ABSTRACT:

The fracture characterization is an integral part of the numerical reservoir simulation, and the application of the EDFM (Embedded Discrete Fracture Model) has been implemented to describe fracture networks with high complexity in shale reservoirs. To understand in which conditions EDFM could work well for characterizing fractures in shale reservoirs, we developed a new workflow to compare the simulation results of the EDFM method with LGR (Local Grid Refinement) technique. In this study, we considered pressure-dependent permeability in both shale gas and shale oil scenarios. Combining the EDFM method with reservoir simulators, we performed a series of sensitivity analysis on grid size resolution to evaluate its impact on EDFM performance. Then, since it would be necessary to construct models that had more complicated conditions, we conducted further study on multiple phases flow and made comparisons of simulation results for EDFM and LGR methods. Through the comparison of simulation results, the results of EDFM were validated. Furthermore, we included natural fractures into the model to investigate their influence on well production of single well and multiple wells. Finally, we provided the summarizations of the situations in which the EDFM could be applied in modeling the fracture networks for shale reservoirs according to the comparisons of results. By following the workflow that we introduced, we can obtain the production simulation results from shale reservoirs under various conditions. This workflow proved that this powerful EDFM method has the strong ability to model shale reservoirs in a more efficient and accurate way.

1. Introduction

With the unconventional reservoirs development draw great attention to the oil and gas industry, the application of hydraulic fracturing technique combined with horizontal wells are commonly used to significantly improve the productivity. In this process, characterizing the complex fracture networks due to this stimulation has become an essential part in reservoir simulations. For the reservoir simulation in unconventional reservoirs, the fracture networks simulation techniques include local grid refinement (LGR), discrete fracture model (DFM) and embedded discrete fracture model (EDFM) (Xu et al., 2019; Sepehrnoori et al., 2020).

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