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`When a geophysicist speaks
`about pre—stacl< data, they are
`
`usually talking about a particular
`class of gather. A gather is a
`collection of seismic traces which
`share some common geometric
`attribute. The term gather usually
`refers to a common depth point
`(CDP) or common mid—point (CMP)
`
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`gather. Gathers are sorted from
`.
`.
`.
`field records in order to examine the dependence of
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`amplitude, signalznoise, moveout, frequency content,
`phase, and other attributes that are important for data
`
`Wh t" AVO—f'
`dl
`a '5
`“en y
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` processing?
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`Sep 21, 2015 .
`Ma” Ha"
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`processing and imaging.
`http://www.agilegeosciencecom/biog/2011/9/14/g-is-for-gather.miFGS
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`WeSternGecO V‘
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`The hack is back:
`1
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`1/7
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)
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`

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`9/30/2015
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`G is for Gather — Agile
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`Common shot or receiver gather: Basic quality
`
`October
`
`Sep 7, 2015 - Matt Hall
`
`ledlll HEW SKIIIS Ill
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`l7+l8
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`New Orleans
`
`"L'‘‘'‘'*‘‘'“‘'‘
`l-lOWtO QC 8 Seismic
`~='":"'
`volume
`mm Aug 21’ 2015 V
`Matt Hall
`
`1"
`
`~_
`
`Introducing Bruges
`Aug 5, 2015 .
`Evan Bianco
`
`.._u-
`
`On answering
`questions
`Jul 30, 20l5 -
`Matt Hall
`
`assessment tools in field acquistion. When the traces of the
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`gather come from a single shot and many receivers, it is
`_
`.
`.
`called a common shot gather. A single receiver with many
`shots is called a common receiver gather. It is very easy to
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`inspect traces in these displays for bad receivers or bad
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`shots.
`
`Common shot
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`lal
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`Common receiver
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`Common offset
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`Common midpoint
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`Common depth point
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`W H
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`W
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`Common midpoint gather,
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`CMP: The stereotypical gather:
`
`traces are sorted by surface
`
`On asking questions
`Jul 28‘ 2015 .
`
`F?
`
`' Matt Hall
`
`geometry to approximate a
`
`single reflection point in the
`
`earth. Data from several shots
`and receivers are combined into
`
`Q Search
`
`a single gather. The traces are
`sorted by offset in order to
`
`Image: gamut.to.it CC—
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`perform velocity analysis for
`
`BY—NC—ND
`
`data processing and hyperbolic
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`moveout correction. Only shot—receiver geometry is
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`required to construct this type of gather.
`
`Common depth point gather, CDP: A more sophisticated
`collection of traces that takes dipping reflector geometry
`other subsurface properties into account. CDPs can be
`stacked to produce a structure stack, and could be used
`for AVO work, though most authors recommend using
`image gathers or ClPs [see the update below for d
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`September 2015
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`August 2015
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`July 2015
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`June 2015
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`May 2015
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`April 2015
`March 2015
`Febmaw 2015
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`January 2015
`December 2014
`November 2014
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`description of C/Ps]. A priori information about the
`
`October 2014
`
`subsurface, usually a velocity model, must be applied with
`September 2014
`"“""’“““”-39"e9e°s°'e"°°-°°"‘”"°9’2°‘"9"“’9"S'*°"9a*“°'“Ties Exhibit 2047 WesternGeco v. PGS (IPR2015-00313)”
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)
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`9/30/2015
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`G is for Gather — Agile
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`the shot receiver geometry in order to construct this type
`
`of gather. [This paragraph has been edited to reflect the
`
`update be/ow].
`
`Com mon
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`Common azimuth
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`Variable azimuth
`
`offset
`
`gather,
`
`COFF:
`
`Used for
`
`surface
`
`
`
`because it
`
`basic quality
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`,a,
`
`connol
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`approximates a structural section. Since all the traces are at
`
`the same offset, it is also sometimes used in AVO analysis;
`
`one can quickly inspect the approximate spatial extent of a
`
`candidate AVO anomaly. lfthe near offset trace is used for
`
`each shot, this is called a brute stack.
`
`August 2014
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`July 2014
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`June 2014
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`May 2014
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`April 2014
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`March 2014
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`February 2014
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`January 2014
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`December 2013
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`November 2013
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`October 2013
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`September 2013
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`August 2013
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`July 2013
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`June 2013
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`May 2013
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`April 2013
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`March 2013
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`Variable azimuth gather: If the offset between source and
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`February 2013
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`receiver is constant, but the azimuth is varied, the gather
`
`can be used to study variations in travel—time anisotropy
`
`from the presence of elliptical stress fields or reservoir
`
`fracturing. The fast and slow traveltime directions can be
`
`mapped from the sinsoidal curve. It can also be used as a
`
`pre—stacl< data quality indicator.
`
`Check out the wiki page for more information. Are there
`
`any gather types or applications that we have missed?
