Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents		$ 1,747	$ 1,606
Accrued production receivable		118,483	124,936
Trade and other receivables, net		55,653	43,900
Derivative assets		1,062	0
Other current assets		11,324	10,684
Total current assets		188,269	181,126
Oil and natural gas properties (using full cost accounting)
Proved properties		10,475,877	10,419,827
Unevaluated properties		951,220	927,819
CO2 properties		1,187,711	1,188,467
Pipelines and plants		2,285,435	2,285,812
Other property and equipment		373,537	378,776
Less accumulated depletion, depreciation, amortization and impairment		(11,255,392)	(11,212,327)
Net property and equipment		4,018,388	3,988,374
Other assets		102,002	105,078
Total assets		4,308,659	4,274,578
Current liabilities
Accounts payable and accrued liabilities		180,529	200,266
Oil and gas production payable		73,250	80,585
Derivative liabilities		18,799	69,279
Current maturities of long-term debt (including future interest payable of $50,349 and $50,349, respectively - see Note 2)	[1]	83,701	83,366
Total current liabilities		356,279	433,496
Long-term liabilities
Long-term debt, net of current portion (including future interest payable on $178,476 and $178,476, respectively - see Note 2)		2,956,385	2,909,732
Asset retirement obligations		151,390	146,807
Deferred tax liabilities, net		328,786	293,878
Other liabilities		22,060	22,217
Total long-term liabilities		3,458,621	3,372,634
Commitments and contingencies (Note 6)
Stockholders' equity
Preferred stock, $.001 par value, 25,000,000 shares authorized, none issued and outstanding		0	0
Common stock, $.001 par value, 600,000,000 shares authorized; 402,706,108 and 402,334,655 shares issued, respectively		403	402
Paid-in capital in excess of par		2,540,057	2,534,670
Accumulated deficit		(1,997,455)	(2,018,989)
Treasury stock, at cost, 4,403,152 and 3,906,877 shares, respectively		(49,246)	(47,635)
Total stockholders' equity		493,759	468,448
Total liabilities and stockholders' equity		$ 4,308,659	$ 4,274,578

[1] Future interest payable on our 9% Senior Secured Second Lien Notes due 2021 (the “2021 Senior Secured Notes”) represents most of the interest due over the term of this obligation, which has been accounted for as debt in accordance with Financial Accounting Standards Board Codification (“FASC”) 470-60, Troubled Debt Restructuring by Debtors. Our current maturities of long-term debt as of March 31, 2017 include $50.3 million of future interest payable related to the 2021 Senior Secured Notes that is due within the next twelve months.