World Geothermal Congress 2020+1
March - October, 2021

Hydrothermal Simulation in a Fault Zone: Impacts of Stimulation Methods


[BRGM, France]

The H2020-DEEPEGS project aims to demonstrate the feasibility of the Enhanced/Engineered Geothermal System Technology (EGS) to produce electricity and/or heat. One of the main technological challenge is to optimise the well architecture and stimulation methods to get economically viable flow rate in deep hot reservoir initially little productive (Peter-borie et al., 2020). The main idea of this work is to provide an overview of the impact of different stimulation methods considered to enhance the productivity of the targeted reservoir of an EGS demonstrator. The targeted fault zone is located in the granitic basement of the Upper Rhine Graben (eastern France), at around 4 400m TVD where the temperature is estimated around 200°C. Based on the drill data recorded and structural hypothesis hinging on a multiscale approach, a conceptual model of the faulted geothermal reservoir is established. Then, a hydrothermal model of the fault zone is built. The numerical model is developed using the ComPASS code that enables the implementation of 2D discrete fracture or fault network coupled with the surrounding 3D matrix (so-called hybrid-dimensional model). The current code is able to handle compositional multiphase Darcy flows, relying on a Coats type formulation, coupled to the conductive and convective transfers of energy (Lopez et al., 2018). The impact of the different technologies used to enhance the injectivity of the well such as stimulation methods (the hydraulical and thermal stimulations are considered) or such as a multi-drain well geometry are studied through the simulation of an injection test. The effect of soft hydraulic stimulation resulting from the hydromechanical simulations (Blaisonneau et al., 2020a) is implemented into the hydrothermal model through the modification of the fractured reservoir properties. In parallel based on the same hydrothermal model the impact of multi-drain well geometry is studied. For each stimulation method, the injectivity can be compared with the initial model and the relative efficiency of each stimulation method can be assessed. Based on the thermal fields (for each case) resulting from the hydrothermal simulations and using the results provided by the thermomechanical models Tran et al., (2020), the permeability variations (around the well and the matrix surrounding the fractures) will be implemented into the hydrothermal model in order to assess the impact of thermal stimulation. The main aim of this study is to integrate the impacts of different stimulation methods into an unique hydrothermal model in order to test different scenarios of stimulation and assess their respective impacts. The final goal of this work is to provide numerical tools in order to investigate the relative efficiency of stimulation methods in the context of EGS.

        Topic: EGS - Enhanced Geothermal Systems Paper Number: 31057

         Session 16P: Poster 4 [Tuesday 6th July 2021, 11:00 pm] (UTC-8)
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