The produced gas from Sleipner West field area contains up to 9.5 % carbon dioxide 1, 2 and is almost free of hydrogen sulfide. Gas handling facilities on the platform were designed to reduce the level of CO2 to the export criteria of 2.5%. During the start up phase of production and the three years of operation period that followed, the required level of carbon dioxide removal of 2.5% was not achieved, and in most cases the CO2 level in the gas export was averaging 3.5% or higher. Although the slightly higher level of CO2 in the gas export did not cause any major problem, since the export stream from Sleipner West production is mixed up with relatively carbon dioxide free gas (less than 1.0%) from the main Sleipner East production area, it was important to provide complete flexibility in the Sleipner West gas treatment facilities to meet the export criteria of 2.5% CO2.

Poor performance of the amine absorbers in removing the CO2 in the gas phase was thought to be related to the condensate build up in the amine solution. Significant foam build up in the amine absorbers was a good indication of condensate build up caused by carry over and / or condensate retrograded in the pipe work between the different vessels.

Organic, aqueous and gas based radioactive tracers were used extensively in the gas processing facilities and the carbon dioxide removal gas sweetening plant on Sleipner West treatment production platform (SLT) in the North Sea. The use of radioactive tracer techniques within the platform facilities provided semi quantitative data on the level of the liquid carry over from the condensate stabilization process train to the gas plant over a period of three years. In addition, by utilizing the technique in the amine absorbers within the carbon dioxide removal plant, a clearer picture of the flow regime within the tower emerged and was developed. Using the data generated from these studies, as well as plant and system performance data, a full assessment of the poor CO2 removal efficiency was carried out in order to identify the potential problem and determine the required and necessary modifications to the treatment facilities on SLT.

A combination of plant offshore studies, process simulation, laboratory analysis and radioactive tracer studies were utilized to identify and rectify the problem. The data generated from the latter studies were considered an important part in developing an understanding of the problem in the process system on Sleipner West treatment plant. This paper addresses the approach used in utilizing the radioactive tracer techniques in providing a tool for determining carry over and flow regime within the process vessels.

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