Hydro-mechanical Evolution of Transport Properties in Porous Media: Constrains for Numerical Modeling of Geothermal Systems

Abstract

Quantifying variations of transfer properties of porous material is of interest for geothermal operations. The basic transport properties of the rocks, which are porosity and permeability can affect if not control the reservoir performance. Variations of these properties are a result of the coupled deformation and thermal processes. Significant pore pressure and temperature changes can occur during injection and production of fluid and affect the reservoir performance. However impacts of elastic deformation processes on transfer properties is often dominant compared to the impacts of the thermal processes in the context of geothermal operations. Understanding the coupling between deformation of the porous material and variation of its properties for mass and energy transfer is therefore a major focus for any geothermal operations. Pore pressure changes due to injection or production of fluid have direct impacts on the stress-field within a geothermal reservoir. Deformation of a porous material filled with fluid is based on variations of bulk and pore volumes and affects therefore the basic transport properties of the rock. The phenomena involved in this hydro-mechanical behavior of porous materials are however hard to observe and quantify at the field scale. This is why studies of hydro-mechanical behavior of porous rocks are often conducted at the laboratory scale where impacts can be measured. Variations of the transport properties can be expressed by theoretical formulations based on experimental observations and then integrated into models which can be used to predict reservoir performance at the field scale.