Abstract
Reservoir quality and productivity of fractured gas reservoirs depend heavily on the degree of fracture development. The fracture evaluation of such reservoir media is the key to quantify reservoir characterization for the purposes such as well drilling and completion as well as development and simulation of fractured gas reservoirs. In this study, a pore-fracture network model was constructed to understand the effects of fracture on permeability in the reservoir media. The microstructure parameters of fractures including fracture length, fracture density, fracture number, and fracture radius were analyzed. Then two modes and effects of matrix and fracture network control were discussed. The results indicate that the network permeability in the fractured reservoir media will increase linearly with fracture length, fracture density, fracture number, and fracture radius. When the fracture radius exceeds 80 µm, the fracture radius has a little effect on network permeability. Within the fracture density less than 0.55, it belongs to the matrix control mode, while the fracture network control mode is dominant in the fracture density exceeding 0.55. The network permeability in the matrix and fracture network control modes is affected by fracture density and the ratio of fracture radius to pore radius. There is a great change in the critical density for the matrix network control compared with the fracture network control. This work can provide a better understanding of the relationship between matrix and fractures, and the effects of fracture on permeability so as to evaluate the fluid flow in the fractured reservoir media.
Highlights
As a special complex gas reservoir, fractured gas reservoir takes a large proportion of gas reservoirs found at home and abroad, which is playing an increasingly important role among energy sources and has attracted wide attention (Li et al, 2017; Shen et al, 2014, 2015)
Fracture length and fracture density are the important parameters in the characterization of the permeability evolution in the fractured reservoir media, which plays a key role in estimating elastic rock properties, fracture porosity, path length, and connectivity for fluid flow of fractured rock (Mauldon et al, 1999)
According to the above results, the following conclusions can be drawn: (1) With fracture length, fracture density, fracture number, and fracture radius increasing, the network permeability in the pore-fracture media will increase linearly and favor fluid flow in the fractured reservoir media, while the fracture radius has a little effect on network permeability when the fracture radius exceeds 80 mm. (2) The control modes of matrix and fracture network are affected by the fracture density
Summary
As a special complex gas reservoir, fractured gas reservoir takes a large proportion of gas reservoirs found at home and abroad, which is playing an increasingly important role among energy sources and has attracted wide attention (Li et al, 2017; Shen et al, 2014, 2015). The pore-fracture network model is an effective method to understand the micro-mechanism of fluid flow in the fractured reservoir media with great heterogeneity and a multi-scale pore structure consisting of fractures, pores, and throats. A pore-fracture network model was constructed to understand the effects of fracture on permeability in the fractured reservoir media.
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