Optimal Experimental Design (OED) for Finding Optimally Located Boreholes in Geothermal Engineering

Abstract

An obstacle for further commercial utilization of deep geothermal resources is the high cost for deep drilling in regard to the productivity risk of a well. Minimizing the risk by optimizing the location of a well is thus a question of primary importance. For a given geological model of a reservoir, we demonstrate how this problem may be tackled by a mathematical optimization approach called optimal experimental design. We show how this problem can be mathematically derived, numerically formulated, and practically implemented using distributed computing. We discuss an example for a sedimentary geothermal reservoir in Western Australia with six lithological units. We show how optimized positions of bore holes can be determined such that uncertainty of estimating the hydraulic permeability of a target rock unit from temperature measurements is minimized. We discuss different optimality criteria and the influence of different a priori permeabilities in the various rock units.