The Accurate and Efficient Simulation of a Fractured Tight Gas Condensate Reservoir Using Embedded Discrete Fracture Model

Abstract

AbstractThe hydraulic fracture modeling is critical for the well dynamic performance and development optimization in the fractured condensate reservoir. The conventional approach based on LGR (Local Grid Refinement) is widely used but with low computational efficiency, and sometimes with artificial fracture orientation and geometry. In this study, a new workflow to model the hydraulic fractures using EDFM (Embedded Discrete Fracture Model) is developed to couple with the Nexus reservoir simulator for the first time. Borrowed from the dual continuum concept, the main idea of EDFM is the non-intrusive embedding of the fracture medium physical properties (such as transmissibility, pore volumes, etc.) into the pre-existing matrix cell blocks. Using the EDFM, tedious work such as model re-gridding and refinements can be avoided, and realistic fracture geometry and geological structures can be honored with only a fraction of the total computational cost.We validate the EDFM approach firstly with a simple mechanistic model and then a sector model with 18 hydraulic fractures in Cartesian grids. The results from the traditional LGR method are compared with those from EDFM to demonstrate its robustness. For the same fracture geometry and reservoir model configurations, the LGR-based and EDFM-based approach gives almost identical results for production simulations. We then applied this workflow to a more realistic sector model with 18 vertical wells in a tight gas condensate reservoir with corner points geometry. We demonstrated that the EDFM approach enables more realistic hydraulic fracture modeling, including the flexibility to incorporate geomechanics-consistent fracture orientation, gridding-independent fracture height, fracture half-length, and straight-forward modifications of fracture properties. Additionally, the speed of the EDFM is much superior to the LGR-based one. The speed-up factor reaches about 50 when appropriately decomposing the domain in this sector model, reducing the computational time from about 8 hours to about 9 minutes. This EDFM-Nexus workflow enables a much faster and more robust fracture modeling, model calibration, development optimization, and business decision-making in the tight gas condensate reservoirs.