Аннотация
Abstract High water-cut oilfields account for 70% of the developed oilfields in China, where ineffective water circulation severely restricts the enhancement of crude oil recovery. Performance control and water shutoff technologies serve as critical means to achieve sustainable oilfield development and are of significant importance for improving water flooding performance. A high-strength preformed particle gel (PPG), as an efficient plugging material, have demonstrated excellent performance in water shutoff. Their application in bottom-water reservoirs remains relatively understudied. To enhance the material strength for high-pressure bottom-water reservoirs, a high-strength preformed particle gel (HSPPG) with delayed swelling was developed in this study. Rheological methods were employed to analyze the viscoelastic of HSPPG under different salinities. The microstructural was characterized using cryo-scanning electron microscopy, revealing the strength enhancement mechanism. Long sand packed tube was conducted to evaluate the plugging capacity and flushing resistance of HSPPG. Parallel sand packed tube was used to investigate its fluid diversion, illustrating the mechanism of HSPPG in controlling water coning. Experimental results indicate that the oil-coating treatment introduced during mechanical grinding enabled HSPPG to swell slowly in water, significantly improving its injectivity into formations. As salinity increased from 0 to 9×104 mg/L, the swelling ratio of HSPPG decreased from 4.45 to 3.29, while high mechanical strength was maintained, demonstrating its suitability for high-salinity bottom-water reservoirs. Microstructural observations showed that a dense three-dimensional network was retained under various salinities, which contributed to its structural stability and resistance to collapse. In physical simulation experiments, the initial water flooding flow rate was 420 mL/min at 5 MPa. After injecting HSPPG and reversing the water flooding direction, the flow rate remained below 330 mL/min while pressure increased from 1 MPa to 6 MPa, confirming excellent injectivity and plugging performance. HSPPG penetrated through high-permeability layers into the water coning zone, effectively blocking water channeling and suppressing bottom water encroachment, thereby enhancing oil displacement efficiency. This study provides a new material for profile control and water shutoff operations in high water-cut oil reservoirs driven by bottom water, and offers a novel technological perspective and research direction for managing water coning and improving oil recovery in such reservoirs.