Abstract
Aiming at the problems of high clay mineral content in strong water-sensitive reservoirs and easy hydration expansion caused by foreign fluids, a clay inhibitor (silyl quaternary ammonium salt DSC) was prepared using 2-(dimethylamino)-ethyl methacrylate and (3-chloropropyl)-trimethoxysilane as raw materials. This is the first report on the synergistic application of silyl quaternary ammonium salt (DSC) and CO(2) for enhanced oil recovery in strongly water-sensitive reservoirs, realizing the dual effects of clay stabilization and CO(2) seepage enhancement. It is demonstrated that the synergy of DSC/CO(2) increases the oil recovery rate by 47.29% compared to traditional water flooding, with a 0.35 PV delay in gas channeling. The DSC system, composed of DSC, ethylene glycol, inorganic salt, and nonionic surfactant, stabilizes pore structures through synergistic charge neutralization, hydrogen bond inhibition, and electric double-layer compression, with an antiswelling rate of 93.92% and dissolution rate of 5.32%. The study on the synergistic effect of the DSC system and CO(2) found that the CO(2) diffusion coefficient in DSC-saturated cores increased to 9.226 × 10(-9) m(2)/s (16 times higher than that in formation water-saturated cores), the initiation pressure gradient was reduced by 2 orders of magnitude compared with simulated water flooding, and the antiswelling rate decreased by only 13.72% after multiple rounds of flushing in an acidic environment. It was confirmed that DSC reconstructed the pore surface energy through silyl bonding, significantly improving the CO(2) seepage capacity. Nuclear magnetic resonance (NMR) proved from a microscopic perspective that the synergy of DSC and CO(2) increased the recovery rate of the remaining oil in small pores by 25.08%. Macroscopic oil displacement experiments further showed that the total recovery rate of DSC system flooding + gas-liquid alternating flooding reached 62.85%. The proposed technical model of "dual-effect stable flow-synergistic oil recovery-delayed gas channeling" provides a solution with both technical feasibility and economic rationality for the development of low-permeability water-sensitive reservoirs and CO(2) geological storage. Future research will focus on formula optimization and adaptability studies for reservoirs with different clay compositions.