Laplace Domain Coupled Dual Continuum and Embedded Discrete Fracture Model for Rate Transient Analysis in Low Permeability Reservoirs

Abstract

Abstract Modeling transient flow of horizontal wells with complex fracture networks is attractive and challenging topic for economically exploitation of low permeability reservoirs. Previous works have been done by employing analytical, semi-analytical and numerical models to solve this problem. The analytical trilinear-flow is not capable to capture the shapes and distributions of stimulated reservoir volume (SRV), while semi-analytical source function method doesn't consider natural fractures. In the paper, we developed a hybrid coupled approach to combine the embedded-discrete-fracture model (EDFM) and dual continuum representation in Laplace domain. The transient dual porosity with various matrix-block size is implemented to incorporate the fracture spacing and the petro-physical characteristics of flow from tight matrix to natural fractures. Large scale hydraulic fractures are explicitly modeled using embedded-discrete-fracture model (EDFM) as the source terms in the systems. Other than the equivalent distance and finite difference method used in EDFM, a novel element-based numerical method called mixed boundary element method is developed to rigorously capture the transient flow behavior of hydraulic fractured systems and couple the above models in triangle grids. Several examples in this work are presented to show the robustness, applicability and computational convenience of the hybrid approach for the rate transient and pressure transient analysis of low permeability oil and gas reservoirs. The proposed model is validated by comparing the results against both analytical trilinear solutions and other numerical solutions. In addition, the method provides maximum flexibility of representation for complex fracture systems both in pressure transient analysis and production forecast.