Classification Method of High Permeability Sandstone Reservoirs Based on Fractal Theory

The K Oilfield’s salt-above reservoir belongs to high-permeability reservoirs, with an average porosity of 35.8% and an average permeability of 577.6 mD. Conventional single physical property parameters are insufficient to accurately characterize the reservoir properties and internal pore structure features. To clarify the relationship between physical properties and pore structure parameters in the K salt-above reservoir, this paper summarizes the basis for reservoir classification. Based on identifying the main pore types in the formation, fractal theory is applied to analyze the formation’s physical property parameters and high-pressure mercury injection experimental data. Ultimately, the interrelationships among physical properties, pore structure, and fractal dimension are obtained. For high-permeability sandstone reservoirs, it is challenging to establish a relationship between a single physical property and fractal dimension. This paper introduces the correlation coefficient (R2) between the logarithmic relationship of mercury saturation and capillary pressure as an additional parameter to characterize the pore-throat features of the samples. By integrating fractal dimension and the correlation coefficient (R2), the classification boundaries of the reservoirs are determined, and the salt-above reservoirs are categorized into three classes based on physical properties and pore-throat characteristics. The final classification results are consistent with the actual reservoir features and production performance, validating the effectiveness of this method. This method also provides a new quantitative approach to evaluate the complexity of reservoir pore structures, and offers a new perspective for studying reservoir heterogeneity and is of great significance for improving the efficiency of oil and gas exploration and development.