Alternative Title

Jackup Rig Spud Can Penetration: A 6,000 Ton Load Test

Location

Arlington, Virginia

Session Start Date

8-11-2008

Session End Date

8-16-2008

Abstract

One of the most exciting geotechnical problems for the offshore engineer is the prediction of mobile jack-up rig spud can penetration. Jack-up drilling rigs are used to drill offshore oil and gas wells in water depths up to about 100 m. The rigs are supported by circular “spud can” foundations fitted at the end of extendable platform legs. Upon arrival to the site the jack-up extends the legs to the sea floor and self-elevates out of the water. This action forces the spud cans into the seabed until soil capacity is attained. Prior to jacking the rig out of the water, a geotechnical borehole is made from the rig to verify soil conditions and estimate bearing capacity and leg penetration. The geotechnical engineer makes predictions of foundation capacity in real time; the predictions are then verified by the actual behavior of the footing under the 6,000 ton preload. This paper presents experience with bearing capacity predictions versus field measurements from over 15 offshore sites. Relatively simple closed form bearing capacity formulas are shown to provide good predictions for real behavior of these large scale foundations.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Sixth Conference

Publisher

Missouri University of Science and Technology

Publication Date

8-11-2008

Document Version

Final Version

Rights

© 2008 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Case Histories Paper: Jackup Rig Spud Can Penetration: A 6,000 Ton Load Test

Arlington, Virginia

One of the most exciting geotechnical problems for the offshore engineer is the prediction of mobile jack-up rig spud can penetration. Jack-up drilling rigs are used to drill offshore oil and gas wells in water depths up to about 100 m. The rigs are supported by circular “spud can” foundations fitted at the end of extendable platform legs. Upon arrival to the site the jack-up extends the legs to the sea floor and self-elevates out of the water. This action forces the spud cans into the seabed until soil capacity is attained. Prior to jacking the rig out of the water, a geotechnical borehole is made from the rig to verify soil conditions and estimate bearing capacity and leg penetration. The geotechnical engineer makes predictions of foundation capacity in real time; the predictions are then verified by the actual behavior of the footing under the 6,000 ton preload. This paper presents experience with bearing capacity predictions versus field measurements from over 15 offshore sites. Relatively simple closed form bearing capacity formulas are shown to provide good predictions for real behavior of these large scale foundations.