Apache Offshore Investment Partnership (AOIP) 10-K 26 Feb 21 2020 FY Annual report Financial data

Cover

Cover	12 Months Ended
	Dec. 31, 2020USD ($)shares
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	0-13546
Entity Registrant Name	APACHE OFFSHORE INVESTMENT PARTNERSHIP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	41-1464066
Entity Address, Address Line One	One Post Oak Central, 2000 Post Oak Boulevard, Suite 100,
Entity Address, City or Town	Houston,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77056-4400
City Area Code	713
Local Phone Number	296-6000
Title of 12(g) Security	Partnership Units
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float | $	$ 0
Entity Common Stock, Shares Outstanding | shares	1,021.5
Documents Incorporated by Reference	Portions of Apache Corporation’s proxy statement relating to its 2021 annual meeting of stockholders (the Apache Proxy Statement) have been incorporated by reference into Part III hereof. On January 4, 2021, Apache Corporation (Apache) announced that its Board of Directors has authorized Apache to effect a holding company reorganization, in connection with which, Apache will create a new holding company, APA Corporation (APA). Upon consummation of the holding company reorganization, Apache will be a wholly-owned subsidiary of APA, and APA will be the successor issuer to Apache pursuant to Rule 12g-3(a) under the Securities Exchange Act of 1934, as amended, and will replace Apache as the public company trading on the Nasdaq stock market. If the holding company reorganization is completed prior to the date that the Apache Proxy Statement is filed with the SEC, then the Apache Proxy Statement will be filed by APA, as successor issuer to Apache.
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000727538

STATEMENT OF CONSOLIDATED OPERA

STATEMENT OF CONSOLIDATED OPERATIONS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
REVENUES:
Oil and gas sales	$ 619,161	$ 1,100,334	$ 1,416,934
Interest income	24,034	106,787	81,368
Total Revenues	643,195	1,207,121	1,498,302
EXPENSES:
Depreciation, depletion and amortization recurring	200,045	264,031	297,328
Asset retirement obligation accretion	52,943	77,805	96,832
Lease operating expenses			492,713
Lease operating expenses	391,751	530,206
Gathering and transportation costs	10,736	15,823	17,493
Administrative	320,704	328,536	323,200
Total Expenses	976,179	1,216,401	1,227,566
NET INCOME (LOSS)	(332,984)	(9,280)	270,736
NET INCOME (LOSS) ALLOCATED TO:
Managing Partner	(35,828)	30,385	96,704
Investing Partners	(297,156)	(39,665)	174,032
NET INCOME (LOSS)	$ (332,984)	$ (9,280)	$ 270,736
NET INCOME (LOSS) PER INVESTING PARTNER UNIT (in USD per share)	$ (291)	$ (39)	$ 170
WEIGHTED AVERAGE INVESTING PARTNER UNITS OUTSTANDING (in shares)	1,021.5	1,021.5	1,021.5

STATEMENT OF CONSOLIDATED CASH

STATEMENT OF CONSOLIDATED CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (332,984)	$ (9,280)	$ 270,736
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation, depletion and amortization	200,045	264,031	297,328
Asset retirement obligation accretion	52,943	77,805	96,832
Changes in operating assets and liabilities:
Accrued revenues receivable	13,103	11,423	(27,235)
Receivable from/Payable to Apache Corporation	(12,419)	6,517	(2,329)
Accrued operating expenses	(1,152)	(14,414)	(9,441)
Asset retirement expenditures	(492,120)	(397,542)	(429,502)
Net cash provided by (used in) operating activities	(572,584)	(61,460)	196,389
CASH FLOWS FROM INVESTING ACTIVITIES:
Additions to oil and gas properties	(9)	(18,481)	(158,444)
Net cash used in investing activities	(9)	(18,481)	(158,444)
CASH FLOWS FROM FINANCING ACTIVITIES:
Contributions from Managing Partner	67,627	0	0
Distributions to Managing Partner	0	(2,963)	(52,094)
Net cash provided by (used in) financing activities	67,627	(2,963)	(52,094)
NET DECREASE IN CASH AND CASH EQUIVALENTS	(504,966)	(82,904)	(14,149)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	5,020,432	5,103,336	5,117,485
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 4,515,466	$ 5,020,432	$ 5,103,336

CONSOLIDATED BALANCE SHEET

CONSOLIDATED BALANCE SHEET - USD ($)	Dec. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 4,515,466	$ 5,020,432
Accrued revenues receivable	95,590	108,693
Receivable from Apache Corporation	4,830	0
Total Current Assets	4,615,886	5,129,125
OIL AND GAS PROPERTIES, on the basis of full cost accounting:
Proved properties	195,727,413	195,401,395
Less – Accumulated depreciation, depletion and amortization	(191,659,260)	(191,459,215)
Total oil and gas properties, on the basis of full cost accounting	4,068,153	3,942,180
Total Assets	8,684,039	9,071,305
CURRENT LIABILITIES:
Payable to Apache Corporation	0	7,589
Current asset retirement obligation	526,440	614,493
Accrued operating expenses	75,848	77,000
Other accrued costs	0	76,410
Total Current Liabilities	602,288	775,492
ASSET RETIREMENT OBLIGATION	858,084	806,789
PARTNERS’ CAPITAL:
Managing Partner	523,407	491,608
Investing Partners (1,021.5 units outstanding)	6,700,260	6,997,416
Total Partners' Capital	7,223,667	7,489,024
Total liabilities and partners' capital	$ 8,684,039	$ 9,071,305

CONSOLIDATED BALANCE SHEET (Par

CONSOLIDATED BALANCE SHEET (Parenthetical) - shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Investing partners, units outstanding (in shares)	1,021.5	1,021.5

STATEMENT OF CONSOLIDATED CHANG

STATEMENT OF CONSOLIDATED CHANGES IN PARTNERS' CAPITAL - USD ($)	Total	Managing Partner	Investing Partners
BEGINNING BALANCE at Dec. 31, 2017	$ 7,282,625	$ 419,576	$ 6,863,049
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions	(52,094)	(52,094)
Net income (loss)	270,736	96,704	174,032
ENDING BALANCE at Dec. 31, 2018	7,501,267	464,186	7,037,081
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions	(2,963)	(2,963)
Net income (loss)	(9,280)	30,385	(39,665)
ENDING BALANCE at Dec. 31, 2019	7,489,024	491,608	6,997,416
Increase (Decrease) in Partners' Capital [Roll Forward]
Contributions	67,627	67,627
Net income (loss)	(332,984)	(35,828)	(297,156)
ENDING BALANCE at Dec. 31, 2020	$ 7,223,667	$ 523,407	$ 6,700,260

