Risk-based Inspection And Evaluation Of Static Equipment For Offshore Oil And Gas Production Platforms

Risk-based inspection(RBI)technique has been being researched and applied for 30 years,and the complete system of this technology has been established.At present,RBI has been widely promoted in China.But,because of the differences of contries and industries,The RBI technique has came across some problems in the process of application in our country.So,researching the applicability of RBI technology on offshore oil and gas platform equipments in China and verifing the reliability of the assessment technology is very significant.The main damage mechanisms have been analysed according to the characteristics of domestic offshore oil and gas production platform static equipments.The method of Level 1 consequences analysis for calculating area has been improved,combined with the characteristics of the offshore oil and gas production platform layer.The new risk matrix was built combined the API581-2008 risk matrix with CNOOC equipment integrity risk management program risk requirements,which could improve the applicability of RBI technology.According to the trend of risk in API 581-2008,the strategies and content of inspection which used on the offshore oil and gas production platform stated equipments has been illuminated with some guides of inspection about pressure vessels and pipeline.In order to improve the efficiency of risk assessment,and save the cost of evaluation,the project that the RBI assessment system would be established by database software was put forward.It is a feasible way to establish database.The Microsoft Access was chosed to accomplish this idea,and many static equipments on a offshore platform in Bohai were used to test the practicability of the system.The areas calculated by Level 1 and Level 2 analysis method have been contrasted.The results are showed as follows:The main damage mechanisms of static equipments on offshore oil and gas production platforms are thinning(CO2 corrosion,H2S corrosion,bacterium corrosion,erosion),stress corrosion cracking(SSCC,HIC,CSCC,ClSCC),external damage(atmospheric corrosion,under CUI corrosion,external ClSCC,under CUI ClSCC),component linings,and piping mechanical fatigue.The efficiency of risk assessment could be improved by the RBI assessment system,and the cost could be saved.The risk matrix of API 581-2008 and the new risk matrix combined API 581-2008 and CNOOC equipment integrity risk management program were both used to analyse the example.The results of the example analysis show that the categories of PoF evaluated by new risk matrix are higher than API 581-2008 about a level.This will affect some equipments which'srisk are closer to the higher level of risk,but it also conforms to the characteristics of offshore equipments that probability of failure is high.The results of the example analysis show that the period of inspection is more than 1 year calculated by RBI.The levels of failure consequences of high-risk items which analysed by Level 1 analysis method and Level 2 analysis method are almost the same,Level 2 analysis method should be used in the equipmemts,when the results evaluated by the RBI assessment system are inconsistent with the actual risk or the effect of RBI assessment system is not suitable.Based on the standard of CNOOC equipment integrity risk management program for dividing the failure consequences,it can be effectively avoided that the division standard is not unified cause by the different size of offshore oil and gas production platform area.