EP2997400A1 - Spectrum splitting - Google Patents
Spectrum splittingInfo
- Publication number
- EP2997400A1 EP2997400A1 EP13753447.5A EP13753447A EP2997400A1 EP 2997400 A1 EP2997400 A1 EP 2997400A1 EP 13753447 A EP13753447 A EP 13753447A EP 2997400 A1 EP2997400 A1 EP 2997400A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- frequencies
- acquiring
- low
- frequency
- spatial sampling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/003—Seismic data acquisition in general, e.g. survey design
Definitions
- Source and receiver intervals are typically chosen to ensure that the maximum expected frequencies are not aliased.
- the present invention considers Vibroseis, dynamite, surface impulsive, TZ and OBC survey examples and shows that acquiring the data to meet the spatial sampling requirement for low, mid and high frequencies (by acquiring coarse, medium and fine acquisition grids respectively and layering these during processing) can result in reduced cost and/or higher quality surveys.
- Sampling the wavefield spatially is one of the most important criteria for successful seismic imaging.
- One of the parameters used in determining spatial sampling is the maximum frequency required from the data.
- the spatial sampling grid could potentially be considerably coarser.
- 25m linear surface sampling were deemed necessary for an upper frequency of, for instance, 80Hz in a particular survey
- a 400m linear surface sampling would satisfy the same sampling criteria if the maximum desired frequency were to be 5Hz.
- This is a ratio of 16: 1 for a 2D survey and 256: 1 for a 3D survey.
- low frequencies may be acquired using considerably lower source and receiver densities, probably about 2 orders of magnitude lower for 3D surveys.
- receiver line intervals are almost always much further apart than the interval required to properly sample the signal and the source intervals generally perform this function in the orthogonal direction.
- the receiver line interval relates to the receiver interval along the line it may not be necessary to have a specific low frequency sensor on every receiver line. This could provide significant savings in the deployment of low frequency sensors should they be deemed to be desirable.
- Vibroseis is the easiest source to which to apply the concept of the present invention, as the source frequency can be tailored on an individual basis to the requirements of the survey. For nonlimiting example, if the spatial sampling requirement of the highest expected frequencies is determined to require a VP interval of 20m, the mid-frequencies 40m, and the low frequencies 80m, then the sweeps could be tailored such that the high frequencies are swept every 20m, the mid frequencies and high frequencies are swept every second VP (40m), and the full sweep is performed (lows to highs) every fourth VP.
- the benefit gained by not sweeping the entire frequency range at each VP can be translated into either a cost saving (by reducing the sweep time on some VPs), or an improvement in quality, by devoting more time in sweeping the higher frequencies.
- the frequency spectrum generated by buried dynamite charges depends upon the depth of the charge below the surface, the size of the charge, and the Poisson's ratio of the formation around the charge.
- Shallow pattern shots are typically less expensive to acquire than deep-hole dynamite yet they can be lacking in lower frequencies due to the smaller charge sizes employed, and have an effect of a surface ghost.
- a fine grid of shallow pattern holes necessary to meet the high-frequency survey sampling requirements could be supplemented with a coarser grid of shot holes designed to generate more of the very low frequencies lacking in the shallow patterns.
- the coarser grid comprising the low-frequency component of the signal does not need to be the same source type as the higher- frequency grid.
- a surface impulsive source could be used to add low frequencies attenuated by the source ghost from buried charges.
- the predominant seismic source is the airgun array.
- the requirements for generating low frequency signals diverge from the requirements for the minimum and high frequencies, and could benefit from being separated into different acquisition grids.
- the source array In order to generate a low frequency signal, the source array should be comprised of larger volume guns, or the guns should be discharged at a higher air pressure than standard.
- the total array volume will need to be increased, or the working pressure will need to be raised.
- the compressors will need to do significantly more work in order to supply an array tuned for low frequencies than that required for the mid and high frequencies. Again, as air supply is often the limiting factor, especially in shallow water surveys, acquiring the lower frequency components on a coarser grid will reduce the air supply requirement for the survey.
- Another source for marine acquisition is the marine vibrator, and the bandwidth splitting concept can be applied.
- the hardware used to acquire the low frequency component of certain marine vibrators is different from that required to produce the mid and high frequencies. In such cases the low frequency source could be acquired separately, and on a coarser grid than the high frequency assembly.
Abstract
Description
Claims
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US2013/041527 WO2014185928A1 (en) | 2013-05-17 | 2013-05-17 | Spectrum splitting |
Publications (1)
Publication Number | Publication Date |
---|---|
EP2997400A1 true EP2997400A1 (en) | 2016-03-23 |
Family
ID=51898737
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP13753447.5A Withdrawn EP2997400A1 (en) | 2013-05-17 | 2013-05-17 | Spectrum splitting |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP2997400A1 (en) |
MX (1) | MX2014010768A (en) |
WO (1) | WO2014185928A1 (en) |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7835223B2 (en) * | 2006-12-21 | 2010-11-16 | Westerngeco L.L.C. | Removing noise from seismic data obtained from towed seismic sensors |
WO2011156494A2 (en) * | 2010-06-09 | 2011-12-15 | Conocophillips Company | Marine seismic data acquisition using designed non-uniform streamer spacing |
-
2013
- 2013-05-17 EP EP13753447.5A patent/EP2997400A1/en not_active Withdrawn
- 2013-05-17 WO PCT/US2013/041527 patent/WO2014185928A1/en active Application Filing
- 2013-05-17 MX MX2014010768A patent/MX2014010768A/en unknown
Non-Patent Citations (2)
Title |
---|
None * |
See also references of WO2014185928A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO2014185928A1 (en) | 2014-11-20 |
MX2014010768A (en) | 2015-10-12 |
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Legal Events
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Owner name: GEOKINETICS USA, INC. |
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