WO2001092917A2 - Station complexe de reception sismique continue - Google Patents

Station complexe de reception sismique continue Download PDF

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Publication number
WO2001092917A2
WO2001092917A2 PCT/US2001/016858 US0116858W WO0192917A2 WO 2001092917 A2 WO2001092917 A2 WO 2001092917A2 US 0116858 W US0116858 W US 0116858W WO 0192917 A2 WO0192917 A2 WO 0192917A2
Authority
WO
WIPO (PCT)
Prior art keywords
film
cable
recited
acoustic energy
compressible material
Prior art date
Application number
PCT/US2001/016858
Other languages
English (en)
Other versions
WO2001092917A3 (fr
Inventor
Loran Ambs
Ricky Workman
Original Assignee
Westerngeco Seismic Holdings Ltd.
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 Westerngeco Seismic Holdings Ltd. filed Critical Westerngeco Seismic Holdings Ltd.
Priority to AU2001264927A priority Critical patent/AU2001264927A1/en
Publication of WO2001092917A2 publication Critical patent/WO2001092917A2/fr
Publication of WO2001092917A3 publication Critical patent/WO2001092917A3/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
    • G01V1/16—Receiving elements for seismic signals; Arrangements or adaptations of receiving elements
    • G01V1/20—Arrangements of receiving elements, e.g. geophone pattern
    • G01V1/201—Constructional details of seismic cables, e.g. streamers
    • G01V1/208—Constructional details of seismic cables, e.g. streamers having a continuous structure

