Formation damage induced by clay colloids deposition in Triassic clastic geothermal fields: Insights from an experimental approach

Abstract

Injectivity decline problems are often encountered during geothermal water reinjection into the subsurface despite massive surface filtration. The reinjected water carrying only nano-sized particles at relatively low concentrations causes severe permeability impairment due to pore clogging by the transported particles. To provide a better understanding to injectivity decline problems, this study investigates the impact of clay minerals transport and deposition on formation damage of sandstone reservoirs. To identify the clays potentially responsible for clogging, a mineral characterization of natural samples, collected from a Triassic reservoir located in the Paris Basin (France), was realized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The obtained results show that in this type of sedimentary environments, illite particles are the most abundant clay species that are more likely to be detached from the rock structure and migrate within the geothermal fluid. Illite particles were then used in core-flooding experiments to mimic their reinjection in sandstones under different physico-chemical conditions. The obtained flow curves were further explained by aggregation experiments carried out using the dynamic light scattering (DLS) technique. The results show a clogging-favored tendency promoted mainly by the increase of ionic strength and particle concentration and the decrease of flow rate.