Oasis Midstream Partners (OMP) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	OMP
Entity Registrant Name	Oasis Midstream Partners LP
Entity Central Index Key	1,652,133
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Common Units [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		13,779,026
Subordinated Units [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		13,750,000

Condensed Consolidated Balance

Condensed Consolidated Balance Sheet (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 4,990	$ 883
Accounts receivable	5,054	834
Accounts receivable from Oasis Petroleum	72,896	85,818
Prepaid expenses	96	778
Total current assets	83,036	88,313
Property, plant and equipment	876,534	653,928
Less: accumulated depreciation and amortization	(54,555)	(34,348)
Total property, plant and equipment, net	821,979	619,580
Other assets	1,981	2,013
Total assets	906,996	709,906
Current liabilities
Accounts payable	460	0
Accounts payable to Oasis Petroleum	24,940	11,638
Accrued liabilities	59,373	58,818
Accrued interest payable	172	114
Total current liabilities	84,945	70,570
Long-term debt	166,000	78,000
Asset retirement obligations	1,497	1,316
Total liabilities	252,442	149,886
Commitments and contingencies
Partners’ Equity
General Partner	0	0
Total partners’ equity	248,420	246,574
Non-controlling interests	406,134	313,446
Total equity	654,554	560,020
Total liabilities and equity	906,996	709,906
Common Units [Member]
Partners’ Equity
Limited Partners	168,387	167,401
Subordinated Units [Member]
Partners’ Equity
Limited Partners	$ 80,033	$ 79,173

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheet (Unaudited) Parenthetical - shares shares in Thousands	Sep. 30, 2018	Dec. 31, 2017
Common Units [Member]
Units issued (shares)	13,779	13,762
Units outstanding (shares)	13,779	13,762
Subordinated Units [Member]
Units issued (shares)	13,750	13,750
Units outstanding (shares)	13,750	13,750

Condensed Consolidated Statemen

Condensed Consolidated Statement of Operations (Unaudited) - USD ($) shares in Thousands	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Total revenues		$ 71,467,000	$ 47,381,000	$ 199,446,000	$ 125,333,000
Operating expenses
Direct operating		19,816,000	13,015,000	53,266,000	31,108,000
Depreciation and amortization		7,189,000	4,147,000	20,212,000	11,359,000
General and administrative		5,449,000	5,084,000	17,496,000	13,868,000
Total operating expenses		32,454,000	22,246,000	90,974,000	56,335,000
Operating income		39,013,000	25,135,000	108,472,000	68,998,000
Interest expense, net of capitalized interest		(163,000)	(2,733,000)	(608,000)	(6,965,000)
Other income (expense)		(15,000)	5,000	(15,000)	7,000
Total other income (expense)		(178,000)	(2,728,000)	(623,000)	(6,958,000)
Income before income taxes		38,835,000	22,407,000	107,849,000	62,040,000
Income tax expense		0	7,898,000	0	22,858,000
Net income	$ 1,605,000	38,835,000	14,509,000	107,849,000	39,182,000
Less: Net income attributable to non-controlling interests subsequent to the initial public offering	1,079,000	26,459,000		73,075,000
Net income attributable to Oasis Midstream Partners LP	$ 526,000	$ 12,376,000	526,000	$ 34,774,000	526,000
Common Units [Member]
Earnings per limited partner unit (Note 12)
Net income per limited partner unit (basic) subsequent to the Offering (in dollars per share)	$ 0.02	$ 0.45		$ 1.27
Weighted average number of limited partner units outstanding - Basic
Weighted average number of limited partner units outstanding (Basic) (shares)	12,625	13,751		13,750
Subordinated Units [Member]
Earnings per limited partner unit (Note 12)
Net income per limited partner unit (diluted) subsequent to the Offering (in dollars per share)	$ 0.02	$ 0.45		$ 1.26
Weighted average number of limited partner units outstanding - Diluted
Weighted average number of limited partner units outstanding (Diluted) (shares)	12,625	13,769		13,764
Oasis Petroleum [Member]
Revenues
Total revenues		$ 68,863,000	47,002,000	$ 194,694,000	123,777,000
Third Parties [Member]
Revenues
Total revenues		$ 2,604,000	$ 379,000	$ 4,752,000	$ 1,556,000

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Equity (Unaudited) - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Noncontrolling Interest [Member]	Unitholders [Member]Common Units [Member]	Unitholders [Member]Subordinated Units [Member]
Beginning balance at Dec. 31, 2017	$ 560,020	$ 313,446	$ 167,401	$ 79,173
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions from non-controlling interests	122,678	122,678
Distributions to non-controlling interests	(103,065)	(103,065)
Distributions to unitholders	(33,080)		(16,554)	(16,526)
Equity-based compensation	280		280
Other	(128)		(128)
Net income	107,849	73,075	17,388	17,386
Ending balance at Sep. 30, 2018	$ 654,554	$ 406,134	$ 168,387	$ 80,033

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 107,849	$ 39,182
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	20,212	11,359
Deferred income taxes	0	5,240
Equity-based compensation expenses	280	999
Deferred financing costs amortization and other	235	7
Working capital changes:
Change in accounts and insurance receivable	8,747	(8,479)
Change in other current assets	0	(94)
Change in prepaid expenses	682	445
Change in accounts payable and accrued liabilities	18,895	5,292
Change in current income taxes payable	0	17,618
Net cash provided by operating activities	156,900	71,569
Cash flows from investing activities:
Capital expenditures	(219,819)	(129,020)
Acquisitions	0	(7,841)
Net cash used in investing activities	(219,819)	(136,861)
Cash flows from financing activities:
Capital contributions from parent	0	65,145
Proceeds from the initial public offering, net of offering costs	0	115,813
Distribution to Oasis Petroleum subsequent to the initial public offering	0	(113,712)
Capital contributions from non-controlling interests	115,502	0
Distributions to non-controlling interests	(103,065)	0
Distributions to unitholders	(33,080)	0
Deferred financing costs	(331)	(1,954)
Proceeds from revolving credit facility	123,000	0
Principal payments on revolving credit facility	(35,000)	0
Net cash provided by financing activities	67,026	65,292
Increase in cash and cash equivalents	4,107	0
Beginning of period	883	0
End of period	4,990	0
Supplemental non-cash transactions:
Change in accrued capital expenditures	(4,520)	17,872
Change in asset retirement obligations	180	138
Installment notes from acquisition	0	4,875
Contribution of capital expenditures from non-controlling interests	$ 7,176	$ 0

