Hydraulic fracturing creates a complex fracture geometry in heterogeneous formations which are frequently simulated using Finite Element based fracture propagation modelling tools. Representing this geometry in Finite Difference based multiphase flow simulators poses some challenges. In this study, a Fracture Upscaling Method (FUM) is developed to represent complex fracture systems generated by the finite element method. It is demonstrated that this method can capture complex fracture geometries even when using coarse grids. This upscaling method can be used as a coupling tool between the output of any discrete fracture model and any finite difference-based reservoir simulator. FUM is tested against a field case and simulation results show a reasonable match with 120 days of production data. This method is then used to investigate the impact that natural fractures have on production from shale gas wells. The results show that the effect of orientation, spacing and length of natural fractures, on propagating hydraulic fractures can reduce the recovery factor by 30%. Furthermore, the ability of FUM to combine highly complex fracture networks with realistic multiple layer models with complex distributions of reservoir properties is demonstrated.
The authors would like to thank the School of Engineering at the University of Aberdeen for financial support and providing the required facilities to complete the study. Support from Computer Modelling Group and Schlumberger for the use of their software packages is greatly acknowledged. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
- Hydraulic fracturing
- Fracture patterns
- Finite difference simulations
- Discrete fracture models