Oasis Midstream Partners (OMP) 10-Q 8 Aug 19 2019 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2019	Jul. 31, 2019
Document Information - Document and Entity Information[Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-38212
Entity Registrant Name	Oasis Midstream Partners LP
Entity Incorporation State	DE
Entity Tax Identification Number	47-1208855
Entity Address, Address Line One	1001 Fannin Street
Entity Address, Address Line Two	Suite 1500
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77002
City Area Code	281
Local Phone Number	404-9500
Title of 12(b) Security	Common units representing limited partner interests
Trading Symbol	OMP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001652133
Current Fiscal Year End Date	--12-31
Common Units
Document Information - Document and Entity Information[Line Items]
Entity Common Stock, Shares Outstanding		20,045,196
Subordinated Units
Document Information - Document and Entity Information[Line Items]
Entity Common Stock, Shares Outstanding		13,750,000

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 6,246	$ 6,649
Accounts receivable	6,010	2,481
Accounts receivable - Oasis Petroleum	80,088	80,805
Prepaid expenses	1,267	1,418
Other current assets	0	22
Total current assets	93,611	91,375
Property, plant and equipment	1,060,379	933,155
Less: accumulated depreciation and amortization	(80,160)	(62,730)
Total property, plant and equipment, net	980,219	870,425
Operating lease right-of-use assets	3,642	0
Other assets	3,385	2,452
Total assets	1,080,857	964,252
Current liabilities
Accounts payable	1,522	2,180
Accounts payable - Oasis Petroleum	34,873	33,014
Accrued liabilities	56,930	57,657
Accrued interest payable	293	442
Current operating lease liabilities	2,051
Other current liabilities	610	0
Total current liabilities	96,279	93,293
Long-term debt	408,000	318,000
Asset retirement obligations	1,564	1,514
Operating lease liabilities	1,597	0
Other liabilities	553	0
Total liabilities	507,993	412,807
Commitments and contingencies
Equity
General Partner	491	112
Total partners’ equity	257,733	238,630
Non-controlling interests	315,131	312,815
Total equity	572,864	551,445
Total liabilities and equity	1,080,857	964,252
Common Units
Equity
Limited partners	205,009	192,581
Subordinated Units
Equity
Limited partners	$ 52,233	$ 45,937

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) - Parenthetical - shares	Jun. 30, 2019	Dec. 31, 2018
Common Units
Units issued (shares)	20,045,196	20,029,026
Units outstanding (shares)	20,045,196	20,029,026
Subordinated Units
Units issued (shares)	13,750,000	13,750,000
Units outstanding (shares)	13,750,000	13,750,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues
Total revenues	$ 97,644	$ 66,558	$ 189,295	$ 127,979
Operating expenses
Costs of product sales	12,022	1,641	20,087	2,761
Operating and maintenance	16,003	14,693	34,853	30,689
Depreciation and amortization	8,562	6,659	17,491	13,023
General and administrative	7,809	5,897	16,529	12,047
Total operating expenses	44,396	28,890	88,960	58,520
Operating income	53,248	37,668	100,335	69,459
Interest expense, net of capitalized interest	(4,209)	(183)	(7,957)	(445)
Other expense	(4)	0	(4)	0
Total other expense	(4,213)	(183)	(7,961)	(445)
Net income	49,035	37,485	92,374	69,014
Less: Net income attributable to non-controlling interests	22,837	25,041	44,633	46,616
Net income attributable to Oasis Midstream Partners LP	$ 26,198	$ 12,444	$ 47,741	$ 22,398
Common Units
Earnings per limited partner unit (Note 12)
Earnings per limited partner unit, Common units - Basic and diluted (in usd per share)	$ 0.76	$ 0.45	$ 1.39	$ 0.81
Weighted average number of limited partner units outstanding - Basic
Weighted average number of limited partner units outstanding (Basic) (shares)	20,024	13,750	20,020	13,750
Weighted average number of limited partner units outstanding - Diluted
Weighted average number of limited partner units outstanding (Diluted) (shares)	20,034	13,761	20,037	13,761
Service revenues
Revenues
Total revenues	$ 73,277	$ 61,378	$ 149,266	$ 119,301
Service revenues | Oasis Petroleum
Revenues
Total revenues	71,452	60,715	146,314	118,344
Service revenues | Third Parties
Revenues
Total revenues	1,825	663	2,952	957
Product revenues
Revenues
Total revenues	24,367	5,180	40,029	8,678
Product revenues | Oasis Petroleum
Revenues
Total revenues	24,348	3,909	40,000	7,393
Product revenues | Third Parties
Revenues
Total revenues	19	1,271	29	1,285
General Partner
Operating expenses
Net income	491
Net income attributable to Oasis Midstream Partners LP	491	0	729	0
Limited Partner
Operating expenses
Net income attributable to Oasis Midstream Partners LP	25,707	12,444	47,012	22,398
Limited Partner | Common Units
Operating expenses
Net income	15,241	6,222
Net income attributable to Oasis Midstream Partners LP	$ 15,245	$ 6,222	$ 27,880	$ 11,199
Earnings per limited partner unit (Note 12)
Earnings per limited partner unit, Common units - Basic and diluted (in usd per share)	$ 0.76	$ 0.45	$ 1.39	$ 0.81
Weighted average number of limited partner units outstanding - Basic
Weighted average number of limited partner units outstanding (Basic) (shares)	20,024	13,750	20,020	13,750
Weighted average number of limited partner units outstanding - Diluted
Weighted average number of limited partner units outstanding (Diluted) (shares)	20,034	13,761	20,037	13,761

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Total	Non-controlling Interests	UnitholdersCommon Units	UnitholdersSubordinated Units	General Partner
Beginning balance at Dec. 31, 2017	$ 560,020	$ 313,446	$ 167,401	$ 79,173	$ 0
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions from non-controlling interests	23,565	23,565
Distributions to non-controlling interests	(38,316)	(38,316)
Distributions to unitholders	(10,991)		(5,498)	(5,493)
Equity-based compensation	63		63
Net income	31,529	21,575	4,977	4,977
Ending balance at Mar. 31, 2018	565,870	320,270	166,943	78,657	0
Beginning balance at Dec. 31, 2017	560,020	313,446	167,401	79,173	0
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	69,014
Ending balance at Jun. 30, 2018	591,183	343,967	167,734	79,482	0
Beginning balance at Mar. 31, 2018	565,870	320,270	166,943	78,657	0
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions from non-controlling interests	16,097	16,097
Distributions to non-controlling interests	(17,441)	(17,441)
Distributions to unitholders	(10,803)		(5,406)	(5,397)
Equity-based compensation	103		103
Other	(128)		(128)
Net income	37,485	25,041	6,222	6,222
Ending balance at Jun. 30, 2018	591,183	343,967	167,734	79,482	0
Beginning balance at Dec. 31, 2018	551,445	312,815	192,581	45,937	112
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions from non-controlling interests	2,532	2,532
Distributions to non-controlling interests	(21,922)	(21,922)
Distributions to unitholders	(15,320)		(9,020)	(6,188)	(112)
Equity-based compensation	119		119
Other	(175)	(2,977)	2,881	(79)
Net income	43,339	21,796	12,630	8,675	238
Ending balance at Mar. 31, 2019	560,018	312,244	199,191	48,345	238
Beginning balance at Dec. 31, 2018	551,445	312,815	192,581	45,937	112
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	92,374
Ending balance at Jun. 30, 2019	572,864	315,131	205,009	52,233	491
Beginning balance at Mar. 31, 2019	560,018	312,244	199,191	48,345	238
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions from non-controlling interests	1,709	1,709
Distributions to non-controlling interests	(21,659)	(21,659)
Distributions to unitholders	(16,122)		(9,421)	(6,463)	(238)
Equity-based compensation	100		100
Other	(217)		(102)	(115)
Net income	49,035	22,837	15,241	10,466	491
Ending balance at Jun. 30, 2019	$ 572,864	$ 315,131	$ 205,009	$ 52,233	$ 491

