43 CFR § 3252.16
How must I abandon a temperature gradient well?
June 11, 2020
(a) Before abandoning your well, submit a complete and signed Sundry Notice, Form 3260-3, describing how you plan to abandon wells and reclaim the surface. Do not begin abandoning wells or reclaiming the surface until BLM approves your Sundry Notice.
(b) You must plug and abandon your well for permanent prevention of interzonal migration of fluids and migration of fluids to the surface. You must reclaim your well location according to the terms of BLM approvals and orders.