CN102812382B - Suppression ghost image and the seismic system of motion - Google Patents

Abstract

A kind of underwater seismic system of the noise reflecting for minimizing ghost image from seismic signal or being caused by seawater movement.This system includes two motion sensors.One sensor has one first response, and the noise and sonic sensitive caused that move platform.Another sensor has a kind of different structure, and this structure makes it isolate with sound wave, so that its response is mainly to motion artifacts.The output of combination the two sensor response eliminates the impact of motion artifacts.When being further combined hydrophone signals, decrease ghost image and reflect the noise caused.

Description

Suppression ghost image and the seismic system of motion

Technical field

Present invention relates in general to marine seismic prospectiong, and drag the sensing after exploration ship more particularly to for reduction In device, it is positioned at the less desirable seismic reflection in the sensor in seabed or in the sensor of autonomous nodes and effect of noise Equipment and method.

Background technology

As shown in fig. 1, in towed marine seismic survey, after the boats and ships 20 of Layer Near The Sea Surface 22, tow hydrophone array Row.These hydrophone are arranged in multisensor cable, are commonly called towing cable 24.This towing cable is used as the platform of hydrophone.With Sample drags the seismic source 26 at Layer Near The Sea Surface periodically to radiate acoustic energy.This acoustic energy passes through ocean travel downward, from fabric or Underwater stratum 28 reflects, and then returns back up to hydrophone array by ocean.The seismic energy reflected arrives towed array Receive point.This hydrophone array includes that multiple this type of receives point, and receives what some record upwardly propagated from sea bed 30 each Earthquake sound small echo.Subsequently, the record of hydrophone is treated as the seismic image of fabric.

Noise is a major consideration in the operation of pull-type towing cable.Noise source includes the expanded noise from sea And wave noise.And, pull this towing cable and can cause noise through sea water.A part for these noises is propagated by this towing cable, A part is by water column own propagation.The typical method processing noise source is to use time filtering and the combination of space filtering.Time Between filtering be by hydrophone signals is carried out discrete data sampling realizing with being applied to the weight of sample in time.Water Analog filter is to prevent from producing signal aliasing when frequency is more than sampling rate half to listen device channel also to include.Typically, empty Between sample formed, so that decayed along the length of towing cable by multiple independent hydrophone outputs are carried out being grouped summation The noise propagated.This spatial sampling is not for affecting at the noise of streamer axis vertically propagating.Typical hydrophone Group includes the hydrophone of about eight at the streamer section of 12 meters.

Acoustic impedance ρ c is the product of the velocity of sound in Media density and medium.Change as long as sound wave encounters acoustic impedance, at least A part of acoustic wave energy can reflect.Energy not reflected crosses two interregional demarcation line with not acoustic impedance Transmission (refraction).This pressure wave is barometric wave, and this causes the Particles Moving on the direction of propagation.Between two different homogenous medium On planar interface, sound wave with incidence angle θ₁Equal angle reflection, and with angle, θ₂Refraction.This refraction angle is:

θ₂=sin^-1(c₂sinθ₁/c₁)。

Subscript refers to sound wave and moves to medium 2 from medium 1, and c₁And c₂It it is the velocity of sound in each medium.If angle of incidence θ₁Be zero, then the angle, θ in refractive power transmission path₂Would is that zero.

For incidence angle θ₁It is zero and does not has energy to be converted into the situation of shear wave energy, in sea water-air interface Reflection coefficient is described as:

$R_{\mathrm{pp}}=\frac{{\mathrm{\ρ}}_2{c}_2-{\mathrm{\ρ}}_1{c}_1}{{\mathrm{\ρ}}_2{c}_2+{\mathrm{\ρ}}_1{c}_1}\≈-1.$

Reflected energy in sea water-air interface is R² _pp, or close to 1, this makes sea be the sound of an approximate ideal Can reflector.After seabed or target interested return, this energy is returned towing cable by sea surface reflection again.Due to typical water Listening utensil to have omnidirectional response, therefore hydrophone array is also recorded for ghost image response, and the response of this ghost image is from sea surface reflection time delay Arrive and the earthquake sound small echo of polarity reversal.This ghost image is the earthquake sound wave of travel downward, when adding on desired waveform Time this earthquake sound wave have damage record seismic image.The reflection that this ghost image causes also can be extended to seabed or other strong reflections Thing, and return up and again disturb desired echo and reduce picture quality further.These reflections are commonly called repeatedly Ripple.

