Extended Abstract: Advanced Multiple Porosity Model for Fractured Reservoirs

Abstract

Abstract Much of the hydrocarbon reserves are stored in fractured reservoirs with high heterogeneity worldwide. In such reservoirs there likely exists more than two porosity types, and transient flow likely occurs in the matrix. Dual porosity models can characterize only two porosity types and are difficult to accurately capture the transient flow. This paper discusses an advanced model that allows simulating an arbitrary number of porosity types which accurately captures the transient flow in the matrix. The proposed multiple porosity model honors any number of porosity types with different properties, such as permeability, porosity and wettability. Arbitrary connection for intra-porosity and inter-porosity flow are designed in an unstructured scheme, and convenient transformation between multiple porosity and multiple permeability formulations is allowed. A flexible porosity subdivision works in a fashion of hierarchical refinement and allows us to characterize the transient flow in the matrix and multilevel fracture sets with different geometry as well. The formulation is designed to allow the proposed scheme to be generalized. To quantify the improvement available with the new formulation, multiple porosity models are compared with single porosity models and analysis of different shape factors are also conducted. Our results show that they can be made to be equivalent under single phase conditions. Moreover, the application of the new model in shale reservoirs is discussed in two phase flow cases considering mixed wettability in shale matrix, and the results show that through a complete inter-porosity connection mode, the flow pathway of gas and water in shale is effectively identified.