Migration of mineral particles and mechanism of injection plugging during CO2 geological storage in low-permeability reservoirs

Abstract

CO2 geological storage in low-permeability sandstone reservoirs is one of the effective means to realize CO2 capture, utilization and storage (CCUS). As CO2 continues to be injected into the absorbing layer, some weakly cemented sandstone particles will migrate with CO2 in pores and fractures. Particle accumulation is formed, which affects the stability of CO2 injection. In order to reveal the dynamic accumulation and microscopic mechanism of polymorphic sandstone particles, a discrete element fluid-solid coupling injection plugging model based on polymorphic sand particles was established. The model considers mineral particle parameters, such as multi-level particle size, irregular shape, and rotation, and fluid physical properties, such as fluid density and fluid velocity. The model can realize the dynamic prediction of the transient accumulation process of injected fluid and mineral particles. The quantitative relationship among CO2 physical properties, weakly cemented irregular sand parameters and injection plugging efficiency was revealed. The results indicate that: ① the highest factor affecting the accumulation of mineral particles is the concentration of mineral particles. The particle concentration of 5% increases the accumulation of mineral particles in pores by 52.06% compared with the particle concentration of 3%. There is a negative correlation between the increase rate of particle accumulation and the increase rate of mineral particle concentration; ② In the case of the same amount of injected CO2 and mineral particles, the accumulation is the highest when the average size of particles is 1/3 of the pore diameter. Small changes in mineral grain density have less impact on the CO2 injection. ③ The CO2 injection reduces the density of multiphase fluid in the sandstone pores, reduces the blockage of irregular mineral particles in the pores. ④ The CO2 injection rate increases by 60%, and the accumulation of mineral particles in the pores increases by 1.2%. The increase of injection velocity increases the plugging ratio of mineral particles in the pores, which is not conducive to the injection of CO2.

Keywords

• co2 injection
• weakly cemented sand grains
• pores
• dynamic transport model
• injection plugging mechanism