Application of Discrete Fracture Network Model in the Simulation of Massive Fracking in Tight Oil Reservoir

Abstract

Because of the ultra-low permeability of tight oil reservoirs and the limited seepage from matrix to fracture, the traditional bi-wing fracking method is not as productive as expected. Massive fracking technology can form complex fracture networks and large drainage areas by multi-stage/multi-cluster perforation and injection of low-viscosity fluids. Because of these differences, the traditional bi-wing planar model is not applicable in the simulation of massive fracturing, and a new network model is needed. The pseudo-three-dimensional (P3D) discrete fracture network (DFN) model was firstly used in the simulation of fracture network in shale gas and coal bed methane (CBM). The mass and momentum conservation equations are based on self-similar solution methodology, and the fracture characteristics are then calculated numerically. To investigate the suitable model for massive fracturing, we performed a comparison between DFN model and cluster facture model through the integration of rock mechanics, well logging, and micro-seismic detection technology. After mini-fracture analysis and closure analysis, parameters like instantaneous shut-in pressure (ISIP), closure pressure, and reservoir permeability were obtained. Pressure history matching and SRV matching were performed, and the results showed that DFN model works better than the cluster fracture model in the matching. The research proves the feasibility of DFN model in the simulation of massive fracking in tight oil reservoirs. Application of this integrated technology and DFN model may provide a theoretical basis for massive fracturing and a systemic method for mini-fracture analysis, fracturing design, SRV estimation, and multi-stage perforation optimization.