Definitions

  • the present invention relates to the field of hydrophone receivers in marine seismic operations. More particularly, the invention relates to a continuous seismic receiver array for reducing undesirable noise as the seismic data is collected.
  • Seismic cables and associated receiver elements are towed in the water behind marine seismic vessels or are laid on the seafloor.
  • Acoustic energy sources such as air guns generate energy for penetrating subsurface geologic formations
  • the cables include hydrophones, geophones, or a combination of both for detecting energy reflected from the subsurface formations.
  • the cables typically comprise hydrophone or geophone sub-arrays, electrical conductors, fiber optic conductors for digital telemetry, sensor wiring, and buoyancy material.
  • internal fill material provides buoyancy to overcome the relatively heavy internal components of the cable to make the streamer cable neutrally buoyant in water.
  • a flexible jacket surrounds the seismic cable exterior to reduce frictional drag through the water, to prevent water intrusion, and to resist damage to the electrical conductors, buoyancy billets and other components.
  • Each streamer cable is circular in cross-section, is approximately two inches in diameter, and is smooth along its length.
  • Acoustic signals are typically recorded from groups or point sensors connected together to form a sub-array.
  • Each sub-array typically comprises fourteen individual sensors, and the sub-array centers are typically spaced at 12.5 meter intervals along the cable. The sensors are electrically grouped into sub-arrays to enhance the desired signal and to reduce undesirable noise.
  • Towed, fluid-filled streamers are susceptible to noise referred to as "bulge wave” energy.
  • the fill fluid is excited by streamer vibration modes and generates pressure waves transmitted longitudinally in the internal fluid which interferes with the seismic energy detected by the hydrophones.
  • Streamer cables are also susceptible to "vibration energy” noise propagated by the strength members and the outer jacket as the streamer is towed through the water, and to "flow” noise (also known as turbulent boundary layer noise) caused by the streamer movement through the water.
  • Newly developed solid streamers contain electrical, fiber optic, and strength members in a core cable surrounded by solid flotation material.
  • the overall diameter of such cables typically exceeds two inches.
  • Such streamers are not susceptible to bulge wave noise energy because no internal fluid is contained within the streamer.
  • such cables are still susceptible to vibration energy noise and to turbulent flow.
  • sensors such as piezoelectric crystal hydrophones comprise a sensor isolated from the central core by a sensor carrier. Such sensors are still subject to turbulent flow noise.
  • United States Patent No. 4,789,971 to Powers et al. (1988) disclosed an acoustic hydrophone formed with polyvinylidene fluoride (PVDF). An array of multiple hydrophones was placed in front of a projector.
  • Another acoustic sensor was disclosed in United States Patent No. 5,361,240 to Pearce (1994) wherein a flexible piezoelectric film was wrapped several times around a mandrel. A hollow space between the film and the mandrel provided a pressure compensation chamber to permit activation of the film.
  • Another acoustic sensor was disclosed in United States Patent No. 5,774,423 to Pearce et al.
  • Seismic vessels typically tow multiple streamers to collect data from a swath during each vessel pass. Multiple streamers increase the weight and volume of equipment stored, deployed, and retrieved by a seismic vessel.
  • the system should reduce noise, should be inexpensive, and should be easy to store, deploy, and retrieve.
  • the present invention provides a system for detecting acoustic energy in marine seismic operations.
  • the system comprises a cable, a piezoelectric film disposed about a radial dimension of the cable wherein the film-covered area extends longitudinally along the cable for a selected distance, and a connector engaged with the film for detecting electric signals produced by the mechanical stresses produced in the film.
  • a compressible material adjacent the film permits displacement of the film in response to acoustic pressure impinging upon the film.
  • the compressible material can comprise a liquid, a cellular foam, or a flotation member.
  • An exterior jacket can surround the cable and the compressible material can be positioned between the film and the jacket.
  • a second piezoelectric film can be disposed about a radial dimension of the cable to partially overlap the first film.
  • Figure 1 illustrates a cable having one or more wires and a compressible medium in contact with a pressure sensitive film.
  • Figure 2 illustrates pressure sensitive film partially around a cable.
  • Figure 3 illustrates overlapping pressure sensitive films.
  • Figure 4 illustrates a pressure sensitive film integrated within a foam.
  • Figure 5 illustrates a foam on the exterior surface of pressure sensitive film.
  • Figure 6 illustrates a cable co-linear with a sub-array.
  • Figure 7 illustrates two layers of film oriented in opposite directions to provide cancellation signals.
  • the invention provides an improved system for detecting reflected seismic energy signals in a marine environment.
  • the terms “streamer,” “cable,” “bottom cable,” and “streamer cable” are used interchangeably as describing a structure for supporting a piezoelectric film.
  • cable 10 can comprise wires 12 for providing strength and for transmitting electric power, fiber optic signals, and electric signals.
  • a flotation member such as foam 14 is positioned around wire 12, and the density or volume of foam 14 can be selected so that cable 10 is neutrally, positively, or negatively buoyant in the water.
  • Sub-array 16 is wrapped around foam 14 to detect marine seismic energy. Instead of multiple, individual sensors used in conventional sensors, sub-array 16 is formed with a pressure sensitive material such as piezoelectric film 18.
  • Film 18 is very thin and does not substantially expand the circumference of cable 10.
  • film 18 can be formed with different materials, one suitable material having good acoustic transductance characteristics for seismic operations comprises polyvinylidene fluoride ("PVDF").
  • PVDF polyvinylidene fluoride
