RE: DM Video11 Jul 2021 12:16
Unlike other gases, helium is more soluble in hot water than in cold water. Therefore, as reservoir water is heated, it scavenges helium which migrates upwardly along gas permeable zones of weakness created by a cooling magmatic body. As a drill bit penetrates through conjugate fractures adjacent to a potential reservoir zone, the helium charged fluids in these fractures mix with the drilling mud and are transported to the surface where they are detected.
To employ the method of the present invention, 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. During monitoring operations, 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. For example, the background level may range from about 5 to about 12 ppm by volume, while faulted strata will have greater than about 12 ppm helium. Helium levels above 20 ppm, generally in the range of 70-1700 ppm, are found in fluids near geothermal reservoirs.
https://patents.google.com/patent/US4378055