September 1998 Vol. 219 No. 9  Exploration

Perry A. Fischer,  Engineering Editor

Geophysicists: Hungry for a brontobyte?

No doubt, the extraordinary advances in computer technology have revolutionized the exploration industry. Improvements in seismic acquisition and interpretation, borehole geophysics, magnetic and gravity surveys have resulted in wildcat success rates and recovery ratios that would have seemed improbable 20 years ago.

Seismic surveys often acquire data in the megabytes-per-second range. Thus, an exploration company with many 3-D and 4-D jobs can amass a great quantity of data. Add to this: magnetic, gravity, bathymetry, satellite photos, field notes, geochemistry, core analysis, maps, well log and lease information, and ... well, you get the picture. The amount of data becomes staggering.

Words such as megabyte and terabyte are commonly used, and petabyte is now gaining familiarity. To ensure that there will always be words to describe increasingly mind-numbing amounts of information, more terms have been invented, culminating in the mother-of-all-bytes, the brontobyte.

World Oil previously featured articles on mass data storage in September and October 1995, and September 1996 issues. Now five heavy hitters have joined forces to create PetaSTAR, a geodata management and storage all-in-one solution. The system loads, archives and indexes automatically, and can transfer data at 11.8 MB/sec for standard SEG-Y and SEG-D formats.

Sony contributed the data repository, a fully automated tape library, scalable from 378 gigabytes to 2.3 petabytes. Sun Microsystems built the server; LSC wrote the data storage management software; Panther contributed the seismic data manager; and ODS supplied the software for image display and component integration. The system works with all leading software applications, such as those offered by Landmark, Geoquest, Paradigm and Charisma.

Data quality dilemma. Now that you have all this data, how do you preserve it? A variety of environmental factors attacks the tape emulsion, causing it to degrade with time. Speaking at the European Association of Geoscientists & Engineers (EAGE) show in Leipzig, IBM's Mark C. Meyer said 60% to 70% of all seismic data is probably garbage. Recovering such damaged data becomes increasingly expensive as tape libraries age. Meyer pointed out a situation in which an unnamed operator had to employ five people full time for 21 days to recover data from newly acquired tapes.

In terms of financial assets, this means that seismic libraries were overpriced on companies' balance sheets, because the tapes would have to undergo costly and extensive cleanup before use. IBM's Alan Bays added that such libraries often needed better filing systems since the data is essentially worthless if users cannot readily access it.

Record streamer. Veritas DGC launched its flagship vessel, the SRV Veritas Viking in June. Built by Mjellem & Karlssen (M&K), the 305-ft vessel has the potential to deploy up to 16 streamers, but was initially configured with dual sources and eight 24-bit RDA streamers, each 5,000 m. Other configurations include six streamers ´ 8,000 m (3,840 channels); or four streamers ´ 10,000 m. Seismic instrumentation consists of a SYNTRAK 960, 24-bit recording system, while the streamers are manufactured by Syntron.

Veritas claimed an industry towing record for the longest streamer on July 8. The 12,000-m streamer was deployed during the beginning of its long-offset seismic program in the White Zone / Faeroes Island area. "This year's survey has been designed to record converted waves to image sediments below the high-velocity basalt common to this area," says Elwyn Jones, VP of Business Development. "Conventional long offsets have utilized the Wide Aperture Recording (WAR) technique, which uses alternating sources and increasing separation between two vessels."

However, the WAR technique is expensive and has several limitations (for a complete discussion, see World Oil, Sept. 1996, pg. 56). If successful, this type of survey will be a precursor to long-offset 3-D in the area, and could have potential application in several other areas with high-velocity strata. Such areas include carbonates offshore Western Australia and salt intrusions in the Gulf of Mexico.

Airborne bathymetric survey, Australia. The survey was conducted by CGG Geoterrex-Dighem offshore Sydney in June, using a helicopter to carry an external sensor system. Similar to a highly sophisticated metal detector, measurements from the sensor are interpreted in terms of the electrical conductivity of the seawater and seabed. The latter can provide information about sediment types.

The survey will be compared to existing bathymetry that used traditional sonar. CGG conducted the bathymetric study for the Defense Science and Technology Organization.

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