Clay-induced permeability decline in sandstone reservoirs: Insights from a coupled NMR-SEM experimental approach

The blockage induced by solid particles transport and deposition is one of the main causes of injectivity decline in geothermal sandstone reservoirs during reinjection. This paper investigates clay-induced clogging mechanisms to provide a better understanding to formation damage problems encountered in geothermal fields. In-depth NMR measurements were carried out during core-flooding experiments where illite clay particles (120 nm) were injected in sand-packed columns. SEM imaging was performed to compare the porous space before and after damage and study the morphology and distribution of the deposited particles in the sand column. Pressure drop measurements and NMR T2 relaxation time distributions revealed that clogging occurs in two stages: surface deposition and pore bridging. This was further confirmed by SEM images showing that pore-blocking illite ribbons were formed in the porous space.

Automated summary

This paper investigates the clogging mechanisms caused by clay particles in geothermal sandstone reservoirs. The results suggest that clogging occurs in two stages: surface deposition and pore bridging. SEM images provide further evidence of pore-blocking clay ribbons.