For the pressure wave of vertical transmission, this ghost image at hydrophone at f_notchAt=c/2d, the frequency spectrum of response produces One trap, wherein c is the velocity of sound, and d is streamer depth.By convention, earthquake towed cable is towed at 10 meters or more shallow deep Degree.At 10 meters of degree of depth, trap frequency (f_notch) it is 75Hz.For high earthquake image resolution ratio, frequency response must expand to Outside 100Hz.Because trap frequency is inversely proportional to towing depth, therefore, towing cable the most towed the shallower degree of depth with improve The resolution of seismic image.Owing to desired seismic signal being defined interference from the noise on sea, therefore drag in shallow water It is problematic for draging.These impacts deteriorate with breakup, sometimes result in staff's interrupt operation, until weather becomes Good.The impact eliminating ghost image-trap makes it possible to pulling away from the deeper degree of depth of surface disturbance.

Seismic sensor is being placed in the undersea system of sea bed, is being suppressed by known technology (as p-z sues for peace) Ghost image and many subwaves.In sound wave, pressure p is a scalar, and particle rapidity u is a vector.Hydrophone comes with positive omnidirectional response Record earthquake sound wave pressure p.The geophone of vertical orientation or accelerometer use to the just response of upwards signal with to downwards The Negative Acknowledgment of signal records earthquake sound wave-particle speed u_zVertical component.In p-z sues for peace, rate signal adds at it Weighed by the acoustic impedance ρ c of sea water before pressure signal.Also need to adjust universal single-axis sensors with to by any reception signal Off-axis arrive caused by the change of particle-motion sensor sensitivity be responsible for.If use accelerometer, can its output integrated Signal, to obtain rate signal, maybe can distinguish hydrophone signals, so since, can preferably and accelerometer spectrally Join.This can produce a kind of has upwardly propagating the total regression of ripple and to the faintest response of travel downward ripple to press down Ghost image processed and the combination sensor of many subwaves.Described in the patent of the U.S. Patent No. 6539308 invented by Monk et al. A kind of Signal Regulation realizing single duplicate removal ghost mark and signal integration method.Fig. 2 is the response of particle-velocity sensor Two dimension (2D) represents.Fig. 3 is that the 2D that the response of all directional hydrophone is added with the response of vertical particle-motion sensor represents.Logical Cross and rotate these 2D response around its vertical axis it is envisioned that respond to complete three-dimensional.

At present, use the technology of similar p-z summation to allow in the towing of the deeper degree of depth in pull-type towing cable collection The interference do not reflected by ghost image-trap, has caused everybody interest.Because this towing cable is drawn by by towing or sea effect The acceleration ratio risen is by expecting that the acceleration that seismic reflection causes is big, and therefore the particle motion sensor in operation earthquake towed cable is deposited In problem.Additionally, these unnecessary acceleration and desired reflex response are positioned in identical band.When towing naval vessel runs into Wave, ship velocity is by little disturbance.Typically, this naval vessel also runs into yawing rotation.Fig. 4 depicts Negotiation speed change 32 and yawing rotation 34 be applied to the energy of towing cable 24.Fig. 5 is to describe to cause the acceleration in towing cable 24 and the energy of shear wave Side view.(for purposes of illustration, exaggerate the energy impact on towing cable in Figure 5.) by elastic stretching parts 36(typical case Ground, before sensor array) most of energy of having decayed.Although this energy is greatly decayed, but still a remaining part.By Expect that the acceleration a that the plane pressure wave that seismic reflection produces causes is given by:

$a=\frac{p2\mathrm{\πf}}{Z},$

Wherein p=sound wave sound pressure level, f is frequency, and Z is acoustic impedance.The performance of particle velocity measure system should be close Outside noise limit.Typically, geological data user requires that the outside noise from towing cable hydrophone system is less than 3 microbars.By Acoustic impedance in sea water is 1.5MPa.s/m, and therefore the 3 microbar pressure waves of 4Hz produce the particle acceleration of about 0.5 μ g.Fig. 6 Illustrate the mechanistic model of the frequency response of the middle typical cable axial acceleration of towing cable.In some cases, exist at 4Hz Only the secondary wave crest of 1.5 orders of magnitude lower than main crest shows that cable dynamic motion can be more than there being seismic signal to be measured.

Authorizing the U.S. Patent number 7,167,413 of Rouquette uses accelerometer to suppress ghost image-fall in earthquake towed cable Wave effect.Rouquette uses mass-spring system to reduce cable power to accelerometer and the impact of load cell system To measure and to suppress the cable movement induced noise on this accelerometer.Rouquette system relies on well-known complicated machinery Relation, this relation can not be with manufacturing tolerance, aging and environmental aspect holding is consistent.Rouquette uses signal processing self adaptation Algorithm is derived load cell and the mass-spring system relation with the acceleration acted on the accelerometer of original place Rouquette describes the mechanical-electronic system of a kind of complexity.