ORGANIZATION

ORGANIZATION	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION	ORGANIZATION Nature of Operations Apache Offshore Investment Partnership, a Delaware general partnership (the Investment Partnership), was formed on October 31, 1983, consisting of Apache Corporation (Apache or Managing Partner) as Managing Partner and public investors (the Investing Partners). The Investment Partnership invested its entire capital in Apache Offshore Petroleum Limited Partnership, a Delaware limited partnership (the Operating Partnership). The primary business of the Investment Partnership is to serve as the sole limited partner of the Operating Partnership. The primary business of the Operating Partnership is to conduct oil and gas development and production operations. The Operating Partnership conducts the operations of the Investment Partnership. The accompanying financial statements include the accounts of both the Investment Partnership and Operating Partnership. The Investing Partners purchased Units of Partnership Interests (Units) in the Investment Partnership at $150,000 per Unit, with five percent down and the balance in payments as called by the Investment Partnership. In 1989, the Investment Partnership determined that the full $150,000 per Unit was not needed, fixed the total calls at $85,000 per Unit, and released the Investing Partners from liability for future calls. The Investment Partnership invested, and will continue to invest, its entire capital in the Operating Partnership. Apache is the managing partner of the Investment Partnership and the general partner of the Operating Partnership, and held approximately five percent of the 1,021.5 Units outstanding at December 31, 2020. As used hereafter, the term “Partnership” refers to the Investment Partnership or the Operating Partnership, as the case may be. Except for an additional interest acquired in Matagorda Island Block 681 and 682 in 1992, the Partnership acquired its oil and gas interests through the purchase of an 85 percent interest in offshore properties acquired by Apache as a co-venturer in a series of oil and gas exploration, development and production activities on 87 federal lease tracts in the Gulf of Mexico, offshore Louisiana and Texas. The remaining 15 percent interest was purchased by an affiliated partnership or retained by Apache. As of December 31, 2020, the Partnership has only one active venture prospect at South Timbalier 295, located offshore Louisiana, with a 7.08 percent working interest. The Partnership’s future financial condition and results of operations will depend largely upon prices received for its oil and natural gas production and the costs of developing and producing reserves. A substantial portion of the Partnership’s production is sold under market-sensitive contracts. Prices for oil and natural gas are subject to fluctuations in response to changes in supply, market uncertainty and a variety of factors beyond the Partnership’s control. These factors include worldwide political instability (especially in the Middle East), the foreign supply of oil and natural gas, the price of foreign imports, the level of consumer demand, and the price and availability of alternative fuels. Under the terms of the Partnership Agreement of the Investment Partnership (the Partnership Agreement), the Investing Partners receive 80 percent and Apache receives 20 percent of revenue. Lease operating, gathering and transportation, and administrative expenses are allocated to the Investing Partners and Apache in the same proportion as revenues. The Investing Partners receive 100 percent of the interest income earned on short-term cash investments. The Investing Partners generally pay for 90 percent and Apache generally pays for 10 percent of exploration and development costs and expenses incurred by the Partnership. However, intangible drilling costs, interest costs and fees or expenses related to the loans incurred by the Partnership are allocated 99 percent to the Investing Partners and one percent to Apache until such time as the amount so allocated to the Investing Partners equals 90 percent of the total amount of such costs, including such costs incurred by Apache prior to the formation of the Partnership. Notice of Withdrawal On March 22, 2019, Apache, as the Managing Partner of the Investment Partnership, gave notice of its intention to withdraw as Managing Partner of the Investment Partnership. The notice described the withdrawal process and certain notice periods required by that process. No party assumed the role of Managing Partner within the 120-day notice period specified by the notice of intention to withdraw. Consequently, Apache will oversee the process of winding up and liquidating the business and affairs of the Investment Partnership. Apache has not made a decision as to when it will complete the process to withdraw as Managing Partner. Right of Presentment In February 1994, an amendment to the Partnership Agreement created a right of presentment under which all Investing Partners had a limited and voluntary right to offer their Units to the Partnership twice each year to be purchased for cash. On April 26, 2019, the Managing Partner determined that, during the withdrawal and dissolution process noted above, it would be inconsistent with the Managing Partner’s fiduciary duties to purchase (or to cause the Investment Partnership to purchase) outstanding units of partnership interests (Units) from the holders thereof pursuant to the right of presentment provided for in Sections 6.9 through 6.14 of the Partnership Agreement. As a result of this determination by the Managing Partner, pursuant to Section 6.12 of the Partnership Agreement, the right of presentment was terminated for 2019 and future periods. Sections 6.9 through 6.14 have “become null and void and of no further force or effect” as provided in Section 6.12. Prior to terminating the right of presentment, the Investment Partnership had not made a repurchase under the right of presentment since 2008.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Accounting policies used by the Partnership reflect industry practices and conform to accounting principles generally accepted in the United States (GAAP). Significant policies are discussed below. Statement Presentation The accompanying consolidated financial statements include the accounts of Apache Offshore Investment Partnership and Apache Offshore Petroleum Limited Partnership after elimination of intercompany balances and transactions. Use of Estimates The preparation of financial statements in conformity with GAAP and the disclosure of contingent assets and liabilities requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Partnership bases its estimates on historical experience and various other assumptions that are believed to be reasonable under the circumstances. The Partnership evaluates its estimates and assumptions on a regular basis. Actual results may differ from these estimates and assumptions used in preparation of its financial statements and changes in these estimates are recorded when known. Significant estimates with regard to these financial statements include the estimate of proved oil and gas reserve quantities and the related present value of estimated future net cash flows therefrom (see Note 10—Supplemental Oil and Gas Disclosures (Unaudited) ) and the assessment of asset retirement obligations (see Note 8—Asset Retirement Obligation ). Cash Equivalents The Partnership considers all highly liquid short-term investments with an original maturity of three months or less at the time of purchase to be cash equivalents. These investments are carried at cost, which approximates fair value. As of December 31, 2020 and 2019, the Partnership had $4.5 million and $5.0 million, respectively, of cash and cash equivalents. Oil and Gas Properties The Partnership follows the full-cost method of accounting for its investment in oil and gas properties for financial statement purposes. Under this method of accounting, the Partnership capitalizes all acquisition, exploration and development costs incurred for the purpose of finding oil and gas reserves. The amounts capitalized under this method include dry hole costs, leasehold costs, engineering, geological, exploration, development and other similar costs. All costs related to production and administrative functions are expensed in the period incurred. The Partnership includes the present value of its dismantlement, restoration, and abandonment costs within the capitalized oil and gas property balance as described in Note 8—Asset Retirement Obligation . Unless greater than 25 percent of the Partnership’s reserve volumes are sold, proceeds from the sale of oil and gas properties are accounted for as reductions to capitalized costs, and gains or losses are not recognized. Capitalized costs of oil and gas properties are amortized on the future gross revenue method whereby depreciation, depletion and amortization (DD&A) expense is computed quarterly by dividing current period oil and gas sales by estimated future gross revenue from proved oil and gas reserves (including current period oil and gas sales) and applying the resulting rate to the net cost of evaluated oil and gas properties, including estimated future development costs. Under the full-cost method of accounting, the Partnership limits the capitalized costs of proved oil and gas properties, net of accumulated DD&A, to the estimated future net cash flows from proved oil and gas reserves discounted at 10 percent, plus the lower of cost or fair value of unproved properties included in the costs being amortized, if any. This ceiling test is performed each quarter. If capitalized costs exceed this limit, the excess is charged to expense and reflected as additional DD&A in the accompanying statement of consolidated operations. Estimated future net cash flows are calculated using end-of-period costs and an unweighted arithmetic average of commodity prices in effect on the first day of each of the previous 12 months, held flat for the life of the production, except where prices are defined by contractual arrangements. The Partnership did not record any write-downs of capitalized costs during 2020, 2019, or 2018. See Note 10—Supplemental Oil and Gas Disclosures (Unaudited) for a discussion on the calculation of estimated future net cash flows. Asset Retirement Costs and Obligation The initial estimated asset retirement obligation related to property and equipment is recorded as a liability at its fair value, with an offsetting asset retirement cost recorded as an increase to oil and gas properties on the consolidated balance sheet. If the fair value of the recorded asset retirement obligation changes, a revision is recorded to both the asset retirement obligation and the asset retirement cost. Revisions in estimated liabilities can result from changes in estimated inflation rates, changes in service and equipment costs and changes in the estimated timing of settling asset retirement obligations. Accretion expense on the liability is recognized over the estimated productive life of the related assets. Revenue Recognition The Partnership applies the provisions of Accounting Standards Codification 606 for revenue recognition to contracts with customers. Sales of crude oil, natural gas, and natural gas liquids (NGLs) are included in revenue when production is sold to a customer in fulfillment of performance obligations under the terms of agreed contracts. Performance obligations primarily comprise delivery of oil, gas, or NGLs at a delivery point, as negotiated within each contract. Each barrel of oil, MMBtu of natural gas, or other unit of measure is separately identifiable and represents a distinct performance obligation to which the transaction price is allocated. Performance obligations are satisfied at a point in time once control of the product has been transferred to the customer. The Partnership considers a variety of facts and circumstances in assessing the point of control transfer, including but not limited to: whether the purchaser can direct the use of the hydrocarbons, the transfer of significant risks and rewards, the Partnership’s right to payment, and transfer of legal title. In each case, the term between delivery and when payments are due is not significant. Apache, as Managing Partner of the Partnership, markets the Partnership’s share of oil production from South Timbalier 295, the Partnership’s largest source of revenue. Apache primarily markets to major oil companies, marketing and transportation companies, and refiners at current index prices, adjusted for quality, transportation, and market reflective differentials. The Partnership markets all other production under the joint operating agreements with the operator of its properties. The operator seeks and negotiates oil and gas marketing arrangements with various marketers and purchasers. These contracts provide for sales that are priced at prevailing market prices. The Partnership records trade accounts receivable for its unconditional rights to consideration arising under sales contracts with customers. The carrying value of such receivables, net of the allowance for doubtful accounts, represents estimated net realizable value. The Partnership routinely assesses the collectability of all material trade and other receivables. The Partnership accrues a reserve on a receivable when, based on the judgment of management, it is probable that a receivable will not be collected and the amount of any reserve may be reasonably estimated. As of December 31, 2020, the carrying amounts of trade accounts receivables approximate fair value because of the short-term nature of these instruments. Receivables from contracts with customers totaled $95,590 and $108,693 as of December 31, 2020 and 2019, respectively. The Partnership has concluded that disaggregating revenue by product appropriately depicts how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. The table below presents the total oil, gas, and NGLs revenues of the Partnership for the years ended December 31, 2020, 2019 and 2018: For the Year Ended December 31, 2020 2019 2018 Oil $ 532,261 $ 990,659 $ 1,253,490 Gas $ 70,999 94,057 120,763 NGLs $ 15,901 15,618 42,681 Total Oil and Gas Revenue $ 619,161 $ 1,100,334 $ 1,416,934 The Partnership did not have any revenue from non-customers. Insurance Coverage The Partnership recognizes an insurance receivable when collection of the receivable is deemed probable. Any recognition of an insurance receivable is recorded by crediting and offsetting the original charge. Any differential arising between insurance recoveries and insurance receivables is recorded as a capitalized cost or as an expense, consistent with its original treatment. Net Income (Loss) Per Investing Unit The net income (loss) per Investing Partner Unit is calculated by dividing the aggregate Investing Partners’ net income (loss) for the period by the number of weighted average Investing Partner Units outstanding for that period. Income Taxes The profit or loss of the Partnership for federal income tax reporting purposes is included in the income tax returns of the partners. Accordingly, no recognition has been given to income taxes in the accompanying financial statements. Receivable from/Payable to Apache Corporation The receivable from/payable to Apache Corporation, the Partnership’s Managing Partner, represents the net result of the Investing Partners’ revenue and expenditure transactions in the current month. Generally, cash in this amount will be paid by Apache to the Partnership or transferred to Apache in the month after the Partnership’s transactions are processed and the net results of operations are determined. Maintenance and Repairs Maintenance and repairs are charged to expense as incurred. New Pronouncements Issued But Not Yet Adopted In October 2020, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) 2020-10, “Codification Improvements,” which clarifies or improves disclosure requirements for various topics to align with the SEC’s regulations. This update is effective for the Partnership beginning in the first quarter of 2021 and will be applied retrospectively. The Partnership is evaluating the effect of the adoption of the ASU and does not believe it will have a material impact on its financial statements.

