Page 19 - 2016Winter

Seismic surveys are not only used during the exploration for oil and gas but are also used throughout the life span of a producing oil or gas field. The term 4-dimensional (4-D) surveys refer to repeated 3-D surveys conducted at intervals of months or years to check the progress in tapping oil or gas deposits during the productive life of a deposit, which may last for 30 yr or more. Some 4-D survey effort may be replaced by installing fixed nodal receive arrays on the sea- floor and using drilling noise or seafloor vibrational sources instead of towed airgun arrays (Blackburn et al., 2007).
Summary
sions about a technology that has substantial environmental, economic, and energy policy implications.
Acknowledgments
I thank International Association of Geophysical Contrac- tors (IAGC) Chairman Roger Keyte of Fairfield Nodal for his help with all aspects of geology, geophysics, and the seismic industry. So many people in the geophysical indus- try have shared generously of their expertise to educate me about seismic surveys and survey technology, but rather than name a few and miss others, I will not name names; they know who they are and I am immeasurably grateful to them all. Any errors are mine; I had great teachers and pa- tient ones at that. Special thanks to Rob McCauley (Curtin University) and Woodside Energy Ltd. for making a con- tract report available for use as an open reference and per- forming some quick additional analyses to help me make a point about the visual representation of propagated impulse sound.
Biosketch
Robert (Bob) Gisiner is the Interna- tional Association of Geophysical Con- tractors (IAGC) director of marine en- vironmental science and biology. Before joining the IAGC, Dr. Gisiner enjoyed a 21-year career with the US Navy as a research scientist, research program
manager, and environmental compliance branch head. Dr. Gisiner also served as scientific program director for the US Marine Mammal Commission from 2006 to 2010. He is a recipient of the Navy Meritorious Civilian Service Award and author or coauthor of numerous peer-reviewed scien- tific papers and professional presentations. He has served on several expert panels on topics in marine bioacoustics, pro- tected species recovery, and marine ecosystem management.
References
Blackburn, J., Daniels, J., Dingwall, S., Hampden-Smith, G., Leaney, S., Le Calvez, J., Nutt, L., Menkiti, H., Sanchez, A., and Schinelli, M. (2007). Borehole seismic surveys: Beyond the vertical profile. Oilfield Review 19, 20-35. Available at https://www.slb.com/~/media/Files/resources/oilfield_ review/ors07/aut07/borehole_seismic_surveys.pdf Accessed August 30, 2016.
Bureau of Ocean Energy Management (BOEM). (2014). Final Programmat- ic Environmental Impact Statement: Mid-Atlantic and South Atlantic Plan- ning Areas, vol. 3. OCS EIS/EA BOEM 2014-001, Gulf of Mexico Outer Continental Shelf (OCS) Region, Bureau of Ocean Energy Management,
Marine geophysical surveys using compressed air sound sources (airguns) have been in widespread use for over 50 yr. The basic technology of the source and the methodology of towed array surveys has not changed significantly over that time. But advances in computer technology since the 1980s have had a tremendous impact on seismic surveys, enabling exploration of new nonimpulse sound source technologies, encouraging the collection of larger 3-D data sets that cover more area with less acoustic output, and making possible a wide range of innovative multivessel data-collection meth- odologies (WAZ, RAX, and others). Unfortunately, the avail- able space cannot do justice to the equally profound change in the analysis of survey data made possible by modern su- percomputing technology (Yilmaz, 2001). Mathematically, intensive signal-processing innovations have enabled old data sets to yield new information as well as shaping deci- sions about the collection of new data sets. Changes in busi- ness practices within the industry, such as the trend toward multiclient surveys and away from single-customer pro- prietary surveys (International Association of Geophysical Contractors [IAGC], 2016), also need to be understood to fully appreciate the consequences of changes to the technol- ogy and the way in which it is used. Finally, although I have presented seismic surveys mainly in the context of oil and gas exploration, it is critical to keep in mind that the same technology has always had many other applications that range from basic research about the structure of our planet to coastal disaster preparedness, renewable energy develop- ment, and mapping of national claims to expanded offshore territory (CBC, 2016).
Seismic surveys and the technologies that support them are currently experiencing an unprecedented level of public at- tention. It is hoped that this article will provide scientists, regulatory agencies, and the concerned public with a better understanding of the technology and its uses to inform deci-
Winter 2016 | Acoustics Today | 17