Abstract
The use of the subsurface and the exploitation of subsurface resources require prior knowledge of fluid flow through fracture networks. For nuclear waste disposal, for the enhancement of hydrocarbon recovery from a field, or the development of an enhanced geothermal system (EGS), it is fundamental to constrain the fractures and the fracture network. This study is part of the GEMex project, an international collaboration of two consortia, one from Europe and one from Mexico. The research is based on exploration, characterization and assessment of two geothermal systems located in the Trans-Mexican volcanic belt, Los Humeros and Acoculco. In Acoculco, two wells reached very high temperatures, but did not find any fluids. For that reason, the Acoculco Caldera is foreseen as an EGS development site, hoping to connect existing wells to a productive zone. This implies that the fluid flow through the geothermal reservoir would be mainly fracture dominated. This study investigates the dependency of fracture permeability, constrained by fracture lengths and apertures, with stress field conditions. Simulations are computed in 2D, using COMSOL Multiphysics^{textregistered } Finite Elements Method Software, populated with mechanical data obtained in the rock physics laboratory and with dense discrete fracture networks generated from 1D scanline surveys measured in Las Minas analogue outcrops for Acoculco reservoir. The method offers a prediction for multiple scenarios of the reservoir flow characteristics which could be a major improvement in the development of the EGS technology.
Highlights
BackgroundThe understanding of fractures is crucial for several subsurface activities such as oil and gas, nuclear waste disposal, enhanced geothermal system or C O2 sequestration (Fox et al 2015)
Two main methods are commonly used to predict the impact of the Lepillier et al Geotherm Energy (2019) 7:24 fractures: one method is using a discrete fracture model (DFM) and the second method is using a continuum described as the representative volume element (RVE) (Geiger and Matthäi 2012; Surrette 2006)
When developing subsurface activities such as oil and gas, nuclear waste disposal, CO2 sequestration or, as in this case, enhanced geothermal system, it is fundamental to quantify the role of the fracture system present in the subsurface
Summary
BackgroundThe understanding of fractures is crucial for several subsurface activities such as oil and gas, nuclear waste disposal, enhanced geothermal system or C O2 sequestration (Fox et al 2015). Two main methods are commonly used to predict the impact of the Lepillier et al Geotherm Energy (2019) 7:24 fractures: one method is using a discrete fracture model (DFM) and the second method is using a continuum described as the representative volume element (RVE) (Geiger and Matthäi 2012; Surrette 2006). In the second case, using RVE consists of modelling the bulk impact of the fractures on the reservoir properties. These properties are averaged to represent the matrix and the fractures together in a continuum model (Flemisch et al 2018; Singhal and Gupta 2010; Surrette 2006; Dershowitz et al 2004). The characterization of the fractures is, of utmost importance to the results
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