Abstract

Recent oil and gas exploration efforts have met with success in the deepwater environment along the Sigsbee Escarpment in the north-central Gulf of Mexico. The topography of the Sigsbee is steep and irregular with numerous faults and slumps occurring on the Escarpment face. The complex topography is challenging for the collection of high-resolution geophysical data. Engineering quality survey data for the installation of export pipelines, infield flowlines and production facilities is needed. BP Exploration and Production Inc. (BP) recognized the limitations of the current survey technology and put forth a push in the industry for the development of a deepwater, Autonomous Underwater Vehicle (AUV) survey platform. A commitment for state-of-the-art survey technology by BP resulted in C & C Technologies, Inc. (C & C) teaming with Kongsberg Simrad to develop an AUV platform for the deployment of high-resolution survey instrumentation capable of surveying to a maximum depth of 3,000 meters. An overview of the system, data processing and data examples from missions completed across the Sigsbee Escarpment are presented in this paper.

The data from the AUV has provided a dramatic advance in the ability to map the seafloor, but it produces a large and diverse data set that can challenge our ability to process and manage the data. The great density of these digital data, however, offers the opportunity to take advantage of interactive 3D visualization techniques that can improve the efficiency and accuracy of processing, and provide an unprecedented perspective of seafloor morphology and processes. Fledermaus interactive 3D visualization software is used to aid in the analysis of the data. This program allows the interpreter to analyse in a single scene all the data fromAUV survey, including the seabed from the multibeam sonar, draped side scan, subbottom profiles and the planned pipe routes.

Introduction

The HUGIN 3000 Autonomous Underwater Vehicle (Figure 1), a third generation AUV from Kongsberg Simrad, resulted from the engineering efforts of C & C and Kongsberg Simrad1. The payload of the AUV consists of three major remote-sensing systems2, 3 (Figure 2). A Kongsberg Simrad EM2000 Multibeam collects high-density soundings in a swath perpendicular to the direction of motion. The AUV depth is recorded with a precision, survey quality depth sensor. Sonar imagery is logged with an Edgetech dualfrequency side scan sonar and high-resolution seismic profiles are obtained with an Edgetech 216 chirped subbottom sonar. Inertial navigation is used for positioning of the AUV and a battery supplies power for mission times approaching 45 continuous hours. Numerous ancillary sensors monitor the AUV and feed information to the artificial intelligence programs controlling the motion and health of the AUV.

The construction of the third-generation HUGIN AUV was performed at Kongsberg Simrad's Norway facilities in late 1998. The vehicle was delivered to the United States in August 1999 and sea trials began in the Gulf of Mexico. Sea trials were conducted over the next several months and the HUGIN was officially commissioned as a commercial survey vehicle in January 2000.

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