Effect of ‘Artificial Islands’ on Structural Integrity Management of Existing Offshore Platforms- Case Study

摘要

Four 'artificial islands' are being constructed in Giant Offshore Field in Abu Dhabi, for the purpose of using as centers for drilling and oil production. ZADCO carried out extensive studies to assess the effect of these 'artificial islands' on the existing field facilities, such as offshore jacket platforms and pipelines, as these 'islands' would permanently alter the estuaries / topographies of the offshore fields. Studies clearly established that these 'alteration' does influence the long term / short term hydrodynamic forces on the existing offshore facilities thus affecting ZADCO's structural integrity management plan. Therefore, it was important to quantify the extent of these changes on the existing jacket platforms such that appropriate modification to the current plan can be implemented. The present case study attempts to address the above issue by analyzing two representative jacket platforms, out of numerous platforms. SACS structural analysis software has been utilized for the analysis of these two platforms using hydrodynamic models developed for the two cases: (1) before the construction of artificial islands and (2) after the construction of 'artificial islands'. Inplace, Fatigue and Pushover cases are part of major parameters used for the structural integrity of the offshore jacket platforms and the results of these analyses are part of critical input to the structural integrity management plans. It was observed that there were significant changes to the result of these analyses due to the introduction of artificial islands especially for the platforms which are having marginal reserve strength. This, in effect, alters current plan of inspection for critical nodes and members which need to be regularly inspected / monitored. It is also observed that the platforms pile on the mudline need to be inspected more frequently to know whether there are any changes to scouring of piles in soil. As a result of this case study it was established that such studies need to be performed while planning 'artificial islands' like facilities in offshore field like areas in order to asses its effect on existing facilities.