  • a stress applied to film 18 with a solid backing will respond to deformation in the thickness dimension and is proportional to the product of piezo-stress constant (thickness), thickness and pressure. If film 18 is stretched over an aperture backed with a compliant backing such as foam 14 and is attached to rigid edges of the aperture, the signal generated by the pressure induced stress is proportional to the product of the piezo-stress constant (length), length of aperture and pressure.
  • the length of the compliant backed film 18 is more than three times the thickness, the signal produced by a compliant backed film is greater than that of a solid backed film when exposed to the same pressure. For this reason, a band of piezo-film wrapped about a compliant inner core produces a significantly larger signal than the same material wrapped about a solid core.
  • turbulent flow noise is substantially reduced because such noise is averaged over a relatively large sub-array length.
  • the high density of sensors improves rejection of incoherent noise, and the long length of the sensor further improves the rejection of in-line incoherent noise.
  • sub-array 16 is formed by a single element, linear array with a single PVDF sheet.
  • a connector such as electric leads 20 are attached to film 18 and are attached to signal conditioner 22 connected to data processor 24. Although only two leads 20 are illustrated, multiple leads (positive and negative) can be attached to different portions of film 18. Leads 20 provide a means for communicating electric signals produced by film 18 to electronic components for further processing.
  • Signal conditioner 22 provides signal conditioning, filtering and amplification.
  • Processor 24 can collect data from one long line-array 16 or can collect data from multiple line- arrays positioned along the length of cable 10. Processor 24 can perform ' different tasks such as A-D conversion, data stacking, noise filtering and data storage.
  • film 18 wraps around the circumference of cable 10.
  • film 18 can wrap partially around cable 10 as shown in Figure 2.
  • line- array 16 can overlap line-arrays 26 and 28 as illustrated in Figure 3.
  • data from overlapping line-arrays can be combined or manipulated during data processing to emphasize signal reception from selected directions and reduce noise and other undesirable signals.
  • film 18 can be
  • film 18 can be formed on or within cable 10 in a seamless manner having no perceptible seams.
  • film 18 would operate as a single, unbroken sensor extending over all or a selected length of cable 10.
  • film 18 is shown in contact with foam 14, film 18 could be integrated within foam 14 as shown in Figure 4 during manufacture of cable 10 to provide uniform movement in response to seismic energy waves, to provide attenuation for vibration noise, and to provide a protective sheath against external forces.
  • foam 14 is illustrated as comprising the compressible material
  • foam 14 can be replaced by or used in cooperation with another material such as plastic, gel, liquid such as oil, or another moveable substance.
  • the purpose of such compressible material in contact with film 18 is to permit movement of film 18 in response to marine seismic energy.
  • Such compressible material is preferably consistent in response to external stimulation so that deflection and performance of film 18 is consistent.
  • Plastic, gel, foam, oil, or another moveable substance 30 can be placed on the outside of film 18 as shown in Figure 5 instead of on the inside. If desired, outer jacket 32 can be placed exterior of moveable substance 30 to provide an outer protective sheath for cable 10.
  • Figure 6 illustrates another embodiment of the invention wherein cable 10 is located adjacent to line-array comprising film 32.
  • This embodiment of the invention facilitates replacement or repair of various components without requiring disassembly of the entire system.
  • cable 10 and film 32 are illustrated as having co-linear longitudinal axes, cable 10 or film 32 could be wrapped or otherwise oriented proximate to the other in different configurations.
  • This invention provides a marine seismic sensor having a surface area or spatial extent substantially larger than prior art sensors.
  • the length of film 18 preferably extends at least four times longer than the radial diameter of cable 10.
  • the large surface area permits turbulent flow noise to be averaged over a larger area, significantly reducing the impact of such noise on collected data.
  • This unique feature of the invention permits the diameter of cable 10 to be reduced, thereby reducing material cost, weight, and volume of cable 10 while preserving or enhancing noise performance of cable 10.
  • Vibration energy noise is attenuated not only by the length and continuum nature of film 18 but also by the attenuating properties of the compressible medium such as foam 14 or other compressive material within cable 10.
  • the amount of size reduction depends on the orientation of film 18 within cable 10, and on the amount of turbulent flow noise generated by the exterior of cable 10.
  • Piezoelectric films produce a voltage when strained in any one of the three axes. In addition to producing an electric signal when a film is deformed by a pressure wave, the film produces a signal when stretched.
  • Film used as an acoustic pressure sensor will produce an unwanted signal when the sub-array is stretched by stretching of the cable or longitudinal waves transmitted along the cable. This interfering signal can be reduced or eliminated by combination of film elements into the sub-array and appropriate combination of electrical signals generated from the film elements.
  • a piezoelectric film may produce either a positive or negative electric signal when compressed to a smaller diameter.
  • the undesired effect of signals produced by longitudinal stretching of cylindrical film sensors could be removed by forming the sub-array of two layers of piezoelectric film where one produces a positive signal when compressed and the other produces an equal but negative signal. Both elements produce the same magnitude and polarity when deformed along the longitudinal direction. When the output of the two elements are electrically subtracted, the signal due to radial compression would be enhanced and the signal due to longitudinal deformation, such as mechanical noise propagated in the longitudinal cable direction, would be cancelled.
  • Figure 7 illustrates film layer 34 is wrapped around cable 10, and film layer 36 is wrapped around film layer 34. Film layers 34 and ' 36 are oriented opposite or in different directions to produce a desired electric response to accomplish the function described above.

