WO2021013829A1 - Procédé et système d'étude sismique - Google Patents

Procédé et système d'étude sismique Download PDF

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Publication number
WO2021013829A1
WO2021013829A1 PCT/EP2020/070544 EP2020070544W WO2021013829A1 WO 2021013829 A1 WO2021013829 A1 WO 2021013829A1 EP 2020070544 W EP2020070544 W EP 2020070544W WO 2021013829 A1 WO2021013829 A1 WO 2021013829A1
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WO
WIPO (PCT)
Prior art keywords
seismic
cable
cables
towed
das
Prior art date
Application number
PCT/EP2020/070544
Other languages
English (en)
Inventor
Tore Kjos
Original Assignee
Tore Kjos
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Tore Kjos filed Critical Tore Kjos
Publication of WO2021013829A1 publication Critical patent/WO2021013829A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/38—Seismology; Seismic or acoustic prospecting or detecting specially adapted for water-covered areas
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • G01V1/22—Transmitting seismic signals to recording or processing apparatus
    • G01V1/226—Optoseismic systems

Definitions

  • the invention is within the technical field of seismic prospecting, and more specifically relates to a method and system for seismic surveying which combines VSP, in particular HybridVSP with towed seismic survey.
  • DAS distributed acoustic sensing
  • HybridVSP is an operation described in patent application WO 2016/202373. Dense seismic with short cables is illuminates reservoirs in difficult fields as described as a method to obtain accurate seismic. Due to the short cables it is easy to maneuver, and such an operation is well suited for circle or elliptical surveying. HybridVSP is particularly well suited to illuminate reservoirs below salt formations where the salt formation obstructs imaging due to density and poor signals.
  • HybridVSP uses a combination of DAS and 3C signals.
  • the DAS signals are collected in the fibre optic cable and can be collected with signal distance as low as 25 cm. This will result in many signals, which provides good and accurate imaging of the reservoir.
  • DAS signals are generally weak signal, but it has been shown that it is possible to process the signals, including noise extraction. A weak complete signal provides the exact same information as a strong signal. Processing is therefore an important issue to make the DAS marine system, near bottom system or subsea system cable work.
  • the distance between two 1C acquisitions in traditional cables is about 3m for dense acquisitions. With similar dense shooting, this results in good and accurate acquisition. Combined with HybridVSP acquisition, this provides very good data that can provide accurate reservoir data in places where the surface seismic methods cannot be used.
  • the acquisition path may comprise a circle or ellipse shaped shot line.
  • the advantage of a circle or ellipse is that you avoid lost time for turn and avoids problems related to getting back into the line. Such paths require that the cables are short or that the shooting takes place without cables.
  • the shoot pattern can be a circle or ellipse with a distance down to 100 m between each line of the circle/ellipse.
  • This firing pattern is then the same as on a HybridVSP and both of the surveys can be combined in the same survey. This provides great cost savings.
  • the number of signals increases accordingly and the accuracy and quality of the seismic increases accordingly.
  • hybridVSP is used as example, but it should be noted that also other kinds of VSP operations may be used as alternative or in combination with hybridVSP.
  • the object of the invention is to provide a method and a system for seismic surveying that increases effectivity, provides improved resolution and decreases surveying costs.
  • a method for seismic surveying comprises performing a towed seismic survey by towing seismic cables and seismic sources from a vessel, performing a Vertical Seismic Profiling (VSP) simultaneously to the towed seismic survey and using the same seismic sources.
  • VSP Vertical Seismic Profiling
  • the towed seismic survey can be a surface survey, a near bottom seismic survey or a seabed seismic survey.
  • the seismic cables are DAS cables.
  • the DAS cables may comprise at least two fibre optic cables arranged in parallel and connected at their ends.
  • the DAS cable comprises a main cable and at least one sub cable, where the sub cables are arranged substantially perpendicular to the main cable.
  • the angle between the sub cable and the main cable may be substantially perpendicular to the each other. In one embodiment is the angle between the sub cable and the main cable such that it is ensured that the angle between the incident seismic signal and the sub cable is less than 90 degrees, and in some embodiments less than 80 degrees.
  • the sub cable may comprise weights and/or control fins.
