Integrity Management of Subsea Pipelines for Water and Gas Transportation in Offshore Gas Storage Facilities

Abstract In the pilot test stage of N gas storage, relying on the construction of D oilfield, the injection production operation was achieved. The D355 subsea water transmission pipeline from the old A artificial island to the B artificial island was converted into a gas transmission pipeline. To ensure the safe and stable operation of the pipeline during the test stage, the feasibility was determined through verification and analysis of the pipeline; High consequence area identification and risk assessment have been carried out on the pipeline, and the risk level is within an acceptable range; Due to the lack of internal testing conditions, a comprehensive inspection and evaluation of the pipeline was conducted, including underwater magnetic memory non-destructive testing, external testing, and pressure testing; In response to the detected problem of exposed pipelines, concrete pads were used for interlocking treatment; In response to the scaling on the inner wall of the pipeline, conservative cleaning measures have been taken, including neutral immersion cleaning and non clogging cleaning with steel wire balls. After thorough argumentation, testing, and treatment, the pipeline has operated well after being put into operation, which is a successful practice for the integrity management of old submarine pipelines. It provides valuable integrity management experience for the gathering and transformation of various offshore oil and gas fields and the construction of offshore gas storage facilities.