COMPENSATION TO AFFILIATES

COMPENSATION TO AFFILIATES	12 Months Ended
	Dec. 31, 2020
Text Block [Abstract]
COMPENSATION TO AFFILIATES	COMPENSATION TO AFFILIATES Apache is entitled to the following types of compensation and reimbursement for costs and expenses. Total Reimbursed by the Investing Partners for 2020 2019 2018 (In thousands) Apache is reimbursed for general, administrative and overhead expenses incurred in connection with the management and operation of the Partnership’s business $ 257 $ 263 $ 259 Apache operated certain Partnership properties through September 30, 2013, at which time Fieldwood Energy LLC purchased Apache’s interest in South Timbalier 295 and Ship Shoal 258/259 and became operator of these properties. Billings to the Partnership were made on the same basis as to unaffiliated third parties or at prevailing industry rates.

OIL AND GAS PROPERTIES

OIL AND GAS PROPERTIES	12 Months Ended
	Dec. 31, 2020
Extractive Industries [Abstract]
OIL AND GAS PROPERTIES	OIL AND GAS PROPERTIES The following tables contain direct cost information and changes in the Partnership’s oil and gas properties for each of the years referenced. All costs of oil and gas properties are currently being amortized. 2020 2019 2018 (In thousands) Oil and Gas Properties Balance, beginning of year $ 195,401 $ 195,327 $ 195,005 Costs incurred during the year: Development – Investing Partners 293 67 291 Managing Partner 33 7 31 Balance, end of year $ 195,727 $ 195,401 $ 195,327 Development costs for 2020, 2019, and 2018 included upward revisions of approximately $326 thousand, $56 thousand, and $305 thousand, respectively, for estimated abandonment costs primarily related to revised cost estimates on the Ship Shoal 258/259 properties. Approximately $18 thousand and $17 thousand of capital costs were incurred in 2019 and 2018, respectively, for participation in pipeline and recompletion projects at South Timbalier 295. Managing Investing Total (In thousands) Accumulated Depreciation, Depletion and Amortization Balance, December 31, 2017 $ 21,104 $ 169,794 $ 190,898 Provision 16 281 297 Balance, December 31, 2018 $ 21,120 $ 170,075 $ 191,195 Provision 14 250 264 Balance, December 31, 2019 $ 21,134 $ 170,325 $ 191,459 Provision 11 189 200 Balance, December 31, 2020 $ 21,145 $ 170,514 $ 191,659 The Partnership’s aggregate DD&A expense as a percentage of oil and gas sales for 2020, 2019, and 2018 was 32 percent, 24 percent and 21 percent, respectively.

MAJOR CUSTOMER AND RELATED PART

MAJOR CUSTOMER AND RELATED PARTIES INFORMATION	12 Months Ended
	Dec. 31, 2020
Risks and Uncertainties [Abstract]
MAJOR CUSTOMER AND RELATED PARTIES INFORMATION	MAJOR CUSTOMER AND RELATED PARTIES INFORMATION Revenues received from major third-party customers that equaled ten percent or more of oil and gas sales are discussed below. No other third-party customers individually accounted for ten percent or more of oil and gas sales. Remittances from Fieldwood Energy LLC accounted for 14 percent, 10 percent and 12 percent of the Partnership’s oil and gas sales for the years 2020, 2019 and 2018, respectively. Approximately 86 percent, 90 percent and 88 percent of the Partnership’s oil and gas sales in 2020, 2019 and 2018, respectively, were to Chevron Products Company. The Partnership’s revenues are derived principally from uncollateralized sales to customers in the oil and gas industry; therefore, customers may be similarly affected by changes in economic and other conditions within the industry. The Partnership has not experienced material credit losses on such sales.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTSCertain assets and liabilities are reported at fair value on a recurring basis in the Partnership’s consolidated balance sheet. As of December 31, 2020 and December 31, 2019, the carrying amounts of cash, cash equivalents, accounts receivable, and accounts payable were determined to approximate fair value because of the short-term nature or maturity of these instruments.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Litigation – The Partnership is subject to governmental and regulatory controls arising in the ordinary course of business. It is the opinion of Apache’s management that all claims and litigation involving the Partnership are not likely to have a material adverse effect on its financial position or results of operations. Environmental – The Partnership, as an owner or lessee of interests in oil and gas properties, is subject to various federal, state and local laws and regulations relating to discharge of materials into, and protection of, the environment. These laws and regulations may, among other things, impose liability on the lessee under an oil and gas lease for the cost of pollution clean-up resulting from operations and subject the lessee to liability for pollution damages. Apache maintains insurance coverage on the Partnership’s properties, which it believes is customary in the industry, although the Partnership is not fully insured against all environmental risks. On August 3, 2020, Fieldwood Energy LLC, the current operator of the Partnership’s producing lease, and certain of its affiliated debtors (collectively, Fieldwood) filed a voluntary petition for relief under Chapter 11 of the United States Bankruptcy Code in the United States Bankruptcy Court for the Southern District of Texas (Case No. 20-33948). Fieldwood has submitted a plan of reorganization, and the Partnership’s Managing Partner has been engaged in discussions with Fieldwood and other interested parties regarding such plan. However, as of the date of this report, the Partnership does not know if, or to what extent, Fieldwood will continue to perform its obligations with respect to the Partnership’s properties. The outcome of Fieldwood’s bankruptcy could have a material adverse effect on the Partnership’s result of operations. No evaluation of the likelihood of an unfavorable outcome or associated economic loss can be made; therefore, no liability has been recorded on the Partnership’s consolidated financial statements. With respect to oil and gas operations in the Gulf of Mexico, the BOEM has issued Notice to Lessees (NTL) No. 2016-N01 pertaining to the obligations of companies to provide supplemental assurances for performance with respect to plugging, abandonment, decommissioning, and site clearance obligations associated with wells, platforms, structures, and facilities located upon or used in connection with such companies’ oil and gas leases. Under this NTL, implementation of which is currently suspended and which may be revised by the BOEM, the Partnership may be required to provide additional security to BOEM with respect to plugging, abandonment, and decommissioning obligations relating to the Partnership’s current ownership interests in various Gulf of Mexico leases. The Partnership will likely satisfy such requirements through the provision of bonds or other forms of security.

ASSET RETIREMENT OBLIGATION

ASSET RETIREMENT OBLIGATION	12 Months Ended
	Dec. 31, 2020
Asset Retirement Obligation Disclosure [Abstract]
ASSET RETIREMENT OBLIGATION	ASSET RETIREMENT OBLIGATION The following table describes the changes to the Partnership’s asset retirement obligation (ARO) liability for the years ended December 31, 2020 and 2019: 2020 2019 Asset retirement obligation at beginning of year $ 1,421,282 $ 1,635,812 Accretion expense 52,943 77,805 Liabilities settled (415,710) (347,952) Revisions in estimated liabilities 326,009 55,617 Asset retirement obligation at end of year $ 1,384,524 $ 1,421,282 Less current portion (526,440) (614,493) Asset retirement obligation, long-term $ 858,084 $ 806,789 The ARO liability reflects the estimated present value of the amount of dismantlement, removal, site reclamation, and similar activities associated with the Partnership’s oil and gas properties. The Partnership utilizes estimates from property operators and current market costs to estimate the expected cash outflows for retirement obligations. The Partnership estimates the ultimate productive life of the properties, a risk-adjusted discount rate, and an inflation factor in order to determine the current present value of this obligation. To the extent future revisions to these assumptions impact the present value of the existing ARO liability, a corresponding adjustment is made to the oil and gas property balance. Liabilities settled primarily relate to individual wells plugged and abandoned and platform decommissioning during the periods presented. The current portion of the ARO liability represents the retirement obligation expected to be incurred in the next twelve months. Decommissioning and abandonment activities began at Ship Shoal 258/259 upon cessation of the lease in 2018 and are close to completion. The lease was relinquished earlier than previously estimated given unplanned third-party pipeline issues and the decision that returning the lease to production was uneconomic. The operator also experienced challenges related to the plugging of wells and weather-related delays which resulted in revising the field’s estimated abandonment obligation based on projected costs. Both factors contributed to the upward cost revisions to ARO liability estimates the past two years.

