Summary of Significant Accounting Policies and Basis of Presentation | Summary of Significant Accounting Policies and Basis of Presentation Basis of Presentation The accompanying consolidated financial statements of the Partnership include the accounts of Oasis Midstream Partners LP and its subsidiaries. All intercompany transactions have been eliminated in consolidation. These statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). Certain reclassifications of prior year balances have been made to conform such amounts to current year classifications. These reclassifications have no impact on net income. Use of Estimates Preparation of the Partnership’s consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ significantly from those estimates. Management evaluates estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic and commodity price environment. Consolidation The Partnership’s 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 entities. In connection with the Partnership’s acquisition of additional ownership interest in both Bobcat DevCo and Beartooth DevCo on November 19, 2018 , the Partnership reassessed its prior conclusions of Bobcat DevCo and Beartooth DevCo as variable interest entities (“VIEs”). Based upon its reassessment, the Partnership determined Beartooth DevCo was no longer a VIE and consolidates into the Partnership’s financial statements under the voting interest consolidation model. With respect to Bobcat DevCo, management has determined that OMS’s equity at risk was established with non-substantive voting rights, making Bobcat DevCo a VIE under the rules of the Financial Accounting Standards Board (“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 Oasis Petroleum’s retained ownership interests, as of December 31, 2018 , in Bobcat DevCo and Beartooth DevCo of 75% and 30% , respectively. Significant Accounting Policies Revenue recognition. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers and a series of related accounting standards updates incorporated into GAAP as Accounting Standards Codification Topic 606 (“ASC 606”) using the modified retrospective method. The adoption of ASC 606 did not result in a material impact to the Partnership’s financial position, cash flows or results of operations. The Partnership has also modified current processes and controls to apply the requirements of the new standard and does not believe such modifications are material to its internal controls over financial reporting. Enhanced disclosures in accordance with the requirements of ASC 606 have been provided in Note 3 — Revenue Recognition . The unit of account in ASC 606 is a performance obligation, which is a promise in a contract to transfer to a customer either a distinct good or service (or bundle of goods or services) or a series of distinct goods or services provided over a period of time. ASC 606 requires that a contract’s transaction price, which is the amount of consideration to which an entity expects to be entitled in exchange for transferring promised goods or services to a customer, is to be allocated to each performance obligation in the contract based on relative standalone selling prices and recognized as revenue when (point in time) or as (over time) the performance obligation is satisfied. The Partnership generates revenues primarily by charging fees for (i) crude oil gathering, stabilization, blending, storage and transportation, (ii) natural gas gathering, gas lift, compression and processing, (iii) produced and flowback water gathering and disposal and (iv) freshwater supply and distribution. The Partnership categorizes revenues as service revenues or product sales in its Consolidated Statements of Operations. For revenues generated under fee-based arrangements, the Partnership records the fees attributable to such arrangements as service revenues in its Consolidated Statements of Operations. Under fee-based arrangements, the Partnership does not take ownership of the volumes it handles for its customers and receives fees for midstream services it provides. Revenues are recognized based upon the transaction price at month-end under the right to invoice practical expedient. For revenues generated under purchase arrangements, the Partnership takes ownership of the product prior to sale and is the principal in the transaction. Revenues and expenses are recognized on a gross basis under Product sales and Costs of product sales, respectively, in the Consolidated Statements of Operations. Cash and cash equivalents. The Partnership classifies all unrestricted cash on hand and investments with original maturity dates less than 90 days as cash equivalents. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2016-15, Statement of Cash Flows (“ASU 2016-15”), which is intended to reduce diversity in practice in how certain transactions are classified in the statement of cash flows. ASU 2016-15 was applied on a retrospective basis. The adoption of ASU 2016-15 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures. Transactions with affiliates. Transactions between Oasis Petroleum, its affiliates and the Partnership have been identified in the consolidated financial statements as transactions with affiliates. See Note 5 — Transactions with Affiliates . Property, plant and equipment. Property, plant and equipment consists primarily of pipelines, natural gas processing plants, produced and flowback water facilities and compressor stations. Property, plant and equipment is stated at the lower of historical cost less accumulated depreciation, or fair value, if impaired. The Partnership capitalizes a portion of its interest expense incurred on its outstanding debt. The amount capitalized is determined by multiplying the capitalization rate by the average amount of eligible accumulated capital expenditures and is limited to actual interest costs incurred during the period. The accumulated capital expenditures included in the capitalized interest calculation begin when the first costs are incurred and end when the asset is either placed into production or written off. The Partnership capitalized $4.9 million , $1.2 million and $4.4 million of interest costs for the years ended December 31, 2018 , 2017 and 2016 , respectively. These amounts are amortized over the useful life of the related assets once the assets are placed in-service. When assets are placed into service, management makes estimates with respect to useful lives and salvage values that management believes are reasonable. However, subsequent events could cause a change in estimates, thereby impacting future depreciation amounts. Uncertainties that may impact these estimates include, among others, changes in laws and regulations relating to environmental matters, including air and water quality, restoration and abandonment requirements, economic conditions and supply and demand in the area. Depreciation is computed over the asset’s estimated useful life using the straight line method based on estimated useful lives and asset