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`PATENT DATE
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`A~J~LICATION NO.
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`0 The term of this patent
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`0 The term of this patent shall
`not extend beyond the expiration date GREGORY J. TOATLaY. JR..
`PRIMARY EXAMINER
`of U.S Patent. No.
`
`Total Claims
`
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`
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`}
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`NOTICE OF ALLOWANCE MAILED
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`
`(Legal Instruments Examiner)
`
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`
`ISSU,BATCH NUMBER
`\
`\
`'
`
`WARNING:
`'-
`The Information disclosed herein may be restricted. Unauthorized disclosure may be prohibited by the United States Code Title 35, Sections 122, 181 and 368.
`Possession outside the U.S. Patent & Trademark Office Is restricted to authorized employees and contractors only.
`
`Form PT0-436A
`(Rev. 6/99)
`
`FILED WITH: D DISK (CRF) D FICHE D CD-ROM
`
`(Attached In pocket on right Inside flap)
`
`PGS Exhibit 2028, pg. 1
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`\U~IIIIIIIr
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`9~&78289 .
`
`' JC997 U.S. PTO
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`... _ j'CONTENTS
`
`I
`
`. ~.
`
`I
`l ~-
`
`Date Received
`(Incl. C. of M.)
`or
`Date Mailed
`
`jl
`INITIALs~
`
`JUN 12 0145
`
`Date Received
`(Incl. C. of M.}/
`or
`'•
`Date Mailed
`
`/
`
`1. Application
`
`\
`
`papers.
`
`42.
`
`43.
`
`44.
`
`45 •..
`
`1iJ
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`48.
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`22 . - - - - - - - - , - - - -
`23 . ...__ __ _ __ _ _
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`26 • ....,....---------,.----
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`68. - - - - - - - - - --~\~_
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`70. •
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`71.
`72. - - - - - - - - - - - · -
`73.
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`74.
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`75.
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`76.
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`'~-·
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`36. - - - - - - - - - - - ' -
`37. __ ______ - - -
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`77.
`78. __ __ ___ _ ----,---
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`38. __ __ _ ___ - - -
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`80. __ ____ __ --,-----
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`40. ___ ___ __ - - -
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`81. ________ - - -
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`41. ________ - - -
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`82. _ __ __ ___ - - -
`
`PGS Exhibit 2028, pg. 2
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`UNITED STATES PATENT AND ThADEMARK OFFICE
`
`Bib Data Sheet
`
`llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll ~ 1111
`l\ FILING DAlE
`
`\
`
`l,
`
`05/30/2001
`
`SERIAL NUMBER
`09/870,289
`
`\RULE
`
`CLASS
`367
`
`"
`
`•
`
`· •
`
`..
`
`~~t ·
`\
`APPLICANTS
`. Robbert Jasper de ~ok, Houston, TX;
`**CONTINUING DATA"" 'l'""""""""""""**"**""""~·~
`\
`•• FOREIGN APPLICATIO~ •••••••••••••••••••• ~~
`IF REQUIRED, FOREIGN FI~NG LICENSE GRANTED
`. J
`** 07/30/2001
`CJ yes
`. no CJ Met after
`35 USC 119 (a-d) conditions CJ y~~
`~·~ \
`7"J:J.
`Examir/31'§ Si lrtlll~
`
`Page 1 of 1
`
`COMMISSIONER FOR PATEN'S
`UNITED STATES PATENT AND TRADEMARK OFFICE
`WASHING"TON, D.C. 202:11
`www.uspto.gov
`
`CONFIRMATION NO. 7316
`
`GROUP ART UNIT
`2857
`
`ATTORNEY
`DOCKET NO.
`594-23060-US
`
`SHEETS
`DRAWING
`7
`
`TOTAL
`CLAIMS
`30
`
`INDEPENDENT
`CLAIMS
`3
`
`'·
`
`Foreign Priority claimed
`
`0
`
`met
`Verified and
`~cknowledged
`~DDRESS
`24923
`
`l_
`
`Initials
`
`'-./v \
`
`STATE OR
`COUNTRY
`TX
`
`~'
`\
`FEES: Authority has bee~iven in Paper
`
`FILING FEE
`RECEIVED No.
`No.
