Select Energy Services (WTTR) 10-Q 5 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-38066
Entity Registrant Name	SELECT ENERGY SERVICES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-4561945
Entity Address, Address Line One	1233 W. Loop South, Suite 1400
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77027
City Area Code	713
Local Phone Number	235-9500
Title of 12(b) Security	Class A common stock, par value $0.01 per share
Trading Symbol	WTTR
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001693256
Amendment Flag	false
Class A Common Stock
Document and Entity Information
Entity Common Stock, Shares Outstanding		87,856,767
Class B Common Stock
Document and Entity Information
Entity Common Stock, Shares Outstanding		16,221,101

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 160,021	$ 169,039
Accounts receivable trade, net of allowance for credit losses of $8,617 and $9,157, respectively	140,016	129,392
Accounts receivable, related parties	332	69
Inventories	34,410	33,384
Prepaid expenses and other current assets	20,774	19,621
Total current assets	355,553	351,505
Property and equipment	870,091	878,902
Accumulated depreciation	(537,199)	(528,537)
Total property and equipment, net	332,892	350,365
Right-of-use assets, net	49,881	52,331
Other intangible assets, net	113,463	116,079
Other long-term assets, net	6,869	5,079
Total assets	858,658	875,359
Current liabilities
Accounts payable	24,847	12,995
Accrued accounts payable	23,177	21,359
Accounts payable and accrued expenses, related parties	946	519
Accrued salaries and benefits	14,996	16,279
Accrued insurance	9,458	9,788
Sales tax payable	2,488	1,415
Accrued expenses and other current liabilities	13,325	12,077
Current operating lease liabilities	13,968	14,019
Current portion of finance lease obligations	287	307
Total current liabilities	103,492	88,758
Long-term operating lease liabilities	57,834	60,984
Other long-term liabilities	19,383	19,735
Total liabilities	180,709	169,477
Commitments and contingencies (Note 8)
Preferred stock, $0.01 par value; 50,000,000 shares authorized; no shares issued and outstanding as of March 31, 2021 and December 31, 2020
Additional paid-in capital	910,688	909,278
Accumulated deficit	(340,354)	(317,247)
Total stockholders' equity	571,375	593,061
Noncontrolling interests	106,574	112,821
Total equity	677,949	705,882
Total liabilities and equity	858,658	875,359
Class A Common Stock
Current liabilities
Common stock	879	868
Class B Common Stock
Current liabilities
Common stock	$ 162	$ 162

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Allowance for doubtful accounts	$ 8,617	$ 9,157
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	50,000,000	50,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Class A Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	350,000,000	350,000,000
Common Stock, Shares, Issued	87,856,767	86,812,647
Common Stock, Shares, Outstanding	87,856,767	86,812,647
Class A-2 Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	40,000,000	40,000,000
Common Stock, Shares, Issued	0	0
Common Stock, Shares, Outstanding	0	0
Class B Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	150,000,000	150,000,000
Common Stock, Shares, Issued	16,221,101	16,221,101
Common Stock, Shares, Outstanding	16,221,101	16,221,101

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue
Total revenue	$ 143,742	$ 278,285
Costs of revenue
Depreciation and amortization	21,650	26,182
Total costs of revenue	148,139	262,989
Gross (loss) profit	(4,397)	15,296
Operating expenses
Selling, general and administrative	19,894	25,289
Depreciation and amortization	649	685
Impairment of goodwill and trademark		276,016
Impairment and abandonment of property and equipment		3,184
Lease abandonment costs	104	953
Total operating expenses	20,647	306,127
Loss from operations	(25,044)	(290,831)
Other (expense) income
Losses on sales of property and equipment and divestitures, net	(579)	(435)
Interest expense, net	(435)	(331)
Foreign currency gain (loss), net	3	(46)
Other (expense) income, net	(1,629)	259
Loss before income tax benefit	(27,684)	(291,384)
Income tax benefit	263	164
Net loss	(27,421)	(291,220)
Less: net loss attributable to noncontrolling interests	4,314	45,358
Net loss attributable to Select Energy Services, Inc.	(23,107)	(245,862)
Water Services
Revenue
Total revenue	64,223	149,511
Costs of revenue
Costs of revenue	62,324	129,114
Water Infrastructure
Revenue
Total revenue	37,803	57,762
Costs of revenue
Costs of revenue	26,399	47,813
Oilfield Chemicals
Revenue
Total revenue	41,716	71,012
Costs of revenue
Costs of revenue	37,766	59,876
Other.
Costs of revenue
Costs of revenue		4
Class A Common Stock
Other (expense) income
Net loss attributable to Select Energy Services, Inc.	$ (23,107)	$ (245,862)
Net loss per share attributable to common stockholders (Note 14):
Basic	$ (0.27)	$ (2.86)
Diluted	$ (0.27)	$ (2.86)

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net loss	$ (27,421)	$ (291,220)
Other comprehensive income
Comprehensive loss	(27,421)	(291,220)
Less: comprehensive loss attributable to noncontrolling interests	4,314	45,358
Comprehensive loss attributable to Select Energy Services, Inc.	$ (23,107)	$ (245,862)

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Class A Common StockCommon Stock	Class B Common StockCommon Stock	Total Stockholders' Equity	Additional Paid-In Capital	Accumulated (Deficit) Retained Earnings	Noncontrolling Interests.	Total
Beginning balance at Dec. 31, 2019	$ 879	$ 162	$ 937,177	$ 914,699	$ 21,437	$ 175,635	$ 1,112,812
Beginning balance (in shares) at Dec. 31, 2019	87,893,525	16,221,101
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ESPP shares issued			30	30		(3)	27
ESPP shares issued (in shares)	4,443
Equity-based compensation			483	483		91	574
Issuance of restricted shares	$ 13		2,171	2,158		(2,171)
Issuance of restricted shares (in shares)	1,271,706
Exercise of restricted stock units			1	1		(1)
Exercise of restricted stock units (in shares)	625
Repurchase of common stock	$ (10)		(7,239)	(7,229)		603	(6,636)
Repurchase of common stock ( in shares)	(979,391)
Restricted shares forfeited	$ (2)		(340)	(338)		340
Restricted shares forfeited (in shares)	(199,069)
NCI income tax adjustment			8	8		(8)
Net loss			(245,862)		(245,862)	(45,358)	(291,220)
Ending balance at Mar. 31, 2020	$ 880	$ 162	686,429	909,812	(224,425)	129,128	815,557
Ending balance (in shares) at Mar. 31, 2020	87,991,839	16,221,101
Beginning balance at Dec. 31, 2020	$ 868	$ 162	593,061	909,278	(317,247)	112,821	705,882
Beginning balance (in shares) at Dec. 31, 2020	86,812,647	16,221,101
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ESPP shares issued			14	14			14
ESPP shares issued (in shares)	2,145
Equity-based compensation			1,202	1,202		220	1,422
Issuance of restricted shares	$ 15		1,544	1,529		(1,544)
Issuance of restricted shares (in shares)	1,487,448
Repurchase of common stock	$ (1)		(889)	(888)		15	(874)
Repurchase of common stock ( in shares)	(144,078)
Restricted shares forfeited	$ (3)		(318)	(315)		318
Restricted shares forfeited (in shares)	(301,395)
Noncontrolling interest in subsidiary			(140)	(140)		(934)	(1,074)
NCI income tax adjustment			8	8		(8)
Net loss			(23,107)		(23,107)	(4,314)	(27,421)
Ending balance at Mar. 31, 2021	$ 879	$ 162	$ 571,375	$ 910,688	$ (340,354)	$ 106,574	$ 677,949
Ending balance (in shares) at Mar. 31, 2021	87,856,767	16,221,101

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net loss	$ (27,421)	$ (291,220)
Adjustments to reconcile net loss to net cash provided by operating activities
Depreciation and amortization	22,299	26,867
Net loss on disposal of property and equipment and divestitures	579	435
Bad debt expense	300	2,385
Amortization of debt issuance costs	172	172
Inventory write-downs	54	48
Equity-based compensation	1,422	574
Impairment of goodwill and trademark		276,016
Impairment and abandonment of property and equipment		3,184
Unrealized loss on short-term investment	1,831
Other operating items, net	(129)	(47)
Changes in operating assets and liabilities
Accounts receivable	(11,187)	34,992
Prepaid expenses and other assets	(2,696)	6,633
Accounts payable and accrued liabilities	10,903	(13,328)
Net cash (used in) provided by operating activities	(3,873)	46,711
Cash flows from investing activities
Proceeds received from divestitures		85
Purchase of property and equipment	(4,534)	(11,338)
Purchase of equity method investment	(2,000)
Proceeds received from sales of property and equipment	2,316	5,768
Net cash used in investing activities	(4,218)	(5,485)
Cash flows from financing activities
Payments of finance lease obligations	(75)	(65)
Proceeds from share issuance	14	27
Contributions from noncontrolling interests		383
Repurchase of common stock	(874)	(6,636)
Net cash used in financing activities	(935)	(6,291)
Effect of exchange rate changes on cash	8	(61)
Net (decrease) increase in cash and cash equivalents	(9,018)	34,874
Cash and cash equivalents, beginning of period	169,039	79,268
Cash and cash equivalents, end of period	160,021	114,142
Supplemental cash flow disclosure:
Cash paid for interest	367	386
Cash refunds received for income taxes, net	(650)	(156)
Supplemental disclosure of noncash investing activities:
Capital expenditures included in accounts payable and accrued liabilities	$ 6,490	$ 6,184

BUSINESS AND BASIS OF PRESENTAT

BUSINESS AND BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2021
BUSINESS AND BASIS OF PRESENTATION
BUSINESS AND BASIS OF PRESENTATION	NOTE 1—BUSINESS AND BASIS OF PRESENTATION Description of the business : Select Energy Services, Inc. (“we,” “Select Inc.” or “the Company”) was incorporated as a Delaware corporation on November 21, 2016. The Company is a holding company whose sole material asset consists of common units (“SES Holdings LLC Units”) in SES Holdings, LLC (“SES Holdings”). We are a leading provider of comprehensive water-management and chemical solutions to the oil and gas industry in the U.S. We also develop, manufacture and deliver a full suite of chemical solutions for use in oil and gas well completion and production operations. As a leader in the water solutions industry, we place the utmost importance on safe, environmentally responsible management of oilfield water throughout the lifecycle of a well. Additionally, we believe that responsibly managing water resources through our operations to help conserve and protect the environment in the communities in which we operate is paramount to our continued success. Rockwater Merger: On November 1, 2017, the Company completed a merger with Rockwater Energy Solutions, Inc. (the “Rockwater Merger”). Class A and Class B Common Stock: Exchange rights: ​ Basis of presentation : The accompanying unaudited interim consolidated financial statements of the Company have been prepared in accordance with generally accepted accounting principles in the U.S. (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). These unaudited interim consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and, therefore, do not include all disclosures required for financial statements prepared in conformity with GAAP. This Quarterly Report relates to the three months ended March 31, 2021 (the “Current Quarter”) and the three months ended March 31, 2020 (the “Prior Quarter”). The Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (the “2020 Form 10-K”) filed with the SEC on February 24, 2021, includes certain definitions and a summary of significant accounting policies and should be read in conjunction with this Quarterly Report. All material adjustments (consisting solely of normal recurring adjustments) which, in the opinion of management, are necessary for a fair statement of the results for the interim periods have been reflected. The results for the Current Quarter may not be indicative of the results to be expected for the full year, in part due to the COVID-19 pandemic and continued progress in the distribution and uptake of remedies such as vaccines. The unaudited interim consolidated financial statements include the accounts of the Company and all of its majority-owned or controlled subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. For investments in subsidiaries that are not wholly owned, but where the Company exercises control, the equity held by the minority owners and their portion of net income or loss are reflected as noncontrolling interests. Investments in entities in which the Company exercises significant influence over operating and financial policies are accounted for using the equity method, and investments in entities for which the Company does not have significant control or influence are accounted for using the cost method or other appropriate basis as applicable. As of March 31, 2021, the Company had one equity method investee and one cost-method investee. The Company also had one investment in notes receivable accounted for using the amortized cost basis and one investment in publicly-traded securities accounted for using the fair value option. The Company’s investments are reviewed for impairment whenever events or circumstances indicate that the carrying value may not be recoverable. When circumstances indicate that the fair value of its investment is less than its carrying value and the reduction in value is other than temporary, the reduction in value is recognized in earnings. Our investments in unconsolidated entities are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) Type of Investment Year attained Accounting method Balance Sheet Location March 31, 2021 ​ December 31, 2020 20% minority interest 2011 Cost-method Other long-term assets, net $ 300 ​ $ 300 Notes receivable 2020 Amortized cost basis Other long-term assets, net ​ 3,096 ​ ​ 3,037 33% minority interest 2021 Equity-method Other long-term assets, net ​ 2,000 ​ ​ — Publicly traded securities 2020 Fair value option Prepaid expenses and other current assets ​ 1,546 ​ ​ 3,377 ​ Segment reporting : The Company has three reportable segments. Reportable segments are defined as components of an enterprise for which separate financial information is evaluated regularly by the chief operating decision maker (“CODM”) in deciding how to allocate resources and assess performance. The Company’s current reportable segments are Water Services, Water Infrastructure, and Oilfield Chemicals. The Water Services segment consists of the Company’s services businesses, including water transfer, flowback and well testing, fluids hauling, water containment and water network automation, primarily serving E&P companies. Additionally, this segment includes the operations of our accommodations and rentals business as well as the Company’s industrial solutions business. The Water Infrastructure segment consists of the Company’s infrastructure assets, including operations associated with our water sourcing and pipeline infrastructure, our water recycling solutions and infrastructure, and our produced water gathering systems and saltwater disposal wells, primarily serving E&P companies. The Oilfield Chemicals segment provides technical solutions and expertise related to chemical applications in the oil and gas industry. We also have significant capabilities in supplying logistics for chemical applications. We develop, manufacture and provide a full suite of chemicals used in hydraulic fracturing, stimulation, cementing, production, pipelines and well completions. With our broad chemicals product line, combined with our expertise in oilfield chemicals application, we serve pressure pumpers and major integrated and independent U.S. and international oil and gas producers. We further utilize our chemicals experience and lab testing capabilities to customize water treatment solutions tailored to the customer’s water quality and other fluid system design objectives.

