Note 9 - Supplemental Information Relating to Oil and Gas Producing Activities (Unaudited) - Standardized Measure of Discounted Future Net Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Future cash inflows from sales of oil and gas	$ 17,014	$ 23,821
Future production and development costs	(10,853)	(15,446)
Future asset retirement obligations, net of salvage	(16,451)	(16,443)
Future income tax expense	(95)	(144)
Future net cash flows	(10,385)	(8,212)
Effect of discounting future net cash flows at 10% per annum	461	1
Standardized measure of discounted future net cash flows	$ (9,924)	$ (8,211)	$ 28,157