`1020
`
`to charge/c~dit DEPOSIT ACCOUNT
`for following\
`\
`
`'i,
`
`TITLE
`Method for acquiring and processing of ata from two or more simultaneously fired sources
`jCJ All Fees
`jCJ 1.16 Fees (Filing)
`Cl 1.17 Fees (Processing Ext. of
`time)
`jCJ 1.18 Fees (Issue)
`jCJ Other
`jCJ credit
`
`I
`I
`
`1
`j
`
`I
`I
`I
`
`-
`
`~~,.,...,,..,.,.,,....,""""',.,...
`
`PGS Exhibit 2028, pg. 3
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`'<
`
`\
`
`PATENT APPLICATION SERIAL NO. of.- g 7 O.Q_ 1$' 1_
`
`U.S. DEPARTMENT OF COMMERCE
`PATENT AND TRADEMARK OFFICE
`FEE RECORD SHEET
`
`06/0412001 tiAHID1 00000010 501720
`01 FC:101
`710.00 CH
`02 FC:103
`180.00CH
`
`09870289
`
`PT0-1556
`(5/87)
`
`•u.S. GPO: 2000-468-987/39595
`
`PGS Exhibit 2028, pg. 4
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`PTO/SB/05 (08-00)
`. ~d for use through 10/31/2002. OMB 0651-0032
`Ar...
`r.1
`. ~
`.
`.
`.
`U.S. Patent and Trad.emark Office; U.S. DEPARTMENT OF COMMERCE
`Please type a plus Sign (+) Inside this l:iox --.. LJJ
`Under the Paperwork Reduction Act of 1995, no persons are required to respond to a collection of information unless it displays a valid OMB control number.
`
`UTILITY
`PATENT APPLICATION
`TRANSMITTAL
`
`A
`
`Docket No. 594-23060-US
`
`Robbert Jasper de Kok
`
`Method for Acquiring and Processing of Data From ..
`
`1.0
`2.0
`3.0
`
`Fee Transmittal Form (e.g., PTO/SB/17)
`(Submit an original and a duplicate for fee processing)
`Applicant claims small entity status.
`See 37 CFR 1.27.
`[Total Pages C2Z] 1
`Specification
`(preferred arrangement set forth below)
`- Descriptive title of the invention
`- Cross Reference to Related Applications
`- Statement Regarding Fed sponsored R & D
`- Reference to sequence listing, a table,
`or a computer program listing appendix
`- Background of the Invention
`- Brief Summary of the Invention
`- Brief Description of the Drawings (if filed)
`- Detailed Description
`- Claim(s)
`-Abstract of the Disclosure
`
`Drawing(s) (35 U.S. C. 113)
`
`b.
`
`(for continuation/divisional with Box 17 completed)
`
`4. 0
`[ Total Sheets CLJ 1
`[ Total Pages [=::J 1
`5. Oath or Declaration
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`D Copy from a prior application (37 CFR 1.63 (d))
`i. 0 DELETION OF INVENTOR(S)
`
`Assistant Commissioner for Patents
`ADDRESS TO:
`Box Patent Application
`DC 20231
`7. 0 CD-ROM or CD-R in duplicate, large table or
`Computer Program (Appendix)
`8. Nucleotide and/or Amino Acid Sequence Submission
`(if applicable, all necessary)
`
`a. D Computer Readable Form (CRF)
`
`b. Specification Sequence Listing on:
`i. 0 CD-ROM or CD-R (2 copies); or
`i i.D paper
`c. 0 Statements verifying identity of above copies
`
`Assignment Papers (cover sheet & document(s))
`
`37 CFR 3.73(b) Statement 0 Power of
`
`Attorney
`(when there is an assignee)
`English Translation Document (if applicable)
`
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`
`Citations
`
`Information Disclosure
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`(Should be specifically itemized)
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`(if foreign priority is claimed)
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`
`Signed statement attached deleting inventor(s)
`named in the prior application, see 37 CFR
`1.63(d)(2) and 1.33(b).
`6.0
`Application Data Sheet See 37 CFR 1.76
`17. If a CONTINUING APPLICATION, check appropriate box, and supply the requisite information below and in a preliminary amendment,
`or in an Application Data Sheet under 37 CFR 1. 76:
`D Continuation D Divisional D Continuation-in-part(CIP)
`
`of priorapplicationNo.: __________ _
`
`Prior application information:
`
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`
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`
`For CONTINUATION OR DIVISIONAL APPS only: The entire disclosure of the prior application, from which an oath or declaration is supplied under
`Box 5b, is considered a part of the disclosure of the accompanying continuation or divisional application and Is hereby Incorporated by reference.