Organization and Nature of Oper

Organization and Nature of Operations	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Nature of Operations	Organization and Nature of Operations Organization. Oasis Midstream Partners LP (the “Partnership” or “Oasis Midstream”) is a growth-oriented, fee-based master limited partnership formed by its sponsor, Oasis Petroleum Inc. (together with its subsidiaries, “Oasis Petroleum”) to own, develop, operate and acquire a diversified portfolio of midstream assets in North America that are integral to the crude oil and natural gas operations of Oasis Petroleum and are strategically positioned to capture volumes from other producers. Contributed businesses. The Partnership conducts its business through its ownership of development companies: Bighorn DevCo LLC (“Bighorn DevCo”), Bobcat DevCo LLC (“Bobcat DevCo”) and Beartooth DevCo LLC (“Beartooth DevCo,” and collectively with Bighorn DevCo and Bobcat DevCo, the “DevCos”). In connection with the Partnership’s initial public offering on September 25, 2017 , Oasis Petroleum contributed to the Partnership ownership interests in the following DevCos: DevCos Areas Served Service Lines Oasis Midstream Ownership Bighorn DevCo Wild Basin – Gas processing – Crude stabilization – Crude blending – Crude and NGL storage – Crude transportation 100% Bobcat DevCo Wild Basin – Gas gathering – Gas compression – Gas lift – Crude gathering – Produced and flowback water gathering – Produced and flowback water disposal 10% Beartooth DevCo Alger – Produced and flowback water gathering – Produced and flowback water disposal – Freshwater supply and distribution 40% In exchange for the contribution of ownership interests in the DevCos, Oasis Petroleum received 5,125,000 common units and 13,750,000 subordinated units, representing a limited partner interest in the Partnership and the right to receive cash distributions from the Partnership. In addition to and concurrent with the closing of the initial public offering, the Partnership’s general partner, OMP GP LLC (the “General Partner”), retained a non-economic general partnership interest and was issued incentive distribution rights in the Partnership (the “IDRs”). Nature of business. The Partnership operates in two primary areas with developed midstream infrastructure, both of which are supported by significant acreage dedications from Oasis Petroleum. In Wild Basin, Oasis Petroleum has dedicated to the Partnership approximately 65,000 acres, of which approximately 29,000 acres are within Oasis Petroleum’s current gross operated acreage position, and in which the Partnership has the right to provide crude oil, natural gas and produced and flowback water services to support Oasis Petroleum’s existing and future production. Outside of Wild Basin, Oasis Petroleum has dedicated to the Partnership approximately 581,000 acres for produced and flowback water services, of which approximately 299,000 acres are within Oasis Petroleum’s current gross operated acreage, and approximately 364,000 acres for freshwater services, of which approximately 203,000 acres are within Oasis Petroleum’s current gross operated acreage. The Partnership generates a substantial portion of its revenues through long-term, fee-based contractual arrangements with wholly owned subsidiaries of Oasis Petroleum for midstream services. These services include (i) gas gathering, compression, processing and gas lift services; (ii) crude gathering, stabilization, blending, storage and transportation services; (iii) produced and flowback water gathering and disposal services; and (iv) freshwater supply and distribution services. The revenue earned from these services is generally directly related to the volume of crude oil, natural gas, produced and flowback water and freshwater that flows through Oasis Midstream’s systems, and Oasis Midstream generally does not take ownership of the crude oil or natural gas that it handles for its customers, including Oasis Petroleum. Predecessor . Prior to the initial public offering on September 25, 2017, Oasis Petroleum’s midstream services were performed by Oasis Midstream Services LLC (“OMS”), which constitutes the predecessor to the Partnership for accounting purposes (the “Predecessor”). The condensed consolidated financial statements include the results of the Predecessor for the periods presented prior to the initial public offering on September 25, 2017. Certain midstream infrastructure assets, liabilities, revenues and expenses included in the Predecessor’s historical financial statements have been excluded from the businesses of the DevCos upon formation. These excluded assets are not included in the condensed consolidated financial statements for the periods presented subsequent to the initial public offering on September 25, 2017. Substantially all of the services of the Predecessor were provided to Oasis Petroleum North America LLC (“OPNA”), a wholly owned subsidiary of Oasis Petroleum that conducts Oasis Petroleum’s crude oil and natural gas exploration and production activities in the Williston Basin. The Predecessor financial statements have been prepared from the separate records maintained by Oasis Petroleum and may not necessarily be indicative of the actual results of operations that might have occurred if the Predecessor had been operated separately during the periods reported.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Presentation The accompanying condensed consolidated financial statements of the Partnership have not been audited by the Partnership’s independent registered public accounting firm, except that the Condensed Consolidated Balance Sheet at December 31, 2017 is derived from audited financial statements. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for fair statement of the Partnership’s financial position have been included. Management has made certain estimates and assumptions that affect reported amounts in the condensed consolidated financial statements and disclosures of contingencies. Actual results may differ from those estimates. The results for interim periods are not necessarily indicative of annual results. These interim financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain disclosures have been condensed or omitted from these financial statements. Accordingly, they do not include all of the information and notes required by accounting principles generally accepted in the United States of America (“GAAP”) for complete consolidated financial statements and should be read in conjunction with the Partnership’s audited consolidated financial statements and notes thereto included in the Partnership’s Annual Report on Form 10-K for the year ended December 31, 2017 (“ 2017 Annual Report”). Consolidation The Partnership’s condensed consolidated financial statements include its accounts and the accounts of the DevCos. With respect to Bobcat DevCo and Beartooth DevCo, management has determined that OMS’s equity at risk was established with non-substantive voting rights, making Bobcat DevCo and Beartooth DevCo variable interest entities (“VIEs”) under the rules of the Financial Accounting Standards Board (“FASB”). Through its 100% ownership interest in OMP Operating LLC (“OMP Operating”), which owns controlling interests in Bobcat DevCo and Beartooth DevCo, the Partnership has the authority to direct the activities that most significantly affect the economic performance of these entities and the obligation to absorb losses or the right to receive benefits that could be potentially significant to them. Therefore, the Partnership is considered the primary beneficiary of Bobcat DevCo and Beartooth DevCo and is required to consolidate these entities in its financial statements under the VIE consolidation model. With respect to Bighorn DevCo, the Partnership is required to consolidate Bighorn DevCo under the voting interest consolidation model because Bighorn DevCo is an indirect wholly owned subsidiary of the Partnership. Non-Controlling Interests The non-controlling interests represent Oasis Petroleum’s retained ownership interest in Bobcat DevCo and Beartooth DevCo of 90% and 60% , respectively. Significant Accounting Policies There have been no material changes to the Partnership’s critical accounting policies and estimates from those disclosed in the 2017 Annual Report, other than as noted below. Revenue recognition. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2014-09, R evenue from Contracts with Customers (“ASU 2014-09”), which uses a five-step model to recognize revenue from customer contracts. ASU 2014-09 was applied on a modified retrospective basis. The adoption of ASU 2014-09 did not result in a material impact to the Partnership’s financial position, cash flows or results of operations. Disclosures in accordance with the requirements of ASU 2014-09 have been provided in Note 3 . Statement of cash flows. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2016-15, Statement of Cash Flows (“ASU 2016-15”), which is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. ASU 2016-15 was applied on a retrospective basis. The adoption of ASU 2016-15 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures. Business combinations. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2017-01, Clarifying the Definition of a Business (“ASU 2017-01”), which provides guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. ASU 2017-01 was adopted on a prospective basis. The adoption of ASU 2017-01 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures. Equity-based compensation. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2017-09, Scope of Modification Accounting (“ASU 2017-09”), which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. ASU 2017-09 was adopted on a prospective basis. The adoption of ASU 2017-09 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures. Recent Accounting Pronouncements Leases. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (“ASU 2016-02”), which requires a lessee to recognize lease payment obligations and a corresponding right-of-use asset to be measured at fair value on the balance sheet. ASU 2016-02 also requires certain qualitative and quantitative disclosures about the amount, timing and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those years. In January 2018, the FASB issued Accounting Standards Update No. 2018-01, Land easement practical expedient for transition to Topic 842 , which provides an optional transition practical expedient to not evaluate under Topic 842 existing or expired land easements that were not previously accounted for as leases under Topic 840, Leases . The Partnership plans to elect this practical expedient. In July 2018, the FASB issued Accounting Standards Update No. 2018-11, Targeted Improvements - Lease Topic 842 , which allows entities another option for transition and also provides lessors with a practical expedient to combine lease and non-lease components. The Partnership will adopt the new leases standard using the required modified retrospective approach and plans to elect the option to recognize a cumulative effect adjustment of initially applying the guidance to the opening balance of retained earnings in the period of adoption, rather than recognizing in the earliest period presented. Prior period amounts will not be adjusted. The Partnership is in the process of analyzing its lease arrangements and is continuing to identify and put in place necessary changes to its business processes and controls to support the adoption of the new standard, including implementing a new lease accounting software to assess the portfolio of leases, assist in the quantification of the expected impact on the consolidated financial statements and facilitate the calculations of the related accounting entries and disclosures. The Partnership is currently evaluating the effect that adopting the new lease guidance will have on its financial position, cash flows and results of operations.

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition In May 2014, the FASB issued a new accounting standard related to revenue recognition, ASC 606 - Revenue from Contracts with Customers (“ASC 606”). This standard was effective in the first quarter of 2018 and the Partnership adopted the new standard using the modified retrospective method. The Partnership applied ASC 606 to all new contracts entered into after January 1, 2018 and all existing contracts for which all (or substantially all) of the revenue has not been recognized under legacy revenue guidance as of December 31, 2017. ASC 606 supersedes previous revenue recognition requirements in ASC 605 and includes a five-step revenue recognition model to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the Partnership expects to be entitled in exchange for those goods or services. In accordance with the adoption of ASC 606, management evaluated its contracts with customers to apply the five-step revenue recognition model. The adoption of ASC 606 did not result in a material impact to the Partnership’s financial position, cash flows or results of operations. Revenue from contracts with customers The unit of account in ASC 606 is a performance obligation, which is a promise in a contract to transfer to a customer either a distinct good or service (or bundle of goods or services) or a series of distinct goods or services provided over a period of time. ASC 606 requires that a contract’s transaction price, which is the amount of consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, is to be allocated to each performance obligation in the contract based on relative standalone selling prices and recognized as revenue when (point in time) or as (over time) the performance obligation is satisfied. Crude oil and natural gas revenues. The Partnership is party to certain contracts for crude oil gathering, stabilization, blending, storage and transportation, as well as natural gas gathering, compression, processing and gas lift services. Under these customer contracts, the Partnership has a series of performance obligations to provide daily integrated midstream services on a stand ready basis over a period of time. This represents a single performance obligation since the customer simultaneously receives and consumes the benefits of these services on a daily basis. Satisfaction of the performance obligation is measured as each day of service is completed, which directly corresponds with its right to consideration from the customer. Revenues associated with these contracts are recognized based upon the transaction price at month-end under the right to invoice practical expedient. Payments are typically due from customers 30 days after receipt of invoice. Water revenues. The Partnership is also party to certain contracts with customers for water services, which includes produced and flowback water gathering and disposal services and freshwater supply and distribution services. Under its customer contracts for produced and flowback water services, the Partnership has a series of performance obligations to provide daily integrated midstream services on a stand ready basis over a period of time. This represents a single performance obligation since the customer simultaneously receives and consumes the benefits of these services on a daily basis. Satisfaction of the performance obligation is measured as each day of service is completed, which directly corresponds with its right to consideration from the customer. Revenues associated with these contracts are recognized based upon the transaction price at month-end under the right to invoice practical expedient. Payments are typically due from customers 30 days after receipt of invoice. Under its customer contracts for freshwater supply and distribution services, the Partnership supplies and distributes freshwater to its customers for hydraulic fracturing and production optimization. These contracts contain multiple distinct performance obligations since each freshwater barrel can be sold separately and is not dependent or highly interrelated with other barrels. Revenue associated with freshwater supply and distribution services is recognized at a point in time based upon the transaction price when title, control and risk of loss transfers to the customer, which occurs at the delivery point. Payments are due from customers 30 days after receipt of invoice. Disaggregation of revenues The following table summarizes revenues associated with contracts with customers for crude oil, natural gas and water services for the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Crude oil and natural gas services revenue $ 34,347 $ 22,419 $ 98,489 $ 59,798 Water services revenue 37,120 24,962 100,957 65,535 Total revenues $ 71,467 $ 47,381 $ 199,446 $ 125,333 Contract balances Under the Partnership’s customer contracts, invoicing occurs once the Partnership’s performance obligations have been satisfied, at which point payment is unconditional. Accordingly, the Partnership’s contracts do not give rise to contract assets or liabilities under ASC 606. Performance obligations The majority of the Partnership’s customer contracts have a term greater than one year. The Partnership recognizes revenue under the right to invoice practical expedient for its contracts for crude oil, natural gas and produced and flowback water services and is not required to disclose the transaction price allocated to remaining performance obligations. Under the Partnership’s customer contracts for freshwater supply and distribution services, each barrel of freshwater delivered represents a separate performance obligation; therefore, future volumes delivered are wholly unsatisfied and disclosure of the transaction price allocated to remaining performance obligations is not required.