Described a kind of use sound wave particle rapidity by the U.S. Patent No. 7,239,577 of Tenghamn et al. invention to pass The equipment of sensor suppression ghost image trap and method.Tenghamn et al. teaches fluid damping, gimbal stationary geophone Use.The fluid encapsulating this geophone is selected to provide the biography being suspended on its balancing stand as is commonly known in the art The damping of sensor.But, it is well known in the art that and not do not describe in Tenghamn et al. is quality-spring vibration isolation system The cable machinery motion impact on earthquake receiver response can be reduced.The motion of the geophone caused by cable machinery motion Sound wave Particles Moving in responding with geophone is undistinguishable.Desired seismic wave Particles Moving is by Tenghamn etc. The cable machinery motion of people is covered.This technology also produces the response of similar cardioid in Fig. 3, wherein, the most still has From this plane and excited the less desirable signal caused by the towing cable along this streamer axis.

A kind of combination load sensor and particle fortune is described by the U.S. Patent number 7,359,283 of Vaage et al. invention Dynamic sensor solves the mechanical movement method on the impact of particle motion sensor.In the method, a certain frequency is not used f₀The response of following particle motion sensor, and simply estimate from pressure transducer response and the known pressure transducer degree of depth Meter.The frequency of these suppression is that the mechanical movement of towing cable is desired.In lower frequency-of-interest, estimate that response has difference Signal to noise ratio.This suppression below a certain frequency is not optimum, because it further suppress the useful letter in important low-frequency range Number, in this low-frequency range, there may be depth targets data.

Although these patents all describe the method for the ghost image trap in suppression earthquake towed cable, but do not expound adequately and drag The effect of noise that hawser and other influences particle-motion sensor or hydrophone are measured.All these patents also lack generation High-fidelity, there is the sensing sound wave composition of the good signal-to noise ratio of low-limit frequency interested.

Summary of the invention

These shortcomings can be overcome by the underwater seismic system embodying feature of the present invention.This type of system includes one first fortune Dynamic sensor and second motion sensor, this first motion sensor may be used for underwater platform and has first sound Should, this second motion sensor is arranged near this first motion sensor and has one second response.These are first and second years old The amplitude of response approximates for platform moves, the most different to sound wave Particles Moving.

One version includes first motion sensor and second motion sensor, this first motion-sensing utensil Having first acoustic impedance to represent platform motion and the first sensor signal of sound wave to generate, this second motion sensor is arranged Near the first motion sensor and there is rising tone impedance represents that platform moves and represents cause by sound wave to produce Second sensor signal of the Particles Moving of decay.For combining the dress of this first sensor signal and this second sensor signal Put the noise caused by platform motion of having decayed, and generate the response to the Particles Moving caused by sound wave.

Another version includes first motion sensor and be arranged near this first motion sensor Two motion sensors.The second motion sensor that configuration acoustic hood only shields from sound wave Particles Moving.

Accompanying drawing explanation

The aspects of the invention and spy can be better understood from by referring to following description, claims and accompanying drawing Levy, wherein:

Fig. 1 is the side view of typical seismic prospecting operation, the row's hydrophone under hawser retouching after illustrating exploration ship Paint the reflected seismic energy arriving towed array reception point；

Fig. 2 is the X-Y scheme of particle velocity sensor response；

Fig. 3 is that all directional hydrophone responds the X-Y scheme being added with the response of vertical particle-velocity sensor；

Fig. 4 be such as Fig. 1 in typical case exploration top view, depict towed speed fluctuation and driftage；

Fig. 5 be such as Fig. 4 in the side view of exploration, depict exaggerating of the fluctuation of towing cable pro forma towed speed and driftage Effect；

Fig. 6 is such as the figure of the typical acceleration of towing cable in exploration in Fig. 1；

Fig. 7 is the block diagram of the underwater seismic system trade edition embodying feature of present invention, has different acoustic response including two Motion sensor；

Fig. 8 be such as Fig. 7 in the motion sensor frequency domain block diagram to the acoustic component response of incident acoustic energy；

Fig. 9 be such as Fig. 7 in the motion sensor frequency domain block diagram to the platform component motion response of incident acoustic energy；

Figure 10 be such as Fig. 7 in the time-domain diagram of output of motion sensor, this output is to platform motion harmony (pressure) ripple Response；