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2021
SIGNIFICANT ACCOUNTING POLICIES
SIGNIFICANT ACCOUNTING POLICIES	NOTE 2—SIGNIFICANT ACCOUNTING POLICIES Significant accounting policies : The Company’s significant accounting policies are disclosed in Note 2 of the consolidated financial statements for the year ended December 31, 2020, included in the 2020 Form 10-K. Use of estimates : The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the recoverability of long-lived assets and intangibles, useful lives used in depreciation and amortization, uncollectible accounts receivable, inventory reserve, income taxes, self-insurance liabilities, share-based compensation, contingent liabilities and the incremental borrowing rate for leases. The Company bases its estimates on historical and other pertinent information that are believed to be reasonable under the circumstances. The accounting estimates used in the preparation of the consolidated financial statements may change as new events occur, as more experience is acquired, as additional information is obtained and as the Company’s operating environment changes. Allowance for credit losses: ​ The change in the allowance for credit losses is as follows: ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ ​ (in thousands) Balance at December 31, 2020 ​ $ 9,157 Increase to allowance based on a percent of revenue ​ 290 Charge-offs ​ ​ (830) Balance at March 31, 2021 ​ $ 8,617 ​ The Company also has a $3.1 million note receivable resulting from an investment in the fourth quarter of 2020, with no allowance for credit losses as of March 31, 2021. See Note 11 – Related Party Transactions for additional information. ​ Asset retirement obligations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ (in thousands) Balance at December 31, 2020 $ 999 Accretion expense, included in depreciation and amortization expense ​ 13 Payments ​ ​ (121) Balance at March 31, 2021 $ 891 ​ We review the adequacy of our ARO liabilities whenever indicators suggest that the estimated cash flows underlying the liabilities have changed. The Company’s ARO liabilities are included in accrued expenses and other current liabilities and other long-term liabilities in the accompanying consolidated balance sheets. Lessor Income: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) Category Classification ​ ​ ​ ​ ​ ​ Lessor income Costs of revenue ​ $ 66 ​ $ 116 Sublease income Lease abandonment costs and Costs of revenue ​ ​ 243 ​ ​ 401 ​ The Company also generates short-term equipment rental revenue. See Note 3—Revenue for a discussion of revenue recognition for the accommodations and rentals business. ​ Defined Contribution Plan: ​ Payroll Tax Deferral:

REVENUE

REVENUE	3 Months Ended
	Mar. 31, 2021
REVENUE
REVENUE	NOTE 3—REVENUE ​ The Company follows ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Leases, The following factors are applicable to all three of the Company’s segments for the first three months of 2021 and 2020, respectively: ● The vast majority of customer agreements are short-term, lasting less than one year. ● Contracts are seldom combined together as virtually all of our customer agreements constitute separate performance obligations. Each job is typically distinct, thereby not interdependent or interrelated with other customer agreements. ● Most contracts allow either party to terminate at any time without substantive penalties. If the customer terminates the contract, the Company is unconditionally entitled to the payments for the services rendered and products delivered to date. ● Contract terminations before the end of the agreement are rare. ● Sales returns are rare and no sales return assets have been recognized on the balance sheet. ● There are minimal volume discounts. ● There are no service-type warranties. ● There is no long-term customer financing. In the Water Services and Water Infrastructure segments, performance obligations arise in connection with services provided to customers in accordance with contractual terms, in an amount the Company expects to collect. Services are generally sold based upon customer orders or contracts with customers that include fixed or determinable prices. Revenues are generated by services rendered and measured based on output generated, which is usually simultaneously received and consumed by customers at their job sites. As a multi-job site organization, contract terms, including pricing for the Company’s services, are negotiated on a job site level on a per-job basis. Most jobs are completed in a short period of time, usually between one day and one month. Revenue is recognized as performance obligations are completed on a daily, hourly or per unit basis with unconditional rights to consideration for services rendered reflected as accounts receivable trade, net of allowance for credit losses. In cases where a prepayment is received before the Company satisfies its performance obligations, a contract liability is recorded in accrued expenses and other current liabilities. Final billings generally occur once all of the proper approvals are obtained. No revenue is associated with mobilization or demobilization of personnel and equipment. Rather, mobilization and demobilization are factored into pricing for services. Billings and costs related to mobilization and demobilization is not material for customer agreements that start in one period and end in another. As of March 31, 2021, the Company had six contracts in place for these segments lasting over one year. The Company has recorded an $8.2 million contract liability associated with one of the six long-term contracts as of March 31, 2021, recognized in other long-term liabilities in the accompanying balance sheets. The Company expects this contract liability to be converted to revenue under the terms of the contract as it is earned. In the Oilfield Chemicals segment, the typical performance obligation is to provide a specific quantity of chemicals to customers in accordance with the customer agreement in an amount the Company expects to collect. Products and services are generally sold based upon customer orders or contracts with customers that include fixed or determinable prices. Revenue is recognized as the customer takes title to chemical products in accordance with the agreement. Products may be provided to customers in packaging or delivered to the customers’ containers through a hose. In some cases, the customer takes title to the chemicals upon consumption from storage containers on their property, where the chemicals are considered inventory until customer usage. In cases where the Company delivers products and recognizes revenue before collecting payment, the Company usually has an unconditional right to payment reflected in accounts receivable trade, net of allowance for credit losses. Customer returns are rare and immaterial and there were no material in-process customer agreements for this segment as of March 31, 2021, lasting greater than one year. The Company accounts for accommodations and rentals agreements as an operating lease. The Company recognizes revenue from renting equipment on a straight-line basis. Accommodations and rental contract periods are generally daily, weekly or monthly. The average lease term is less than three months and as of March 31, 2021, there were no material rental agreements in effect lasting more than one year. During the Current Quarter and Prior Quarter, approximately $6.2 million and $15.2 million of accommodations and rentals revenue was accounted for under ASC 842 lease guidance, with the remainder accounted for under ASC 606 revenue guidance. The following table sets forth certain financial information with respect to the Company’s disaggregation of revenues by geographic location: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Geographic Region ​ ​ ​ ​ ​ ​ ​ Permian Basin ​ $ 71,204 ​ $ 137,998 ​ Eagle Ford ​ ​ 20,785 ​ ​ 35,664 ​ Haynesville/E. Texas ​ ​ 17,265 ​ ​ 19,015 ​ Marcellus/Utica ​ ​ 11,667 ​ ​ 19,839 ​ Rockies ​ ​ 10,022 ​ ​ 18,869 ​ MidCon ​ ​ 8,476 ​ ​ 24,873 ​ Bakken ​ ​ 6,903 ​ ​ 22,560 ​ Eliminations and other regions ​ ​ (2,580) ​ ​ (533) ​ Total ​ $ 143,742 ​ $ 278,285 ​ ​ In the Water Services segment, the top three revenue-producing regions are the Permian Basin, Eagle Ford and Marcellus/Utica, which collectively comprised 77%

INVENTORIES

INVENTORIES	3 Months Ended
	Mar. 31, 2021
INVENTORIES
INVENTORIES	NOTE 4—INVENTORIES Inventories, which are comprised of chemicals and materials available for resale and parts and consumables used in operations, are valued at the lower of cost and net realizable value, with cost determined under the weighted-average method. The significant components of inventory are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ (in thousands) Raw materials ​ $ 18,869 ​ $ 16,701 Finished goods ​ 15,541 ​ 16,683 Total ​ $ 34,410 ​ $ 33,384 ​ During the Current Quarter and Prior Quarter, the Company recorded charges to the reserve for excess and obsolete inventory for immaterial amounts of $0.1 million or less, respectively, which were recognized within costs of revenue on the accompanying consolidated statements of operations. The Company’s inventory reserve was $4.1 million as of March 31, 2021 and December 31, 2020. The reserve for excess and obsolete inventories is determined based on the Company’s historical usage of inventory on hand, as well as future expectations and the amount necessary to reduce the cost of the inventory to its estimated net realizable value.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	3 Months Ended
	Mar. 31, 2021
PROPERTY AND EQUIPMENT..
PROPERTY AND EQUIPMENT	NOTE 5—PROPERTY AND EQUIPMENT Property and equipment are stated at cost less accumulated depreciation. Depreciation (and amortization of finance lease assets) is calculated on a straight-line basis over the estimated useful life of each asset. Property and equipment consists of the following as of March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ (in thousands) Machinery and equipment ​ $ 591,362 ​ $ 596,441 Buildings and leasehold improvements ​ 92,669 ​ 93,236 Pipelines ​ ​ 72,624 ​ ​ 72,458 Disposal wells ​ 47,571 ​ 48,097 Vehicles and equipment ​ 29,839 ​ 30,975 Land ​ ​ 12,803 ​ ​ 13,497 Computer equipment and software ​ ​ 6,790 ​ ​ 7,127 Office furniture and equipment ​ 888 ​ 892 Machinery and equipment - finance lease ​ 537 ​ 537 Vehicles and equipment - finance lease ​ 463 ​ 475 Computer equipment and software - finance lease ​ 356 ​ 356 Construction in progress ​ 14,189 ​ 14,811 ​ ​ 870,091 ​ 878,902 Less accumulated depreciation (1) ​ (537,199) ​ (528,537) Total property and equipment, net ​ $ 332,892 ​ $ 350,365 (1) Includes $1.1 million of accumulated depreciation related to finance leases as of March 31, 2021 and December 31, 2020. Total depreciation and amortization expense related to property and equipment and finance leases presented in the table above, as well as amortization of intangible assets presented in Note 6 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Category ​ ​ ​ ​ ​ ​ ​ Depreciation expense from property and equipment ​ $ 19,587 ​ $ 23,985 ​ Amortization expense from finance leases ​ ​ 82 ​ ​ 77 ​ Amortization expense from intangible assets ​ ​ 2,617 ​ ​ 2,993 ​ Accretion expense from asset retirement obligations ​ ​ 13 ​ ​ (188) ​ Total depreciation and amortization ​ $ 22,299 ​ $ 26,867 ​ ​ Long-lived assets are evaluated for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. During the Prior Quarter, the Company determined that certain equipment was obsolete, and recorded a $3.2 million impairment of property and equipment. ​