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 92,374	$ 69,014
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17,491	13,023
Equity-based compensation expenses	219	166
Deferred financing costs amortization	417	104
Working capital and other changes:
Change in accounts receivable	(2,086)	29,407
Change in other current assets	0	(92)
Change in prepaid expenses	150	420
Change in accounts payable and accrued liabilities	3,927	4,105
Change in other assets and liabilities, net	(399)	0
Net cash provided by operating activities	112,093	116,147
Cash flows from investing activities:
Capital expenditures	(130,826)	(154,988)
Net cash used in investing activities	(130,826)	(154,988)
Cash flows from financing activities:
Capital contributions from non-controlling interests	4,241	31,258
Distributions to non-controlling interests	(43,581)	(55,757)
Distributions to unitholders	(31,442)	(21,794)
Deferred financing costs	(440)	0
Proceeds from revolving credit facility	95,000	113,000
Principal payments on revolving credit facility	(5,000)	(26,000)
Other	(448)	0
Net cash provided by financing activities	18,330	40,707
Increase (decrease) in cash and cash equivalents	(403)	1,866
Beginning of period	6,649	883
End of period	6,246	2,749
Supplemental non-cash transactions:
Change in accrued capital expenditures	(3,602)	(3,523)
Change in asset retirement obligations	49	118
Reimbursement of capital expenditures from Oasis Petroleum	$ 0	$ 8,404

Organization and Nature of Oper

Organization and Nature of Operations	6 Months Ended
	Jun. 30, 2019
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”) 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”). Bobcat DevCo and Beartooth DevCo are jointly-owned with Oasis Petroleum through its wholly-owned subsidiary Oasis Midstream Services LLC (“OMS”). As of June 30, 2019, the Partnership’s assets and ownership interests in the DevCos were as follows: DevCos Areas Served Service Lines Partnership Ownership Bighorn DevCo Wild Basin – Natural gas processing – Crude oil stabilization – Crude oil blending – Crude oil and natural gas liquids storage – Crude oil transportation 100.0% Bobcat DevCo Wild Basin – Natural gas gathering – Natural gas compression – Gas lift – Crude oil gathering – Produced and flowback water gathering – Produced and flowback water disposal 32.5% Beartooth DevCo Alger – Produced and flowback water gathering – Produced and flowback water disposal – Freshwater supply and distribution 70.0% Nature of business. The Partnership generates the majority 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, gas lift and natural gas liquids (“NGL”) storage services; (ii) crude oil 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 natural gas, crude oil, produced and flowback water and freshwater that flows through the Partnership’s systems. The Partnership’s operations are supported by significant acreage dedications from Oasis Petroleum. In addition, the Partnership is party to a number of third party agreements across all three DevCos in which the Partnership has the right to provide its full suite of midstream services to support existing and future third party volumes.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of 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, 2018 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, 2018 (“2018 Annual Report”). Consolidation The Partnership’s condensed consolidated financial statements include its accounts and the accounts of the DevCos, each of which is controlled by OMP GP LLC (the “General Partner”). All intercompany balances and transactions have been eliminated upon consolidation. Variable interest entity (“VIE”). On November 19, 2018, the Partnership completed its acquisition of an additional 15% ownership interest in Bobcat DevCo and an additional 30% ownership interest in Beartooth DevCo. The Partnership determined its acquisition of additional ownership interests in Bobcat DevCo and Beartooth DevCo was a reconsideration event in accordance with the rules of the Financial Accounting Standards Board (“FASB”) for VIEs and completed a reassessment of its prior conclusions that Bobcat DevCo and Beartooth DevCo were each VIEs. With respect to Bobcat DevCo, management determined that OMS’s equity at risk was established with non-substantive voting rights, making Bobcat DevCo a VIE under the rules of the FASB. Through its 100% ownership interest in OMP Operating LLC (“OMP Operating”), which owns a controlling interest in Bobcat DevCo, the Partnership has the authority to direct the activities that most significantly affect the economic performance of this entity and the obligation to absorb losses or the right to receive benefits that could be potentially significant. Therefore, the Partnership is considered the primary beneficiary of Bobcat DevCo and is required to consolidate this entity in its financial statements under the VIE consolidation model. The Partnership has determined that Bighorn DevCo and Beartooth DevCo are not VIEs due to OMP Operating’s 100% and 70% ownership interest in Bighorn DevCo and Beartooth DevCo, respectively, which is proportional to its voting rights through its controlling interests. The Partnership has a controlling financial interest in Bighorn DevCo and Beartooth DevCo, through its 100% ownership interest in OMP Operating, and is required to consolidate Bighorn DevCo and Beartooth DevCo in its financial statements under the voting interest consolidation model. Non-controlling interests. The non-controlling interests represent OMS’s retained ownership interests in Bobcat DevCo and Beartooth DevCo as of June 30, 2019 of 67.5% and 30%, respectively. Significant Accounting Policies There have been no material changes to the Partnership’s critical accounting policies and estimates from those disclosed in the 2018 Annual Report, other than as noted below. Leases. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) , which requires lessees to recognize a right-of-use (“ROU”) asset and related liability on the balance sheet for leases with durations greater than twelve months and also requires certain quantitative and qualitative disclosures about leasing arrangements. Accounting Standards Codification 842, Leases (“ASC 842”), was subsequently amended by various Accounting Standards Updates, which provided additional implementation guidance. The Partnership adopted the new standard as of January 1, 2019, using the required modified retrospective approach and elected 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. Prior period amounts were not adjusted. The Partnership elected the package of practical expedients under the transition guidance within the new standard, including the practical expedient to not reassess under the new standard any prior conclusions about lease identification, lease classification and initial direct costs; the use-of hindsight practical expedient; the practical expedient to not reassess the prior accounting treatment for existing or expired land easements; and the practical expedient pertaining to combining lease and non-lease components for all asset classes. In addition, the Partnership elected not to apply the recognition requirements of ASC 842 to short-term leases, and as such, recognition of lease payments for short-term leases are recognized in net income on a straight line basis. See Note 8 — Leases for the adoption impact and disclosures required by ASC 842.

Revenue Recognition

Revenue Recognition	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition Disaggregation of revenues The following table presents revenues associated with contracts with customers for the periods presented: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 (In thousands) Service revenues Crude oil and natural gas revenues $ 45,298 $ 32,729 $ 93,881 $ 64,142 Produced and flowback water revenues 27,979 28,649 55,385 55,159 Total service revenues 73,277 61,378 149,266 119,301 Product revenues Natural gas and NGL revenues 16,641 — 26,858 — Freshwater revenues 7,726 5,180 13,171 8,678 Total product revenues 24,367 5,180 40,029 8,678 Total revenues $ 97,644 $ 66,558 $ 189,295 $ 127,979 Prior period performance obligations The Partnership records revenue when the performance obligations under the terms of its customer contracts are satisfied. The Partnership measures the satisfaction of its performance obligations using the output method based upon the volume of crude oil, natural gas or water that flows through its systems. In certain cases, the Partnership is required to estimate these volumes during a reporting period and record any differences between the estimated volumes and actual volumes in the following reporting period. Such differences have historically not been significant. For the three and six months ended June 30, 2019 and 2018, revenue recognized related to performance obligations satisfied in prior reporting periods was not material. Contract balances Contract balances are the result of timing differences between revenue recognition, billings and cash collections. Contract liabilities are recorded for consideration received from customers primarily related to (i) temporary deficiency quantities under minimum volume commitments which are recognized as revenue when the customer makes up the volumes or the deficiency makeup period expires and (ii) aid in construction payments received from customers which are recognized as revenue over the expected period of future benefit. The Partnership does not recognize contract assets or contract liabilities under its customer contracts for which invoicing occurs once the Partnership’s performance obligations have been satisfied and payment is unconditional. No material contract balances were recorded in the condensed consolidated financial statements for the three and six months ended June 30, 2019 or for the three and six months ended June 30, 2018. Remaining performance obligations The following table presents estimated revenue allocated to remaining performance obligations for contracted revenues that are unsatisfied (or partially satisfied) as of June 30, 2019 : (In thousands) 2019 (excluding the six months ended June 30, 2019) $ 11,189 2020 24,183 2021 27,019 2022 19,244 2023 12,624 Thereafter 14,642 Total $ 108,901 The partially and wholly unsatisfied performance obligations presented in the table above are generally limited to customer contracts which have fixed pricing and fixed volume terms and conditions, which generally include customer contracts with minimum volume commitment payment obligations. The Partnership has elected practical expedients, pursuant to Accounting Standards Codification 606, Revenue from Contracts with Customers , to exclude from the presentation of remaining performance obligations: (i) contracts with index-based pricing or variable volume attributes in which such variable consideration is allocated entirely to a wholly unsatisfied performance

