TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Mad Dog prospect is located along the Sigsbee Escarpment in the southeastern portion of the Green Canyon Area. The Mad Dog mooring system straddles the Sigsbee Escarpment ( Figure 1). A total of eleven mooring piles arranged in three clusters were planned for this mooring system.Two clusters are situated along the Lower Continental Slope and one cluster is situated along the escarpment. The paper describes the complex surficial geologic setting as well as the geohazards present at the site and how they influenced the anchor locations of the chosen mooring pattern. The unique challenge of this project was the effort put forth to understand the mooring system in variable and complex areas at each anchor cluster.

The complex geologic development of the Sigsbee Escarpment in the Southern Green Canyon area has been studied in great det ail using a comprehensive suite of geophysical and geotechnical data. Integration of these data led to the recognition of certain geologic indicators that assist, either directly, or indirectly, in "filling the gaps" in the geologic history of the Atlantis area. These indicators include:the Law of Superposition,regional stratigraphic markers,sedimentation rates,seafloor current processes, andfault offsets. These indicators provide both relative and absolute timing constraints on the occurrence and level of activity of various geologic depositional and erosional processes in the Atlantis prospect area. They are most beneficial where quantitative dating methods (i.e. radiocarbon dating) cannot be used or do not adequately constrain the timing and relationship of geologic processes and events. In this way, they play a vital role in assessing the past, present, and potential future rates geologic activity that is critical to the success of the Atlantis development. Introduction BP America, Inc., and its partners are currently evaluating the feasibility of installing various production facilities along the Sigsbee Escarpment in the southern Green Canyon area, Gulf of Mexico (Figure 1). Current development plans call for the seabed installation of architecture such as anchors, manifolds, flowlines, umbilicals, and export pipelines. The complex geologic development of the Sigsbee Escarpment has been studied in great detail using an integrated suite of geophysical and geotechnical data. These data were correlated to portray the chronology of active geologic processes over roughly the past 30,000 years. Integration of these data also led to the recognition of certain geologic indicators that assist, either directly, or indirectly, in "filling in the gaps" in the geologic history of Atlantis. These indicators include:the Superposition of stratigraphy and geologic features,the Triplet and other regional stratigraphic markers,sedimentation rates,seafloor current processes, andfault offsets. Use of these indicators provided a relative sequence for the occurrence and level of activity of various geologic processes in the Atlantis area where the quantitative dating methods (i.e. radiocarbon or paleontological) cannot be used or do not reveal significant insights into the timing and relationship of geologic processes and events. Thus, using indirect geologic indicators of sequencing and dating of geologic processes at Atlantis have been key in understanding the geologic history and rates of activity of geologic processes. When integrated with the entire suite of data, they contribute vital information about past, present, and future rates of activity for geologic processes; an understanding of which is critical to the success of the Atlantis field over its projected lifetime Available Data Several data types were used to identify and correlate the aforementioned geologic indicators including geophysical, geotechnical, radiocarbon dating, and various laboratory tests. The geophysical data consisted of two 3D speculative surveys, 2D high-res seismic lines, two 3D high-res seismic surveys, and shallow high-resolution data consisting of multibeam sounding, side-scan sonar, and subbottom profiler. The geotechnical field study programs consisted of 4- in. jumbo piston cores, 3-in conventional piston cores, box cores, and deep soil borings.

The movement of petroleum exploration and production to the frontier deepwater and ultra-deepwater of the Gulf of Mexico presents a variety of engineering challenges. One such challenge is the placement of seafloor production infrastructure on or near the base of steep slopes associated with the Sigsbee Escarpment. As a result, the potential hazards associated with shallow seated slope failures have become a legitimate concern. These types of failures can result in the formation of debris flows and turbidity currents capable of damaging or destroying seafloor structures in their path. The potential for significant damage or loss of seafloor facilities from such an event merits a comprehensive understanding of the factors that influence shallow slope failures. However, total field coverage with geotechnical cores to assess these factors is neither logistically or economically feasible nor practical. We present a new method for integrating these factors with available geotechnical core data and 3D seismic to quantitatively extrapolate and predict the location of critical areas of potential shallow seated slope failure.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe geological setting of the Mad Dog anchoring system has been described by Berger et al (2006) and the details of the geotechnical investigation performed to design the anchors given by Liedtke et al (2006). This companion paper describes how the results of the geotechnical campaign were integrated with the high-resolution geophysical data to define the geotechnical and bathymetric constraints associated with the anchor locations and to provide input to the geotechnical design.For Cluster 2, located on the Sigsbee Escarpment, the paper highlights the great care that was taken in positioning the anchors close to the location of the soil borings and Cone Penetrometer Tests (CPTs) and on seabed with acceptable slope angles.