Chemistry and Technology of Fuels and Oils最新文献

Medium-coarse-crystalline dolomite is a major variant of dolomite, and its structural heterogeneity inside and outside the crystals makes it an ideal vehicle for studies of dolomite genesis, fluid evolution and elemental migration. In this paper, the medium-coarse crystalline dolomite from the fifth section of the Majiagou Formation of the Lower Ordos Basin was systematically studied by petrographic, cathodoluminescence and related geochemical methods. The rock is developed in the context of mud powder crystal dolomite and granular dolomite, possessing significant ring band structure, fluorite and quartz intergrowth. Compared with other dolomites, it is characterized by Fe and Mn enrichment and low Na and Sr contents, as well as a negative δEu anomaly and a strong negative δ¹⁸ O offset. Combined with the evolutionary history of diagenesis, it is believed that the medium-coarse-crystal dolomite is the end product of a series of diagenetic effects such as early dolomitization-atmospheric freshwater leaching-secondary burial recrystallization-deep burial dissolution. Electron microprobe analysis reveals the structural and compositional heterogeneity inside and outside the crystals. The formation of mediumcoarse- crystalline dolomite is associated with an increase in Fe-Mn content, a rise in the Mn/Sr ratio, a decrease in Sr, and a first rise and then a fall in Na concentration. This study provides a valuable reference for further research on the genesis of the medium-coarse crystalline dolomite.

Shale oil is currently a key area for unconventional oil and gas exploration and represents a new field to ensure national energy security. As a major contributor to unconventional oil and gas in China, Sichuan Basin has enormous potential as an oil and gas resource.The exploration of Jurassic shale oil reservoirs is in its infancy, with diverse reservoir lithology and the ability to store oil and gas. Therefore, whether the generated hydrocarbon substances in shale are still gathering in situ or have undergone short distance migration plays a guiding role in the formulation of the next oil and gas exploration and development plan. In this study, we focused on the shale oil reservoirs of Lianggaoshan Formation in northeastern Sichuan Basin. Firstly, the lithological characteristics of shale oil reservoirs, as well as the physical and geochemical characteristics of different lithological reservoirs were determined via core observations and conventional reservoir geological characteristic experiments. Secondly, Laser confocal scanning microscopy (LCSM) was used to conduct three-dimensional modeling and quantitative testing of the shale oil occurrence characteristics of different lithological reservoirs. Finally, based on the differences in the occurrence of hydrocarbons in different lithological reservoirs and the physical characteristics of rocks, hydrocarbon migration is traced.The following three insights were obtained based on the experimental results: The crude oil produced was primarily composed of light hydrocarbons.The physical properties of sandstone profiles are superior, with a higher proportion of light hydrocarbons compared to shale reservoirs.The above experimental results indicate that hydrocarbons generated in shale migrated over short distances and were enriched in adjacent sandstone and siltstone bands with relatively desirable physical properties. This study provides experimental means and data support for subsequent flowability evaluations and development plan preparation for Jurassic shale oil extraction in northeastern Sichuan.

Shale gas reservoirs usually have well-developed fractures and joints, and the fracturing development process is prone to forming complex fracture networks near the wellbore, which is not conducive to the effective migration and efficient development of shale gas. The development of temporary plugging agents related to shale fracturing reservoir transformation is a key technology to solve this problem in the shale gas development process. Therefore, a water-soluble preformed gel temporary plugging agent was developed, and its expansion/swelling characteristics and temporary plugging performance were analyzed through experiments. At the same time, experimental evaluation was conducted on its unblocking performance. Research has found that although there are differences in the swelling rate of temporary plugging agents at different stages, they gradually increase during plugging operations. The volume of the temporary plugging agent expanded nearly 8.24 times throughout the entire experimental process. In addition, temporary plugging agents can temporarily seal micro fractures and rapidly expand hydraulic fractures, thereby significantly improving shale gas recovery rate. The shale gas recovery rate when temporary plugging agents are used in fracturing operations is about 12.3% higher than when temporary plugging agents are not used. In addition, the increase in working fluid temperature and the concentration of surfactants will mostly stimulate the activity of water molecules, thereby stimulating the hydrolysis of temporary blocking agents in microcracks. Taking into account the development cost and efficiency, it is reasonable to control the temperature of the working fluid and the concentration of surfactant during the unblocking process after the fracturing operation between 110-140°C and 0.75 g/m3, respectively. In order to provide technical support and design basis for the efficient development of shale gas through this study.

Synthesized a kind of polyacrylamide konjac gum double network gel system, and studied the possibility of replacing mechanical bridge plug with this system. Studied the effects of covalent bond cross-linking, ionic bond cross-linking and monomer ratio on the mechanical properties of gel, including the stress-strain curve, elastic modulus, critical stretch and fracture energy. And conducted indoor simulation wellbore sealing experiments. The results show that the double network gel has higher strength than the single network gel, and the plugging ability of the well bore is greatly improved, which is expected to replace the mechanical bridge plug in construction.

