Research On Fractal Characteristic Of Pore Structure And Permeability Model In Sandstone Reservoirs

Researching the pore structure have important significance for the problems encountered in oil filed exploitation.The pore structure of reservoir rock is complex and irregular,and the traditional physical and chemical experiment methods are difficult to quantify.The fractal theory provides the possibility to study the law behind the complex phenomenon in nature.Based on the fractal theory,the physical properties of sandstone samples were systematically studied from two-dimensional and three-dimensional dimensions.Fractal dimension can be used to describe the complex pore structure morphology,and its value can analyze the microscopic reservoir heterogeneity.The models of figuring out the fractal dimension of reservoirs.However,after a series of data analysis,the results are different according to different models.In this paper,a large number of mercury injection experimental data are used to study different fractal dimension algorithms.The results show that the three dimensional capillary cube model has the strongest correlation between the fractal dimensions and rock physical properties,and it shows the most rationality to analysis the pore structure in low permeability.By using the box counting method to study the digital core image,it is found that the accuracy of the box counting dimension is closely related to the resolution and the selection of self-similar intervals.After some derivation and data analysis,it is found that different fractal dimensions have different effects on permeability prediction,and different fractal dimension calculation methods should be selected for different models when performing permeability prediction.Two-dimensional fractal dimension should be used to calculate permeability in 2D fractal permeability model,the fitting result is over 80%,so the feasibility is high;D_f44 should be used to calculate permeability in 2D fractal permeability model,the fitting degree is more than 90%;the fitting effect of Winland r₅ model is more than 90%,and it is highly feasible;the permeability prediction model based on the box-counting fractal dimension is accurate.The degree reaches more than 80%,so it is also feasible.