SEGD rev 3.0 proposal - PowerPoint PPT Presentation

rune hagelund westerngeco stewart a levin halliburton n.
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SEGD rev 3.0 proposal PowerPoint Presentation
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SEGD rev 3.0 proposal

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  1. Rune Hagelund, WesternGeco Stewart A. Levin, Halliburton SEGD rev 3.0 proposal

  2. Overview of rev 3.0 proposal • All features discussed at SEG New Orleans have been implemented • With a few additions • SEGD Tape Label, General Header 1 and Demux Trace Header left as is (with a few exceptions) • Be an efficient format for transferring information between acquisition and QC/processing • SEGD is not a processing format • More space for user-defined header blocks

  3. Overview of rev 3.0 proposal • Increased flexibility • Header blocks tagged to allow shot specific (attached to general header) or trace specific information • Flexible samplerates, header sizes, reclength etc. • Increased robustness • Tagged header blocks • Size of shot/data in General Header • Simplified encoding/decoding • No complex datatypes, using 4byte float, int etc • Explicit values (ex. #samples/trace)‏ • No dependencies between header blocks • Additional functionality

  4. New functionality in rev 3.0 • Positions can be tagged to all traces/equipment • Multiple positions (in space and time)‏ • Format TBD by pos group • Support for multi-component data • Node number, trace grouping, orientation header • New General Trailer format • Flexible, allows any data-block to be appended • Standardized edits can be appended to General Trailer • Allows easy addition of edits post-acquisition • 8068: IEEE 8 byte samples

  5. New functionality in rev 3.0 • Supporting complex shooting schemes • Multiple source efforts per shot record • Multiple sources firing simultaneously • Supporting complex source configurations • Traces and measurements for sources and parts of sources • Align SEGD with SPS

  6. New functionality in rev 3.0 • All measurements now properly tagged with accurate, absolute timestamp (if available)‏ • Positions, traces, shot, etc. • All header sizes extended • More room for acquisition system defined blocks • Existing trace ext hdr blocks may be used.... • ...but remember to use correct block tag • Standardizing storage of SEGD • One header block spanning multiple tape blocks • A trace spanning multiple tape blocks • Fixed/variable block devices • Disk storage • Transfer across network

  7. New functionality in rev 3.0 • Standardizing storage of common survey information • Vessel/crew identification • Survey area name • Client identification • Job identification • Line identification (Record set identification)‏ • Size of record, data, and header explicit in General Header

  8. New functionality in rev 3.0 • Logical numbering of traces/source points extended to handle all operation types • Line number • Point number • Point index • Group index • Depth index • Reshoot index

  9. New functionality in rev 3.0 • More sensor types/channel types explicitly supported • Wind, depth, reference signals, source measurements etc. • Sensor sensitivity value stored per channel • Convert to actual physical unit • Support non-voltage measurements

  10. New functionality in rev 3.0 • Table Of Contents file • Stored at end (or beginning) of tape • Lists all SEGD records on a tape • Enable fast access to data • May be stored on disk (to simplify data mgt)‏

  11. New functionality in rev 3.0 • Line number -> Record set number • To be usable for all types of operation • Only 3 General Header blocks required in rev 3 • Everything else optional

  12. Header sizes • Channelset header block 96 bytes • Header block sizes • General header - 65536 blocks (2 MB)‏ • Channelset header – 65535 blocks (~6MB) • Skew blocks – 65535 blocks (~2MB)‏ • Extended header – 16777215 blocks (~512MB)‏ • External header - 16777215 blocks (~512MB)‏ • Trace Header Extension – 255 blocks (8160 bytes)‏ • General Trailer – 4294967295 blocks (~128GB)‏

  13. Samplerate / timestamp • Sample rates steps of 1 microsecs • No longer a base scan rate • Dominant Sample interval used for backwards compatibility • Timestamp – counting microsecs since 6 jan 1980 (GPS epoch)‏ • 8 byte integer • Negative timestamps allowed • 292471 years range

  14. Trace size • Traces can be 2147 secs long • Negative start times allowed • Extended recording mode allows up to 140735340 secs (1628 days) of data to be stored in one record

  15. Filters • Extended filter definitions • Frequencies and slopes are IEEE floats (4 bytes) • Filter type • Filter delay