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Mathieu Stability of Offshore Buoyant Leg Storage and Regasification Platform

Authors: S. Chandrasekaran, P. A. Kiran

Abstract:

Increasing demand for large-sized Floating, Storage and Regasification Units (FSRUs) for oil and gas industries led to the development of novel geometric form of Buoyant Leg Storage and Regasification Platform (BLSRP). BLSRP consists of a circular deck supported by six buoyant legs placed symmetrically with respect to wave direction. Circular deck is connected to buoyant legs using hinged joints, which restrain transfer of rotational response from the legs to deck and vice-versa. Buoyant legs are connected to seabed using taut moored system with high initial pretension, enabling rigid body motion in vertical plane. Encountered environmental loads induce dynamic tether tension variations, which in turn affect stability of the platform. The present study investigates Mathieu stability of BLSRP under the postulated tether pullout cases by inducing additional tension in the tethers. From the numerical studies carried out, it is seen that postulated tether pullout on any one of the buoyant legs does not result in Mathieu type instability even under excessive tether tension. This is due to the presence of hinged joints, which are capable of dissipating the unbalanced loads to other legs. However, under tether pullout of consecutive buoyant legs, Mathieu-type instability is observed.

Keywords: Offshore platforms, stability, postulated failure, dynamic tether tension.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1132078

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References:


[1] Chandrasekaran.S and R. S. Lognath (2015). Dynamic Analyses of Buoyant Leg Storage Regasification Platform (BLSRP) Under Regular Waves: Experimental Investigations, Ships and Offshore structures, Taylor & Francis.DOI:10.1080/17445302.2015.1131006.
[2] Chandrasekaran, S., Lognath, RS. 2017. Dynamic analyses of Buoyant leg Storage and Regasification platforms: Numerical studies, J. Marine Systems and Ocean Tech., 12(2):39-48.
[3] Graham R. Perrett and Robert M. Webb (1980). Tethered Buoyant Platform production system, 12th Annual Offshore Technology Conference, OTC 3881, Houston, Texas, 5-8th May, pp. 261-274.
[4] Robert W. Copple and Cuneyt C. Capanoglu (1995). A Buoyant Leg Structure for the development of marginal fields in deep water, Proceedings of the fifth International Offshore and Polar Engineering Conference, The Hague, The Netherlands, June 11- 16, pp 163.
[5] Chandrasekaran, S., Mayank, S. 2017. Dynamic analyses of stiffened triceratops under regular waves: experimental investigations, Ships and Offshore structures, 12(5):697-705.
[6] White N Charles, Copple W Robert, Cunyet Capangolu. 2005. Triceratops: An effective platform for development of oil and gas fields in deep and ultra-deep water, Proc. Fifteenth Int. Offshore and Polar Eng. Conf., Seoul, Korea, June 19-24, p.133-139.
[7] Chandresekaran, S., Madhuri, S., Jain, AK. 2013. Aerodynamic response of offshore triceratops, Ships and Offshore Structures, 8(2):123–140.
[8] Chandrasekaran, S., Madhuri, N. 2013. Response analyses of offshore triceratops to seismic activities, Ship and offshore structures, 9(6):633-642.
[9] Chandrasekaran, S., Madhuri, S. 2015. Dynamic response of offshore triceratops: Numerical and experimental investigations, Ocean Engg., 109(15):401-409.
[10] Adrain Biran, Ruben Lopez Pulido. 2013. Ship hydrostatics and Stability, Butterworth-Heinemann.
[11] Rho JB, Choi HS, Lee WC, Shin HS, Park IK. 2002. Heave and pitch motion of a spar platform with damping plate, Proc. of Twelfth Int. Offshore and Polar Eng. Conf., Kitakyshu, Japan, 1:198–201.
[12] Rho JB, Choi HS, Lee WC, Shin HS, Park IK. 2003. An experimental study for mooring effects on the stability of spar platform, Proc. of Thirteenth Int. Offshore and Polar Eng. Conf., Honolulu, 1:285–288.
[13] Patel MH, Park HI. 1991. Dynamics of Tension Leg Platform Tethers at Low Tension. Part I - Mathieu Stability at Large Parameters, Marine Structures, 4(3):257-273.
[14] Chandrasekaran S, Chandak NR, Gupta Anupam. 2006. Stability analysis of TLP tethers¸ Ocean Engg., 33(3-4): 471-482.
[15] Simos AN, Pesce CP. 1997. Mathieu stability in dynamics of TLP tether considering variable tension along the length. Trans. on Built Environment, 29:175–186.