Transactions with Affiliates

Transactions with Affiliates	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Transactions with Affiliates	Transactions with Affiliates Revenues. The Partnership generates a substantial portion of its revenues through 15 -year, fee-based contractual arrangements with wholly owned subsidiaries of Oasis Petroleum for midstream services. These services include (i) gas gathering, compression, processing and gas lift services; (ii) crude gathering, stabilization, blending, storage and transportation services; (iii) produced and flowback water gathering and disposal services; and (iv) freshwater supply and distribution services. The revenue earned from these services is generally directly related to the volume of crude oil, natural gas, produced and flowback water and freshwater that flows through the Partnership’s systems, and the Partnership generally does not take ownership of the crude oil or natural gas that it handles for its customers, including Oasis Petroleum. Expenses. Oasis Petroleum provides substantial labor and overhead support for the Partnership. The Partnership is party to a 15 -year services and secondment agreement with Oasis Petroleum pursuant to which Oasis Petroleum provides all personnel, equipment, electricity, chemicals and services (including third-party services) required for the Partnership to operate such assets, and the Partnership reimburses Oasis Petroleum for its share of the actual costs of operating such assets (the “Services and Secondment Agreement”). In addition, pursuant to the Services and Secondment Agreement, Oasis Petroleum performs centralized corporate, general and administrative services for the Partnership, such as legal, corporate recordkeeping, planning, budgeting, regulatory, accounting, billing, business development, treasury, insurance administration and claims processing, risk management, health, safety and environmental, information technology, human resources, investor relations, cash management and banking, payroll, internal audit, tax and engineering. Oasis Petroleum has also seconded to the Partnership certain of its employees to operate, construct, manage and maintain its assets, and the Partnership reimburses Oasis Petroleum for direct general and administrative expenses incurred by Oasis Petroleum for the provision of these services. The expenses of executive officers and non-executive employees are allocated to the Partnership based on the amount of time spent managing its business and operations. For the periods prior to the initial public offering, shared services and direct labor were allocated to the Predecessor primarily based on headcount and direct usage during the respective years. Management believes that these allocations are reasonable and reflect the utilization of services provided and benefits received, but may differ from the cost that would have been incurred had the Predecessor operated as a stand-alone company for the periods presented prior to the initial public offering. Additionally, for the period prior to the initial public offering, interest expense was recognized by the Predecessor related to its funding activity with Oasis Petroleum based on capital expenditures for the period using the weighted average effective interest rate for Oasis Petroleum’s long-term indebtedness. General and administrative expenses and interest expense incurred from affiliate transactions with Oasis Petroleum include the following for the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Expenses from affiliates General and administrative $ 4,490 $ 2,895 $ 15,320 $ 8,416 Interest expense, net of capitalized interest — 2,714 — 6,945

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities The following table sets forth the Partnership’s accrued liabilities for the periods presented: September 30, 2018 December 31, 2017 (In thousands) Accrued capital costs $ 43,323 $ 47,843 Accrued operating expenses 16,007 10,860 Other accrued liabilities 43 115 Total accrued liabilities $ 59,373 $ 58,818

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment The following table sets forth the Partnership’s property, plant and equipment for the periods presented: September 30, 2018 December 31, 2017 (In thousands) Pipelines $ 364,199 $ 255,231 Natural gas processing plant 112,563 102,371 Produced and flowback water facilities 92,646 80,050 Compressor stations 95,972 59,293 Other property and equipment 33,737 32,340 Construction in progress 177,417 124,643 Total property, plant and equipment 876,534 653,928 Less: accumulated depreciation and amortization (54,555 ) (34,348 ) Total property, plant and equipment, net $ 821,979 $ 619,580

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt On September 25, 2017, the Partnership entered into a credit agreement (the “Credit Agreement”) for a $200.0 million revolving credit facility with OMP Operating as borrower (the “Revolving Credit Facility”), which has a maturity date of September 25, 2022 . On August 27, 2018 , the Partnership entered into an amendment to the Credit Agreement to (i) increase the aggregate amount of commitments from $200.0 million to $250.0 million ; (ii) provide for the ability to further increase commitments to $400.0 million ; and (iii) add six new lenders to the bank group. The Revolving Credit Facility is available to fund working capital and to finance acquisitions and other capital expenditures of the Partnership. The Revolving Credit Facility includes a letter of credit sublimit of $10.0 million and a swingline loans sublimit of $10.0 million . All obligations of OMP Operating, as the borrower under the Revolving Credit Facility, are unconditionally guaranteed on a joint and several basis by the Partnership, OMP Operating and Bighorn DevCo. At September 30, 2018 , $166.0 million of borrowings were outstanding under the Revolving Credit Facility, and the weighted average interest rate on borrowings under the Revolving Credit Facility was 4.0% . The Revolving Credit Facility is collateralized by mortgages and other security interests on substantially all of the Partnership’s and its subsidiaries’ properties and assets, including the equity interests in all present and future subsidiaries (subject to certain exceptions). Some or all of the collateral owned by Bobcat DevCo and Beartooth DevCo is subject to an intercreditor agreement between Wells Fargo, National Association (“Wells Fargo”), as administrative agent for the Revolving Credit Facility, and Wells Fargo as the administrative agent for the revolving credit facility of Oasis Petroleum, and acknowledged by OMS, Bobcat DevCo and Beartooth DevCo. The Revolving Credit Facility provides for customary representations, warranties and covenants, including, among other things, covenants relating to financial and collateral reporting, notices of material events, maintenance of the existence of the business and its properties, payment of obligations, the Partnership’s ability to enter into certain hedging agreements, limitations on the Partnership’s ability to sell or acquire properties and limitations on indebtedness and liens, dividends and distributions, transactions with affiliates and certain fundamental transactions. Borrowings under the Revolving Credit Facility bear interest at a rate per annum equal to the applicable margin (as described below) plus (i) with respect to Eurodollar Loans, the Adjusted LIBO Rate (as defined in the Credit Agreement) or (ii) with respect to ABR Loans, the greatest of (A) the Prime Rate in effect on such day, (B) the Federal Funds Effective Rate in effect on such day plus 1/2 of 1.00% or (C) the Adjusted LIBO Rate for a one-month interest period on such day plus 1.00% (each as defined in the Credit Agreement). The applicable margin for borrowings under the Revolving Credit Facility is determined in accordance with the Credit Agreement as follows: Consolidated Total Leverage Ratio Applicable Margin for Eurodollar Loans Applicable Margin for ABR Loans Commitment Fee Rate Less than or equal to 3.00 to 1.00 1.75 % 0.75 % 0.375 % Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 2.00 % 1.00 % 0.375 % Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 2.25 % 1.25 % 0.500 % Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 2.50 % 1.50 % 0.500 % Greater than 4.50 to 1.00 2.75 % 1.75 % 0.500 % The Revolving Credit Facility also requires the Partnership to maintain the following financial covenants as of the end of each fiscal quarter: • Consolidated Total Leverage Ratio : Prior to the date on which one or more of the credit parties have issued an aggregate principal amount of at least $150.0 million of senior notes (as permitted under the Revolving Credit Facility) (such date the “Covenant Changeover Date”), the Partnership and OMP Operating’s ratio of Total Debt to EBITDA (each as defined in the Credit Agreement) on a quarterly basis may not exceed 4.50 to 1.00 (or during an Acquisition Period (as defined in the Credit Agreement), 5.00 to 1.00 ). On a quarterly basis following the Covenant Changeover Date, the Partnership and OMP Operating’s ratio of Total Debt to EBITDA may not exceed 5.25 to 1.00 . • Consolidated Senior Secured Leverage Ratio : On a quarterly basis following the Covenant Changeover Date, the Partnership and OMP Operating’s ratio of Consolidated Senior Secured Funded Debt to EBITDA (each as defined in the Credit Agreement) may not exceed 3.75 to 1.00 . • Consolidated Interest Coverage Ratio : On a quarterly basis prior to the Covenant Changeover Date, the Partnership and OMP Operating’s ratio of EBITDA to Consolidated Interest Expense (each as defined in the Credit Agreement) may not be less than 3.00 to 1.00 and on a quarterly basis following the Covenant Changeover Date, the Partnership and OMP Operating’s ratio of EBITDA to Consolidated Interest Expense may not be less than 2.50 to 1.00 . The Partnership was in compliance with the financial covenants of the Revolving Credit Facility at September 30, 2018 .