  • FIG 1 illustrates parts of prior art seismic acquisition operations
  • Figure 2 illustrates a traditional cable being towed.
  • Figure 3 illustrates a DAS cable being towed near surface
  • Figure 4 illustrates a DAS cable being towed near bottom
  • Figure 5 illustrates a DAS cable used at the seabed
  • Figure 1 illustrates examples of a vessel and DAS cable in a well of a typical HybridVSP acquisition.
  • the acquisition path may comprise a circle or ellipse shaped shot line.
  • Figure la shows the device on a vessel 10. Sources 11 are towed by the vessel 10, and the distance between the sources are determined by the spreaders 13.
  • Figure lb shows the arrangement of HybridVSP in a well 16, using a DAS cable 15.
  • the arrows represent the path of the acoustic signals from the acoustic sources, being reflected and received by the various seismic sensors.
  • FIG. 2 illustrates a traditional prior art cable 20 which can be used in the method and system according to the invention.
  • This cable is being towed at a depth of 3 to 5 m below the sea surface 21.
  • the cable 20 is for example 100 m long.
  • An air gun/source 24 is arranged at or near the surface 21 by means of a float 23.
  • the air gun/seismic source 24 emits an acoustic signal which are reflected from the sea bed and/or the ground below the seabed.
  • seismic sensors 22 making the acquisitions when the acoustic signal is reflected towards the surface.
  • the seismic acquisitions are recorded as seismic raw data for later processing.
  • the traditional cable 20 can be used during a HybridVSP survey, by towing cables together with the shooting for the HybridVSP.
  • two different surveys are performed simultaneously, providing significantly increased data acquisition and better resolution in the seismic images resulting from the surveys, without the costs for one of the surveys increasing proportionally.
  • the innovative idea is therefore to run two surveying simultaneously. Therefore, with HybridVSP and dense cables, quality, number of signals, reservoir illumination and accuracy can be increased.
  • the number of signals is an important parameter.
  • the number of signals may increase by a factor 20 compared to the typical amount of data used in a standard VSP processing. The operational costs can thus be reduced to substantially, possibly be halved.
  • FIG. 3 illustrates an example of a new type of DAS cable 30 that only comprises fibre optic cables used in surface seismic surveys. These are two continuous, fibre optic cables 37,38 connected at their ends to achieve the double length of cable for receiving independent signals. This leads to a substantially improved amount of data that can be recorded by the cable. Since DAS signals require that the incoming, reflected signals 39 have an incident angle different from perpendicular to the cable, the cables in the surface cable have sub-cables 35 that are arranged substantially vertically to the direction of travel.
  • the sub cables can for example be 5m long, but can in other embodiments have lengths between 3-5m.
  • the angle a must be less than 80 degrees.
  • the signals come along the vertical cables and can be captured as DAS signals, for examples every 25 cm along the cable.
  • the vertical cable is equipped with weights and/or control fins so that a stable geometric shape is established.
  • the cable can also comprise positioning instruments so that accurate coordinates can be provided for each shot.
  • the main cable is equipped with spreaders so that the sources have a required distance, for example 50 m, to each side and can be used for flip/flop shooting.
  • Figure 4 shows a similar cable 30 as in figure 3, used in a near bottom seismic survey.
  • the cable 30 is in this embodiment towed at a distance of 3-20 meters above the seabed 46.
  • This system may be operated as a close to the bottom system, i.e. it can be towed with 3 to 5 knots, capturing 3C directional signals as well as S signals. This provides significant cost savings compared to traditional subsea seismic.
  • the DAS cable described in figure 3 and 4 may also be used at the seabed as illustrated in figure 5.
  • the main cable 30 is arranged in the sand/seabed 46.
  • the vessel may only tow the seismic source.
  • the cable 30 may also comprise 3C satellites.
  • the vertical part 35 comprise or is connected to buoyancy elements, so that the vertical part 35 can be extended to for example 100m. With DAS signals this can give 400 signals per vertical cable. If a vertical cable 35 is arranged at the main cable 30 with a distance of 20m, this can give 2000 signals per 100 m.
  • These signals will also comprise directional information, and will be able to replace more than 500 3C satellites on the seabed or 3 3C satellites per m.
  • the seabed cable even if it is horizontal, can receive signals from shots far from the cable, ie. the angle a of the incident signal is less than 80 degrees.

