ABSTRACT

This paper shares a structural integrity management (SIM) approach for a steel gravity-based structure (GBS) which is installed in the Caspian Sea. SIM for the steel GBS was based on the API-RP2SIM, 2014 methodology of Data-Evaluation-Strategy-Program processes. A Major Accidental Hazard (MAH) study identified that a total of seven (7) major structural hazards and two (2) non-structural hazards are considered for the SIM approach to the GBS. A Qualitative risk assessment (QRA) approach was used to establish the risk for each identified hazards and the risk-based underwater inspection (RBUI) and maintenance strategy was established with the associated inspection, testing and planned maintenance program.

The platform risk was identified through the QRA which identified the global collapse due to extreme storm as the highest risk. To demonstrate the acceptance risk level, an extreme storm regional hazard curve was established. A semi-quantitative methodology was used to determine the platform probability of failure. The company's risk matrix was used via the Hazards and Effects Management Process (HEMP) and the inspection frequency as per the recommended practices of API-RP2SIM, 2014. With more inspection data in the future and an ultimate strength assessment of the structure to support the SIM approach, a less conservative risk assessment is possible, to further optimize the inspection scope of work.

INTRODUCTION

Since 1974, more than 12,000 offshore platforms have been constructed and installed worldwide. The number is growing fast with energy industry transitioning to green energy where offshore wind farm structures is adding to the fleet. Majority of offshore oil and gas production platforms are made up of fixed steel jacket structures due to reliability, constructability, and life cycle economic. Other types of structures such as compliant towers, gravity-based structure (GBS), tension-leg platform (TLP) and other floating structures are also installed to support exploration and production of oil and gas offshore. Besides fixed steel jacket and light weight structures, GBS is among the more common shallow water facilities.

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