SEG-D Revision 3.0 Proposal SEG Technical Standards Committee

SEG Field Tape Standards SEG Field Tape Standards History 1967 SEG-A & SEG-B SEG-C 1972 SEG-D Rev 0 1979 Rev 1 1994 Rev 2 1996 SEG-D, Rev 2.1 SEG Field Tape Standards 2006

Why now? The 2006 2.1 revision was specifically designed as a targeted upgrade to support very high capacity tapes. 3.0 was promised in the 2.1 standard to follow soon afterwards and deal with major overhaul and/or upgrades.

Why us? Jill Lewis (Troika International) — Earns living transferring & transcribing data Stewart A. Levin (Halliburton Energy Services) — ProMAX™ SEG-D Input support & upgrades Rune Hagelund (WesternGeco) — Umpteen years acquisition software experience Barry D. Barrs (ExxonMobil) — Navigation and positioning expertise

SEG-D issues driving 3.0 An explosion in data being stored in vendor-specific headers driven by the need for smooth transfer between acqusition & QC/processing Multicomponent surveys Higher sampling rates/non-power-of-2 ratios Beyond 24-bit sensor sensitivity Continuous passive monitoring Only non-record format is long byte stream— cumbersome for QC and transcription

SEG-D opportunities driving 3.0 Nonseismic data? Positioning standards coordination Using web documents for dynamic information Manufacturer list Media types and parameters API organization codes Guidance recommendations and clarifications Errata and translations Format validation utilities

Overview of revision 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

Overview of revision 3.0 proposal Increased flexibility Header blocks tagged to allow shot specific (attached to general header) or trace specific information Flexible sample rates, 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

New features in revision 3.0 proposal Logical numbering of traces/source points extended to handle all operation types Line number Point number Point index Group index Depth index Reshoot index

New features in revision 3.0 proposal Support for complex shooting schemes Multiple source initiations per shot record Multiple sources firing simultaneously Support for complex source configurations Traces and measurements for sources and parts of sources Align SEG-D with SPS standard and/or SEG-Y revision 1 positioning support

New features in revision 3.0 proposal Standardizing storage of common survey information Vessel/crew identification Survey area name Client identification Job identification Line identification (Record set ID)‏ Size of record, data, and header explicit in General Header

New features in revision 3.0 proposal 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

Sample rate / timestamp Sample rate 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

New features in revision 3.0 proposal 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

New features in revision 3.0 proposal 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

New features in revision 3.0 proposal 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)‏

New features in revision 3.0 proposal Line number -> Record set number To be usable for all types of operation Only 3 General Header blocks required in rev 3.0 Everything else optional

Header size extensions Channel set 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)‏

Trace size Traces can be 2147 seconds long Negative start times allowed Extended recording mode allows up to 140,735,340 seconds (1628 days) of data to be stored in one record

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

Questions, Concerns and Suggestions? Volunteers always wanted We’re taking names Multicomponent standards Downhole acquisition support Metadata additions (temperature, wave height, …) Opinions too  We’re taking notes