Study of Thermo-Mechanical Damage around Deep Geothermal Wells: from the Micro-Processes to Macroscopic Effects in the Near Well

Abstract : The different processes involved in the life of a geothermal well, from drilling to exploitation, can damage the rock mass in the near well area. In this paper, we propose to study the potential damage linked to the mechanical and thermo-mechanical effects of the well drilling, the well development and the well exploitation. The cooling of the rock mass of the near well pre-damaged by drilling process is a complex phenomenon with the superimposition of different kind of loadings at different scale that lead us to use modeling with a micro-macro approach. To confront the results of the modeling with the reality, we propose to base our study on real cases. For studying mechanical and thermo-mechanical loadings due to drilling and development of the well, we focus our study on the granitic reservoir exploited in the framework of the enhanced geothermal system (EGS) of Soultz-sous-Forêts (France). The study of the thermo-mechanical loading due to well exploitation is performed for a sandstone in the conventional heat exploitation of Melleray (Loiret, France). These simulations highlight the thermo-mechanical damage of a geothermal well linked to the different steps of its life.