Fracture Network Numerical Well Test Model Based on the Discrete-fracture Model

Abstract

Based on the characteristics of fractures in naturally fractured reservoir and the discrete-fracture model, a fracture network numerical well test model was developed, which incorporated the fractures explicitly in the spatial domain. In two-dimensional problems, fractures were represented as one-dimensional line element and matrix space was discretized into linear triangular elements. Bottom hole pressure response curves and pressure field were obtained by solving the model equations with finite-element method. Through analyses of the bottom hole pressure curves and the fluid flow in pressure field, seven flow stages can be recognized on the curves, i.e. wellbore storage, transition, fracture linear flow, fracture network flow, matrix to fractures flow, system radial flow and boundary-dominated flow. Effects of reservoirs parameters, such as fracture conductivity, matrix permeability, fracture density and permeability anisotropy were studied. The analysis results demonstrated that fracture conductivity played a leading role in the fluid flow. Matrix permeability influenced the beginning time of flow from matrix to fractures. Fractures density was another important parameter controlling the flow. The fracture linear flow was covered under large fracture density. The pressure propagation was slower in the direction of larger fracture density. The same situation happened in the permeability anisotropy cases.