Preliminary experimental set-up for the investigation of colloid/nanoparticle transport in fractures of hydrothermally altered granite

Abstract

Colloidal material may influence different processes in the exploration and exploitation of geothermal reservoirs. For example, colloids in heavy drilling mud may clog naturally permeable structures or naturally occurring colloids may represent nuclei for scales or form scaling themselves. Therefore, the interaction between colloids and water-effective migration pathways is essential to describe transport processes in geothermal systems. The overall aim of this study is to elucidate the influence of the surface roughness, flow channel geometry, surface charge and clay content in fractures on the transport behavior of colloids and possible reduction in permeability and porosity caused by the immobilization of these particles or secondary phase formation. Migration experiments in drill cores, which contain natural water-bearing fractures or mechanically induced fractures (by means of tri-axial tests) shall be conducted by using a bottom-up methodical approach. These flow and colloid transport processes will be examined by drill core experiments (including natural fracture geometry) using differently altered granite samples (from geothermal reservoir rocks from Soultz-sous-Forêts (France) and rocks from the Grimsel Massive (Switzerland). The experimental work is accompanied by 3-D flow and mass transport modeling using commercial software packages (ANSYS Fluent/COMOSL Multiphysics).