The research presented here investigates the reaction mechanism of wollastonite in situ mineral carbonation for carbon dioxide (CO₂) sequestration. Because wollastonite contains high calcium (Ca) content, it was considered as a suitable feedstock in the mineral carbonation process. To evaluate the reaction mechanism of wollastonite for geological CO₂ sequestration (GCS), a series of carbonation experiments were performed at a range of temperatures from 35 to 90 °C, pressures from 1500 to 4000 psi, and salinities from 0 to 90,000 mg/L NaCl. The kinetics batch modeling results were validated with carbonation experiments at the specific pressure and temperature of 1500 psi and 65 °C, respectively. The results showed that the dissolution of calcium increases with increment in pressure and salinity from 1500 to 4000 psi and 0 to 90000 mg/L NaCl, respectively. However, the calcium concentration decreases by 49%, as the reaction temperature increases from 35 to 90 °C. Besides, it is clear from the findings that the carbonation efficiency only shows a small difference (i.e., ±2%) for changing the pressure and salinity, whereas the carbonation efficiency was shown to be enhanced by 62% with increment in the reaction temperature. These findings can provide information about CO₂ mineralization of calcium silicate at the GCS condition, which may enable us to predict the fate of the injected CO₂, and its subsurface geochemical evolution during the CO₂–fluid–rock interaction.

Turbidite-associated black shale of the Semanggol Formation is extensively distributed in the northwestern part of the Western Belt, Peninsular Malaysia. The black shale occurs as a dark grey to black and thick to medium-bedded deposit. It represents the distal part of submarine fan system (outer-fan) overlying interbedded sandstone to shale facies of the mid-fan and conglomeratic pebbly sandstone facies of the inner-fan. Field observations and its widespread occurrence have resulted in the black shale being considered as a potential analog for a source rock in offshore Peninsular Malaysia. The present study includes detailed mineralogical (XRD, SEM, and EDX analysis), inorganic geochemical (major oxides, trace elements TEs, and rare earth elements REEs), and Rock-Eval pyrolysis analyses of the black shale samples, collected from the Gunung Semanggol, Bukit Merah, and Nami areas in northwestern Peninsular Malaysia. The primary focus of this study is to investigate the provenance, paleoredox conditions, paleoclimate, sedimentary rate, paleoproductivity, and upwelling system that would be helpful to understanding the role of these parameters in the enrichment of organic matter (OM) in the black shale. The Rock-Eval analysis shows that the black shale of the Semanggol Formation comprises type-III kerogens, which suggests organic input from a terrestrial source. The black shale also contains mature to postmature organic matter. Based on the mineralogical analysis, the mineral composition of the black shale comprises illite and kaolinite, with abundant traces of quartz and feldspar as well as few traces of titanium and zircon. Inorganic geochemical data designate black shale deposition in a passive margin setting that has experienced moderate to strong weathering, semi-arid to hot arid climate, and moderate sedimentation rate. Ratios of Ni/Co, U/Th, and V/(V+Ni) along with slightly negative to positive Ce* anomalies and U_EF-Mo_EF cross-plot unanimously indicate anoxic/dysoxic water conditions that are suitable for organic matter preservation. Geochemical proxies related to modern upwelling settings (i.e., Cd/Mo, Co vs. Mn) show that the deep marine black shale was strongly influenced by persistent upwelling, a first-order controlling factor for organic matter enrichment in the distal part (outer fan of the submarine fan system) of the Semanggol Basin. However, productivity-controlled upwelling and a high sedimentary rate, as well as high-productivity in oxygen-depleted settings without strong anoxic conditions, has played an essential role in the accumulation of organic matter.

