The dust-collection system, as the core of a sweeper vehicle, directly inhales dust particles on the pavement. The influence of variable operational conditions on particle-separation performance was investigated using computational fluid dynamics (CFD) Euler–Lagrange multiphase model. The particle-separation performance efficiency and retention time were used to evaluate the dust-collection efficiency. The uniform design (UD) and multiple regression analysis (MRA) methods were employed to predict and optimize the effects of reverse-blowing flow rate, pressure drop, and traveling speed on separation efficiency. The results indicated that the dust-collection performance initially increased and then decreased with increasing reverse-blowing flow rate. As the pressure drop increased, there was an increase in total dust-collection efficiency. However, the efficiency decreased with increasing traveling speed. The regression model showed that the proposed approach was able to predict the particle collection efficiency accurately. In addition, the optimum operational conditions were obtained, namely a reverse-blowing flow rate of 2100 m³/h, a traveling speed of 5 km/h, and a pressure drop of 2400 Pa. The maximum particle-separation efficiency was 99.10%, which showed good agreement with the experimental results.

CO2 flooding for oil recovery is a dynamic process that requires further investigation of oil-gas interface change characteristics, interfacial mass transfer processes, and oil-gas composition variation during both immiscible and miscible displacement. Understanding these factors is crucial for better comprehending their impact on CO2-enhanced oil recovery (EOR). This research used a jointly developed CO2 miscible visual flooding experimental apparatus to study the horizontal dynamic characteristics of CO2 and crude oil under different pressures and flow rates in visual slim tube. At 10 MPa, the stratification results of CO2 and crude oil indicate that the experiment is immiscible flooding. The contact angle (7.9°) between the two phases of CO2 and crude oil at the flow rate of 15 cm/min is larger than that (5.2°) at 1.5 cm/min, and the grey scale of CO2 increases at 100 cm/min. The quantity, individual content, and shape of the light and medium hydrocarbon components condensed on the inner wall of the tube vary with different flow rates. At 15 MPa, the appearance of the CO2 and crude oil transition interval proves that the experiment is miscible flooding. At different flow rates, the inclination angle and distribution of black stripes vary. The whole transition interval is divided into 6 intervals, and the transition interval lengthens with increasing fluid velocity. The experiments visually demonstrate the occurrence of the miscible phase, and identify experimental pressure and fluid flow rate as key factors influencing the miscibility of CO2 and crude oil.

During prolonged well shut-in operations in deepwater drilling, gas dissolved in the wellbore drilling fluid will gradually become saturated and diffuse along the wellbore, posing significant risks to well opening operations. To address this issue, the diffusion law of formation gas in drilling fluid during well shut-in is investigated by combining gas diffusion experiments with gas invasion model calculations. Experimental results show that: (1) The gas-liquid ratio is negatively correlated with invasion depth. Gas invasion is significant near the wellbore wall, where the gas-liquid ratio drops sharply, while it decreases relatively slowly at the center of the wellbore; (2) The gas-liquid ratio is positively correlated with time, and increases gently with time; (3) The gas-liquid ratio is positively correlated with pressure, and varies uniformly with increasing pressure, exhibiting a definite functional relationship; (4) The gas-liquid ratio is positively correlated with temperature, and increases approximately linearly with rising temperature. Based on Fick’s law of diffusion and considering the effects of temperature and pressure, an unsteady-state gas diffusion and migration model during well shut-in is established, which is applicable to different temperature and pressure conditions. By substituting experimental data, specific expressions for the gas temperature diffusion coefficient and pressure diffusion coefficient are obtained. The average error between model predictions and experimental results is within 5%. Applying this model to actual well shut-in conditions yields the distribution law and invasion volume of diffused gas influx at different times, providing certain theoretical guidance and data support for field well shut-in operations.

The physical properties of the reservoir in the Black 59 block of Jilin Oilfield are poor, the porosity is generally low, and the permeability is significantly reduced. The cementing quality of gas injection wells gradually declines under the influence of cement ring corrosion and alternating load impact. By comparing and analyzing the applicability of traditional and new cementing quality evaluation methods in the Black 59 block, a combined scheme suitable for the geological conditions of this block is proposed for optimization treatment. Literature research and on-site data analysis show that acoustic variable density logging has low cost and reliable overall evaluation. Sector cement bond logging has advantages in longitudinal and circumferential resolution, accurately identifying local cementation defects, micro-cracks and corrosion locations in the cement ring. Distributed optical fiber sensing dynamically monitors temperature, strain and pressure changes, and provides real-time early warning for corrosion leakage under alternating loads. For the Black 59 block, a phased collaborative technical solution was proposed. During the initial measurement, acoustic variable density logging was selected for overall evaluation. For the free casing section and suspected problem areas, sector cement bonding logging was deployed for fine diagnosis. During long-term monitoring, distributed optical fiber sensing technology was adopted. When complex anomaly points were detected by sector cement bonding logging or optical fiber, ultrasonic imaging was used as an auxiliary measure. Form a closed loop of dynamic early warning - static diagnosis. This research provides a theoretical paradigm and technical path for wellbore integrity management of similar reservoirs, and has certain engineering value for ensuring the safe and efficient development of unconventional natural gas.