Previous studies showed the difficulty during polymer flooding and the low producing degree for the low permeability layer. To solve the problem, Daqing, the first oil company, puts forward the polymer-separate-layer-injection-technology which separates mass and pressure in a single pipe. This technology mainly increases the control range of injection pressure of fluid by using the annular de-pressure tool, and reasonably distributes the molecular weight of the polymer injected into the thin and poor layers through the shearing of the different-medium-injection-tools. This occurs, in order to take advantage of the shearing thinning property of polymer solution and avoid the energy loss caused by the turbulent flow of polymer solution due to excessive injection rate in different injection tools. Combining rheological property of polymer and local perturbation theory, a rheological model of polymer solution in different-medium-injection-tools is derived and the maximum injection velocity is determined. The ranges of polymer viscosity in different injection tools are mainly determined by the structures of the different injection tools. However, the value of polymer viscosity is mainly determined by the concentration of polymer solution. So, the relation between the molecular weight of polymer and the permeability of layers should be firstly determined, and then the structural parameter combination of the different-medium-injection-tool should be optimized. The results of the study are important for regulating polymer injection parameters in the oilfield which enhances the oil recovery with reduced the cost.

Micro/nanoparticles have emerged as pivotal agents in enhancing oil recovery (EOR), offering novel approaches to optimize the extraction processes in complex reservoirs. This review comprehensively examines the utilization of these particles, focusing on their unique material and structural characteristics that facilitate significant modifications in flow dynamics within porous media. These particles effectively reduce interfacial tension, modify wettability, and improve sweep efficiency, thereby enhancing oil recovery efficacy. Through a synthesis of current research spanning field-scale experiments, core flood studies, and micro-model investigations, this paper highlights the integration of micro/nanoparticles in practical EOR applications. Despite their proven potential, challenges such as scalability, environmental concerns, and economic feasibility persist, requiring ongoing advancements in particle engineering and simulation technologies. This review aims to provide a thorough understanding of the current landscape and future prospects of micro/nanoparticles in EOR, underlining the need for innovation and interdisciplinary collaboration to overcome existing hurdles and fully exploit these technologies in the oil and gas industry.

In order to improve the oil displacement effect of alkali/surfactant/polymer (ASP) solution in low-permeability oil layers, Daqing Oilfield has proposed a separate injection technology. The objective of separate injection technology is to reduce the viscosity of ASP solution through a different medium injection tool and increase the injection amount of ASP solution in low permeability oil layer, thus improving the oil displacement effect. In order to study the effect of the different medium injection tool on ASP solution, SEM is used to observe the changes in molecular micromorphology before and after the ASP solution flows through the tool. Then, the influence of the tool on viscosity and the first normal stress difference of the solution are studied through static shear experiments. Finally, the storage and loss modulus of the solution are measured through dynamic mechanical experiments and the relaxation time and zero shear viscosity of the solution are verified and compared. The results show that molecular chains are obviously broken and the grid structure is destroyed after the ASP solution is acted on by the different medium injection tool. The viscosity and elasticity of ASP solution decrease, and the influence degree of the different medium injection tool on viscosity is greater than elasticity. The results of the steady shear experiment and dynamic mechanics experiment are consistent. Therefore, the different medium injection tool can achieve the purpose of use, which is conducive to the injection of displacement fluid into low-permeability oil layers and enhance the recovery ratio.

Hydrogels typically deteriorate under high-salinity conditions because electrostatic screening and reduced polymer-solvent affinity suppress swelling and weaken load-bearing network connectivity. Here, we report a double-network hydrogel that strengthens while swelling in brine. Compared with its behavior in water, the network undergoes an ion-triggered topological reconfiguration upon salt exposure. The intrachain zwitterionic ion pairs open and reform as inter-network SBVI⁺-AMPS^- bridges, increasing effective bridge density at lower polymer fraction. The hydrogel exhibits 1.63-fold tensile strength and 1.21-fold swelling ratio in 200 g/L NaCl compared to deionized water. SAXS and XPS confirm salt-induced structural homogenization and charge redistribution. Density functional theory calculations support strengthened ionic association under saline conditions between SBVI and AMPS. Free energy analysis reveals that reduced loop fraction and increased connectivity enable associative stabilization to compensate for elastic swelling penalties. Core-flooding demonstrates robust injectability in high-salinity porous rock. This mechanism provides design rules for salt-adaptive hydrogels.

Electrical borehole imaging tools cannot achieve full-borehole images due to their structure limitation. Gaps always occur between pads, and it is necessary to fill in the gaps for subsequent interpretation. In this paper, an improved model for borehole image restoration and enhancement is established by combining a “Deep-Fill” image repair algorithm based on generative adversarial networks (GANs) with histogram equalization principles. Firstly, resistivity data is converted into images, and the anomalous areas are manually repaired. Then, the manually repaired images undergo iterative training using the “Deep-Fill” model. Finally, the repaired images are further enhanced through histogram equalization principles. Results show the overall restoration quality of the model surpasses that of the original GAN-based restoration model, particularly in terms of texture coherence at junctions. This approach not only enhances the quality of repaired images but also improves the interpretability of geological features of the electrical imaging logs.

Pipelines extend thousands of kilometers to transport and distribute oil and gas. Given the challenges often faced with corrosion, fatigue, and other issues in steel pipes, the demand for glass fiber-reinforced plastic (GFRP) pipes is increasing in oil and gas gathering and transmission systems. However, the medium that is transported through these pipelines contains multiple acid gases such as CO₂ and H₂S, as well as ions including Cl⁻, Ca²⁺, Mg²⁺, SO₄²⁻, CO₃²⁻, and HCO₃⁻. These substances can cause a series of problems, such as aging, debonding, delamination, and fracture. In this study, a series of aging damage experiments were conducted on V-shaped defect GFRP pipes with depths of 2 mm and 5 mm. The aging and failure of GFRP were studied under the combined effects of external force and acidic solution using acoustic emission (AE) techniques. It was found that the acidic aging solution promoted matrix damage, fiber/matrix desorption, and delamination damage in GFRP pipes over a short period. However, the overall aging effect was relatively weak. Based on the experimental data, the SSA-LSSVM algorithm was proposed and applied to the damage pattern recognition of GFRP. An average recognition rate of up to 90% was achieved, indicating that this method is highly suitable for analyzing AE signals related to GFRP damage.