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2021
GOODWILL AND OTHER INTANGIBLE ASSETS.
GOODWILL AND OTHER INTANGIBLE ASSETS	NOTE 6—GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill is evaluated for impairment on at least an annual basis, or more frequently if indicators of impairment exist. The annual impairment tests are based on Level 3 inputs (see Note 10 – Fair Value Measurement). During the first quarter of 2020, the Company had triggering events related to the significant adverse change to the demand for the Company’s services in connection with a significant decline in the price of oil and the related global economic impacts resulting from the OPEC+ disputes as well as the COVID-19 pandemic. This included uncertainty regarding oil prices and the length of the recovery following the significant market disruption in the oil and gas industry. Given the volatile market environment at March 31, 2020, the Company utilized third-party valuation advisors to assist with these evaluations. These evaluations included significant judgment, including management’s short-term and long-term forecast of operating performance, discount rates based on our weighted-average cost of capital, revenue growth rates, profitability margins, capital expenditures, the timing of future cash flows based on an eventual recovery of the oil and gas industry, and in the case of long-lived assets, the remaining useful life and service potential of the asset. The Company performed quantitative tests for reporting units in both the Water Services and Water Infrastructure segments using the income and market approaches, resulting in a full impairment to goodwill in both segments totaling $266.9 million. The components of other intangible assets, net as of March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, 2021 ​ As of December 31, 2020 ​ Gross Accumulated Net Gross ​ ​ Accumulated Net ​ ​ Value ​ Amortization ​ Value ​ Value ​ Impairment ​ Amortization ​ Value ​ ​ (in thousands) ​ (in thousands) Definite-lived ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships ​ $ 116,554 ​ $ (31,568) ​ $ 84,986 ​ $ 116,554 ​ $ — ​ $ (29,302) ​ $ 87,252 Patents ​ ​ 9,741 ​ ​ (3,410) ​ ​ 6,331 ​ ​ 9,741 ​ ​ — ​ ​ (3,166) ​ ​ 6,575 Other ​ ​ 7,234 ​ ​ (6,479) ​ ​ 755 ​ 7,234 ​ ​ — ​ (6,373) ​ 861 Total definite-lived ​ ​ 133,529 ​ ​ (41,457) ​ ​ 92,072 ​ ​ 133,529 ​ ​ — ​ ​ (38,841) ​ ​ 94,688 Indefinite-lived ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Water rights ​ ​ 7,031 ​ ​ — ​ ​ 7,031 ​ ​ 7,031 ​ ​ — ​ ​ — ​ ​ 7,031 Trademarks ​ ​ 14,360 ​ ​ — ​ ​ 14,360 ​ ​ 23,442 ​ ​ (9,082) ​ ​ — ​ ​ 14,360 Total indefinite-lived ​ ​ 21,391 ​ ​ — ​ ​ 21,391 ​ ​ 30,473 ​ ​ (9,082) ​ ​ — ​ ​ 21,391 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other intangible assets, net ​ $ 154,920 ​ $ (41,457) ​ $ 113,463 ​ $ 164,002 ​ $ (9,082) ​ $ (38,841) ​ $ 116,079 ​ Due to the triggering events discussed above, the Company also tested indefinite-lived intangible assets for impairment during the first quarter of 2020. These evaluations included significant judgment, including discount rates based on our weighted-average cost of capital and the royalty rate. This resulted in $9.1 million of impairment to trademarks using the relief from royalty method, which was recorded in the Oilfield Chemicals segment. Further, the Company tested all other long-lived assets for impairment, including definite-lived intangible assets, using an undiscounted test for recoverability at the asset group level which resulted in no additional impairments. The weighted-average amortization period for customer relationships, patents, and other definite-lived assets was 9.4 years, 6.5 years, and 2.5 five ​ ​ ​ ​ ​ ​ ​ Amount ​ ​ ​ (in thousands) ​ Remainder of 2021 ​ $ 7,850 ​ Year ending December 31, 2022 ​ 10,252 ​ Year ending December 31, 2023 ​ 10,180 ​ Year ending December 31, 2024 ​ 10,111 ​ Year ending December 31, 2025 ​ 9,948 ​ Thereafter ​ ​ 43,731 ​ Total ​ $ 92,072 ​ ​

DEBT

DEBT	3 Months Ended
	Mar. 31, 2021
DEBT
DEBT	NOTE 7—DEBT Credit facility and revolving line of credit On November 1, 2017, SES Holdings and Select Energy Services, LLC (“Select LLC”) entered into a $300.0 million senior secured revolving credit facility (the “Credit Agreement”), by and among SES Holdings, as parent, Select LLC, as borrower and certain of SES Holdings’ subsidiaries, as guarantors, each of the lenders party thereto and Wells Fargo Bank, N.A., as administrative agent, issuing lender and swingline lender (the “Administrative Agent”). The Credit Agreement also has a sublimit of $40.0 million for letters of credit and a sublimit of $30.0 million for swingline loans. The maturity date of the Credit Agreement is the earlier of (a) November 1, 2022, and (b) the earlier termination in whole of the Commitments pursuant to Section 2.1(b) of Article VII of the Credit Agreement. The Credit Agreement permits extensions of credit up to the lesser of $300.0 million and a borrowing base that is determined by calculating the amount equal to the sum of (i) 85% of the Eligible Billed Receivables (as defined in the Credit Agreement), plus (ii) 75% of Eligible Unbilled Receivables (as defined in the Credit Agreement), provided that this amount will not equal more than 35% of the borrowing base, plus (iii) the lesser of (A) the product of 70% multiplied by the value of Eligible Inventory (as defined in the Credit Agreement) at such time and (B) the product of 85% multiplied by the Net Recovery Percentage (as defined in the Credit Agreement) identified in the most recent Acceptable Appraisal of Inventory (as defined in the Credit Agreement), multiplied by the value of Eligible Inventory at such time, provided that this amount will not equal more than 30% of the borrowing base, minus (iv) the aggregate amount of Reserves (as defined in the Credit Agreement), if any, established by the Administrative Agent from time to time, including, if any, the amount of the Dilution Reserve (as defined in the Credit Agreement). The borrowing base is calculated on a monthly basis pursuant to a borrowing base certificate delivered by Select LLC to the Administrative Agent. Borrowings under the Credit Agreement bear interest, at Select LLC’s election, at either the (a) one-, two-, three- or six-month LIBOR (“Eurocurrency Rate”) or (b) the greatest of (i) the federal funds rate plus 0.5%, (ii) the one-month Eurocurrency Rate plus 1% and (iii) the Administrative Agent’s prime rate (the ”Base Rate”), in each case plus an applicable margin. Interest is payable monthly in arrears. The applicable margin for Eurocurrency Rate loans ranges from 1.50% to 2.00% and the applicable margin for Base Rate loans ranges from 0.50% to 1.00%, in each case, depending on Select LLC’s average excess availability under the Credit Agreement. During the continuance of a bankruptcy event of default, automatically and during the continuance of any other default, upon the Administrative Agent’s or the required lenders’ election, all outstanding amounts under the Credit Agreement will bear interest at 2.00% plus the otherwise applicable interest rate. ​ ​ ​ ​ ​ ​ ​ ​ Level ​ Average Excess Availability ​ Base Rate Margin ​ Eurocurrency Rate Margin ​ ​ ​ ​ ​ ​ ​ I ​ < 33% of the commitments ​ 1.00% ​ 2.00% II ​ < 66.67% of the commitments and ≥ 33.33% of the commitments ​ 0.75% ​ 1.75% III ​ ≥ 66.67% of the commitments ​ 0.50% ​ 1.50% ​ ​ ​ ​ ​ ​ Level ​ Average Revolver Usage ​ Unused Line Fee Percentage ​ ​ ​ ​ ​ I ​ ≥ 50% of the commitments ​ 0.250% II ​ < 50% of the commitments ​ 0.375% ​ The obligations under the Credit Agreement are guaranteed by SES Holdings and certain subsidiaries of SES Holdings and Select LLC and secured by a security interest in substantially all of the personal property assets of SES Holdings, Select LLC and their domestic subsidiaries. The Credit Agreement contains certain customary representations and warranties, affirmative and negative covenants and events of default. If an event of default occurs and is continuing, the lenders may declare all amounts outstanding under the Credit Agreement to be immediately due and payable. In addition, the Credit Agreement restricts SES Holdings’ and Select LLC’s ability to make distributions on, or redeem or repurchase, its equity interests, except for certain distributions, including distributions of cash so long as, both at the time of the distribution and after giving effect to the distribution, no default exists under the Credit Agreement and either (a) excess availability at all times during the preceding 30 consecutive days, on a pro forma basis and after giving effect to such distribution, is not less than the greater of (1) 25% of the lesser of (A) the maximum revolver amount and (B) the then-effective borrowing base and (2) $37.5 million or (b) if SES Holdings’ fixed charge coverage ratio is at least 1.0 to 1.0 on a pro forma basis, and excess availability at all times during the preceding 30 consecutive days, on a pro forma basis and after giving effect to such distribution, is not less than the greater of (1) 20% of the lesser of (A) the maximum revolver amount and (B) the then-effective borrowing base and (2) $30.0 million. Additionally, the Credit Agreement generally permits Select LLC to make distributions to allow Select Inc. to make payments required under the existing Tax Receivable Agreements. See “Note 11—Related-Party Transactions” for further discussion of the Tax Receivable Agreements. The Credit Agreement also requires SES Holdings to maintain a fixed charge coverage ratio of at least 1.0 to 1.0 at any time availability under the Credit Agreement is less than the greater of (i) 10% of the lesser of (A) the maximum revolver amount and (B) the then-effective borrowing base and (ii) $15.0 million and continuing through and including the first day after such time that availability under the Credit Agreement has equaled or exceeded the greater of (i) 10% of the lesser of (A) the maximum revolver amount and (B) the then-effective borrowing base and (ii) $15.0 million for 60 consecutive calendar days. Certain lenders party to the Credit Agreement and their respective affiliates have from time to time performed, and may in the future perform, various financial advisory, commercial banking and investment banking services for the Company and its affiliates in the ordinary course of business for which they have received and would receive customary compensation. In addition, in the ordinary course of their various business activities, such parties and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investments and securities activities may involve the Company’s securities and/or instruments. The Company had no borrowings outstanding under the Credit Agreement as of March 31, 2021 and December 31, 2020. As of March 31, 2021 and December 31, 2020, the borrowing base under the Credit Agreement was $117.8 million and $96.4 million, respectively. Debt issuance costs are amortized to interest expense over the life of the debt to which they pertain. Total unamortized debt issuance costs as of March 31, 2021 and December 31, 2020, were $1.1 million and $1.3 million, respectively. As these debt issuance costs relate to a revolving line of credit, they are presented as a deferred charge within other assets on the consolidated balance sheets. Amortization expense related to debt issuance costs was $0.2 million for both the Current Quarter and Prior Quarter. The Company was in compliance with all debt covenants as of March 31, 2021.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2021
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	NOTE 8—COMMITMENTS AND CONTINGENCIES Litigation The Company is subject to a number of lawsuits and claims arising out of the normal conduct of its business. The ability to predict the ultimate outcome of such matters involves judgments, estimates and inherent uncertainties. Based on a consideration of all relevant facts and circumstances, including applicable insurance coverage, it is not expected that the ultimate outcome of any currently pending lawsuits or claims against the Company will have a material adverse effect on its consolidated financial position, results of operations or cash flows; however, there can be no assurance as to the ultimate outcome of these matters. As previously disclosed, certain subsidiaries acquired in the Rockwater Merger are under investigation by the U.S. Attorney's Office for the Middle District of Pennsylvania and the U.S. Environmental Protection Agency (“EPA”). It is alleged that certain employees at some of the facilities altered emissions controls systems on less than 5% of the vehicles in the fleet in violation of the Clean Air Act. The Company is continuing to cooperate with the relevant authorities to resolve the matter, and while at this time no administrative, civil or criminal charges have been brought against the Company, the Company accrued $4.3 million related to the settlement of this investigation and made payments of $1.7 million related to this accrual during 2020. The Company does not believe that the ultimate resolution of this matter will be material to the Company’s financial statements. In February 2021, the Company, and certain subsidiaries, received Notices of Proposed Debarment (“Notices”) from the EPA’s Suspension and Debarment Official (“SDO”). The Notices propose a debarment from participation in future federal contracts, non-procurement covered transactions such as grants, and other assistance activities, and would render the Company ineligible to receive any federal contracts or approved subcontracts in excess of $35,000 or to act as an agent or representative on behalf of another in such transaction, or receive certain federal benefits. Please see Item 1A – Risk Factors in this Form 10-Q. Self-Insured Reserves We are self-insured up to certain retention limits with respect to workers’ compensation, general liability and vehicle liability matters and health insurance. We maintain accruals for self-insurance retentions that we estimate using third-party data and claims history.

