Combatting Mercury Threat in Sustaining Asset Integrity for Offshore Production Facilities

Abstract Mercury production from reservoir is exceedingly challenging to predict, especially at the development stage of the project with limited data. Therefore, it poses operational challenges during production and may possess integrity risk to the assets and downstream buyer. This paper offers a comprehensive evaluation of product quality, integrity, and economic assessment for an offshore facility in managing elemental and solid mercury, which could impact the downstream system. A comprehensive approach was undertaken, encompassing the analysis of historical production data, including mercury data, sampling and analysis, mercury partitioning simulation, pipeline partitioning simulation, integrity assessment, particles analysis, solid computational fluid dynamic (CFD) modelling, impact on product quality, and mercury technology screening. Historical and sampling data, along with future forecasts, were analyzed to develop scenario for the production facilities. Based on this, the elemental mercury partitioning and drop out was simulated throughout the facilities and the pipeline, comparing with the actual production data. The result was used for elemental and solid mercury integrity assessment for the facilities. Study indicates there are no clear correlation between the gas and mercury production. For elemental mercury, partitioning study indicated that elemental mercury would partition into the gas phase and some of the elemental mercury would be partitioned into the liquid when there are changes in operating pressure and temperature in the processing and transport system in the offshore facilities. During transport of fluid in the pipeline, most of the elemental mercury would partition into the gas phase. The mercury is still within the downstream mercury removal unit and sales agreement specification. The particulates mercury will mostly be at the liquid side where a solid mercury removal unit (MRU) had been installed. However, sampling result indicated smaller particles had been produced from the reservoir compared to the design stage. Computational Fluid Dynamic (CFD) study was conducted to evaluate the behavior of the particles. Based on study finding, there is no evidence to suggest that there is a threat to the integrity of offshore facilities or cross contamination possibility to gas phase. As a result, there are no requirement to remove the smaller particulates as it does not pose erosion risk. In addition, there is limited technology available in the industry for removal of sub-micron particles. This paper provides a holistic and systematic approach on evaluating the impact of changes on mercury production to the existing gas production facilities. Understanding of the integrity and product quality threat would direct the operation's management in making the right decision on the technology investment.