A Proposed Framework for Strengthening Mitigations of Offshore Jacket Structures and its Application

Abstract

The majority of offshore platforms and jacket structures are currently passing their assigned lifetime both on the Norwegian Continental Shelf (NCS), the Gulf of Mexico (GoM), the United Kingdom Continental Shelf (UKCS) and other parts of the world. The concern about ageing related issues and how to solve them is a major concern and presents a significant challenge in all sectors of the offshore oil and gas industry. The reason for mitigation and extending the lifetime of platforms are because there are still plenty of oil reserves left in existing fields. These fields are too small for stand-alone development and the construction of new platforms. Therefore, the use of existing infrastructure is a necessary and efficient solution. In addition, there are several monetary and environmental factors for extending the lifetime of platforms instead of decommissioning them. Mitigation of existing jacket platforms is especially a major concern, because the majority of offshore platforms around the world are jacket-type structures. However, the standards and codes that are available does not provide a detailed guideline for strengthening mitigation of offshore jacket structures. There is not sufficient information about the process and the necessary solutions for extending the lifetime of a jacket structure. In addition, the information is scattered among several codes, guidelines, standards and numerous published articles. To address this issue, a detailed framework is proposed that show a more precise and general guideline for the mitigation of an offshore jacket structure. A literature review is done to assess and collect the available information and present it in a clear overview. The proposed framework is more detailed and provides a list of mitigation techniques on an offshore jacket structure. It provides a better solution by addressing the issues related to the weld, the legs and braces, corrosion damage and structural integrity. At last, the significance of the proposed framework is highlighted through a case study where the proposed mitigation techniques are applied on an existing offshore jacket structure. The results from the case study are discussed and finally conclusions are drawn about the applicability and significance of the proposed framework.