Structural Integrity Study for Additional Piles on an Existing Jacket Structure in Western Indian Offshore
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Oil and Natural Gas Corporation (ONGC) operates more than 265 steel jacket-supported platforms installed in water depths ranging from 25 to 90 mts. and secured to the seabed using steel piles. Quite large number of platforms have either exceeded their design lives and/or undergone modifications/mitigation/strengthening due to change in design premises and/or revamping projects executed for enhanced oil recovery. This calls for requalification studies for their extended “fit for use purpose.” This paper describes the structural integrity assessment of an existing platform found to have highly overstressed piles and failing members and joints based on design-level analysis. A pushover analysis has been carried out to assess the reserve strength ratio (RSR) for checking the structural adequacy of the jacket structure, and suitable mitigation measures have been suggested for the particular platform as a combination of additional retrofit members/piles, removal of redundant facilities, and strengthening of members/joints, etc.
KeywordsJacket structure Design in-place analysis Ultimate strength analysis RSR
We acknowledge the support and resources provided by ONGC required for carrying out this study. The study has been immensely beneficial in understanding the pertinent issues relevant to the structural behavior of jacket structures and is of vital importance in purview of ONGC’s operational requirements to carry out life extension studies of existing platforms. We extend our sincere thanks to Shri C. Tandi, ED-HoI, IEOT-ONGC for his generous support and encouragement. We are also immensely grateful for the continuous motivation received from Shri Dinesh Kumar, GGM (Civil)-Head of Structures Section, IEOT-ONGC.
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