Note 8 - Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2018

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of June 30, 2018
Assets:
NYMEX fixed price derivative contracts	$	-	$	-	$	-	$	-
Total Assets	$	-	$	-	$	-	$	-
Liabilities:
NYMEX fixed price derivative contracts	$	-	$	32,329	$	-	$	32,329
Total Liabilities	$	-	$	32,329	$	-	$	32,329

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2017
Assets:
NYMEX fixed price derivative contracts	$	-	$	-	$	-	$	-
Total Assets	$	-	$	-	$	-	$	-
Liabilities:
NYMEX fixed price derivative contracts	$	-	$	13,208	$	-	$	13,208
NYMEX basis differential swap		-		-		16		16
Total Liabilities	$	-	$	13,208	$	16	$	13,224

Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

Unobservable inputs at January 1, 2018	$	(16	)
Changes in market value		—
Settlements during the period		16
Unobservable inputs at June 30, 2018	$	—