Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Revenue Percentage Accounted by Purchasers

For the years ended December 31, 2019, 2018 and 2017, the following customers accounted for more than 10% of the Company’s revenue:

	Year Ended December 31,
	2019	2018	2017
Shell Trading (US) Company	55%	53%	62%
Lion Oil, Inc.	30%	22%	3%
Targa Pipeline Mid-Continent, LLC	8%	11%	13%

Summary of Changes in Asset Retirement Obligations

The following table summarizes the changes in the Company’s asset retirement obligations for the periods indicated (in thousands):

	Year ended December 31,
	2019			2018
Asset retirement obligations, beginning of year	$	26,884		$	27,170
Additional liabilities incurred	1,490			2,111
Dispositions of wells	(339		)	(3,557		)
Accretion expense	1,465			1,422
Liabilities settled upon plugging and abandoning wells	(484		)	(262		)
Revision of estimates	(5,577		)	—
Asset retirement obligations, end of year	$	23,439		$	26,884

Exploration Costs

	Year Ended December 31,
	2019		2018		2017
Leasehold abandonments and impairments	$	99,225	$	160,834	$	32,872
Geological and geophysical costs	978		1,479		5,429
Other	8		226		1,044
Total exploration and abandonment costs	$	100,211	$	162,539	$	39,345