Abstract: The X-6 Formation is located at a depth of 500-700 m in the QA Oilfield and has low porosity and low permeability. Natural high-angle fractures exist in the formation. These conditions partially satisfy the requirements for a fracture network after hydraulic fracturing but may result in relatively complex fracture patterns and introduce difficulties to the fracturing design and treatment. Firstly, triaxial tests were carried out in this work to study rock mechanical properties. A two-dimensional seepage-stress-damage-coupled finite element model of the sand- and mudstone-interlayered formation was then established. Lastly, the propagation of multiple hydraulic fractures and the stress interference mechanism of the X-6 reservoir were simulated and the influences of the pumping rate, in situ stress, and fracturing fluid viscosity on the stress interference were studied. The interference mechanism of the interaction of the hydraulic and natural fracture was revealed. We found that the reservoir has complex fracture mechanical and engineering geological conditions for complex fracture generation, providing theoretical guidance for the hydraulic fracturing of the region.

Key words: fracture morphology, horizontal fracture, stress interference, fracture intersection, pore pressure element