A Multifunctional Sand-carrying and Oil-displacement Fracturing Fluid System Based on Physical Cross-linking

It is difficult to avoid the contradiction between the high sand-carrying capacity of fracturing fluids, the flowback and formation damage of gel breaking fluid during the shale oil extraction process. A new multifunctional sand-carrying and oil-displacement fracturing fluid system (PN-PPS), with high sand-carrying capacity, low damage and high oil displacement, it was developed by synergizing surfactant (PN) and polymers (PPS) and relying on the physical cross-linking to enhance the network structure. PN-PPS has excellent sand-carrying capacity and temperature and salt resistant performance by relying on the dense network structure. The sand-carrying time of ceramic in PN-PPS solution is as high as 510 min, profit from the network structure of the system strengthened by physical cross-linking. The gel breaking of PN-PPS quickly and thoroughly, the residue content of the gel breaking fluid is less than 34.5 mg/L and core damage is less than 18%. Further, PN-PPS shows excellent oil displacement performance, with oil washing efficiency higher than 99% at 90 ℃, and the oil imbibition recovery rate of 20.46%, compare with water displacement, the oil displacement rate of oil-displacing agent increased by 12.54%. Therefore, the application of PN-PPS can ensure efficient sand carrying fracturing and realize in-situ oil displacement without flowback, through combining the fracturing and oil repulsion processes. the application of PN-PPS provides an innovative solution for shale oil extraction, which is of great significance for the development of the integrated technology of fracturing and displacement.