One of the main applications of carbon capture, utilization, and storage (CCUS) technology in the industry is carbon-dioxide-enhanced oil recovery (CO₂-EOR). However, accurately and rapidly assessing their application potential remains a major challenge. In this study, a numerical model of the CO₂-WAG technique was developed using the reservoir numerical simulation software CMG (Version 2021), which is widely used in the field of reservoir engineering. Then, 10,000 different reservoir models were randomly generated using the Monte Carlo method for numerical simulations, with each having different formation physical parameters, fluid parameters, initial conditions, and injection and production parameters. Among them, 70% were used as the training set and 30% as the test set. A comprehensive analysis was conducted using eight different machine learning regression methods to train and evaluate the dataset. After evaluation, the XGBoost algorithm emerged as the top-performing method and was selected as the optimal approach for the prediction and optimization. By integrating the production prediction model with a particle swarm optimizer (PSO), a workflow for optimizing the CO₂-EOR parameters was developed. This process enables the rapid optimization of the CO₂-EOR parameters and the prediction of the production for each period based on cumulative production under different geological conditions. The proposed XGBoost-PSO proxy model accurately, reliably, and efficiently predicts production, thereby making it an important tool for optimizing CO₂-EOR design.

Molecular self-assembly of DNA has been developed as an effective construction strategy for building complex materials. Among them, DNA hydrogels are known for their simple fabrication process and their tunable properties. In this study, we have engineered, built, and characterized a variety of pure DNA hydrogels using DNA tile-based crosslinkers and different sizes of linear DNA spacers, as well as DNA hydrogel/nanomaterial composites using DNA/nanomaterial conjugates with carbon nanotubes and gold nanoparticles as crosslinkers. We demonstrate the ability of this system to self-assemble into three-dimensional percolating networks when carbon nanotubes and gold nanoparticles are incorporated into the DNA hydrogel. These hydrogel composites showed interesting non-linear electrical properties. We also demonstrate the tuning of rheological properties of hydrogel-based composites using different types of crosslinkers and spacers. The viscoelasticity of DNA hydrogels is shown to dramatically increase by the use of a combination of interlocking DNA tiles and DNA/carbon nanotube crosslinkers. Finally, we present measurements and discuss electrically conductive nanomaterials for applications in nanoelectronics.

CCUS-EOR is a crucial technology for reducing carbon emissions and enhancing reservoir recovery. It enables the achievement of dual objectives: improving economic efficiency and protecting the environment. To explore a set of CCUS-EOR reservoir screening criteria suitable for continental reservoirs in China, this study investigated and compared the CCUS-EOR reservoir screening criteria outside and in China, sorted out the main reservoir parameters that affect CO₂ flooding, and optimized the indices and scope of CCUS-EOR reservoir screening criteria in China. The weights of parameters with respect to their influences on CCUS-EOR were determined through principal component analysis. The results show that there are 14 key parameters affecting CO₂ flooding, which can be categorized into four levels. For the first level, the crude oil-CO₂ miscibility index holds the greatest weight of 0.479. It encompasses seven parameters: initial formation pressure, current formation pressure, temperature, depth, C₂–C₁₅ molar content, residual oil saturation, and minimum miscibility pressure. The second level consists of the crude oil mobility index, which has a weight of 0.249. This index includes four parameters: porosity, permeability, density, and viscosity. The third level pertains to the index of reservoir tectonic characteristics, with a weight of 0.141. It comprises two parameters: permeability variation coefficient and average effective thickness. Lastly, the fourth level focuses on the index of reservoir property change, with a weight of 0.131, which solely considers the pressure maintenance level. Based on the CCUS-EOR reservoir screening criteria and index weights established in this study, comprehensive scores for CCUS-EOR were calculated for six blocks in China. Among these, five blocks are deemed suitable for CCUS-EOR. Based on the comprehensive scoring results, a planning for field application of CCUS-EOR is proposed. The study provides a rational method to evaluate the CCUS-EOR reservoir screening and field application in continental reservoirs in China.

CO₂ flooding is widely applied in low-permeability reservoirs due to its good injectivity, miscibility with crude oil, and ability to diminish the interfacial tension and viscosity between oil and gas. However, strongly heterogeneous reservoirs can lead to phenomena such as fingering and gravity override during the displacement process, which significantly reduce the sweep area. To address this, this study systematically investigates the mechanisms influencing CO₂ miscible flooding sweep efficiency under interlayer heterogeneity using a 2D, three-layer, equally thick, heterogeneous visualized physical model. The study compares oil displacement efficiency under three injection-production strategies: sequential activation of high-, medium-, and low-permeability layers, simultaneous activation, and accelerated flooding (1.0 mL/min). High-speed imaging technology is used for real-time monitoring of the CO₂ front migration, revealing the dynamic coupling mechanism of gravity segregation and mass transfer. Experimental results show that at low injection rates (0.1 mL/min), gravity override leads to early gas cap formation at the top of the high-permeability layer, restricting the gas-phase sweep area. In contrast, high injection rates (1.0 mL/min) enhance horizontal displacement forces, suppressing override and increasing the sweep area in the high-permeability layer. Additionally, the migration of CO₂ from the low-permeability layer to the medium-permeability layer intensifies under gravity segregation, and its recovery is strongly influenced by injection rates. The simultaneous activation strategy significantly improves recovery in the medium-permeability layer through synergistic vertical mass transfer and horizontal pressure difference, achieving a total recovery of 85.47%, making it the optimal injection-production strategy. This study provides a theoretical basis for optimizing CO₂ flooding in interlayer heterogeneous reservoirs, emphasizing the critical role of injection-production rates and interlayer coupling effects on sweep efficiency.

This paper summarizes the research progress and applications of oxygen-reduced-air-assisted gravity drainage (OAGD) in enhanced oil recovery (EOR). The fundamental principles and key technologies of OAGD are introduced, along with a review of domestic and international field trials. Factors influencing displacement performance, including low-temperature oxidation reactions, injection rates, and reservoir dip angles, are discussed in detail. The findings reveal that low-temperature oxidation significantly improves the recovery efficiency through the dynamic balance of light hydrocarbon volatilization and fuel deposition, coupled with the synergistic optimization of the reservoir temperature, pressure, and oxygen concentration. Proper control of the injection rate stabilizes the oil–gas interface, expands the swept volume, and delays gas channeling. High-dip reservoirs, benefiting from enhanced gravity segregation, demonstrate superior displacement efficiency. Finally, the paper highlights future directions, including the optimization of injection parameters, deepening studies on reservoir chemical reaction mechanisms, and integrating intelligent gas injection technologies to enhance the effectiveness and economic viability of OAGD in complex reservoirs.

The development strategy of reservoirs containing high pour point oil is affected by temperature greatly, which is different from the common light oil reservoir. In the present study, the sensitivity of a reservoir containing high pour point oil, the fluid properties, the waterflooding rules under different temperature, and the cooling zone in the injection well bottom have been studied. Experiment based laboratory and field data analyses have been conducted. The results shown that the water salinity, pH value and water injection rate affected the waterflooding results. The temperature of the reservoir impacts the efficiency of waterflooding greatly. When the temperature is lower than that of the wax precipitation, the wax precipitation affects the efficiency of waterflooding. The data from water injection well temperature tests have shown that strata cold injury existed concurrently with the water injecting due to the reservoir temperature dropping. Therefore, the injected water temperature should be improved to guarantee the formation temperature higher than the wax precipitation temperature to modify the oil field development results.