Reservoir Characterisation and Numerical Modelling to Reduce Project Risk and Maximise the Chance of Success. an Example of How to Design a Stimulation Program and Assess Fluid Production from the Soultz Geothermal Field, France

Abstract

This paper describes a predictive, fully coupled poro-thermo-elastic numerical model that is specifically developed to evaluate and optimise geothermal reservoir development strategies. This paper illustrates this via an investigation into the role of stimulation to enhance the permeability for economic hot water production from the deep geothermal site at Soultz-sous-Foréts (France). This study integrates four key elements: a natural fracture characterization model, a fluid flow simulation model, a heat transfer model and a stimulation model. Fluid flow is simulated using a finite element based model wherein stresses and temperature are fully coupled to the fluid flow equations. The heat transfer model is based on conductive heat transfer within the reservoir rock, convective (including conduction) heat transfer through the reservoir fluid and time dependent thermal equilibrium between the rock and fluid. The stimulation model integrates shear dilation mechanisms and stress dependent permeabilities. Effective permeability tensors (based on discrete fracture network) are estimated dynamically and are iteratively used to determine the pore pressure, stress and thermal state within the reservoir.