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NORM Contaminants at Off-Shore Drilling Platforms
Posted on November 15th, 2016

Petroleum production through drilling operations can release and concentrate naturally occurring radioactive material (NORM) as these elements are present along with the oil and gas that is recovered.  Most of the NORM identified in oil and gas streams belong to the decay chains of naturally occurring uranium 238 and thorium 232.  Among these elements, the decay product isotopes of radium 226 and 228 are prevalent in NORM, due to their solubility in water.  Most drilling operations inject pressurized water to extract petroleum products from a reservoir, which releases radium from the reservoir rock into the production water. During the production process, drops in pressure and temperature will cause its precipitation as sulphate and carbonate scale. Concentration of NORM in scale and sludge is a feature of the composition of reservoir fluids and associated physical and chemical conditions resulting from the production of oil and gas.  The EPA reports that this scale has an average radium concentration of 480 pCi/g, while sludge has an average concentration of 75 pCi/g. It is estimated that annual petroleum production in the US results in 25,000 tons of NORM contaminated scale, and 225,000 tons of NORM contaminated sludge. An individual well produces an average of 100 tons of scale annually.

The deposition of scale can be exacerbated by high salinity of the production water. In addition, deeper drilling operations expose production water to longer columns of rock resulting in higher concentrations of radium in the water.  Both conditions exist at ocean-based platforms referred to as floating production, storage and offloading (FPSO) platforms, increasing the radiological hazards due to NORM.

RSCS has recently been engaged to support the radiation protection program for off-shore oil operations near Angola by performing baseline surveys on four FPSO platforms.  These surveys will be conducted in accordance with the requirements listed in the Presidential Decree 12/12 of January 25, 2012 and with the recommendations of Report n°412 of the International Association of Oil and Gas Producers “Radiation Guidelines for the management of Naturally Occurring Radioactive Material (NORM) in the Oil & Gas Industry” and IAEA Safety Report Series n°34 “Radiation protection and the management of radioactive waste in the oil and gas industry”. 

Measurements with portable γ ray scintillators and a gamma dose rate meters will provide the ambient background dose equivalent rate H*(10) in nSv/h or µSv/h. Surveys will focus on pipes and fixtures involved in water separation operations, heater treaters, and gas dehydrators, as these are areas where NORM contaminated scales typically deposit.  In addition, the surveys will determine if NORM exists in sludge collected in water storage tanks. RSCS will provide detailed survey reports on the NORM contaminants detected, and will conduct radworker training to the employees of the FPSO to reinforce radiation safety and contamination control principles. 

This work scope is unique in that it requires our staff to be certified for Basic Safety Training (BST) and Helicopter Underwater Egress Training (HUET) required for off-shore workers.  In addition, this work required our staff to be bi-lingual in both French and English, with knowledge of international regulations pertaining to NORM and radioactive material management.  Our Health Physicist Jean Geslin is undertaking this work which should be completed by the end of November 2016. 

 

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