SEG Y Standard And UTIG additions

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SEG Y Standard AndUTIG additions
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Seismic Database Description

• Seismic data in database uses the following SEG Y
  format
• The reel identification header consists of
  3600 bytes
• EBCDIC section describes the data from a line of
  shot points -3200 bytes
• The binary coded section describes information
  common to the seismic data on the reel 400
  bytes
• This reel identification header is ignored
• The seismic data record
• Each trace data block consists of a fixed
  240-byte trace identification header followed by
  the seismic trace data

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Block-diagram
byte 1 . . EBCDIC header . byte 3200
byte 1 . . Trace header . byte 240
Reel identification header
byte 241 . . Trace data . byte N
byte 3201 . . Binary header . byte 3600
. .
.
byte 1 . . Trace header . byte 240
. .
.
Seismic data record
byte 241 . . Trace data . byte N
byte 1 . . Trace header . byte 240
byte 241 . . Trace data . byte N
byte 1 . . Trace header . byte 240
byte 241 . . Trace data . byte N
EOF
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Description of Trace Identification Header
Entries Required by UTIG

• Byte number Description
• 912 Original field record number (used if
  value in bytes 17-20 is non-positive)
• 1316 Trace number within the original field
  record.
• 1720 Shot point (surface position of shot)
• 2124 CDP ensemble number
• 2528 Trace number within the CDP ensemble
  (each ensemble starts with trace 1)
• 2930 Trace identification code if greater
  than 1 is reset to 1, otherwise is reset to 0
• 3740 Offset - distance from source point to
  receiver group
• 4144 Receiver group elevation Z
• 4548 Source elevation Z
• 6970 Scaler to be applied to elevations in
  bytes 4148 to give the real value
• 7172 Scaler to be applied to coordinates in
  bytes 7388 to give the real value
• 7376 Source coordinate X
• 7780 Source coordinate Y
• 8184 Receiver group coordinate X
• 8588 Receiver group coordinate Y

Entries in orange font can be used for sorting
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Description of Trace Identification Header
Entries Required by UTIG (continued)

• Byte number Description
• 109110 Delay recording time
• 115116 Number of samples in this trace
• 117118 Sample interval in µs for this trace
• 157158 Year data recorded
• 159160 Day of the year
• 161162 Hour of day (24 hour clock)
• 163164 Minute of the hour
• 165166 Second of the minute
• 193196 Repeat survey number
  (year10000month100day)
• 197198 Line number
• 231234 Receiver (trace) number in this array
• 235236 Component number
• 237238 Array number
• ALL OTHER BYTES IN THIS HEADER ARE IGNORED

Entries in yellow font are used for sorting
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Required Sorting

• Program should be capable of retrieving all
  the traces given the following information
• Survey number
• Line number (first, last increment)
• Shot point number (or CDP number) (first, last
  increment)
• Source position
• Array number (or max and min numbers)
• Receiver group number (first, last increment)
• Receiver group position
• Recorded component number (or max and min number)

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Diagram
Survey
Line
Sp (or CDP) source position
Array
Traces
Receiver group receiver group position
Component
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Shot point/CDP
Sp (or CDP) position
Array
Receiver group position
Receiver group position
Receiver group position
Array
Receiver group position
Receiver group position
Receiver group position
Array
Receiver group position
Receiver group position
Receiver group position
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Typical 3D layouts
1 component recording
Array 1 (top) 1-component surface detectors
Source
Array 2 (bottom) 4-component bottom detectors
4 component recording
Array 3 3-component down-hole detectors
3 component recording