Supplemental Cash Flow Disclosure (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash paid during the period for:
Interest	$ 2,770	$ 645
Non-cash transactions:
Increase in asset retirement obligations	3,590	5
Decrease in accounts payable and accrued liabilities included in oil and gas properties	(491)	(12)
Non-cash acquisition of Carbon California interests (see note 3)	(18,906)
Carbon California Acquisition on February 1, 2018 (see note 3)	17,114
Obligations assumed with Seneca asset purchase (see note 2)	330
Accrued dividend for convertible preferred stock (see note 9)	148
Beneficial conversion feature for convertible preferred stock (see note 9)	1,125
Issuance of warrants for investment in affiliates		7,094
Exercise of warrant derivative (see note 3)	$ (1,792)