Geotechnical Analysis of a Mat Foundation Supporting a Wellhead Platform
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 147, Issue 11
Abstract
China National Offshore Oil Corporation (CNOOC) currently is developing a mat-supported wellhead production platform concept as an alternative solution to conventional jacket platforms in shallow-water oil fields. The platform is towed to the site with the mat foundation elevated. The mat then is lowered and embedded in the seabed as the hull is jacked out of the water. Steel pipe piles subsequently are driven through the tubular legs of the platform. After grouting the connection, the pile foundations provide permanent support for the platform. The mat foundation therefore provides only temporary support to the platform. This paper presents a case study focusing on the installation behavior of the mat foundation in a soft soil site as part of the platform concept development and suitability evaluation. The study determined (1) the expected penetration depth under the platform’s self-weight considering its irregular geometry and soft over stiff clay stratigraphy; (2) the target center of gravity to achieve even penetration and the potential for tilt development in the case of offset from the target position; (3) the effectiveness of using ballast tanks to correct the tilt; and (4) settlement after the installation due to dissipation of pore pressure and creep. Advanced large-deformation finite-element simulations featuring a strain softening soil model and analytical analyses were performed. A dedicated lab testing program geared was designed and executed to provide the necessary soil parameters for the analyses. This paper presents the techniques and considerations that were applied in this study and insights gained into the installation and subsequent postinstallation behavior of large-area mat foundations.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 147 • Issue 11 • November 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Oct 8, 2020
Accepted: Jul 12, 2021
Published online: Aug 27, 2021
Published in print: Nov 1, 2021
Discussion open until: Jan 27, 2022
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Cited by
- Run Liu, Runbo Cai, Guangsi Chen, Chao Liang, The bearing capacity of A-shaped mat foundations on cohesive soil, Ships and Offshore Structures, 10.1080/17445302.2022.2116208, (1-10), (2022).