TAX-BASIS FINANCIAL INFORMATION

TAX-BASIS FINANCIAL INFORMATION	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
TAX-BASIS FINANCIAL INFORMATION	TAX-BASIS FINANCIAL INFORMATION A reconciliation of ordinary income for federal income tax reporting purposes to net income under accounting principles generally accepted in the United States is as follows: 2020 2019 2018 Net partnership ordinary income (loss) for federal income tax reporting purposes $ (549,623) $ (80,046) $ (196,919) Plus: Items of current expense for tax reporting purposes only – Intangible drilling cost 9 113 16,859 Dismantlement and abandonment cost 415,710 347,952 555,501 Tax depreciation 53,908 64,537 289,455 469,627 412,602 861,815 Less: full cost DD&A expense (200,045) (264,031) (297,328) Less: asset retirement obligation accretion (52,943) (77,805) (96,832) Net income (loss) $ (332,984) (9,280) 270,736 The Partnership’s tax basis in net oil and gas properties at December 31, 2020, and 2019 was $2,685,573 and $2,505,692, respectively, lower than the carrying value of oil and gas properties under full cost accounting. The difference reflects the timing deductions for depreciation, depletion and amortization, intangible drilling costs and dismantlement and abandonment costs. For federal income tax reporting, the Partnership had capitalized syndication cost of $8,660,878 at December 31, 2020, and 2019. A reconciliation of liabilities for federal income tax reporting purposes to liabilities under accounting principles generally accepted in the United States is as follows: December 31, 2020 2019 Liabilities for federal income tax purposes $ 75,848 $ 160,999 Asset retirement liability 1,384,524 1,421,282 Liabilities under accounting principles generally accepted in the United States $ 1,460,372 $ 1,582,281 Asset retirement liabilities for future dismantlement and abandonment costs are not recognized for federal income tax reporting purposes until settled.

SUPPLEMENTAL OIL AND GAS DISCLO

SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited)	12 Months Ended
	Dec. 31, 2020
Extractive Industries [Abstract]
SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited)	SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited) Oil and Gas Reserve Information Proved oil and gas reserves are the estimated quantities of natural gas, crude oil, condensate, and NGLs that geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing conditions, operating conditions, and government regulations. There are numerous uncertainties inherent in estimating quantities of proved reserves and projecting future rates of production and timing of development expenditures. The following reserve data represents estimates only and should not be construed as being exact. (Oil and NGL in Mbbls and gas in MMcf) 2020 2019 2018 Oil NGL Gas Oil NGL Gas Oil NGL Gas Proved Reserves Beginning of year 361 27 626 363 29 670 376 54 1,016 Extensions, discoveries and other additions — — — — — — — — — Revisions of previous estimates 3 — (1) 15 (1) (10) 6 (24) (309) Production (14) (1) (28) (17) (1) (34) (19) (1) (37) End of year 350 26 597 361 27 626 363 29 670 Proved Developed Beginning of year 361 27 626 363 29 670 376 54 1,016 End of year 350 26 597 361 27 626 363 29 670 Oil includes crude oil and condensate. All the Partnership’s reserves as of December 31, 2020 are located on federal lease tracts in the Gulf of Mexico, offshore Louisiana. Approximately 86 percent of the Partnership’s current proved developed reserves on a barrels of oil equivalent basis are classified as proved not producing. These reserves relate to zones that are either behind pipe, or that have been completed but not yet produced or zones that have been produced in the past, but are now not producing due to mechanical reasons. These reserves may be regarded as less certain than producing reserves because they are frequently based on volumetric calculations rather than performance data. Future production associated with behind pipe reserves is scheduled to follow depletion of the currently producing zones in the same wellbores. It should be noted that additional capital will have to be spent to access these reserves. The capital and economic impact of production timing is reflected in the Partnership’s standardized measure under Future Net Cash Flows. Future Net Cash Flows Future cash inflows as of December 31, 2020, 2019, and 2018 were calculated using an unweighted arithmetic average of oil and gas prices in effect on the first day of each month in the respective year, except where prices are defined by contractual arrangements. Operating costs, production and ad valorem taxes and future development costs are based on current costs with no escalation. The following table sets forth unaudited information concerning future net cash flows from proved oil and gas reserves. As the Partnership pays no income taxes, estimated future income tax expenses are omitted. This information does not purport to present the fair value of the Partnership’s oil and gas assets, but does present a standardized disclosure concerning possible future net cash flows that would result under the assumptions used. Discounted Future Net Cash Flows Relating to Proved Reserves December 31, 2020 2019 2018 (In thousands) Future cash inflows $ 15,329 $ 24,158 $ 28,707 Future production costs (5,116) (5,540) (5,937) Future development costs (1) (3,204) (3,483) (3,831) Net cash flows 7,009 15,135 18,939 10 percent annual discount rate (2,267) (4,735) (7,316) Discounted future net cash flows $ 4,742 $ 10,400 $ 11,623 (1) This amount includes estimated abandonment costs. The following table sets forth the principal sources of change in the discounted future net cash flows: For the Year Ended December 31, 2020 2019 2018 (In thousands) Sales, net of production costs $ (217) $ (554) $ (907) Net change in prices and production costs (5,668) (2,476) 4,996 Revisions of quantities 43 273 (1,820) Accretion of discount 1,040 1,162 823 Changes in future development costs (1) (122) (39) (257) Previously estimated development costs incurred during the period 492 416 584 Changes in production rates and other (1,226) (5) (28) $ (5,658) $ (1,223) $ 3,391 (1) This amount includes estimated abandonment costs.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Statement Presentation	Statement Presentation The accompanying consolidated financial statements include the accounts of Apache Offshore Investment Partnership and Apache Offshore Petroleum Limited Partnership after elimination of intercompany balances and transactions.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP and the disclosure of contingent assets and liabilities requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Partnership bases its estimates on historical experience and various other assumptions that are believed to be reasonable under the circumstances. The Partnership evaluates its estimates and assumptions on a regular basis. Actual results may differ from these estimates and assumptions used in preparation of its financial statements and changes in these estimates are recorded when known. Significant estimates with regard to these financial statements include the estimate of proved oil and gas reserve quantities and the related present value of estimated future net cash flows therefrom (see Note 10—Supplemental Oil and Gas Disclosures (Unaudited) ) and the assessment of asset retirement obligations (see Note 8—Asset Retirement Obligation ).
Cash Equivalents	Cash Equivalents The Partnership considers all highly liquid short-term investments with an original maturity of three months or less at the time of purchase to be cash equivalents. These investments are carried at cost, which approximates fair value. As of December 31, 2020 and 2019, the Partnership had $4.5 million and $5.0 million, respectively, of cash and cash equivalents.
