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ABSTRACT Obtaining very high resolution seismic images of sediments near the sea floor in deep water is fraught with problems. The conventional approach has been to tow a subbottom profiler near the bottom but, if the water depth is a kilometre or more, vessel speed and manoeuverability are so restricted that it becomes more economical to mount the profiler on an autonomous underwater vehicle. Either way, the survey would be expensive. Moreover, in depths of a kilometre or more, source energy levels are so restricted that the depth of subbottom penetration is limited to a few tens of metres. A research program at the University of Mississippi has been investigating ways of improving seismic resolution while achieving significant penetration and has obtained some remarkable results in the Gulf of Mexico. Deploying a commercial watergun just below the surface of the water and towing a single-channel hydrophone array at a few hundred metres depth, the program has demonstrated that, in a thousand metres of water, sea-floor resolutions of tens of centimetres and penetration of hundreds of metres can be achieved. Vessel speeds were typically 2–4 knots but it is likely that higher speeds are possible. The demonstrated results were achieved by combining rapid digitization with state-of-the-art signal processing. Processing was done on a desktop computer and easily could have been done on board ship. The method is discussed and illustrated by examples of both raw and processed data. INTRODUCTION Reflection seismic profiling has been used throughout most of the 20 th century to map deep geologic formations. The method was revolutionized in the late 1950s and early 1960s when digital technology was applied to petroleum exploration. Three decades later digital seismic profiling was being used to image shallow formations for engineering and environmental purposes.
- North America > United States > Louisiana (0.30)
- North America > United States > Mississippi (0.26)
ABSTRACT The possibility of designing and developing a remote, multi sensor, monitoring station for long term investigation and research of the near-sea-floor hydrocarbon system within the hydrate stability zone of the northern Gulf of Mexico has been discussed for some years. A program was initiated in 1999 to design and assemble a station which will monitor physical and chemical parameters of the sea water and sea-floor sediments on a more-orless continuous basis over an extended period of time. It is planned that an operational station will be installed in at least a thousand meters of water by 2004. The heart of the station will be a net of vertical arrays of sensors. Each array will occupy the lower portion of the water column and a hole bored into the sea floor. Sensors will include hydrophones to record compression waves, thermistors to measure temperature within the water and the sediment, and optic fibers connected to an optical spectrometer to identify and quantify hydrocarbon gases. The lowermost sensor of each array will be a three-component accelerometer pushed into the sediments at the bottom of the hole to record compression and shear waves. Peripheral sensors will include a sea-floor positioning system and an acoustic doppler current profiler. Also, if sufficient electrical power is available, several video systems with pan and tilt capability will be installed. The video images would be posted on a web site in near-to-real time and made available for educational and public outreach purposes. The most likely scenario is that, at first, the data will be recorded on the sea floor and periodically downloaded by an underwater vehicle. Eventually, the station will be connected via optic fiber to a surface structure, such as an oil platform, and the data transmitted in near-to-real time to a shore facility at the Stennis Space Center.
- North America > United States > Mississippi (0.49)
- North America > United States > Texas (0.47)
- Geology > Structural Geology > Tectonics (1.00)
- Geology > Geological Subdiscipline (0.94)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- North America > United States > Gulf of Mexico > Central GOM > West Gulf Coast Tertiary Basin > Green Canyon > Block 52 > Marquette Field (0.93)
- North America > Canada > Alberta > Joliet Field > Bonavista Joliet 10-31-25-7 Well (0.93)