Figure 11 be such as Fig. 7 in the time-domain diagram of output of motion sensor, this output is only response to platform motion；

Figure 12 is the difference of Figure 10 and Figure 11 outlet chamber, represents sound (pressure) the ripple signal removing platform motion；

Figure 13 be such as Fig. 7 in a version of seismic system, wherein this motion sensor is encapsulated in different structure, this Provide different acoustic impedances；

Figure 14 A and 14B be such as Fig. 7 in the sectional view of another seismic system, this system has the arrangement of multiple axial symmetry Motion sensor in towing cable；

Figure 15 is such as another version of seismic system in Fig. 7, and the most each motion sensor has a different sound to cut Face is to provide different acoustic response；

Figure 16 is another version of the seismic system of the Figure 15 with more high-gain；

Figure 17 be such as Fig. 7 in the side view of seismic system, this system is arranged on rotatably suspended from towing cable In cable positioning aircraft；And

Figure 18 be such as Fig. 7 in the side view of seismic system, this system is arranged on the electricity that connect into straight line intersegmental with towing cable In cable positioning aircraft.

Detailed description of the invention

Fig. 7 is the block diagram of underwater seismic system 19 trade edition embodying feature of present invention, and this system includes using motion to pass Sensor or the technology of sensor cluster, the signal causing sound wave has different responses, and to platform (such as, towing cable, cable Or autonomous nodes, motion) moving has similar response, the signal to noise ratio of the data obtained to rise to seismic imaging.At Fig. 7 In, 40,41 and pressure transducer 42(of two motion sensors is usually hydrophone) signal is provided, these signals are carried out Combine to generate the signal that noise reduces and removes ghost image.One group of pressure transducer can be used for the occasion of single sensor, such as, fall The low noise caused by the pressure wave propagated along this streamer axis.It is desirable that this motion sensor is sensitive to unidirectional current and can Decompose this gravity vector, otherwise, need an extra orientation sensor.This first motion sensor 40 has the sound to sound wave Should, this response ideally but not necessarily equal with the response of sea water；If requiring higher gain, its response can improve To the response exceeding sea water.Second motion sensor 14 has the response to sound wave, this response and the first motion sensor 40 Respond significantly different.Available sensors difference in terms of material composition or geometry realizes this difference in acoustic response. In all versions of native system, select material and the geometric properties of two sensors, so that they are to platform motion Mechanical response mates.Such as, if each motion sensor is designed in the way of identical with second order mass-spring system Interact with cable, then make the quality of sensor (include additional mass, if any) and they springs of being associated Coefficient is equal.First and second outputs 44,45 of the first and second motion sensors 40,41 subtract each other 46, or in this locality or far After journey processes, to generate the response signal 48 that noise reduces, this signal represents what the sound wave moved by platform of having decayed caused Particles Moving.Subtraction block 46 constitutes one for combining first sensor signal and the device of the second sensor signal.If The opposite in phase of the signal of one of sensor, then the device being used for combining first sensor signal and the second sensor signal will be used Adder block replaces realizing.Regulate 50 noises reduce response with matching pressure sensor respond 52, such as hydrophone signals, and The final output signal 56 inhibiting ghost image trap and many subwaves equally is generated for p-z summing unit 54.Combination the first biography Sensor signal and the device of the second sensor signal and p-z summing unit can pass through analog circuit, Digital Logical Circuits or micro-place Algorithm this locality in reason device realizes or is processed by computer on ship or off-line data remotely realizing.