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Partnership is not a taxable entity for U.S. federal income tax purposes, and taxes are generally borne by unitholders through the allocation of taxable income. Accordingly, for the periods subsequent to the initial public offering, the Partnership does not record deferred taxes related to the aggregate differences in the tax bases and reported amounts of its assets and liabilities. The Partnership did not record a tax provision for the three and nine months ended September 30, 2018 . The provision for income taxes recorded by the Predecessor for the three and nine months ended September 30, 2017 was determined as if the Predecessor was a stand-alone taxpayer for the period prior to the initial public offering on September 25, 2017 . The Predecessor’s effective tax rate for the three and nine months ended September 30, 2017 was 35.2% and 36.8% , respectively. The effective tax rates for the three and nine months ended September 30, 2017 were lower than the statutory tax rate applicable to the U.S. and the blended state rate for the states in which the Predecessor conducted its business primarily due to earnings not subject to tax for the period subsequent to the initial public offering on September 25, 2017 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Partnership has various contractual obligations in the normal course of its operations. Currently, there are no unrecorded commitments in the accompanying Condensed Consolidated Balance Sheets as of September 30, 2018 . Water volume commitment agreements. As of September 30, 2018 , the Partnership had certain agreements with an aggregate requirement to deliver a minimum quantity of approximately 16.3 million barrels of water, prior to any applicable volume credits, within specified timeframes, all of which are ten years or less. The estimable future commitments under these agreements were approximately $10.9 million as of September 30, 2018 . Litigation. The Partnership is party to various legal and/or regulatory proceedings from time to time arising in the ordinary course of business. When the Partnership determines that a loss is probable of occurring and is reasonably estimable, the Partnership accrues an undiscounted liability for such contingencies based on its best estimate using information available at the time. The Partnership discloses contingencies where an adverse outcome may be material, or where in the judgment of management, the matter should otherwise be disclosed. Mirada litigation . On March 23, 2017, Mirada filed a lawsuit against Oasis Petroleum, OPNA, and OMS, seeking monetary damages in excess of $100.0 million , declaratory relief, attorneys’ fees and costs (Mirada Energy, LLC, et al. v. Oasis Petroleum North America LLC, et al.; in the 334th Judicial District Court of Harris County, Texas; Case Number 2017-19911). In its original lawsuit, Mirada asserts that it is a working interest owner in certain acreage owned and operated by Oasis Petroleum in Wild Basin. Specifically, Mirada asserts that Oasis Petroleum has breached certain agreements by: (1) failing to allow Mirada to participate in Oasis Petroleum’s midstream operations in Wild Basin; (2) refusing to provide Mirada with information that Mirada contends is required under certain agreements and failing to provide information in a timely fashion; (3) failing to consult with Mirada and failing to obtain Mirada’s consent prior to drilling more than one well at a time in Wild Basin; and (4) overstating the estimated costs of proposed well operations in Wild Basin. Mirada seeks a declaratory judgment that OPNA be removed as operator in Wild Basin at Mirada’s election and that Mirada be allowed to elect a new operator; that certain agreements apply to Oasis Petroleum and Mirada and Wild Basin with respect to this dispute; that Oasis Petroleum be required to provide all information within its possession regarding proposed or ongoing operations in Wild Basin; and that OPNA not be permitted to drill, or propose to drill, more than one well at a time in Wild Basin without obtaining Mirada’s consent. Mirada also seeks a declaratory judgment with respect to Oasis Petroleum’s current midstream operations in Wild Basin. Specifically, Mirada seeks a declaratory judgment that Mirada has a right to participate in Oasis Petroleum’s Wild Basin midstream operations, consisting of produced and flowback water disposal, crude oil gathering and gas gathering and processing; that, upon Mirada’s election to participate, Mirada is obligated to pay its proportionate costs of Oasis Petroleum’s midstream operations in Wild Basin; and that Mirada would then be entitled to receive a share of revenues from the midstream operations and would not be charged any amount for its use of these facilities for production from the “Contract Area.” On June 30, 2017, Mirada amended its original petition to add a claim that Oasis Petroleum has breached certain agreements by charging Mirada for midstream services provided by its affiliates and to seek a declaratory judgment that Mirada is entitled to be paid its share of total proceeds from the sale of hydrocarbons received by OPNA or any affiliate of OPNA without deductions for midstream services provided by OPNA or its affiliates. On February 2, 2018 and February 16, 2018, Mirada filed a second and third amended petition, respectively. In these filings, Mirada alleged new legal theories for being entitled to enforce the underlying contracts, and added Bighorn DevCo LLC, Bobcat DevCo LLC and Beartooth DevCo LLC as defendants, asserting that these entities were created in bad faith in an effort to avoid contractual obligations owed to Mirada. Mirada may further amend its petition from time to time to assert additional claims as well as defendants. On March 2, 2018, Mirada filed a fourth amended petition that described Mirada’s alleged ownership and assignment of interests in assets purportedly governed by agreements at issue in the lawsuit. On August 31, 2018, Mirada filed a fifth amended petition that added the Partnership as a defendant, asserting that it was created in bad faith in an effort to avoid contractual obligations owed to Mirada. Oasis Petroleum believes that Mirada’s claims are without merit, that Oasis Petroleum has complied with its obligations under the applicable agreements and that some of Mirada’s claims are grounded in agreements which do not apply to Oasis Petroleum. Oasis Petroleum filed answers denying all of Mirada’s claims and intends to continue to vigorously defend against Mirada’s claims. The Partnership has not yet filed an answer because it has not yet been served with process. Discovery is ongoing, and each of the parties has made a number of procedural filings and motions, and additional filings and motions can be expected over the course of the claim. Trial is currently scheduled for May 2019. However, neither we nor Oasis Petroleum can predict or guarantee the ultimate outcome or resolution of such matter. If such matter were to be determined adversely to our or Oasis Petroleum’s interests, or if we or Oasis Petroleum were forced to settle such matter for a significant amount, such resolution or settlement could have a material adverse effect on our business, results of operations and financial condition. Such an adverse determination could materially impact Oasis Petroleum’s ability to operate its properties in Wild Basin or develop its identified drilling locations in Wild Basin on its current development schedule. A determination that Mirada has a right to participate in Oasis Petroleum’s midstream operations could materially reduce the interests of Oasis Petroleum and us in our current assets and future midstream opportunities and related revenues in Wild Basin. Under the Omnibus Agreement the Partnership entered into with Oasis Petroleum in connection with the closing of our initial public offering, Oasis Petroleum agreed to indemnify the Partnership for any losses resulting from this litigation. However, the Partnership cannot guarantee that such indemnity will fully protect the Partnership from the adverse consequences of any adverse ruling.

Equity-Based Compensation

Equity-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation	Equity-Based Compensation The Oasis Midstream Partners LP 2017 Long Term Incentive Plan (“LTIP”) provides for the grant, at the discretion of the Board of Directors of the General Partner, of options, unit appreciation rights, restricted units, phantom units, and other unit or cash-based awards. The purpose of awards under the LTIP is to provide additional incentive compensation to individuals providing services to the Partnership, and to align the economic interests of such individuals with the interests of the Partnership’s unitholders. As of September 30, 2018 , the aggregate number of common units that may be issued pursuant to any and all awards under the LTIP is equal to 1,980,118 common units, subject to adjustment due to recapitalization or reorganization, or related to forfeitures or expiration of awards, as provided under the LTIP. On January 1 of each calendar year following the adoption and prior to the expiration of the LTIP, the total number of common units that may be issued pursuant to the LTIP automatically increases by a number of common units equal to one percent of the number of common units outstanding on a fully diluted basis as of the close of business on the immediately preceding December 31 (calculated by adding to the number of common units outstanding, all outstanding securities convertible into common units on such date on an as converted basis). As a result of this adjustment, an additional 137,618 common units were reserved for issuance pursuant to awards under the LTIP on January 1, 2018 . Phantom unit awards. On October 19, 2017 , the Partnership granted under its LTIP 101,500 phantom unit awards (collectively the “Phantom Units” and each a “Phantom Unit”) to certain employees of Oasis Petroleum who are non-employees of the Partnership. Each Phantom Unit represents the right to receive a cash payment equal to the fair market value of one common unit on the day prior to the date it vests. Award recipients are also entitled to Distribution Equivalent Rights, which represent the right to receive a cash payment equal to the value of the distributions paid on one common unit between the grant date and the vesting date. The Phantom Units vest in equal amounts each year over a three -year period. The Phantom Units are accounted for as liability-classified awards since the awards will settle in cash. Under the fair value method for liability-classified awards, compensation expense is remeasured each reporting period at fair value based upon the closing price of a publicly traded common unit. Oasis Petroleum will reimburse the Partnership for the cash settlement amount of these awards. The Partnership recognizes in its Condensed Consolidated Balance Sheets the compensation expense associated with these awards in accounts receivable from Oasis Petroleum and accrued liabilities. As of September 30, 2018 , unrecognized equity-based compensation expense for all outstanding Phantom Units was $1.4 million , which is expected to be recognized over a weighted average period of 2.16 years. The following table summarizes information related to the Phantom Units held by certain non-employees of the Partnership: Phantom Units Non-vested units outstanding at December 31, 2017 99,100 Granted — Vested — Forfeited (9,600 ) Non-vested units outstanding at September 30, 2018 89,500 Restricted unit awards. The Partnership has granted to independent directors of the General Partner restricted unit awards under its LTIP, which vest over a one -year period. These awards are accounted for as equity-classified awards since the awards will settle in common units upon vesting. Under the fair value method for equity-classified awards, equity-based compensation expense is measured at the grant date based on the fair value of the award and is recognized over the vesting period. During the nine months ended September 30, 2018 , the Partnership granted 17,260 restricted unit awards which vest over a one -year period with a weighted-average grant date fair value of $17.55 per common unit. Equity-based compensation expense recorded for restricted unit awards for the three and nine months ended September 30, 2018 was approximately $0.1 million and $0.3 million , respectively. Equity-based compensation expense is included in general and administrative expenses on the Condensed Consolidated Statements of Operations. As of September 30, 2018 , unrecognized equity-based compensation expense for all outstanding restricted unit awards was $0.2 million , which is expected to be recognized over a weighted average period of 0.54 years. The following table summarizes information related to restricted units held by certain directors of the General Partner: Restricted Units Non-vested units outstanding at December 31, 2017 11,766 Granted 17,260 Vested (11,766 ) Forfeited — Non-vested units outstanding at September 30, 2018 17,260 Restricted stock awards (Predecessor). Prior to the initial public offering on September 25, 2017 , certain employees of Oasis Petroleum were granted restricted stock awards under its Amended and Restated 2010 Long Term Incentive Plan, the majority of which vest over a three -year period. Oasis Petroleum accounts for these awards as equity-classified awards, in accordance with GAAP. The value of restricted stock grants is based on the closing sales price of Oasis Petroleum’s common stock on the date of grant, and compensation expense is recognized ratably over the requisite service period. During the nine months ended September 30, 2017 , employees of the Predecessor were granted restricted stock awards equal to 91,550 shares of common stock with a $14.95 weighted average grant date fair value per share. In accordance with its indirect shared service expense allocation from Oasis Petroleum, the Predecessor recorded equity-based compensation expense associated with these awards of approximately $0.3 million and $1.0 million for the three and nine months ended September 30, 2017 , respectively, in general and administrative expenses on the Condensed Consolidated Statements of Operations. There is no unrecognized expense associated with these awards for the Partnership.

