Active magnetic ranging while drilling: A down-hole surroundings mapping

Active magnetic ranging (AMR) while drilling is an electromagnetic method used to map subsurface ground by its conductivity. Subsurface mapping is needed both in the oil and gas industry and in the geothermal drilling industry. In both cases, several wells are drilled close to each other to exploit the full potential of either an oil reservoir or a geothermal reservoir. The challenge however with subsurface mapping compared to thin air radar mapping is the very low skin depth given by the high conductivity of the ground. For that reason, existing systems are often limited to very short range operations.In this paper methods for range improvement are presented. To maximize the range potential the frequency of operation is reduced, and the efficiency and size of the antennas are increased as much as possible.