Dissolution and Deformation Characteristics of Limestones Containing Different Calcite and Dolomite Content Induced by CO₂‐Water‐Rock Interaction

Abstract

To investigate the impacts of mineral composition on physical and mechanical properties of carbonate rocks, limestone specimens containing different contents in calcite and dolomite are selected to perform CO2‐water‐rock reaction experiments. The X‐ray Diffraction (XRD) and Nuclear Magnetic Resonance (NMR) are carried out to examine the change characteristics of mineral dissolution and pore structure after reaction. The core flooding experiments with Fiber Bragg gratings are implemented to examine the stress sensitivity of carbonate rocks. The results show that the limestones containing pure calcite are more susceptible to acid dissolution compared to limestone containing impure dolomite. The calcite content in pure limestone decreases as the reaction undergoes. The dissolution of dolomite leads to the formation of calcite in impure limestone. Calcite dissolution leads to the formation of macropore and flow channels in pure limestone, while the effects of impure dolomite in impure limestone results in mesopore formation. When confining pressure is lower than 12 MPa, pure limestones demonstrate higher strain sensitivity coefficients compared to impure limestone containing dolomite after reaction. When confining pressure exceeds 12 MPa, the strain sensitivity coefficients of both pure and impure limestones become almost equal.

SC-CO2 and Brine Exposure Altering the Mineralogy, Microstructure, and Micro- and Macromechanical Properties of Shale

“…The dissolution sequence of minerals in an acidic solution is carbonate (eqs and ) > clay minerals (eqs and ) > feldspar (eqs and ) > quartz (eq ), in which carbonate is the most easily dissolved and quartz is the most stable. Previous investigations have also confirmed the alternation patterns of these mineral compositions. ,, Under the acidic conditions of SC-CO 2 + brine, the dissolution of carbonates, clay minerals, and feldspar leads to a reduction in their relative proportion. Further, the phenomenon of an increase in quartz was related to the following: (i) Although quartz can be dissolved under high temperature and pressure, the degree was very weak (eq ).…”

“…Consequently, during CO 2 injection to extract shale oil, the fluid interacting with the shale is not only pure CO 2 but also pure brine and CO 2 + brine. In the presence of formation mineralized water, CO 2 can also react with formation water to generate an acidic solution. , Shale minerals have a larger probability of undergoing dissolution and precipitation in an environment with acidity, which can significantly alter the physical properties of shale reservoirs. Zhou et al compared the mechanical properties of shale specimens before and after soaking in different fluids (pure CO 2 , pure brine, and combined soaking conditions).…”

Advances in the Experiments of Leaching in Cement-Based Materials and Dissolution in Rocks

“…Figure 5 shows the XRD diffractograms of a marble sample after dissolution; the chemical composition can be seen from the perspective and shape of the peaks. The XRD technology can perform phase analysis of samples, and the changes in the relative content of a certain component before and after leaching can be analyzed through X-ray diffraction patterns [69]. For example, XRD can be used to compare the differences in mineral composition of sandstone cores before and after dissolution [70], study the order degree of rocks such as dolomite [71], and judge the differences in hydration products of cement [72].…”

Effect of freez thaw on the solubility the Mesozoic limestone (a case study: Iran, Dorfak karstic area, Guilan province, North of Iran)

“…The solubility value of carbonate rocks has been studied by various researchers all over the world. Including: Ajalloeian, et al, (2001);Ghobadi, (2005); Heidari, et al, (2011);Taheri, et al, (2016); Mousavi-Maddah, et al, (2020);Taheri, et al, (2021); Mohammadian, et al, (2021); Gessert and Hochmuth, (2022);Chen, et al, (2023);Hou, et al, (2023).…”