New insights into the dolomitization and dissolution mechanisms of dolomite-calcite (104)/(110) crystal boundary: An implication to geologic carbon sequestration process

• Published in: The Science of the total environment 2023-12, Vol.904, p.166273-166273, Article 166273
• Main Authors: Zhu, Guangyou, Wei, Zhenlun, Wu, Xiaoyong, Li, Yubiao
• Format: Article
• Language: English
• Subjects: Boundary dissolution; Carbonate reservoirs; Dolomitization; Geologic carbon sequestration
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.166273

Geologic carbon sequestration (GCS) is a promising strategy to reduce the harm of CO2 due to the rapidly increased fossil fuel combustion. Dolomitization and dissolution processes of deeply buried carbonate reservoirs significantly impact the potential of GCS. However, previous investigations mainly focus on the macroscopic batch experiments, the mechanisms at atomic level are still unclear especially for crystal boundary, but urgently required. Herein, the GCS potential and the effects of boundary dissolution on calcite and dolomite were investigated based on both analytical and simulation methods such as molecular dynamics simulation (MDS) and density functional theory (DFT) calculations, to deeply unveil the mechanisms of dolomitization and formation of intergranular secondary pores from the atomic perspective. The morphology results indicated that the dissolution of calcite and dolomite in carbonic acid solution started via the edges and corners. In addition, the simulated results showed that the carbon sequestration potential presented an order in dolomite (PMg50%) > PMg40% > PMg30% > PMg20% > PMg10% > calcite by dolomitization due to the reduced bulk volume but increased lattice stress. Furthermore, both electrons transfer and diffusion coefficients results suggested that the (104)/(110) boundary was preferentially dissolved as compared to the (104) and (110) planes, indicating that crystal boundary was beneficial to the formation of pores for the oil and gas storage, but harmful to the stability of long-term GCS. Therefore, this study, for the first time, provides new insights into uncovering the mechanisms of the GCS process in depth, from an atomic level focusing on the crystal boundary, thereby promoting the understand of the long-term evolution for both calcite and dolomite in deep reservoirs. [Display omitted] •Dolomitization and carbonates dissolution mechanisms were revealed at atomic level.•Carbonate dissolution rate decreases with increasing dolomitization degree.•GCS potential follows: dolomite >PMg40% > PMg30% > PMg20% > PMg10% > calcite.•Surface activities follow: (104)/(110) > (110) > (104) for calcite and dolomite.•Calcite dissolves faster than dolomite in carbonic acid solution.