## 1 Introduction
### Shale Interactions (Multi-Mineral)
After dry scCO\({}_{2}\) exposure, the largest changes seen were the increase in calcite content of 3% and a decrease in dolomite of 4.2%. However, [PERSON] et al. [53] made clear that analytical errors (of up to 3%) and inherent heterogeneity between samples meant that the XRD method was not diagnostic of mineral reactions. In addition, SEM-EDS results showed calcite surfaces were corroded and made rugged due to dissolution, but with reprecipitation elsewhere, such that there was little net mass loss to the fluid phase. The growth of fibres and needles of salt (halite and anhydrite) was observed on pyrite surfaces and on calcite grain boundaries. [PERSON] et al. [53] suggested that the alteration of calcite and pyrite was likely enabled by the presence of water retained in the pores. This water evaporates into the dry scCO\({}_{2}\), carrying dissolved materials and precipitating elsewhere at the rock/gas interface. Mercury porosimetry tests showed that there was no overall porosity change after submersion in dry CO\({}_{2}\). A set of five studies from the same group based in Chengdu, China, was undertaken concerning the evolution of rocks following treatment with CO\({}_{2}\)[17; 33; 36; 54; 55]. The shale samples studied in this work came from the Longmaxi formation, the Wufeng formation, and the Yanchang formation. All contained various amounts of quartz, calcite, dolomite, feldspar, pyrite, and clay. The clay component was made up of illite, kaolinite, chlorite, and mixed layer illite/smectite. The TOC ranged from 2-5.6%. the experimental setups were very similar across the five studies, but the exposure times and temperature and pressure conditions tested were different. [PERSON] et al. [33] focused on how varying pressure (8-18 MPa) or temperature (40 \({}^{\circ}\)C-90 \({}^{\circ}\)C) affected pore structure changes over just 4 days. They found that as pressure increased, specific surface area and porosity slightly increased. This was said to be due to the scCO\({}_{2}\) fluid density increasing and so the capability of dissolution into the water film also increased [33]. The temperature value was described as having a positive impact on dissolution at higher pressures (>16 MPa) but little effect below this. [PERSON] et al. [54] looked at longer-term reactivity over 30 days (T = 40 \({}^{\circ}\)C, P = 16 MPa). They used SEM, XRD, FTIR, and adsorption techniques. The specific surface area and number of micropores were found to decreased sharply, whereas the average pore size was enlarged. The fractal dimension of the shale was also reported to decrease. This implies a smoothing of the surface, which conflicts with the findings of aforementioned papers, in which pitting and etching were observed. [PERSON] et al. [17] treated Longmaxi shale with CO\({}_{2}\) at 15 MPa and 35 \({}^{\circ}\)C for periods of 24, 48, 72, 96, and 120 h. Using low-pressure nitrogen adsorption data, they reported that the specific surface area of the shale had decreased, whereas the porosity and average pore size increased. Pores close to 2.32 nm were primarily enlarged. Complementary XRD data showed that the content of all minerals, except quartz, decreased. [PERSON] and co-workers [36; 55] treated various shales with scCO\({}_{2}\) at 15 MPa and 80 \({}^{\circ}\)C, with serial sampling after 10, 20, and 30 days. XRD was used to find the mineralogy before and after treatment, but [PERSON] et al. [36; 55] suggested that this type of analysis may not accurately detect the small changes that occurred in the minerals, and the sample heterogeneity itself may lead to variations of up to 5%. Elemental analysis was thought to be a more robust technique, and this showed that the carbon and hydrogen elemental content changed with increasing treatment time. Initially, the content of both elements decreased slightly after 10 days, before increasing thereafter. These results were attributed to the extraction of organic matter, as well as the chemical reactions in shale minerals caused by scCO\({}_{2}\).