Application of RPD on Spudcan Sliding During Jack-Up Installation Near the Footprints
- Chang Gao (Offshore Engineering Technology Center of China Classification Society) | Hongtao Li (Offshore Engineering Technology Center of China Classification Society) | Song Liu (Offshore Engineering Technology Center of China Classification Society)
- Document ID
- International Society of Offshore and Polar Engineers
- The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society of Offshore and Polar Engineers
- critical RPD, spudcan sliding, jack-up platform, installation near the footprints
- 1 in the last 30 days
- 18 since 2007
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Before well repairing operation, it is often necessary to install the jackup very close to the existing spudcan pits, which called footprints. The spudcan is prone to slide towards the footprint in this process, which can lead to damage of legs, jacking system and the hull structure. RPD (Rack Phase Difference) system can monitor the rack vertical phase difference of adjacent chord of truss type leg. In this paper, the RPD calculation principle is studied and an available analysis method of critical RPD applicable to spudcan sliding condition is obtained. The method can provide useful guidance to the designers and operators.
Jack-up drilling unit is the platform whose main hull can be elevated along the leg to the certain height above the sea for drilling operation. The Jack-up has been widely used in offshore oil and gas exploration. With the development of deep-sea oil and gas exploration, the working depth of the jack-up unit is constantly increasing and the structural safety has been paid more attention (Chen Hong, 2008). Before well repairing operation, the jack-up is usually installed near the fixed structure or wellhead. The seabed depressions which remain when a jack-up is removed from a location are referred to as ‘footprints’. The difference in resistance between the original soil and the disturbed soil in the footprint area or the slope at the footprint perimeter, may cause the spudcans to slide towards the footprint. The resulting leg displacements could cause severe damage to the structure and, at worst, could lead to catastrophic failure (SNAME, 2007). The schematic drawing is shown in Fig.1. In May 2012, “Shengli 3” Jack-up skidded during the preloading operation in Yellow Sea and the platform structure was seriously damaged. Then the platform capsized, so as to cause serious operational accidents. In May 2009, in the course of preloading operation for ”HYSY941” in the South China Sea, the bow leg sliding leads bow inclination of 6.2 degrees and large deformation of 4 diagonal braces and two internal horizontal braces. Therefore, before the jack-up preloads near the footprints, more detailed analysis must be executed and response measures should be prepared to avoid the structural injury by spudcan sliding.
|File Size||2 MB||Number of Pages||6|