FRACABILITY ANALYSIS AND ENGINEERING SWEET SPOT EVALUATION OF THE WUFENG-LONGMAXI SHALE: A CASE STUDY FROM A WELL IN THE SOUTHWEST CHINA

The identification of engineering sweet spots is crucial for the efficient development of shale oil and gas, as it enables optimized fracturing design and supports cost-effective production. This process typically relies on an assessment of reservoir fracability. Using a shale gas well in southwestern China as a case study, this research applied the Analytic Hierarchy Process (AHP) to evaluate the fracability of the Wufeng-Longmaxi Formation shale and identify engineering sweet spots. Rock mechanical parameters—including tensile strength, Young's modulus, and Poisson's ratio—were measured directly at the drilling site using a truck-mounted rock mechanics testing system, minimizing sample disturbance caused by storage and transport. The brittleness index was characterized using both brittle mineral content and inherent brittleness indicators, while the horizontal stress difference was calculated based on the Huang Rongzun model. The results show that the fracability index generally increases with depth. In particular, the Long-₁² and Long-₁¹ sub-layers exhibit high fracability indices, marking them as engineering sweet spots, which correspond well with geological sweet spot intervals. The fracability index derived from this method can be cross-verified with well logging data, enabling more accurate delineation of engineering sweet spots and providing valuable guidance for the design of field fracturing operations.