Supplemental oil, NGL and natural gas disclosures (unaudited) | Note 20 Supplemental oil, NGL and natural gas disclosures (unaudited) a. Costs incurred in oil and natural gas property acquisition, exploration and development activities The following table presents costs incurred in the acquisition, exploration and development of oil and natural gas properties, with asset retirement obligations included in evaluated property acquisition costs and development costs, for the periods presented: Years ended December 31, (in thousands) 2019 2018 2017 Property acquisition costs: Evaluated $ 126,372 $ 15,072 $ — Unevaluated 83,738 2,790 — Exploration costs 19,954 23,884 36,257 Development costs 450,501 607,790 560,919 Total costs incurred $ 680,565 $ 649,536 $ 597,176 b. Aggregate capitalized oil, NGL and natural gas costs The following table presents the aggregate capitalized costs related to oil, NGL and natural gas production activities with applicable accumulated depletion and impairment as of the dates presented: (in thousands) December 31, 2019 December 31, 2018 Gross capitalized costs: Evaluated properties $ 7,421,799 $ 6,752,631 Unevaluated properties not being depleted 142,354 130,957 Total gross capitalized costs 7,564,153 6,883,588 Less accumulated depletion and impairment (5,725,114 ) (4,854,017 ) Net capitalized costs $ 1,839,039 $ 2,029,571 The following table presents a summary of the unevaluated property costs not being depleted as of December 31, 2019 , by year in which such costs were incurred: (in thousands) 2019 2018 2017 2016 and prior Total Unevaluated properties not being depleted $ 97,213 $ 5,028 $ 4,905 $ 35,208 $ 142,354 Unevaluated properties, which are not subject to depletion, are not individually significant and consist of costs for acquiring oil and natural gas leasehold where no evaluated reserves have been identified, including costs of wells being evaluated. The evaluation process associated with these properties has not been completed and therefore, the Company is unable to estimate when these costs will be included in the depletion calculation. c. Results of operations of oil, NGL and natural gas producing activities The following table presents the results of operations of oil, NGL and natural gas producing activities (excluding corporate overhead and interest costs) for the periods presented: Years ended December 31, (in thousands) 2019 2018 2017 Revenues: Oil, NGL and natural gas sales $ 706,548 $ 808,530 $ 621,507 Production costs: Lease operating expenses 90,786 91,289 75,049 Production and ad valorem taxes 40,712 49,457 37,802 Transportation and marketing expenses 25,397 11,704 — Total production costs 156,895 152,450 112,851 Other costs: Depletion 250,857 196,458 143,592 Accretion of asset retirement obligations 3,926 4,233 3,567 Impairment expense 620,565 — — Income tax (benefit) expense (1) (3,257 ) 4,554 — Total other costs 872,091 205,245 147,159 Results of operations $ (322,438 ) $ 450,835 $ 361,497 _____________________________________________________________________________ (1) During each of the years ended December 31, 2019, 2018 and 2017, the Company recorded valuation allowances against its deferred tax assets related to its oil, NGL and natural gas producing activities. Accordingly, the income tax (benefit) expense was computed utilizing the Company's effective tax rates of 1% for the years ended December 31, 2019 and 2018 and 0% for the year ended December 31, 2017, which reflects tax deductions and tax credits and allowances relating to the oil, NGL and natural gas producing activities that are reflected in the Company's "Total income tax benefit (expense)" on the consolidated statements of operations. d. Net proved oil, NGL and natural gas reserves Ryder Scott Company, L.P. ("Ryder Scott"), the Company's independent reserve engineers, estimated 100% of the Company's proved reserves as of December 31, 2019 , 2018 and 2017 . In accordance with SEC regulations, the reserves as of December 31, 2019 , 2018 and 2017 were estimated using the Realized Prices, which reflect adjustments to the Benchmark Prices for quality, transportation fees, geographical differentials, marketing bonuses or deductions and other factors affecting the price received at the wellhead . See Note 6.a for these Realized Prices. The Company's reserves as of December 31, 2019 , 2018 and 2017 are reported in three streams: oil, NGL and natural gas. The SEC has defined proved reserves as the estimated quantities of oil, NGL and natural gas that geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions. The process of estimating oil, NGL and natural gas reserves is complex, requiring significant decisions in the evaluation of available geological, geophysical, engineering and economic data. The data for a given property may also change substantially over time as a result of numerous factors, including additional development activity, evolving production history and a continual reassessment of the viability of production under changing economic conditions. As a result, material revisions to existing reserve estimates occur from time to time. Although every reasonable effort is made to ensure that reserve estimates reported represent the most