关键词: 定面射孔, 流固耦合, 起裂压力, 裂缝形态, 数值分析

Abstract: The set surface perforation is the latest perforating technology which is proposed to improve fracture volume effect. Based on the theory of fluid-solid coupling and rock mechanics, a three-dimensional elastic-plastic fluid-solid coupling stress model for set surface perforation in stratums is developed. Based on the maximum tensile stress criterion, the crack rule of hydraulic fracture is obtained by numerical simulation. It can be seen from abundant calculations that under the condition of set surface perforation, crack first initiates in the perforation of the perforating plane, and then extends in the perforating surface to form a fan-shaped fracture surface, which increase the swept volume of hydraulic fracture and the wellbore connectivity. Both sides of the perforation produce additional stress in the middle perforation to reduce the principal stress of Y direction within the same plane and increase the principal stresses of the X and Z directions. Thus it is the reason that when set surface perforation is adopted for the normal fault, under a larger crack stress, the greater the perforation azimuth angle, the lower the crack pressure. Only when the perforating azimuth angle is greater than 60°, the set surface perforation crack pressure is lower than that of spiral perforation. For reverse fault, the smaller the perforation azimuth angle, the lower the crack pressure, and the crack pressure is lower than that of spiral perforation at any time. Reducing the angle between perforation and perforation, increasing the perforation diameter and depth can reduce the crack pressure effectively.

Key words: set surface perforation, fluid-solid coupling, crack pressure, cracks form, numerical analysis