Pore Structure and Fractal Characteristics of the H Formation of the K Structure in the Eastern X Depression

Abstract

To address the limited understanding of the pore structure in the H reservoir of the K structure in the eastern X depression, a fractal analysis method was employed to analyze the reservoir pores. Through the integration of experimental techniques, including casting thin sections, X-ray diffraction, and mercury intrusion, the study identified the reservoir's pore types, pore-throat distribution characteristics, and fractal properties. Additionally, it explored the relationships between fractal dimensions, reservoir physical properties, pore structure parameters, and mineral compositions.The results indicate that the pore types in the reservoir of the study area are primarily primary intergranular pores, intergranular dissolution pores, and intragranular dissolution pores. The reservoir's mineral composition is dominated by quartz and feldspar, with chlorite being the most abundant among clay minerals.Based on the morphology of capillary pressure curves, the reservoir pore structures are classified into four types: Type I, Type II, Type III, and Type IV. Their storage capacity and permeability decrease sequentially, while heterogeneity gradually increases.The reservoir pores exhibit multifractal characteristics, with the pore space divided into macropores (megapores and macropores), mesopores, and micropores (micropores and nanopores). The pore structure of macropores and mesopores is superior to that of micropores. The fractal dimension is unrelated to reservoir porosity but shows good correlations with permeability, pore structure parameters, and mineral composition.This study reveals the pore size distribution characteristics of the reservoir from the perspective of multifractal theory, providing a basis for the development of the H reservoir in the K structure of the X depression in the eastern region.