Safety Assessment Of Pressure Vessel And Pipeline Defects In SZ Oilfield Platform

The performance against corrosion of SZ platform was detected by MsS Ultrasonic Guided Wave Technique. Several typical pipelines which were selected randomly in these oil field were under the corrosion detection and were divided into different degrees to reflect the corrosion levels of the whole platform.Through the thickness detection, a wall thickness distribution of pipelines in SZ platform was obtained roughly; pipeline defects of SZ platform were found mainly in water pipelines, and reflected a prevalence of internal corrosion; the closed drainage insulations were damaged in 3#platform,6#platform,4# platform of SZ. The amount of H2S, CO2, Fe2+,total iron, soluble gas, bacterial were examed, and a result was showed that the corrosion type was H2S/CO2 synergic corrosion by analyzing the features of the transmission medium, which might attribute to the use of ClO2, and result oxygen corrosion in equipments. The analysis of linear polarization (LPR) revealed a higher corrosion rate in these locations:11# to the terminal of P,115 water well, B to the terminal of P sea water injection pipe, B2 water well, K to the terminal of I and 9# water injection pipe.The Gumbel mode and Weibull mode were applied to analyze the regularities of depth distribution of pipeline corrosion. The results proved that the deepest pitting defects obeyed the Gumbel distribution and Weibull distribution, and the probability of the maximum less than a certain value was calculated according to such regularities.The pipeline corrosion rates with different diameters and flow speeds were predicted according to De.Waard mode. The consequences showed that the smaller the pipe were and the quicker the mixture flowed, the bigger the rates were. A flow field analysis, using FLUENT, showed that the bends were more vulnerable than the straight pipes. Because of pitting defects, the sections which had pits deeper thanl.5mm in crude oil system and water system corrosion were experienced a stress analysis by using ANSYS, one kind of finite element analysis software. According to DNV (Det Norske Veritas) recommended method of calculating the corrosion of pipeline failure probability, two pipelines were selected from crude oil system and water system respectively of SZ I platform and be examed the failure probabilities, and the evaluation showed that the former is safer than the latter.According to analysis data of detection, gas features, coupon sample, the aqueous phase, LPR, and pipeline safety assessment, some suggestions were proposed to make sure the product system perform well:strengthening management of the use of inhibitors(especially hydrogen sulphide inhibitors) in oil processing system of SZ I district; increasing the amount of inhibitor in water system to reduce corrosion of pipeline and equipment; adding corrosion coupon to monitor corrosion development; repairing, or replacing if necessary,6 most serious defects.