Experimental Evaluation on the Fracability of Tight Sandstones in the Shaximiao Formation in Central Sichuan Basin

Tight sandstone reservoirs in the Shaximiao Formation of the central Sichuan Basin are primarily developed in the first member of the Shaximiao Formation and exhibit promising exploration and development potential. However, systematic evaluation of engineering sweet spots and fracturing effectiveness has not yet been conducted, resulting in insufficient guidance for fracturing engineering design. Therefore, it is necessary to investigate the engineering geological characteristics of tight sandstone reservoirs in the study area. Experimental results indicate that the reservoirs have an average porosity of 4.16% and an average permeability of 0.46 mD. Pores are predominantly concentrated in the range of 1–5 μm, with the presence of some microfractures. The mineral composition is dominated by quartz, potassium feldspar, and plagioclase, with an average clay mineral content of 6.44%. The average brittleness index of the reservoirs is 45.74%, the in-situ stress difference coefficient ranges from 0.17 to 0.30, the average fracture pressure is 45.14 MPa, the average fracture toughness is 0.48 MPa•√m, and the average fracture development index is 0.91. This study establishes a fracability evaluation model applicable to tight sandstone reservoirs in the Shaximiao Formation of the central Sichuan Basin. By integrating field operations, it analyzes and summarizes the characteristics of high-productivity wells achieved through fracturing stimulation and proposes strategies for reservoir stimulation in wells with suboptimal fracturing outcomes.