Abstract
To achieve proper efficiency, for some geothermal applications it is necessary to drill 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 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.
We have conducted test rig experiments using a full-size drilling rig. Several test wells are drilled on this location for testing different types of drilling equipment. At the depth used in the tests the formation consists of a gneiss. A gneiss would represent typical low porosity and low permeable formations with poor electrical conductivity that is a representative model formation for geothermal heat transfer formations. Possibly because of the low conductivity false measurements can be obtained — so-called Ghost Targets.
In this paper we present an analysis of how ghost targets can look like. Furthermore, it is outlined how to distinguish ghost targets from real targets and how to design systems to reduce the impact of such ghosts.
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 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.
We have conducted test rig experiments using a full-size drilling rig. Several test wells are drilled on this location for testing different types of drilling equipment. At the depth used in the tests the formation consists of a gneiss. A gneiss would represent typical low porosity and low permeable formations with poor electrical conductivity that is a representative model formation for geothermal heat transfer formations. Possibly because of the low conductivity false measurements can be obtained — so-called Ghost Targets.
In this paper we present an analysis of how ghost targets can look like. Furthermore, it is outlined how to distinguish ghost targets from real targets and how to design systems to reduce the impact of such ghosts.