Assessment of Offshore Platforms Under Subsidence—Part II: Analysis and Results

Jha, Alok K.; Kiciman, Ö.K.; Gebara, Joseph M.; Stahl, Bernhard; Dahl-Stamnes, Knut H.

doi:10.1115/1.1313531

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…It is suggested that the component method [45,46] or computational fluid dynamic method [28,[47][48][49] are to be utilized to calculate the wave-in-deck load in order to reduce the conservatism of the silhouette method. The risk of platform damage may be reduced via modification such as localized protection or relocation of exposed sensitive equipment or via procedures such as production shut-in and temporary evacuation during storm season [59,60]. Another method that was successfully performed was by jacking-up the platform in order to increase the air gap of platform [61].…”

Section: Probability Of Failurementioning

confidence: 99%

Structural Integrity of Fixed Offshore Platforms by Incorporating Wave-in-Deck

Azman¹,

Husain²,

Zaki³

et al. 2021

JMSE

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The structural integrity of offshore platforms is affected by degradation issues such as subsidence. Subsidence involves large settlement areas, and it is one of the phenomena that may be experienced by offshore platforms throughout their lives. Compaction of the reservoir is caused by pressure reduction, which results in vertical movement of soils from the reservoir to the mud line. The impact of subsidence on platforms will lead to a gradually reduced wave crest to deck air gap (insufficient air gap) and cause wave-in-deck. The wave-in-deck load can cause significant damage to deck structures, and it may cause the collapse of the entire platform. This study aims to investigate the impact of wave-in-deck load on structure response for fixed offshore structure. The conventional run of pushover analysis only considers the 100-year design crest height for the ultimate collapse. The wave height at collapse is calculated using a limit state equation for the probabilistic model that may give a different result. It is crucial to ensure that the reserve strength ratio (RSR) is not overly estimated, hence giving a false impression of the value. This study is performed to quantify the wave-in-deck load effects based on the revised RSR. As part of the analysis, the Ultimate Strength for Offshore Structures (USFOS) software and wave-in-deck calculation recommended by the International Organization for Standardization (ISO) as practised in the industry is adopted to complete the study. As expected, the new revised RSR with the inclusion of wave-in-deck load is lower and, hence, increases the probability of failure (POF) of the platform. The accuracy and effectiveness of this method will assist the industry, especially operators, for decision making and, more specifically, in outlining the action items as part of their business risk management.

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Section: Probability Of Failurementioning

confidence: 99%

Structural Integrity of Fixed Offshore Platforms by Incorporating Wave-in-Deck

Azman¹,

Husain²,

Zaki³

et al. 2021

JMSE

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“…Pile foundation is widely used in these structures. And piles bear the loads including drag force and lift force under the wave and current and usually are destroyed by wave-current flow [1,2]. Indoor model experiments were made to study the influence of different flow velocities in wave-current flow on loads of a single pile and the change of the key coefficients.…”

Section: Introductionmentioning

confidence: 99%

Experimental Studies on Loads on a Single Pile under the Wave-Current Flow

Zhu

Qiu

Dai³

2012

AMM

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Indoor model experiments were made to study loads on single pile under the wave-current flow. Take three different velocities of the current and three different diameters of piles in the experiments to get the variations of loads. Drag and lift forces were measured by a two-component balance. Analysis on experiment results shows that, both drag force and lift force increase with the increase of the pile diameter and the current velocity. The drag coefficient Cd increases with the increase of Kc number until Kc researches 12, when Kc is more than 12, Cd decreases with the increase of Kc; while the inertia force coefficient Cm decreases with the increase of Kc, when Kc is more than 12, Cmchanges little. And the lift coefficient shows no correlation with the Kc number.

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