Research and Application of Fracability Evaluation Method for Tight Sandstone Reservoirs Based on Logging and Experimental Data

In recent years, oil and gas exploration, both onshore and offshore, has gradually moved towards the field of low porosity and low permeability. The development of such reservoirs requires hydraulic fracturing, making the evaluation of reservoir fracability increasingly important for major oil and gas fields. This study focuses on the tight sandstone gas reservoir in the northeast edge of the Ordos Basin. Based on well-logging data, as well as rock mechanical and physical experiments, a comprehensive brittleness evaluation method—accounting for the influence of minerals and microcracks—is proposed for the study area. Then, the fracability of reservoirs is evaluated considering four aspects: the difficulty of generating hydraulic fractures, the vertical expansion ability of hydraulic fractures, the azimuth of hydraulic fractures, and the complexity of the hydraulic fractures network. Specifically, taking into account the strength and brittleness of rocks, the difficulty of generating hydraulic fractures was analyzed. The vertical expansion ability of hydraulic fractures was discussed through the thickness of the barrier formation and the differences in properties between the reservoir and the barrier formation. The azimuth of hydraulic fractures was determined through fast shear wave azimuth obtained from acoustic anisotropy inversion or induced fractures and wellbore collapse observed in electrical imaging data. The complexity of the hydraulic fractures network was assessed based on parameters such as rock brittleness, microcracks, bedding, natural fractures, and horizontal stress difference coefficient. The application example indicates that reservoirs with good fracability have a significant increase in post-fracturing production, and it also shows good consistency with the analysis of the hydraulic fracturing effect and post-fracturing fracture network morphology. The application example confirms the reliability and accuracy of the prefracturing fracability analysis.