accurate assessments possible, the subjective decisions and variances in available data for various properties increase the likelihood of significant changes in these estimates. If such changes are material, they could significantly affect future amortization of capitalized costs and result in impairment of assets that may be material. The following tables provide an analysis of the changes in estimated proved reserve quantities of oil, NGL and natural gas for the years ended December 31, 2019 , 2018 and 2017 , all of which are located within the U.S. Year ended December 31, 2019 Oil NGL (MBbl) Natural gas MBOE Proved developed and undeveloped reserves: Beginning of year 61,894 86,647 537,756 238,167 Revisions of previous estimates (7,865 ) 5,301 69,678 9,049 Extensions, discoveries and other additions 13,573 12,614 83,345 40,078 Acquisitions of reserves in place 21,413 6,754 44,627 35,605 Production (10,376 ) (9,118 ) (60,169 ) (29,522 ) End of year 78,639 102,198 675,237 293,377 Proved developed reserves: Beginning of year 55,893 79,241 491,828 217,105 End of year 52,711 90,861 600,334 243,628 Proved undeveloped reserves: Beginning of year 6,001 7,406 45,928 21,062 End of year 25,928 11,337 74,903 49,749 Year ended December 31, 2018 Oil NGL (MBbl) Natural gas MBOE Proved developed and undeveloped reserves: Beginning of year 79,413 67,371 414,592 215,883 Revisions of previous estimates (20,921 ) 11,089 72,028 2,173 Extensions, discoveries and other additions 13,330 15,112 93,762 44,069 Acquisitions of reserves in place 596 457 2,810 1,521 Divestitures of reserves in place (349 ) (123 ) (756 ) (598 ) Production (10,175 ) (7,259 ) (44,680 ) (24,881 ) End of year 61,894 86,647 537,756 238,167 Proved developed reserves: Beginning of year 68,877 60,441 371,946 191,309 End of year 55,893 79,241 491,828 217,105 Proved undeveloped reserves: Beginning of year 10,536 6,930 42,646 24,574 End of year 6,001 7,406 45,928 21,062 Year ended December 31, 2017 Oil NGL Natural gas MBOE Proved developed and undeveloped reserves: Beginning of year 63,940 50,350 316,857 167,100 Revisions of previous estimates 9,818 13,158 74,247 35,351 Extensions, discoveries and other additions 15,250 9,711 59,759 34,921 Divestitures of reserves in place (120 ) (48 ) (299 ) (218 ) Production (9,475 ) (5,800 ) (35,972 ) (21,270 ) End of year 79,413 67,371 414,592 215,883 Proved developed reserves: Beginning of year 53,156 42,950 270,291 141,155 End of year 68,877 60,441 371,946 191,309 Proved undeveloped reserves: Beginning of year 10,784 7,400 46,566 25,945 End of year 10,536 6,930 42,646 24,574 The following discussion is for the year ended December 31, 2019. The Company's positive revision of 9,049 MBOE of previously estimated quantities consisted of (i) 20,858 MBOE of positive revisions from performance of proved developed producing wells, (ii) 12,417 MBOE of negative revisions from a decrease in the Realized Prices for oil, NGL and natural gas and other changes to proved developed producing wells and (iii) 608 MBOE of positive revisions due to proved undeveloped locations that were removed from the development plan in prior years. Extensions, discoveries and other additions of 40,078 MBOE consisted of (i) 24,629 MBOE that resulted from new wells drilled and (ii) 15,449 MBOE that resulted from new horizontal proved undeveloped locations added in our established acreage. Acquisitions of reserves in place of 35,605 MBOE consisted of (i) 1,306 MBOE from new proved developed producing wells and (ii) 34,299 MBOE from 86 new proved undeveloped locations in Howard and western Glasscock Counties of Texas. The following discussion is for the year ended December 31, 2018. The Company's positive revision of 2,173 MBOE of previously estimated quantities consisted of (i) 11,364 MBOE of negative revisions from performance driven mainly by steeper oil decline curves and tighter well spacing, and a decrease in the Realized Price for natural gas, (ii) 7,045 MBOE of positive revisions from increases in the Realized Prices for oil and NGL and other changes to proved developed producing wells and (iii) 6,492 MBOE of positive revisions due to proved undeveloped locations that were removed from the development plan in prior years, eight of these locations were drilled in 2018 and two were scheduled to be drilled in 2019. Extensions, discoveries and other additions of 44,069 MBOE consisted of (i) 25,617 MBOE that resulted from new wells drilled and (ii) 18,452 MBOE that resulted from new horizontal proved undeveloped locations added. The following discussion is for the year ended December 31, 2017. The Company's positive revision of 35,351 MBOE of previously estimated quantities consisted of (i) 16,916 MBOE from positive performance, price increases and other changes to proved developed producing wells and (ii) 18,435 MBOE of revisions due to proved undeveloped locations that were removed from the development plan in prior years, 10 of these locations were drilled in 2017 and eight were scheduled to be drilled in 2018. Extensions, discoveries and other additions of 34,921 MBOE consisted of (i) 18,985 MBOE that resulted from new wells drilled and (ii) 15,936 MBOE that resulted from new horizontal proved undeveloped