Sigsbee2A Public Distribution. Created Sept. 25, 2001 by the SMAART Joint Venture.
The data contained within this distribution remains the property of SMAART whose members
are BHP Petroleum, BP, Chevron Petroleum Technology Company and Texaco. Anyone may
use the data to test any type of algorithm and to publish the results under the conditions
described in the Sigsbee2A Data Release Agreement.
The contents of this tape is a tar file containing a seismic data file (SEG-Y), ascii text file (txt),
the data release agreement (pdf) and graphics files (Jpeg and Powerpoint).
The files (and their size) contained within this distribution are:
5,233
29,696
13,913
952,751,760
16,149,444
10,762,452
16,149,444
98,305
104,285
140,179
136,071
168,321
1,425,940
sigsbee2a_readme.txt (this file in ascii text format)
sigsbee2a_readme.doc (this file in Word format)
sigsbee2a_release_agreement.pdf (pdf file with the data release terms)
sigsbee2a_nfs.segy (shot gathers)
sigsbee2a_stratigraphy.segy (true stratigraphic interval velocity)
sigsbee2a_migration_velocity.segy (migration interval velocity)
sigsbee2a_reflection_coefficients.segy (P-wave reflectivity)
sigsbee2a_migration_velocity.jpg
sigsbee2a_stratigraphy.jpg
sigsbee2a_reflection_coefficients.jpg
sigsbee2a_stratigraphy_index.jpg (stratigraphy qualitative)
sigsbee2a_zero_offset.jpg (zero offset trace section)
sigsbee2a.ppt (Powerpoint file including jpg’s)
The data file sigsbee2a_nfs.segy is in IBM Real format. All other floating point data are in IEEE
Real format.
Information: True stratigraphic interval velocity model and P-wave reflectivity
Number of velocity traces = 3201 from X= 10000 to X= 90000 ft
Velocity trace increment = 25 ft.
Velocity depth sample = 25 ft
Total Depth of Model: 30000 ft
Salt Velocity: 14800 ft/sec
Sediment Velocity: V = Vo + kZ; Vo = 5000 ft/sec; Z = depth below water bottom;
V = 5000 + 0.3 (Z - Z_seafloor).
The reflection interfaces are all the result of velocity contrasts, which fluctuate within +/300 ft/sec relative to V(z) linear velocity function. This produces reflectivities up to about +/3%, enough to produce reflections, but not sufficient to destroy the basic gradient macro model
which is used in depth migration.
Information: Migration interval velocity model
Number of velocity traces = 2133 from X= 10025 to X= 89975 ft
Velocity trace increment = 37.5 ft.
Velocity depth sample = 25 ft
Total Depth of Model: 30000 ft
Sigsbee2A Computation Information:
Acoustic Finite Difference (constant density)
Grid size: dX = dZ = 25 feet
Dominant Frequency ~ 20 Hz, Max frequency = 40 Hz.
Source and receiver ghosts included in the recorded wavelet (even though there is no free
surface).
Single source point, 75-foot receiver array.
56 ms negative static shift applied, which positions the maximum wavelet amplitude at the
theoretical arrival time (wavelet no longer causal).
In order to test the effects of illumination on imaging, this is a relatively noise-free model:
No free surface (absorbing top surface) - therefore no free-surface multiples.
Dim seafloor - therefore weak interbeds between salt and seafloor.
Sigsbee2a Acquisition Information:
Number of shots = 500, from X = 10925 to X = 85775 ft
FFID = 499-0
Shot interval = 150 ft
Minimum offset = 0 ft
Maximum offset = 26025 ft (end-on)
Max. number of offsets per shot = 348
Max. number of traces in cmp gather = 87
Receiver interval = 75 ft
CMP interval = 37.5 ft
CDP range = 25-2021(1)
Record length = 12 seconds
Sample rate = 8 ms
Source depth below sea-level = Receiver depth below sea-level = 25 ft
Remark: Source is pulling the cable. Starting at the far right side of the model
(FFID #499) the source location walks through the cable until the full cable
length is reached (26025 ft).
Imaging Suggestions
Maximum depth to image = 31000 ft
Depth step ~ 25 ft (this was the resolution on the input seismic modeling finite difference grid)
Aperture: 25000 ft on each side of an image point should be sufficient.
For support on reading the data from the distribution media, contact Steve Darnell, Oil Data Inc.,
1888 Stebbins Drive, Houston, TX 77043, Phone: 713-461-7178, Fax: 713-461-2788,
darnell@oildata.com
To contact SMAART about the Sigsbee2A dataset, send email to smaart2-admin@chevron.com.
If you are submitting a paper using this dataset, SMAART prefers to receive copies of the papers
in digital form. If the file is too large for email (>5MB), we will provide you with instructions
on how to ftp the file. Postal mail can be sent to: Imaging Technology Unit Manager, Bldg. D1
Attn: SMAARTJV, Chevron Petroleum Technology Co., P. O. Box 6019, San Ramon, CA
94583-0719
The Smaart JV hope you will find the data useful for current and future research.