The hydraulic fracturing with multiple influencing factors in carbonate fracture-cavity reservoirs

In carbonate fracture-cavity reservoirs, such as the Tahe oilfield in China, natural cavities are the main storage space of oil. It is critical to control the propagation of hydraulic fractures in order to enhance the connectivity between wellbores and oil-filled cavities. In this work, the influencing factors, including natural fracture strike angle, confining stress, the internal fluid pressure of natural cavities and fluid injection pressure are investigated numerically using the TOUGH-AiFrac simulator. Our results show that when multiple influencing factors are taken into account, natural fractures have dominant impacts on hydraulic fractures propagation, followed by the impacts of confining stress. These two influencing factors are critical to the hydraulic fracturing design in carbonate fracture-cavity reservoirs. Fluid injection pressure control can be limited by the capacity of the field equipment and the influence of cavity internal fluid pressure that tends to attract propagating fractures depending on the site-specific reservoir conditions. The present work provides guidance on how to optimize the design of hydraulic fracturing in carbonate fracture-cavity reservoirs.