Transactions with Affiliates

Transactions with Affiliates	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Transactions with Affiliates	Transactions with Affiliates Revenues. The Partnership generates the majority of its revenues through 15-year, fee-based contractual arrangements with wholly-owned subsidiaries of Oasis Petroleum for midstream services as described in Note 1 — Organization and Nature of Operations. In addition, the Partnership sells the residue gas and NGLs recovered from its gas processing plants attributable to its third party natural gas purchase agreements to Oasis Petroleum to market and sell to non-affiliated purchasers. Expenses. Oasis Petroleum provides substantial labor and overhead support for the Partnership pursuant to a 15-year services and secondment agreement (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. The Partnership reimburses Oasis Petroleum for direct and allocated general and administrative expenses incurred by Oasis Petroleum for the provision of these services. The expenses of executive officers and non-executive employees of Oasis Petroleum are allocated to the Partnership based on the amount of time spent managing its business and operations. The Partnership’s general and administrative expenses include $7.0 million and $5.4 million from affiliate transactions with Oasis Petroleum for the three months ended June 30, 2019 and 2018, respectively, and include $14.8 million and $10.8 million from affiliate transactions with Oasis Petroleum for the six months ended June 30, 2019 and 2018, respectively. 2019 Capital Expenditures Arrangement. On February 22, 2019, the Partnership entered into a memorandum of understanding (the “MOU”) with Oasis Petroleum regarding the funding of Bobcat DevCo’s capital expenditures for the 2019 calendar year (the “2019 Capital Expenditures Arrangement”). Pursuant to the Amended and Restated Limited Liability Company Agreement of Bobcat DevCo LLC, as amended (the “First A&R Bobcat LLCA”), the Partnership and Oasis Petroleum are each required to make pro-rata capital contributions to Bobcat DevCo in accordance with their respective percentage ownership interests in Bobcat DevCo. Pursuant to the MOU, the Partnership agreed to make up to $80.0 million of capital expenditures to Bobcat DevCo that Oasis Petroleum would otherwise be required to contribute under the First A&R Bobcat LLCA. In connection with execution of the MOU, the Partnership and Oasis Petroleum amended the First A&R Bobcat LLCA and entered into the Second Amended and Restated Limited Liability Company Agreement of Bobcat DevCo LLC (the “Second A&R Bobcat LLCA”). The Second A&R Bobcat LLCA includes provisions applicable to the disproportionate capital contributions that the Partnership will make to Bobcat DevCo in connection with the 2019 Capital Expenditures Arrangement. Pursuant to the Second A&R Bobcat LLCA, upon the occurrence of a disproportionate capital contribution, the percentage interests of the Partnership and Oasis Petroleum in Bobcat DevCo will be adjusted to take into account the amount of the disproportionate capital contribution. During the three and six months ended June 30, 2019, the Partnership made capital contributions to Bobcat DevCo pursuant to the 2019 Capital Expenditures Arrangement of $35.8 million and $52.8 million, respectively. As a result, the Partnership’s ownership interest in Bobcat DevCo increased from 25% as of December 31, 2018 to 32.5% as of June 30, 2019.

Accrued Liabilities

Accrued Liabilities	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities Accrued liabilities consist of the following: June 30, 2019 December 31, 2018 (In thousands) Accrued capital costs $ 39,351 $ 42,953 Accrued operating expenses 16,145 13,539 Other accrued liabilities 1,434 1,165 Total accrued liabilities $ 56,930 $ 57,657

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment consists of the following: June 30, 2019 December 31, 2018 (In thousands) Pipelines $ 469,794 $ 395,087 Natural gas processing plants 291,960 278,680 Produced and flowback water facilities 95,582 95,119 Compressor stations 137,031 126,019 Other property and equipment 33,946 33,829 Construction in progress 32,066 4,422 Total property, plant and equipment 1,060,379 933,155 Less: accumulated depreciation and amortization (80,160) (62,730) Total property, plant and equipment, net $ 980,219 $ 870,425

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt The Partnership has a revolving credit facility with OMP Operating as borrower (the “Revolving Credit Facility”) which is available to fund working capital and to finance acquisitions and other capital expenditures of the Partnership. On May 6, 2019, the Partnership entered into an amendment to its Revolving Credit Facility to (i) increase the aggregate amount of commitments from $400.0 million to $475.0 million; (ii) provide for the ability to further increase commitments to $675.0 million; and (iii) add a new lender to the bank group. As of June 30, 2019, the aggregate amount of commitments under the Revolving Credit Facility were $475.0 million. The Revolving Credit Facility matures on September 25, 2022. At June 30, 2019, the Partnership had $408.0 million of borrowings outstanding under the Revolving Credit Facility, at a weighted average interest rate of 4.2%, and an $8.2 million outstanding letter of credit, resulting in an unused borrowing capacity of $58.8 million. The unused portion of the Revolving Credit Facility is subject to a commitment fee ranging from 0.375% to 0.500%. The fair value of the Revolving Credit Facility approximates book value since borrowings under the Revolving Credit Facility bear interest at rates which are tied to current market rates. The Partnership was in compliance with the financial covenants under the Revolving Credit Facility at June 30, 2019.

