Fracability Evaluation Method of a Fractured-Vuggy Carbonate Reservoir in the Shunbei Block

Abstract

The fracability of carbonate reservoirs is a key indicator for evaluating whether reservoirs can be effectively fractured. Taking the fractured-vuggy carbonate reservoir in the Shunbei block as an example, the microscopic characteristics and mechanical properties of this reservoir were analyzed. The test results showed that the core microstructure is relatively dense, the micropores and microfractures are developed, and the mineral composition is characterized by "high carbonate and few impurities". The compressive strength, Young's modulus, and Poisson's ratio of the rock increased with the increase in the confining pressure. Poisson's ratio is more sensitive to confining pressure than Young's modulus and shows the ductile transformation tendency from a low confining pressure to a high confining pressure. Considering the difficulty of forming a complex fracture network, we put forward a "fracture propagation factor" equation constructed with five main factors, including brittleness, fracture toughness, natural fracture, hole size, and horizontal stress difference, and then the fracture propagation factor of Yijianfang formation is calculated to be greater than 0.5. It is known that the Yijianfang formation has higher fracability. On this basis, combined with the construction parameters, a model for evaluating the fracability of a fractured-vuggy carbonate reservoir was established. The comprehensive fracability of four wells in the Shunbei block was calculated by the model. From the calculation results, the comprehensive fracability index of SHB43X was 0.5406 and greater than that of the other three wells, which has a high correlation with the production after fracturing.

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