Abstract

L'invention concerne un système de détection d'énergie acoustique utilisé au cours d'opérations sismiques marines. Un film piézoélectrique continu est placé dans un câble afin de détecter l'énergie d'une source acoustique marine réfléchie et réfractée à partir de formations géologiques souterraines. Le câble peut être fixe par rapport au fond marin ou peut être remorqué par un engin sismique dans l'eau. Le film est positionné par rapport au câble de façon à être adjacent à une matière de compression. Lorsque l'énergie sismique entre en contact avec le film, la matière de compression permet le déplacement du film qui peut être détecté et converti en signal électrique. Le traitement ultérieur des signaux permet d'obtenir des informations représentant les formations géologiques souterraines, et le système réduit sensiblement les bruits indésirables contenus dans ces signaux.
PCT/US2001/016858 2000-05-31 2001-05-24 Station complexe de reception sismique continue WO2001092917A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001264927A AU2001264927A1 (en) 2000-05-31 2001-05-24 Continuous seismic receiver array

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US58444000A 2000-05-31 2000-05-31
US09/584,440 2000-05-31

Publications (2)

Publication Number Publication Date
WO2001092917A2 true WO2001092917A2 (fr) 2001-12-06
WO2001092917A3 WO2001092917A3 (fr) 2002-06-06

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AU (1) AU2001264927A1 (fr)
WO (1) WO2001092917A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114455001A (zh) * 2021-12-20 2022-05-10 宜昌测试技术研究所 一种用于拖缆的粘贴式的导流机构

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4040044A (en) * 1976-08-30 1977-08-02 Gte Sylvania Incorporated Dual line electret transducer
US4695988A (en) * 1984-09-12 1987-09-22 Ngk Spark Plug Co. Ltd. Underwater piezoelectric arrangement
US4918666A (en) * 1987-12-30 1990-04-17 Institut Francais Du Petrole Tubular piezo-electric sensor with high sensitivity
US5204843A (en) * 1990-06-29 1993-04-20 Institut Francais Du Petrole Integrated reception system of great length for sensing acoustic waves
US5251183A (en) * 1992-07-08 1993-10-05 Mcconnell Joseph R Apparatus and method for marine seismic surveying utilizing adaptive signal processing
US5275885A (en) * 1988-12-19 1994-01-04 Ngk Spark Plug Co., Ltd. Piezoelectric cable
FR2765065A1 (fr) * 1997-06-20 1998-12-24 Thomson Marconi Sonar Sas Procede de soustraction de bruit pour antenne acoustique lineaire remorquee

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4040044A (en) * 1976-08-30 1977-08-02 Gte Sylvania Incorporated Dual line electret transducer
US4695988A (en) * 1984-09-12 1987-09-22 Ngk Spark Plug Co. Ltd. Underwater piezoelectric arrangement
US4918666A (en) * 1987-12-30 1990-04-17 Institut Francais Du Petrole Tubular piezo-electric sensor with high sensitivity
US5275885A (en) * 1988-12-19 1994-01-04 Ngk Spark Plug Co., Ltd. Piezoelectric cable
US5204843A (en) * 1990-06-29 1993-04-20 Institut Francais Du Petrole Integrated reception system of great length for sensing acoustic waves
US5251183A (en) * 1992-07-08 1993-10-05 Mcconnell Joseph R Apparatus and method for marine seismic surveying utilizing adaptive signal processing
FR2765065A1 (fr) * 1997-06-20 1998-12-24 Thomson Marconi Sonar Sas Procede de soustraction de bruit pour antenne acoustique lineaire remorquee

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114455001A (zh) * 2021-12-20 2022-05-10 宜昌测试技术研究所 一种用于拖缆的粘贴式的导流机构
CN114455001B (zh) * 2021-12-20 2023-06-27 宜昌测试技术研究所 一种用于拖缆的粘贴式的导流机构

Also Published As

Publication number Publication date
AU2001264927A1 (en) 2001-12-11
WO2001092917A3 (fr) 2002-06-06

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