Fig. 8 is the frequency domain block diagram of two motion sensors 40,41 in Fig. 7, illustrates they sound waves to projectile energy The transmission function of component 58.This acoustic component includes seismic signal interested.First sensor 40 and the second sensor 41 have There is different sound wave transfer function H₁(s) and H₂(s).Transfer function H₁S () is sensitive to sound wave Particles Moving, therefore the first sensing Device 40 generates the output response O representing Particles Moving₁(s).Transfer function H₂S () is insensitive to sound wave Particles Moving, and therefore second Sensor 41 generates the output response O of the motion not including surrounding acoustic medium particle₂(s).Fig. 9 is two motion-sensings of Fig. 7 The frequency domain block diagram of device 40,41, represents they transmission functions to the platform component motion 59 of projectile energy.To platform motion Speech, the transfer function H of two motion sensors 40,41₃(s) and H₄(s) proportional in amplitude (or equal), but in phase place Upper possible contrary.Therefore, 40, the 41 pairs of platform motions of two sensors all have similar output response O₃(s) and O₄(s).First It is H for first sensor with the composite transfer function of first 40,41 pairs of projectile energies of motion sensor₁(s) and H₃(s) Combination and be H for the second sensor₂(s) and H₄The combination of (s).The complex response of two sensors is to the first motion-sensing It is O for device₁(s) and O₃The combination of (s) and be O for the second motion sensor₂(s) and O₄The combination of (s).Figure 10 is The example of the time domain response of projectile energy is represented by one sensor 40, and this projectile energy includes platform motion and sound wave.First passes The response 44 of sensor is sensitive to platform noise and sound wave both of which.Figure 11 is corresponding to identical projectile energy of the second sensor 41 Response.The response 45 of the second sensor is only sensitive to the platform noise component of projectile energy.Figure 12 depicts two sensings of combination The result of the response of device, this is combined through the output 44 from first sensor and deducts the output 45 of the second sensor to generate Fig. 7 In deduct the acoustic signals 48 of noise.In order to simplify description, although the second sensor is considered zero to the response of pressure wave, but Pressure wave may be had small response or even Negative Acknowledgment.Additionally, the first and second sensor outputs may be with towing cable Vibrations Incomplete matching.But, even if in these cases, signal subtraction still results in has the platform motion being greatly attenuated The acoustic response of response, it is combined with hydrophone data that this platform motion response can regulate and pass through p-z summation in proportion.

The different particular versions of the general-purpose system represented in Fig. 7-9 block diagram use the acoustic impedance of different stage to obtain sound The expectation difference of the little wave response of sound.As it has been described above, two motion sensors 40,41 and pressure transducer 42 is arranged in platform, On platform or be installed to platform.For example, it is possible to it is fixed to be enclosed in underwater towing line or be arranged on the cable being attached on towing cable In the aircraft of position.Such as, these motion sensors are the most mutually isolated, but position is close and is divided into independent by dispenser Region.First motion sensor is enclosed in a first area with surface, the acoustic impedance on this surface and the sound of surrounding seawater Impedance approximates, so that sound wave can penetrate this surface with minimum reflection and act on sensor.Second motion sensor It is located in the housing of the sound insulation in a second area, and is not affected by incident acoustic wave.Towing cable under pulling force has itself Faint and unstable response to sound wave.Towing cable itself is registered as platform motion to any response of sound wave.Therefore, first Sensor has the proportional response to sound wave；And the second sensor has minimum response.Additionally, correct this sensor group Part, to mate the response to platform motion (such as, streamer vibration), such as, can lead to if showing as second order mass-spring system Cross and make their quality (include additional mass, if any) and corresponding spring constant is equal.From first sensor signal Deduct (or after Local or Remote processes) the second sensor signal towing cable being greatly attenuated-motion response and generate desired Acoustic signals.

Figure 13 shows a particular version of the seismic system of Fig. 7-9, is acoustically isolated with by center dispenser 64 Two motion sensors 60,61, an and pressure transducer 62.First motion sensor 60 is included in rigidity, thoroughly In the first area 66 of the towing cable on the surface 68 of sound.Such as, what surface 68 crust 70 flexible by, entrant sound covered wears Hole, rigidity housing.The inside of first area 66 is filled with liquid.It is desirable that this crust and liquid all have and surrounding sea The acoustic impedance of aqueous phase etc..First test quality 72 hangs in a liquid, this quality have one ideally but not necessarily with The acoustic response that the acoustic response of liquid is equal；If requiring higher gain, its response can be increased to exceed the response of sea water.Should First test quality 72 is connected to the surface of towing cable by means of displacement, speed or the acceleration transducer as motion sensor. This first sensor 60 uses the surface of towing cable as reference standard, and serves as and dynamically couples this test quality and the bullet of towing cable Spring.Such as, this first sensor can be monocrystal or PZT bool.If this sensor is a single-axis sensors, the most Test quality system may be used for being formed a three-axis sensor, wherein calibrates all of test quality thus coupling sound Both sound and dynamic response.The replacement scheme that multiaxis is measured is: as long as the response of this mass sensor can keep independent, for Multiaxis is measured and multiple sensors is connected to same test quality.Second area 67 on isolator opposite, first area 66 Assembly in by the second sensor 61 with second test quality 73 be connected.The assembly of the second sensor and the group of first sensor Part is different, because its surface of shell 69 has an acoustic impedance much larger than the acoustic impedance of cycle sea water, and its inside 67 is full of Air is illustrating the elasticity can not ignore any in surface of shell 69.The hardness of the second sensor housing adds it The impact of the acoustic impedance strengthened, this allows this housing to serve as a blimp, the faraday being analogous in electromagnetism (Faraday) Cage.The acoustic impedance of the second surface of shell 69 is set with the material with suitably high density or the velocity of sound.

