Hydraulic fracture initiation and propagation: roles of wellbore trajectory, perforation and stress regimes

This paper develops a generic model for predicting hydraulic fracture initi ation from arbitrarily oriented wellbores. For a given in-situ stress condi tion and wellbore orientation parameters, the model predicts the fracture i nitiation pressure and the orientation and location of fractures on the wel lbore wall. The model has been applied in a series of in-situ stress condit ions to study the effect of wellbore orientation on fracture initiation usi ng non-dimensional parameters, which have enhanced the applicability of pre sented results for any stress condition. Closed-form analytical solutions a re also obtained for initiation of longitudinal, transverse and complex mul tiple fractures from vertical and horizontal wellbores with and without per foration. A numerical model is then incorporated in the study to analyze th e propagation behavior of initiated fractures. Causes of Fracture initiatio n at non-preferred locations and its effects on fracture propagation pressu re and fracture volume due to twist of these initiated fractures during pro pagation are studied and discussed. Results from the analytical and numeric al models used in this study are interpreted with a particular effort to en lighten the causes of abnormally high treating pressures during hydraulic f racture treatments. (C) 2000 Elsevier Science B.V. All rights reserved.