Implementation of a Preprocessor for Embedded Discrete Fracture Modeling in an IMPEC Compositional Reservoir Simulator

Abstract

AbstractThe Embedded Discrete Fracture Model (EDFM) is a promising new method used to explicitly model high-level inhomogeneities such as conductive faults or fractures. The EDFM formulation can be used to model naturally fractured reservoirs (NFR) and unconventional reservoirs through also in a triple porosity model composed of hydraulic fractures, natural fractures, and matrix domains for simulation of unconventional reservoirs. Using non-neighboring connections, the EDFM approach was implemented in an IMPEC compositional reservoir simulator (UTCOMP). A preprocessing code was developed to convert the discrete natural/hydraulic fractures into a data set to be used by the simulator, which allows more realistic representation of fractured reservoirs. Compared to previous studies, the developed preprocessing code introduces additional features to better represent structural properties of matrix and fractures, such as implementation of Odas permeability tensor formulation for modeling permeability anisotropy, partial penetration of fractures into the grid, partial intersection of fractures, and calculation of equivalent properties using the definition of density of fractures for conventional dual porosity/dual permeability simulation. The preprocessing code is also capable of handling the data generated by commercial geological modeling softwares. Both the updated UTCOMP and preprocessing code were validated against in-house fully implicit simulator (GPAS) and fine-grid models using commercially available reservoir simulators. Simulation run time was improved by applying a porosity cut-off in the fracture cells, upon which constant fracture conductivity was assumed. Validation case studies include multi-fractured wells producing through depletion and a 2D quarter five-spot production scheme (water and miscible gas injection) in NFR. Moreover, the updated UTCOMP was further used for application case studies including 3D models and considering miscible gas injection for different, geological scenarios: horizontal, dipping, and anticline fractured reservoirs. Both continuous gas and water alternating gas (WAG) injection were evaluated. The validation studies show good agreement between EDFM and fine-grid models. Results show that the effect of fractures on hydrocarbon production depends on fracture network connectivity, which can be properly modeled using the preprocessing code integrates with a numerical simulator capable of handling non-neighboring connections.