RESUMEN
Dawsonite, as a natural CO2 tracing mineral, is intimately associated with CO2 injection and serves as a crucial mineral for geological carbon sequestration. The massive and stable presence of dawsonite in the geological background is a key consideration for CO2 mineralization capture and plays a significant role in identifying CO2 geological burial sites. To investigate the optimal conditions for the rapid synthesis of dawsonite using CO2, we conducted comparative experiments to examine the three primary influencing factors: temperature (100 °C, 120 °C, 140 °C, 160 °C, 180 °C, and 200 °C), pH (8.5, 9, 9.5, 10, and 10.5), and reaction time (6 and 12 h). Through scanning electron microscopy and X-ray diffraction analysis, the optimal conditions for dawsonite synthesis were determined. The experiments revealed that within the pH range of 8.5-10.5 and at temperatures of 100-180 °C, the dawsonite products obtained are consistently pure, which indicates that CO2 can be effectively mineralized and sequestered as dawsonite within these temperature and pH ranges. The synthesis yield increased and then decreased with increasing pH and temperature. At 200 °C, the crystallinity of dawsonite decreased and the content of pseudo-boehmite increased. This suggests that higher temperature conditions are not conducive to the mineralization and sequestration of CO2. Extending the reaction time did not have a significant promoting effect on the quality of the product. The maximum amount of dawsonite synthesis, good dispersion and homogeneity of crystals, and maximum ratio of mineralization of CO2 by dawsonite were achieved at a temperature of 140 °C and a pH of 9.5, indicating that these are the optimal conditions for the hydrothermal synthesis of dawsonite using CO2. Moreover, these are the optimal geological conditions for the mineralization sequestration of CO2 in the form of dawsonite.
RESUMEN
Authigenic chlorite is a common clay mineral in clastic rock reservoirs, and it has an important influence on the pore structure of tight clastic rock reservoirs. In this paper, the tight clastic reservoirs in the Lower Cretaceous Yingcheng Formation in the Longfengshan subsag in the Changling fault depression in the Songliao Basin were investigated. Polarized light microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), high-pressure mercury injection (HPMI), and low temperature nitrogen adsorption (LTNA) were used to study the influence of authigenic chlorite on the pore structure of tight clastic reservoirs. The results show that the authigenic chlorite in the study area was mainly generated in the form of pore linings. The formation of the authigenic chlorite was mainly controlled by the parent rock type and the sedimentary microfacies in the provenance area. The hydrolysis and dissolution of the iron- and magnesium-rich intermediate-mafic magmatic rocks and the high-energy, open, weakly alkaline reducing environment in the delta-front underwater distributary channel were the key factors controlling the formation of the authigenic chlorite in the study area. The pore-lining chlorite slowed down compaction and inhibited quartz overgrowth, protecting the original pores. Moreover, there are a large number of intercrystalline pores in the chlorite, which provided channels for the flow of acidic water and thus the formation of secondary pores, playing a positive role in the physical properties of the tight clastic rock reservoirs. However, the pore-filling chlorite also blocked the pore throats, playing a negative role in the physical properties of the tight clastic rock reservoirs. The tight clastic rock reservoirs with pore-lining chlorite generally had low displacement pressures and large pore throat radii. The morphology of the nano-scale pores was mainly parallel plate-shaped slit pores. There were many primary pores and a small number of secondary pores in the reservoir. Some of the pores were connected by narrow-necked or curved sheet-like throats, and the pore structure was relatively good. A higher relative content of chlorite led to a larger nano-scale pore throat radius, a smaller specific surface area, a smoother pore surface, and stronger homogeneity. Authigenic chlorite played a positive role in the formation of the tight clastic reservoirs in the study area.