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  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geophysics (AREA)
  • Oceanography (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

L'invention concerne un procédé de levé sismique comprenant la réalisation d'un levé sismique remorquée par remorquage de câbles sismiques et de sources sismiques depuis un navire et la réalisation d'un profilage sismique vertical (PSV) simultanément au levé sismique remorqué et en utilisant les mêmes sources sismiques.
PCT/EP2020/070544 2019-07-22 2020-07-21 Procédé et système d'étude sismique WO2021013829A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO20190913 2019-07-22
NO20190913 2019-07-22

Publications (1)

Publication Number Publication Date
WO2021013829A1 true WO2021013829A1 (fr) 2021-01-28

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2020/070544 WO2021013829A1 (fr) 2019-07-22 2020-07-21 Procédé et système d'étude sismique

Country Status (1)

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WO (1) WO2021013829A1 (fr)

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4970697A (en) * 1989-10-06 1990-11-13 Amoco Corporation Vertical marine seismic array
US20120227504A1 (en) * 2011-03-08 2012-09-13 US Seismic Systems, Inc. Fiber optic acoustic sensor arrays and systems, and methods of fabricating the same
WO2014165219A2 (fr) * 2013-03-12 2014-10-09 Ion Geophysical Corporation Système de capteur de réseau sismique enterré
WO2014199300A2 (fr) 2013-06-10 2014-12-18 Read As Câble sismique, système et procédé pour acquérir des informations concernant des incidents de vibration sismique, micro-sismique et mécanique dans un puits
US20160011301A1 (en) * 2014-07-14 2016-01-14 US Seismic Systems, Inc. Fiber optic backscatter sensing systems and methods of operating the same
CN105510977A (zh) * 2015-12-31 2016-04-20 中国海洋大学 拖曳式海洋地震勘探垂直缆数据采集系统
WO2016202373A1 (fr) 2015-06-17 2016-12-22 Read As Dispositif capteur et procédé pour applications sismiques de trou de forage
US20170260846A1 (en) * 2016-03-09 2017-09-14 Conocophillips Company Measuring downhole temperature by combining das/dts data
CN105738951B (zh) * 2016-05-06 2018-02-06 广州海洋地质调查局 多节点obs垂直缆地震采集系统
US20180164456A1 (en) * 2015-06-12 2018-06-14 Shell Oil Company Marine seismic surveying
CN109765620A (zh) * 2019-02-20 2019-05-17 自然资源部第二海洋研究所 近底拖曳式随机接收电缆地震数据采集系统与方法
US20190195066A1 (en) * 2017-06-01 2019-06-27 Saudi Arabain Oil Company Detecting sub-terranean structures

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4970697A (en) * 1989-10-06 1990-11-13 Amoco Corporation Vertical marine seismic array
US20120227504A1 (en) * 2011-03-08 2012-09-13 US Seismic Systems, Inc. Fiber optic acoustic sensor arrays and systems, and methods of fabricating the same
WO2014165219A2 (fr) * 2013-03-12 2014-10-09 Ion Geophysical Corporation Système de capteur de réseau sismique enterré
WO2014199300A2 (fr) 2013-06-10 2014-12-18 Read As Câble sismique, système et procédé pour acquérir des informations concernant des incidents de vibration sismique, micro-sismique et mécanique dans un puits
US20160011301A1 (en) * 2014-07-14 2016-01-14 US Seismic Systems, Inc. Fiber optic backscatter sensing systems and methods of operating the same
US20180164456A1 (en) * 2015-06-12 2018-06-14 Shell Oil Company Marine seismic surveying
WO2016202373A1 (fr) 2015-06-17 2016-12-22 Read As Dispositif capteur et procédé pour applications sismiques de trou de forage
CN105510977A (zh) * 2015-12-31 2016-04-20 中国海洋大学 拖曳式海洋地震勘探垂直缆数据采集系统
US20170260846A1 (en) * 2016-03-09 2017-09-14 Conocophillips Company Measuring downhole temperature by combining das/dts data
CN105738951B (zh) * 2016-05-06 2018-02-06 广州海洋地质调查局 多节点obs垂直缆地震采集系统
US20190195066A1 (en) * 2017-06-01 2019-06-27 Saudi Arabain Oil Company Detecting sub-terranean structures
CN109765620A (zh) * 2019-02-20 2019-05-17 自然资源部第二海洋研究所 近底拖曳式随机接收电缆地震数据采集系统与方法

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