Pressure Test Method of Safety Assessment on Existed Submarine Pipeline

Submarine pipeline has become a major transportation pattern of oil and gas, as well known, the petroleum is corrosive and harmful to the steel wall of the pipeline. The existed pipelines should be checked after several years in service, so that the remaining service life time can be estimated and the decision of re-using can be made. Several normal test methods are all expensive; some of them are inconvenient and need to stop the service transportation. So a new convenient method, based on on-spot pressure test, is developed to check the pipeline safety without interrupting the service. In this method, first of all, the corrosion state of the pipeline is estimated on the base of corrosion test. Then mechanical analysis is performed to determine the corresponding test pressure of all corrosion state cases. Then the on-spot pressure test is performed, and the test result is a powerful indication of the safety state of pipeline. An Equivalent Reliability Method (ERM) is used to determine corresponding service pressure, which is believed to be safe for continuing service. This method has been used in a pipeline safety assessment of CNOOC. The result showed that the new attempt is pretty reliable, economic and convenient.