Size Effect on Pore-Scale Variables and Heterogeneous Pore-Network Characteristics in Carbonate Rocks

Pore-scale variables, specifically porosity and permeability, are vital in deep resource exploration projects like geothermal energy and shale gas. Digital rock measurement techniques (DRMTs) are commonly employed to match these variables with experimental results. However, limited attention has been given to identifying errors and size effects on pores and pore scale variables, as well as spatial heterogeneous characteristics of pore-networks. In this research, we define pore scale variables and investigate the size effects on these variables through statistical analysis. Additionally, we propose novel empirical formulas for predicting porosity and permeability based on X-ray CT images acquired at varying resolutions from the same carbonate rock sample. Our results indicate that the scanning direction has minimal influence on the physical and hydraulic properties, while these properties are significantly affected by image resolution. The porosity and permeability calculated using the proposed formulas show good agreement with experimental results, with errors below 10%. Consequently, the proposed formulas prove to be effective and reliable in evaluating physical and hydraulic properties based on DRMTs.