3D numerical modeling of fracture initiation from branch wellbore

Abstract

ABSTRACT Branch wellbore fracturing in branch wellbore is a new technology for developing unconventional oil and gas reservoirs. In this study, we developed a 3D numerical model based on finite element method to analyze fracture initiation characteristics from branch wellbore. Two typical cases were analyzed: a branch wellbore drilled from vertical main wellbore and a branch wellbore drilled from horizontal main wellbore. Then, the effects of different factors on fracture initiation were analyzed, which includes branch wellbore orientation (intersection angle between branch wellbore axis and maximum horizontal stress/vertical stress), difference between vertical and maximum horizontal stress, branch wellbore length and branch wellbore diameter. Results show that fracture initiation from the branch wellbore is mainly controlled by the branch wellbore orientation and difference between vertical and maximum horizontal stress. Besides, for the branch wellbore drilled from vertical main wellbore, fracture always initiates from two symmetric areas at the base of branch wellbore with any branch wellbore orientation and difference between vertical and maximum horizontal stress. However, for the branch wellbore drilled from horizontal main wellbore, fracture initiates from two symmetric zones at the base of branch wellbore when branch wellbore orientation is less than 40° and difference between vertical and maximum horizontal stress is larger than 0.1, while fracture initiates from two symmetric zones on the whole branch wellbore when branch wellbore orientation is larger than 40° or difference between vertical and maximum horizontal stress is less than 0.1. Furthermore, the increase of branch wellbore diameter leads to increase of FIP by 1–4 MPa. The key findings of this work provides basis for the field application of this technology.