Coreflooding Evaluation of Fiber-Assisted Recrosslinkable Preformed Particle Gel Using an Open Fracture Model

Recrosslinkable preformed particle gels (RPPGs) have been used to treat the problem of void space conduits (VSC) and repair the "short-circuited" waterflood in Alaska's West Sak field. Field results showed a 23% increase in success rates over typical preformed particle gel (PPG) treatments. In this paper, we evaluated whether adding fiber into RPPGs can increase the RPPG plugging efficiency and thus further improve the success rate. We designed open fracture models to represent VSC and investigated the effect of swelling ratio (SR), fracture size, and fiber concentration on gel injection pressure, water breakthrough pressure, and permeability reduction. Results show that fiber can increase RPPG strength and delay its initial swelling rate, but an optimized fiber concentration exists. Beyond that, the fiber entangling problem can result in the recrosslinked bulk gel inhomogeneously and impact gel quality. The injection pressure of fiber-assisted RPPGs increased with the SR and fracture width. During post-injection water process, the breakthrough pressure and residual resistance factor increased when the RPPG SR and fracture width decreased. Fiber-assisted RPPGs can dramatically reduce the permeability of the fractured core up to 1.8x10(6) times. It is observed that the fiber-assisted RPPGs used in the experiment remain in a bulk form in the fracture when we open the fracture after water injection. Not only does the addition of fiber improve the plugging efficiency, but it also prevents particle precipitation along vertical fractures or conduits.