Quality Enhancement of μ-CT Scanned Shale Images and Optimization of Experimental Conditions

Abstract

Micrometer CT scanning (μ-CT) is a crucial technique for three-dimensional characterization of pore structures, but both the scanning resolution and scanning outcomes are constrained by several factors. This paper selects shale samples from a section of the Wufeng−Longmaxi Formation in the Luzhou block in southern Sichuan, prepares samples of different sizes and water-bearing conditions, investigates the characteristics of pore development, connectivity, and structural variability of different samples through μ-CT scanning combined with digital image processing technology, and selects the optimal experimental conditions for μ-CT scanning. The results show that the smaller the shale sample size, the higher the accuracy and resolution of the CT image and the more accurate the identification of pore fractures. Moisture in the sample can make the values obtained from CT scanning higher, affecting the identification of pores. Sporadic water at the edge of the pore space and in the pore space will not change the number of pores but will reduce the pore volume; complete water in the pore space will reduce the number of pores and the pore volume; the pore space is separated by the endowment of water into a number of zones; and when the pore space increases, the number of pore spaces and pore volume decrease. Therefore, the smaller the size of the shale samples after drying, the higher the quality of the CT images and the more accurate the identification of the pores. This result can provide more accurate experimental conditions for μ-CT shale porosity research reference.