EQUITY-BASED COMPENSATION

EQUITY-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2021
EQUITY-BASED COMPENSATION
EQUITY-BASED COMPENSATION	NOTE 9—EQUITY-BASED COMPENSATION The SES Holdings 2011 Equity Incentive Plan, (“2011 Plan”) was approved by the board of managers of SES Holdings in April 2011. In conjunction with the private placement of 16,100,000 shares of the Company’s Class A Common Stock on December 20, 2016 (the “Select 144A Offering”), the Company adopted the Select Energy Services, Inc. 2016 Equity Incentive Plan (as amended, the “2016 Plan”) for employees, consultants and directors of the Company and its affiliates. Options that were outstanding under the 2011 Plan immediately prior to the Select 144A Offering were cancelled in exchange for new options granted under the 2016 Plan. On May 8, 2020, the Company’s stockholders approved an amendment to the 2016 Plan to increase the number of shares of the Company’s Class A common stock that may be issued under the 2016 Plan by 4,000,000 shares and to make certain other administrative changes. The 2016 Plan includes share recycling provisions that allow shares subject to an award that expires or is cancelled, forfeited or otherwise terminated without actual delivery of the underlying shares of Class A common stock to be considered not delivered and thus available to be granted as new awards under the 2016 Plan. Currently, the maximum number of shares reserved for issuance under the 2016 Plan is approximately 13.3 million shares, with approximately 3.4 million shares available to be issued as of March 31, 2021. For all share-based compensation award types, the Company accounts for forfeitures as they occur. Stock option awards Stock options were granted with an exercise price equal to or greater than the fair market value of a share of Class A Common Stock as of the date of grant. The Company utilized the Monte Carlo option pricing model to determine fair value of the options granted during 2018, which incorporates assumptions to value equity-based awards. The risk-free interest rate is based on the U.S. Treasury yield curve in effect for the expected term of the option at the time of grant. The expected life of the options was based on the vesting period and term of the options awarded, which is ten years. A summary of the Company’s stock option activity and related information as of and for the Current Quarter is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2021 ​ ​ ​ ​ ​ ​ ​ Weighted-average ​ ​ ​ ​ ​ ​ ​ Weighted-average ​ Grant Date Value ​ Aggregate Intrinsic ​ Stock Options Exercise Price Term (Years) Value (in thousands) (a) Beginning balance, outstanding 3,519,159 ​ $ 16.11 ​ 3.3 ​ $ — Expired ​ (1,246,718) ​ ​ 14.28 ​ ​ ​ ​ ​ Ending balance, outstanding 2,272,441 ​ $ 17.11 ​ 4.8 ​ $ — Ending balance, exercisable ​ 2,272,441 ​ $ 17.11 ​ 4.8 ​ $ — Nonvested at March 31, 2021 ​ — ​ $ — ​ ​ ​ ​ ​ ​ (a) The Company recognized a nominal amount and $0.2 million of compensation expense related to stock options during the Current Quarter and Prior Quarter, respectively. As of March 31, 2021, all equity-based compensation expense related to stock options had been recognized. Restricted Stock Awards The value of the restricted stock awards granted was established by the market price of the Class A Common Stock on the date of grant and is recorded as compensation expense ratably over the vesting term, which is generally one $1.9 million related to the restricted stock awards for the Current Quarter and Prior Quarter, respectively. As of March 31, 2021, there was $13.6 million of unrecognized compensation expense with a weighted-average remaining life of 2.4 years related to unvested restricted stock awards. A summary of the Company’s restricted stock awards activity and related information for the Current Quarter is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2021 ​ ​ ​ ​ Weighted-average ​ Restricted Stock Awards Grant Date Fair Value Nonvested at December 31, 2020 ​ 2,003,072 ​ $ 6.97 Granted ​ 1,487,448 ​ ​ 6.31 Vested ​ (484,816) ​ ​ 8.71 Forfeited ​ (301,395) ​ ​ 6.38 Nonvested at March 31, 2021 ​ 2,704,309 ​ $ 6.36 ​ Performance Share Units (PSUs) During 2018 and 2019, the Company approved grants of performance share units (“PSUs”) that are subject to both performance-based and service-based vesting provisions. The number of shares of Class A Common Stock issued to a recipient upon vesting of the PSU will be calculated based on performance against certain metrics that relate to the Company’s return on asset performance over the January 1, 2018 through December 31, 2020, and January 1, 2019 through December 31, 2021 performance periods, respectively. The target number of shares of Class A Common Stock subject to each PSU granted in 2018 and 2019 is one; however, based on the achievement of performance criteria, the number of shares of Class A Common Stock that may be received in settlement of each PSU can range from zero to 1.75 times the target number. The PSUs become earned at the end of the performance period after the attainment of the performance level has been certified by the compensation committee, which will be no later than June 30, 2021 for the 2018 PSU grants, and June 30, 2022 for the 2019 PSU grants, assuming the minimum performance metrics are achieved. The target PSUs that become earned PSUs during the performance period will be determined in accordance with the following table: ​ ​ ​ ​ Return on Assets at Performance Period End Date ​ Percentage of Target PSUs Earned Less than 9.6% ​ 0% 9.6% ​ 50% 12% ​ 100% 14.4% ​ 175% ​ All PSUs granted in 2018 did not achieve the performance-based vesting conditions and were forfeited. Also, during 2020, the Company revised the estimates for the PSUs granted in 2019, which are not expected to achieve the performance-based vesting conditions. During 2020 and 2021, the Company approved grants of PSUs that are subject to both performance-based and service-based vesting provisions related to (i) return on asset performance (“ROA”) in comparison to thirteen peer companies and (ii) Adjusted Free Cash Flow (“FCF”) performance percentage. The number of shares of Class A Common Stock issued to a recipient upon vesting of the PSUs will be calculated based on ROA and FCF performance over the applicable period from either January 1, 2020 through December 31, 2022 or January 1, 2021 through December 31, 2023. The target number of shares of Class A Common Stock subject to each PSU granted in 2020 and 2021 is one; however, based on the achievement of performance criteria, the number of shares of Class A Common Stock that may be received in settlement of each PSU can range from zero committee, which will be no later than June 30, 2023 for the 2020 PSU grants and June 30, 2024 for the 2021 PSU grants, assuming the applicable minimum performance metrics are achieved. The target PSUs granted in 2020 that become earned connected with the ROA in comparison to other companies will be determined based on the Company’s Average Return on Assets (as defined in the applicable PSU agreement) relative to the Average Return on Assets of the peer companies (as defined in the applicable PSU agreement) in accordance with the following table, but only if the Company’s Average Return on Assets is equal to or greater than 5% during the performance period. The target PSUs granted in 2021 removed the 5% minimum ROA for the Company and added that the Company must have a positive Total Shareholder Return (as defined in the applicable PSU agreement) over the performance period. As a result of this market condition being added, the 2021 PSUs will be valued each reporting period utilizing a Black-Scholes model. ​ ​ ​ ​ Ranking Among Peer Group ​ Percentage of Target Amount Earned Outside of Top 10 ​ 0% Top 10 ​ 50% Top 7 ​ 100% Top 3 ​ 175% ​ The target PSUs that become earned in connection with the adjusted FCF performance percentage will be determined (as defined in the applicable PSU agreement) in accordance with the following table: ​ ​ ​ ​ Adjusted FCF Performance Percentage ​ Percentage of Target Amount Earned Less than 70% ​ 0% 70% ​ 50% 100% ​ 100% 130% ​ 175% ​ The fair value on the date the PSUs were granted during 2021, 2020, and 2019 was $4.2 million, $4.4 million, $7.0 million, respectively. Compensation expense related to the PSUs is determined by multiplying the number of shares of Class A Common Stock underlying such awards that, based on the Company’s estimate, are probable to vest by the measurement-date (i.e., the last day of each reporting period date) fair value and recognized using the accelerated attribution method. The Company recognized compensation expense of $0.4 million and a credit to compensation expense of $1.4 million related to the PSUs for the Current Quarter and Prior Quarter, respectively. As of March 31, 2021, the unrecognized compensation cost related to our unvested PSUs is estimated to be $ million and is expected to be recognized over a weighted-average period of 2.3 years. However, this compensation cost will be adjusted as appropriate throughout the applicable performance periods. The following table summarizes the information about the performance share units outstanding as of March 31, 2021: ​ ​ ​ ​ ​ Performance Share Units Nonvested as of December 31, 2020 ​ 1,763,909 Target shares granted ​ 613,842 Target shares forfeited ​ (242,087) Target shares outstanding as of March 31, 2021 ​ 2,135,664 ​ Employee Stock Purchase Plan (ESPP) The Company has an Employee Stock Purchase Plan (“ESPP”) under which employees that have been continuously employed for at least one year may purchase shares of Class A Common Stock at a discount. The plan provides for four through August 31 and September 1 through November 30. At the end of each offering period, enrolled employees purchase shares of Class A Common Stock at a price equal to 95% of the market value of the stock on the last day of such offering period. The purchases are made at the end of an offering period with funds accumulated through payroll deductions over the course of the offering period. Subject to limitations set forth in the plan and under IRS regulations, eligible employees may elect to contribute a maximum of $15,000 to the plan in a single calendar year. The plan is deemed to be noncompensatory. The following table summarizes ESPP activity (in thousands, except shares): ​ ​ ​ ​ ​ ​ For the three months ended ​ March 31, 2021 Cash received for shares issued ​ $ 14 Shares issued ​ ​ 2,145 ​ Share Repurchases During the Current Quarter, the Company repurchased 144,078 shares of Class A Common Stock in connection with employee minimum tax withholding requirements for units vested under the 2016 Plan. All repurchased shares were retired. During the Current Quarter, the repurchases were accounted for as a decrease to paid-in-capital of $0.9 million and a decrease to Class A Common Stock of approximately $1,400. In the Prior Quarter, the Company repurchased 849,711 shares in the open market and repurchased 129,680 shares in connection with employee minimum tax withholding requirements.

FAIR VALUE MEASUREMENT

FAIR VALUE MEASUREMENT	3 Months Ended
	Mar. 31, 2021
FAIR VALUE MEASUREMENT
FAIR VALUE MEASUREMENT	NOTE 10—FAIR VALUE MEASUREMENT The Company utilizes fair value measurements to measure assets and liabilities in a business combination or assess impairment and abandonment of property and equipment, intangible assets and goodwill. Fair value is defined as the amount at which an asset (or liability) could be bought (or incurred) or sold (or settled) in an orderly transaction between market participants at the measurement date. Further, ASC 820, Fair Value Measurements ASC 820 establishes a three-level valuation hierarchy for disclosure of fair value measurements. The valuation hierarchy categorizes assets and liabilities measured at fair value into one of three different levels depending on the observability of the inputs employed in the measurement. The three levels are defined as follows: Level 1 Level 2 Level 3 A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and considers factors specific to the asset or liability. There were no transfers into, or out of, the three levels of the fair value hierarchy for the three months ended March 31, 2021 or the year ended December 31, 2020. The following table presents information about the Company’s assets measured at fair value on a recurring and non-recurring basis as of March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Measurements Using ​ Carrying ​ ​ ​ ​ ​ Frequency ​ Measurement Date Level 1 Level 2 Level 3 Value (1) Impairment ​ ​ ​ ​ ​ ​ (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarter Ended March 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investments ​ Recurring ​ March 31 ​ ​ 1,546 ​ ​ — ​ ​ — ​ ​ 1,546 ​ ​ — (1) Amount represents carrying value at the date of assessment. Other fair value considerations The carrying values of the Company’s current financial instruments, which include cash and cash equivalents, accounts receivable trade and accounts payable, approximate their fair value as of March 31, 2021 and December 31, 2020, due to the short-term maturity of these instruments. The Company did not have any bank debt as of March 31, 2021 or December 31, 2020. The estimated fair values of the Company’s financial instruments are not necessarily indicative of the amounts that would be realized in a current market exchange. ​ Nonmonetary transaction chose the fair value option because it represents the period-end value of the securities, which the Company has the ability to sell. The Company recorded a $1.8

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2021
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS	NOTE 11—RELATED-PARTY TRANSACTIONS The Company considers its related parties to be those stockholders who are beneficial owners of more than 5.0% of its common stock, executive officers, members of its board of directors or immediate family members of any of the foregoing persons, an investment in a company that is significantly influenced by a related party, and cost-method and equity-method investees. The Company has entered into a number of transactions with related parties. In accordance with the Company’s related persons transactions policy, the audit committee of the Company’s board of directors regularly reviews these transactions. However, the Company’s results of operations may have been different if these transactions were conducted with non-related parties. During the Current Quarter, sales to related parties were $0.3 million and purchases from related-party vendors were $1.1 million. These purchases consisted of $0.9 million relating to the rental of certain equipment or other services used in operations and $0.2 million relating to management, consulting and other services. During the Prior Quarter, sales to related parties were $2.4 million and purchases from related-party vendors were $4.2 million. These purchases consisted of $3.7 million relating to the rental of certain equipment or other services used in operations, $0.2 million relating to purchases of property and equipment, $0.2 million relating to management, consulting and other services and $0.1 million relating to inventory and consumables. Tax Receivable Agreements In connection with the Select 144A Offering, the Company entered into the Tax Receivable Agreements with the TRA Holders. The first of the Tax Receivable Agreements, which the Company entered into with Legacy Owner Holdco and Crestview Partners II GP, L.P. (“Crestview GP”), generally provides for the payment by the Company to such TRA Holders of 85% of the net cash savings, if any, in U.S. federal, state and local income and franchise tax that the Company actually realizes (computed using simplifying assumptions to address the impact of state and local taxes) or is deemed to realize in certain circumstances in periods after the Select 144A Offering as a result of, as applicable to each such TRA Holder, (i) certain increases in tax basis that occur as a result of the Company’s acquisition (or deemed acquisition for U.S. federal income tax purposes) of all or a portion of such TRA Holder’s SES Holdings LLC Units in connection with the Select 144A Offering or pursuant to the exercise of the Exchange Right or the Company’s Call Right and (ii) imputed interest deemed to be paid by the Company as a result of, and additional tax basis arising from, any payments the Company makes under such Tax Receivable Agreement. The second of the Tax Receivable Agreements, which the Company entered into with an affiliate of certain Legacy Owners and Crestview GP, generally provides for the payment by the Company to such TRA Holders of 85% of the net cash savings, if any, in U.S. federal, state and local income and franchise tax that the Company actually realizes (computed using simplifying assumptions to address the impact of state and local taxes) or is deemed to realize in certain circumstances in periods after the Select 144A Offering as a result of, as applicable to each such TRA Holder, (i) any net operating losses available to the Company as a result of certain reorganization transactions entered into in connection with the Select 144A Offering and (ii) imputed interest deemed to be paid by the Company as a result of any payments the Company makes under such Tax Receivable Agreement. The Company has not recognized a liability associated with the Tax Receivable Agreements as of March 31, 2021 or December 31, 2020. ​

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2021
INCOME TAXES
INCOME TAXES	NOTE 12—INCOME TAXES The Company’s income tax information is presented in the table below. The effective tax rate is different than the 21% standard Federal rate due to net income allocated to noncontrolling interests, state income taxes and valuation allowances. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ (in thousands) Current income tax benefit ​ $ (197) ​ $ (72) ​ Deferred income tax benefit ​ ​ (66) ​ ​ (92) ​ Total income tax benefit ​ $ (263) ​ $ (164) ​ Effective Tax Rate ​ ​ 1.0% ​ ​ 0.1% ​ ​ On March 27, 2020, the CARES Act was enacted. The CARES Act includes, among other things, certain income tax provisions for businesses. The Company recognized an income tax benefit of $0.4 million during the Prior Quarter, as a result of the net operating loss carryback and interest expense limitation provisions of the CARES Act. ​

