Effects of Oil and Gas Exploration and Development at Selected Continental Slope Sites in the Gulf of Mexico
- David A. Gettleson (Continental Shelf Associates, Inc.) | Alan D. Hart (Continental Shelf Associates, Inc.) | Stephen T. Viada (Continental Shelf Associates, Inc.) | Neal W. Phillips (Continental Shelf Associates, Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, 29-31 March, Calgary, Alberta, Canada
- Publication Date
- Document Type
- Conference Paper
- 2004. Society of Petroleum Engineers
- 5.5.2 Core Analysis, 1.6 Drilling Operations, 4.1.5 Processing Equipment, 4.3.4 Scale, 1.11 Drilling Fluids and Materials, 1.6.9 Coring, Fishing, 1.2.3 Rock properties, 5.6.5 Tracers, 4.5.4 Mooring Systems, 2.1.7 Deepwater Completions Design
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A field study was conducted between November 2000 and August 2002 to assess benthic impacts of drilling at four sites on the Gulf of Mexico continental slope. The study applied a combination of conventional and innovative techniques that have not been used previously to monitor deepwater drilling in the Gulf of Mexico. Particularly useful methodologies included geophysical mapping of mud and cuttings deposits using an autonomous underwater vehicle; digital analysis of sediment color; analyses of sediments for concentrations of barium (a drilling fluid tracer) and hydrocarbons found in synthetic-based drilling fluids; and sediment profile imaging of sedimentary conditions and benthic infaunal communities.
The Gulf of Mexico has seen a remarkable increase in deepwater oil and gas exploration, development, and production in recent years [1,2,3]. Studies on the continental shelf have documented impacts of water-based drilling fluids and cuttings on benthic animals near drillsites [4,5]. However, because of environmental and technological differences, the applicability of this knowledge to deepwater benthic communities is limited [6,7]. For example, the increased use of synthetic-based drilling fluids (SBFs), may result in volumes and characteristics of discharged material quite different from those used for decades in shallower water [8,9]. To date, there have been few field measurements and observations around deepwater drillsites in the Gulf of Mexico, in part due to the technical challenges of sampling in water depths greater than 1,000 m.
A field study was conducted between November 2000 and August 2002 to assess benthic impacts at four sites on the Gulf of Mexico continental slope (Fig. 1). The study applied a combination of conventional and innovative techniques that have not been used previously in environmental monitoring of deepwater drilling in the Gulf of Mexico, including:
Use of an autonomous underwater vehicle (AUV) to geophysically map mud and cuttings deposits.
Quantification of SBF concentrations in bottom sediments.
Use of a dragged camera sled to obtain photographs of the seafloor and benthic organisms.
Digital analyses of photographs for seafloor color and texture.
Combination of conventional box core sampling, photographic analysis, and sediment profile imagery to characterize the benthic environment (e.g., redox conditions) as well as benthic communities.
Specialized biological studies of harpacticoid copepod genetics, microbial abundance, and sediment toxicology.
Study objectives were to document (1) drilling mud and cuttings accumulations; (2) physical modification/disturbance of the seabed due to anchors and mooring systems; (3) debris accumulations; (4) physical/chemical modification of sediments; and (5) effects on benthic organisms.
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