Supplementary Information of Oil and Gas Operations—Unaudited | Supplementary Information on Oil and Gas Operations—Unaudited The following tables disclose certain financial data relative to the Company’s oil and gas producing activities, which are located onshore and offshore in the continental United States: Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities ( amounts in thousands ) For the Year-Ended December 31, 2015 2014 2013 Acquisition costs: Proved (1) $ 2,287 $ 3,064 $ 177,880 Unproved (1) 2,550 39,164 35,008 Exploration costs: Proved 29,322 67,297 34,344 Unproved 7,677 13,515 20,112 Development costs 9,888 55,722 41,328 Capitalized general and administrative and interest costs 12,881 22,121 19,911 Total costs incurred $ 64,605 $ 200,883 $ 328,583 For the Year-Ended December 31, 2015 2014 2013 Accumulated depreciation, depletion and amortization (DD&A) Balance, beginning of year $ (1,648,060 ) $ (1,553,044 ) $ (1,472,244 ) Provision for DD&A (62,138 ) (86,406 ) (69,357 ) Ceiling test writedown (266,562 ) — — Sale of proved properties and other (2) (3) 819,305 (8,610 ) (11,443 ) Balance, end of year $ (1,157,455 ) $ (1,648,060 ) $ (1,553,044 ) DD&A per Mcfe $ 1.82 $ 1.99 $ 1.82 (1) During 2014 , the Company entered into a joint venture in Louisiana for an aggregate purchase price of $24 million for an approximate 30,000 acre leasehold position. During 2013 , the Company closed on the Gulf of Mexico Acquisition for an aggregate cash purchase price of $188.8 million (see Note 2). Additionally, the Company acquired 13,500 net unevaluated acres in Oklahoma targeting the Woodford Shale in 2013 . (2) During 2015 , the Company sold its Woodford and Mississippian Lime assets for an aggregate cash purchase price of $274.1 million (see Note 2). (3) During 2015 , the Company sold its Fort Trinidad assets for net proceeds of approximately $0.5 million and its East Haynesville assets for net proceeds of approximately $0.1 million . During 2014 , the Company sold its Eagle Ford assets for net proceeds of approximately $9.8 million . During 2013 , the Company sold 50% of its saltwater disposal systems and related surface assets in the Woodford for net proceeds of approximately $10.4 million and its non-operated Wyoming assets for a cash purchase price of $1.0 million . At December 31, 2015 and 2014 , unevaluated oil and gas properties totaled $12.5 million and $109.1 million , respectively, and were not subject to depletion. Unevaluated costs at December 31, 2015 included $0.2 million of costs related to two exploratory wells in progress at year-end. These costs are expected to be transferred to evaluated oil and gas properties during 2016 upon the completion of drilling. At December 31, 2014 , unevaluated costs included $16.8 million related to 16 exploratory wells in progress. All of these costs were transferred to evaluated oil and gas properties during 2015 . The Company capitalized $4.7 million , $10.0 million and $6.6 million of interest during 2015 , 2014 and 2013 , respectively. Of the total unevaluated oil and gas property costs of $12.5 million at December 31, 2015 , $(3.1) million , or (25)% , was incurred in 2015 , $3.6 million , or 29% , was incurred in 2014 and $12.1 million , or 96% , was incurred in prior years. The Company expects that the majority of the unevaluated costs at December 31, 2015 will be evaluated within the next 3 years, including $0.2 million that the Company expects to be evaluated during 2016 . Oil and Gas Reserve Information The Company’s net proved oil and gas reserves at December 31, 2015 have been estimated by independent petroleum engineers in accordance with guidelines established by the SEC using a historical 12-month average pricing assumption. The estimates of proved oil and gas reserves constitute those quantities of oil, gas,and natural gas liquids, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible—from a given date forward, from known reservoirs, and under existing economic conditions, operating methods, and government regulations—prior to the time at which contracts providing the right to operate expire, unless evidence indicates that renewal is reasonably certain, regardless of whether deterministic or probabilistic methods are used for the estimation. However, there are numerous uncertainties inherent in estimating quantities of proved reserves and in providing the future rates of production and timing of development expenditures. The following reserve data represents estimates only and should not be construed as being exact. In addition, the present values should not be construed as the current market value of the Company’s oil and gas properties or the cost that would be incurred to obtain equivalent reserves. The following table sets forth an analysis of the Company’s estimated quantities of net proved and proved developed oil (including condensate), gas and natural gas liquid reserves, all located onshore and offshore in the continental United States: Oil NGL Natural Gas Total Proved reserves as of December 31, 2012 1,635 24,366 188,264 222,441 Revisions of previous estimates (156 ) 804 