NONCONTROLLING INTERESTS

NONCONTROLLING INTERESTS	3 Months Ended
	Mar. 31, 2021
NONCONTROLLING INTERESTS
NONCONTROLLING INTERESTS	NOTE 13—NONCONTROLLING INTERESTS The Company’s noncontrolling interests fall into two categories as follows: ● Noncontrolling interests attributable to joint ventures formed for water-related services. ● Noncontrolling interests attributable to holders of Class B Common Stock. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ ​ ​ (in thousands) ​ Noncontrolling interests attributable to joint ventures formed for water-related services ​ ​ $ 1,080 $ 2,002 ​ Noncontrolling interests attributable to holders of Class B Common Stock ​ ​ ​ 105,494 110,819 ​ Total noncontrolling interests ​ ​ $ 106,574 $ 112,821 ​ ​ During the Current Quarter, the Company dissolved one of its water-related services joint ventures and increased its ownership interest in another joint venture, which combined eliminated $0.9 million of noncontrolling interest. During the Prior Quarter, there were no changes to Select’s ownership interest in joint ventures formed for water-related services. Additionally, for all periods presented, there were changes in Select’s ownership interest in SES Holdings LLC. The effects of the changes in Select’s ownership interest in SES Holdings LLC are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) Net loss attributable to Select Energy Services, Inc. ​ ​ $ (23,107) $ (245,862) Transfers from (to) noncontrolling interests: ​ ​ ​ ​ ​ Increase in additional paid-in capital as a result of restricted stock issuance, net of forfeitures ​ ​ 1,226 1,831 Increase in additional paid-in capital as a result of issuance of common stock due to vesting of restricted stock units ​ ​ ​ — ​ ​ 1 Decrease in additional paid-in capital as a result of the repurchase of SES Holdings LLC Units ​ ​ (15) (603) Increase in additional paid-in capital as a result of the Employee Stock Purchase Plan shares issued ​ ​ ​ — ​ ​ 3 Change to equity from net loss attributable to Select Energy Services, Inc. and transfers from noncontrolling interests ​ ​ $ (21,896) $ (244,630) ​

LOSS PER SHARE

LOSS PER SHARE	3 Months Ended
	Mar. 31, 2021
LOSS PER SHARE
LOSS PER SHARE	NOTE 14—LOSS PER SHARE Loss per share are based on the amount of loss allocated to the stockholders and the weighted-average number of shares outstanding during the period for each class of common stock. Outstanding options to purchase 2,272,441 and 3,777,228 shares of Class A Common Stock are not included in the calculation of diluted weighted-average shares outstanding for the Current Quarter and Prior Quarter, respectively, as the effect is antidilutive. The following tables present the Company’s calculation of basic and diluted loss per share for the Current and Prior Quarter (dollars in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ Three months ended March 31, 2020 ​ ​ Select Energy ​ ​ ​ ​ ​ ​ ​ Select Energy ​ ​ ​ ​ ​ ​ ​ Services, Inc. Class A Class B Services, Inc. Class A Class B Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (27,421) ​ ​ ​ ​ ​ ​ ​ $ (291,220) ​ ​ ​ ​ ​ ​ Net loss attributable to noncontrolling interests ​ ​ 4,314 ​ ​ ​ ​ ​ ​ ​ ​ 45,358 ​ ​ ​ ​ ​ ​ Net loss attributable to Select Energy Services, Inc. — basic ​ $ (23,107) ​ $ (23,107) ​ $ — ​ $ (245,862) ​ $ (245,862) ​ $ — Net loss attributable to Select Energy Services, Inc. — diluted ​ $ (23,107) ​ $ (23,107) ​ $ — ​ $ (245,862) ​ $ (245,862) ​ $ — Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares of common stock outstanding — basic ​ ​ ​ ​ ​ 84,989,945 ​ ​ 16,221,101 ​ ​ ​ ​ ​ 86,104,925 ​ ​ 16,221,101 Weighted-average shares of common stock outstanding — diluted ​ ​ ​ ​ ​ 84,989,945 ​ ​ 16,221,101 ​ ​ ​ ​ ​ 86,104,925 ​ ​ 16,221,101 Loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ ​ ​ ​ $ (0.27) ​ $ — ​ ​ ​ ​ $ (2.86) ​ $ — Diluted ​ ​ ​ ​ $ (0.27) ​ $ — ​ ​ ​ ​ $ (2.86) ​ $ — ​

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2021
SEGMENT INFORMATION
SEGMENT INFORMATION	NOTE 15—SEGMENT INFORMATION Select Inc. is a leading provider of comprehensive water-management and chemical solutions to the oil and gas industry in the U.S. The Company’s services are offered through three reportable segments. Reportable segments are defined as components of an enterprise for which separate financial information is evaluated regularly by the CODM in deciding how to allocate resources and assess performance. The Company’s CODM assesses performance and allocates resources on the basis of the three reportable segments. Corporate and other expenses that do not individually meet the criteria for segment reporting are reported separately as Corporate or Other. The Company’s CODM assesses performance and allocates resources on the basis of the following three reportable segments: Water Services Water Infrastructure ​ Oilfield Chemicals ​ Financial information by segment for the Current and Prior Quarter is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2021 ​ ​ ​ (Loss) Income Depreciation and Capital ​ ​ Revenue ​ before taxes ​ Amortization ​ Expenditures ​ ​ (in thousands) Water Services ​ $ 66,717 ​ $ (13,310) ​ $ 13,054 ​ $ 269 Water Infrastructure ​ ​ 37,805 ​ ​ 1,657 ​ ​ 6,255 ​ ​ 4,460 Oilfield Chemicals ​ ​ 41,812 ​ ​ (1,477) ​ ​ 2,340 ​ ​ 561 Other ​ ​ — ​ ​ (13) ​ ​ — ​ ​ 1 Eliminations ​ (2,592) ​ — ​ — ​ — Loss from operations ​ ​ ​ (13,143) ​ ​ ​ ​ Corporate ​ — ​ (11,901) ​ 650 ​ — Interest expense, net ​ — ​ (435) ​ — ​ — Other expense, net ​ — ​ (2,205) ​ — ​ — ​ ​ $ 143,742 ​ $ (27,684) ​ $ 22,299 ​ $ 5,291 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2020 ​ ​ ​ (Loss) Income Depreciation and Capital ​ ​ Revenue ​ before taxes ​ Amortization ​ Expenditures ​ ​ (in thousands) Water Services ​ $ 150,152 ​ $ (195,900) ​ $ 17,156 ​ $ 1,267 Water Infrastructure ​ ​ 57,884 ​ ​ (82,077) ​ ​ 7,028 ​ ​ 2,568 Oilfield Chemicals ​ ​ 71,028 ​ ​ (2,896) ​ ​ 1,998 ​ ​ 2,890 Other ​ ​ — ​ ​ 25 ​ ​ — ​ ​ 325 Eliminations ​ (779) ​ — ​ — ​ — Loss from operations ​ ​ ​ (280,848) ​ ​ ​ ​ Corporate ​ — ​ (9,983) ​ 685 ​ — Interest expense, net ​ — ​ (331) ​ — ​ — Other expense, net ​ — ​ (222) ​ — ​ — ​ ​ $ 278,285 ​ $ (291,384) ​ $ 26,867 ​ $ 7,050 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets by segment as of March 31, 2021 and December 31, 2020, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ March 31, 2021 December 31, 2020 ​ ​ (in thousands) Water Services ​ $ 494,495 ​ $ 515,856 Water Infrastructure ​ 206,825 ​ 204,995 Oilfield Chemicals ​ 151,078 ​ 147,612 Other ​ ​ 6,260 ​ ​ 6,896 ​ ​ $ 858,658 ​ $ 875,359 ​

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2021
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	NOTE 16—SUBSEQUENT EVENTS On April 20, 2021, an entity acquired in the Rockwater Merger formally pled guilty to violations of the Clean Air Act that occurred prior to the Rockwater Merger and entered a plea agreement before the U.S. District Court for the Middle District of Pennsylvania. Entry into this plea agreement has resolved the government’s prosecution related to Rockwater’s altering emissions controls systems on less than 5% of the vehicles in the fleet. The Company made final payments in April totaling $2.6 million, which was the amount accrued as of both March 31, 2021 and December 31, 2020, and did not incur additional monetary penalties or fines. The total amount paid in settlement of this matter was $4.3 million. ​

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2021
SIGNIFICANT ACCOUNTING POLICIES
Use of estimates	Use of estimates : The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the recoverability of long-lived assets and intangibles, useful lives used in depreciation and amortization, uncollectible accounts receivable, inventory reserve, income taxes, self-insurance liabilities, share-based compensation, contingent liabilities and the incremental borrowing rate for leases. The Company bases its estimates on historical and other pertinent information that are believed to be reasonable under the circumstances. The accounting estimates used in the preparation of the consolidated financial statements may change as new events occur, as more experience is acquired, as additional information is obtained and as the Company’s operating environment changes.
Allowance for credit losses	Allowance for credit losses: ​ The change in the allowance for credit losses is as follows: ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ ​ (in thousands) Balance at December 31, 2020 ​ $ 9,157 Increase to allowance based on a percent of revenue ​ 290 Charge-offs ​ ​ (830) Balance at March 31, 2021 ​ $ 8,617 ​ The Company also has a $3.1 million note receivable resulting from an investment in the fourth quarter of 2020, with no allowance for credit losses as of March 31, 2021. See Note 11 – Related Party Transactions for additional information.
Asset retirement obligations	Asset retirement obligations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ (in thousands) Balance at December 31, 2020 $ 999 Accretion expense, included in depreciation and amortization expense ​ 13 Payments ​ ​ (121) Balance at March 31, 2021 $ 891 ​ We review the adequacy of our ARO liabilities whenever indicators suggest that the estimated cash flows underlying the liabilities have changed. The Company’s ARO liabilities are included in accrued expenses and other current liabilities and other long-term liabilities in the accompanying consolidated balance sheets.
Lessor Income	Lessor Income: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) Category Classification ​ ​ ​ ​ ​ ​ Lessor income Costs of revenue ​ $ 66 ​ $ 116 Sublease income Lease abandonment costs and Costs of revenue ​ ​ 243 ​ ​ 401 ​ The Company also generates short-term equipment rental revenue. See Note 3—Revenue for a discussion of revenue recognition for the accommodations and rentals business.
Defined Contribution Plan	Defined Contribution Plan:
Payroll Tax Deferral	Payroll Tax Deferral:

BUSINESS AND BASIS OF PRESENT_2

BUSINESS AND BASIS OF PRESENTATION (Tables)	3 Months Ended
	Mar. 31, 2021
BUSINESS AND BASIS OF PRESENTATION
Schedule of investments in unconsolidated entities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) Type of Investment Year attained Accounting method Balance Sheet Location March 31, 2021 ​ December 31, 2020 20% minority interest 2011 Cost-method Other long-term assets, net $ 300 ​ $ 300 Notes receivable 2020 Amortized cost basis Other long-term assets, net ​ 3,096 ​ ​ 3,037 33% minority interest 2021 Equity-method Other long-term assets, net ​ 2,000 ​ ​ — Publicly traded securities 2020 Fair value option Prepaid expenses and other current assets ​ 1,546 ​ ​ 3,377

SIGNIFICANT ACCOUNTING POLICI_3

SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2021
SIGNIFICANT ACCOUNTING POLICIES
Schedule of change in allowance for doubtful accounts	​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ ​ (in thousands) Balance at December 31, 2020 ​ $ 9,157 Increase to allowance based on a percent of revenue ​ 290 Charge-offs ​ ​ (830) Balance at March 31, 2021 ​ $ 8,617
Summary of change in asset retirement obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ (in thousands) Balance at December 31, 2020 $ 999 Accretion expense, included in depreciation and amortization expense ​ 13 Payments ​ ​ (121) Balance at March 31, 2021 $ 891
Schedule of lessor income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) Category Classification ​ ​ ​ ​ ​ ​ Lessor income Costs of revenue ​ $ 66 ​ $ 116 Sublease income Lease abandonment costs and Costs of revenue ​ ​ 243 ​ ​ 401

REVENUE (Tables)

REVENUE (Tables)	3 Months Ended
	Mar. 31, 2021
REVENUE
Schedule of disaggregation of revenue by geographic location	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Geographic Region ​ ​ ​ ​ ​ ​ ​ Permian Basin ​ $ 71,204 ​ $ 137,998 ​ Eagle Ford ​ ​ 20,785 ​ ​ 35,664 ​ Haynesville/E. Texas ​ ​ 17,265 ​ ​ 19,015 ​ Marcellus/Utica ​ ​ 11,667 ​ ​ 19,839 ​ Rockies ​ ​ 10,022 ​ ​ 18,869 ​ MidCon ​ ​ 8,476 ​ ​ 24,873 ​ Bakken ​ ​ 6,903 ​ ​ 22,560 ​ Eliminations and other regions ​ ​ (2,580) ​ ​ (533) ​ Total ​ $ 143,742 ​ $ 278,285 ​

