Nanoparticle-Enhanced Water-Based-Emulsion Fracturing Fluid for Improved Imbibition Recovery in Unconventional Reservoirs: Performance and Mechanism

Abstract

The conventional friction reducer, typically a water-in-oil (W/O) emulsion, used in slickwater, encounters challenges related to poor environmental friendliness, limited stability, and low activity, hindering its widespread applicability. In this study, we synthesized a water-based emulsion through water dispersion polymerization, incorporating nanoparticles (NPs) into the process to enhance the stability and activity of the polymer emulsion. The result is an environmentally friendly, oil-phase-free, instantly dissolution, and highly efficient friction reducer, intended to optimize the utilization efficiency of slickwater. The NP-enhanced water-based emulsion demonstrated a consistent and spherical dispersion, featuring an average particle size of ~10 μm, maintaining stability for more than 6 months. With rapid dissolution in water, achieved within a mere 38 seconds, it facilitated continuous on-the-fly mixing. Slickwater composed of this emulsion exhibited outstanding application performance, yielding a remarkable 76% reduction in pipeline friction. The presence of NPs and specific monomers facilitated the formation of a spatial network structure that maintains high temperature/shear resistance even after prolonged shear. Moreover, the system exhibited an exceptional capacity for imbibition oil production. Indoor spontaneous imbibition experiments showed a final recovery rate of 32.41% in tight oil cores (~10% higher than conventional systems), and imbibition depth reached 40.2 mm (1.2-fold increase compared with traditional systems). Field experiments were conducted in a tight oil reservoir to validate practical applications; the results further validated the effectiveness of the novel system. The treated wells showcased rapid oil production, reaching an average daily production rate of 55.8 t/d and water content as low as ~31%, satisfying the predicted production target.