Active Magnetic Ranging From Drill String for Geothermal Systems

Abstract Many advanced geothermal systems require drilling deep connected closed loop wells. These wells are connected by a series of parallel horizontal well sections pairs for heat transfer from the formations. The separation of these wells, and the distance between them, must be controlled in the drilling operation to ensure efficient heat transfer. Active Magnetic Ranging (AMR) is an oilfield drilling measurement technique developed for efficient relief well drilling and to drill well sections within a conglomerate of old wells without hitting any existing wells. Different to traditional ranging systems where the ranging is performed using a wireline operation, an AMR system integrates the logging system onto the drill string bottom hole assembly. Such a method would save several rig days as the tripping operations can be avoided. The active magnetic ranging tool emits an alternating current into the formation. This will reach the target well and then run through steel casing/tubulars and finally return to the well being drilled. This current sets up a variable magnetic field that is measured by the AMR tool determining the direction towards the target well as well as the distance. Traditionally, if drilling a relief well without an active magnetic ranging tool on a drill pipe, 10 – 25 wireline runs are needed before the target well is intercepted. The present tool allows similar operations using an integrated tool systems in the drill pipe and, thus, avoid all the tripping operations necessary when running wireline operations. In this paper we present assessment to optimize performance of this tool. Both experiments and simulations are applied in this analysis.