Design and development of a hazard map for the positioning and siting of large jack-up rigs at the geologically complex areas of the Gulf of Suez

Design and development of a hazard map for the positioning and siting of large jack-up rigs at the geologically complex areas of the Gulf of Suez

Lietaert, B.K.J.

Ngan-Tillard, D.J.M. (mentor)
Van Paassen, L.A. (mentor)
Kortekaas, S. (mentor)
Van der Wal, T. (mentor)

Civil Engineering and Geosciences

Geotechnology

Geo-engineering

2011-06-30

The aim of this research project is to develop a hazard map for punch-through failure during jack-up rig installation in the Gulf of Suez. This map can be used to make an upfront assessment of unfavorable foundation conditions at a proposed installation site. This is not self-evident due to the complex geological setting of the area. Data to complete this research was provided by Fugro Engineers B.V.. The available data set contains (geotechnical) borehole data, geophysical data, bathymetric data and information regarding the surface sediments in the Gulf of Suez. The borehole data are used to perform bearing capacity calculations for different kinds of spudcan foundations, ranging in diameter between 10 m and 18 m. These calculations resulted in a distinction between locations with a “safe” profile and locations for which a punch-through profile is generated. At these unfavorable locations, the actual risk of a punch-trough failure will depend on the deployed rig and the corresponding preload. Therefore, a factor of safety is calculated for these risky locations. The data was integrated into an ArcGIS project. Data analysis resulted in the identification of different safe and risky zones regarding punch-through occurrence. The identified zones turned out to be valid for every spudcan with a diameter between 10 m and 18 m. An observed trend is that for a constant preload, the risk for punch-through decreases if the spudcan diameter increases. Generalization of the identified zones into depositional environments allowed the production of a risk map that also covers these areas in the Gulf of Suez for which no data was available. Two environments turned out to have the highest risk for punch through failure. The first environment is characterised by a deep bathymetry and fine grained sediments, possibly with coarse grained intercalations. Punch-through in these areas is related to these coarse grained intercalations or to different degree of consolidation inside these fine grained packages. The second environment is related to areas where wadis bring a lot of sediment into the Gulf of Suez and develop an alluvial fan at their mouth. Mixing of this coarse grained input with finer grained deep water sedimentation results in the generation of punch-through profiles. Finally, for two areas with a high borehole concentration, an attempt was made to develop 3D ground models with the SGeMS software package. The bearing capacity inside the grid was predicted by applying ordinary kriging between the boreholes. The accuracy of these models and the practicability of the SGeMS program are thoroughly discussed.

Gulf of Suez
jack-up rig
hazard map
punch-through failure
bearing capacity
3D model
ArcGIS
SGeMS

http://resolver.tudelft.nl/uuid:325eb00b-038e-4ebd-893a-2e4a42e251cd

Student theses

master thesis

(c) 2011 Lietaert, B.K.J.