Partnership Equity and Distribu

Partnership Equity and Distributions	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Partnership Equity and Distributions	Partnership Equity and Distributions Cash distributions. On October 30, 2018 , the Board of Directors of the General Partner declared the quarterly cash distribution for the third quarter of 2018 of $0.4300 per unit. The distribution will be payable on November 27, 2018 to unitholders of record as of November 9, 2018 . The following table details the distributions paid in respect of each period in which the distributions were earned: Distributions Limited Partners General Partner Period Record Date Distribution Date Distribution per limited partner unit Common units Subordinated units IDRs (In thousands, except per unit data) Q3 2017 (1) February 16, 2018 February 26, 2018 $ 0.0245 $ 337 $ 337 $ — Q4 2017 February 16, 2018 February 26, 2018 0.3750 5,161 5,156 — Q1 2018 May 17, 2018 May 29, 2018 0.3925 5,406 5,397 — Q2 2018 August 16, 2018 August 28, 2018 0.4100 5,649 5,638 — Q3 2018 (2) November 9, 2018 November 27, 2018 0.4300 5,925 5,913 — __________________ (1) Distribution prorated from the closing of the Partnership’s initial public offering on September 25, 2017. (2) The cash distribution for the three months ended September 30, 2018 was determined based upon the number of units outstanding at November 1, 2018 . Minimum quarterly distribution. The partnership agreement requires that all of the Partnership’s available cash be distributed quarterly. Under the current cash distribution policy, the Partnership intends to distribute to the holders of common units and subordinated units on a quarterly basis at least the minimum quarterly distribution of $0.3750 per unit, or $1.50 on an annualized basis, to the extent the Partnership has sufficient cash after establishment of cash reserves and payment of fees and expenses, including payments to the General Partner and its affiliates. Subordinated units. Oasis Petroleum owns all of the Partnership’s subordinated units. The partnership agreement provides that, during the subordination period, the common units have the right to receive distributions of available cash from operating surplus each quarter in an amount equal to the minimum quarterly distribution, plus any arrearages in the payment of the minimum quarterly distribution on the common units from prior quarters, before any distributions of available cash from operating surplus may be made on the subordinated units. No arrearages will accrue or be payable on the subordinated units. When the subordination period ends, each outstanding subordinated unit will convert into one common unit and will thereafter participate pro rata with the other common units in distributions of available cash. The subordination period will end on December 31, 2020 if each of the following tests are met: • for each of the three consecutive, non-overlapping four-quarter periods immediately preceding that date, aggregate distributions from operating surplus equaled or exceeded the sum of the minimum quarterly distribution multiplied by the total number of common units and subordinated units outstanding in each quarter in each period; • for the same three consecutive, non-overlapping four-quarter periods, the “adjusted operating surplus” (as defined in the partnership agreement) equaled or exceeded the sum of the minimum quarterly distribution multiplied by the total number of common units and subordinated units outstanding during each quarter on a fully diluted weighted average basis; and • there are no arrearages in payment of the minimum quarterly distribution on the common units. Notwithstanding the foregoing, the subordination period will automatically terminate, and all of the subordinated units will convert into common units on a one-for-one basis, on the first business day after the distribution to unitholders in respect of any quarter, beginning with the quarter ending December 31, 2018, if each of the following has occurred: • for one four-quarter period immediately preceding that date, aggregate distributions from operating surplus exceeded 150.0% of the minimum quarterly distribution multiplied by the total number of common units and subordinated units outstanding in each quarter in the period; • for the same four-quarter period, the “adjusted operating surplus” (as defined in the Partnership’s Amended and Restated Agreement of Limited Partnership) equaled or exceeded 150.0% of the sum of the minimum quarterly distribution multiplied by the total number of common units and subordinated units outstanding during each quarter on a fully diluted weighted average basis, plus the related distribution on the IDRs; and • there are no arrearages in payment of the minimum quarterly distributions on the common units. Incentive distribution rights. The General Partner owns all of the Partnership’s IDRs, which will entitle it to increasing percentages, up to a maximum of 50.0% , of the cash the Partnership distributes in excess of $0.43125 per unit per quarter. The maximum distribution of 50.0% does not include any distributions that Oasis Petroleum may receive on common units or subordinated units that it owns. No distributions have been declared on the IDRs since the Partnership’s initial public offering. Percentage allocations of available cash from operating surplus. For any quarter in which the Partnership has distributed cash from operating surplus to the common and subordinated unitholders in an amount equal to the minimum distribution, the Partnership will distribute any additional available cash from operating surplus for that quarter among the unitholders and the IDR holders in the following manner: Marginal Percentage Interest in Distributions Total Quarterly Distribution Per Unit Unitholders IDR Holders Minimum Quarterly Distribution up to $0.3750 100 % — % First Target Distribution above $0.3750 up to $0.4313 100 % — % Second Target Distribution above $0.4313 up to $0.4688 85 % 15 % Third Target Distribution above $0.4688 up to $0.5625 75 % 25 % Thereafter above $0.5625 50 % 50 %

Net Income Per Limited Partner

Net Income Per Limited Partner Unit	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income Per Limited Partner Unit	Earnings Per Limited Partner Unit Earnings per limited partner unit is computed by dividing the respective limited partners’ interest in earnings attributable to the Partnership by the weighted average number of common units and subordinated units outstanding. Because there is more than one class of participating securities, the Partnership uses the two-class method when calculating earnings per limited partner unit. The classes of participating securities include common units, subordinated units, and IDRs. Diluted earnings per limited partner unit reflects the potential dilution that could occur if securities or agreements to issue common units, such as awards under the LTIP, were exercised, settled or converted into common units. When it is determined that potential common units should be included in diluted net income per limited partner unit calculation, the impact is reflected by applying the treasury stock method. Three Months Ended September 30, 2018 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared $ — $ 5,925 $ 5,913 $ 11,838 Undistributed earnings attributable to Oasis Midstream Partners LP — 269 269 538 Net income attributable to Oasis Midstream Partners LP $ — $ 6,194 $ 6,182 $ 12,376 Weighted average limited partner units outstanding Basic 13,751 Diluted 13,769 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 0.45 Diluted 0.45 Anti-dilutive restricted units 8 Three Months Ended September 30, 2017 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared (1) $ — $ 337 $ 337 $ 674 Excess distributions attributable to Oasis Midstream Partners LP — (71 ) (77 ) (148 ) Net income attributable to Oasis Midstream Partners LP $ — $ 266 $ 260 $ 526 Weighted average limited partner units outstanding Basic 12,625 Diluted 12,625 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 0.02 Diluted 0.02 Anti-dilutive restricted units 12 ___________________ (1) On February 2, 2018, the Board of Directors of the General Partner declared the quarterly cash distribution for the third quarter of 2017 of $0.0245 per unit for the six days ended September 30, 2017. The cash distribution for the third quarter of 2017 was prorated from the closing of the initial public offering on September 25, 2017. Nine Months Ended September 30, 2018 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared $ — $ 16,980 $ 16,948 $ 33,928 Undistributed earnings attributable to Oasis Midstream Partners LP — 423 423 846 Net income attributable to Oasis Midstream Partners LP $ — $ 17,403 $ 17,371 $ 34,774 Weighted average limited partner units outstanding Basic 13,750 Diluted 13,764 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 1.27 Diluted 1.26 Anti-dilutive restricted units 8 Nine Months Ended September 30, 2017 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared (1) $ — $ 337 $ 337 $ 674 Excess distributions attributable to Oasis Midstream Partners LP — (71 ) (77 ) (148 ) Net income attributable to Oasis Midstream Partners LP $ — $ 266 $ 260 $ 526 Weighted average limited partner units outstanding Basic 12,625 Diluted 12,625 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 0.02 Diluted 0.02 Anti-dilutive restricted units 12 ___________________ (1) On February 2, 2018, the Board of Directors of the General Partner declared the quarterly cash distribution for the third quarter of 2017 of $0.0245 per unit for the six days ended September 30, 2017. The cash distribution for the third quarter of 2017 was prorated from the closing of the initial public offering on September 25, 2017.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Presentation	Presentation The accompanying condensed consolidated financial statements of the Partnership have not been audited by the Partnership’s independent registered public accounting firm, except that the Condensed Consolidated Balance Sheet at December 31, 2017 is derived from audited financial statements. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for fair statement of the Partnership’s financial position have been included. Management has made certain estimates and assumptions that affect reported amounts in the condensed consolidated financial statements and disclosures of contingencies. Actual results may differ from those estimates. The results for interim periods are not necessarily indicative of annual results. These interim financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain disclosures have been condensed or omitted from these financial statements. Accordingly, they do not include all of the information and notes required by accounting principles generally accepted in the United States of America (“GAAP”) for complete consolidated financial statements and should be read in conjunction with the Partnership’s audited consolidated financial statements and notes thereto included in the Partnership’s Annual Report on Form 10-K for the year ended December 31, 2017 (“ 2017 Annual Report”).
Consolidation	Consolidation The Partnership’s condensed consolidated financial statements include its accounts and the accounts of the DevCos. With respect to Bobcat DevCo and Beartooth DevCo, management has determined that OMS’s equity at risk was established with non-substantive voting rights, making Bobcat DevCo and Beartooth DevCo variable interest entities (“VIEs”) under the rules of the Financial Accounting Standards Board (“FASB”). Through its 100% ownership interest in OMP Operating LLC (“OMP Operating”), which owns controlling interests in Bobcat DevCo and Beartooth DevCo, the Partnership has the authority to direct the activities that most significantly affect the economic performance of these entities and the obligation to absorb losses or the right to receive benefits that could be potentially significant to them. Therefore, the Partnership is considered the primary beneficiary of Bobcat DevCo and Beartooth DevCo and is required to consolidate these entities in its financial statements under the VIE consolidation model. With respect to Bighorn DevCo, the Partnership is required to consolidate Bighorn DevCo under the voting interest consolidation model because Bighorn DevCo is an indirect wholly owned subsidiary of the Partnership.
Non-controlling Interests	Non-Controlling Interests The non-controlling interests represent Oasis Petroleum’s retained ownership interest in Bobcat DevCo and Beartooth DevCo of 90% and 60% , respectively.
Revenue from contracts with customers	Revenue recognition. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2014-09, R evenue from Contracts with Customers (“ASU 2014-09”), which uses a five-step model to recognize revenue from customer contracts. ASU 2014-09 was applied on a modified retrospective basis. The adoption of ASU 2014-09 did not result in a material impact to the Partnership’s financial position, cash flows or results of operations. Disclosures in accordance with the requirements of ASU 2014-09 have been provided in Note 3 . Revenue from contracts with customers The unit of account in ASC 606 is a performance obligation, which is a promise in a contract to transfer to a customer either a distinct good or service (or bundle of goods or services) or a series of distinct goods or services provided over a period of time. ASC 606 requires that a contract’s transaction price, which is the amount of consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, is to be allocated to each performance obligation in the contract based on relative standalone selling prices and recognized as revenue when (point in time) or as (over time) the performance obligation is satisfied. Crude oil and natural gas revenues. The Partnership is party to certain contracts for crude oil gathering, stabilization, blending, storage and transportation, as well as natural gas gathering, compression, processing and gas lift services. Under these customer contracts, the Partnership has a series of performance obligations to provide daily integrated midstream services on a stand ready basis over a period of time. This represents a single performance obligation since the customer simultaneously receives and consumes the benefits of these services on a daily basis. Satisfaction of the performance obligation is measured as each day of service is completed, which directly corresponds with its right to consideration from the customer. Revenues associated with these contracts are recognized based upon the transaction price at month-end under the right to invoice practical expedient. Payments are typically due from customers 30 days after receipt of invoice. Water revenues. The Partnership is also party to certain contracts with customers for water services, which includes produced and flowback water gathering and disposal services and freshwater supply and distribution services. Under its customer contracts for produced and flowback water services, the Partnership has a series of performance obligations to provide daily integrated midstream services on a stand ready basis over a period of time. This represents a single performance obligation since the customer simultaneously receives and consumes the benefits of these services on a daily basis. Satisfaction of the performance obligation is measured as each day of service is completed, which directly corresponds with its right to consideration from the customer. Revenues associated with these contracts are recognized based upon the transaction price at month-end under the right to invoice practical expedient. Payments are typically due from customers 30 days after receipt of invoice. Under its customer contracts for freshwater supply and distribution services, the Partnership supplies and distributes freshwater to its customers for hydraulic fracturing and production optimization. These contracts contain multiple distinct performance obligations since each freshwater barrel can be sold separately and is not dependent or highly interrelated with other barrels. Revenue associated with freshwater supply and distribution services is recognized at a point in time based upon the transaction price when title, control and risk of loss transfers to the customer, which occurs at the delivery point. Payments are due from customers 30 days after receipt of invoice.
Statement of Cash Flows	Statement of cash flows. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2016-15, Statement of Cash Flows (“ASU 2016-15”), which is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. ASU 2016-15 was applied on a retrospective basis. The adoption of ASU 2016-15 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures.
Business Combinations	Business combinations. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2017-01, Clarifying the Definition of a Business (“ASU 2017-01”), which provides guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. ASU 2017-01 was adopted on a prospective basis. The adoption of ASU 2017-01 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures.
Equity-based Compensation	Equity-based compensation. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2017-09, Scope of Modification Accounting (“ASU 2017-09”), which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. ASU 2017-09 was adopted on a prospective basis. The adoption of ASU 2017-09 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Leases. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (“ASU 2016-02”), which requires a lessee to recognize lease payment obligations and a corresponding right-of-use asset to be measured at fair value on the balance sheet. ASU 2016-02 also requires certain qualitative and quantitative disclosures about the amount, timing and uncertainty of cash flows arising from leases. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those years. In January 2018, the FASB issued Accounting Standards Update No. 2018-01, Land easement practical expedient for transition to Topic 842 , which provides an optional transition practical expedient to not evaluate under Topic 842 existing or expired land easements that were not previously accounted for as leases under Topic 840, Leases . The Partnership plans to elect this practical expedient. In July 2018, the FASB issued Accounting Standards Update No. 2018-11, Targeted Improvements - Lease Topic 842 , which allows entities another option for transition and also provides lessors with a practical expedient to combine lease and non-lease components. The Partnership will adopt the new leases standard using the required modified retrospective approach and plans to elect the option to recognize a cumulative effect adjustment of initially applying the guidance to the opening balance of retained earnings in the period of adoption, rather than recognizing in the earliest period presented. Prior period amounts will not be adjusted. The Partnership is in the process of analyzing its lease arrangements and is continuing to identify and put in place necessary changes to its business processes and controls to support the adoption of the new standard, including implementing a new lease accounting software to assess the portfolio of leases, assist in the quantification of the expected impact on the consolidated financial statements and facilitate the calculations of the related accounting entries and disclosures. The Partnership is currently evaluating the effect that adopting the new lease guidance will have on its financial position, cash flows and results of operations.