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases As discussed in Note 2 — Summary of Significant Accounting Policies, the Partnership adopted ASC 842 as of January 1, 2019 using the modified retrospective method, which resulted in the Partnership recognizing offsetting operating ROU assets and lease liabilities of $4.1 million. The Partnership did not have any finance leases as of the date of adoption. There was no impact to the opening equity balance as a result of the adoption of ASC 842. Prior period amounts were not adjusted and continue to be reported in accordance with previous guidance, Accounting Standards Codification 840 (“ASC 840”). In accordance with the adoption of ASC 842, management determines whether an arrangement is a lease at its inception. The Partnership’s operating and finance leases consist primarily of equipment and land easements. The Partnership considers renewal and termination options in determining the lease term used to establish its ROU assets and lease liabilities to the extent the Partnership is reasonably certain to exercise the renewal or termination. The Partnership’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. As most of the Partnership’s leases do not provide an implicit rate, the Partnership uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future lease payments. The Partnership has determined the respective incremental borrowing rates based upon the rate of interest that would have been paid on a collateralized basis over similar tenors to that of the leases. The following table sets forth the Partnership’s components of lease costs for the periods presented: Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 (In thousands) Operating lease costs $ 692 $ 1,787 Variable lease costs (1) 103 103 Short-term lease costs 95 95 Finance lease costs: Amortization of ROU assets 8 11 Interest on lease liabilities 6 8 Total lease costs $ 904 $ 2,004 __________________ (1) Based on payments made by the Partnership to lessors for the right to use an underlying asset that vary because of changes in circumstances occurring after the commencement date, other than the passage of time, such as property taxes, operating and maintenance costs. The operating lease costs disclosed above are included in operating and maintenance expenses on the Partnership’s Condensed Consolidated Statement of Operations. The finance lease costs for the amortization of ROU assets and the interest on lease liabilities disclosed above are included in depreciation and amortization and interest expense, net of capitalized interest, respectively, on the Partnership’s Condensed Consolidated Statements of Operations. As of June 30, 2019, maturities of the Partnership’s lease liabilities are as follows: Operating Leases Finance Leases (In thousands) 2019 (excluding the six months ended June 30, 2019) $ 1,080 $ 5 2020 2,160 21 2021 540 45 2022 — 45 2023 — 45 Thereafter — 684 Total future lease payments 3,780 845 Less: Imputed interest 132 285 Present value of future lease payments $ 3,648 $ 560 As of December 31, 2018, future minimum annual rental commitments under non-cancelable leases under ASC 840 were as follows: (In thousands) 2019 $ 736 2020 — 2021 — 2022 — 2023 — Thereafter — Total future minimum lease payments $ 736 Supplemental balance sheet information related to the Partnership’s leases are as follows: Balance Sheet Classification June 30, 2019 (In thousands) Assets Operating lease assets Operating lease right-of-use assets $ 3,642 Finance lease assets Other assets 643 Total lease assets $ 4,285 Liabilities Current Operating lease liabilities Current operating lease liabilities $ 2,051 Finance lease liabilities Other current liabilities 7 Long-term Operating lease liabilities Operating lease liabilities 1,597 Finance lease liabilities Other liabilities 553 Total lease liabilities $ 4,208 Supplemental cash flow information and non-cash transactions related to the Partnership’s leases are as follows: June 30, 2019 (In thousands) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,454 Operating cash flows from finance leases 8 Financing cash flows from finance leases 59 ROU assets obtained in exchange for lease obligations Operating leases $ 1,227 Finance leases 654 Weighted-average remaining lease term and discount rate for the Partnership’s leases are as follows: As of June 30, 2019 Operating Leases Weighted average remaining lease term 1.7 years Weighted average discount rate 4.3 % Finance Leases Weighted average remaining lease term 19.7 years Weighted average discount rate 4.3 %
Leases	Leases As discussed in Note 2 — Summary of Significant Accounting Policies, the Partnership adopted ASC 842 as of January 1, 2019 using the modified retrospective method, which resulted in the Partnership recognizing offsetting operating ROU assets and lease liabilities of $4.1 million. The Partnership did not have any finance leases as of the date of adoption. There was no impact to the opening equity balance as a result of the adoption of ASC 842. Prior period amounts were not adjusted and continue to be reported in accordance with previous guidance, Accounting Standards Codification 840 (“ASC 840”). In accordance with the adoption of ASC 842, management determines whether an arrangement is a lease at its inception. The Partnership’s operating and finance leases consist primarily of equipment and land easements. The Partnership considers renewal and termination options in determining the lease term used to establish its ROU assets and lease liabilities to the extent the Partnership is reasonably certain to exercise the renewal or termination. The Partnership’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. As most of the Partnership’s leases do not provide an implicit rate, the Partnership uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future lease payments. The Partnership has determined the respective incremental borrowing rates based upon the rate of interest that would have been paid on a collateralized basis over similar tenors to that of the leases. The following table sets forth the Partnership’s components of lease costs for the periods presented: Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 (In thousands) Operating lease costs $ 692 $ 1,787 Variable lease costs (1) 103 103 Short-term lease costs 95 95 Finance lease costs: Amortization of ROU assets 8 11 Interest on lease liabilities 6 8 Total lease costs $ 904 $ 2,004 __________________ (1) Based on payments made by the Partnership to lessors for the right to use an underlying asset that vary because of changes in circumstances occurring after the commencement date, other than the passage of time, such as property taxes, operating and maintenance costs. The operating lease costs disclosed above are included in operating and maintenance expenses on the Partnership’s Condensed Consolidated Statement of Operations. The finance lease costs for the amortization of ROU assets and the interest on lease liabilities disclosed above are included in depreciation and amortization and interest expense, net of capitalized interest, respectively, on the Partnership’s Condensed Consolidated Statements of Operations. As of June 30, 2019, maturities of the Partnership’s lease liabilities are as follows: Operating Leases Finance Leases (In thousands) 2019 (excluding the six months ended June 30, 2019) $ 1,080 $ 5 2020 2,160 21 2021 540 45 2022 — 45 2023 — 45 Thereafter — 684 Total future lease payments 3,780 845 Less: Imputed interest 132 285 Present value of future lease payments $ 3,648 $ 560 As of December 31, 2018, future minimum annual rental commitments under non-cancelable leases under ASC 840 were as follows: (In thousands) 2019 $ 736 2020 — 2021 — 2022 — 2023 — Thereafter — Total future minimum lease payments $ 736 Supplemental balance sheet information related to the Partnership’s leases are as follows: Balance Sheet Classification June 30, 2019 (In thousands) Assets Operating lease assets Operating lease right-of-use assets $ 3,642 Finance lease assets Other assets 643 Total lease assets $ 4,285 Liabilities Current Operating lease liabilities Current operating lease liabilities $ 2,051 Finance lease liabilities Other current liabilities 7 Long-term Operating lease liabilities Operating lease liabilities 1,597 Finance lease liabilities Other liabilities 553 Total lease liabilities $ 4,208 Supplemental cash flow information and non-cash transactions related to the Partnership’s leases are as follows: June 30, 2019 (In thousands) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,454 Operating cash flows from finance leases 8 Financing cash flows from finance leases 59 ROU assets obtained in exchange for lease obligations Operating leases $ 1,227 Finance leases 654 Weighted-average remaining lease term and discount rate for the Partnership’s leases are as follows: As of June 30, 2019 Operating Leases Weighted average remaining lease term 1.7 years Weighted average discount rate 4.3 % Finance Leases Weighted average remaining lease term 19.7 years Weighted average discount rate 4.3 %

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Partnership has various contractual obligations in the normal course of its operations. As of June 30, 2019, there have been no material changes to the Partnership’s future commitments as disclosed in Note 10 — Commitments and Contingencies in the Partnership’s 2018 Annual Report, except as noted below. Volume commitment agreements. As of June 30, 2019, the Partnership had certain agreements with an aggregate requirement to either deliver or purchase a minimum quantity of approximately 16.0 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 $10.3 million as of June 30, 2019. 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, Oasis Petroleum America LLC (“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. On July 2, 2019, Oasis Petroleum, OPNA, Oasis Midstream Services LLC, Oasis Midstream Partners LP, Bighorn DevCo LLC, Bobcat DevCo LLC and Beartooth DevCo LLC (collectively “Oasis Entities”) counterclaimed against Mirada for a judgment declaring that Oasis Entities are not obligated to purchase, manage, gather, transport, compress, process, market, sell or otherwise handle Mirada’s proportionate share of oil and gas produced from OPNA-operated wells. The counterclaim also seeks attorney’s fees, costs and expenses . 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 scheduled for February 2020. 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, financial condition and cash flows. 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 the 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	6 Months Ended
	Jun. 30, 2019
Share-based Payment Arrangement [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 June 30, 2019, the aggregate number of common units that may be issued pursuant to any and all awards under the LTIP is equal to 2,455,408 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). Phantom unit awards. In 2017, the Partnership granted under its LTIP 101,500 phantom unit awards 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 No phantom unit awards were granted under the LTIP during the six months ended June 30, 2019. Equity-based compensation expense related to phantom unit awards is recorded on the Condensed Consolidated Balance Sheets in accounts receivable from Oasis Petroleum, for the portion which will be reimbursed from Oasis Petroleum, and accrued liabilities, for the portion which will be owed to award holders. Equity-based compensation expense recorded on the Condensed Consolidated Balance Sheets related to phantom unit awards was $0.6 million and $0.1 million as of June 30, 2019 and December 31, 2018, respectively. As of June 30, 2019, unrecognized equity-based compensation expense for all outstanding phantom units was $0.8 million, which is expected to be recognized over a weighted average period of 1.4 years. Restricted unit awards. The Partnership has granted to independent directors of the General Partner restricted unit awards under the LTIP, which vest over a one one