Embody another version of seismic system of the present invention as shown in figs. 14 a-b, with two groups of motion sensors 80,81 and a pressure transducer 82.In this version, first group of sensor 80 and second group of sensor 81 are connected to carrying The single rigid body 84 of streamer vibration.This rigid body has 86, small diameter of Part I of a major diameter Part II 87 and the changeover portion 88 of connection the first and second parts.Smaller diameter portion 87 is with an inner side 83 and one The tubulose body in outside 85.First group of sensor 80 is round a part for the Part II 87 of rigid body 84, and connects Outside it 85.Available three or more single sensors constitute this first group 80.If not using axial symmetry, then this One group of sensor 80 and be in the side of this rigid body.Be made up of the flexible membrane covered on the stiff case of perforation is saturating This sensing system of 90, sound surface and surrounding seawater are separately.Between Part II 87 and the surface 90 of this rigid body 84 First cavity 92 is filled with liquid.It is desirable that surface 90 and liquid have the acoustic impedance equal with the acoustic impedance of surrounding seawater.Tool The the first test quality 94 having the acoustic characteristic identical in quality with the first test in Figure 13 is suspended in the first cavity 92, and Part II 87 round rigid body 84.This first test quality 94 is mechanically connected by first group of motion sensor 80 To the outside 85 of this rigid body 84, this first group of motion sensor has identical with the first sensor 60 in Figure 13 version Characteristic, but rigid body 84 is as its reference standard.Second cavity 93 is completely contained in the tubulose second of rigid body 84 Divide in 87.This second cavity 93 comprises a second test quality 95 floated on a liquid, and by being connected to this rigidity originally Second group of motion sensor 81 of the inner side 83 of body is connected to rigid body 84.Correct the dynamic response of second group of sensor 81, Streamer vibration to be had the response of the response mating first group 80.But, it is different from the first test quality 94, to the second test The not requirement of the acoustic response of quality 95.Rigid body 84 itself functions as the acoustic hood to second group of sensor 81, and by having phase The material of high acoustic impedance is formed.The usefulness of arranged in co-axial alignment is that each test quality is added by multiple independent sensor Speed responds.The output signal combining this motion sensor obtains the more robust iterative of actual acceleration value.With description Equally, first group and second group of sensor 80,81 are to radial direction motion sensitive；If need three axles sensitivity, the most each with should Streamer axis cavity in line can include an additional test-quality-sensing system.

Figure 15 shows another version of seismic system.With rigidity, the towing cable on entrant sound surface 98 have two motions Sensor 100,101(such as, the accelerometer of three axles sensitive to unidirectional current) and a pressure transducer 102(is such as, water is listened Device).Such as, this surface 98 can include bore a hole a, housing for rigidity, and this housing is flexible by one, the crust of entrant sound institute Cover.Micro Electro Mechanical System (MEMS), PZT, monocrystal can be passed through or there is any other technology of similar effectiveness realize this Accelerometer.Motion sensor 100,101 is fixedly secured to the first and second stiff cases 104,105 and appoints can directly measure What dynamically towing cable motion.Two sensors are the most acoustically connected to this cable surface 98, but for example are by center dispenser 106 The most mutually isolated.Each of first and second housings 104,105 will be constructed so that the quality of the first housing is plus it The quality that the quality surrounded is surrounded plus it equal to the second housing.Dynamic linker between design housing and towing cable surface 98 103 are used as the second order mass-spring system with identical springs coefficient, therefore, maintain equal quality-spring relation.Separately On the one hand, these housings have different sound cross sections, and therefore, they generate different responses to acoustic pressure wave.Specifically, first Sensor 100 generates the first sensor signal 108 of an expression sound Particles Moving well；Second sensor 101 generates one Individual second sensor signal 109 the most insensitive to sound wave.It is also likely to be different material structures with different solids Sensor housing is to produce different cross sections and thus to produce different transmission functions for each sensor.In this locality or far After journey processes, deduct the second sensor signal 109 to provide desired pressure wave signal from first sensor signal 108, this Signal has, to towing cable motion, the response being greatly attenuated.Such as, available open cell foamed plastic is as each housing 104,105 and Dynamic linker 103 between surface 98.It is full of and is corrected thus mates the liquid of the acoustic impedance of surrounding seawater, this foam plastics It is also used as entrant sound adapter.In this example, it is contemplated that liquid and be filled with air, this first housing 104 is carried out Seal thus any very important elasticity in housing is described；And, the second housing 105 is bored a hole or slotted, and allows it to use Liquid around is full of.They different responses to incident pressure ripple of comprehensive differences in global density explanation between housing.