INVENTORIES (Tables)

INVENTORIES (Tables)	3 Months Ended
	Mar. 31, 2021
INVENTORIES
Schedule of inventory	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ (in thousands) Raw materials ​ $ 18,869 ​ $ 16,701 Finished goods ​ 15,541 ​ 16,683 Total ​ $ 34,410 ​ $ 33,384

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2021
PROPERTY AND EQUIPMENT..
Schedule of property and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ (in thousands) Machinery and equipment ​ $ 591,362 ​ $ 596,441 Buildings and leasehold improvements ​ 92,669 ​ 93,236 Pipelines ​ ​ 72,624 ​ ​ 72,458 Disposal wells ​ 47,571 ​ 48,097 Vehicles and equipment ​ 29,839 ​ 30,975 Land ​ ​ 12,803 ​ ​ 13,497 Computer equipment and software ​ ​ 6,790 ​ ​ 7,127 Office furniture and equipment ​ 888 ​ 892 Machinery and equipment - finance lease ​ 537 ​ 537 Vehicles and equipment - finance lease ​ 463 ​ 475 Computer equipment and software - finance lease ​ 356 ​ 356 Construction in progress ​ 14,189 ​ 14,811 ​ ​ 870,091 ​ 878,902 Less accumulated depreciation (1) ​ (537,199) ​ (528,537) Total property and equipment, net ​ $ 332,892 ​ $ 350,365 (1) Includes $1.1 million of accumulated depreciation related to finance leases as of March 31, 2021 and December 31, 2020.
Schedule of amortization of intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Category ​ ​ ​ ​ ​ ​ ​ Depreciation expense from property and equipment ​ $ 19,587 ​ $ 23,985 ​ Amortization expense from finance leases ​ ​ 82 ​ ​ 77 ​ Amortization expense from intangible assets ​ ​ 2,617 ​ ​ 2,993 ​ Accretion expense from asset retirement obligations ​ ​ 13 ​ ​ (188) ​ Total depreciation and amortization ​ $ 22,299 ​ $ 26,867 ​

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2021
GOODWILL AND OTHER INTANGIBLE ASSETS.
Summary of components of other intangible assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of March 31, 2021 ​ As of December 31, 2020 ​ Gross Accumulated Net Gross ​ ​ Accumulated Net ​ ​ Value ​ Amortization ​ Value ​ Value ​ Impairment ​ Amortization ​ Value ​ ​ (in thousands) ​ (in thousands) Definite-lived ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships ​ $ 116,554 ​ $ (31,568) ​ $ 84,986 ​ $ 116,554 ​ $ — ​ $ (29,302) ​ $ 87,252 Patents ​ ​ 9,741 ​ ​ (3,410) ​ ​ 6,331 ​ ​ 9,741 ​ ​ — ​ ​ (3,166) ​ ​ 6,575 Other ​ ​ 7,234 ​ ​ (6,479) ​ ​ 755 ​ 7,234 ​ ​ — ​ (6,373) ​ 861 Total definite-lived ​ ​ 133,529 ​ ​ (41,457) ​ ​ 92,072 ​ ​ 133,529 ​ ​ — ​ ​ (38,841) ​ ​ 94,688 Indefinite-lived ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Water rights ​ ​ 7,031 ​ ​ — ​ ​ 7,031 ​ ​ 7,031 ​ ​ — ​ ​ — ​ ​ 7,031 Trademarks ​ ​ 14,360 ​ ​ — ​ ​ 14,360 ​ ​ 23,442 ​ ​ (9,082) ​ ​ — ​ ​ 14,360 Total indefinite-lived ​ ​ 21,391 ​ ​ — ​ ​ 21,391 ​ ​ 30,473 ​ ​ (9,082) ​ ​ — ​ ​ 21,391 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total other intangible assets, net ​ $ 154,920 ​ $ (41,457) ​ $ 113,463 ​ $ 164,002 ​ $ (9,082) ​ $ (38,841) ​ $ 116,079
Summary of future estimated amortization expense for other intangible assets	​ ​ ​ ​ ​ ​ ​ Amount ​ ​ ​ (in thousands) ​ Remainder of 2021 ​ $ 7,850 ​ Year ending December 31, 2022 ​ 10,252 ​ Year ending December 31, 2023 ​ 10,180 ​ Year ending December 31, 2024 ​ 10,111 ​ Year ending December 31, 2025 ​ 9,948 ​ Thereafter ​ ​ 43,731 ​ Total ​ $ 92,072 ​

DEBT (Tables)

DEBT (Tables)	3 Months Ended
	Mar. 31, 2021
DEBT
Summary of Company's leverage ratio	​ ​ ​ ​ ​ ​ ​ ​ Level ​ Average Excess Availability ​ Base Rate Margin ​ Eurocurrency Rate Margin ​ ​ ​ ​ ​ ​ ​ I ​ < 33% of the commitments ​ 1.00% ​ 2.00% II ​ < 66.67% of the commitments and ≥ 33.33% of the commitments ​ 0.75% ​ 1.75% III ​ ≥ 66.67% of the commitments ​ 0.50% ​ 1.50%
Schedule of fee Percentage on unused credit facility	​ ​ ​ ​ ​ ​ Level ​ Average Revolver Usage ​ Unused Line Fee Percentage ​ ​ ​ ​ ​ I ​ ≥ 50% of the commitments ​ 0.250% II ​ < 50% of the commitments ​ 0.375%

EQUITY-BASED COMPENSATION (Tabl

EQUITY-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2021
Schedule of equity option activity and related information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2021 ​ ​ ​ ​ ​ ​ ​ Weighted-average ​ ​ ​ ​ ​ ​ ​ Weighted-average ​ Grant Date Value ​ Aggregate Intrinsic ​ Stock Options Exercise Price Term (Years) Value (in thousands) (a) Beginning balance, outstanding 3,519,159 ​ $ 16.11 ​ 3.3 ​ $ — Expired ​ (1,246,718) ​ ​ 14.28 ​ ​ ​ ​ ​ Ending balance, outstanding 2,272,441 ​ $ 17.11 ​ 4.8 ​ $ — Ending balance, exercisable ​ 2,272,441 ​ $ 17.11 ​ 4.8 ​ $ — Nonvested at March 31, 2021 ​ — ​ $ — ​ ​ ​ ​ ​ ​ (a)
summary of ESPP activity	The following table summarizes ESPP activity (in thousands, except shares): ​ ​ ​ ​ ​ ​ For the three months ended ​ March 31, 2021 Cash received for shares issued ​ $ 14 Shares issued ​ ​ 2,145
Restricted Stock
Schedule of restricted stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2021 ​ ​ ​ ​ Weighted-average ​ Restricted Stock Awards Grant Date Fair Value Nonvested at December 31, 2020 ​ 2,003,072 ​ $ 6.97 Granted ​ 1,487,448 ​ ​ 6.31 Vested ​ (484,816) ​ ​ 8.71 Forfeited ​ (301,395) ​ ​ 6.38 Nonvested at March 31, 2021 ​ 2,704,309 ​ $ 6.36
Performance share units
Schedule of percentage of target PSUs earned	​ ​ ​ ​ Return on Assets at Performance Period End Date ​ Percentage of Target PSUs Earned Less than 9.6% ​ 0% 9.6% ​ 50% 12% ​ 100% 14.4% ​ 175% ​ ​ ​ ​ Ranking Among Peer Group ​ Percentage of Target Amount Earned Outside of Top 10 ​ 0% Top 10 ​ 50% Top 7 ​ 100% Top 3 ​ 175% ​ ​ ​ ​ Adjusted FCF Performance Percentage ​ Percentage of Target Amount Earned Less than 70% ​ 0% 70% ​ 50% 100% ​ 100% 130% ​ 175%
Summary of activity related to the units outstanding	​ ​ ​ ​ ​ Performance Share Units Nonvested as of December 31, 2020 ​ 1,763,909 Target shares granted ​ 613,842 Target shares forfeited ​ (242,087) Target shares outstanding as of March 31, 2021 ​ 2,135,664

FAIR VALUE MEASUREMENT (Tables)

FAIR VALUE MEASUREMENT (Tables)	3 Months Ended
	Mar. 31, 2021
FAIR VALUE MEASUREMENT
Summary of assets and liabilities measured at fair value on a non-recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Measurements Using ​ Carrying ​ ​ ​ ​ ​ Frequency ​ Measurement Date Level 1 Level 2 Level 3 Value (1) Impairment ​ ​ ​ ​ ​ ​ (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Quarter Ended March 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Investments ​ Recurring ​ March 31 ​ ​ 1,546 ​ ​ — ​ ​ — ​ ​ 1,546 ​ ​ — (1) Amount represents carrying value at the date of assessment.

INCOME TAXES (Tables)

INCOME TAXES (Tables)	3 Months Ended
	Mar. 31, 2021
INCOME TAXES
Summary of components of the federal and state income tax expense (benefit)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ (in thousands) Current income tax benefit ​ $ (197) ​ $ (72) ​ Deferred income tax benefit ​ ​ (66) ​ ​ (92) ​ Total income tax benefit ​ $ (263) ​ $ (164) ​ Effective Tax Rate ​ ​ 1.0% ​ ​ 0.1% ​

NONCONTROLLING INTERESTS (Table

NONCONTROLLING INTERESTS (Tables)	3 Months Ended
	Mar. 31, 2021
NONCONTROLLING INTERESTS
Schedule of Non Controlling Interests Categories	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ ​ ​ (in thousands) ​ Noncontrolling interests attributable to joint ventures formed for water-related services ​ ​ $ 1,080 $ 2,002 ​ Noncontrolling interests attributable to holders of Class B Common Stock ​ ​ ​ 105,494 110,819 ​ Total noncontrolling interests ​ ​ $ 106,574 $ 112,821 ​
Summary of the effects of changes in noncontrolling interests	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, ​ ​ 2021 2020 ​ ​ ​ (in thousands) Net loss attributable to Select Energy Services, Inc. ​ ​ $ (23,107) $ (245,862) Transfers from (to) noncontrolling interests: ​ ​ ​ ​ ​ Increase in additional paid-in capital as a result of restricted stock issuance, net of forfeitures ​ ​ 1,226 1,831 Increase in additional paid-in capital as a result of issuance of common stock due to vesting of restricted stock units ​ ​ ​ — ​ ​ 1 Decrease in additional paid-in capital as a result of the repurchase of SES Holdings LLC Units ​ ​ (15) (603) Increase in additional paid-in capital as a result of the Employee Stock Purchase Plan shares issued ​ ​ ​ — ​ ​ 3 Change to equity from net loss attributable to Select Energy Services, Inc. and transfers from noncontrolling interests ​ ​ $ (21,896) $ (244,630)

LOSS PER SHARE (Tables)

LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2021
LOSS PER SHARE
Summary of calculation of basic and diluted earnings per share	The following tables present the Company’s calculation of basic and diluted loss per share for the Current and Prior Quarter (dollars in thousands, except share and per share amounts): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended March 31, 2021 ​ Three months ended March 31, 2020 ​ ​ Select Energy ​ ​ ​ ​ ​ ​ ​ Select Energy ​ ​ ​ ​ ​ ​ ​ Services, Inc. Class A Class B Services, Inc. Class A Class B Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (27,421) ​ ​ ​ ​ ​ ​ ​ $ (291,220) ​ ​ ​ ​ ​ ​ Net loss attributable to noncontrolling interests ​ ​ 4,314 ​ ​ ​ ​ ​ ​ ​ ​ 45,358 ​ ​ ​ ​ ​ ​ Net loss attributable to Select Energy Services, Inc. — basic ​ $ (23,107) ​ $ (23,107) ​ $ — ​ $ (245,862) ​ $ (245,862) ​ $ — Net loss attributable to Select Energy Services, Inc. — diluted ​ $ (23,107) ​ $ (23,107) ​ $ — ​ $ (245,862) ​ $ (245,862) ​ $ — Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares of common stock outstanding — basic ​ ​ ​ ​ ​ 84,989,945 ​ ​ 16,221,101 ​ ​ ​ ​ ​ 86,104,925 ​ ​ 16,221,101 Weighted-average shares of common stock outstanding — diluted ​ ​ ​ ​ ​ 84,989,945 ​ ​ 16,221,101 ​ ​ ​ ​ ​ 86,104,925 ​ ​ 16,221,101 Loss per share: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Basic ​ ​ ​ ​ $ (0.27) ​ $ — ​ ​ ​ ​ $ (2.86) ​ $ — Diluted ​ ​ ​ ​ $ (0.27) ​ $ — ​ ​ ​ ​ $ (2.86) ​ $ —

