Addressing the Challenges in the Placement of Seafloor Infrastructure on the East Breaks Slide-A Case Study: The Falcon Field (EB 579/623), Northwestern Gulf of Mexico
Authors: Hoffman John S. , Kaluza Michael J. , Griffiths Richard , McCullough Gary , Hall Joey , Nguyen Thien 
Published: October 2008

The East Breaks Slide is a late Pleistocene shelf-slope instability feature that has impacted some 342-square miles in the western portion of the East Breaks Federal lease area (EB) in the northwestern Gulf of Mexico. However relict this slide may be it has a significant impact on the present seafloor displaying irregular, tilted, and rotated blocks of intact stratigraphy within an amorphous and disturbed slump matrix. The Falcon Field is near the center of the western lobe of the slide in EB 579 and 623. One of the challenges faced by the operators was to locate a feasible pipeline route from the Falcon Field to the host platform in Mustang Island Block A- 103. The rough topography over the East Breaks Slide restricted a direct route from the field to the host platform. An irregular seafloor and potential slope instability were two factors that had to be addressed for selecting a pipeline route, and at the same time, keeping the route as short as possible. Both factors could have a significant impact on the potential for spanning of the pipeline and stability of the bottomfounded man-made infrastructure planned.

Pre-survey route planning was undertaken using public bathymetric data and proprietary 3D seismic data. A digital terrain model (dtm) of the seafloor was developed from which potential routes were viewed and cross-sections cut to determine if pipe span would be an issue. Changes and alternative considerations to the routing could be done using these data sets to investigate multiple route scenarios.

The Falcon Team had a promising route selected before any high-resolution field survey was commissioned and little change to the routing was necessary. The field work was planned with a contingency of altering the route within the slide if the planned route was not feasible based on the survey. Minor alterations were made to the route within the slide, but the survey corridor was adequately planned through the slide feature to accommodate the changes. Once the route was determined a routine hazards assessment report was completed and issued to satisfy Minerals Management Service requirements.

Introduction

The East Breaks Slide is a late Pleistocene shelf-slope instability feature in the northwest Gulf of Mexico that has impacted some 342-square miles in the western portion of the East Breaks Federal lease area, and extends into the Alaminos Canyon area to the south (Figure 1). Although a relict feature, the slide has had a significant impact on the present seafloor. The seafloor is very irregular and rough where impacted by the slide.

Mariner Energy, Inc., (Mariner) and Pioneer Natural Resources U.S.A. Inc., (Pioneer) made a significant gas discovery in EB 579 in 2001, and a subsequent side-track well in Block 623. The discovery known as the Falcon Field lies directly within the path of the East Breaks Slide. Mariner and Pioneer committed to developing the Falcon Field and evaluated several development scenarios, both technically and commercially to best exploit the reserves. A two-well subsea system, with provisions for future expansion was decided as the optimal plan and was put in place.