Oil and Gas Properties	Oil and Gas Properties The Partnership follows the full-cost method of accounting for its investment in oil and gas properties for financial statement purposes. Under this method of accounting, the Partnership capitalizes all acquisition, exploration and development costs incurred for the purpose of finding oil and gas reserves. The amounts capitalized under this method include dry hole costs, leasehold costs, engineering, geological, exploration, development and other similar costs. All costs related to production and administrative functions are expensed in the period incurred. The Partnership includes the present value of its dismantlement, restoration, and abandonment costs within the capitalized oil and gas property balance as described in Note 8—Asset Retirement Obligation . Unless greater than 25 percent of the Partnership’s reserve volumes are sold, proceeds from the sale of oil and gas properties are accounted for as reductions to capitalized costs, and gains or losses are not recognized. Capitalized costs of oil and gas properties are amortized on the future gross revenue method whereby depreciation, depletion and amortization (DD&A) expense is computed quarterly by dividing current period oil and gas sales by estimated future gross revenue from proved oil and gas reserves (including current period oil and gas sales) and applying the resulting rate to the net cost of evaluated oil and gas properties, including estimated future development costs. Under the full-cost method of accounting, the Partnership limits the capitalized costs of proved oil and gas properties, net of accumulated DD&A, to the estimated future net cash flows from proved oil and gas reserves discounted at 10 percent, plus the lower of cost or fair value of unproved properties included in the costs being amortized, if any. This ceiling test is performed each quarter. If capitalized costs exceed this limit, the excess is charged to expense and reflected as additional DD&A in the accompanying statement of consolidated operations. Estimated future net cash flows are calculated using end-of-period costs and an unweighted arithmetic average of commodity prices in effect on the first day of each of the previous 12 months, held flat for the life of the production, except where prices are defined by contractual arrangements. The Partnership did not record any write-downs of capitalized costs during 2020, 2019, or 2018. See Note 10—Supplemental Oil and Gas Disclosures (Unaudited) for a discussion on the calculation of estimated future net cash flows.
Asset Retirement Costs and Obligation	Asset Retirement Costs and Obligation The initial estimated asset retirement obligation related to property and equipment is recorded as a liability at its fair value, with an offsetting asset retirement cost recorded as an increase to oil and gas properties on the consolidated balance sheet. If the fair value of the recorded asset retirement obligation changes, a revision is recorded to both the asset retirement obligation and the asset retirement cost. Revisions in estimated liabilities can result from changes in estimated inflation rates, changes in service and equipment costs and changes in the estimated timing of settling asset retirement obligations. Accretion expense on the liability is recognized over the estimated productive life of the related assets.
Revenue Recognition	Revenue Recognition The Partnership applies the provisions of Accounting Standards Codification 606 for revenue recognition to contracts with customers. Sales of crude oil, natural gas, and natural gas liquids (NGLs) are included in revenue when production is sold to a customer in fulfillment of performance obligations under the terms of agreed contracts. Performance obligations primarily comprise delivery of oil, gas, or NGLs at a delivery point, as negotiated within each contract. Each barrel of oil, MMBtu of natural gas, or other unit of measure is separately identifiable and represents a distinct performance obligation to which the transaction price is allocated. Performance obligations are satisfied at a point in time once control of the product has been transferred to the customer. The Partnership considers a variety of facts and circumstances in assessing the point of control transfer, including but not limited to: whether the purchaser can direct the use of the hydrocarbons, the transfer of significant risks and rewards, the Partnership’s right to payment, and transfer of legal title. In each case, the term between delivery and when payments are due is not significant. Apache, as Managing Partner of the Partnership, markets the Partnership’s share of oil production from South Timbalier 295, the Partnership’s largest source of revenue. Apache primarily markets to major oil companies, marketing and transportation companies, and refiners at current index prices, adjusted for quality, transportation, and market reflective differentials. The Partnership markets all other production under the joint operating agreements with the operator of its properties. The operator seeks and negotiates oil and gas marketing arrangements with various marketers and purchasers. These contracts provide for sales that are priced at prevailing market prices.
Insurance Coverage	Insurance Coverage The Partnership recognizes an insurance receivable when collection of the receivable is deemed probable. Any recognition of an insurance receivable is recorded by crediting and offsetting the original charge. Any differential arising between insurance recoveries and insurance receivables is recorded as a capitalized cost or as an expense, consistent with its original treatment.
Net Income (Loss) Per Investing Unit	Net Income (Loss) Per Investing Unit The net income (loss) per Investing Partner Unit is calculated by dividing the aggregate Investing Partners’ net income (loss) for the period by the number of weighted average Investing Partner Units outstanding for that period.
Income Taxes	Income Taxes The profit or loss of the Partnership for federal income tax reporting purposes is included in the income tax returns of the partners. Accordingly, no recognition has been given to income taxes in the accompanying financial statements.
Receivable from / Payable to Apache Corporation	Receivable from/Payable to Apache Corporation The receivable from/payable to Apache Corporation, the Partnership’s Managing Partner, represents the net result of the Investing Partners’ revenue and expenditure transactions in the current month. Generally, cash in this amount will be paid by Apache to the Partnership or transferred to Apache in the month after the Partnership’s transactions are processed and the net results of operations are determined.
Maintenance and Repairs	Maintenance and Repairs Maintenance and repairs are charged to expense as incurred.
New Pronouncements Issued But Not Yet Adopted	New Pronouncements Issued But Not Yet Adopted In October 2020, the Financial Accounting Standards Board issued Accounting Standards Update (ASU) 2020-10, “Codification Improvements,” which clarifies or improves disclosure requirements for various topics to align with the SEC’s regulations. This update is effective for the Partnership beginning in the first quarter of 2021 and will be applied retrospectively. The Partnership is evaluating the effect of the adoption of the ASU and does not believe it will have a material impact on its financial statements.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Disaggregation of Revenue	The table below presents the total oil, gas, and NGLs revenues of the Partnership for the years ended December 31, 2020, 2019 and 2018: For the Year Ended December 31, 2020 2019 2018 Oil $ 532,261 $ 990,659 $ 1,253,490 Gas $ 70,999 94,057 120,763 NGLs $ 15,901 15,618 42,681 Total Oil and Gas Revenue $ 619,161 $ 1,100,334 $ 1,416,934

