Mechanism of sediment dynamic behavior during marine gas hydrate production: The role of fines

Marine gas hydrates are commonly found in sediments rich in fines or in mixtures of fine and coarse-grained sediments; consequently, the macroscopic properties of these reservoirs are controlled by fines dynamics, which in turn are governed by pore fluid chemistry. However, the impact of pore fluid chemistry changes on the migration and sedimentation of fine-grained sediments has not been extensively considered to date. Therefore, this study employed a high-pressure, low-temperature hydrate reactor to observe the dynamic sedimentation behavior of fines (montmorillonite and mica) during pore fluid chemical changes in the presence of hydrates. It was found that montmorillonite with a high electrical sensitivity index (SE characterizing their responsiveness to pore fluid chemical changes) exhibits increased sedimentation rates in brine solutions, while low-SE mica demonstrates the slowest sedimentation in brine conditions. Furthermore, low-field nuclear magnetic resonance (LNMR) coupled with dynamic fines. Migration experiments investigated sedimentation behavior and pore structure response mechanisms under varying pore fluid chemistry. Results indicate that higher SE of fines correlates with more pronounced migration behavior and porosity variations in fine-grained sediments under flowing pore fluids. This study reveals the influence of pore fluid chemistry on fines dynamic behavior, establishing an intrinsic relationship between fines dynamic behavior and SE.