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Comparing deepwater sediments from South China Sea with Gulf of Guinea sediments

Published: This paper was prepared for presentation at the Offshore Technology Conference held in Houston, Texas, USA, 6–9 May 2013. Paper No 24010. Copyright 2013, Offshore Technology Conference.

06 May 2013
E. Palix, Fugro; N. Chan, Fugro; Z. Yangrui and W. Haijing, China Oilfield Services Ltd

The first deep water geotechnical survey in South China Sea has been performed at Liwan 3-1 Field in Pearl River MouthBassin. The investigation comprised Piezocone Penetrometer Tests (PCPT), T-bar, insitu vane tests, pore pressure dissipation tests, jumbo piston cores, box cores, along with advanced laboratory testing. The in-situ and laboratory data results obtained have been used together with the geophysical data (AUV data) to provide the soil design parameters used for the design of the deepest PLEM and Manifold foundations (i.e. between 1300 and 1500m WD). The high quality and variety of in-situ and laboratory tests performed enable a sound comparison with other deep water sediments. Most of the soil properties of the Liwan 3-1 clays are in the range of those encountered in the Gulf of Guinea (Colliat et al. 2010). The use of scanning electron microscopy (SEM) revealed highly structured clay what is in accordance with the relatively high sensitivity of about 5 to 9 obtained from T-bar tests after 30 cycles. However some particularities arise in their mechanical behavior. The shear strength anisotropy (i.e. answer under different modes of shearing) is for example not significant. It can also be noted that the increase of shear strength with time or with the rate of shearing (i.e. respectively the thixotropy and rate effects) are less pronounced.


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