Experimental Study of Proppant Conductivity in Low Permeability Reservoirs in the South China Sea

The degree of reserve recovery in low permeability reservoirs in the South China Sea is low, and high-conductivity fractures are difficult to create from hydraulic fracturing. Laboratory studies were conducted to analyze the impact of clay mineral content, combination mode of proppants with different grain sizes, and gel-breaking liquid viscosity on fracture conductivity. Studies showed that the conductivity reduction rate of the 20/40 mesh proppant went up from 13.84% to 31.34% when clay mineral content increased from 15% to 50% under testing conditions.The optimal ratio for ceramsites sized in 20/40 mesh, 30/50 mesh and 40/70 mesh was 3∶1∶1, with a final conductivity of 116.7 D·cm. The maximum proppant conductivity achieved at a gel-breaking liquid viscosity of 1 mPa·s. According to the experimental results, with the increase in clay mineral content, proppant conductivity would decrease. Proppant crushing is mainly caused by compression among proppant particles rather than the interaction of the proppant with the reservoir. A larger proportion of proppant with a larger grain size results in higher conductivity when the proppant is combined with different grain sizes. Permeability decreases from proppant crushing with a small grain size is the main reason for conductivity loss as closure pressure increase. A lower gel-breaking liquid viscosity indicates a higher proppant conductivity. The research outcomes can provide a reference for stimulation candidates selection and fracturing scheme optimization of low permeability reservoirs in the South China Sea.