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WO1985001359A1 - Source de vibrations sismiques - Google Patents

Source de vibrations sismiques Download PDF

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Publication number
WO1985001359A1
WO1985001359A1 PCT/AU1984/000173 AU8400173W WO8501359A1 WO 1985001359 A1 WO1985001359 A1 WO 1985001359A1 AU 8400173 W AU8400173 W AU 8400173W WO 8501359 A1 WO8501359 A1 WO 8501359A1
Authority
WO
WIPO (PCT)
Prior art keywords
valve member
poppet valve
vibrator
cylindrical portion
cylinder
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.)
Ceased
Application number
PCT/AU1984/000173
Other languages
English (en)
Inventor
David Brian Stewart
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Unisearch Ltd
Original Assignee
Unisearch 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 Unisearch Ltd filed Critical Unisearch Ltd
Publication of WO1985001359A1 publication Critical patent/WO1985001359A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • G01V1/02—Generating seismic energy
    • G01V1/143—Generating seismic energy using mechanical driving means, e.g. motor driven shaft
    • G01V1/155—Generating seismic energy using mechanical driving means, e.g. motor driven shaft using reciprocating masses

Definitions

  • VIBRATOR SEISMIC SOURCE This invention relates generally to improvements to seismic sources used for geophysical examination of underground strata.
  • this specification deals with a vibrator seismic source (VSS) which is powered hydraulically.
  • VSS vibrator seismic source
  • the main application of the invention described in this specification is for the generation of seismic compression and shear waves at the surface of the earth but equally the invention could be useful for generation of seismic compression and shear waves underground in mines and at the ocean bottom surface and also could be useful for generation of acoustic waves underwater for transmission through water for the purpose of sound navigation and ranging.
  • BACKGROUND ART BACKGROUND ART
  • a VSS according to the invention is powered hydraulically to take advantage of the low compressibility of hydraulic oils or other working liquids in the transfer from hydraulic energy within the VSS to wave energy in a transmitting medium, for example the earth, including mineral deposits and water.
  • the low compressibility characteristic of hydraulic oils naturally leads to simple control of an output member of the VSS which applies forces cyclically to the transmitting medium.
  • Control of the flow rate of the hydraulic oil into one end of a single acting hydraulic cylinder fitted with a slidably mounted piston in turn rigidly connected to the fijrst end of a piston rod enables control of the motion of the output member which is connected rigidly or by thrust bearing means to the second end of the piston rod.
  • VSS VSS
  • This particular application of the invention is useful in geophysical examination of coal deposits, for example in the determination of coal seam burial depth, extent of seam faulting, extent of seam parting and extent of longitudinal seam continuity all of which are important in the economics of planning and operation of coal mines.
  • This invention incorporates different design and construction and a different central principle of operation as compared to existing vibrator sources.
  • Vibroseis a trade mark of Continental Oil Company Inc.
  • the principal difference between the VSS of the present invention and the "Vibroseis” system is that the former uses a single acting hydraulic cylinder for generation of cyclic compression waves in the transmitting medium, whereas the "Vibroseis” system uses a double acting hydraulic cylinder for generation of cyclic compression waves in the transmitting medium.
  • the double acting cylinder in the "Vibroseis” system involves the use of hydraulic oil injection into two mutually inclusive ends of a double acting cylinder whereas the VSS uses hydraulic oil injection into a single end of a single acting hydraulic cylinder.
  • the present invention and the "Vibroseis" system both may be used in conjunction with a common data processing method of reflection seismology, for example, in one application of the use of the VSS according to the invention, this is the cross-correlation method of signal processing, in which for time varying swept frequency operation of a VSS according to the invention and the "Vibroseis" system a pilot signal representing cyclic compressing waves, ie. time varying swept frequency compression wave signal, ie. wave train, ie. input signal, ie. sweep, to said transmitting medium is cross-correlated against time varying signals received by geophones which sense reflections, of the input signal, from the strata.
  • a pilot signal representing cyclic compressing waves ie. time varying swept frequency compression wave signal, ie. wave train, ie. input signal, ie. sweep
  • Cross-correlation of the pilot signal and the geophone signals together with a definition of zero time of the pilot signal specifies in the time domain the location of reflectors, ie. strata in the transmitting medium.
  • This method of reflection seismology processing is based, upon the original work on radar by Klauder.
  • the present invention consists in a vibrator seismic source consisting of an output member adapted to be brought into contact with a transmitting medium and apply forces cyclically thereto, a single acting hydraulic cylinder having a piston rod therein one end of which is connected to the output member, an inlet for hydraulic liquid under pressure into the cylinder, a source of hydraulic liquid under pressure, valve means for controlling the intermittent supply of hydraulic liquid into the cylinder to apply a force to the piston and for returning hydraulic liquid for repressurisation.
