Research and Experimentation on Pneumatic Particle Transport in Confined Spaces of Offshore Oil and Gas Wells Based on DEM-CFD Coupling Method

To optimize the corrosion mitigation process in the annular space of oil and gas well pipelines, this study introduces a secondary acceleration pneumatic conveying device for particles within the confined spaces of offshore oil and gas wells. This approach addresses the limitations of traditional offshore hydraulic transportation, which can lead to corrosion failure of drug particles. The study investigates the motion mechanisms of drug particles within the pipeline and identifies the critical structural parameters that influence the smooth transport of these particles. A DEM-CFD coupled simulation methodology was employed to conduct single-factor experiments on the minimum air pressure and particle injection quantity required for stable transportation. The results demonstrate that at an air pressure of 0.25 MPa, no particle retention or accumulation occurs within the pipeline, thereby satisfying the engineering requirements. A Box–Behnken three-factor, three-level experimental design was used to perform response surface analysis on the pneumatic device. The findings reveal that the particle outlet velocity initially increases and then decreases with the air injection angle, while the outlet velocity progressively increases with the diameter of the conveying hole and the number of small holes. The maximum outlet velocity achieved is 8 m/s, with the optimal structural parameters identified as an air injection hole diameter of 2.96 mm, an air injection angle of 47°, and 24 small holes. The simulation model was calibrated and validated through fluidized bed experiments, and the simulation optimization was further confirmed via bench-scale particle transportation tests. This research provides a theoretical framework and engineering guidance for optimizing pneumatic particle transport in the confined spaces of offshore oil and gas wells.