Figure 16 shows the revision of the seismic system of the Figure 15 of the overall gain being intended to raising system.This first sensor 110 is acoustically identical with the first sensor 100 dynamically shown as with Figure 15.This second sensor 111 generate one right The response of pressure wave and a towing cable motion response, the response of pressure wave mated by this with the response of first sensor 110, and this drags Cable motion response and this first sensor are equal in amplitude, and contrary in phase place.The same with in Figure 15 build the first housing 114 and second housing 115, particularly in terms of sound cross section and density, therefore, they cable movement is had similar quality- Spring responds, but has a visibly different response to incident sound pressure Reeb.Additionally, this second housing 115 includes one Test quality 116, this test quality is designed to swing in a liquid and have the sound wave of the response of coupling the first housing 114 and rings Should.On the other hand, test quality responds the response much smaller than housing to towing cable motion, this is because test quality is suspended in liquid In body, housing is mechanically connected to cable surface.Test quality 116 relies on and uses the second housing as the displacement of reference standard, fortune Dynamic or acceleration transducer 111 is connected to the second housing 115 not firmly.In this example, use is made up of piezoelectric Cantilevered accelerometer as motion sensor.Multiple accelerometers can be used for constituting a three-axis sensor, wherein to each survey Examination quality is corrected thus mates first housing 114 acoustic response at its each axis.Therefore, it can positively (i.e. homophase) The pressure wave being applied to the motion in this test quality 116 rather than on the second housing 115 detected.Therefore, pass from first The pressure signal of sensor 110 and the second sensor 111 mates in amplitude and symbol.On the contrary, negatively (that is, anti-phase) detection Affect the second housing 115 rather than the streamer vibration of test quality 116.Therefore, from the vibration signal of sensor in amplitude Coupling, but there is contrary symbol.In this case, by addition 118 rather than subtraction, combination is from two sensors 110, the signal of 111 is to generate the towing cable motion response being greatly attenuated and the gain improving acoustic response simultaneously.Alternatively, may be used Use another hook wall testing quality in the first housing 114.But, owing to the polarity of first sensor signal will be run equally Fall, it is therefore necessary to combined with this second sensor signal by subtraction rather than addition.

As shown in Figure 17, during the Sensor section of seismic system 19 may be installed streamer cables 120 or by collar 124 It is rotatably connected in cable location equipment (such as, cable compensation or cable management aircraft 122) of towing cable.In Figure 18 Shown in, the cable location equipment 126 that straight line connects between head and the tail streamer section 128,129 can be placed in the sensing of seismic system 19 In device part.It is apparent that these sensors may be installed in other equipment, these equipment can be attached to towing cable, submarine cable Or autonomous nodes is internal, above or be attached to these equipment.

Have to unidirectional current with to being manufactured by Houston, Texas, United States ION Geophysical company The triaxial accelerometer of the response that VectorSeis sensor is similar is suitable to multiple embodiments of the present invention.Due in seismic waves Not having DC component, therefore, the DC response of this motion sensor is for detecting the orientation of sensor relative gravity.Design towing cable The known direction of axis is an axis of sensor.Owing to this streamer axis direction is known and gravity vector is measured , therefore sensor direction and thus arrive sensing seismic waves direction can rotate electronically with relative gravity, from And make, seismic waves upwards can be accepted and refuse downward seismic waves.

Any sensor of detection motion can be used.This sensor can be to position, speed or acceleration responsive Any motion sensor.Such as, as described in the patent in the U.S. Patent No. 7,239,577 invented by Tenghamn et al. Universal first geophone can be with the second seismometer array encapsulating, so that any sound wave is had by it The least response or do not respond to, and towing cable motion is had identical response, to realize desired result.As long as having suitable When sensor performance, it is possible to use piezoelectric accelerometer.

If sensor not can determine that himself direction, sensing system can include single alignment sensor.Alternative Ground, machinery (such as balancing system) can be used for being fixed on sensor known orientation.The flight being attached on towing cable sets Standby (sometimes referred to as aircraft) can be also used for forcing to move to sensor desired orientation.

The present invention is not intended to limit for pull-type marine streamer.Described technology can be additionally used in other platforms, such as Submarine cable and autonomous nodes system.Additionally, described sensing system can be used for collecting individually geological data；Or, they Can bundle and be used in conjunction with, combine their data to reduce the impact of local flow patterns.