locations added. e. Standardized measure of discounted future net cash flows The standardized measure of discounted future net cash flows does not purport to be, nor should it be interpreted to present, the fair value of the oil, NGL and natural gas reserves of the property. An estimate of fair value would take into account, among other things, the recovery of reserves not presently classified as proved, the value of proved properties and consideration of expected future economic and operating conditions. The estimates of future cash flows and future production and development costs as of December 31, 2019 , 2018 and 2017 are based on the Realized Prices, which reflect adjustments to the Benchmark Prices for quality, transportation fees, geographical differentials, marketing bonuses or deductions and other factors affecting the price received at the wellhead . All Realized Prices are held flat over the forecast period for all reserve categories in calculating the discounted future net revenues. Any effect from the Company's commodity hedges is excluded. In accordance with SEC regulations, the proved reserves were anticipated to be economically producible from the "as of date" forward based on existing economic conditions, including prices and costs at which economic producibility from a reservoir was determined. These costs, held flat over the forecast period, include development costs, operating costs, ad valorem and production taxes and abandonment costs after salvage. Future income tax expenses are computed using the appropriate year-end statutory tax rates applied to the future pretax net cash flows from proved oil, NGL and natural gas reserves, less the tax basis of the Company's oil and natural gas properties. The estimated future net cash flows are then discounted at a rate of 10% . The Company's unamortized cost of evaluated oil and natural gas properties being depleted exceeded the full cost ceiling as of September 30, 2019 and December 31, 2019 , but did not record any similar impairments for the years ended December 31, 2018 or 2017 . See Note 6.a for discussion of the Benchmark Prices, Realized Prices and the 2019 full cost ceiling impairment recorded. The following table presents the standardized measure of discounted future net cash flows relating to proved oil, NGL and natural gas reserves for the periods presented: Years ended December 31, (in thousands) 2019 2018 2017 Future cash inflows $ 5,702,580 $ 6,266,862 $ 5,777,533 Future production costs (1,994,732 ) (1,977,401 ) (1,675,837 ) Future development costs (615,839 ) (257,310 ) (307,689 ) Future income tax expenses (24,392 ) (226,183 ) (237,153 ) Future net cash flows 3,067,617 3,805,968 3,556,854 10% discount for estimated timing of cash flows (1,405,356 ) (1,691,731 ) (1,786,533 ) Standardized measure of discounted future net cash flows $ 1,662,261 $ 2,114,237 $ 1,770,321 It is not intended that the FASB's standardized measure of discounted future net cash flows represent the fair market value of the Company's proved reserves. The Company cautions that the disclosures shown are based on estimates of proved reserve quantities and future production schedules which are inherently imprecise and subject to revision, and the 10% discount rate is arbitrary. In addition, prices and costs as of the measurement date are used in the determinations, and no value may be assigned to probable or possible reserves. The following table presents the changes in the standardized measure of discounted future net cash flows relating to proved oil, NGL and natural gas reserves for the periods presented: Years ended December 31, (in thousands) 2019 2018 2017 Standardized measure of discounted future net cash flows, beginning of year $ 2,114,237 $ 1,770,321 $ 978,494 Changes in the year resulting from: Sales, less production costs (549,653 ) (656,080 ) (508,656 ) Revisions of previous quantity estimates 36,182 (179,912 ) 289,150 Extensions, discoveries and other additions 361,479 521,605 296,129 Net change in prices and production costs (900,019 ) 365,902 474,831 Changes in estimated future development costs 14,876 7,246 10,989 Previously estimated development costs incurred during the period 158,631 207,865 192,332 Acquisitions of reserves in place 207,636 11,411 — Divestitures of reserves in place — (6,015 ) (793 ) Accretion of discount 217,119 181,693 97,849 Net change in income taxes 46,939 (10,340 ) (46,610 ) Timing differences and other (45,166 ) (99,459 ) (13,394 ) Standardized measure of discounted future net cash flows, end of year $ 1,662,261 $ 2,114,237 $ 1,770,321 Estimates of economically recoverable oil, NGL and natural gas reserves and of future net revenues are based upon a number of variable factors and assumptions, all of which are, to some degree, subjective and may vary considerably from actual results. Therefore, actual production, revenues, development and operating expenditures may not occur as estimated. The reserve data are estimates only, are subject to many uncertainties and are based on data gained from production histories and on assumptions as to geologic formations and other matters. Actual quantities of oil, NGL and natural gas may differ materially from the amounts estimated. |