Numerical model and investigation of simultaneous multiple-fracture propagation within a stage in horizontal well

Abstract

Multistage hydraulic fracturing in combination with horizontal drilling has been widely used in tight reservoirs. This technology can enlarge the drainage area of per well while reduce the operational costs. However, production data and fracturing field experiments both indicated that multiple fracture in horizontal well are nonuniform growth, and even some fractures are invalid. Therefore, we simultaneously consider the stress shadowing effect, flow resistance from wellbore friction, perforation friction and fracture friction to establish a simultaneous multiple-fracture propagation numerical model. In our model, the flow rate distributing into different fractures is determined based on Kirchhoff’s second law, and the multiple-fracture expansion velocity is calculated according to their energy release rate. Based on our numerical model, we investigate the influence factors of multiple-fracture even propagation within a stage. The single-fracture propagation results obtained from our numerical model and simplified semi-analytical solution have a good agreement, besides our four cluster fracturing numerical results are consistent with Wheaton et al. (Unconventional resources technology conference, Denver, Colorado, 2014) field experiment results; these two comparisons prove that our model is effective. Numerical results indicate that one or two clusters are more likely to achieve uniform expansion of multiple fractures than three or more clusters. In order to promote multiple-fracture uniform propagation, not only can we adjust the cluster number or cluster spacing, but also we can regulate the perforation friction.