Effect of multiple factors on preformed particle gel placement, dehydration, and plugging performance in partially open fractures

摘要

Preformed particle gels (PPGs) have been successfully applied for solving conformance problems caused by fractures. In real reservoirs, a considerable portion of fractures have relatively short length and closed ends. However, PPG treatment in this typical kind of fractures, termed partially open fractures (POFs), was barely investigated in existing studies. Cylindrical sandstone cores were used to construct partially open fracture models. PPG placement and water floodings were conducted in the POF models to explore the effect of fracture length, fracture height, matrix permeability, and residual oil on the PPG placement, dehydration, and water-plugging performance. Up to 18 fracture volume (FV) of PPG could be placed under a 1000 psi placing pressure. With the same placing pressure, less FV of PPG was placed with the increase of fracture height, decrease of matrix permeability, or presence of residual oil, respectively. However, placement FV didn't show an apparent change with the fracture length modification. The re-swelling experiments showed that PPG samples dehydrated when exposed to a high pressure difference between fracture and porous rock. The dehydration level of placed PPG yielded a positive correlation with the placement FV in all conducted experiments. The placed PPG blocked the water flow until a breakthrough pressure was reached. It performed a resistance to the water flow after breakthrough. The residual resistance factor increased when the fracture had a greater length, the matrix had a higher permeability, or residual oil absented in the core. The residual resistance factor was relatively independent of the partially open fracture height.