  • the invention consists in a vibrator seismic source incorporating the principle of single action operation and comprising an output member whose contact area is coupled with a seismic transmitting medium, for example the earth's surface, the output member including structural stiffening means to withstand generation of compression waves or shear waves or other waves in the transmitting medium, the centroid of the output member contact area being connected rigidly or by accommodating thrust bearing means to a second end of a piston rod, the first end of the piston rod being connected rigidly to a generally cylindrical piston which co-operates and seals with the internal cylindrical surface of a vibrator cylinder whose second end is fitted with sliding bearing means for the piston rod to allow sliding and guiding of the piston rod in the direction of the common centreline of the piston and the piston rod between the extremities of the piston rod first end and the piston rod second end, the first end of the vibrator cylinder incorporating a liquid inlet port for liquid injection directly from the outlet port of flow control means whose purpose is to shape the flow rate versus real time of the liquid injection conveyed directly to
  • VSS by way of example. This detailed description illustrates the main application of the invention and also illustrates the best method of carrying out the invention for the purpose of generation of cyclic compression waves on the earth's surface. Said method of reflection seismology processing is also applicable in conjunction with the detailed description of the VSS, although this is only one of several methods of signal processing that may be used in conjunction with the
  • VSS since said swept frequency operation of the VSS is only one of several methods of operation of the VSS.
  • Fig. 1 is a partly sectioned elevation of a VSS according to the invention mounted on the rear of a vehicle.
  • Fig. 2 is a cross-sectional view on line A-A of Fig. 1 of a servo valve assembly controlling the flow of hydraulic oil, and.
  • Fig. 3 is a diagram showing the hydraulic circuit of the servo valve assembly of Fig. 2.
  • FIG. 1 shows a partly sectioned exterior arrangement drawing of a VSS according to the invention mounted at the rear of a vehicle.
  • a single acting hydraulic cylinder 1 is shown fitted internally with a slidable piston 2 connected rigidly to one end of piston rod 3.
  • the other end of piston rod 3 is connected rigidly or by a spherical thrust bearing 4 to a vibrator output member 5 in the form of an earth contact plate.
  • the piston rod 3 is guided slidably by neck bearing 6 at the lower end of the hydraulic cylinder 1.
  • hydraulic oil 7 Whilst the VSS is operating, hydraulic oil 7 is injected into the upper end of the hydraulic cylinder 1 and occupies volume 8; also whilst operating there is air 9 occupying the internal volume at the lower end of the hydraulic cylinder 1. Air is exhausted from the lower end of the hydraulic cylinder whilst hydraulic oil 7 is injected into the upper end.
  • the flow rate of hydraulic oil 7 is controlled by a servo-valve assembly 10 which is also shown in a cross-sectional view on line A-A in Fig. 2.
  • the servo-valve assembly 10 consists of two major assemblies namely a flow valve 11 and an electrohydraulic servo-valve 12.
  • the servo-valve 12 is, for example, a Moog Inc.
  • the servo-valve 12 is predominantly a flow control device whose output flow rate of hydraulic oil is proportional to electric current applied to the electromagnetic means.
  • the servo-valve is capable of operating at up to frequencies of 500 Hz and higher to give controlled flow rates of hydraulic oil 13 and 14 from a high pressure supply of hydraulic oil 15.
  • Hydraulic oil 16 exhausted from the servo-valve assembly 12, including any internal hydraulic oil leakage from the servo-valve, is returned to a separate hydraulic power supply for reuse.
  • piston 17 which is either attached rigidly to a first end of poppet valve 19 or is attached by accommodating and sealing means to that end of the poppet valve 19 whereby motion of piston 17 in the direction of the longitudinal centreline of poppet valve 19 is transferred directly to the poppet valve 19 but whereby any motion of the piston 17 at right angles to the longitudinal centreline of the poppet valve is accommodated by the accommodating and sealing means so as to allow for geometry tolerances in manufacturing whose effects are present in assembly of the flow valve 11.
  • piston 18 controls the closing motion of the poppet valve 19 by acting on piston 18 which is attached to the second end of the poppet valve 19 by means similar to those described for attachment of the piston 17 to the poppet valve 19.
  • piston 18 may be free of any mechanical attachments to poppet valve 19 and therefore the piston 18 simply contacts the second end of the poppet valve 19 as a result of hydraulic force due to hydraulic oil flow 14 acting on piston 18.
  • a helical spring 20 which maintains contact between the piston 18 and the poppet valve 19.
  • the spring 20 is also useful to keep the poppet valve 19 in sealing contact with seat 21, during periods wh en a controlled flow of hydraulic oil 14 does not exist, thereby sealing the hydraulic oil injection 7 and thus preventing hydraulic oil 7 from entering cylinder 1 during periods when output member 5 is not required to vibrate on the earth's surface.