COMPENSATION TO AFFILIATES (Tab

COMPENSATION TO AFFILIATES (Tables)	12 Months Ended
	Dec. 31, 2020
Text Block [Abstract]
Compensation and Reimbursement for Costs and Expenses	Apache is entitled to the following types of compensation and reimbursement for costs and expenses. Total Reimbursed by the Investing Partners for 2020 2019 2018 (In thousands) Apache is reimbursed for general, administrative and overhead expenses incurred in connection with the management and operation of the Partnership’s business $ 257 $ 263 $ 259

OIL AND GAS PROPERTIES (Tables)

OIL AND GAS PROPERTIES (Tables)	12 Months Ended
	Dec. 31, 2020
Extractive Industries [Abstract]
Direct Cost Information	The following tables contain direct cost information and changes in the Partnership’s oil and gas properties for each of the years referenced. All costs of oil and gas properties are currently being amortized. 2020 2019 2018 (In thousands) Oil and Gas Properties Balance, beginning of year $ 195,401 $ 195,327 $ 195,005 Costs incurred during the year: Development – Investing Partners 293 67 291 Managing Partner 33 7 31 Balance, end of year $ 195,727 $ 195,401 $ 195,327
Changes in Partnership's Oil and Gas Properties	Managing Investing Total (In thousands) Accumulated Depreciation, Depletion and Amortization Balance, December 31, 2017 $ 21,104 $ 169,794 $ 190,898 Provision 16 281 297 Balance, December 31, 2018 $ 21,120 $ 170,075 $ 191,195 Provision 14 250 264 Balance, December 31, 2019 $ 21,134 $ 170,325 $ 191,459 Provision 11 189 200 Balance, December 31, 2020 $ 21,145 $ 170,514 $ 191,659