salvage values. The weighted average life of each of the Partnership’s pipelines, natural gas processing plants, produced and flowback water facilities, compressor stations, and other long-lived assets is 30 years. When properties are retired or otherwise disposed of, the related cost and accumulated depreciation are removed from the respective accounts and any profit or loss on disposition is recognized as gain or loss. Impairment of long-lived assets. The Partnership evaluates the ability to recover the carrying amount of long-lived assets and determine whether such long-lived assets have been impaired. Impairment exists when the carrying amount of an asset exceeds estimates of the undiscounted cash flows expected to result from the use and eventual disposition of the asset. An impairment analysis requires management to apply judgment in identifying impairment indicators and estimating future cash flows. When alternative courses of action to recover the carrying amount of a long-lived asset are under consideration, estimates of future undiscounted cash flows take into account possible outcomes and probabilities of their occurrence. If the carrying amount of the long-lived asset is not recoverable based on the estimated future undiscounted cash flows, the impairment loss is measured as the excess of the asset’s carrying amount over its estimated fair value, such that the asset’s carrying amount is adjusted to its estimated fair value with an offsetting charge to impairment expense. Fair value represents the estimated price between market participants to sell an asset in the principal or most advantageous market for the asset, based on assumptions a market participant would make. When warranted, management assesses the fair value of long-lived assets using commonly accepted techniques and may use more than one source in making such assessments. The factors used to determine fair value are subject to management’s judgment and expertise and include, but are not limited to, recent third-party comparable sales, internally developed discounted cash flow analysis and analysis from outside advisors. Significant changes, such as changes in contract rates or terms, the condition of an asset or management’s intent to utilize the asset, generally require management to reassess the cash flows related to long-lived assets. A reduction of the carrying value of fixed assets would represent a Level 3 fair value measurement. If actual results are not consistent with assumptions and estimates, or assumptions and estimates change due to new information, the Partnership may be exposed to additional impairment charges. Ultimately, a prolonged period of lower commodity prices may adversely affect the estimate of future operating results through lower throughput volumes on the Partnership’s assets, which could result in future impairment charges due to the potential impact on operations and cash flows. Asset retirement obligations (“ARO”). The Partnership records the fair value of a liability for a legal obligation to retire an asset in the period in which the liability is incurred, with the corresponding cost capitalized by increasing the carrying amount of the related long-lived asset. For produced and flowback water disposal wells, this is the period in which the well is drilled or acquired. The ARO represents the estimated amount the Partnership will incur to plug, abandon and remediate the produced and flowback water properties at the end of their useful lives, in accordance with applicable state laws. The liability is accreted to its present value each period and the capitalized costs are depreciated using the straight-line method. The accretion expense is recorded as a component of depreciation and amortization in the Consolidated Statements of Operations. Some assets, including certain pipelines and the Partnership’s natural gas processing plants, have contractual or regulatory obligations to perform remediation and, in some instances, dismantlement and removal activities when the assets are abandoned. The Partnership is not able to reasonably estimate the fair value of the ARO for these assets because the settlement dates are indeterminable given the expected continued use of the assets with proper maintenance. The Partnership will record an ARO for these assets in the periods in which the settlement dates become reasonably determinable. The Partnership determines the ARO, which represents a non-financial liability which is measured at fair value on a non-recurring basis, by calculating the present value of estimated cash flows related to the liability. Estimating the future ARO requires management to make estimates and judgments regarding timing and existence of a liability, as well as what constitutes adequate restoration. Inherent in the fair value calculation are numerous assumptions and judgments including the ultimate costs, inflation factors, credit adjusted discount rates, timing of settlement and changes in the legal, regulatory, environmental and political environments. These assumptions represent Level 3 inputs. To the extent future revisions to these assumptions impact the fair value of the existing ARO liability, a corresponding adjustment is made to the related asset. Deferred financing costs. The Partnership capitalizes directly attributable costs incurred in connection with obtaining debt financing. These costs are amortized over the term of the related financing using the straight-line method, which approximates the interest method. The amortization expense is recorded as a component of interest expense in the Partnership’s Consolidated Statements of Operations. The deferred financing costs related to the Partnership’s revolving credit facility are included in other assets on the Consolidated Balance Sheets. Equity-based compensation. The Partnership has granted phantom unit awards and restricted unit awards under the Oasis Midstream Partners LP 2017 Long Term Incentive Plan (“LTIP”). The Partnership accounts for phantom unit awards as liability-classified awards in accordance with GAAP, since the Partnership intends to settle these awards in cash. The Partnership will be reimbursed by Oasis Petroleum for the cash settlement amount of these awards. The Partnership accounts for restricted units granted to certain independent directors of the General Partner as equity-classified awards in accordance with GAAP, as the Partnership intends to settle these awards in common units. Forfeitures associated with awards granted under the LTIP are accounted for when they occur. