Optimization of perforation parameters for horizontal wells in shale reservoir

Volume fracturing of horizontal wells is the key technology for efficient development of shale reservoirs, and perforation is the basic condition of hydraulic fracturing. In this paper, based on the basic equation of fluid-structure coupling and the cohesive fracture model, a three-dimensional numerical model of spiral perforation hydraulic fracture propagation in near well bore horizontal wells was established. The pipe flow elements were introduced to characterize the automatic distribution of fluid and the pressure drop caused by friction. The results show that the vertical perforation initiation pressure is lower than the horizontal perforation, the vertical perforation is easier to release energy after initiation, the fracturing fluid is easier to flow into the vertical perforation, and eventually form 1-2 major fractures. The common rule among different pore densities is that the fracture distribution at both ends of the cluster is more, and the fracture distribution in the middle is less, and the gap between the two increases with the increase of injection. When the hole density is higher than 8 P/m, the uneven development of fractures is significant. If the hole density is 4 P/m, the number of effective fractures around the wellbore decreases. Therefore, it is suggested that the optimal hole density is 8 P/m. With the increase of perforation depth, the effective area of liquid pressure on the hole wall increases, and the initiation pressure decreases. With the increase of the diameter of the hole, the initiation pressure is lower and the initiation and extension of the fracture are easier. Compared with pore diameter, the effect of pore depth on fracture propagation is greater than that of pore diameter. Under the calculation conditions, it is recommended that 8 P/m, hole depth is 0.8 m, and aperture is 20 mm. (C) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

Horizontal well volume fracturing is crucial for efficient shale reservoir development, with perforation being a basic requirement. A numerical model was established for spiral perforation hydraulic fracture propagation in near well bore horizontal wells, revealing lower initiation pressure for vertical perforation and easier energy release, leading to the formation of 1-2 major fractures. The optimal hole density is suggested to be 8 P/m, with significant uneven fracture development observed at densities higher than 8 P/m.