Numerical Investigation of Hydraulic Fracture Extension Based on the Meshless Method

Abstract

The fracture propagation in hydraulic fracturing is described as a nonlinear problem dynamic boundary. Due to the limitation of mesh refinement, it is difficult to obtain the real crack propagation path using conventional numerical methods. Meshless methods (MMs) are an effective method to eliminate the dependence on the computational grid in the simulation of fracture propagation. In this paper, a hydraulic fracture propagation model is established based on the element-free Galerkin (EFG) method by introducing jump and branch enrichment functions. Based on the proposed method, three types of fracturing technology are investigated. The results reveal that the stress interference between fractures has an important impact on the propagation path. For the codirectional fracturing simultaneously, fractures propagate in a repel direction. However, the new fracture is attracted and eventually trapped by the adjacent fracture in the sequential fracturing case. For the opposite simultaneous fracturing in multiwells, two fractures with a certain lateral spacing will deflect toward each other. The effect of stress shadow should be used rationally in the optimization of construction parameters; for the single well multistage fracturing, the stage spacing should be out of stress inversion area, while for the simultaneous fracturing of multiple wells, stress inversion zones should be used to maximize communication between natural fractures. Overall, this study establishes a novel and effective approach of using MM to simulate the propagation of hydraulic fractures, which can serve as a useful reference for understanding the mechanism of hydraulic fracture propagation under various conditions.

A Random‐XFEM technique modeling of hydraulic fracture interaction with natural void

“…Owing to the requirements of oil and gas reservoirs and field technology, simulations of hydraulic fracturing have been rapidly developed, with great advances both in theory and laboratory experiments. In virtue of developments in computer technology and numerical calculation method, models for hydraulic fracture propagation have evolved from analytical models (KGD model, 1,2 PKN model, 3 pseudo‐3D model 4 ), semi‐analytical models (liner network model, 5,6 UFM model 7,8 ) to numerical models (classical finite element method, 9–11 displacement discontinuous method, 12–14 discrete element methods, 15,16 extended finite element method 17–20 ), and the theory has evolved from double‐wing seam theory to multi‐factor theory, which considers the effects of natural fracture, 21–24 stress shadow, 25,26 hydro‐mechanical coupling, 27–29 thermal strain 30,31 . Despite great achievements in numerical simulations of hydraulic fracture propagation, most studies of hydraulic fracture propagation models are based on homogeneous media., It was found that the propagation direction of dry crack may deviate from the direction of maximum horizontal principal stress as a result of the anisotropy of rocks 32–36 .…”