Abstract

Supplying monoethylene glycol (MEG) to the wellhead is critical to gas production since interruption of MEG injection can lead to loss of well production due to the risk of hydrate plug formation in the subsea production infrastructure. Maintaining a high reliability of MEG supply is heavily dependent on good MEG Recovery Unit (MRU) performance.

This paper is applicable to subsea gas-condensate wells using MEG for hydrate inhibition and outlines a holistic approach towards diminishing the impact of contaminants in Rich MEG on MRU operating performance. An overview of the impact of various contaminants on MRU operation and how to deal with them will be discussed. Conceptual design considerations and practical applications as per vendor experience will be presented, as well as, examples of the impact of Rich MEG contaminants on MRU operation.

During the life of the gas reservoir, both short term events (e.g., completions fluid clean up, well start up, flow rate increases) and long term events (e.g., hydrocarbons entrainment, clay, silt, corrosion products, corrosion inhibitors, scale inhibitors, demulsifiers, formation water breakthrough) introduce contaminants into the Rich MEG that need to be considered in terms of impact on operational reliability of the MRU. If the effects of the contaminants result in reducing the reliability of the MRU to less than the desired design target, then they need to be removed or at least reduced in quantity to a level that permits the reliability target to be achieved.

Key groups that need to be involved in conjunction with the Client to ensure successful MRU design are Flow Assurance (wellhead chemistry and pipeline flow), Testing/Simulation facility and/or Vendor facility (study work, bench tests, and/or separation equipment piloting), Hydrocarbons Process Engineering (topsides or onshore processing facilities/MEG Regenerator and MEG Reclaimer design), and the MRU package vendor. Effective communication and collaboration between all parties in the early phases of the project is essential for managing these contaminants and maximizing MRU availability.

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