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Laboratory experiments, numerical simulations and fracturing technology were combined to address the problems in shale oil recovery by CO2 injection. The laboratory experiments were conducted to investigate the displacement mechanisms of shale oil extraction by CO2 injection, and the influences of CO2 pre-pad on shale mechanical properties. Numerical simulations were performed about influences of CO2 pre-pad fracturing and puff-n-huff for energy replenishment on the recovery efficiency. The findings obtained were applied to the field tests of CO2 pre-pad fracturing and single well puff-n-huff. The results show that the efficiency of CO2 puff-n-huff is affected by micro- and nano-scale effect, kerogen, adsorbed oil and so on, and a longer soaking time in a reasonable range leads to a higher exploitation degree of shale oil. In the “injection + soaking” stage, the exploitation degree of heavy hydrocarbons is enhanced by CO2 through its effects of solubility-diffusion and mass-transfer. In the “huff” stage, crude oil in large pores is displaced by CO2 to surrounding larger pores or bedding fractures and finally flows to the production well. The injection of CO2 pre-pad is conducive to keeping the rock brittle and reducing the fracture breakdown pressure, and the CO2 is liable to filter along the bedding surface, thereby creating a more complex fracture. Increasing the volume of CO2 pre-pad can improve the energizing effect, and enhance the replenishment of formation energy. Moreover, the oil recovery is more enhanced by CO2 huff-n-puff with the lower shale matrix permeability, the lower formation pressure, and the larger heavy hydrocarbon content. The field tests demonstrate a good performance with the pressure maintained well after CO2 pre-pad fracturing, the formation energy replenished effectively after CO2 huff-n-puff in a single well, and the well productivity improved.

Pathogenic bacteria's metabolic adaptation for survival and proliferation within hosts is a crucial aspect of bacterial pathogenesis. Here, we demonstrate that citrate, the first intermediate of the tricarboxylic acid (TCA) cycle, plays a key role as a regulator of gene expression in Staphylococcus aureus. We show that citrate activates the transcriptional regulator CcpE and thus modulates the expression of numerous genes involved in key cellular pathways such as central carbon metabolism, iron uptake and the synthesis and export of virulence factors. Citrate can also suppress the transcriptional regulatory activity of ferric uptake regulator. Moreover, we determined that accumulated intracellular citrate, partly through the activation of CcpE, decreases the pathogenic potential of S. aureus in animal infection models. Therefore, citrate plays a pivotal role in coordinating carbon metabolism, iron homeostasis, and bacterial pathogenicity at the transcriptional level in S. aureus, going beyond its established role as a TCA cycle intermediate.

Carbon capture, utilization and storage (CCUS) technology is an important means to effectively reduce carbon emissions from fossil energy combustion and industrial processes. With the crisis of climate change, CCUS has attracted increasing attention in the world. CCUS technology as developed rapidly in China is technically feasible for large-scale application in various industries. The R&D and demonstration of CCUS in China Petroleum & Chemical Corporation (Sinopec) are summarized, including carbon capture, carbon transport, CO2 enhanced energy recovery (including oil, gas, and water, etc.), and comprehensive utilization of CO2. Based on the source-sink matching characteristics in China, two CCUS industrialization scenarios are proposed, namely, CO2-EOR, CO2-driven enhanced oil recovery using centralized carbon sinks in East China and CO2-EWR, CO2-driven enhanced water recovery (EWR) using centralized carbon sources from the coal chemical industry in West China. Finally, a CCUS industrialization path from Sinopec's perspective is suggested, using CO2-EOR as the major means and CO2-EWR, CO2-driven enhanced gas recovery (CO2-EGR) and other utilization methods as important supplementary means.

