Particle blockage mechanism of a weakly consolidated sandstone geothermal reservoir during tailwater recharge

Abstract

Weakly consolidated sandstone geothermal reservoirs (WCSGR) are widely distributed, highly developed and utilized, with tremendous potential to meet enormous energy needs. However, this kind of geothermal reservoir (GR) suffer from permeability damage during tailwater recharge, primarily due to particle blockage (PB). The exact impact of PB on the permeability of GRs during tailwater recharge remains unclear. Therefore, an experimental study investigating PB in WCSGR tailwater recharge was conducted, considering the comprehensive effects of multiple factors. The study aimed to understand the mechanism of PB and its effect on GR permeability by observing the migration of fluorescent particles in sandstone core. Through analysis of microsphere migration/blockage properties, theoretical calculations, and empirical criteria, the PB mechanism during tailwater recharge in weakly consolidated sandstone was revealed. A physical model of particle movement was developed to explain the permeability attenuation phenomena in the experimental cores, describing the occurrence and development process of PB in real recharge operations. Finally, the theoretical computation were integrated with the experimental findings, and the chemical and dynamic conditions of geothermal tailwater recharge in the WCSGR were optimized. This study provides theoretical guidance for further numerical simulations and field tests.