`
`Find ot/7erA to Z posts
`
`Update on 2011-10-17 14:19 by Evan Bianco
`
`Gijs Vermeer sent Agile* an email a few weeks ago with
`
`some helpful comments about this post. It is worth re-
`
`stating that common shot. common receiver. common
`http://www.agi|egeoscience.com/blog/2011/9/14/g-is-for-gather.htrIyGS
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`January 2013
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`December 2012
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`November 2012
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`October 2012
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`September 2012
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`August 2012
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`July 2012
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`June 2012
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`May 2012
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`April 2012
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`March 2012
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`February 2012
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`January 2012
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`December 2011
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`November 2011
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`fWn+n|»-‘Aw ')f'\‘l1
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`WeSternGecO V‘
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`1
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)
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`9/30/2015
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`Gis for Gather—Agi|e
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`-_u_...U _..u_ --......c.. -..-_, ,,......-.. .,--..-., --......-..
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`\JLLUL)C'| AU ll
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`offset, and common midpoint gathers are wholly defined by
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`the surface layout of sources and receivers. CDP gathers,
`on the other hand, require knowledge of the subsurface.
`
`Common midpoint
`rrir.p: r1
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`CMP gone wrong Common depth point
`
`
`
`rr~l'4~-:lir.rr.-‘-\-""'i--.._
`WM
`
`fIa1 fl“.'f|EC!I3-f
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`cl-no-rigroflecior
`
`dim:-no rerledor
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`As shown by this drawing, the CMP method doesn't work
`
`for dipping reflectors because the reflection point smears
`
`along the reflector. But if we know something about the
`velocities in the earth, we can compute the surface
`
`geometry needed to image a depth point—the common
`depth point.
`
`Common image point or CIP gathers it turns out are not as
`easy to draw. They result from the migration—or imaging—
`
`process. Like the CDP gather, this process uses subsurface
`velocity information, but C|Ps cannot be constructed with a
`simple collection of traces. As Gijs says "each trace in a
`CIP gather is the result of an imaging process that includes
`_
`tt
`"
`man in u
`races.
`y
`p
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`We'll award a covetable prize to anyone that can draw a
`
`convincing representation of an image gather!
`
`O
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`9
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`September 2011
`August 2011
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`July 2011
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`June 2011
`May 2011
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`April 2011
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`February 2011
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`January 2011
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`December 2010
`November 2010
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`@kwmkunkS on Twmer
`
` M tt H II
`
`a
`a
`Geocomputing!
`
`-
`
`:-
`
`
`
`httpsz//tco/qnBmXUpGK
`7 hours ago
`
`M tt H II
`a
`a
`Streak ONO! A” Sweaty
`now"
`http://t.co/bXwyWG94ut
`18 hours ago
`
`Matt Hall
`
`Not a bad view from the
`
`office this morning...
`
`#NovaScotia
`
`http://t.co/Ed.JhcqcZw><
`A day ago
`
`< FOLLOW THE SEG CONFERE
`
`AVO* IS FREE! >
`
`http://www.agi|egeoscience.com/biog/2011/9/14/g-is-for-gather.htrIyGS
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`WeSternGecO V‘
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`1 3)4/7
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)
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`

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`9/30/2015
`
`G is for Gather — Agile
`
`Comments (6)
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`
`Scott Dalferes 4 years ago
`
`Well done. Will you be at the SEG next week?
`
`evan 4 years ago
`
`Scott,
`
`Thanks, yes Matt and I both will be at the SEG
`
`conference. Looking forward to it. Hope to see you
`
`there!
`
`Aaron Stanton 4years ago
`
`Don't forget about cross spreads and common
`http://www.agi|egeoscience.com/biog/2011/9/14/g-is-for-gather.ht@GS
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`WeSternGeCO V
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)
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`9/30/2015
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`G is for Gather — Agile
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`offset vectors!
`
`Cheers,
`
`Aaron
`
`eVan 4 years ago
`
`@Aaron,
`
`It's funny we had another reader suggest the same
`
`thing yesterday, along with a few other refinements.
`
`So that's great. Yours is certainly a point worth
`
`making: cross spreads and common offset vectors
`
`are single fold 3D equivalents to the 2D common
`
`shot and common receiver diagrams I have shown
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`above. Those are certainly going to be a little
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`trickier to draw, so I better get on it :)
`
`Thanks for the comment.
`
`Hasan 3 years ago
`
`is it acceptable to use some diagram above for my
`
`final project?
`
`eVan 3 years ago
`
`@Hasan,
`
`Glad you like the figures. As long as you give
`
`attribution to us and the website, no problem. This
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`work is licensed under creative commons
`
`agreement. In case you occassionally need a
`
`refresher on the symbols:
`
`http://creativecommons.org/licenses/
`
`http://www.agilegéosciencecom/biog/2011/9/14/g;is-for-gather.htTyGS Exhibit" 2047 WeSternGecO V. PGS (IPR2015_00313)6fl
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)
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`9/30/2015
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`G is for Gather — Agile
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`Also you can go to subsun‘wil<i.org and search for
`
`Gather. You will find more content and editable SVG
`
`files if you wish.
`
`I will follow up with you in an email. Have fun and let
`
`me know how it goes.
`
`9‘f|30>>°
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`© 2015 Agile Geoscience Ltd - PO Box 336, Mahone Bay NS BOJ 2E0, Canada - +1.902.980.013O -
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`http://www.agi|egeoscience.com/biog/2011/9/14/g-is-for-gather.ht@GS
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`WeSternGeCO V.
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`PGS Exhibit 2047, WesternGeco v. PGS (IPR2015-00313)