According to the requirements for large-scale project implementation, a four-scale and three-level CO2 storage potential evaluation method is proposed for saline aquifers in a petroliferous basin in China, considering geological, engineering and economic factors. The four scales include basin scale, depression scale, play scale and trap scale, and the three levels include theoretical storage capacity, engineering storage capacity, and economic storage capacity. The theoretical storage capacity can be divided into four trapping mechanisms, i.e. structural & stratigraphic trapping, residual trapping, solubility trapping and mineral trapping, depending upon the geological parameters, reservoir conditions and fluid properties in the basin. The engineering storage capacity is affected by the injectivity, storage security pressure, well number, and injection time. The economic storage capacity mainly considers the carbon pricing yield, drilling investment, and operation cost, based on the break-even principle. Application of the method for saline aquifer in the Gaoyou sag of the Subei Basin reveals that the structural & stratigraphic trapping occupies the largest proportion of the theoretical storage capacity, followed by the solubility trapping and the residual trapping, and the mineral trapping takes the lowest proportion. The engineering storage capacity and the economic storage capacity are significantly lower than the theoretical storage capacity when considering the constrains of injectivity, security and economy, respectively accounting for 21.0% and 17.6% of the latter.

The two-component regulatory system VraRS regulates transcription of penicillin-binding protein 2 in response to cell wall antimicrobials. Here, Lu et al. show that an enzyme from the wall teichoic acid biosynthetic pathway of MRSA can also modulate the expression of virulence factors such as Staphylococcal protein A via VraRS.

This paper analyzes the differences in geological and development characteristics between continental shale oil in China and marine shale oil in North America, reviews the evaluation methods and technological progress of the continental shale oil development in China, and points out the existing problems and development directions of the continental shale oil development. The research progress of development evaluation technologies such as favorable lithofacies identification, reservoir characterization, mobility evaluation, fracability evaluation, productivity evaluation and geological-mathematical modeling integration are introduced. The efficient exploration and development of continental shale oil in China are faced with many problems, such as weak basic theoretical research, imperfect exploration and development technology system, big gap in engineering technology between China and other countries, and high development cost. Three key research issues must be studied in the future: (1) forming differentiated development technologies of continental shale oil through geological and engineering integrated research; (2) strengthening the application of big data and artificial intelligence to improve the accuracy of development evaluation; (3) tackling enhanced shale oil recovery technology and research effective development method, so as to improve the development effect and benefit.

Abstract Unmanned aerial vehicles (UAVs) are widely used in wireless communication networks due to their rapid deployment and high mobility. However, in practical scenarios, the existence of obstacles and eavesdroppers will seriously interfere with the communication quality of the UAV network and produce a security risk. Thus, this paper combines reconfigurable intelligent surface (RIS) technology with UAVs to build a secure UAV communication network. Normally, a rotary‐wing UAV (labeled as UAV‐S) acting as a base station sends information signals to a legitimate user on the ground with RIS equipment. However, there is a passive eavesdropper on the ground who can steal the information. Therefore, a friendly UAV jammer (labeled as UAV‐J) with a fixed location is introduced to send jamming signals to confuse the eavesdropper. The goal of this paper is to maximize the average secrecy rate of the communication network by jointly optimizing the flight trajectory, transmit power of the UAV‐S and UAV‐J, and phase shifter of the RIS. Since the constructed problem is highly nonconvex, an alternating optimization algorithm based on successive convex approximation techniques is proposed to solve the problem. Simulation results show that the proposed algorithm can achieve a higher secrecy rate in comparison with other schemes.

Factors affecting CO2 flooding of shale oil reservoir were studied by nuclear magnetic resonance (NMR) experiments, the effects of time, pressure, temperature on the recovery of CO2 flooding in shale oil reservoir were analyzed based on nuclear magnetic resonance T2 spectrum, and the effect of fracture development degree on recovery of CO2 flooding in shale oil reservoir was analyzed based on NMR images. In the process of CO2 flooding, the recovery degree of the shale oil reservoir gradually increases with time. With the rise of pressure, the recovery degree of the shale oil reservoir goes up gradually. With the rise of temperature, the recovery degree of shale oil increases first and then decreases gradually. For CO2 flooding in matrix core, the crude oil around the core surface is produced in the initial stage, with recovery degree going up rapidly; with the ongoing of CO2 injection, the CO2 gradually diffuses into the inside of core to produce the oil, and the increase of recovery degree slows down gradually. For CO2 flooding in matrix core with fractures, in the initial stage, the oil in and around the fractures are produced first, and the recovery degree goes up fast; with the extension of CO2 injection time, CO2 diffuses into the inside of the core from the fractures and the core surface to produce the oil inside the core, and the increase of recovery degree gradually slows down. Fractures increase the contact area between injected CO2 and crude oil, and the more the fractures and the greater the evaluation index of fractures, the greater the recovery degree of shale oil will be.