`The Incorporation
`be relied upon when a portion has been inadvertently omitted from the submitted application parts.
`
`0
`
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`
`or 0
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`Correspondence address below
`
`Name
`
`Kaushik P. Sriram
`
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`
`Kaushik P. Sriram
`
`Signature
`Burden Hour Statement: This form is' estimated to take 0.2 hours to complete. Time will vary depending upon the needs of the individual case. Any comments 'b.(l
`the amount of time you are required to complete this form should be sent to the Chief Information Officer, U.S. Patent and Trademark Office, Washington, D'<
`20231. DO NOT SEND FEES OR COMPLETED FORMS TO THIS ADDRESS. SEND TO: Assistant Commissioner for Patents, Box Patent Application,
`Washington, DC 20231.
`
`PGS Exhibit 2028, pg. 5
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`EXPRESS MAIL CERTIFICATE
`"EXPRESS MAIL" LABEL No: Q<b@...~\0'3 Db'-\- US
`Date of Deposit: May~, 2001
`I hereby certify that this paper or fee is being deposited with the United States Postal
`Service "Express Mail Post Office to Addressee" service under 37 CFR 1.10 on the date
`indicated above, addressed to: Commissioner of Patents and Trademarks, Washington,
`D.C. 20231.
`
`Beth Pearson-Naul
`
`APPLICATION FOR UNITED STATES UTILITY PATENT
`
`FOR
`
`METHOD FOR ACQUIRING AND PROCESSING OF DATA FROM TWO OR
`MORE SIMULTANEOUSLY FIRED SOURCES
`
`Inventors: Robbert Jasper de Kok
`5807 Song Ridge Court
`Houston, Texas 77041
`
`Assignee:
`
`WesternGeco, L.L.C.
`lOOOl.Richmond
`Houston, Texas 77042
`
`llllllllllllllllll
`24923
`
`PATENT .TRADEMARK OFFICE
`
`..
`
`PGS Exhibit 2028, pg. 6
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`METHOD FOR ACQUIRING AND PROCESSING OF DATA FROM TWO OR
`MORE SIMULTANEOUSLY FIRED SOURCES
`
`5
`
`FIELD OF THE INVENTION
`
`This invention relates to the field of geophysical prospecting and, more
`
`particularly, to a method for generating seismic energy for seismic surveys.
`
`BACKGROUND OF THE INVENTION
`
`~:J
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`
`In the oil and gas industry, geophysical prospecting techniques are commonly
`
`~1:...'::1.
`
`used to aid in the search for and evaluation of subterranean hydrocarbon deposits.
`
`Generally, a seismic energy source is used to generate a seismic signal that propagates
`
`15
`
`into the earth an~ is at least partially reflected by subsurface seismic reflectors (i.e.,
`
`interfaces between underground formations having different acoustic impedances). The
`
`reflections are recorded by seismic detectors located at or near the surface of the earth, in
`
`a body of water, or at known depths in boreholes, and the resulting seismic data may be
`
`processed to yield information relating to the location of the subsurface reflectors and the
`
`20
`
`physical properties of the subsurface formations.
`
`594-23060US
`
`.,
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`PGS Exhibit 2028, pg. 7
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`U.S. Patent 3,744,021 to Todd discloses the firing oflow energy shots for shallow,
`
`high resolution profiling in combination with high energy shots for deep seismic
`
`profiling. The method only allowed for a small overlap of shallow and deep profiling
`
`5
`
`recording cycles, merely maximizing the number of shots in a given period of time while
`
`minimizing interference. U.S. Patent 5,973,995 to Walker and Lindtjeorn discloses a
`
`method for simultaneous recording of deep and shallow profiling data. Their main
`
`objective was to use different cables in one and the same shooting configuration.
