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Changing the Hydrate Management Guidelines: From Benchtop Experiments to CSMHyK Field Simulations

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journal contribution
posted on 03.11.2020, 21:03 by Yan Wang, Siva Subramanian, Douglas Estanga, Ahmad A. A. Majid, Sijia Hu, Davi C. Salmin, Carolyn A. Koh, Luis E. Zerpa
High-pressure and low-temperature conditions during subsea pipeline transportation favor the formation of gas hydrates and may create challenging flow assurance problems. Once gas hydrates have plugged the pipeline, it is usually difficult and costly to remediate. To prevent hydrate plugging, rigorous hydrate management guidelines need to be formulated and implemented at an affordable cost. Current hydrate management guidelines are mostly based on fluid analysis and benchtop experimental results, which may not represent the actual field conditions. Based on this situation, a simulation tool that can bridge the gap between benchtop experiments and field pipeline transportation conditions is needed. In this paper, a methodology is proposed to combine benchtop ultralow volume (<10 mL) experiments with field simulations to provide insights for field hydrate management. This methodology was applied to a real black oil field to study the blockage risk during shut-ins of varying durations. Simulations were carried out at three representative water cuts. It is indicated that for production shut-ins within 6 h, the flowlines can be directly restarted without hydrate plugging risk. Hydrate slip and accumulation could increase the plug potential, thus for a restart following a planned shut-in longer than 6 h, AA injection might be necessary. Simulations indicate that even after 16 h into a shut-in, the hydrate formation amount would be very low during dead oil displacement. This suggests that dead oiling could be a good strategy to minimize risk during the ensuing restart for unplanned shut-ins longer than 6 h. Based on these simulation results, the envelope for a hydrate risk management approach can be expanded to allow higher water cut operation with minimal blockage risk during extended unplanned shut-ins and restarts. This simulation tool and the proposed methodology may be used to develop competitive field hydrate management guidelines with relatively low capital expense (CAPEX) and operating expense (OPEX) in different fields.

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