Partnership Equity and Distribu

Partnership Equity and Distributions	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Partnership Equity and Distributions	Partnership Equity and Distributions Cash distributions. On August 6, 2019, the Board of Directors of the General Partner declared the quarterly cash distribution for the second quarter of 2019 of $0.49 per unit. In addition, the General Partner will receive a cash distribution of $0.5 million attributable to incentive distribution rights (“IDRs”) related to the earnings for the second quarter of 2019. These distributions will be payable on August 28, 2019, to unitholders of record as of August 16, 2019. The following table details the distributions paid in respect of each period in which the distributions were earned for the following periods: Distributions Limited Partners General Partner Period Record Date Distribution Date Distribution per limited partner unit Common units Subordinated units IDRs (In thousands) Q1 2018 May 17, 2018 May 29, 2018 $ 0.3925 $ 5,406 $ 5,397 $ — Q2 2018 August 16, 2018 August 28, 2018 0.41 5,649 5,638 — Q3 2018 November 9, 2018 November 27, 2018 0.43 5,925 5,913 — Q4 2018 February 15, 2019 February 28, 2019 0.45 9,020 6,188 112 Q1 2019 May 17, 2019 May 29, 2019 0.47 9,421 6,463 238 Q2 2019 August 16, 2019 August 28, 2019 0.49 9,822 6,738 491 __________________ (1) The cash distribution for the three months ended June 30, 2019 was determined based upon the number of units outstanding at July 31, 2019. 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% 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% 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 $0.4313 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. 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%

Earnings Per Limited Partner Un

Earnings Per Limited Partner Unit	6 Months Ended
	Jun. 30, 2019
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 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. There are no adjustments made to net income attributable to Oasis Midstream Partners LP in the calculation of diluted earnings per unit. Diluted weighted average limited partner units outstanding includes the dilutive effect of unvested restricted unit awards (see Note 10 — Equity-Based Compensation). The following table presents the calculation of earnings per limited partner unit under the two-class method: Three Months Ended June 30, 2019 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 $ 491 $ 9,822 $ 6,738 $ 17,051 Undistributed earnings attributable to Oasis Midstream Partners LP — 5,423 3,724 9,147 Net income attributable to Oasis Midstream Partners LP $ 491 $ 15,245 $ 10,462 $ 26,198 Weighted average limited partners units outstanding Basic 20,024 Diluted 20,034 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 0.76 Anti-dilutive restricted units 11 Six Months Ended June 30, 2019 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 $ 729 $ 19,243 $ 13,201 $ 33,173 Undistributed earnings attributable to Oasis Midstream Partners LP — 8,637 5,931 14,568 Net income attributable to Oasis Midstream Partners LP $ 729 $ 27,880 $ 19,132 $ 47,741 Weighted average limited partners units outstanding Basic 20,020 Diluted 20,037 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 1.39 Anti-dilutive restricted units 7 Three Months Ended June 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 $ — $ 5,649 $ 5,638 $ 11,287 Undistributed earnings attributable to Oasis Midstream Partners LP — 573 584 1,157 Net income attributable to Oasis Midstream Partners LP $ — $ 6,222 $ 6,222 $ 12,444 Weighted average limited partners units outstanding Basic 13,750 Diluted 13,761 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 0.45 Anti-dilutive restricted units 13 Six Months Ended June 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 $ — $ 11,056 $ 11,034 $ 22,090 Undistributed earnings attributable to Oasis Midstream Partners LP — 143 165 308 Net income attributable to Oasis Midstream Partners LP $ — $ 11,199 $ 11,199 $ 22,398 Weighted average limited partners units outstanding Basic 13,750 Diluted 13,761 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 0.81 Anti-dilutive restricted units 9

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of 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, 2018 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.
Consolidation	Consolidation The Partnership’s condensed consolidated financial statements include its accounts and the accounts of the DevCos, each of which is controlled by OMP GP LLC (the “General Partner”). All intercompany balances and transactions have been eliminated upon consolidation. Variable interest entity (“VIE”). On November 19, 2018, the Partnership completed its acquisition of an additional 15% ownership interest in Bobcat DevCo and an additional 30% ownership interest in Beartooth DevCo. The Partnership determined its acquisition of additional ownership interests in Bobcat DevCo and Beartooth DevCo was a reconsideration event in accordance with the rules of the Financial Accounting Standards Board (“FASB”) for VIEs and completed a reassessment of its prior conclusions that Bobcat DevCo and Beartooth DevCo were each VIEs. With respect to Bobcat DevCo, management determined that OMS’s equity at risk was established with non-substantive voting rights, making Bobcat DevCo a VIE under the rules of the FASB. Through its 100% ownership interest in OMP Operating LLC (“OMP Operating”), which owns a controlling interest in Bobcat DevCo, the Partnership has the authority to direct the activities that most significantly affect the economic performance of this entity and the obligation to absorb losses or the right to receive benefits that could be potentially significant. Therefore, the Partnership is considered the primary beneficiary of Bobcat DevCo and is required to consolidate this entity in its financial statements under the VIE consolidation model. The Partnership has determined that Bighorn DevCo and Beartooth DevCo are not VIEs due to OMP Operating’s 100% and 70% ownership interest in Bighorn DevCo and Beartooth DevCo, respectively, which is proportional to its voting rights through its controlling interests. The Partnership has a controlling financial interest in Bighorn DevCo and Beartooth DevCo, through its 100% ownership interest in OMP Operating, and is required to consolidate Bighorn DevCo and Beartooth DevCo in its financial statements under the voting interest consolidation model.
Non-controlling interests	Non-controlling interests. The non-controlling interests represent OMS’s retained ownership interests in Bobcat DevCo and Beartooth DevCo as of June 30, 2019 of 67.5% and 30%, respectively.
Significant Accounting Policies	Significant Accounting Policies There have been no material changes to the Partnership’s critical accounting policies and estimates from those disclosed in the 2018 Annual Report, other than as noted below. Leases. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) , which requires lessees to recognize a right-of-use (“ROU”) asset and related liability on the balance sheet for leases with durations greater than twelve months and also requires certain quantitative and qualitative disclosures about leasing arrangements. Accounting Standards Codification 842, Leases (“ASC 842”), was subsequently amended by various Accounting Standards Updates, which provided additional implementation guidance. The Partnership adopted the new standard as of January 1, 2019, using the required modified retrospective approach and elected 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. Prior period amounts were not adjusted. The Partnership elected the package of practical expedients under the transition guidance within the new standard, including the practical expedient to not reassess under the new standard any prior conclusions about lease identification, lease classification and initial direct costs; the use-of hindsight practical expedient; the practical expedient to not reassess the prior accounting treatment for existing or expired land easements; and the practical expedient pertaining to combining lease and non-lease components for all asset classes. In addition, the Partnership elected not to apply the recognition requirements of ASC 842 to short-term leases, and as such, recognition of lease payments for short-term leases are recognized in net income on a straight line basis. See Note 8 — Leases for the adoption impact and disclosures required by ASC 842.

