The Simulation Method Research of Hydraulic Fracture Initiation with Perforations

Abstract

Perforation is an important factor affecting on hydraulic fracture initiation and propagation. It is still difficult to observe fractures’ geometry and calculate initiation pressure due to the lack of research method and complexity of perforations. This paper introduces a new experimental technology and numerical simulation method based on discrete grid. They can be used to simulate fracture initiation with the spiral perforation configuration near the wellbore and compare the difference of fracture initiation pressure and fracture morphology under different perforation strategy. The results show that: (a) the new perforation technology with unified plane can reduce fracture initiation pressure more significantly instead of increasing traditional spiral perforation length. The initiation pressure which is lowered nearly to the minimum horizontal principal stress indicates that the changing of perforation shape from spiral to unified plane can reduce stress concentration effect near the wellbore. (b) The unified plane technology can improve perforation efficiency more significantly compared with traditional spiral perforation which means fracture initiates from all perforation holes and makes the fracture initiation geometry more simple to decrease fracture distortion friction. So the new completion pattern not only helps fracture initiation but also decreases fracture propagation pressure. This new simulation method helps to guide well completion optimization in Chang 6 and 7 tight oil formation, Ordos Basin, P.R. China. Total more than 50 trial horizontal wells with unified plane perforation were conducted. The fracture initiation pressure was dropped obviously.