Reliability Analysis of Opukushi Seibou Oil Field Flowline Against Corrosion Failure

The aim of this paper was to examine the effect of corrosion on Opukushi Seibou Oil field flowline and also evaluate the reliability of the flowline. The corrosion failure is as a result of absence of corrosion inhibitor in Well 24T 6 inches flowline pipe. The first order reliability method analysis using Weibull distribution model was developed in python computer program, to analyze data of the corroded pipe. Piping dimensions from the field were obtained in imperial units for this research computer program and final results in SI units. Thickness of pipe t2 is 7.11mm, the depth of corrosion d is 5.588mm, longitudinal length L of corrosion is 305.05mm and operating pressure of the flowline Po is 8.49Mpa. Standard ASME code that relates extent of corrosion to the burst pressure of a corroded pipe was used to carry out a Monte Carlo Simulation for the burst pressure Assumptions were made for corrosion longitudinal length and depth to take up the shape of a normal exponential distribution. The random value generated simulated random event that could happen at any point in the pipe. Two thousand (2000) samples were iterated using the python program to obtain results. For each sample generated the values of d and L were substituted into the equation for burst pressure as per ASME B31. The Two thousand (2000) equivalent samples for the burst pressure resolved from the Monte Carlos random sample for d and L were plotted. The shape of the distribution is in form of a Weibull distribution, which was used to calculate the probability that the pipe burst pressure is greater than the operating pressure of the pipe (Pb > 8.49􀀅􀀆􀀇). The resulting probability of 68% from a Weibull distribution of scale factor was equal to 0.0556MPA and shape parameter of 1.849(no unit), showed that the pipe was not reliable, indicating that at the present condition of the pipe it will not survive 10 more years without getting damaged.