  • Sealing of hydraulic oil injection has the important advantage that power wastage is eliminated because hydraulic oil leakage from high pressure hydraulic oil supply 22 is eliminated during periods when the output member is not required to vibrate on the earth's surface.
  • Poppet valve 19 has sliding bearing and sealing means 46 for the first end cylindrical portion and second end cylindrical portion to enable the poppet valve to slide longitudinally and seal in the body of the flow valve 11.
  • Reduced cross-sectional areas of pistons 17 and 18, which are for example one quarter of the cross-sectional area of the first and second end cylindrical portions of poppet valve 19, enable enhancement of the hydraulic oil flow rate from flow valve 11 and therefore enable increased injection 7 due to increased longitudinal displacement of poppet valve 19 from seat 21 for a given flow rate 13, provided that the high pressure hydraulic oil supply 22 is adequate.
  • Sensitive and responsive operational performance of servo-valve assembly 10 to result in the desired hydraulic oil injection into the hydraulic cylinder 1 first end is achieved through the use of feedback control, for example, using well known electronic feedback control techniques.
  • the feedback control includes a first control for the pressure difference between hydraulic oil flow 14 and hydraulic oil flow 13 to ensure, during periods whilst the ground contact plate is not required to vibrate on the earth's surface, that poppet valve 19 is in sealing contact with the seat 21 to prevent oil injection.
  • the first control involves, for example, the use of a differential pressure transducer to convert the pressure difference to an electrical signal for feedback control.
  • the first control ensures that the pressure of hydraulic oil flow 14 acting on piston 18 results in a small magnitude net force to keep poppet valve 19 in sealing contact with seat 21.
  • This first control has the added advantage of ensuring that the second stage of the servo-valve 12 is sensitive and responsive to enable initiation of cyclic compression waves in the transmitting medium.
  • the feedback control includes a second control which incorporates the use of a linear voltage displacement transducer, for example, rigidly connected to piston 17 to measure the displacement of poppet valve 19 from the seat 21.
  • the second control also incorporates the use of a transducer mounted rigidly on the ground contact plate to measure, for example, the acceleration, the velocity and the displacement of the ground contact plate while these parameters vary with time during a sweep.
  • the second control collectively may be used for feedback control of cyclic compression waves in the transmitting medium.
  • a commercially available vibrator controller manufactured by Texas Instruments Inc. is capable of such second control collectively to enable the time varying amplitude of sinusoidal compression waves in the transmitting medium to be controlled through the measurement of time varying ground contact plate acceleration and comparison of time varying ground contact plate acceleration with a desired and previously specified time varying reference sweep frequency signal generated using microprocessor based instrumentation.
  • the vibrator controller includes the use of phase compensation techniques to allow for phase differences between the time varying ground contact plate acceleration and the reference signal.
  • Fig. 1 shows a single acting hydraulic cylinder 1 with the servo-valve assembly 10 rigidly connected to the upper end of the cylinder 1.
  • This arrangement provides the shortest hydraulic oil path and the most direct hydraulic oil path for oil injection. It is advantageous to have the shortest hydraulic oil path for oil injection since this results in the highest resonant frequency when considering the hydraulic stiffness of the oil path and the associated resonating mass whether the mass is the total first mass consisting of piston 2 plus piston rod 3 plus thrust bearing 4 plus earth contact plate 5 and plus a stiffening frame 23 or whether the mass is the total second mass consisting of cylinder 1 plus servo-valve assembly 10 hydraulic oil plumbing 24 plus accumulator mountings 25 and 26 plus hydraulic accumulators 27, 28 and 29 plus hydraulic plumbing 30 plus added reaction mass 31 plus various bolted attachments 32 plus sliding means 33.
  • Hydraulic oil plumbing 24 conveys hydraulic oil to hydraulic accumulators 27 and 28 when the separate hydraulic power supply is charging the accumulators with hydraulic oil during times when the ground contact plate is not required to vibrate on the earth's surface. During times when the ground contact plate is required to vibrate on the earth's surface hydraulic oil plumbing 24 conveys a high flow rate of hydraulic oil to flow valve 11 for oil injection 7. The plumbing 24 together with accumulators 27 and 28 collectively provide the high pressure hydraulic oil supply 22.
  • the separate supply may provide a significant part of the high flow rate of hydraulic oil, though to reduce equipment costs the separate hydraulic power supply will not be large enough to provide a significant part of the high flow rate of hydraulic oil.
  • a balance is needed in choos ing the size of the separate hydraulic power supply so that the accumulators 27 and 28 may be recharged quickly enough to minimise the time between sweeps.