ASSET RETIREMENT OBLIGATION (Ta

ASSET RETIREMENT OBLIGATION (Tables)	12 Months Ended
	Dec. 31, 2020
Asset Retirement Obligation Disclosure [Abstract]
Changes to Partnership's Asset Retirement Obligation Liability	The following table describes the changes to the Partnership’s asset retirement obligation (ARO) liability for the years ended December 31, 2020 and 2019: 2020 2019 Asset retirement obligation at beginning of year $ 1,421,282 $ 1,635,812 Accretion expense 52,943 77,805 Liabilities settled (415,710) (347,952) Revisions in estimated liabilities 326,009 55,617 Asset retirement obligation at end of year $ 1,384,524 $ 1,421,282 Less current portion (526,440) (614,493) Asset retirement obligation, long-term $ 858,084 $ 806,789

TAX-BASIS FINANCIAL INFORMATI_2

TAX-BASIS FINANCIAL INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Reconciliation of Ordinary Income for Federal Income Tax Reporting Purposes	A reconciliation of ordinary income for federal income tax reporting purposes to net income under accounting principles generally accepted in the United States is as follows: 2020 2019 2018 Net partnership ordinary income (loss) for federal income tax reporting purposes $ (549,623) $ (80,046) $ (196,919) Plus: Items of current expense for tax reporting purposes only – Intangible drilling cost 9 113 16,859 Dismantlement and abandonment cost 415,710 347,952 555,501 Tax depreciation 53,908 64,537 289,455 469,627 412,602 861,815 Less: full cost DD&A expense (200,045) (264,031) (297,328) Less: asset retirement obligation accretion (52,943) (77,805) (96,832) Net income (loss) $ (332,984) (9,280) 270,736
Reconciliation of Liabilities for Federal Income Tax Reporting Purposes	A reconciliation of liabilities for federal income tax reporting purposes to liabilities under accounting principles generally accepted in the United States is as follows: December 31, 2020 2019 Liabilities for federal income tax purposes $ 75,848 $ 160,999 Asset retirement liability 1,384,524 1,421,282 Liabilities under accounting principles generally accepted in the United States $ 1,460,372 $ 1,582,281

SUPPLEMENTAL OIL AND GAS DISC_2

SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Extractive Industries [Abstract]
Proved Reserves and Projecting Future Rates of Production and Timing of Development Expenditures	The following reserve data represents estimates only and should not be construed as being exact. (Oil and NGL in Mbbls and gas in MMcf) 2020 2019 2018 Oil NGL Gas Oil NGL Gas Oil NGL Gas Proved Reserves Beginning of year 361 27 626 363 29 670 376 54 1,016 Extensions, discoveries and other additions — — — — — — — — — Revisions of previous estimates 3 — (1) 15 (1) (10) 6 (24) (309) Production (14) (1) (28) (17) (1) (34) (19) (1) (37) End of year 350 26 597 361 27 626 363 29 670 Proved Developed Beginning of year 361 27 626 363 29 670 376 54 1,016 End of year 350 26 597 361 27 626 363 29 670
Discounted Future Net Cash Flows Relating to Proved Reserves	Discounted Future Net Cash Flows Relating to Proved Reserves December 31, 2020 2019 2018 (In thousands) Future cash inflows $ 15,329 $ 24,158 $ 28,707 Future production costs (5,116) (5,540) (5,937) Future development costs (1) (3,204) (3,483) (3,831) Net cash flows 7,009 15,135 18,939 10 percent annual discount rate (2,267) (4,735) (7,316) Discounted future net cash flows $ 4,742 $ 10,400 $ 11,623 (1) This amount includes estimated abandonment costs.
Discounted Future Net Cash Flows	The following table sets forth the principal sources of change in the discounted future net cash flows: For the Year Ended December 31, 2020 2019 2018 (In thousands) Sales, net of production costs $ (217) $ (554) $ (907) Net change in prices and production costs (5,668) (2,476) 4,996 Revisions of quantities 43 273 (1,820) Accretion of discount 1,040 1,162 823 Changes in future development costs (1) (122) (39) (257) Previously estimated development costs incurred during the period 492 416 584 Changes in production rates and other (1,226) (5) (28) $ (5,658) $ (1,223) $ 3,391 (1) This amount includes estimated abandonment costs.

ORGANIZATION (Detail)

ORGANIZATION (Detail)	Mar. 22, 2019	Dec. 31, 2020LeaseVentureshares	Dec. 31, 1989$ / shares	Dec. 31, 1988$ / shares	Dec. 31, 2019shares
Schedule Of Organization [Line Items]
Full purchase price (in USD per share)				$ 150,000
Discount percentage on full purchase price				5.00%
Investor subscription units (in USD per share)			$ 85,000
Investing partners, units outstanding (in shares) | shares		1,021.5			1,021.5
Percentage interest Purchased in offshore leasehold		85.00%
Number of federal lease tracts | Lease		87
Percentage of remaining interest purchased		15.00%
Number of remaining ventures | Venture		1
Working percentage interest		7.08%
Percentage of exploration and development costs incurred paid by Company		10.00%
Percentage of expenses related to loans		1.00%
Notice of intention to withdrawal, notice period	120 days
Apache
Schedule Of Organization [Line Items]
Percentage share held in partnership		5.00%
Investing Partners
Schedule Of Organization [Line Items]
Percent of revenues		80.00%
Percentage of interest income earned on short term cash investments		100.00%
Percentage of exploration and development costs incurred paid by Partners		90.00%
Percentage of expenses related to loans		99.00%
Percentage of partner's total amount equals to cost		90.00%
Managing Partner
Schedule Of Organization [Line Items]
Percent of revenues		20.00%

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 4,515,466	$ 5,020,432
Percentage of reserve volumes sold	25.00%
Estimated future net cash flows from proved oil and gas reserves	10.00%
Non-cash write-downs of carrying value of proved oil and gas properties	$ 0	0	$ 0
Receivables from contracts with customers	$ 95,590	$ 108,693

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Oil and gas sales	$ 619,161	$ 1,100,334	$ 1,416,934
Oil
Disaggregation of Revenue [Line Items]
Oil and gas sales	532,261	990,659	1,253,490
Gas
Disaggregation of Revenue [Line Items]
Oil and gas sales	70,999	94,057	120,763
NGLs
Disaggregation of Revenue [Line Items]
Oil and gas sales	$ 15,901	$ 15,618	$ 42,681

COMPENSATION TO AFFILIATES (Det

COMPENSATION TO AFFILIATES (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments in and Advances to Affiliates, Schedule of Investments [Abstract]
Apache is reimbursed for general, administrative and overhead expenses incurred in connection with the management and operation of the Partnership’s business	$ 257	$ 263	$ 259