Nanoparticle-assisted microwave heating of heavy oil has the advantages of fast temperature rise and high thermal efficiency. Compared with traditional heating methods, it can reduce viscosity in a shorter time. In addition, the heavy components in the heavy oil are cracked into light components at high temperatures (this high temperature cannot be reached by conventional heating methods). This process is irreversible and avoids the problem of viscosity recovery of heavy oil after the temperature is reduced. Through absorbing microwave heating experiments, study the effect of nanoparticles on the improvement of the ability of heavy oil to absorb waves and raise temperature; through the heavy oil upgrading experiment and the four-component analysis experiment, the effect of adding hydrogen donor to assist microwave on the viscosity reduction of heavy oil upgrading by nanoparticles was studied, and the problem of viscosity recovery was determined; Through the gravity drainage experiment, the mechanism of nanoparticle-assisted microwave to improve the recovery of heavy oil is studied, and the influence of water content, nanocatalyst, and microwave power on the production of drainage is analyzed. The results show that nanoparticles can improve the wave absorption and heating capacity of heavy oil, and adding 0.6 wt% of nanomagnetic iron oxide catalyst can increase the heating rate of heavy oil in microwave by 60.6%; nanoparticle-assisted microwave heating method can effectively upgrade heavy oil and reduce viscosity. The experimental conditions are 2 wt% tetralin mass concentration, 0.5 wt% nano-Fe3O4 particle mass concentration, microwave heating time 50-60 min, and microwave power 539 W. Under this experimental condition, the viscosity is reduced by 40%. This method has viscosity recovery problems, but final viscosity reduction effect is still very significant. Obtaining the mechanism of nanoparticle-assisted microwave to enhance oil recovery, one of which is that nanoparticles improve the wave absorption and heating capacity of heavy oil and increase the heating speed of heavy oil; the second is that the nanoparticles form local high temperature under the action of microwave, which catalyzes the hydrocracking reaction between the heavy components in the heavy oil and the hydrogen donor, upgrading and reducing the viscosity of the heavy oil, and accelerating the production of heavy oil.

Four new sesquiterpene hydroquinones, xishaeleganins A–D (6–9), along with eleven known related ones (12 and 14–23) were isolated from the Xisha marine sponge Dactylospongia elegans (family Thorectida). Their structures were determined by extensive spectroscopic analysis, ECD calculations, and by comparison with the spectral data reported in the literature. Compounds 7, 15, 20, and 21 showed significant antibacterial activity against Staphylococcus aureus, with minimum inhibitory concentration values of 1.5, 2.9, 5.6, and 5.6 µg/mL, which are comparable with those obtained for the positive control vancomycin (MIC: 1.0 µg/mL).

This paper proves the soundness of supercritical CO2 displacement for enhancing gas recovery of a tight gas reservoir via laboratory investigations and compositional modeling. First, a novel phase behavior experimental device with a screened supercritical CO2 dyeing agent were first presented to better understand the mixture characteristics between supercritical CO2 and natural gas. The mass transfer between two vapor phases was also measured. Then, based on experimental results, the compositional model considering the influence of CO2 diffusion on the gas recovery and critical property adjustment of supercritical CO2 was established. The miscibility process and mixing properties, such as density, viscosity, and the flowing velocity vector, of supercriticalCO2 and natural gas were visualized through a 3D display, which obtained a better understanding of the flooding mechanism of Enhanced Gas Recovery (EGR) via supercritical CO2. Finally, with experiments and numerical simulations, the main benefits of CO2 EGR were shown, which were partial miscibility between CO2 and natural gas, pressure maintenance, and CO2 displacement as a “gas cushion.” In general, experiments and numerical simulations demonstrate that CO2 EGR can be seen as a promising way of prolonging the productive life and enhancing recovery of tight gas reservoirs.