A quantitative fracability evaluation method and its application to deep shale gas development in Sichuan Basin, China

• A novel fracability evaluation model integrating improved brittleness index, rock strength, geostresses, and natural weakness characteristics was developed using a combined weighting method. • Rock brittleness and fracability are not equivalent for deep reservoirs; the proposed fracability index provides a more comprehensive assessment. • The fracability index shows a high correlation (84%) with pay zones and actual gas production, validating its practical significance. • The method offers theoretical guidance for selecting fracturing candidates and optimizing fracturing design in deep shale gas development.