Geological storage of carbon dioxide (CO₂) requires the host rock to have the capacity to permanently store CO₂ with minimum post-storage monitoring. Mineral carbonation in geological formations is one of the most promising approaches to CO₂ storage as the captured CO₂ is converted into stable carbonated minerals (e.g., calcite and magnesite). In this study, we investigated the geochemical and mineralogical characteristics of Segamat basalt in the Central Belt of Malaysia and evaluated its potential for mineral carbonation by using laboratory analyses of X–ray fluorescence (XRF), X–ray diffraction analysis (XRD) and petrographic study. The XRF results showed that Segamat basalt samples contain a number of elements such as Fe (21.81–23.80 wt.%), Ca (15.40–20.83 wt.%), and Mg (3.43–5.36 wt.%) that can react with CO₂ to form stable carbonated minerals. The XRD and petrographic results indicated that Segamat basalt contains the reactive mineral groups of pyroxene and olivine, which are suitable for the mineral carbonation process. The results of this study could help to identify the spatial distribution of elements and minerals in the Segamat basalt and to assess its mineral carbonation potential for geological storage in Malaysia.

Clay mineral content and diagenetic processes are vital factors that affect reservoir quality, especially in tight clastic reservoirs, which are crucial for industrial and scientific purposes. The presence of clay minerals poses one of the most significant challenges in evaluating sandstone reservoirs’ quality. Even though wireline logs may provide a good indication of the reservoir quality, there have been cases where they have failed. This work focuses on the clay minerals’ impact on the porosity and permeability of a clastic reservoir. Typical outcrops from Labuan Island, Brunei–Sabah Basin, were chosen as a case study to investigate the petrophysical and petrographic parameters together with clay mineralogy profiling. The effects of the clays on the petrophysical parameters of the sandstone reservoir were evaluated through air permeability, spectral gamma ray measurements, a petrographic thin section analysis, a visual porosity estimation, and a grain size analysis. Field and petrographic studies revealed that Belait and Temburong formations contain massive, interbedded, laminated, and cross-bedded sandstones. Using an image analysis of the thin sections, porosity values ranged from 7.3% to 23.5%, with different macro and micro porosity distributions. According to the spectral gamma-ray investigation and air permeability, permeability reduction is strongly associated with clay minerals. The microporosity and permeability of the analyzed samples showed a unique pattern influenced by the grain size distribution. It was found that the textures dominated by mud grain size had a more significant impact on the air permeability and visual porosity, with coefficient of determination values of 0.83 and 0.70, respectively. The Belait Formation displayed a higher porosity and permeability compared to the Temburong Formation. This research provides new insight into the potential reservoir of Stage IV (the Belait Formation offshore equivalent) compared to Stage II (the Temburong Formation offshore equivalent).

There is a recognized need for the determination of total organic carbon (TOC) as an essential factor in the evaluation of source rocks. In this study, the ∆LogR technique was coupled with logging curves of sonic, resistivity, spectral gamma-ray (SGR), and computed gamma-ray (CGR) to determine an accurate content of TOC in the Gadvan Formation. Multiple linear regression analysis was also applied to the ∆LogR technique. To this aim, 14 samples of the Gadvan Formation were taken from Wells B and C in the South Pars field and analyzed using Rock-Eval pyrolysis. Results from the ∆LogR technique and multiple linear regression analysis, well logs, and Rock-Eval were compared to calculate the accurate content of TOC in the Gadvan Formation. Geochemical data confirmed that the Gadvan Formation was a relatively poor source rock in the South Pars field, as average TOC and T_max values of the samples were 0.79 and less than 430 °C, respectively. Also, the content of potassium (K < 0.1%) confirmed the origin of the source rock as a pure carbonate, whereas the low content of thorium (Th < 5 ppm) was indicative of the percentage of clays. There was a moderate content of uranium (U < 10 ppm), suggesting that the Gadvan Formation was not deposited in an excellent reducing environment to conserve the organic matter. Moreover, the results from the integration of the multiple linear regression model with SGR and CGR showed that the value of R² was higher than the results obtained without SGR and CGR. Findings from this study could help the exploration and production team to determine the accurate content of TOC using the ∆LogR technique in association with logging curves.