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2021
SEGMENT INFORMATION
Summary of financial information by segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2021 ​ ​ ​ (Loss) Income Depreciation and Capital ​ ​ Revenue ​ before taxes ​ Amortization ​ Expenditures ​ ​ (in thousands) Water Services ​ $ 66,717 ​ $ (13,310) ​ $ 13,054 ​ $ 269 Water Infrastructure ​ ​ 37,805 ​ ​ 1,657 ​ ​ 6,255 ​ ​ 4,460 Oilfield Chemicals ​ ​ 41,812 ​ ​ (1,477) ​ ​ 2,340 ​ ​ 561 Other ​ ​ — ​ ​ (13) ​ ​ — ​ ​ 1 Eliminations ​ (2,592) ​ — ​ — ​ — Loss from operations ​ ​ ​ (13,143) ​ ​ ​ ​ Corporate ​ — ​ (11,901) ​ 650 ​ — Interest expense, net ​ — ​ (435) ​ — ​ — Other expense, net ​ — ​ (2,205) ​ — ​ — ​ ​ $ 143,742 ​ $ (27,684) ​ $ 22,299 ​ $ 5,291 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended March 31, 2020 ​ ​ ​ (Loss) Income Depreciation and Capital ​ ​ Revenue ​ before taxes ​ Amortization ​ Expenditures ​ ​ (in thousands) Water Services ​ $ 150,152 ​ $ (195,900) ​ $ 17,156 ​ $ 1,267 Water Infrastructure ​ ​ 57,884 ​ ​ (82,077) ​ ​ 7,028 ​ ​ 2,568 Oilfield Chemicals ​ ​ 71,028 ​ ​ (2,896) ​ ​ 1,998 ​ ​ 2,890 Other ​ ​ — ​ ​ 25 ​ ​ — ​ ​ 325 Eliminations ​ (779) ​ — ​ — ​ — Loss from operations ​ ​ ​ (280,848) ​ ​ ​ ​ Corporate ​ — ​ (9,983) ​ 685 ​ — Interest expense, net ​ — ​ (331) ​ — ​ — Other expense, net ​ — ​ (222) ​ — ​ — ​ ​ $ 278,285 ​ $ (291,384) ​ $ 26,867 ​ $ 7,050 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total assets by segment as of March 31, 2021 and December 31, 2020, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of ​ As of ​ March 31, 2021 December 31, 2020 ​ ​ (in thousands) Water Services ​ $ 494,495 ​ $ 515,856 Water Infrastructure ​ 206,825 ​ 204,995 Oilfield Chemicals ​ 151,078 ​ 147,612 Other ​ ​ 6,260 ​ ​ 6,896 ​ ​ $ 858,658 ​ $ 875,359

BUSINESS AND BASIS OF PRESENT_3

BUSINESS AND BASIS OF PRESENTATION (Details)	3 Months Ended
	Mar. 31, 2021Voteitemsegment
BUSINESS AND BASIS OF PRESENTATION
Number of vote per share | Vote	1
Number of equity method investee	1
Number of cost-method investee	1
Number of investment in notes receivable	1
Number of investment in publicly traded securities	1
Number of operating segments | segment	3

BUSINESS AND BASIS OF PRESENT_4

BUSINESS AND BASIS OF PRESENTATION - Investments in Unconsolidated (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Other long-term assets, net
20% minority interest	$ 300	$ 300
Notes receivable	3,096	3,037
33% minority interest	2,000
Prepaid Expenses and Other Current Assets
Prepaid expenses and other current assets	$ 1,546	$ 3,377
Investment in Joint Venture One
Percentage of interest in a joint venture	20.00%
Investment in Joint Venture Two
Percentage of interest in a joint venture	33.00%

SIGNIFICANT ACCOUNTING POLICI_4

SIGNIFICANT ACCOUNTING POLICIES - Allowance activity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 9,157
Increase to allowance based on a percent of revenue	290
Charge-offs	(830)
Balance at end of year	8,617
Notes receivable with affiliates
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at end of year	0
Notes Receivables	$ 3,100

SIGNIFICANT ACCOUNTING POLICI_5

SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)lease	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of Current Period	$ 999
Accretion expense, included in depreciation and amortization expense	13
Payments	(121)
Balance at end of Current Period	$ 891
Lessor Income
Number of owned operating leases | lease	2
Lessor income	$ 66	$ 116
Sublease income	243	401
Defined Contribution Plan
401(k) match expense	0	$ 0
Payroll Tax Deferral	$ 6,000		$ 6,000

REVENUE (Details)

REVENUE (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)regionsegment	Mar. 31, 2020USD ($)segment
REVENUE
Number of Reportable Segments | segment	3	3
Contract liability	$ 8,200
Revenue	143,742	$ 278,285
Accommodations and rentals | ASC 842
REVENUE
Revenue	6,200	15,200
Permian Basin
REVENUE
Revenue	71,204	137,998
Eagle Ford
REVENUE
Revenue	20,785	35,664
Haynesville/E. Texas
REVENUE
Revenue	17,265	19,015
Marcellus/Utica
REVENUE
Revenue	11,667	19,839
Rockies
REVENUE
Revenue	10,022	18,869
MidCon
REVENUE
Revenue	8,476	24,873
Bakken
REVENUE
Revenue	6,903	22,560
Eliminations and other regions
REVENUE
Revenue	$ (2,580)	$ (533)
Permian Basin, Eagle Ford and Marcellus/Utica | Water Services
REVENUE
Number of revenue producing regions | region	3
Percentage of revenue	77.00%	74.00%
Permian Basin and Bakken | Water Infrastructure
REVENUE
Number of revenue producing regions | region	2
Percentage of revenue	86.00%	87.00%
Permian Basin, Haynesville/E. Texas and MidCon | Oilfield Chemicals
REVENUE
Number of revenue producing regions | region	3
Percentage of revenue	88.00%	81.00%

INVENTORIES (Details)

INVENTORIES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Significant components of inventory
Raw materials	$ 18,869		$ 16,701
Finished goods	15,541		16,683
Total	34,410		33,384
Inventory write-downs	54	$ 48
Inventory Valuation Reserves	4,100		$ 4,100
Maximum
Significant components of inventory
Inventory write-downs	$ 100	$ 100

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Property and equipment
Property and equipment	$ 870,091		$ 878,902
Accumulated depreciation	(537,199)		(528,537)
Total property and equipment, net	332,892		350,365
Accumulated depreciation related to finance leases	1,100		1,100
Depreciation and amortization expense
Depreciation expense from property and equipment	19,587	$ 23,985
Amortization expense from finance lease	82	77
Amortization expense from intangible assets	2,617	2,993
Accretion expense from asset retirement obligations	13	(188)
Total depreciation and amortization	22,299	26,867
Property and Equipment Held-for-Sale and Impairments
Impairment of property and equipment		$ 3,200
Machinery and equipment
Property and equipment
Property and equipment	591,362		596,441
Buildings and leasehold improvements
Property and equipment
Property and equipment	92,669		93,236
Pipelines
Property and equipment
Property and equipment	72,624		72,458
Disposal wells
Property and equipment
Property and equipment	47,571		48,097
Vehicles and equipment
Property and equipment
Property and equipment	29,839		30,975
Land
Property and equipment
Property and equipment	12,803		13,497
Computer equipment and software
Property and equipment
Property and equipment	6,790		7,127
Office furniture and equipment
Property and equipment
Property and equipment	888		892
Machinery and equipment - finance lease
Property and equipment
Property and equipment	537		537
Vehicles and equipment - finance lease
Property and equipment
Property and equipment	463		475
Computer equipment and software - finance lease
Property and equipment
Property and equipment	356		356
Construction in progress
Property and equipment
Property and equipment	$ 14,189		$ 14,811

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS - Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Water Services And Water Infrastructure
Goodwill
Impairment of Goodwill	$ 266.9

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS - Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Value, Definite-lived	$ 133,529		$ 133,529
Accumulated Amortization, Definite-lived	(41,457)	$ (41,457)	(38,841)
Total	92,072		94,688
Gross Value, Indefinite-lived	21,391		30,473
Impairment, Indefinite-lived			(9,082)
Net Value, Indefinite-lived	21,391		21,391
Intangible Assets, Gross (Excluding Goodwill)	154,920		164,002
Intangible Assets, Net (Excluding Goodwill)	113,463		116,079
Amortization of Intangible Assets	2,617	2,993
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Value, Definite-lived	116,554		116,554
Accumulated Amortization, Definite-lived	(31,568)		(29,302)
Total	$ 84,986		87,252
Weighted average amortization period	9 years 4 months 24 days
Patents
Finite-Lived Intangible Assets [Line Items]
Gross Value, Definite-lived	$ 9,741		9,741
Accumulated Amortization, Definite-lived	(3,410)		(3,166)
Total	$ 6,331		6,575
Weighted average amortization period	6 years 6 months
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Value, Definite-lived	$ 7,234		7,234
Accumulated Amortization, Definite-lived	(6,479)		(6,373)
Total	$ 755		861
Weighted average amortization period	2 years 6 months
Water rights
Finite-Lived Intangible Assets [Line Items]
Gross Value, Indefinite-lived	$ 7,031		7,031
Net Value, Indefinite-lived	$ 7,031		7,031
Renewal term	5 years
Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross Value, Indefinite-lived	$ 14,360		23,442
Impairment, Indefinite-lived		$ (9,100)	(9,082)
Net Value, Indefinite-lived	$ 14,360		$ 14,360
Renewal term	10 years

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS - Annual Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Annual amortization of intangible assets
Remainder of 2021	$ 7,850
Year Ending December 31, 2022	10,252
Year ending December 31, 2023	10,180
Year ending December 31, 2024	10,111
Year ending December 31, 2025	9,948
Thereafter	43,731
Total	$ 92,072	$ 94,688

DEBT (Details)

DEBT (Details) - USD ($) $ in Thousands	Nov. 01, 2017	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
DEBT
Amortization of debt issuance costs		$ 172	$ 172
Average excess availability, less than 33% of the commitments | Base Rate Advances
DEBT
Variable interest rate (as a percent)		1.00%
Average excess availability, less than 33% of the commitments | LIBOR
DEBT
Variable interest rate (as a percent)		2.00%
Average excess availability, less than 66.67% of the commitments and more than or equal to 33.33% of the commitments | Base Rate Advances
DEBT
Variable interest rate (as a percent)		0.75%
Average excess availability, less than 66.67% of the commitments and more than or equal to 33.33% of the commitments | LIBOR
DEBT
Variable interest rate (as a percent)		1.75%
Average excess availability, more than or equal to 66.67% of the commitments | Base Rate Advances
DEBT
Variable interest rate (as a percent)		0.50%
Average excess availability, more than or equal to 66.67% of the commitments | LIBOR
DEBT
Variable interest rate (as a percent)		1.50%
Average excess availability more than or equal to fifty percent
DEBT
Unused line fee (as a percent)		0.25%
Average excess availability less than fifty percent
DEBT
Unused line fee (as a percent)		0.375%
Eligible unbilled receivables
DEBT
Borrowing base (as a percent)	75.00%
Letter of credit
DEBT
Amount outstanding		$ 0		$ 0
Revolving line of credit
DEBT
Maximum borrowing capacity	$ 300,000
Revolving line of credit | Letter of credit
DEBT
Maximum borrowing capacity		117,800		96,400
Senior secured credit facility
DEBT
Percentage of borrowing base allowed	35.00%
Margin (as a percent)	2.00%
Reduction in borrowing capacity		15,600		15,600
Unused portion of available borrowing		102,200
Debt issuance costs		$ 1,100		$ 1,300
Senior secured credit facility | Minimum
DEBT
Percentage of borrowing base allowed	30.00%
Variable interest rate (as a percent)		1.50%
Senior secured credit facility | Maximum
DEBT
Variable interest rate (as a percent)		2.00%
Senior secured credit facility | Base Rate Advances | Minimum
DEBT
Margin (as a percent)	0.50%
Senior secured credit facility | Base Rate Advances | Maximum
DEBT
Margin (as a percent)	1.00%
Senior secured credit facility | LIBOR
DEBT
Margin (as a percent)	1.00%
Senior secured credit facility | LIBOR | Minimum
DEBT
Margin (as a percent)	1.50%
Senior secured credit facility | LIBOR | Maximum
DEBT
Margin (as a percent)	2.00%
Senior secured credit facility | Federal Funds Rate
DEBT
Margin (as a percent)	0.50%
Senior secured credit facility | Eligible billed receivables
DEBT
Borrowing base (as a percent)	85.00%
Senior secured credit facility | Eligible inventory
DEBT
Borrowing base (as a percent)	70.00%
Senior secured credit facility | Net recovery percentage
DEBT
Borrowing base (as a percent)	85.00%
Senior secured credit facility | Criteria for distributions, scenario one
DEBT
Lookback period	30 days
Percentage outstanding	25.00%
Base amount	$ 37,500
Senior secured credit facility | Criteria for distributions, scenario two
DEBT
Lookback period	30 days
Percentage outstanding	20.00%
Base amount	$ 30,000
Fixed charge coverage ratio	1.00%
Senior secured credit facility | Coverage Ratio Criteria
DEBT
Lookback period	60 days
Percentage outstanding	10.00%
Base amount	$ 15,000
Fixed charge coverage ratio	1.00%
Senior secured credit facility | Letter of credit
DEBT
Maximum borrowing capacity	$ 40,000
Senior secured credit facility | Swingline loan
DEBT
Maximum borrowing capacity	$ 30,000