`
`\J 10
`
`U.S. Patent 4,168,485 to Payton, et al, teaches a full simultaneous signal
`
`generation method. This patent implements orthogonal pseudorandom sequences for
`
`;=;
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`
`vibratory sources allowing for the separation of the source signals during the correlation
`
`~JJ
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`
`process. Experiments with pseudo random firings of airguns have also been conducted,
`
`however no global successes have been reported. Others have experimented with phase
`
`encoding of vibratory sources. Other patents attempt!ng full simultaneous signal
`
`generation include U.S. Patent 4,715,020 to Landrum and U.S. Patent 5,822,269, to Allen.
`
`The problem with these types of encoding methods is that harmonic distortion is not
`
`rejected or is only partly rejected.
`
`20
`
`U.S. Patent 4,159,463 to Silverman describes the use multiple vibrators,
`
`repeatedly vibrating at stationary locations, generating opposite polarity sweeps in
`
`594-23060US
`
`2
`
`J
`
`..
`
`PGS Exhibit 2028, pg. 8
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`encoded sequences. However, Silverman does not include the use of vibrators for firing a
`
`single shot or sweep at one set of locations while generating other polarity changing
`
`sweeps at another set of locations.
`
`5
`
`U.S. Patent 5,721,710 to Sallas teaches a generalized method for the simultaneous
`
`use of an arbitrary number of vibrators, sweeping a specified number of times in constant
`
`geometry. In this method, the separation of sources is achieved through the repeated
`
`inversion of two-dimensional (source versus shot) matrices at constant frequencies.
`
`A general limitation when using pseudo-random sequences and sweep signals is
`
`nJ
`
`the length of the energy emission, rendering the method less attractive for dynamic
`
`(marine) recording. Methods that are applicable to explosive and.implosive types of
`
`sources are limited. U.S. Patent'5,924,049 to Beasley and Chambers teaches a processing
`
`method to separate the signals from different sources when fired simultaneously from two
`
`ends of recording cable(s). The method is not suitable for the simultaneous recording of
`
`~=J
`!·"~ 15
`
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`
`signals arriving from approximately the same direction.
`
`A method disclosed by U.S. Patent 4,953,657 to Edington discloses use of a suite
`
`of time delay differences between sources. To enhance the signal from a particular source,
`
`20
`
`the corresponding signals are aligned and stacked. The contributions from the other
`
`594-23060US
`
`3
`
`..
`
`PGS Exhibit 2028, pg. 9
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`source( s) are not aligned and do not stack to full strength. The remaining undesired
`
`energy is further attenuated in the frequency domain.
`
`The high cost of seismic acquisition necessitates that compromises in the field be
`
`5
`
`made, both on land and offshore. The common practice is to acquire data at a low but still
`
`acceptable areal density of surface locations. On land both the source and the receiver
`
`deployment may be less than optimal while in the marine environment the source
`
`deployment is routinely compromised and often lower than desirable. Often, data quality
`
`seems initially acceptable for the intended purpose, such as reconnaissance, new field
`
`exploration, wildcat drilling, etc. However, when more detailed studies like hydrocarbon
`
`identification and reservoir characterization are needed at a later stage, the data quality
`
`proves insufficient. In both land and marine environments there is a compelling case for
`
`the efficient acquisition of seismic data at a denser grid of locations. The use of multiple
`
`sources firing simultaneously into the same recording system is an attractive option to
`
`l=:b 15
`
`increase the field efforts at relatively low incremental cost. Simultaneous firing is
`
`particularly economical when additional sources can easily and cheaply be deployed, such
`
`as vibrator groups on land and airgun arrays in a marine situation. Unfortunately, the
`
`separation of the information pertaining to the individual sources may be cumbersome
`
`and/or imperfect.
`
`20
`
`594-23060US
`
`4
`
`s
`
`.,
`
`PGS Exhibit 2028, pg. 10
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`It would be desirable to have a method of simultaneous shooting with impulsive
`
`sources. The present invention satisfies that need.
`
`SUMMARY OF T~E INVENTION
`
`A method of seismic surveying using a plurality of simultaneously recorded
`
`seismic energy sources. An activation sequence for each of said plurality of seismic
`
`energy sources may be determined such that energy from separate seismic source
`
`positions may be recorded simultaneously and seismic energy responsive to individual
`
`seismic sources separated into separate source records. The seismic sources are activated
`
`using an activation sequence, the recorded seismic energy in the shot recordings may be
`
`separated into source recordings responsive to individual seismic ·sources. The source
`
`records may be derived from the shot records using a combination of shot record
`
`summations, inversions and filtering.