OIL AND GAS PROPERTIES - Direct

OIL AND GAS PROPERTIES - Direct Cost Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Direct Cost Changes In Partnership's Oil And Gas Properties [Roll Forward]
Balance, beginning of year	$ 195,401	$ 195,327	$ 195,005
Development - Investing Partners	293	67	291
Development - Managing Partner	33	7	31
Balance, end of year	$ 195,727	$ 195,401	$ 195,327

OIL AND GAS PROPERTIES - Additi

OIL AND GAS PROPERTIES - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Extractive Industries [Abstract]
Upward (negative) revisions of abandonment cost and deferral of abandonment	$ 326	$ 56	$ 305
Asset retirement expense		$ 18	$ 17
DD&A rate as percentage of oil and gas sales	32.00%	24.00%	21.00%

OIL AND GAS PROPERTIES - Change

OIL AND GAS PROPERTIES - Changes in Partnership's Oil and Gas Properties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Depreciation, Depletion and Amortization
Beginning Balance	$ 191,459	$ 191,195	$ 190,898
Provision	200	264	297
Ending Balance	191,659	191,459	191,195
Managing Partner
Accumulated Depreciation, Depletion and Amortization
Beginning Balance	21,134	21,120	21,104
Provision	11	14	16
Ending Balance	21,145	21,134	21,120
Investing Partners
Accumulated Depreciation, Depletion and Amortization
Beginning Balance	170,325	170,075	169,794
Provision	189	250	281
Ending Balance	$ 170,514	$ 170,325	$ 170,075

MAJOR CUSTOMER AND RELATED PA_2

MAJOR CUSTOMER AND RELATED PARTIES INFORMATION (Detail) - Customer Concentration Risk - Sales	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fieldwood Energy LLC
Revenue, Major Customer [Line Items]
Concentration risk percentage	14.00%	10.00%	12.00%
Chevron Products Company
Revenue, Major Customer [Line Items]
Concentration risk percentage	86.00%	90.00%	88.00%

ASSET RETIREMENT OBLIGATION (De

ASSET RETIREMENT OBLIGATION (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation at beginning of year	$ 1,421,282	$ 1,635,812
Accretion expense	52,943	77,805	$ 96,832
Liabilities settled	(415,710)	(347,952)
Revisions in estimated liabilities	326,009	55,617
Asset retirement obligation at end of year	1,384,524	1,421,282	1,635,812
Asset retirement obligation at end of year	$ 1,421,282	$ 1,421,282	$ 1,635,812	$ 1,384,524	$ 1,421,282
Less current portion				(526,440)	(614,493)
Asset retirement obligation, long-term				$ 858,084	$ 806,789

TAX-BASIS FINANCIAL INFORMATI_3

TAX-BASIS FINANCIAL INFORMATION - Reconciliation of Ordinary Income for Federal Income Tax Reporting Purposes (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net partnership ordinary income (loss) for federal income tax reporting purposes	$ (549,623)	$ (80,046)	$ (196,919)
Plus: Items of current expense for tax reporting purposes only –
Intangible drilling cost	9	113	16,859
Dismantlement and abandonment cost	415,710	347,952	555,501
Tax depreciation	53,908	64,537	289,455
Non deductible expenses for federal income tax purposes	469,627	412,602	861,815
Less: full cost DD&A expense	(200,045)	(264,031)	(297,328)
Less: asset retirement obligation accretion	(52,943)	(77,805)	(96,832)
Net income (loss)	$ (332,984)	$ (9,280)	$ 270,736

TAX-BASIS FINANCIAL INFORMATI_4

TAX-BASIS FINANCIAL INFORMATION - Additional Information (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax bases in net oil and gas properties	$ 2,685,573	$ 2,505,692
Capitalized syndication cost	$ 8,660,878	$ 8,660,878

TAX-BASIS FINANCIAL INFORMATI_5

TAX-BASIS FINANCIAL INFORMATION - Reconciliation of Liabilities for Federal Income Tax Reporting Purposes (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Liabilities for federal income tax purposes	$ 75,848	$ 160,999
Asset retirement liability	1,384,524	1,421,282	$ 1,635,812
Liabilities under accounting principles generally accepted in the United States	$ 1,460,372	$ 1,582,281

SUPPLEMENTAL OIL AND GAS DISC_3

SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited) - Proved Reserves and Projecting Future Rates of Production and Timing of Development Expenditures (Detail)	12 Months Ended
	Dec. 31, 2020MBblsMMcf	Dec. 31, 2019MMcfMBbls	Dec. 31, 2018MMcfMBbls
Proved Developed and Undeveloped Reserves [Roll Forward]
Percentage of estimated proved developed reserves classified as proved not producing	86.00%
Oil | Proved Reserves
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning of year	361	363	376
Extensions, discoveries and other additions	0	0	0
Revisions of previous estimates	3	15	6
Production	(14)	(17)	(19)
End of year	350	361	363
Oil | Proved Developed
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning of year	361	363	376
End of year	350	361	363
NGLs | Proved Reserves
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning of year	27	29	54
Extensions, discoveries and other additions	0	0	0
Revisions of previous estimates	0	(1)	(24)
Production	(1)	(1)	(1)
End of year	26	27	29
NGLs | Proved Developed
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning of year	27	29	54
End of year	26	27	29
Gas | Proved Reserves
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning of year | MMcf	626	670	1,016
Extensions, discoveries and other additions | MMcf	0	0	0
Revisions of previous estimates | MMcf	(1)	(10)	(309)
Production | MMcf	(28)	(34)	(37)
End of year | MMcf	597	626	670
Gas | Proved Developed
Proved Developed and Undeveloped Reserves [Roll Forward]
Beginning of year | MMcf	626	670	1,016
End of year | MMcf	597	626	670

SUPPLEMENTAL OIL AND GAS DISC_4

SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited) - Discounted Future Net Cash Flows Relating to Proved Reserves (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Oil And Gas Disclosures [Abstract]
Future cash inflows	$ 15,329	$ 24,158	$ 28,707
Future production costs	(5,116)	(5,540)	(5,937)
Future development costs	(3,204)	(3,483)	(3,831)
Net cash flows	7,009	15,135	18,939
10 percent annual discount rate	(2,267)	(4,735)	(7,316)
Discounted future net cash flows	$ 4,742	$ 10,400	$ 11,623

SUPPLEMENTAL OIL AND GAS DISC_5

SUPPLEMENTAL OIL AND GAS DISCLOSURES (Unaudited) - Discounted Future Net Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Oil And Gas Disclosures [Abstract]
Sales, net of production costs	$ (217)	$ (554)	$ (907)
Net change in prices and production costs	(5,668)	(2,476)	4,996
Revisions of quantities	43	273	(1,820)
Accretion of discount	1,040	1,162	823
Changes in future development costs	(122)	(39)	(257)
Previously estimated development costs incurred during the period	492	416	584
Changes in production rates and other	(1,226)	(5)	(28)
Total	$ (5,658)	$ (1,223)	$ 3,391