The Characteristics of Meso-Scale Natural Fractures in Deep Shale Reservoirs and their Geo-Engineering Significance

Abstract Having in-depth understanding of meso-scale natural fractures in deep shale reservoirs of southern Sichuan Basin is of great importance for the effective shale gas development since natural fractures may cause real time casing deformation and decide optimal fracturing design. Existing studies mostly emphasize macro-scale natural fracture prediction using seismic data, but this is not enough anymore for current extensive development stage which demands more detailed analysis of meso-scale natural fractures. Based on multi-resolution data, i.e. cores, image logs, seismic structures and fracture-related attributes, the characteristics of meso-scale natural fractures are analyzed detailedly, including fracture distribution by zones, fracture type and dip angle, fracture intensity distribution and fillings, and fracture strike. Then the genesis of natural fractures and seismic predictability are inferred based on their characteristics and strike comparison with the trending of nearby seismic structures and seismic fracture prediction attributes. At last, the slip tolerance of all natural fractures with all attitudes from image logs is figured out based on 3D mechanical earth model (MEM) and Moor-Coulomb criterion. The conclusions in this paper provide solid geological foundation for more accurate seismic fracture prediction, 3D discrete fracture modeling, geological stability analysis and numerical simulation, which will improve the effective development of deep shale reservoirs.