Geomechanics modeling of ultra-deep fault-controlled carbonate reservoirs and its application in development

Abstract

To enhance the development efficiency of ultra-deep fault-controlled carbonate reservoirs, large-scale rock mechanical experiments were conducted to reveal the deformation and connectivity mechanisms of high-angle to near-vertical fault surfaces. Based on the mechanical and flow coupling principles of high-pressure water injection production, geomechanical modeling was employed to clarify the current in-situ stress field and fault activity distribution patterns in fault-controlled carbonate reservoirs. Significant differences were found in fault activities in different directions and in the connectivity of fracture and cavity bodies in different parts. The development effects of different wellbore trajectories were then analyzed, and an integrated geological and engineering working method was proposed to scientifically guide the design of wellbore trajectories and the optimization of water injection schemes. The results show: ① Large-scale fractured bodies and high-angle fracture systems in strike-slip fault deformation are key factors affecting reservoir quality. High-pressure water injection can activate existing fractures on one hand, and on the other hand, it can extend and expand based on existing fractures, even generating new fractures, promoting the interconnection of fault-controlled fracture and cavity bodies in both vertical and horizontal directions; ② During the high-pressure water injection process, coupling changes between mechanics and flow occur inside the fault body, improving the seepage environment, and increasing oil and gas recovery rate through cyclic lifting; ③ According to the shape and the occurrence of the fault body, and the dynamic shear deformation connectivity of the fault surface, the best well point and well trajectory for directional wells can be selected, and the water injection scheme can be optimized; ④ In the fault-controlled oil reservoir test area of Tarim Basin, the recovery rate was increased by 5% through high-pressure water injection. This method provides a good theoretical basis and technical support for the efficient development of ultra-deep fault-controlled reservoirs.

Keywords

• ultra-deep layer
• fault-controlled carbonate reservoir
• fracture-cavity body
• geomechanics
• fault activity
• wellbore trajectory
• water injection development
• geology-engineering integration