Study on the removal efficiency of hydrate blockage by injection ethylene glycol in vertical pipeline

Hydrate blockages threaten the safe transportation of deep-sea pipelines. Limited by flow loop scale, generating sufficient hydrate blockages for removal studies in lab is challenging. This study proposed a novel method to prepare solid hydrate blockages by separating hydrate crystals from residual gas–liquid mixtures via high-pressure filtration. The effects of ethylene glycol (EG) concentration, temperature, volume, and soak time on hydrate decomposition were systematically examined. Results show that increasing EG concentration from 5 wt% to 50 wt% enhances decomposition by 415 %, though EG efficiency declines at higher concentrations. Raising the temperature from 30 °C to 80 °C increases gas decomposition by 182 %, with peak thermal efficiency at 50 °C. Increasing injection volume from 50  mL to 170  mL boosts dissociation by 406 %. Injecting EG solution causes the decomposition of hydrate plugs, resulting in the increase of pressure in the pipeline, with a maximum increase of 1.31 MPa. Soak time correlates positively with EG concentration, but longer soak time reduce the average decomposition rate. These dissociation characteristics are crucial for the flow assurance of oil and natural gas.