  • the accumulators 27, 28 and a further accumulator 29 are the usual commercial nitrogen filled rubber bladder type.
  • the accumulator 29 provides the high pressure hydraulic oil supply 15 for the servo-valve 12 and accumulator 29 is charged with hydraulic oil by the separate hydraulic power supply. Accumulators 27, 28 and 29 all help to dampen out resonance.
  • the hold-down mass and low stiffness suspension is now described which basically maintains contact between the vibrator output member 5 and the earth's surface during sweeps.
  • the lower portion of stiffening frame 23 is rigidly attached to the ground contact plate 5 to increase the structural stiffness of the ground contact plate 5 to minimise deflections due to forces on the ground contact plate 5 so that the displacement of the earth's surface is nearly uniform over the area of contact of the ground contact plate and the earth's surface.
  • the low stiffness suspension consists of multiple, for example four, rubber suspension members 34 or other low stiffness means whose stiffness is small compared to the stiffness of the transmitting medium.
  • Double acting hydraulic powered lift cylinders 35 fitted internally with pistons 36 and piston rods 37 are used to lift the vehicle clear of the earth's surface.
  • Piston rods 37 are flexibly attached to a suspension frame 38 in turn rigidly attached to the upper ends of the low stiffness suspension members 34.
  • the lower ends of the low stiffness suspension members 34 are rigidly attached to the upper part of the stiffening frame 23.
  • the lift cylinders are rigidly attached to a frame 39 in turn rotatably connected to a trolley 40.
  • the trolley 40 is slidably attached to beams
  • the lower portions of the beams 41 are rigidly attached to the upper surface of a vehicle 42, for example a truck or a trailer.
  • vehicle 42 is fitted with the usual suspension springs 43 together with road wheels and axles 44.
  • the apportioned amounts of all masses making up the total of the hold-down mass on the ground contact plate consist of the sum of all the vertical reaction components on the ground contact plate of the individual masses of the road wheels and axles 44, the springs 43, the vehicle 42, the beams 41, the trolley 40, the frame 39, the lift cylinders 35, the pistons 36, the piston rods 36, the suspension frame 38 and if needed additional hold-down ballast 45.
  • the frame 39 provides a slideway for the sliding means 33 as well as being part of the vehicle lift system which makes use of the cylinders 35 to lift the rear end of the vehicle so that the wheels 44 are clear of the earth during vibration on the transmitting medium.
  • hydraulic oil occupying volume 8 is returned to a separate hydraulic power supply through an electric operated solenoid valve not shown in fig. 1.
  • the solenoid valve enables the volume 8 to return to its minimum value for the commencement of a further sweep.
  • the lift cylinders 35 are operated to lower the road wheels at the rear of vehicle down to the earth's surface. Continued operation of the lift cylinders then results in elevation of the vibrator output member 5 clear of the earth's surface.
  • the rotatable connection of frame 39 to the trolley 40 then enables rotary movement of the frame 39 to a near horizontal position powered by a double acting hydraulic cylinder, i.e., a tilt cylinder, not shown in fig. 1.
  • the trolley 40 complete with the frame 39 and all of the elements rigidly and slidably attached to the frame 39, is then able to slide in beams 41 to result in distribution of the total weight of the VSS more evenly on, for example, four road wheels of the vehicle; two of these four road wheels being the wheels 44 at the rear of the vehicle and the remaining two road wheels being at the front of the vehicle.
  • the VSS may be represented by a mathematical model to take account of the dynamics of the VSS including the coupling of the VSS to the transmitting medium.
  • the mathematical model includes the flow rate of hydraulic oil from the flow valve 11 to the first end of cylinder 1.
  • the high pressure hydraulic oil supply 22 provides the flow rate by direct connection through the plumbing 24 to an inlet chamber 47 of the flow valve 11 shown in fig. 2.
  • the previously described control of poppet valve 19 enables hydraulic oil from chamber 47 to flow initially to a chamber 48 before leaving flow valve 11 to become injection flow 7.
  • the flow path taken by hydraulic oil is predominantly in a straight line from the supply 22 through flow valve 11 in the direction shown for the injection flow in fig. 1.
  • the displacement motion of the plate 5 may be sinusoidal, for example, when graphed against real time.
  • the pressure of hydraulic oil in the upper end of hydraulic cylinder 1 varies. The lowest magnitude of this pressure does not cause cavitation of hydraulic oil in volume 8 or in chamber 48 because of the existence of the pressure for an insufficient length of time.
  • Experimental tests have shown for example that cavitation does not occur at any time during operational performance of a VSS according to the invention on the transmitting medium for swept frequency operation during generation of the cyclic compression waves over a range of operational frequency of the cyclic compression waves of from 20 Hz to 500 Hz.
  • the operational performance of the invention therefore involves a different principle of operation hereby defined as single action operation as compared to all double acting vibrator sources for example "Vibroseis" apparatus.