Organization and Nature of Op_2

Organization and Nature of Operations (Tables)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Ownership Interests in DevCos	As of June 30, 2019, the Partnership’s assets and ownership interests in the DevCos were as follows: DevCos Areas Served Service Lines Partnership Ownership Bighorn DevCo Wild Basin – Natural gas processing – Crude oil stabilization – Crude oil blending – Crude oil and natural gas liquids storage – Crude oil transportation 100.0% Bobcat DevCo Wild Basin – Natural gas gathering – Natural gas compression – Gas lift – Crude oil gathering – Produced and flowback water gathering – Produced and flowback water disposal 32.5% Beartooth DevCo Alger – Produced and flowback water gathering – Produced and flowback water disposal – Freshwater supply and distribution 70.0%

Revenue Recognition (Tables)

Revenue Recognition (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents revenues associated with contracts with customers for the periods presented: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 (In thousands) Service revenues Crude oil and natural gas revenues $ 45,298 $ 32,729 $ 93,881 $ 64,142 Produced and flowback water revenues 27,979 28,649 55,385 55,159 Total service revenues 73,277 61,378 149,266 119,301 Product revenues Natural gas and NGL revenues 16,641 — 26,858 — Freshwater revenues 7,726 5,180 13,171 8,678 Total product revenues 24,367 5,180 40,029 8,678 Total revenues $ 97,644 $ 66,558 $ 189,295 $ 127,979
Estimated Timing of Remaining Performance Obligation	The following table presents estimated revenue allocated to remaining performance obligations for contracted revenues that are unsatisfied (or partially satisfied) as of June 30, 2019 : (In thousands) 2019 (excluding the six months ended June 30, 2019) $ 11,189 2020 24,183 2021 27,019 2022 19,244 2023 12,624 Thereafter 14,642 Total $ 108,901

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consist of the following: June 30, 2019 December 31, 2018 (In thousands) Accrued capital costs $ 39,351 $ 42,953 Accrued operating expenses 16,145 13,539 Other accrued liabilities 1,434 1,165 Total accrued liabilities $ 56,930 $ 57,657

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment consists of the following: June 30, 2019 December 31, 2018 (In thousands) Pipelines $ 469,794 $ 395,087 Natural gas processing plants 291,960 278,680 Produced and flowback water facilities 95,582 95,119 Compressor stations 137,031 126,019 Other property and equipment 33,946 33,829 Construction in progress 32,066 4,422 Total property, plant and equipment 1,060,379 933,155 Less: accumulated depreciation and amortization (80,160) (62,730) Total property, plant and equipment, net $ 980,219 $ 870,425

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Schedule of lease costs, supplemental cash flow information and non-cash transactions	The following table sets forth the Partnership’s components of lease costs for the periods presented: Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 (In thousands) Operating lease costs $ 692 $ 1,787 Variable lease costs (1) 103 103 Short-term lease costs 95 95 Finance lease costs: Amortization of ROU assets 8 11 Interest on lease liabilities 6 8 Total lease costs $ 904 $ 2,004 __________________ (1) Based on payments made by the Partnership to lessors for the right to use an underlying asset that vary because of changes in circumstances occurring after the commencement date, other than the passage of time, such as property taxes, operating and maintenance costs.
Maturities of the Partnership's lease liabilities	As of June 30, 2019, maturities of the Partnership’s lease liabilities are as follows: Operating Leases Finance Leases (In thousands) 2019 (excluding the six months ended June 30, 2019) $ 1,080 $ 5 2020 2,160 21 2021 540 45 2022 — 45 2023 — 45 Thereafter — 684 Total future lease payments 3,780 845 Less: Imputed interest 132 285 Present value of future lease payments $ 3,648 $ 560
Maturities of the Partnership's lease liabilities	As of June 30, 2019, maturities of the Partnership’s lease liabilities are as follows: Operating Leases Finance Leases (In thousands) 2019 (excluding the six months ended June 30, 2019) $ 1,080 $ 5 2020 2,160 21 2021 540 45 2022 — 45 2023 — 45 Thereafter — 684 Total future lease payments 3,780 845 Less: Imputed interest 132 285 Present value of future lease payments $ 3,648 $ 560
Schedule of future minimum rental commitments	As of December 31, 2018, future minimum annual rental commitments under non-cancelable leases under ASC 840 were as follows: (In thousands) 2019 $ 736 2020 — 2021 — 2022 — 2023 — Thereafter — Total future minimum lease payments $ 736
Schedule of supplemental balance sheet information	Supplemental balance sheet information related to the Partnership’s leases are as follows: Balance Sheet Classification June 30, 2019 (In thousands) Assets Operating lease assets Operating lease right-of-use assets $ 3,642 Finance lease assets Other assets 643 Total lease assets $ 4,285 Liabilities Current Operating lease liabilities Current operating lease liabilities $ 2,051 Finance lease liabilities Other current liabilities 7 Long-term Operating lease liabilities Operating lease liabilities 1,597 Finance lease liabilities Other liabilities 553 Total lease liabilities $ 4,208
Schedule of Supplemental Cash Flow Information	Supplemental cash flow information and non-cash transactions related to the Partnership’s leases are as follows: June 30, 2019 (In thousands) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,454 Operating cash flows from finance leases 8 Financing cash flows from finance leases 59 ROU assets obtained in exchange for lease obligations Operating leases $ 1,227 Finance leases 654
Schedule of Weighted Average Remaining Lease Term and Discount Rate	Weighted-average remaining lease term and discount rate for the Partnership’s leases are as follows: As of June 30, 2019 Operating Leases Weighted average remaining lease term 1.7 years Weighted average discount rate 4.3 % Finance Leases Weighted average remaining lease term 19.7 years Weighted average discount rate 4.3 %

Partnership Equity and Distri_2

Partnership Equity and Distributions (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Schedule of Percentage Allocations of Available Cash from Operating Surplus	The following table details the distributions paid in respect of each period in which the distributions were earned for the following periods: Distributions Limited Partners General Partner Period Record Date Distribution Date Distribution per limited partner unit Common units Subordinated units IDRs (In thousands) Q1 2018 May 17, 2018 May 29, 2018 $ 0.3925 $ 5,406 $ 5,397 $ — Q2 2018 August 16, 2018 August 28, 2018 0.41 5,649 5,638 — Q3 2018 November 9, 2018 November 27, 2018 0.43 5,925 5,913 — Q4 2018 February 15, 2019 February 28, 2019 0.45 9,020 6,188 112 Q1 2019 May 17, 2019 May 29, 2019 0.47 9,421 6,463 238 Q2 2019 August 16, 2019 August 28, 2019 0.49 9,822 6,738 491 __________________
Schedule of Target Partnership Unit Distribution Allocations	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%

Earnings Per Limited Partner _2

Earnings Per Limited Partner Unit (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Net Income per Limited Partner Unit	The following table presents the calculation of earnings per limited partner unit under the two-class method: Three Months Ended June 30, 2019 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 $ 491 $ 9,822 $ 6,738 $ 17,051 Undistributed earnings attributable to Oasis Midstream Partners LP — 5,423 3,724 9,147 Net income attributable to Oasis Midstream Partners LP $ 491 $ 15,245 $ 10,462 $ 26,198 Weighted average limited partners units outstanding Basic 20,024 Diluted 20,034 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 0.76 Anti-dilutive restricted units 11 Six Months Ended June 30, 2019 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 $ 729 $ 19,243 $ 13,201 $ 33,173 Undistributed earnings attributable to Oasis Midstream Partners LP — 8,637 5,931 14,568 Net income attributable to Oasis Midstream Partners LP $ 729 $ 27,880 $ 19,132 $ 47,741 Weighted average limited partners units outstanding Basic 20,020 Diluted 20,037 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 1.39 Anti-dilutive restricted units 7 Three Months Ended June 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 $ — $ 5,649 $ 5,638 $ 11,287 Undistributed earnings attributable to Oasis Midstream Partners LP — 573 584 1,157 Net income attributable to Oasis Midstream Partners LP $ — $ 6,222 $ 6,222 $ 12,444 Weighted average limited partners units outstanding Basic 13,750 Diluted 13,761 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 0.45 Anti-dilutive restricted units 13 Six Months Ended June 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 $ — $ 11,056 $ 11,034 $ 22,090 Undistributed earnings attributable to Oasis Midstream Partners LP — 143 165 308 Net income attributable to Oasis Midstream Partners LP $ — $ 11,199 $ 11,199 $ 22,398 Weighted average limited partners units outstanding Basic 13,750 Diluted 13,761 Net income attributable to Oasis Midstream Partners LP per limited partner unit Basic and diluted $ 0.81 Anti-dilutive restricted units 9

Organization and Nature of Op_3

Organization and Nature of Operations (Details)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2019
Oasis | Commercial Agreements with OPNA, Oasis Petroleum Marketing LLC (“OPM”) and OMS
Limited Partners' Capital Account [Line Items]
Term of contractual arrangements			15 years
Bighorn DevCo
Limited Partners' Capital Account [Line Items]
Ownership interest (percent)			100.00%
Bobcat DevCo | Oasis Midstream Partners, LP
Limited Partners' Capital Account [Line Items]
Ownership interest (percent)	32.50%	25.00%
Beartooth DevCo | Oasis Midstream Partners, LP
Limited Partners' Capital Account [Line Items]
Ownership interest (percent)			70.00%

