Enhanced oil recovery (EOR) is a crucial technology in the petroleum industry, influenced by several factors, including flooding fluids and methods. The adjustment of injection strategies and the application of vibration stimulation can significantly impact oil recovery, especially residual oil. In this study, we conducted experiments using a glass micromodel to investigate the effect of pulsing water injection on oil recovery. Our results show that when the pulse frequency matches the natural frequency of the micromodel, resonance occurs during the two-phase flow of pulse driving, which causes an increase in the amplitude of oscillation, enhances the mobility of oil, and improves recovery. The efficiency of the kinetic energy of displacement is also improved. However, when the frequency is 3 Hz, the absence of resonance leads to the opposite effect. In addition, we found that a greater amplitude increases the fluidity of oil. These findings have significant implications for the design of EOR strategies and methods. Our experimental results provide insight into the effect of pulse water injection on oil recovery and offer a potential strategy for the optimization of EOR techniques.

The CO₂-enhanced oil recovery (EOR) technology has the dual significance of enhancing oil recovery and realizing carbon storage in onshore and offshore oil and gas exploitation. This study investigates the adsorption of crude oil components on quartz surfaces and the microscopic mechanisms of CO₂ stripping from crude oil using molecular dynamics simulations. A four-component model representing C₆H₁₄, benzene, resins, and asphaltenes was constructed to simulate the oil phase, while the quartz surface model was created using Materials Studio. Simulations were conducted under different temperature conditions to understand the distribution and adsorption behavior of crude oil components, as well as the impact of CO₂ on the oil film at pressures up to 10 MPa. The results indicate that the resin–asphaltene interactions are significantly weakened at elevated temperatures, affecting the adsorption capacity. Furthermore, CO₂ stripping primarily extracts light components such as C₆H₁₄ and aromatic hydrocarbons, while heavy components remain in the oil phase. The highest extraction efficiency and expansion effect of CO₂ were observed at 35 °C, demonstrating optimal conditions for enhanced oil recovery through CO₂ flooding. These findings provide insights into the effective use of CO₂ for crude oil extraction and its interactions with oil components on a quartz substrate, which is crucial for optimizing CO₂-enhanced oil recovery operations.

Natural gas hydrates (NGHs) are an emerging source of clean energy distributed in the pores of soil sediments in deep seabed and permafrost zones with abundant reserves. Cavitation contains enormous energy, thus allowing radial cavitation jets to improve drilling and production rates of NGHs. This paper presents an experimental apparatus that was developed to synthesize NGHs and generate cavitation bubbles by laser for the analysis of the erosion rules of NGHs by cavitation in a reservoir environment. The apparatus consists of a working fluid injection and pressure control system, a temperature control and circulation system, a laser-induced cavitation system, a visual reaction vessel, and a data acquisition and measurement system. The laser-induced cavitation erosion on NGHs and multi-bubble interaction experiments can be conducted over temperatures and pressures in the range of 0–20 °C and 0–12 MPa, respectively, in a visualized reaction vessel. Hydrophones and high-speed photography were utilized for monitoring and analyzing the erosion process within the visualized reaction vessel. In addition, bubble groups of different components in various environments can also be tested in this apparatus to obtain the interaction characteristics under different conditions. This paper discusses the basic structure and principle of the apparatus and conducts a series of experiments to verify the effect of cavitation erosion on hydrate and the feasibility of using cavitation to increase production in hydrate exploitation.

Depleted oil and gas reservoirs, owing to their large storage capacity and well-established infrastructure, are attractive sites for storing green energy carriers such as natural gas, hydrogen, and compressed air. During injection–production cycling in underground gas storage (UGS), variations in effective stress can cause repeated stress disturbances in the reservoir and surrounding rock, which may trigger borehole sand production. In this study, laboratory sand-production simulation tests were conducted to evaluate the effects of cyclic-loading stage, upper stress limit, and cycling frequency on borehole damage and sand-production behavior. The results show that sand production is stage-dependent. During the rapid-hardening and stable stages, the borehole remains largely intact and sand production is negligible. Once the failure and collapse stages are reached, borehole integrity deteriorates and sand production increases sharply, with fine particles becoming dominant. Cumulative sand production increases with the upper stress limit. Increasing the upper limit from 80% to 95% leads to a 2.53-fold increase in produced sand mass, together with a higher fine-sand fraction and a shift in the particle-size distribution (PSD) toward smaller sizes. The cycling frequency also plays an important role. When the frequency decreases, cumulative sand production increases and becomes 53.1% higher than the baseline at 0.001 Hz. Meanwhile, the median particle size (D50) decreases, indicating stronger particle breakage under low-frequency cycling. These findings provide guidance for designing injection–production schemes for UGS and for selecting appropriate sand-control completion strategies.

Ultra-deep shale in the Mahu Sag, characterized by difficult-to-drill formations, exhibits high resistivity. This study uses XRD and petrophysical testing on 12 dry core samples (depths 4600–5000 m) to characterize mineral composition and evaluate resistivity-influencing factors. Mineralogical analysis reveals that brittle minerals, dominated by quartz and feldspar (>50%), constitute the primary components of the ultra-deep shale in the Mahu Sag, with quartz, feldspar, and carbonates collectively accounting for ~80%. Clay (~6%) and pyrite (<5%) contents are notably low, resulting in elevated resistivities of 10⁵–10⁷ Ω·m. Resistivity correlates negatively with pyrite (r = −0.588) and feldspar (r = −0.319) but positively with dolomite (r = 0.209), quartz (r = 0.017), and porosity (r = 0.749). At elevated temperatures (100 °C), resistivity declines owing to enhanced ionic conduction. These findings clarify high-resistivity mechanisms, supporting resistivity-based drilling parameter optimization.