Water Management and Oil Recovery Improvement Performance of High-Strength Preformed Particle Gels in Fractured Conglomerate Reservoirs

Lithologic reservoirs, such as conglomerate reservoirs, exhibit stronger heterogeneity compared with conventional sandstone reservoirs. Their early stage development usually requires hydraulic fracturing to increase the stimulated reservoir volume (SRV). As a result, high-conductivity channels are generated during waterflooding, which further limit the sweep volume and oil recovery. Traditional particle gels and in situ cross-linked polymer gels exhibit limited field application due to their low plugging strength. In this paper, a high-strength preformed particle–gel (HSPPG) with sticking-together capability was studied through evaluating different factors such as particle size, swelling ratio, injection volume, and their effects on the swelling performance, gel strength, and plugging performance in fractures. The results show that the swollen HSPPGs had strong water swelling and sticking-together ability, exhibited good viscoelasticity, and formed high-strength adhesive bonds on rock surfaces. In addition, as the particle size decreased, the gel’s maximum swelling ratio increased. However, as the swelling ratio of HSPPG increased, the storage modulus G′ and the loss modulus G″ both decreased, but they still displayed excellent elasticity and viscosity. The greater the filling volume of HSPPG in fractured conglomerate rock cores, the stronger the overall plugging efficiency. Oil displacement experiments showed that the oil recovery of fractured conglomerate rock cores treated with HSPPG increased by 22.12 percentage points on the basis of primary waterflooding. Therefore, HSPPG has a promising application prospect in the conformance improvement of strong heterogeneity conglomerate reservoirs.