The integrated study performed to characterize the Marlin Deepwater Field is presented herein. The work included the integration of 2-D high-resolution data, side scan sonar records, and 3.5 kHz sub-bottom profiler imagery with geotechnical data to properly characterize the site. The geohazards present at the site include faults, fluid expulsion zones, shallow gas, and buried landslides. They are described and their influence on geotechnical properties is discussed. The extensive monotonic and cyclic advanced geotechcal laboratory testing program is also documented. Key results are summarized in simple diagrams that can be used in practical design to calculate the holding capacity of suction caissons for floating production systems at Gulf of Mexico deepwater locations.


Unlike the simple shallow soil and geologic conditions at most fields developed to date on the Gulf of Mexico (GoM) continental shelf, shallow geologic conditions in deepwater on the GoM continental slope off Texas and Louisiana are among the most complex offshore conditions in the world (Fugro 1991). These conditions constitute a dynamic geosystem with ongoing salt uplift, faulting, landsliding, and gas seepage.

To help avoid costly delays in project fast tracking, integrated studies provide a coherent and reconciled picture of the sods in the zone of interest for field development activities (excluding drilling activities). Geoscientists and geotechnical engineers work together and combine results of geophysical and geotechnical surveys to accurately describe the properties and spatial variation of soil deposits at the site.

Although used worldwide, suction caissons had not been used in the Gulf of Mexico at the tune of the Marlin site geotechnical investigation (January 1996) and have so far (March 1998) been used only for single point mooring of supply vessels. Several oil companies, however, have definite plans to use them in the near future for production platform spread moorings.

Very limited information exists in the open literature on the monotonic and cyclic behavior of deepwater GoM highly plastic clays, as it pertains to suction caisson design. The partial results presented and summarized herein extend the knowledge of GoM deepwater clay behavior for suction caisson design purposes. More dews on how to use the results in design are available in Jeanjean et al(1998).

This paper will describe the specific geophysical surveys and the geotechnical site investigation performed at the Marlin site. Integrated results will be presented and the influence of the numerous geohazards at the site on the soil properties used for foundation design will be discussed.

Overview of Marlin Project

This integrated study was performed for the Marlin prospect, which is m Viosca Knoll Block 915 about 145 miles east-southeast of New Orleans, Louisiana (Fig. 1). The field will be produced by a Tension Leg Platform (TLP) which will be anchored m 3249 ft (990 m) of water by driven piles. Installation is scheduled for early 1999.

Because of schedule constraints, the geophysical and geotechnical site investigations had to be performed before the final system selection was made. In the initial stages of the project, and at the time of the investigations

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