In order to investigate the influence of primary production, dilution and preservation on organic matter accumulation, geochemical data and geochemical proxies of primary production, clastic influx and redox conditions were presented from the Cambrian Niutitang Formation organic-rich shales. The primary production proxies (TOC, Mo, P, Ba and Babio) and redox proxies (Ni/Co, V/Cr, U/Al and Th/U) suggest that the black organic-rich shales of the Niutitang Formation are deposited in anoxic/euxinic condition with high primary production. The pyrite of the Niutitang Formation is composed of spherical framboids, indicating that the anoxic bottom water could not prevail before organic matter degradation during the Niutitang Formation deposition. High primary production enhances organic carbon flux into chemocline layer and bottom water, leading to the anoxic bottom water from oxygen consumption by microorganisms and organic matter degradation. The anoxic bottom water in turn is beneficial to preservation of organic matter. In addition, Ti/Al ratios correlate well with TOC contents through the Niutitang Formation, indicating that clastic inputs enhance the burial rate for preventing organic matter from degradation during Niutitang Formation deposition. Therefore, the accumulation of organic matter in the Niutitang Formation is mainly influenced by primary production rather than the redox conditions in bottom water.

The CO₂ enhanced oil recovery(EOR) technology is widely utilized in the development of shale oil reservoirs. However, reservoir plugging issues often occur during the CO₂ injection process, leading to reduced onsite development efficiency. Currently, the mechanism behind reservoir plugging is still unclear. Therefore, this research selects Jimsar crude oil from Xinjiang to conduct CO₂ displacement experiments on shale cores and analysis of crude oil components. A comparative analysis is conducted with previous studies to explore the plugging mechanism. The research results demonstrate that core plugging occurs when the displacement pressure exceeds 25 MPa, resulting in a significant decrease in core permeability. Under a displacement pressure of 40 MPa, the additional resistance accounts for as much as 72% of the total resistance, with high asphalt content and the extractive effect of CO₂ on crude oil components being important factors leading to core plugging. Therefore, in the field development process, the CO₂ enhanced oil recovery technology should be applied in a rational and tailored manner according to the properties of the field’s crude oil.

Results are given for a kinetic study of the synthesis of a new fullerene derivative containing a diterpene fragment obtained using HPLC and subsequent mathematical modelling. Kinetic and activation parameters were found for the cyclopropanation of fullerene using the Bingel procedure and a reaction mechanism was proposed. The optimal synthesis conditions were found to entail a slight excess of a chlorine‑containing cyclopropanation agent and carrying out the reaction at room temperature.

Horizontal well development of natural gas hydrate (NGH) can greatly improve gas production and make it cost-effective, which is one of the key technologies for the efficient development of NGH in the future. World widely, there is only limited experience in drilling horizontal wells into gas hydrate sediments, which lacks certain reference. In this paper, the practice of drilling horizontal wells into gas hydrate sediments, were analyzed the challenges. The challenges encountered when drilling horizontal wells into hydrate sediments were also analyzed. At least, the application of horizontal wells and complex well structure, which based on horizontal wells are analyzed. The advantages and disadvantages of several novel well structure are compared. This paper will contribute to the development of natural gas hydrate of our country.

In order to improve the accuracy of gravity anomaly data processing, this study utilizes multi-scale surface fitting techniques (MSSF) to separate the Bouguer gravity field into residual gravity fields and regional gravity fields at different depths. By sequentially stripping away layers, the residual gravity anomalies of the target layer are obtained as the data basis for subsequent gravity interpretation. This study selects appropriate parameters and establishes different lithology forward modeling templates based on actual geological data in the study area. The method is verified to accurately separate gravity anomalies generated by different density bodies, with accurate anomaly locations, complete shapes, and clear boundaries. It can also serve as a quantitative template for rock properties and provide theoretical references for practical cases. Additionally, the method exhibits high noise resistance, resolution, and accuracy. The practical application of the method is validated through microgravity monitoring data in carbonate reservoirs in western China and time-shifted microgravity monitoring data in tight sandstone reservoirs. The results demonstrate that the obtained residual gravity anomaly data of the target layer can effectively reflect the distribution of reservoir fluids.

The Longmaxi Formation in the Sichuan Basin is a hotspot formation for shale gas exploration. In this paper, taking the Longmaxi Formation shale in Yuxi area as an example, a large number of TOC tests, X-diffraction whole-rock mineral fraction tests, electron microscope observations, physical properties, gas content, and CT scanning experiments were carried out, which in turn analyzed the characteristics of the shale gas reservoir and the factors influencing the gas content. The results of the study show that there are seven types of shale facies developed in Yuxi area, which are organic-rich siliceous shale facies (I), organic-rich carbonate-siliceous shale facies (II), organic-rich clayey shale facies (III), organic-poor clayey shale facies (IV), organic-poor carbonate-siliceous shale facies (V), organic-poor siliceous shale facies (VI), and organic-poor siliceous-carbonate shale facies (VII). The microstructural characteristics of the shale reflect that it was disturbed by multiple environmental factors at the time of deposition, and the sources of brittle minerals include both terrestrial clasts and biogenic siliciclastics. The bottom 30 m shale of Longmaxi Formation has good physical properties and gas content, which is a high-quality target section for shale gas exploration and development. TOC, R_o, permeability, quartz content and clay mineral content all have a significant effect on shale gas content and are important control factors for shale gas content.