Abstract
Closed loop geothermal applications allow energy production also outside geothermal sweet spot regions. For these cases it is necessary to drill deep connected closed loop wells. The system consists of series of parallel horizontal well sections pairs, connected at the well toe, for heat transfer from the formations. The separation of these wells, and the distance between them, must be accurately controlled in the drilling operation to ensure efficient heat transfer. A technique, originally developed for relief well drilling when control has been lost of an oil or gas well, require ranging towards an existing completed wellbore. Active Magnetic Ranging (AMR) is an oilfield drilling measurement technique originally 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 integrate the logging system onto the drill string bottom hole assembly. Such method would save several rig days as the trip-out operations can be skipped. Saving rig days is certainly desired in any drilling operation. For geothermal applications, where the financial conditions are far less prosperous than traditional oil&gas developments, such improvements are crucial even to justify the development. A ranging system for use on the bottom hole assembly has been tested out at a full-size drilling rig, a research test site and in laboratories. Tests in various formations verify the applicability of the ranging system. Both high resistive and low resistive formations are used and for all the cases targets were identified. This shows that the system has potential to enable applicable closed loop geothermal systems. In this paper we present status of the development with selected test results and simulations. Measured distances and positions of target wells at test sites are included. The corresponding simulations and design optimization are shown.