`
`5
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`The present invention offers embodiments for simultaneous source separation
`
`applicable to both marine and land environments. One embodiment utilizes source signals
`
`coded with positive and negative polarities, but without the restriction of stationary
`
`locations and without the restriction of vibratory sources. Another embodiment utilizes
`
`20
`
`source signals with time-delays between source activation times. These embodiments
`
`achieve enhancement of the desired source energy through the alignment and combination
`
`594-23060US
`
`5
`
`•,
`
`PGS Exhibit 2028, pg. 11
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`of the coded signals. In the source discrimination process, an equal amount of data as
`
`recorded and of data, polarity changed in processing, may be used. This aspect allows that
`
`undesired source energy and distortion energy are effectively cancelled, which are
`
`advantages over the prior art.
`
`5
`
`One embodiment of the present invention described in this disclosure is based
`
`primarily on source polarity encoding, while another embodiment is based primarily on
`
`source time shift encoding. It should be noted here that in the first part of the detailed
`
`description, the source signal has been simplified to a spike representation, or in other
`
`10
`
`words it has been deconvolved for the direct source signature. This implies that the
`
`schematic data shown in the relevant figures should be convolved with the direct source
`
`signature to obtain the actual responses.
`
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`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The present invention and its advantages will be better understood by referring to
`
`20
`
`the following detailed description and the attached drawings in which:
`
`594-23060US
`
`6
`
`..
`
`PGS Exhibit 2028, pg. 12
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`FIGURE lA illustrates a downward firing source comprising two source elements.
`
`FIGURE lB illustrates an upward firing source comprising two source elements.
`
`FIGURE 2 illustrates a two source shooting geometry and simultaneous signal-coding
`
`5
`
`scheme.
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`FIGURE 3 illustrates discrimination of simultaneous sources by data processing in the
`
`FKdomain.
`
`FIGURE 4 illustrates a four source shooting geometry and simultaneous signal-coding
`
`scheme.
`
`FIGURES SA, SB and SC illustrate a source discrimination scheme for two sources.
`
`FIGURES 6A and 6B illustrate an alternate source discrimination scheme for adding a
`
`third source to the two sources of FIGURES 5.
`
`FIGURES 7 A and 7B illustrate a three-source four-shot sequence with varying
`
`amplitudes and time delays.
`
`594-23060US
`
`7
`
`.,
`
`PGS Exhibit 2028, pg. 13
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`The present invention is a method for acquiring seismic data using simultaneously
`
`activated seismic energy sources. This invention may enable seismic surveys to be
`
`5
`
`acquired more rapidly than conventional surveys. Other advantages of the invention will
`
`10
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`be readily apparent to persons skilled in the art based on the following detailed
`
`description. To the extent that the following detailed description is specific to a particular
`
`embodiment or a particular use of the invention, this is intended to be illustrative and is
`
`not to be construed as limiting the scope of the invention.
`
`Except for the seismic vibrator, changing the polarity of a seismic source has not
`
`generally been considered to be a viable option and hence polarity encoding has not been
`
`used in all seismic acquisition environments. However, in the marine situation,
`
`incorporating the negative sea surface reflection into the method can approximate a
`
`polarity-reversed impulse. Referring to a standard airgun array, the far field source
`
`signature is composed of a positive pressure pulse followed by a negative pulse from the
`
`sea surface reflection. The negative pulse, called the ghost, is time separated from the
`
`positive pulse by a time shift that may be referred to as the ghost time delay. This makes
`
`the far-field signal look like an anti-symmetric wavelet. The ratio of the constituent
`
`20
`
`positive to negative peaks can, however, be changed by using vertically staggered arrays
`
`operated in so called 'end fire' mode. By directing energy downwards or upwards, the
`
`594-23060US
`
`8
`
`..
