Active Magnetic Ranging Solution While Drilling for Geothermal Loop: Test in Low-Conductive Formation

In the enterprise of creating a geothermal loop deep in a formation it may be necessary to drill an intercept with another well. This intercept has some similarities with the well intercept needed when drilling a relief well in cases of blow out of gas or oil wells. At the same time, it is necessary to avoid colliding with the other well prior to reaching the intercept point. A constant distance may be required to the other well at some well depths. A prototype of a tool for Active Magnetic Ranging While Drilling (AMR) without the use of a wireline operation has been developed to navigate for distance control or intercept. The main scope of the current article is to present the results of a prototype test of this new tool in a test well suitable to simulate geothermal well. The ranging tool emits a low frequency alternating current into the formation to reach the target well. The current then run down the target well’s casing and back to the well being drilled. This electric current set up a variable magnetic field that is measured by the AMR tool determining the distance to and the direction towards the target well. Hence, the tool facilitates drilling radiator shape multi-lateral well paths. If drilling an intercept at the end of the radiator sections, 10 - 25 wireline runs are needed in each lateral to the target well is intercepted. The present AMR tool is fully integrated in the drill pipe and, thus, all the tripping operations are avoided. A prototype of an active magnetic ranging tool on the drill pipe has been developed. This tool design is outlined in the paper. The focus is given to performance tests conducted in research wells in Norway. A drill pipe is placed in a vertical well drilled in a gneiss formation. This well simulates a target well. The AMR tool was run in a parallel well and the direction and distance to the nearby target well was measured. The gneiss formation would be a tough formation to drill. However, this formation type is suitable for testing drilling in geothermal well formations. The set-up and the results of this logging operation conducted on a drill pipe is described in detail. It is shown how the direction and distance between the two wells are measured using the tool.