Impact of Carbonate Precipitation Morphology on Reinforcement and Sand Control Efficiency of MICP-Treated Reservoirs Following Hydrate Dissociation

Abstract

Sand production induced by hydrate dissociation severely threatens the safe and sustainable exploitation of weakly cemented marine hydrate reservoirs. Microbially induced carbonate precipitation (MICP) has emerged as a promising in situ sand-control technique; however, its reinforcement effectiveness is governed not only by carbonate content but also by the spatial occurrence morphology of carbonate precipitation. Yet, the underlying mechanisms through which carbonate morphology regulates mechanical behavior, particle migration, and seepage characteristics remain poorly understood. In this study, a multiscale numerical framework integrating discrete element method (DEM)-based triaxial compression simulation, CFD–DEM fluid–particle coupling analysis, and OpenPNM pore network reconstruction was developed to systematically investigate the reinforcement, sand-control, and permeability responses of four idealized carbonate occurrence morphologies, including bridging cementation, contact cementation, grain coating, and pore filling. The results demonstrate that carbonate occurrence morphology is a critical determinant of the mechanical response of MICP-treated sediments. The enhancement in shear strength arises primarily from increased interparticle cohesion, whereas the frictional characteristics remain relatively unchanged. Among the morphologies examined, bridging cementation exhibits the most significant strengthening effect, increasing cohesion by up to 593.3%. In terms of sand-control performance, bridging and contact cementation reduce sand production by 93.46% and 81.91%, respectively, at a carbonate content of 4%. In contrast, grain coating and pore filling fail to establish continuous interparticle bonding networks and may even promote particle migration at low carbonate contents, showing limited sand-control effectiveness only after exceeding a critical carbonate content of approximately 3.5%. Further analysis reveals that the superior performance of bridging cementation originates from the formation of a cross-particle carbonate network, which enhances structural connectivity and improves resistance against hydraulic disturbance. Permeability analysis indicates that excessive contact cementation causes more severe flow impairment due to carbonate accumulation around particle contacts, resulting in a higher flow-loss rate (29.3%) compared to bridging cementation (27.6%). Overall, bridging cementation provides the best balance among mechanical reinforcement, sand-control efficiency, and permeability preservation under the investigated conditions. This study highlights that the spatial topology of carbonate precipitation, rather than carbonate quantity alone, governs the effectiveness of MICP reinforcement and provides theoretical guidance for optimizing MICP treatment strategies to promote favorable carbonate bridging structures in hydrate-bearing sediments.