Hydraulic fracture initiation mechanism in the definite plane perforating technology of horizontal well

Abstract

The local stress calculation model of the definite plane perforation for the horizontal wells was built, and the mechanism of fracture initiation and the influence rules of the wellbore location and perforating parameters on the fracture initiation pressure were analyzed. The in-situ stress model of three-dimensional fluid-solid coupling was established according to the theory of percolation mechanics, and the method for determining the initiation pressure of the definite plane perforation was presented according to the maximum tensile stress theory and was verified by application example. The calculation and analysis reveal: for the in-situ stress fields of normal faults and reverse faults, the initiation of hydraulic fractures happens on the perforated plane during the definite plane perforation, a wide, short, vertical fracture forms in the in-situ stress field of a normal fault, and a narrow, long, diverted fracture forms in the in-situ stress field of a reverse fault; for the in-situ stress field of a normal fault, the greater the wellbore azimuth and inclination angle are, the lower the initiation pressure is; for the in-situ stress field of a reverse fault, the larger the wellbore azimuth angle or the smaller the wellbore inclination angle is, the lower the initiation pressure is; the smaller the perforation angle, the greater the perforating depth, or the larger the perforation diameter is, the lower the initiation pressure of definite plane perforation is. Key words: definite plane perforation, hydraulic fracturing, volume fracturing, fracture initiation mechanism, fracture initiation pressure