Determination of hydrate inhibitor injection rate based on the life-cycle cost of the injection facility and mitigating measures

This study presents a framework for hydrate formation risk management. Hydrate formation accidents and the consequences of hydrate formation risk are defined by the initiation of hydrate formation and pipeline blockage due to hydrate formation, respectively. The hazards, preventive measures and mitigating measures for hydrate formation are presented in accordance with defined accidents and consequences. A life-cycle cost (LCC)-based hydrate formation risk management methodology is proposed that consists of four steps: construction of an exceedance curve for the durations of operational interruptions, construction of an exceedance curve for the frequency versus the monoethylene glycol (MEG) injection rate, selection of the MEG injection rate, and LCC estimation. Operational interruptions are quantified in terms of the frequency of hazard occurrence and their extent via exceedance curves for the durations of the operational interruptions. The next step of constructing the exceedance curve for the frequency of hydrate formation with respect to the MEG injection rate quantifies the frequency of the accidents for a given MEG injection rate. Because the failure rate and the repair time of equipment are discrete, only a set of representative MEG injection rates deserve further consideration in the LCC estimation. Two case studies are performed with topsides that have different process complexities, which lead to different frequencies of operational interruption.