Chemistry and Technology of Fuels and Oils最新文献

Thermal pressurization of the trapped pore fluid is considered to be a widespread fault weakening during fluid injection in confined geological formations. Tremendous amounts of heats will be generated within the narrow shear zone during fault slip. Considering the melting of the fault gouge, the fault seal zone is adopted to construct the fluid pressurization model, thermal pressurization implemented in Comsol Multiphysics is established to illustrate the fault weaken coefficient and effective normal stress during fluid injection. The friction weakening coefficients m_T and m_F are proposed to research the performance of fault weakening during fluid injection. The results indicate that, the friction coefficients m_T and m_F both exhibit the initially decreasing and then increasing tendency, and thermal-induced fault weakening of CO₂ injection occurs earlier than that of water injection. It was found that initial pore pressure and fault sealing porosity have a negligible influence on the evolutions of friction weakening and effective normal stress. Initial normal stress and fault sealing permeability have certain obvious influences on fault weakening during CO₂ injection. Fault thickness is the primary factor influencing the friction weakening coefficient. When the fault thickness is over 1 mm, the variation of fault weakening is totally different from that when the thickness is less than 1 mm. This investigation of friction weakening during fault slip provides an effective reference for fluid injection.

Heihai Lake, a freshwater lake in the area of the East Kunlun Mountains is an accurate monitor of climate-driven hydrological and environmental changes during the past 2000 yr BP. In order to reconstruct the environment in the north Tibetan Plateau, we studied the multi-proxy records from Heihai lake sediments. Major analyses comprise mineral composition (XRD), morphology of minerals (ATEM), geochemical data (XRF), Ostracoda analysis and chronological framework based on AMS¹⁴C data. Climate was cold and dry since 1972 yr.BP of the Holocene, which was mainly physical weathering and with a weak chemical weathering. The sedimentary discontinuity happened during 1352 yr.BP and 352 yr.BP, is seen as the size of the lake shrink, which is in consistent with the extremely low temperature and dry climate conditions during the global Glacier Time. From the study, we can conclude that the climate of Tibetan plateau was unstable during the last 2000 years, and extremely cold and dry event happened on Tibetan plateau during the warmer Holocene in China.

CO₂ expansion flooding technology has the potential to significantly enhance oil recovery in low permeability and ultra-low permeability reservoirs, while also facilitating carbon capture, utilization, and storage (CCUS) to a certain extent. This paper provides a comprehensive review of the mechanism of CO₂ expansion flooding, the current research status of two main methods – self-generated expansion with viscosity reduction and gas injection expansion with viscosity reduction - as well as advancements in simulation studies on expansion flooding. Currently, achieving optimal CO₂ flooding conditions remains challenging due to limited availability of large-scale gas sources and concerns regarding equipment pipeline corrosion during transportation. Finally, this environmentally friendly CO₂ flooding technology is summarized and its future prospects are discussed.

The temperatures of the phase transitions for polyethyleneterephthalate samples containing recycled PET (the product Vivilen) and the waste materials from its production were analyzed by differential scanning calorimetry and x-ray structural analysis, and the ratio of the crystalline and amorphous phases was determined. The polyethyleneterephthalate samples were arranged according to their glass transition and melting points, which made it possible to correlate the samples according to the degree of crystallinity. In order to obtain a filament based on the dust waste from the solid-phase polycondensation process an extrusion temperature regime was established, and samples of filaments for 3D printing that meet the requirements of GOST R 59100-2020 were obtained.

An investigation was carried out on the feasibility of obtaining a reagent based on complex compounds for regulating the parameters of a drilling mud by introducing complex‑forming ferrous cations into a sodium lignosulfonate composition followed by additional modification with phosphonic compounds and obtaining a polyelectrolyte complex derived from anionic polyelectrolyte‑sodium lignosulfonate and modified cationic starch. The presence of functional groups in the sodium lignosulfonate sample studied capable of complexation was established by IR spectrometry. The determination of the optimal ratios of the starting components for the obtaining complex compounds using lignosulfonate, iron sulfate, and phosphonic compounds was carried by mathematical modelling with the Statistica 12 software package. The surface activity of the experimental samples was studied by a stalagmometric method (drop count method). The particle size distribution method using an SALD‑7101 laser analyzer was employed to study changes in the structure of the macromolecule of sodium lignosulfonate and a polyelectrolyte complex derived from sodium lignosulfonate and cationic starch. Obtaining a stable polyelectrolyte complex by selecting the optimal ratios of the anionic and cationic components involved measuring the dependence of the impedance of an electrochemical cell on the alternating currency frequency. The best mole ratio for preparation of the polyelectrolyte complex was 1:1. Feasibility was studied for using this lignosulfonate reagent based on complex compounds as a reagent for regulating the drilling mud parameters in the temperature range from 20° to 160-180°C.

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.