The Challenges of Siting Facilities along the Sigsbee Escarpment in the Southern Green Canyon Area of the Gulf of Mexico: Framework for Integrated Studies.
Authors: Jeanjean Philippe , Hill Andrew , Taylor Stephen 
Published: October 2008

The Sigsbee Escarpment is a major regional geomorphological feature of the Gulf of Mexico seafloor, with evidence of numerous major slope failure events during the relatively recent geological past. The Mad Dog and Atlantis field areas lie beneath the Sigsbee Escarpment, making the effective siting of facilities to efficiently develop the fields close to or on the escarpment itself of great strategic importance.

This paper describes the key processes and skills involved in the analysis of geohazards related to the Sigsbee Escarpment, leading to the choice of safe facility locations, and emphasizes the need for cross-disciplinary work to deliver the required results. The paper also describes the practical challenges of conducting studies and fieldwork in such a complex geological setting - especially within the context of a fastpaced field development schedule.

The proper assessment of geohazards takes considerable planning. The many types of field data collection activities have to be planned and managed in parallel; bearing in mind that the results of one dataset will have a direct impact on the needed acquisition of other data types. Large volumes of highresolution data must be interpreted and shared between various discipline teams; itself providing logistical problems. During the projects described, although time and human resources were limited due to the fast project pace quality answers were provided in a timely fashion to the projects' facility teams.

Introduction to the Mad Dog and Atlantis Fields

The Mad Dog and Atlantis fields are located in the Southern Green Canyon protraction area of the Gulf of Mexico. The geological and geomorphological setting is one of the most complex settings faced in the development of deepwater fields in the world.

Most of the Mad Dog field lies in Green Canyon (GC) blocks GC742, GC743, and GC786; the Atlantis field mainly lies in blocks GC699, and GC743. BP will develop the Mad Dog field with partners BHP Billiton Petroleum and Unocal, and will develop the Atlantis field with BHP Billiton Petroleum. BP will operate both fields.

The fields straddle three distinct geological provinces: the southern edge of the northern Gulf of Mexico continental slope, the Sigsbee Escarpment, and the upper continental rise. Fig. 1 shows the seabed relief of the area. Although the aerial extent of the field reservoirs is not shown, the location of the discovery and appraisal wells hint at how the reservoir is located with respect to the escarpment. Due to the disposition of the developable reserves it becomes of critical importance to locate facilities as close as possible to the escarpment, either at the upper edge (Mad Dog) or the foot (Atlantis) of the escarpment (Fig. 2).

Need and Purpose of Integrated Geohazard Studies

One of the main challenges faced on these two projects is the sheer scale of the seabed features present at the sites. At Mad Dog, the top of the escarpment (Slump 8, see Young et al, 2003) is located only 1200 ft (365m) away from the proposed spar center. Below the slope break, the escarpment dips to the south at an average angle of 19 degrees.