Note 2 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Schedule of Cash, Cash Equivalents and Restricted Cash [Table Text Block]

	As of December 31,
	2022		2021
	(in thousands)
Cash and cash equivalents	$	37,205	$	48,675
Restricted cash - current		222		79
Restricted cash - non-current		1,763		1,752
Abandonment funding		20,586		21,808
Total cash, cash equivalents and restricted cash	$	59,776	$	72,314

Accounts Receivable, Allowance for Credit Loss [Table Text Block]

	Year Ended December 31,
	2022			2021			2020
	(in thousands)
Allowance for bad debt
Balance at beginning of period	$	(5,741	)	$	(2,273	)	$	(1,508	)
Bad debt charges, net of receipts		(3,082	)		(875	)		(1,165	)
Adjustment associated with reversal of allowance on Mutamba receivable		—			—			593
Adjustment associated with Sasol Acquisition		—			(2,879	)		—
Foreign currency gain (loss)		119			286			(193	)
Balance at end of period	$	(8,704	)	$	(5,741	)	$	(2,273	)

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

		As of December 31, 2022
	Balance Sheet Line	Level 1		Level 2		Level 3		Total
		(in thousands)
Assets
Derivative asset	Prepayments and other	$	—	$	102	$	—	$	102
		$	—	$	102	$	—	$	102
Liabilities
SARs liability	Accrued liabilities and other	$	—	$	556	$	—	$	556
		$	—	$	556	$	—	$	556

		As of December 31, 2021
	Balance Sheet Line	Level 1		Level 2		Level 3		Total
		(in thousands)
Liabilities
SARs liability	Accrued liabilities and other	$	—	$	609	$	—	$	609
Derivative liability	Accrued liabilities and other		—		4,806		—		4,806
		$	—	$	5,415	$	—	$	5,415