THE USE OF INSPECTION RESULTS FOR THE EVALUATION OF BATCH rREATMENT EFFICIENCY AND THE REMAINING LIFE OF THE PIPELINES SUBJECTED TO TOP OF LINE CORROSION

摘要

Bongkot is an offshore gas filed in the Gulf of Thailand in operation since 1992. The average CO_2 content of the gas is 23%. Recently the decision was taken to produce gas from reservoirs containing higher percentage of CO_2. Evaluations of the new corrosivity and the efficiency of chemical treatment are needed to estimate the remaining service life of the sealines which have been subjected to top of line corrosion (TLC) since the production start-up. After detection of the first TLC case in this field in 1996, different possibilities were investigated to reduce the corrosion rate to a reasonable value. Batch treatment started in 2000 using double pig and then Top of Line Corrosion Control Pig (TLCC-PIG) has been used since 2004. The weak point of the TLC control is the unavailability of a reliable monitoring system. The development of condensing probe for TLC monitoring is completed but the field testing is not yet performed. However, some of the sealines have been inspected but intelligent pigging two or three times. The decision is taken to use intelligent pigging results for this study. The paper describes the field conditions, summarizes the inspection results, and explains the methodology used for the evaluation of the corrosivity and batch treatment efficiency; the objective being the evaluation of the remaining life of the sealines.