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2017-09, Scope of Modification Accounting (“ASU 2017-09”), which provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. ASU 2017-09 was adopted on a prospective basis. The adoption of ASU 2017-09 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures. Income taxes. For the period subsequent to the initial public offering, the consolidated financial statements do not include a provision for income taxes as the Partnership is generally not subject to federal or state income tax. Generally, each partner is separately taxed on its share of taxable income. For periods prior to the initial public offering, the consolidated financial statements include a provision for income tax expense. Deferred federal and state income taxes were provided on temporary differences between the financial statement carrying amounts of recognized assets and liabilities and their respective tax bases as if the Partnership filed tax returns as a stand-alone entity. Business combinations. The Partnership accounts for business combinations under the acquisition method of accounting. An income, market or cost valuation method may be utilized to estimate the fair value of the assets acquired, liabilities assumed, and non-controlling interest, if any, in a business combination. Fair value is determined on the acquisition date. Acquisition-related costs are expensed as incurred in connection with each business combination. If the initial accounting for the business combination is incomplete by the end of the reporting period in which the acquisition occurs, an estimate will be recorded. Subsequent to the acquisition, and not later than one year from the acquisition date, the Partnership will record any material adjustments to the initial estimate based on new information obtained about facts and circumstances that existed as of the acquisition date. The Partnership makes various assumptions in estimating the fair values of assets acquired and liabilities assumed. As fair value is a market-based measurement, it is determined based on the assumptions that market participants would use. The income valuation method represents the present value of future cash flows over the life of the asset using discrete financial forecasts. Such discrete financial forecasts rely on estimates and assumptions made by management. The most significant assumptions relate to management’s estimates of throughput volumes, future operating and development costs, long-term growth rates and a market-based weighted average cost of capital. The market valuation method uses prices paid for a reasonably similar asset by other purchasers in the market, with adjustments relating to any differences between the assets. The cost valuation method is based on the replacement cost of a comparable asset at prices at the time of the acquisition reduced for depreciation of the asset. Any excess of the acquisition price over the estimated fair value of net assets acquired is recorded as goodwill. Any excess of the estimated fair value of net assets acquired over the acquisition price is recorded in current earnings as a gain on bargain purchase. In the first quarter of 2018 , the Partnership adopted Accounting Standards Update No. 2017-01, Clarifying the Definition of a Business (“ASU 2017-01”), which provides guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. ASU 2017-01 was adopted on a prospective basis. The adoption of ASU 2017-01 did not result in a material impact to the Partnership’s financial position, cash flows, results of operations or financial statement disclosures. Concentrations of Market and Credit Risk The Partnership has limited direct exposure to risks associated with fluctuating commodity prices due to the nature of its business and its long-term, fixed-fee arrangements with customers. However, to the extent that the future contractual arrangements with customers, including Oasis Petroleum or third parties, do not provide for fixed-fee structures, the Partnership may become subject to commodity price risk. Additionally, as substantially all of the Partnership’s revenues are derived from Oasis Petroleum, the Partnership is indirectly subject to risks associated with fluctuating commodity prices to the extent that lower commodity prices adversely affect Oasis Petroleum’s production, drilling schedule, financial condition, leverage, market reputation, liquidity, results of operations or cash flows. Recent Accounting Pronouncements Leases. In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (“ASU 2016-02”), which established a right-of-use (“ROU”) model that requires a lessee to recognize an operating lease asset and lease liability on the balance sheet, with the exception of short-term leases. Accounting Standards Codification 842, Leases (“ASC 842”), was subsequently amended by ASU No. 2018-01, Land easement practical expedient for transition to Topic 842 (“ASU 2018-01”); ASU No. 2018-10, Codification Improvements to Topic 842; and ASU No. 2018-11, Targeted Improvements . The new standard is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The effective date and transition requirements for the amendments are the same as the effective date for ASU 2016-02. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Partnership will adopt the new standard as of January 1, 2019 using the required modified retrospective approach and plans to elect the option to recognize a cumulative effect adjustment of initially applying the guidance to the opening balance of retained earnings in the period of adoption, rather than recognizing in the earliest period presented. Prior period amounts will not be adjusted. ASU 2018-01 provides a number of optional practical expedients in transition. The Partnership expects to elect the ‘package of practical expedients’, which permits the Partnership not to reassess under the new standard prior conclusions about lease identification, lease classification and initial direct costs; the use-of hindsight practical expedient; the practical expedient pertaining to land easements, which provides an option to not evaluate under ASC 842 existing or expired land easements that were previously accounted for as leases under ASC 840, Leases ; and the practical expedient pertaining to combining lease and non-lease components. In addition, under the new standard, an entity may elect not to apply the recognition requirements of ASC 842 to short-term leases, which are leases with terms of one year or less. The Partnership expects to make this election, and as such, recognition of lease payments for short-term leases will be recognized in net income on a straight line basis. The Partnership expects the new standard will not have a material effect on its consolidated financial statements but will impact certain disclosures about the Partnership’s leasing activities. The Partnership plans to modify its business processes and controls to support the adoption of the new standard, including implementing a new lease accounting software to assess the portfolio of leases, assist in the quantification of the expected impact on the consolidated financial statements and facilitate the calculations of the related accounting entries and disclosures. The changes to controls will not materially affect the Partnership’s internal control over financial reporting, and the Partnership does not expect a significant change in its leasing activities as a result of this adoption. |