Subsequent events (Tables)

6 Months Ended

Jun. 30, 2017

Subsequent Events [Abstract]

New commodity derivative contracts

After June 30,2017, the Company entered into the following oil price swaps and oil basis swaps to hedge additional amounts of the Company’s estimated future production:

				First		Second		Third		Fourth
				Quarter		Quarter		Quarter		Quarter		Total
Oil Price Swaps: (a)
	2017:
		Volume (Bbl)						1,253,000		1,354,000		2,607,000
		Price per Bbl					$	47.76	$	47.73	$	47.74
	2018:
		Volume (Bbl)		1,059,000		869,000		747,000		669,000		3,344,000
		Price per Bbl	$	48.33	$	48.26	$	48.20	$	48.15	$	48.25
	2019:
		Volume (Bbl)		1,002,000		940,000		885,000		845,000		3,672,000
		Price per Bbl	$	49.26	$	49.24	$	49.27	$	49.26	$	49.26
Oil Basis Swaps: (b)
	2017:
		Volume (Bbl)						915,000		1,380,000		2,295,000
		Price per Bbl					$	(1.28)	$	(1.28)	$	(1.28)
	2018:
		Volume (Bbl)		630,000		637,000		644,000		644,000		2,555,000
		Price per Bbl	$	(1.11)	$	(1.11)	$	(1.11)	$	(1.11)	$	(1.11)
	2019:
		Volume (Bbl)		810,000		819,000		828,000		828,000		3,285,000
		Price per Bbl	$	(1.12)	$	(1.12)	$	(1.12)	$	(1.12)	$	(1.12)
(a)	The index prices for the oil price swaps are based on the NYMEX – WTI monthly average futures price.
(b)	The basis differential price is between Midland – WTI and Cushing – WTI.