Results of Operations Year ended December 31, 2020 compared to the year ended December 31, 2019 (1) Barrels of oil equivalent have been calculated on the basis of six thousand cubic feet (Mcf) of natural gas equals one barrel of oil equivalent (BOE). 49 Years Ended December 31, 2020 2019 Change Sales volumes: Oil (MBbl) 3,180  3,086  3  % Natural gas (MMcf) 7,282  4,760  53  % Natural gas liquids (MBbl) 1,198  1,022  17  % Barrels of oil equivalent (MBOE)  5,591  4,902  14  % Average daily production (BOE per day) 15,276  13,429  14  % Average prices realized: Oil (per Bbl) $ 37.85  $ 55.71  (32) % Natural gas (per Mcf) $ 1.18  $ 0.82  44  % Natural gas liquids (per Bbl) $ 13.03  $ 15.09  (14) % Average prices adjusted for realized derivatives settlements: Oil ($/Bbl) $ 54.95  $ 59.82  (8) % Natural gas ($/Mcf) $ 1.42  $ 1.49  (5) % Natural gas liquids ($/Bbl) $ 13.03  $ 15.09  (14) % (In thousands) Oil revenues $ 120,355  $ 171,925  (30) % Natural gas revenues 8,567  3,913  119  % Natural gas liquids revenues 15,601  15,424  1  % Total revenues $ 144,523  $ 191,262  (24) % Lease operating expense $ 29,131  $ 28,683  2  % Production and ad valorem taxes $ 9,411  $ 11,871  (21) % Impairment expense $ 64,498  $ —  NM Depreciation, depletion and amortization $ 96,414  $ 69,243  39  % General and administrative expense (excluding stock-based compensation) $ 18,179  $ 18,963  (4) % Stock-based compensation $ 10,054  $ 8,648  16  % General and administrative expense $ 28,233  $ 27,611  2  % Transaction costs $ 622  $ 1,077  (42) % Gain on sale of oil and gas properties, net $ 204  $ 3,222  (94) % Interest expense, net $ (5,232) $ (6,566) (20) % Write-off of deferred financing costs $ —  $ (1,242) NM Unrealized gain (loss) on derivative contracts $ 3,855  $ (59,849) (106) % Realized gain on derivative contracts $ 56,044  $ 15,866  253  % Gain (loss) on derivative contracts, net $ 59,899  $ (43,983) (236) % Income tax benefit (expense) $ 112  $ (1,665) (107) % (1)