Improved Model for Predicting Multiple Hydraulic Fracture Propagation from a Horizontal Well

Abstract

ABSTRACT The goal of this research effort was to develop and evaluate the applicability of a simplified multicrack, hydraulic fracture model for predicting multiple fracture propagation during stimulation of a horizontal wellbore in a naturally fracture formation. This model is based on the assumption that individual fracture propagation is governed by the theory presented by Geerstma and DeKlerk2 for single vertical fractures of a constant height. In this model, the fluid flow in the wellbore is coupled with the flow in, and propagation of, multiple fractures. The fluid volumetric flow rates and pressure compatibility is maintained between the wellbore and the fracture network with a systematic iterative, numerical scheme. Prior to analysis of available field data, the model was evaluated by predicting how variations of hydraulic fracture treatment parameters Influence the propagation of a multiple fracture system. Based on these evaluations, it was concluded that both turbulent and laminar conditions of flow exist in different segments of the wellbore. It was also concluded that fracture inclination to the well-bore and entry losses into the natural fractures from the wellbore have a significant influence on the propagation of a multiple fracture system. Following this initial evaluation, data gathered from a recently completed horizontal wellbore field test were then used to evaluate the predictive capability of the multicrack hydraulic fracture model. In this field test, radioactive-tracer with spectral gamma ray logging was used to determine the locations of fractures accepting fluids and the volumes of fluids entering natural fractures. The predicted and log-derived fluid flow rates into each natural fracture were in good agreement. To date, the model has been modified to predict hydraulic fracture propagation with proppant laden fluids. Predictions from this enhanced model are being compared against available field data to evaluate the modified multicrack model. As more field data are gathered, and the multiple fracture model is modified and improved, additional comparisons can be made. The multicrack model provides further insight into the factors that govern multiple fracture propagation in horizontal wells.