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  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Acoustics & Sound (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)

Abstract

Source de vibrations sismiques pour créer des ondes de compression sismiques dans un milieu de transmission comme la croûte terrestre en vue de la recherche de minerais et de pétrole, ainsi que d'autres buts, formée d'un organe de sortie (5) conçu pour être appliqué au milieu de transmission afin de lui appliquer cycliquement des forces créées par un piston (2) se déplaçant dans un cylindre hydraulique à simple effet (1) à l'extrémité duquel un liquide hydraulique (7) sous pression est appliqué par intermittence au moyen d'une soupape de régulation d'écoulement (11). La soupape de régulation d'écoulement (11) est actionnée de préférence par une servo-soupape électro-hydraulique (12) à laquelle est appliqué un courant alternatif de fréquence variable.
PCT/AU1984/000173 1983-09-09 1984-09-07 Source de vibrations sismiques Ceased WO1985001359A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPG1331/83 1983-09-09
AU133183 1983-09-09

Publications (1)

Publication Number Publication Date
WO1985001359A1 true WO1985001359A1 (fr) 1985-03-28

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ID=3691886

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1984/000173 Ceased WO1985001359A1 (fr) 1983-09-09 1984-09-07 Source de vibrations sismiques

Country Status (2)

Country Link
EP (1) EP0155957A1 (fr)
WO (1) WO1985001359A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107037478A (zh) * 2017-06-06 2017-08-11 中国地质大学（北京） 一种新型振动器
CN111142152A (zh) * 2019-12-28 2020-05-12 吉林大学 一种可控震源反力实时调节系统及其调节方法
CN120159374A (zh) * 2025-04-21 2025-06-17 延安永协工贸有限公司 一种压裂设备

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3745885A (en) * 1971-10-07 1973-07-17 Continental Oil Co Hydraulic vibrator
US3789951A (en) * 1972-02-07 1974-02-05 D Silverman Vibrator system for generating seismic waves in the earth
GB1395841A (en) * 1973-06-26 1975-05-29 Continental Oil Co Hydraulic vibrator
US4143736A (en) * 1977-11-03 1979-03-13 Continental Oil Company Seismic transducer construction
US4178838A (en) * 1977-11-03 1979-12-18 Conoco, Inc. Oil porting system for dual cylinder vibrator

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3745885A (en) * 1971-10-07 1973-07-17 Continental Oil Co Hydraulic vibrator
US3789951A (en) * 1972-02-07 1974-02-05 D Silverman Vibrator system for generating seismic waves in the earth
GB1395841A (en) * 1973-06-26 1975-05-29 Continental Oil Co Hydraulic vibrator
US4143736A (en) * 1977-11-03 1979-03-13 Continental Oil Company Seismic transducer construction
US4178838A (en) * 1977-11-03 1979-12-18 Conoco, Inc. Oil porting system for dual cylinder vibrator

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107037478A (zh) * 2017-06-06 2017-08-11 中国地质大学（北京） 一种新型振动器
CN111142152A (zh) * 2019-12-28 2020-05-12 吉林大学 一种可控震源反力实时调节系统及其调节方法
CN120159374A (zh) * 2025-04-21 2025-06-17 延安永协工贸有限公司 一种压裂设备

Also Published As

Publication number Publication date
EP0155957A1 (fr) 1985-10-02

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