Particle migration and formation damage during geothermal exploitation from weakly consolidated sandstone reservoirs via water and CO2 recycling

Abstract

Coupled migration and retention of suspended injection particles and reservoir particles can severely damage the formation, especially for weakly consolidated sandstone geothermal reservoirs. Understanding their migration and retention is significant to prevent undesired formation damage. The forces acted on these particles were calculated, and then a comprehensive simulation model was established to analyze the coupled particle migration and retention. Massive detachment of reservoir particles, formation of wormhole-like preferential flow paths, and retention of the injected suspended particles are identified as three successive stages during geothermal energy exploitation via water recycling. The mobile reservoir particles play a leading role in the first two stages, while the injected suspended particles mainly affect the last stage. Sensitivity analysis indicates that the high injection-production pressure difference and low concentration of injected suspended particles are conducive to form preferential flow paths, but a severe local reservoir blockage may occur under high mobile reservoir particles. CO2 can effectively reduce reservoir damage caused by particle migration due to its high mobility and low drag force. Although the region of reservoir particle detachment is large during geothermal energy exploitation via CO2 recycling, more preferential flow paths can form to reduce the formation blockage caused by particle migration.