`
`PGS Exhibit 2028, pg. 14
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`positive direct pulse or the negative reflected pulse can be enhanced respectively. The
`
`left side of Figure 1A shows a downward firing source comprised of two source
`
`elements. Time is the horizontal axis 111; depth is the vertical axis 113. The shallower
`
`source element 101 is activated at time tt. emitting energy in all directions, thereby
`
`5
`
`creating a pressure wave front. At the moment the pressure wave front arrives at the
`
`deeper source element 103, that element is activated at time t2, thereby enhancing the
`
`downward traveling signal. The activation sequence time delay is computed by
`
`determining the time difference between tt and t2, the pressure wave front travel time
`
`between source elements. The upward traveling wave fronts from the time separated
`
`sources propagate such that the wave fronts do not reinforce. The impulse responses are
`
`displayed with arbitrary amplitude 114 on the right hand side of Figure 1A, with time
`
`zero tr (reference time) chosen to correspond to the sea surface. The impulse responses at
`
`the right hand side of Figure 1A are as measured vertically below the sources, but
`
`redatumed such that time zero corresponds to the sea surface.
`
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`In the upward firing source, as depicted in Figure 1B, the guns of the deeper
`
`source element 107 fire first while the shallower guns 105 are time delayed until the
`
`upward traveling wave-front has arrived at that shallower depth level. This way the up-
`
`going wave front is enhanced. Again, on the right side of Figure 1B, the reference time
`
`20
`
`tr in the impulse response of the up-going wave front is chosen to be the sea surface.
`
`Although more than two source elements can be deployed for creating enhanced positive
`
`594-23060US
`
`9
`
`[0
`
`PGS Exhibit 2028, pg. 15
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`and negative signals, and for enhancing directionality of signals, only two are used in the
`
`illustration of Figure lA and Figure lB.
`
`Figure 2 shows the sequences of two sources firing simultaneously with polarity
`
`5
`
`coding. It should also be noted that the number of sources is not limited to two. Larger
`
`numbers of sources can be used in combination with longer source activation or coding
`
`sequences. Figure 2 shows a source vessel201 towing sources 203 and 205. A source
`
`vessel 201 may also tow a streamer containing sensors for receiving source signals, for
`
`example streamer 207. In Figure 2, Source 203 emits Sl, in which positive (P) and
`
`negative (N) polarity source signals alternate as depicted by the positive and negative
`
`polarity representation through time. 81 may correspond to the example of alternately
`
`;;l'J
`
`using a pair of source elements in the configuration shown in Figure lA with a pair of
`
`source elements in the configuration shown in Figure lB. Source 205 emits positive
`
`signals 82 only. 82 corresponds to using a pair of source elements in the configuration
`
`!~ 15
`
`shown in Figure lA. The sources may have arbitrary positions in a seismic survey, but in
`
`the example of Figure 2 they are located closely together like in a flip-flop shooting
`
`configuration.
`
`The seismic energy returned from shot records containing multiple source position
`
`20
`
`energy must be separated into source records containing energy responsive to the
`
`individual seismic sources. The separation of individual source contributions into source
`
`594-23060US
`
`10
`
`[ (
`
`PGS Exhibit 2028, pg. 16
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`~-----·---·------
`
`records (as opposed to shot records) is achieved during processing, preferably in the
`
`common mid-point (CMP) domain but any other domain where the contributions from
`
`successive shot records are present may be used. In the domain selected, a form of mixing
`
`or filtering may be applied to remove the undesired source position contribution seismic
`
`5
`
`energy. In the example of Figure 2 for instance, a two-trace mix with equal weights or a
`
`three trace running mix with weights 1/2, 1 and 112 may greatly attenuate the polarity
`
`changing signals from Source S 1. It should be noted here that all multi-trace operations
`
`such as DMO, stacking, migration, etc. have a mixing effect on the data. Thanks to the
`
`polarity changing nature of the undesired data, these multi-traces processes will also
`
`reduce undesired source contributions.
`
`In order to enhance the signal from Source S2 and attenuate signals from Source
`
`S 1, successive shots are polarity reversed during processing. Hereby signals from S 1 will
`
`become positive in polarity for all shots, while the signals from Source S2 will alternately
`
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`become positive and negative.