38,383 38,247 Extensions, discoveries and other additions 434 6,099 30,429 39,132 Purchase of producing properties 1,833 1,915 22,274 35,187 Sale of reserves in place (34 ) — (15 ) (218 ) Production (681 ) (4,754 ) (29,226 ) (38,066 ) Proved reserves as of December 31, 2013 3,031 28,430 250,109 296,723 Revisions of previous estimates (37 ) 2,894 9,976 12,650 Extensions, discoveries and other additions 475 49,990 82,364 135,205 Sale of reserves in place (229 ) (334 ) (2,396 ) (4,105 ) Production (803 ) (7,482 ) (31,028 ) (43,325 ) Proved reserves as of December 31, 2014 2,437 73,498 309,025 397,148 Revisions of previous estimates (211 ) (3,571 ) (9,852 ) (14,698 ) Extensions, discoveries and other additions 163 16,078 45,645 62,702 Sale of reserves in place (54 ) (45,692 ) (186,972 ) (232,988 ) Production (529 ) (5,487 ) (25,502 ) (34,160 ) Proved reserves as of December 31, 2015 1,806 34,826 132,344 178,004 Proved developed reserves As of December 31, 2013 2,709 23,173 163,728 203,152 As of December 31, 2014 2,089 42,584 182,567 237,688 As of December 31, 2015 1,549 15,792 78,533 103,615 Proved undeveloped reserves As of December 31, 2013 322 5,257 86,381 93,571 As of December 31, 2014 348 30,914 126,458 159,460 As of December 31, 2015 257 19,034 53,811 74,389 Year Ended December 31, 2015 During 2015 , the Company’s estimated proved reserves decrease d by 55% . Sales of reserves in place was primarily due to the divestiture of the majority of the Company's Woodford and Mississippian Lime assets. Extensions, discoveries and other additions of 63 Bcfe were primarily due to successful drilling programs in the Company's Oklahoma and East Texas fields. The Company added approximately 17 Bcfe of proved reserves in Oklahoma and 44 Bcfe in Texas. Overall, the Company had a 95% drilling success rate during 2015 on 56 gross wells drilled. Year Ended December 31, 2014 During 2014 , the Company’s estimated proved reserves increase d by 34% . Extensions, discoveries and other additions of 135 Bcfe were primarily due to successful drilling programs in the Company's Oklahoma and East Texas fields and its Thunder Bayou discovery. The Company added approximately 72 Bcfe of proved reserves in Oklahoma, 46 Bcfe in Texas and 15 Bcfe in the Gulf Coast. Overall, the Company had a 91% drilling success rate during 2014 on 58 gross wells drilled. Year Ended December 31, 2013 Extensions, discoveries and other additions were primarily due to the success of the Company's Oklahoma, Texas and Gulf Coast drilling programs. The Company added approximately 23 Bcfe of proved reserves in Oklahoma, 5 Bcfe in the Gulf Coast and 10 Bcfe in Texas. Revisions of previous estimates were primarily a result of the increase in the historical 12-month average price per Mcf of natural gas used to calculate estimated proved reserves, which was $3.11 per Mcf at December 31, 2013 as compared to $2.20 per Mcf at December 31, 2012. The 35 Bcfe added through purchase of producing properties relates to the Company's Gulf of Mexico Acquisition (See Note 2). The following tables (amounts in thousands) present the standardized measure of future net cash flows related to proved oil and gas reserves together with changes therein, as defined by ASC Topic 932. Future production and development costs are based on current costs with no escalations. Estimated future cash flows have been discounted to their present values based on a 10% annual discount rate. Standardized Measure December 31, 2015 2014 2013 Future cash flows $ 487,834 $ 1,711,404 $ 1,243,627 Future production costs (171,678 ) (372,690 ) (295,666 ) Future development costs (116,591 ) (244,784 ) (185,188 ) Future income taxes — (121,192 ) (37,404 ) Future net cash flows 199,565 972,738 725,369 10% annual discount (71,880 ) (424,176 ) (274,189 ) Standardized measure of discounted future net cash flows $ 127,685 $ 548,562 $ 451,180 Changes in Standardized Measure Year Ended December 31, 2015 2014 2013 Standardized measure at beginning of year $ 548,562 $ 451,180 $ 230,823 Sales and transfers of oil and gas produced, net of production costs (55,849 ) (173,540 ) (134,184 ) Changes in price, net of future production costs (267,710 ) 37,204 55,601 Extensions and discoveries, net of future production and development costs 70,928 237,290 70,181 Changes in estimated future development costs, net of development costs incurred during this period 31,007 11,094 (25,389 ) Revisions of quantity estimates (14,427 ) 25,591 58,508 Accretion of discount 60,071 47,130 23,776 Net change in income taxes 52,149 (32,034 ) (13,182 ) Purchase of reserves in place — — 191,964 Sale of reserves in place (194,454 ) (7,240 ) (411 ) Changes in production rates (timing) and other (102,592 ) (48,113 ) (6,507 ) Net increase (decrease) in standardized measure (420,877 ) 97,382 220,357 Standardized measure at end of year $ 127,685 $ 548,562 $ 451,180 The historical twelve-month average prices of oil, gas and natural gas liquids used in determining standardized measure were: 2015 2014 2013 Oil, $/Bbl $50.29 $96.45 $106.19 Ngls, $/Mcfe 2.24 4.11 5.10 Natural Gas, $/Mcf 2.41 3.80 3.11 |