Novel evaluation of fracture-type reservoir based on optimization inversion of Sphere-Fracture Model

It is still a challenge for evaluating fracture-type reservoirs in the complex oil and gas fields, and the exploration requirements of this fracture reservoir are increasing day by day. In this paper, all the porous space in the fracture-type reservoir can be categorized into two basic types, the fractures and the pores. Then, the fractures and the pores are superimposed to form a Sphere-Fracture Model (SFM) under the configuration of different sizes. According to the SFM, an approach for the parameter optimization of pore structure is developed in this study. Combined with the existing inversion algorithms, an optimized algorithm for NMR (Nuclear Magnetic Resonance) logging echo is developed and it can be used for determining the average fracture width, the radius of spherical pore, the sorting coefficient, the kurtosis, and other pore structure parameters as well. From the comparative analyses of the pore structure parameters with the reservoir quality factor and oil and gas production, it can be found that the pore structure parameters show a good correlation with both the reservoir quality factor and the formation testing production, which illustrates that the pore structure parameters derived from the inversion of the SFM show a good performance in describing the physical properties of the fracture-type reservoir. Thus, our investigations in this paper enable to provide a potential application to improve the evaluation of fracture-type reservoir.