Organization and Nature of Op_2

Organization and Nature of Operations (Tables)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Ownership Interests in DevCos	In connection with the Partnership’s initial public offering on September 25, 2017 , Oasis Petroleum contributed to the Partnership ownership interests in the following DevCos: DevCos Areas Served Service Lines Oasis Midstream Ownership Bighorn DevCo Wild Basin – Gas processing – Crude stabilization – Crude blending – Crude and NGL storage – Crude transportation 100% Bobcat DevCo Wild Basin – Gas gathering – Gas compression – Gas lift – Crude gathering – Produced and flowback water gathering – Produced and flowback water disposal 10% Beartooth DevCo Alger – Produced and flowback water gathering – Produced and flowback water disposal – Freshwater supply and distribution 40%

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table summarizes revenues associated with contracts with customers for crude oil, natural gas and water services for the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Crude oil and natural gas services revenue $ 34,347 $ 22,419 $ 98,489 $ 59,798 Water services revenue 37,120 24,962 100,957 65,535 Total revenues $ 71,467 $ 47,381 $ 199,446 $ 125,333

Transactions with Affiliates (T

Transactions with Affiliates (Tables)	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Schedule of Related Party Operating Expenses	General and administrative expenses and interest expense incurred from affiliate transactions with Oasis Petroleum include the following for the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Expenses from affiliates General and administrative $ 4,490 $ 2,895 $ 15,320 $ 8,416 Interest expense, net of capitalized interest — 2,714 — 6,945

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	The following table sets forth the Partnership’s accrued liabilities for the periods presented: September 30, 2018 December 31, 2017 (In thousands) Accrued capital costs $ 43,323 $ 47,843 Accrued operating expenses 16,007 10,860 Other accrued liabilities 43 115 Total accrued liabilities $ 59,373 $ 58,818

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	The following table sets forth the Partnership’s property, plant and equipment for the periods presented: September 30, 2018 December 31, 2017 (In thousands) Pipelines $ 364,199 $ 255,231 Natural gas processing plant 112,563 102,371 Produced and flowback water facilities 92,646 80,050 Compressor stations 95,972 59,293 Other property and equipment 33,737 32,340 Construction in progress 177,417 124,643 Total property, plant and equipment 876,534 653,928 Less: accumulated depreciation and amortization (54,555 ) (34,348 ) Total property, plant and equipment, net $ 821,979 $ 619,580

Long-Term Debt (Tables)

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Applicable Margins Under Revolving Credit Facility	The applicable margin for borrowings under the Revolving Credit Facility is determined in accordance with the Credit Agreement as follows: Consolidated Total Leverage Ratio Applicable Margin for Eurodollar Loans Applicable Margin for ABR Loans Commitment Fee Rate Less than or equal to 3.00 to 1.00 1.75 % 0.75 % 0.375 % Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 2.00 % 1.00 % 0.375 % Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 2.25 % 1.25 % 0.500 % Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 2.50 % 1.50 % 0.500 % Greater than 4.50 to 1.00 2.75 % 1.75 % 0.500 %

Equity-based Compensation (Tabl

Equity-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Phantom Units Held	The following table summarizes information related to the Phantom Units held by certain non-employees of the Partnership: Phantom Units Non-vested units outstanding at December 31, 2017 99,100 Granted — Vested — Forfeited (9,600 ) Non-vested units outstanding at September 30, 2018 89,500
Schedule of Restricted Award Activity	The following table summarizes information related to restricted units held by certain directors of the General Partner: Restricted Units Non-vested units outstanding at December 31, 2017 11,766 Granted 17,260 Vested (11,766 ) Forfeited — Non-vested units outstanding at September 30, 2018 17,260

Partnership Equity and Distri_2

Partnership Equity and Distributions (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Schedule of Percentage Allocations of Available Cash from Operating Surplus	For any quarter in which the Partnership has distributed cash from operating surplus to the common and subordinated unitholders in an amount equal to the minimum distribution, the Partnership will distribute any additional available cash from operating surplus for that quarter among the unitholders and the IDR holders in the following manner: Marginal Percentage Interest in Distributions Total Quarterly Distribution Per Unit Unitholders IDR Holders Minimum Quarterly Distribution up to $0.3750 100 % — % First Target Distribution above $0.3750 up to $0.4313 100 % — % Second Target Distribution above $0.4313 up to $0.4688 85 % 15 % Third Target Distribution above $0.4688 up to $0.5625 75 % 25 % Thereafter above $0.5625 50 % 50 % The following table details the distributions paid in respect of each period in which the distributions were earned: Distributions Limited Partners General Partner Period Record Date Distribution Date Distribution per limited partner unit Common units Subordinated units IDRs (In thousands, except per unit data) Q3 2017 (1) February 16, 2018 February 26, 2018 $ 0.0245 $ 337 $ 337 $ — Q4 2017 February 16, 2018 February 26, 2018 0.3750 5,161 5,156 — Q1 2018 May 17, 2018 May 29, 2018 0.3925 5,406 5,397 — Q2 2018 August 16, 2018 August 28, 2018 0.4100 5,649 5,638 — Q3 2018 (2) November 9, 2018 November 27, 2018 0.4300 5,925 5,913 — __________________ (1) Distribution prorated from the closing of the Partnership’s initial public offering on September 25, 2017. (2) The cash distribution for the three months ended September 30, 2018 was determined based upon the number of units outstanding at November 1, 2018 .

