Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 2,812	$ 23,153
Accrued production receivable	100,413	181,761
Trade and other receivables, net	87,093	156,955
Derivative assets	142,846	440,359
Deferred tax assets, net	1,539	0
Other current assets	10,005	10,452
Total current assets	344,708	812,680
Oil and natural gas properties (using full cost accounting)
Proved properties	10,245,195	9,782,337
Unevaluated properties	894,948	918,406
CO2 properties	1,187,458	1,162,538
Pipelines and plants	2,293,219	2,269,564
Other property and equipment	408,194	468,051
Less accumulated depletion, depreciation, amortization and impairment	(9,653,205)	(4,248,652)
Net property and equipment	5,375,809	10,352,244
Derivative assets	0	66,187
Goodwill	0	1,283,590
Other assets	199,307	213,101
Total assets	5,919,824	12,727,802
Current liabilities
Accounts payable and accrued liabilities	253,197	394,758
Oil and gas production payable	87,337	128,170
Deferred tax liabilities	0	81,727
Current maturities of long-term debt	32,481	35,470
Total current liabilities	373,015	640,125
Long-term liabilities
Long-term debt, net of current portion	3,277,866	3,535,900
Asset retirement obligations	138,919	126,411
Deferred tax liabilities, net	853,628	2,694,842
Other liabilities	27,484	26,668
Total long-term liabilities	$ 4,297,897	$ 6,383,821
Commitments and contingencies (Note 10)
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; 354,541,626 and 411,779,911 shares issued, respectively	355	412
Paid-in capital in excess of par	2,353,549	3,230,418
Retained earnings (accumulated deficit)	(1,058,954)	3,392,465
Accumulated other comprehensive loss	0	(209)
Treasury stock, at cost, 3,124,311 and 58,415,507 shares, respectively	(46,038)	(919,230)
Total stockholders' equity	1,248,912	5,703,856
Total liabilities and stockholders' equity	$ 5,919,824	$ 12,727,802