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Basis of Presentation (Details)	Jun. 30, 2019	Dec. 31, 2018	Nov. 19, 2018	Jun. 30, 2019
Bighorn DevCo
Variable Interest Entity [Line Items]
Ownership interest (percent)				100.00%
Bobcat DevCo | Oasis Midstream Partners, LP
Variable Interest Entity [Line Items]
Ownership interest (percent)	32.50%	25.00%
Bobcat DevCo | OMS Holdings LLC (“OMS”)
Variable Interest Entity [Line Items]
Non-controlling interest (percent)	67.50%			67.50%
Beartooth DevCo | Oasis Midstream Partners, LP
Variable Interest Entity [Line Items]
Ownership interest (percent)				70.00%
Beartooth DevCo | OMS Holdings LLC (“OMS”)
Variable Interest Entity [Line Items]
Non-controlling interest (percent)	30.00%			30.00%
Bobcat DevCo | Oasis Midstream Partners, LP
Variable Interest Entity [Line Items]
Additional ownership interest acquired (percent)			15.00%
Beartooth DevCo | Oasis Midstream Partners, LP
Variable Interest Entity [Line Items]
Additional ownership interest acquired (percent)			30.00%

Revenue Recognition - Disaggreg

Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Timing of satisfaction of performance obligation			The partially and wholly unsatisfied performance obligations presented in the table above are generally limited to customer contracts which have fixed pricing and fixed volume terms and conditions, which generally include customer contracts with minimum volume commitment payment obligations. The Partnership has elected practical expedients, pursuant to Accounting Standards Codification 606, Revenue from Contracts with Customers, to exclude from the presentation of remaining performance obligations: (i) contracts with index-based pricing or variable volume attributes in which such variable consideration is allocated entirely to a wholly unsatisfied performance obligation or to a wholly unsatisfied promise to transfer a distinct service that forms part of a series of distinct services; (ii) contracts with an original expected duration of one year or less; and (iii) contracts for which the Partnership recognizes revenue under the right to invoice practical expedient.
Disaggregation of Revenue [Line Items]
Total revenues	$ 97,644	$ 66,558	$ 189,295	$ 127,979
Service revenues
Disaggregation of Revenue [Line Items]
Total revenues	73,277	61,378	149,266	119,301
Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	24,367	5,180	40,029	8,678
Crude oil and natural gas revenues | Service revenues
Disaggregation of Revenue [Line Items]
Total revenues	45,298	32,729	93,881	64,142
Produced and flowback water revenues | Service revenues
Disaggregation of Revenue [Line Items]
Total revenues	27,979	28,649	55,385	55,159
Natural gas and NGL revenues | Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	16,641	0	26,858	0
Freshwater revenues | Product revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 7,726	$ 5,180	$ 13,171	$ 8,678

Revenue Recognition - Estimated

Revenue Recognition - Estimated Timing of Remaining Performance Obligation (Details) $ in Thousands	Jun. 30, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 108,901
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 11,189
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 24,183
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 27,019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 19,244
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 12,624
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 14,642
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period

Transactions with Affiliates (D

Transactions with Affiliates (Details) - USD ($)	Jun. 30, 2019	Feb. 22, 2019	Dec. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Oasis
Related Party Transaction [Line Items]
General and administrative				$ 7,000,000	$ 5,400,000	$ 14,800,000	$ 10,800,000
Commercial Agreements with OPNA, Oasis Petroleum Marketing LLC (“OPM”) and OMS | Oasis
Related Party Transaction [Line Items]
Term of contractual arrangements						15 years
2019 Capital Expenditures Arrangement | Oasis
Related Party Transaction [Line Items]
Capital expenditures agreed to pursuant to the MOU		$ 80,000,000
Capital expenditures made				$ 35,800,000		$ 52,800,000
Centralized Corporate, General and Administrative Services | Commercial Agreements with OPNA, Oasis Petroleum Marketing LLC (“OPM”) and OMS | Oasis
Related Party Transaction [Line Items]
Term of contractual arrangements						15 years
Oasis Midstream Partners, LP | Bobcat DevCo
Related Party Transaction [Line Items]
Ownership interest (percent)	32.50%		25.00%

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued capital costs	$ 39,351	$ 42,953
Accrued operating expenses	16,145	13,539
Other accrued liabilities	1,434	1,165
Total accrued liabilities	$ 56,930	$ 57,657

Property, Plant and Equipment_2

Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,060,379	$ 933,155
Less: accumulated depreciation and amortization	(80,160)	(62,730)
Total property, plant and equipment, net	980,219	870,425
Pipelines
Property, Plant and Equipment [Line Items]
Property, plant and equipment	469,794	395,087
Natural gas processing plants
Property, Plant and Equipment [Line Items]
Property, plant and equipment	291,960	278,680
Produced and flowback water facilities
Property, Plant and Equipment [Line Items]
Property, plant and equipment	95,582	95,119
Compressor stations
Property, Plant and Equipment [Line Items]
Property, plant and equipment	137,031	126,019
Other property and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	33,946	33,829
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 32,066	$ 4,422

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - The Credit Agreement - Revolving Credit Facility - USD ($)	6 Months Ended
	Jun. 30, 2019	May 06, 2019	May 05, 2019
Line of Credit Facility [Line Items]
Maximum aggregate commitment amount	$ 475,000,000	$ 475,000,000	$ 400,000,000
Borrowing capacity increase limit	675,000,000
Borrowings outstanding	$ 408,000,000
Weighted average interest rate (percent)	4.20%
Unused borrowing capacity	$ 58,800,000
Letters of credit outstanding	$ 8,200,000
Minimum
Line of Credit Facility [Line Items]
Commitment fee rate (percent)	0.375%
Maximum
Line of Credit Facility [Line Items]
Commitment fee rate (percent)	0.50%

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	$ 3,642		$ 0
Operating lease liabilities	$ 3,648
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets		$ 4,100
Operating lease liabilities		$ 4,100

Leases - Schedule of lease cost

Leases - Schedule of lease costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease costs	$ 692	$ 1,787
Variable lease costs	103	103
Short-term lease costs	95	95
Amortization of ROU assets	8	11
Interest on lease liabilities	6	8
Total lease costs	$ 904	$ 2,004

Leases - Maturities of the Part

Leases - Maturities of the Partnership's lease liabilities (Details) $ in Thousands	Jun. 30, 2019USD ($)
Operating Leases
2019 (excluding the six months June 30, 2019)	$ 1,080
2020	2,160
2021	540
2022	0
2023	0
Thereafter	0
Total future lease payments	3,780
Less: Imputed interest	132
Present value of future lease payments	3,648
Finance Leases
2019 (excluding the six months ended June 30, 2019)	5
2020	21
2021	45
2022	45
2023	45
Thereafter	684
Total future lease payments	845
Less: Imputed interest	285
Present value of future lease payments	$ 560

Leases - Schedule of future min

Leases - Schedule of future minimum rental commitments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 736
2020	0
2021	0
2022	0
2023	0
Thereafter	0
Total future minimum lease payments	$ 736

Leases - Schedule of supplement

Leases - Schedule of supplemental balance sheet information (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease right-of-use assets	$ 3,642	$ 0
Finance lease assets	643
Total lease assets	4,285
Operating lease liabilities, current	2,051
Finance lease liabilities, current	7
Operating lease liabilities, long-term	1,597	$ 0
Finance lease liabilities, long-term	553
Total lease liabilities	$ 4,208

Leases - Schedule of lease co_2

Leases - Schedule of lease costs, supplemental cash flow information and non-cash transactions (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 1,454
Operating cash flows from finance leases	8
Financing cash flows from finance leases	59
ROU assets obtained in exchange for lease obligations, operating leases	1,227
ROU assets obtained in exchange for lease obligations, finance leases	$ 654