Net Income Per Limited Partne_2

Net Income Per Limited Partner Unit (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Net Income per Limited Partner Unit	Three Months Ended September 30, 2018 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared $ — $ 5,925 $ 5,913 $ 11,838 Undistributed earnings attributable to Oasis Midstream Partners LP — 269 269 538 Net income attributable to Oasis Midstream Partners LP $ — $ 6,194 $ 6,182 $ 12,376 Weighted average limited partner units outstanding Basic 13,751 Diluted 13,769 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 0.45 Diluted 0.45 Anti-dilutive restricted units 8 Three Months Ended September 30, 2017 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared (1) $ — $ 337 $ 337 $ 674 Excess distributions attributable to Oasis Midstream Partners LP — (71 ) (77 ) (148 ) Net income attributable to Oasis Midstream Partners LP $ — $ 266 $ 260 $ 526 Weighted average limited partner units outstanding Basic 12,625 Diluted 12,625 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 0.02 Diluted 0.02 Anti-dilutive restricted units 12 ___________________ (1) On February 2, 2018, the Board of Directors of the General Partner declared the quarterly cash distribution for the third quarter of 2017 of $0.0245 per unit for the six days ended September 30, 2017. The cash distribution for the third quarter of 2017 was prorated from the closing of the initial public offering on September 25, 2017. Nine Months Ended September 30, 2018 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared $ — $ 16,980 $ 16,948 $ 33,928 Undistributed earnings attributable to Oasis Midstream Partners LP — 423 423 846 Net income attributable to Oasis Midstream Partners LP $ — $ 17,403 $ 17,371 $ 34,774 Weighted average limited partner units outstanding Basic 13,750 Diluted 13,764 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 1.27 Diluted 1.26 Anti-dilutive restricted units 8 Nine Months Ended September 30, 2017 General Partner Limited Partners IDRs Common units Subordinated units Total (In thousands, except per unit data) Net income attributable to Oasis Midstream Partners LP: Distribution declared (1) $ — $ 337 $ 337 $ 674 Excess distributions attributable to Oasis Midstream Partners LP — (71 ) (77 ) (148 ) Net income attributable to Oasis Midstream Partners LP $ — $ 266 $ 260 $ 526 Weighted average limited partner units outstanding Basic 12,625 Diluted 12,625 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic $ 0.02 Diluted 0.02 Anti-dilutive restricted units 12 ___________________ (1) On February 2, 2018, the Board of Directors of the General Partner declared the quarterly cash distribution for the third quarter of 2017 of $0.0245 per unit for the six days ended September 30, 2017. The cash distribution for the third quarter of 2017 was prorated from the closing of the initial public offering on September 25, 2017.

Organization and Nature of Op_3

Organization and Nature of Operations (Details) a in Thousands	Sep. 25, 2017shares	Sep. 30, 2018aarea
Limited Partners' Capital Account [Line Items]
Number of primary areas with developed infrastructure | area		2
Bighorn DevCo [Member]
Limited Partners' Capital Account [Line Items]
Ownership interest (percent)	100.00%
Bobcat DevCo [Member]
Limited Partners' Capital Account [Line Items]
Ownership interest (percent)	10.00%
Beartooth DevCo [Member]
Limited Partners' Capital Account [Line Items]
Ownership interest (percent)	40.00%
Wild Basin [Member] | Oil, Gas and Water Services [Member]
Limited Partners' Capital Account [Line Items]
Gross dedicated acreage received from Oasis (acres)		65
Wild Basin [Member] | Fresh Water [Member]
Limited Partners' Capital Account [Line Items]
Gross dedicated acreage received from Oasis (acres)		364
Wild Basin [Member] | Produced Water [Member]
Limited Partners' Capital Account [Line Items]
Gross dedicated acreage received from Oasis (acres)		581
Oasis Petroleum [Member] | Common Units [Member]
Limited Partners' Capital Account [Line Items]
Common units sold in public offering (shares) | shares	5,125,000
Oasis Petroleum [Member] | Subordinated Units [Member]
Limited Partners' Capital Account [Line Items]
Common units sold in public offering (shares) | shares	13,750,000
Oasis Petroleum [Member] | Wild Basin [Member] | Oil, Gas and Water Services [Member]
Limited Partners' Capital Account [Line Items]
Dedicated acreage still within Oasis' gross operated acreage position (acres)		29
Oasis Petroleum [Member] | Wild Basin [Member] | Fresh Water [Member]
Limited Partners' Capital Account [Line Items]
Dedicated acreage still within Oasis' gross operated acreage position (acres)		203
Oasis Petroleum [Member] | Wild Basin [Member] | Produced Water [Member]
Limited Partners' Capital Account [Line Items]
Dedicated acreage still within Oasis' gross operated acreage position (acres)		299

Basis of Presentation (Details)

Basis of Presentation (Details)	Sep. 25, 2017	Sep. 30, 2018
Bobcat DevCo [Member]
Variable Interest Entity [Line Items]
Ownership interest (percent)	10.00%
Beartooth DevCo [Member]
Variable Interest Entity [Line Items]
Ownership interest (percent)	40.00%
Oasis Midstream Partners, LP [Member] | OMP Operating, LLC [Member]
Variable Interest Entity [Line Items]
Ownership interest (percent)		100.00%
Oasis Petroleum [Member] | Bobcat DevCo [Member]
Variable Interest Entity [Line Items]
Non-controlling interest (percent)		90.00%
Oasis Petroleum [Member] | Beartooth DevCo [Member]
Variable Interest Entity [Line Items]
Non-controlling interest (percent)		60.00%

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 71,467	$ 47,381	$ 199,446	$ 125,333
Crude Oil and Natural Gas Services [Member]
Disaggregation of Revenue [Line Items]
Total revenues	34,347	22,419	98,489	59,798
Water Services [Member]
Disaggregation of Revenue [Line Items]
Total revenues	$ 37,120	$ 24,962	$ 100,957	$ 65,535

Transactions with Affiliates (D

Transactions with Affiliates (Details) - Oasis [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
General and administrative	$ 4,490	$ 2,895	$ 15,320	$ 8,416
Interest expense, net of capitalized interest	$ 0	$ 2,714	$ 0	$ 6,945
Commercial Agreements with OPNA, Oasis Petroleum Marketing LLC (“OPM”) and OMS [Member]
Related Party Transaction [Line Items]
Term of contractual arrangements			15 years
Centralized Corporate, General and Administrative Services [Member] | Commercial Agreements with OPNA, Oasis Petroleum Marketing LLC (“OPM”) and OMS [Member]
Related Party Transaction [Line Items]
Term of contractual arrangements			15 years

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued capital costs	$ 43,323	$ 47,843
Accrued operating expenses	16,007	10,860
Other accrued liabilities	43	115
Total accrued liabilities	$ 59,373	$ 58,818

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 876,534	$ 653,928
Less: accumulated depreciation and amortization	(54,555)	(34,348)
Total property, plant and equipment, net	821,979	619,580
Pipelines [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	364,199	255,231
Natural Gas Processing Plant [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	112,563	102,371
Produced and Flowback Water Facilities [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	92,646	80,050
Compressor Stations [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	95,972	59,293
Other Property and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	33,737	32,340
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 177,417	$ 124,643

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details)	9 Months Ended
	Sep. 30, 2018USD ($)	Aug. 27, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 25, 2017USD ($)
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 166,000,000		$ 78,000,000
Maximum consolidated senior secured leverage ratio	3.75
Covenant Period One [Member]
Line of Credit Facility [Line Items]
Maximum consolidated total leverage ratio	4.50
Minimum consolidated interest coverage ratio	3
Covenant Period Two [Member]
Line of Credit Facility [Line Items]
Maximum consolidated total leverage ratio	5
Minimum consolidated interest coverage ratio	2.50
Covenant Period Three [Member]
Line of Credit Facility [Line Items]
Maximum consolidated total leverage ratio	5.25
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowing capacity increase limit		$ 400,000,000
Minimum aggregate principal amount threshold under covenant	$ 150,000,000
ABR Loans [Member] | Revolving Credit Facility [Member] | Federal Funds Effective Rate [Member]
Line of Credit Facility [Line Items]
Spread on variable rate (percent)	0.50%
ABR Loans [Member] | Revolving Credit Facility [Member] | Adjusted LIBOR [Member]
Line of Credit Facility [Line Items]
Spread on variable rate (percent)	1.00%
The Credit Agreement [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum aggregate commitment amount		$ 250,000,000		$ 200,000,000
Borrowings outstanding	$ 166,000,000
Weighted average interest rate (percent)	4.00%
The Credit Agreement [Member] | Letters of Credit [Member]
Line of Credit Facility [Line Items]
Maximum aggregate commitment amount				10,000,000
The Credit Agreement [Member] | Swingline Loans [Member]
Line of Credit Facility [Line Items]
Maximum aggregate commitment amount				$ 10,000,000

Long-Term Debt - Applicable Mar

Long-Term Debt - Applicable Margins Under Revolving Credit Facility (Details)	9 Months Ended
	Sep. 30, 2018
Less than or equal to 3.00 to 1.00 | Maximum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	3
Less than or equal to 3.00 to 1.00 | OMP Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Commitment fee rate (percent)	0.375%
Less than or equal to 3.00 to 1.00 | OMP Revolving Line of Credit [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	1.75%
Less than or equal to 3.00 to 1.00 | OMP Revolving Line of Credit [Member] | Alternate Based Rate (ABR) [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	0.75%
Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 | Maximum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	3.50
Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 | Minimum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	3
Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 | OMP Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Commitment fee rate (percent)	0.375%
Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 | OMP Revolving Line of Credit [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	2.00%
Greater than 3.00 to 1.00 but less than or equal to 3.50 to 1.00 | OMP Revolving Line of Credit [Member] | Alternate Based Rate (ABR) [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	1.00%
Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 | Maximum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	4
Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 | Minimum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	3.50
Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 | OMP Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Commitment fee rate (percent)	0.50%
Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 | OMP Revolving Line of Credit [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	2.25%
Greater than 3.50 to 1.00 but less than or equal to 4.00 to 1.00 | OMP Revolving Line of Credit [Member] | Alternate Based Rate (ABR) [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	1.25%
Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 | Maximum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	4.50
Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 | Minimum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	4
Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 | OMP Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Commitment fee rate (percent)	0.50%
Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 | OMP Revolving Line of Credit [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	2.50%
Greater than 4.00 to 1.00 but less than or equal to 4.50 to 1.00 | OMP Revolving Line of Credit [Member] | Alternate Based Rate (ABR) [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	1.50%
Greater than 4.50 to 1.00 | Minimum [Member]
Debt Instrument [Line Items]
Consolidated total leverage ratio	4.50
Greater than 4.50 to 1.00 | OMP Revolving Line of Credit [Member]
Debt Instrument [Line Items]
Commitment fee rate (percent)	0.50%
Greater than 4.50 to 1.00 | OMP Revolving Line of Credit [Member] | Eurodollar [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	2.75%
Greater than 4.50 to 1.00 | OMP Revolving Line of Credit [Member] | Alternate Based Rate (ABR) [Member]
Debt Instrument [Line Items]
Applicable margin (percent)	1.75%

