The origin and distribution prediction of fractures in tight sandstone of Z gas field in Xihu Sag

The development scale of natural fractures exerts a certain degree of control over the stimulation of deep tight gas reservoirs. Currently, the fracture development pattern in the Z gas field remains unclear, which restricts the fracturing development of ultra-low permeability gas reservoirs. Fractures were systematically identified and accurately predicted through data including core and thin section observations, inclusion analysis of fracture fillings, drilling fluid losses, and imaging logging, combined with post-stack seismic attributes and paleotectonic stress field simulation, so as to clarify the types and genesis of fractures and establish a geological model for fracture development. The research results indicate that structural fractures are predominantly developed in the study area, primarily consisting of shear fractures located on the structural limbs near faults, while tensile fractures are relatively less developed in the structural highs. A fault-dominated fracture development model, mainly characterized by shear fractures, has been established. Most fractures are filled, and the development degree of effective fractures is relatively low. Therefore, wells can be placed near fault zones and pilot development can be conducted. The research findings on fractures hold guiding significance for the formulation of fracturing plans in the target formation of the research area.