Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Non-cash gain on derivatives	$ 10,286	$ 11,006
Intangibles	215	222
Inventory	23	23
Share-based compensation	690	480
Accruals and other	558	578
Net operating loss	3,172	5,422
Total deferred tax assets	14,944	17,731
Oil and natural gas assets	(32,154)	(29,161)
Other fixed assets	(174)	(198)
Total deferred tax liabilities	(32,328)	(29,359)
Deferred tax liabilities	$ (17,384)	$ (11,628)