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 28, 2021
COMMITMENTS AND CONTINGENCIES
Percentage of vehicles in which certain employees at some of the facilities altered emissions controls systems	5.00%
Litigation Settlement Accrual	$ 4,300,000
Litigation Payment Accrual	$ 1,700,000
Maximum contract amount		$ 35,000

EQUITY-BASED COMPENSATION (Deta

EQUITY-BASED COMPENSATION (Details) - shares	Nov. 01, 2017	Dec. 20, 2016	Mar. 31, 2021	May 08, 2020
Class A-1 Common Stock | Private Placement
EQUITY-BASED COMPENSATION
Shares issued		16,100,000
2016 plan
EQUITY-BASED COMPENSATION
Maximum number of shares	13,300,000		3,400,000
2016 plan | Maximum
EQUITY-BASED COMPENSATION
Equity options term	10 years
Second Amendment to the 2016 Plan [Member] | Class A Common Stock
EQUITY-BASED COMPENSATION
Maximum number of shares				4,000,000

EQUITY BASED COMPENSATION - Roc

EQUITY BASED COMPENSATION - Rockwater awards (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Restricted Stock
Assumptions for equity options granted:
Equity-based compensation expense	$ 1	$ 1.9
Equity options
Assumptions for equity options granted:
Equity-based compensation expense		$ 0.2
Equity options | Class A Common Stock
Assumptions for equity options granted:
Underlying Equity	$ 4.98		$ 4.10

EQUITY-BASED COMPENSATION - Equ

EQUITY-BASED COMPENSATION - Equity Options Changed During Period (Details) - Equity options - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Equity Options
Beginning balance (in shares)	3,519,159
Expired (in shares)	(1,246,718)
Ending balance (in shares)	2,272,441	3,519,159
Ending balance, exercisable (in shares)	2,272,441
Weighted-average Exercise Price
Beginning balance (in dollars per share)	$ 16.11
Expired (in dollars per share)	14.28
Ending balance (in dollars per share)	17.11	$ 16.11
Ending balance, exercisable	$ 17.11
Weighted-average Remaining Contractual Term (Years)
Outstanding	4 years 9 months 18 days	3 years 3 months 18 days
Ending balance, exercisable	4 years 9 months 18 days

EQUITY-BASED COMPENSATION - Res

EQUITY-BASED COMPENSATION - Restricted stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
EQUITY-BASED COMPENSATION
Payments for repurchase of common stock	$ 874	$ 6,636
Restricted Stock
EQUITY-BASED COMPENSATION
Compensation expense	$ 1,000	$ 1,900
Restricted Stock | Minimum
EQUITY-BASED COMPENSATION
offering period	1 year
Restricted Stock | Maximum
EQUITY-BASED COMPENSATION
offering period	3 years
Restricted Stock Awards
EQUITY-BASED COMPENSATION
Unrecognized compensation expense	$ 13,600
Weighted-average remaining life	2 years 4 months 24 days
Restricted stock
Beginning balance (in shares)	2,003,072
Granted (in shares)	1,487,448
Vested (in shares)	(484,816)
Forfeited (in shares)	(301,395)
Ending balance (in shares)	2,704,309
Grant Date Fair Value
Beginning balance (in dollars per share)	$ 6.97
Granted (in dollars per share)	6.31
Vested (in dollars per share)	8.71
Forfeited (in dollars per share)	6.38
Ending balance (in dollars per share)	$ 6.36

EQUITY-BASED COMPENSATION - Per

EQUITY-BASED COMPENSATION - Performance share units (Details) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2021USD ($)item	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2019item	Dec. 31, 2018item
Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of times shares issued for each performance share settlement | item				1	1
Grant date fair value of PSUs | $	$ 4.2	$ 4.4	$ 7
Compensation expense | $	0.4	$ (1.4)
Fair value of outstanding shares | $	$ 4.7
Weighted-average remaining life	2 years 3 months 18 days
Performance share units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of times shares issued for each performance share settlement | item	0
Percentage of Target PSUs Earned	0.00%
Performance share units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of times shares issued for each performance share settlement | item	1.75
Percentage of Target PSUs Earned	175.00%
Return on assets Less than 9.6% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned	0.00%
Return on assets 9.6% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned	50.00%
Return on assets 12% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned	100.00%
Return on assets 14.4% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned	175.00%
Peer Group Outside of Top 10 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	0.00%
Peer Group Top 10 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	50.00%
Peer Group Top 7 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	100.00%
Peer Group Top 3 | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	175.00%
Adjusted FCF Performance Percentage Less than 70% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	0.00%
Adjusted FCF Performance Percentage 70% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	50.00%
Adjusted FCF Performance Percentage 100% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	100.00%
Adjusted FCF Performance Percentage 130% | Performance share units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Amount Earned	175.00%
Return On Assets Five Percent [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target PSUs Earned	5.00%
Percentage of Target Amount Earned	5.00%

EQUITY-BASED COMPENSATION - P_2

EQUITY-BASED COMPENSATION - Performance share units outstanding (Details) - Performance share units	3 Months Ended
	Mar. 31, 2021shares
Performance share units
Beginning balance (in shares)	1,763,909
Target shares granted	613,842
Target shares forfeited	(242,087)
Ending balance (in shares)	2,135,664

EQUITY-BASED COMPENSATION - Emp

EQUITY-BASED COMPENSATION - Employee Stock Purchase Plan (ESPP) (Details) - ESPP	3 Months Ended
	Mar. 31, 2021USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
offering period	4 years
Issue price (percentage)	95.00%
Maximum annual employees contribution	$ 15,000
Cash received for shares issued	$ 14,000
Shares issued | shares	2,145
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee service period	1 year

EQUITY-BASED COMPENSATION - Sha

EQUITY-BASED COMPENSATION - Share-repurchases (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in paid-in capital	$ 874,000	$ 6,636,000
2016 plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares repurchased in open market		849,711
Number of shares repurchased with employee minimum tax withholding requirements	144,078	129,680
Decrease in paid in-capital	$ 900,000
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in Class A common stock	$ 1,400

FAIR VALUE MEASUREMENT (Details

FAIR VALUE MEASUREMENT (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers into or out of all levels of the fair value hierarchy	$ 0		$ 0
Impairment of property and equipment		$ 3,184
Recurring | March 31 | Carrying value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,546
Level 1 | Recurring | March 31 | Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 1,546

FAIR VALUE MEASUREMENT - Nonmon

FAIR VALUE MEASUREMENT - Nonmonetary transaction (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Sep. 30, 2020	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exchange for accounts receivable		$ 1,600
Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
common stock and related securities prepaid expenses	$ 1,546		$ 3,377
Other Nonoperating Income (Expense)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains/losses	$ 1,800

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
RELATED PARTY TRANSACTIONS
Sales to related parties	$ 0.3	$ 2.4
Purchases from related party vendors	$ 1.1	4.2
Minimum
RELATED PARTY TRANSACTIONS
Beneficial ownership (as a percent)	5.00%
Tax Receivable Agreement | Legacy Owner Holdco and Crestview GP
RELATED PARTY TRANSACTIONS
Percentage of net tax savings for payment to TRA Holders	85.00%
Tax Receivable Agreement | Contributing Legacy Owners
RELATED PARTY TRANSACTIONS
Percentage of net tax savings for payment to TRA Holders	85.00%
Property and equipment
RELATED PARTY TRANSACTIONS
Purchases from related party vendors		0.2
Inventory and consumables
RELATED PARTY TRANSACTIONS
Purchases from related party vendors		0.1
Rent of certain equipment or other services
RELATED PARTY TRANSACTIONS
Purchases from related party vendors	$ 0.9	3.7
Management, consulting and other services
RELATED PARTY TRANSACTIONS
Purchases from related party vendors	$ 0.2	$ 0.2

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
INCOME TAXES
Current income tax benefit	$ (197)	$ (72)
Deferred income tax benefit	(66)	(92)
Total income tax benefit	$ (263)	$ (164)
Effective Income tax (as percent)	1.00%	0.10%
Statutory tax rate (as a percent)	21.00%
Income tax benefit	$ 400

NONCONTROLLING INTERESTS (Detai

NONCONTROLLING INTERESTS (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
NONCONTROLLING INTERESTS
Noncontrolling interests attributable to joint ventures formed for water-related services	$ 1,080	$ 2,002
Noncontrolling interests attributable to holders of Class B Common Stock	105,494	110,819
Total noncontrolling interests	$ 106,574	$ 112,821

NONCONTROLLING INTERESTS - Effe

NONCONTROLLING INTERESTS - Effect of Changes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Effects of changes in noncontrolling interests on equity
Net loss attributable to Select Energy Services, Inc.	$ (23,107)	$ (245,862)
Transfers from (to) noncontrolling interests:
Noncontrolling interest in subsidiary	1,074
Increase in additional paid-in capital as a result of restricted stock issuance, net of forfeitures	1,226	1,831
Increase in additional paid-in capital as a result of issuance of common stock due to vesting of restricted stock units		1
Decrease in additional paid-in capital as a result of the repurchase of SES Holdings LLC Units	(15)	(603)
Increase in additional paid-in capital as a result of the Employee Stock Purchase Plan shares issued		3
Change to equity from net loss attributable to Select Energy Services, Inc. and transfers from noncontrolling interests	(21,896)	$ (244,630)
SES Holdings LLC [Member]
Transfers from (to) noncontrolling interests:
Noncontrolling interest in subsidiary	$ 900

LOSS PER SHARE (Details)

LOSS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Calculation of basic and diluted earnings per share:
Antidilutive shares	2,272,441	3,777,228
Net loss	$ (27,421)	$ (291,220)
Net loss attributable to noncontrolling interests	4,314	45,358
Net loss attributable to Select Energy Services, Inc.	(23,107)	(245,862)
Net loss attributable to Select Energy Services, Inc. - diluted	(23,107)	(245,862)
Class A Common Stock
Calculation of basic and diluted earnings per share:
Net loss attributable to Select Energy Services, Inc.	(23,107)	(245,862)
Net loss attributable to Select Energy Services, Inc. - diluted	$ (23,107)	$ (245,862)
Weighted-average shares of common stock outstanding - basic	84,989,945	86,104,925
Weighted-average shares of common stock outstanding - diluted	84,989,945	86,104,925
Earnings (loss) per share, Basic (in dollars per share)	$ (0.27)	$ (2.86)
Earnings (loss) per share, Diluted (in dollars per share)	$ (0.27)	$ (2.86)
Class B Common Stock
Calculation of basic and diluted earnings per share:
Weighted-average shares of common stock outstanding - basic	16,221,101	16,221,101
Weighted-average shares of common stock outstanding - diluted	16,221,101	16,221,101

SEGMENT INFORMATION (Details)

SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)segment	Mar. 31, 2020USD ($)segment
SEGMENT INFORMATION
Number of reportable segments | segment	3	3
Segment information
Revenue	$ 143,742	$ 278,285
(Loss) Income before taxes	(27,684)	(291,384)
Depreciation and Amortization	22,299	26,867
Capital Expenditures	5,291	7,050
Loss from operations	(25,044)	(290,831)
Other (expense) income, net	(1,629)	259
Operating segment | Water Services
Segment information
Revenue	66,717	150,152
(Loss) Income before taxes	(13,310)	(195,900)
Depreciation and Amortization	13,054	17,156
Capital Expenditures	269	1,267
Operating segment | Water Infrastructure
Segment information
Revenue	37,805	57,884
(Loss) Income before taxes	1,657	(82,077)
Depreciation and Amortization	6,255	7,028
Capital Expenditures	4,460	2,568
Operating segment | Oilfield Chemicals
Segment information
Revenue	41,812	71,028
(Loss) Income before taxes	(1,477)	(2,896)
Depreciation and Amortization	2,340	1,998
Capital Expenditures	561	2,890
Operating segment | Other
Segment information
(Loss) Income before taxes	(13)	25
Capital Expenditures	1	325
Elimination
Segment information
Revenue	(2,592)	(779)
Corporate
Segment information
(Loss) Income before taxes	(11,901)	(9,983)
Depreciation and Amortization	650	685
Material reconciling items
Segment information
Loss from operations	(13,143)	(280,848)
Interest expense, net	(435)	331
Other (expense) income, net	$ (2,205)	$ (222)

SEGMENT INFORMATION - Total Ass

SEGMENT INFORMATION - Total Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Assets	$ 858,658	$ 875,359
Operating segment | Water Services
Segment Reporting Information [Line Items]
Assets	494,495	515,856
Operating segment | Water Infrastructure
Segment Reporting Information [Line Items]
Assets	206,825	204,995
Operating segment | Oilfield Chemicals
Segment Reporting Information [Line Items]
Assets	151,078	147,612
Operating segment | Other
Segment Reporting Information [Line Items]
Assets	$ 6,260	$ 6,896

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ in Millions	Apr. 20, 2021	Dec. 31, 2020
Sale of subsidiary
Percentage of vehicles in which certain employees at some of the facilities altered emissions controls systems		5.00%
Settlement amount paid		$ 1.7
Subsequent Event
Sale of subsidiary
Percentage of vehicles in which certain employees at some of the facilities altered emissions controls systems	5.00%
Settlement amount paid	$ 2.6
Litigation Settlement	$ 4.3