Influence of Surface Wettability of Nonhomogeneous Proppant on Hydraulic Fracture Inflow Performance

Quartz sand proppant is widely used in hydraulic fracturing and the extraction of low-permeability reservoirs to prevent fracture closure and enhance reservoir recovery effectively. The influence of proppant size and type on well productivity has been widely studied, but the mechanism of proppant surface wettability on the hydraulic fracture inflow performance has not been thoroughly investigated. To further understand the influence of proppant wettability on fracture inflow performance, in this work, a hydrophobic quartz sand proppant was prepared by a simple dip-coating method using silane solution with a static water contact angle of 136.8° in air, and three types of filtration layer models were prepared according to the mass ratio of hydrophilic/hydrophobic particles, hydrophilic (4:0), hybrid (2:2), and hydrophobic (0:4), to analyze the effects of quartz sand proppant wettability on the oil/water distribution and conductivity performance in the three filter layers. The preliminary results show that (1) under different mesh sizes of quartz sand, different emulsion concentrations, and high-viscosity oil samples, the hydraulic performance of the hydrophobic quartz sand filter layer is generally better than that of the hydrophilic quartz sand filter layer; and (2) the hydraulic performance of the hydrophobic quartz sand filter layer decreases as the concentration of the emulsion increases, the hybrid quartz sand filter layer is basically unaffected and its hydraulic performance is relatively stable, and the hydraulic performance of the hydrophilic quartz sand filter layer is more fluctuating. The flow conductivity of the hydrophilic quartz sand filter layer fluctuates greatly. In addition, the mechanism of the influence of proppant wettability on the flow-conducting performance is proposed through the microscopic percolation experiment of an oil-water emulsion. This study is of some guiding significance for engineers to better design the surface wettability of proppant and the selection and matching of proppant in hydraulic fracturing construction design to improve the recovery rate of low-permeability reservoirs.