20x local background levels28 Jan 2024 13:40
"the helium content of the drilling mud is determined and monitored, either intermittently or continuously, during drilling operations.
the background level of helium is established during the early stages of drilling the well. This background level may not be constant, but can vary gradually during the drilling operation.
the average helium content of the drilling fluids from the upper strata are assumed to be the normal helium background level. Moderate increases in the helium content over the background level indicate faulted strata. Further increases in helium content indicate that the drill bit is approaching a geothermal reservoir."
From the Google read. Thanks Chesh.