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Holiday [Line Items]
Tax provision	$ 0	$ 7,898,000	$ 0	$ 22,858,000
Predecessor [Member]
Income Tax Holiday [Line Items]
Effective tax rate (percent)		35.20%		36.80%

Commitments and Contingencies (

Commitments and Contingencies (Details) bbl in Millions, $ in Millions	Mar. 23, 2017USD ($)	Sep. 30, 2018USD ($)bbl
Mirada Litigation [Member]
Loss Contingencies [Line Items]
Monetary damages sought (in excess of)	$ 100
Water Volume Commitment Agreements [Member]
Loss Contingencies [Line Items]
Minimum quantity to be delivered (barrels) | bbl		16.3
Term of contractual arrangements		10 years
Estimable future commitments under volume commitment agreements		$ 10.9

Equity-Based Compensation (Deta

Equity-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2018	Oct. 19, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 25, 2017
Long Term Incentive Plan (LTIP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional number of shares reserved for issuance (shares)	1,980,118
Annual increase in number of common units authorized for issuance as a percentage of units outstanding (percent)			1.00%		1.00%
Aggregate number of common units that may be issued (shares)			137,618		137,618
Phantom Units [Member] | Long Term Incentive Plan (LTIP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)					0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period (shares)	99,100				99,100
Granted (shares)					0
Vested (shares)					0
Forfeited (shares)					(9,600)
Outstanding at end of period (shares)			89,500		89,500
Restricted Unit Awards [Member] | Long Term Incentive Plan (LTIP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 0.2		$ 0.2
Weighted average recognition period					6 months 15 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period (shares)	11,766				11,766
Vested (shares)					(11,766)
Forfeited (shares)					0
Outstanding at end of period (shares)			17,260		17,260
Predecessor [Member] | Restricted Stock [Member] | Long Term Incentive Plan (LTIP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)						91,550
Vesting period of granted awards							3 years
Weighted average grant date per share (in dollars per share)						$ 14.95
Stock-based compensation expense				$ 0.3		$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (shares)						91,550
Oasis Midstream Partners, LP [Member] | Phantom Units [Member] | Long Term Incentive Plan (LTIP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)		101,500
Vesting period of granted awards		3 years
Unrecognized compensation cost			$ 1.4		$ 1.4
Weighted average recognition period					2 years 1 month 29 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (shares)		101,500
OMP General Partner LLC [Member] | Restricted Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)					17,260
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted (shares)					17,260
OMP General Partner LLC [Member] | Restricted Unit Awards [Member] | Long Term Incentive Plan (LTIP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					1 year
Weighted average grant date per share (in dollars per share)					$ 17.55
Stock-based compensation expense			$ 0.1		$ 0.3

Partnership Equity and Distri_3

Partnership Equity and Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended					6 Months Ended	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Distribution Made to Limited Partner [Line Items]
Cash distributions declared per limited partner unit (in usd per share)	$ 0.43	$ 0.41	$ 0.3925	$ 0.375	$ 0.0245
Distribution	$ 11,838				$ 674		$ 33,928	$ 674
IDR holders [Member]
Distribution Made to Limited Partner [Line Items]
Distribution	$ 0	$ 0	$ 0	$ 0	0		$ 0	0
Cash Distribution [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)	$ 0.3750
Partners annualized distribution (in dollars per share)							$ 1.50
Termination threshold as percentage of sum of minimum distribution multiplied by total number of units outstanding (percent)						150.00%	50.00%
Basis for General Partners' interest in distributions (in dollars per share)							$ 0.43125
Cash Distribution [Member] | Target Distribution up to $0.375 [Member] | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.375
Cash Distribution [Member] | Target Distribution above $0.375 up to $0.4313 [Member] | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.375
Cash Distribution [Member] | Target Distribution above $0.375 up to $0.4313 [Member] | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.4313
Cash Distribution [Member] | Target Distribution above $0.4313 up to $0.4688 [Member] | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.4313
Cash Distribution [Member] | Target Distribution above $0.4313 up to $0.4688 [Member] | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.4688
Cash Distribution [Member] | Target Distribution above $$0.4688 up to 0.5625 [Member] | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.4688
Cash Distribution [Member] | Target Distribution above $$0.4688 up to 0.5625 [Member] | Maximum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							0.5625
Cash Distribution [Member] | Target Distribution above $0.5625 [Member] | Minimum [Member]
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)							$ 0.5625
Cash Distribution [Member] | Unitholders [Member] | Target Distribution up to $0.375 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	100.00%						100.00%
Cash Distribution [Member] | Unitholders [Member] | Target Distribution above $0.375 up to $0.4313 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	100.00%						100.00%
Cash Distribution [Member] | Unitholders [Member] | Target Distribution above $0.4313 up to $0.4688 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	85.00%						85.00%
Cash Distribution [Member] | Unitholders [Member] | Target Distribution above $$0.4688 up to 0.5625 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	75.00%						75.00%
Cash Distribution [Member] | Unitholders [Member] | Target Distribution above $0.5625 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	50.00%						50.00%
Cash Distribution [Member] | IDR holders [Member] | Target Distribution up to $0.375 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	0.00%						0.00%
Cash Distribution [Member] | IDR holders [Member] | Target Distribution above $0.375 up to $0.4313 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	0.00%						0.00%
Cash Distribution [Member] | IDR holders [Member] | Target Distribution above $0.4313 up to $0.4688 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	15.00%						15.00%
Cash Distribution [Member] | IDR holders [Member] | Target Distribution above $$0.4688 up to 0.5625 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	25.00%						25.00%
Cash Distribution [Member] | IDR holders [Member] | Target Distribution above $0.5625 [Member]
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)	50.00%						50.00%
Common Units [Member] | Unitholders [Member]
Distribution Made to Limited Partner [Line Items]
Distribution	$ 5,925	5,649	5,406	5,161	337		$ 16,980	337
Subordinated Units [Member] | Unitholders [Member]
Distribution Made to Limited Partner [Line Items]
Distribution	$ 5,913	$ 5,638	$ 5,397	$ 5,156	$ 337		$ 16,948	$ 337

Net Income Per Limited Partne_3

Net Income Per Limited Partner Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Sep. 30, 2017	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared		$ 11,838				$ 674	$ 33,928	$ 674
Undistributed earnings attributable to Oasis Midstream Partners LP		538					846
Excess distributions attributable to Oasis Midstream Partners LP						(148)		(148)
Earnings attributable to Oasis Midstream Partners LP	$ 526	$ 12,376				$ 526	$ 34,774	526
Net income attributable to Oasis Midstream Partners LP per limited partner unit
Cash distributions declared per limited partner unit (in usd per share)		$ 0.43	$ 0.41	$ 0.3925	$ 0.375	$ 0.0245
Common Units [Member]
Weighted average units outstanding:
Weighted average number of limited partner units outstanding (Basic) (shares)	12,625	13,751					13,750
Net income attributable to Oasis Midstream Partners LP per limited partner unit
Net income per limited partner unit (basic) subsequent to the Offering (in dollars per share)	$ 0.02	$ 0.45					$ 1.27
Subordinated Units [Member]
Weighted average units outstanding:
Weighted average number of limited partner units outstanding (Diluted) (shares)	12,625	13,769					13,764
Net income attributable to Oasis Midstream Partners LP per limited partner unit
Net income per limited partner unit (diluted) subsequent to the Offering (in dollars per share)	$ 0.02	$ 0.45					$ 1.26
General Partner [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	0
Undistributed earnings attributable to Oasis Midstream Partners LP		0					0
Excess distributions attributable to Oasis Midstream Partners LP						0		0
Earnings attributable to Oasis Midstream Partners LP		0				0	0	0
Limited Partner [Member] | Common Units [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared		5,925	5,649	5,406	5,161	337	16,980	337
Undistributed earnings attributable to Oasis Midstream Partners LP		269					423
Excess distributions attributable to Oasis Midstream Partners LP						(71)		(71)
Earnings attributable to Oasis Midstream Partners LP		$ 6,194				$ 266	$ 17,403	$ 266
Weighted average units outstanding:
Weighted average number of limited partner units outstanding (Basic) (shares)		13,751				12,625	13,750	12,625
Weighted average number of limited partner units outstanding (Diluted) (shares)		13,769				12,625	13,764	12,625
Net income attributable to Oasis Midstream Partners LP per limited partner unit
Net income per limited partner unit (basic) subsequent to the Offering (in dollars per share)		$ 0.45				$ 0.02	$ 1.27	$ 0.02
Net income per limited partner unit (diluted) subsequent to the Offering (in dollars per share)		$ 0.45				$ 0.02	$ 1.26	$ 0.02
Anti-dilutive restricted units (shares)		8				12	8	12
Limited Partner [Member] | Subordinated Units [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared		$ 5,913	$ 5,638	$ 5,397	$ 5,156	$ 337	$ 16,948	$ 337
Undistributed earnings attributable to Oasis Midstream Partners LP		269					423
Excess distributions attributable to Oasis Midstream Partners LP						(77)		(77)
Earnings attributable to Oasis Midstream Partners LP		$ 6,182				$ 260	$ 17,371	$ 260