Impact of an uncertain structural model on geothermal reservoir simulations

Abstract

Numerical reservoir models are usually based on geological and structural models. Geological and geophysical input for structural models has varying degrees of uncertainty, making the structural model itself uncertain. Usually, however, one single structural model is used for subsequent numerical simulations. We study an ensemble of different, but equally likely structures of a characteristic of geothermal reservoir systems in Tuscany, the K horizon. This horizon is a prominent seismic reflector and usually regarded as a 450 °C isotherm. Here, we present a workflow for assessing the impact of the structural uncertainty of the K horizon. By varying the structure of the K horizon within bounds of its uncertainty, we generate different structural models, which will be used for subsequent hydrothermal simulations. Comparison of simulation results to measured bottom-hole temperatures enables rejecting unlikely K horizon structures, thus reducing the amount of likely structures to a smaller ensemble which fit the temperature data.