Thermally induced permeability reduction due to particle migration in sandstones: the effect of temperature on kaolinite mobilisation and aggregation

The seasonal imbalance in supply and demand of renewable energy requires seasonal storage, which potentially may be achieved by hot water injection in geothermal aquifers to minimize heat loss by advection. A reduction of porosity and permeability is a risk of heating the rock above the in-situ temperature.

Published data indicate that the permeability reduction can be a consequence of the mobilisation of kaolinite particles. Particle mobilisation as a result of changes in physico-chemical conditions is often addressed using the DLVO theory (Derjaguin and Landau, 1941; Verwey and Overbeek, 1948). Mobilisation occurs due to similar surface charges on kaolinite and quartz grains which causes a detachment force on the kaolinite particles.

Permeability reduction as a result of mobilisation requires the released particles to be captured in the pore throats. Data indicate that the permeability reduction can be reversible, implying captured particles are remobilised when the temperature is reduced. This paper considers the effects of mineralogy and hydrodynamic forces on particle mobilisation and aggregation.

The mineral surface charge originates from the interaction between the particles and the saturating fluid and is affected by both the fluid composition and the temperature. Kaolinite particles have a heterogeneous surface charge distribution that can play an important role in the particle aggregation in the pore throats, leading to permeability damage.

The reduction of temperature causes an increase in the hydrodynamic force on the aggregated particles at pore throats. It can remobilise particles and lead to permeability recovery. We discuss the mineral structure of quartz and kaolinite and estimate the effects of heating on the surface charges using published data.

The DLVO theory is used to model the interaction energy between quartz and kaolinite particles for different saturating fluids. The results are compared to the published data addressing the effect of temperature on permeability. This provides a qualitative explanation for the observed changes in permeability with temperature for the tests with distilled water.