Estimating the Relative Permeability from the Electrical Parameters of Sandstone with a Complex Pore Structure

Abstract

Relative permeability is a crucial parameter for reservoir fluid-producing evaluation. In clay-free rock, water flow and electric current are dependent on the same controlling factors. The impact of pore structure on rock electrical properties and fluid flow is significant when calculating relative permeability from electrical properties in complex pore structure sandstone. In this paper, the pore geometry of complex pore structure sandstone is equivalent to tubular-and micromembrane-like shapes. A conduction model and a fluid flow model for two shapes of pores are studied. The study result shows that the flow path of water is the same as the conductive path in tubular-like-shaped pores; however, in micromembrane-like-shaped pores, water does not flow but electric current flows. Based on the above, the relative permeability calculation method from electrical properties in complex pore structure sandstone is proposed. A total of 16 rock samples selected from a complex pore structure reservoir of Dongying Formation in Nanpu Sag are used to verify the validity of the relative permeability calculation method. Rock samples are classified into five pore size distribution types according to NMR experimental data; for each type, relative permeability is calculated using the new method. The result shows that the new method-calculated relative permeability is in accordance with the experimental values and parameter calculation accuracy is improved. The relative permeability calculation method from electrical properties in complex pore structure sandstone has good application prospects and can provide important guidance for high-precision evaluation of complex pore structure reservoirs and research of rock mechanical characteristics.

Research on the Shale Porosity–TOC Maturity Relationship Based on an Improved Pore Space Characterization Method

“…Shale pore evolution is a combined result of permeability, fluid pressure, formation temperature, thermal maturity, etc. It has a vital influence on geophysical response parameters, such as formation velocity, density, resistivity, and the NMR T2 spectrum [31,32]. Inorganic pores of shale are mainly controlled by diagenesis and fluid interaction [33,34], while organic pores are influenced by different factors during different stages.…”

Nuclear Magnetic Resonance T2 Distribution-Based Gas–Water Relative Permeability Prediction in Tight Sandstone Reservoirs: A Case Study on Central Sichuan Basin, China

“…The methods for obtaining relative permeability are mainly classified into experimental measurement methods and model prediction methods. − At present, the experimental measurement is the main method to obtain the relative permeability curve in the oilfield, and it has achieved good application results in conventional oil and gas reservoirs. − Due to the complex pore structure and strong heterogeneity of tight sandstone reservoirs, measuring relative permeability by experimental methods is challenging; , many scholars have established mathematical models to predict relative permeability. − Based on the relationship between relative permeability and measured capillary pressure–saturation curves, relative permeability can be predicted through the capillary pressure curves. According to Purcell’s (1949) permeability prediction method, Burdine (1953), Corey (1954), and Brooks and Corey (1966) proposed a relative permeability model based on capillary pressure.…”