43 CFR 3252.12: How deep may I drill a temperature gradient well?

(a) You may drill a temperature gradient well to any depth that we approve in your exploration permit or sundry notice. In all cases, you may not flow test the well or perform injection tests of the well unless you follow the procedures for geothermal drilling operations in subparts 3260 through 3267.

(b) BLM may modify your permitted depth at any time before or during drilling, if we determine that the bottom hole temperature or other information indicates that drilling to the original permitted depth could directly encounter the geothermal resource or create risks to public health, safety, property, the environment, or other resources.