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* Corresponding author 1 BRGM - Bureau de Recherches Géologiques et Minières

Abstract : In this paper, we build a 3D stress model of a region in the Upper Rhine Graben. The model relies on a mechanical code based on the Distinct Element Method 3DEC TM which allows taking multiple fault zones into account. Under the influence of the fault network, horizontal stress redistributions occur within the rock mass and result in areas of greater or lesser compression. In addition, the dilatant nature of the fault zones is reproduced by the chosen law of behavior, and causes the opening of the faults under shearing. The ultimate goal of the model is to improve the exploration phase for deep seated geothermal systems by highlighting areas where the mechanical conditions favor the presence of geothermal resources. To achieve this goal, the model needs to be further tested regarding its assumptions on the geometry, mechanical behavior, boundary conditions and initial state. 1. INTRODUCTION The economic viability of heat extraction from Earth-s subsurface mainly relies on two physical properties: temperature and intrinsic permeability. Few sites exhibit such favorable conditions at reasonable drilling depths and the widespread use of geothermal energy production requires targeting deeper resources. The uncertainties on the resource at depth bring a non-negligible risk of targeting error for the wells which, given the high drilling costs, can jeopardize the worldwide generalization of geothermal projects. To address this issue, the Seventh Framework Programme project IMAGE aims at enhancing the exploration techniques in order to significantly reduce the pre-drill uncertainties. The three main goals of the project are: 1. better understand the processes controlling the spatial distribution of exploration parameters, 2. improve the exploration methods already in use and propose new ones, and 3. integrate the existing and newly acquired data in order to provide predictive models to help with choosing exploration areas. To reach the first goal, information should be acquired from and cross-correlated between as many disciplines as possible geology, geophysics, geomechancis,

Keywords : Enhanced Geothermal Systems exploration geomechanics regional stress heterogeneities fault zones Distinct Element Method

Autor: Théophile Guillon - Mariane Peter-Borie - Sylvie Gentier - Arnold Blaisonneau -



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