The goal of the development of reactive percolation tests in fracture under Thermo-Hydro- Mechanical conditions is to improve the understanding of fluid/rock interactions and their role on the fracture permeability evolutions. Indeed, these permeability evolutions of the fractures are a key point in the life duration of a geothermal exchanger in EGS (Enhanced Geothermal System) sites.
In the framework of the development of EGS (Enhanced Geothermal System) technology, a better understanding of fluid/rock interactions in the deep fractured reservoir will allow to improve the management of the heat exchanger and to optimize its life duration. Indeed, beyond the stimulation step of the reservoir, the evolution of fracture permeability is strongly related to chemical processes due to fluid/rock interactions in a system with varying mechanical, hydraulic and thermic conditions, depending on the distance from injective and productive wells. These chemical processes can lead either to an increase of the permeability, due to dissolution phenomenon, or to a decrease of the permeability because of precipitation phenomenon. This is to improve the understanding of these fluid/rock chemical interactions and their impact on the fluid flow in the fracture that reactive percolation tests in fracture in Thermo-Hydro-Mechanical (THM) conditions are developed.
The principle of the reactive percolation test is to performa fluid flow in a fracture of a rock sample in THM conditions determined and controlled (Fig. 1):
A cylindrical rock sample is drilled to get the mean plane of the fracture perpendicular to the axis of revolution;
A normal stress is applied to the rock sample, perpendicular to the fracture plane;
The fluid, whose chemical composition is calculated, is injected with a determined flow rate at the center of the fracture. In the fracture, the flow is radial divergent. The fluid, flowing through the fracture, is collected in an annulus tank surrounding the rock sample.