Leases - Schedule of weighted a

Leases - Schedule of weighted average remaining lease term and discount rates (Details)	Jun. 30, 2019
Leases [Abstract]
Operating leases - Weighted average remaining lease term	1 year 8 months 12 days
Operating leases - Weighted average discount rate (percent)	4.30%
Finance leases - Weighted average remaining lease term	19 years 8 months 12 days
Finance leases - Weighted average discount rate (percent)	4.30%

Commitments and Contingencies (

Commitments and Contingencies (Details) bbl in Millions	Mar. 23, 2017USD ($)	Jun. 30, 2019USD ($)bbl
Mirada Litigation
Loss Contingencies [Line Items]
Monetary damages sought (in excess of)	$ 100,000,000
Water Volume Commitment Agreements
Loss Contingencies [Line Items]
Minimum quantity to be delivered (barrels) | bbl		16
Purchase obligation		$ 10,300,000

Equity-Based Compensation (Deta

Equity-Based Compensation (Details) - Long Term Incentive Plan (LTIP) - USD ($) $ / shares in Units, $ in Millions	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional number of shares reserved for issuance (shares)	2,455,408
Annual increase in number of common units that may be issued (percent)	1.00%	1.00%		1.00%
Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)				0
Vesting period				3 years
Restricted Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)				16,170
Vesting period				1 year
Weighted average grant-date fair value (in usd per share)				$ 18.57
Stock-based compensation expense		$ 0.1	$ 0.1	$ 0.2	$ 0.2
Oasis Midstream Partners, LP | Phantom Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted (shares)						101,500
Equity based compensation cost	$ 0.6	0.6		0.6			$ 0.1
Unrecognized compensation cost	$ 0.8	$ 0.8		$ 0.8
Weighted average recognition period				1 year 4 months 24 days

Partnership Equity and Distri_3

Partnership Equity and Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 28, 2019	Aug. 06, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Distribution Made to Limited Partner [Line Items]
Distribution per limited partner unit (in dollars per share)			$ 0.49	$ 0.47	$ 0.45	$ 0.43	$ 0.41	$ 0.3925
Cash distribution declared			$ 17,051				$ 11,287		$ 33,173	$ 22,090
Partners annualized distribution (in dollars per share)									$ 1.50
General Partner
Distribution Made to Limited Partner [Line Items]
Cash distribution declared			$ 491	$ 238	$ 112	$ 0	0	$ 0	$ 729	0
Cash Distribution
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.3750
Termination threshold as percentage of sum of minimum distribution multiplied by total number of units outstanding (percent)									150.00%
Cash Distribution | General Partner
Distribution Made to Limited Partner [Line Items]
Termination threshold as percentage of sum of minimum distribution multiplied by total number of units outstanding (percent)									50.00%
Basis for General Partners' interest in distributions (in dollars per share)									$ 0.4313
Cash Distribution | Target Distribution up to $0.375 | Limited Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			100.00%						100.00%
Cash Distribution | Target Distribution up to $0.375 | General Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			0.00%						0.00%
Cash Distribution | Target Distribution up to $0.375 | Maximum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.3750
Cash Distribution | Target Distribution above $0.375 up to $0.4313 | Limited Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			100.00%						100.00%
Cash Distribution | Target Distribution above $0.375 up to $0.4313 | General Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			0.00%						0.00%
Cash Distribution | Target Distribution above $0.375 up to $0.4313 | Minimum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.3750
Cash Distribution | Target Distribution above $0.375 up to $0.4313 | Maximum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.4313
Cash Distribution | Target Distribution above $0.4313 up to $0.4688 | Limited Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			85.00%						85.00%
Cash Distribution | Target Distribution above $0.4313 up to $0.4688 | General Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			15.00%						15.00%
Cash Distribution | Target Distribution above $0.4313 up to $0.4688 | Minimum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.4313
Cash Distribution | Target Distribution above $0.4313 up to $0.4688 | Maximum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.4688
Cash Distribution | Target Distribution above $$0.4688 up to 0.5625 | Limited Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			75.00%						75.00%
Cash Distribution | Target Distribution above $$0.4688 up to 0.5625 | General Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			25.00%						25.00%
Cash Distribution | Target Distribution above $$0.4688 up to 0.5625 | Minimum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.4688
Cash Distribution | Target Distribution above $$0.4688 up to 0.5625 | Maximum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.5625
Cash Distribution | Target Distribution above $0.5625 | Limited Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			50.00%						50.00%
Cash Distribution | Target Distribution above $0.5625 | General Partner
Distribution Made to Limited Partner [Line Items]
Marginal percentage interest in distributions (percent)			50.00%						50.00%
Cash Distribution | Target Distribution above $0.5625 | Minimum
Distribution Made to Limited Partner [Line Items]
Partners quarterly distribution (in dollars per share)									$ 0.5625
Expected distribution
Distribution Made to Limited Partner [Line Items]
Cash distribution declared	$ 500
Common Units | Limited Partner
Distribution Made to Limited Partner [Line Items]
Cash distribution declared			$ 9,822	9,421	9,020	5,925	5,649	5,406	$ 19,243	11,056
Subordinated Units | Limited Partner
Distribution Made to Limited Partner [Line Items]
Cash distribution declared			$ 6,738	$ 6,463	$ 6,188	$ 5,913	$ 5,638	$ 5,397	$ 13,201	$ 11,034
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distribution per limited partner unit (in dollars per share)		$ 0.49

Earnings Per Limited Partner _3

Earnings Per Limited Partner Unit (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared	$ 17,051				$ 11,287		$ 33,173	$ 22,090
Undistributed earnings attributable to Oasis Midstream Partners LP	9,147				1,157		14,568	308
Net income attributable to Oasis Midstream Partners LP	26,198				12,444		47,741	22,398
General Partner
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared	491	$ 238	$ 112	$ 0	0	$ 0	729	0
Undistributed earnings attributable to Oasis Midstream Partners LP	0				0		0	0
Net income attributable to Oasis Midstream Partners LP	491				0		729	0
Limited Partner
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Oasis Midstream Partners LP	$ 25,707				$ 12,444		$ 47,012	$ 22,398
Common Units
Weighted average units outstanding:
Weighted average number of limited partner units outstanding (Basic) (shares)	20,024				13,750		20,020	13,750
Weighted average number of limited partner units outstanding (Diluted) (shares)	20,034				13,761		20,037	13,761
Net income attributable to Oasis Midstream Partners LP per limited partner unit
Earnings per limited partner unit, Common units - Basic and diluted (in usd per share)	$ 0.76				$ 0.45		$ 1.39	$ 0.81
Common Units | Limited Partner
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared	$ 9,822	9,421	9,020	5,925	$ 5,649	5,406	$ 19,243	$ 11,056
Undistributed earnings attributable to Oasis Midstream Partners LP	5,423				573		8,637	143
Net income attributable to Oasis Midstream Partners LP	$ 15,245				$ 6,222		$ 27,880	$ 11,199
Weighted average units outstanding:
Weighted average number of limited partner units outstanding (Basic) (shares)	20,024				13,750		20,020	13,750
Weighted average number of limited partner units outstanding (Diluted) (shares)	20,034				13,761		20,037	13,761
Net income attributable to Oasis Midstream Partners LP per limited partner unit
Earnings per limited partner unit, Common units - Basic and diluted (in usd per share)	$ 0.76				$ 0.45		$ 1.39	$ 0.81
Anti-dilutive restricted units (shares)	11				13		7	9
Subordinated Units | Limited Partner
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Distribution declared	$ 6,738	$ 6,463	$ 6,188	$ 5,913	$ 5,638	$ 5,397	$ 13,201	$ 11,034
Undistributed earnings attributable to Oasis Midstream Partners LP	3,724				584		5,931	165
Net income attributable to Oasis Midstream Partners LP	$ 10,462				$ 6,222		$ 19,132	$ 11,199