Management of Mercury Offshore for Onshore Production Facilities

Abstract

The objective of this paper is to provide an approach in mitigating the adverse effects of mercury found in production fields which include the evaluation on the requirement for mercury treatment facility and suitable technology and best location for the production fields and onshore LNG facilities. The evaluation included assessment of pipeline integrity and managing unexpected increase in mercury content to ensure Mercury Removal Unit (MRU) is capable to treat the gas within the design specification The method includes mercury mapping and analysis of the results. Evaluation of technology and type at various streams in gas, condensate and water streams. There is no method to predict mercury production forecast and sizing cannot be based on one exploration well data only. Subsurface data might not be representative due to improper procedure, sampling, preservation and timing. Rigorous technology evaluation was evaluated for various mercury species covering its vulnerability to operations abnormalities such as entrainment of moisture, spikes of mercury content, changes to feed gas, hydrogen sulfide content, historical experience of mercury contamination and its impact to operations and performance of cryogenic systems and chemical injection for pipelines. Review of effectiveness of mercury removal technology for gas stream cover metal sulfide based adsorbent and metal oxide based with H2S in-situ sulfiding. In view that there is no proven technology for condensates stream, particulates mercury removal using filtration and hydrocyclones of the multiphase condensate /water and water streams were considered Mercury has exceeded downstream design specification and pose threats to existing LNG facilities aluminum cryogenic heat exchanger. Speciation, particle size distribution and the use of a practical size test rig on site, adsorbent -condensate compatibility test are approaches to determine the capacity of the MRU. Based on the selected technology, concepts were derived for gas and condensate to ascertain the feasibility of mercury removal, particulate filtration, mercury impact to pipeline integrity and the basis for the onshore mercury removal facility. This yielded seven (7) different concepts or options addressing both MRU gas and condensate either at offshore platform or onshore facilities. The concept select ascertained the optimum requirement to install the mercury removal unit onshore upstream of an Acid Gas Removal Unit in the LNG facilities. A two-stage filtration to remove mercury particulates above 1 micron was selected for offshore facility. Understanding the behaviour of mercury and the distribution tendencies into the various streams and factors that influence this distribution would provide insight on the integrity of production and pipeline system and management of mercury for operations.