Experimental study on the evolution process of hydrate deposition, blockage and decomposition in reducing pipeline

Background In the process of deep-water oil and gas extraction, due to the special structure of the reducing pipeline, the flow field of the pipeline changes here, making it easier for hydrates to form and accumulate at reduced-diameter zone and increasing the risk of pipeline blockage. Methods Aiming at the problem of hydrate deposition and blockage in reducing pipeline, an experimental study was carried out through the self-designed and reduced-diameter transparent flow loop to investigate the hydrate deposition and blockage and decomposition evolution of hydrate at reduced-diameter zone under different conditions of flow velocities and initial cyclopentane volume contents. Significant Findings The study found that the flow field formed at reduced-diameter zone was the main reason affecting the distribution of hydrate particles, and the flow velocity and the initial hydrate volume fraction were the main controlling factors affecting the blockage in reducing pipeline. The flow velocity of 1.6 m/s was determined as the safe boundary for cyclopentane hydrate in reducing pipeline. Based on the experimental results, the mechanism of cyclopentane hydrate deposition and blockage in reducing pipeline was revealed, and targeted prevention and control methods for hydrate blockage at reduced-diameter zone were proposed. It is of great significance to ensure the safe flow of hydrate in reducing pipeline.