Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 58		$ 1,606
Accrued production receivable	146,334		124,936
Trade and other receivables, net	45,193		43,900
Other current assets	10,670		10,684
Total current assets	202,255		181,126
Oil and natural gas properties (using full cost accounting)
Proved properties	10,775,792		10,419,827
Unevaluated properties	951,397		927,819
CO2 properties	1,191,058		1,188,467
Pipelines and plants	2,286,047		2,285,812
Other property and equipment	339,218		378,776
Less accumulated depletion, depreciation, amortization and impairment	(11,376,646)		(11,212,327)
Net property and equipment	4,166,866		3,988,374
Other assets	102,178		105,078
Total assets	4,471,299		4,274,578
Current liabilities
Accounts payable and accrued liabilities	177,220		200,266
Oil and gas production payable	76,588		80,585
Derivative liabilities	99,061		69,279
Current maturities of long-term debt (including future interest payable of $75,347 and $50,349, respectively – see Note 5)	105,188	[1]	83,366
Total current liabilities	458,057		433,496
Long-term liabilities
Long-term debt, net of current portion (including future interest payable of $241,472 and $178,476, respectively – see Note 5)	2,979,086		2,909,732
Asset retirement obligations	165,756		146,807
Deferred tax liabilities, net	198,099		293,878
Other liabilities	22,136		22,217
Total long-term liabilities	3,365,077		3,372,634
Commitments and contingencies (Note 11)
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; 402,549,346 and 402,334,655 shares issued, respectively	403		402
Paid-in capital in excess of par	2,507,828		2,534,670
Accumulated deficit	(1,855,810)		(2,018,989)
Treasury stock, at cost, 457,041 and 3,906,877 shares, respectively	(4,256)		(47,635)
Total stockholders' equity	648,165		468,448
Total liabilities and stockholders' equity	$ 4,471,299		$ 4,274,578

[1] Future interest payable represents most of the interest due over the term of our 9% Senior Secured Second Lien Notes due 2021 (the “2021 Senior Secured Notes”), 9¼% Senior Secured Second Lien Notes due 2022 (the “2022 Senior Secured Notes”) and 3½% Convertible Senior Notes due 2024 (the “2024 Convertible Senior Notes”), which has been accounted for as debt in accordance with FASC 470-60, Troubled Debt Restructuring by Debtors. Our current maturities of long-term debt as of December 31, 2017 include $75.3 million of future interest payable related to these notes that is due within the next twelve months. See December 2017 and January 2018 Note Exchanges below for further discussion.