Dissolution kinetics and heterogeneous evolution of dolomite with different pore structures

Abstract

Mesogenetic dissolution is a critical process in the evolution and preservation of pore spaces in carbonate reservoirs. While limestone dissolution has been extensively studied, there is a lack of research on the dissolution kinetics of dolomite reservoirs, particularly regarding differences in dissolution mechanisms and heterogeneity evolution across various pore structures. This study aims to investigate diagenesis processes and heterogeneity evolution patterns in dolomites with different pore structures by simulating reservoir dissolution using organic acids generated during kerogen cracking. Flow system dissolution experiments were conducted on four dolomites with varying pore structures in 0.2% acetic acid under high-temperature (T = 40–160 °C) and high-pressure (P = 10–50 MPa) conditions. The chemical composition of the fluid and pore structure images were analyzed using ICP-OES and X-ray computed microtomography, respectively. Pore size distribution and evolution were assessed through digital cores based on Micro-CT analysis, while fractal and multifractal analyses were employed to quantify the evolution of pore structure heterogeneity. The findings highlight the importance of an effective combination of early material base and subsequent organic acid dissolution in the formation and maintenance of deep, high-quality dolomite reservoirs.