`
`Although data mixing can take place at various stages during processing, the
`
`preferred domain is the CMP gather where the desired data are sorted to offset and
`
`normal move-out (NMO) corrected as shown schematically on the left panel301 in
`
`20
`
`Figure 3. The first panel 301 of Figure 3 is a depiction of an NMO corrected CMP
`
`gather showing flattened reflection events Rl, R2 and R3. There are also seismic event
`
`594-23060US
`
`11
`
`•,
`
`PGS Exhibit 2028, pg. 17
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`----~--- - - - - - --~~- --------------
`
`contributions 309 from two additional sources located at the tail end of the cable, for
`
`instance sources 413 and 415 as depicted in Figure 4. The NMO corrected data are
`
`transformed to the Frequency-Wavenumber (FK) domain representation 303 where
`
`attenuation of undesired energy can take place by passing wavenumber (K) values around
`
`5
`
`the K=O axis only. Panel305 is the FK domain representation after filtering; panel307 is
`
`the CMP gather after transforming from the FK domain back to CMP containing
`
`reflection events Rl, R2 and R3 with other unwanted seismic energy suppressed or
`
`absent.
`
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`Figure 4 depicts a four source (203, 205, 413, 415) shooting arrangement with
`
`two receiver cables (407, 409). Front source 203 emits signal sequence 81 and 205 emits
`
`signal sequence 82, may be as previously shown in Figure lA and Figure lB. Source
`
`vessel 201 may also tow two streamers containing sensors for receiving source signals,
`
`for example streamers 407 and 409. Figure 4 shows two sources, 413 and 415, following
`
`~r=?: 15
`
`the streamers. Source 413 may have a signal sequence 83 as depicted in Figure 4. Two
`
`shots of one polarity, for instance positive polarity, are followed by two shots of negative
`
`polarity before two shots of positive polarity are again initiated. The signal sequence 84
`
`for another source, for instance 415, is the same as 83 except the polarity sequence is
`
`offset one step either direction compared to 83.
`
`20
`
`594-23060US
`
`12
`
`!)
`
`..
`
`PGS Exhibit 2028, pg. 18
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`In the configuration of Figure 4 the two sources 203 and 205 preceding streamers
`
`407 and 409 are relatively close to each other, and also sources 413 and 415 at the back of
`
`the streamers 407 and 409 are in relatively close proximity. As a consequence, when
`
`processing for desired front source 205, the data from undesired source 203 have move-
`
`5
`
`out that is approximately the same as that of the desired front source 205. However, the
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`corresponding energy from each front source projects at different locations in the FK
`
`domain. Because the undesired data is changing in polarity as outlined above, it has zero
`
`average amplitude and thus has no energy at K=O. Instead, the polarity swapping data
`
`represent a periodic function in X and projects onto constant K values, 311 in Figure 3,
`
`pertaining to the length of a period. Transformation back to the TX domain, after any
`
`necessary FK filtering, yields the desired data absent the undesired source contributions,
`
`for example as is shown on panel307 in Figure 3.
`
`After polarity reversing successive shot recordings during processing, this process
`
`can then be repeated for the other sources. For instance, flipping alternate records will
`
`cause signals from source 203 to be in phase and those from other sources to be out of
`
`phase. Flipping (inverting) the signals from the 3rd and 4th shot and the ih and 8th shot
`
`and so on will cause signals from source 413 to be in phase and those from the other
`
`sources to be out of phase in successive recordings. There are four separable sources
`
`20
`
`shown in the configuration of Figure 4, separable by using stacking, filtering or
`
`combinations ofboth stacking and filtering.
`
`594-23060US
`
`13
`
`•,
`
`PGS Exhibit 2028, pg. 19
`WesternGeco v. PGS (IPR2015-00309, 310, 311)
`
`

`
`Another embodiment of the present invention entails time delay encoding. The
`
`time delay encoding technique relies on programmed time delays in the field and polarity
`
`decoding in the processing center. The time shifts for encoding may be arbitrarily chosen
`
`5
`
`per source, but they should preferably be equal to the ghost time delay in the marine case.
`
`In the land case the delay should be less than the reciprocal of the maximum frequency of
`
`interest. The enhancement of data pertaining to a particular desired source is
`
`accomplished through equalizing the polarity of corresponding signal components and to
`
`align and average (mix or stack) the responses. This principle is illustrated with the
`
`10
`
`impulse response representations of Figure 5A for a marine application. The impulse
`
`response representations may be, for example, where the sea surface reflection having
`
`opposite polarity follows a primary source impulse. Here, the pnmary source is
`
`represented as a positive polarity followed by a ghost of negative polarity with a delay
`
`time. In Figure 5A (and in Figure 6 and Figure 7), only the individual source firing