Claims (17)

1. a underwater seismic system, including:

One the first motion sensor, this first motion sensor can be used on underwater platform and have first acoustic impedance or First sound cross section represents, to generate, the platform motion and the first sensor signal of Particles Moving caused by sound wave；

One the second motion sensor, this second motion sensor is arranged near this first motion sensor and has one the Two acoustic impedances or rising tone cross section, wherein this rising tone impedance is different from this first acoustic impedance, or this first sound cross section is different from This rising tone cross section, with generate represents platform motion and represent the decay caused by sound wave Particles Moving second sensor believe Number；

For combining this first sensor signal and this second sensor signal thus the noise caused by platform motion of decaying And generate the device of the response that the noise to the Particles Moving caused by sound wave reduces；And

One dispenser being arranged between this first motion sensor and this second motion sensor, to be acoustically isolated This first motion sensor in one region and this second motion sensor in separate second area；

Wherein this first motion sensor in this first area is arranged in first medium, the acoustic impedance of this first medium and sea The acoustic impedance match of water, and wherein this second motion sensor in this second area is arranged in second medium, and this is second years old Medium has the acoustic impedance different from the acoustic impedance of this first medium.

2. underwater seismic system as claimed in claim 1, farther includes:

One rigid body being connected on this underwater platform and experiencing platform motion；

Multiple first motion sensors being connected in this rigid body and multiple second motions being connected in this rigid body Sensor.

3. underwater seismic system as claimed in claim 1, including:

One rigid body being connected on this underwater platform and experiencing platform motion；

Around this first motion sensor, this second motion sensor and this rigid body and the surface of the entrant sound contacting sea water； And

One first test quality and one second test quality；

Wherein this underwater seismic system is divided into one and receives this first test perimeter of quality and one by this rigid body Receive the interior zone of this second test quality；And

Wherein this first test quality is connected in this rigid body by this first motion sensor, and this second motion sensor This second test quality is connected in this rigid body.

4. underwater seismic system as claimed in claim 3, wherein this first motion sensor is also by this first test quality even Receive in this rigid body.

5. underwater seismic system as claimed in claim 4, wherein this first test quality, this rigid body and this second test Quality arranged in co-axial alignment.

6. underwater seismic system as claimed in claim 1, also includes:

One the first stiff case being strongly attached on this first motion sensor；

One the second stiff case being strongly attached on this second motion sensor；

Wherein this first stiff case and this second stiff case have different sound cross sections to incident acoustic wave.

7. underwater seismic system as claimed in claim 6, including:

One is surrounded this first area and the surface of second area；

One the first adapter between this first stiff case and this surface；And

One the second adapter between this second stiff case and this surface.

8. underwater seismic system as claimed in claim 7, wherein this first adapter and this second adapter include that one is opened Hole plastic foam material.

9. underwater seismic system as claimed in claim 8, farther includes a kind of liquid filling this open cell foamed plastic, and And wherein this is filled with the acoustic impedance match of acoustic impedance and sea water of open cell foamed plastic of liquid.

10. underwater seismic system as claimed in claim 1, farther includes:

One the first stiff case being strongly attached on this first motion sensor；

One the second stiff case for this second motion sensor；

One is positioned at this second stiff case inside and is connected to this second rigidity not firmly by this second motion sensor Test quality on housing；

Wherein sound wave is in phase responded and anti-phase to platform by this first motion sensor and this second motion sensor Motion responds.

11. underwater seismic systems as claimed in claim 1, farther include a hydrophone sending hydrophone signals, should The response combination that hydrophone signals needs to be reduced with this noise is with Multiple attenuation or decay ghost image response.

12. underwater seismic systems as claimed in claim 11, wherein this hydrophone and this first motion sensor and this second Motion sensor is apart from close.

13. underwater seismic systems as claimed in claim 1, wherein this first acoustic impedance is less than this rising tone impedance.

14. underwater seismic systems as claimed in claim 1, wherein this first medium has the first density, and wherein this Second medium has second density bigger than this first density.

15. underwater seismic systems as claimed in claim 1, wherein this be used for combining this first sensor signal and this second The device of sensor signal deducts this second sensor signal from this first sensor signal.

16. underwater seismic systems as claimed in claim 1, including a sensor cable being used as underwater platform, Qi Zhongduo Individual described first motion sensor and multiple described second motion sensor are disposed in and separate position along this sensor cable Put place.

17. underwater seismic systems as claimed in claim 1, including the cable location equipment being used as underwater platform or autonomy Node, wherein this first motion sensor and this second motion sensor are arranged on this cable location equipment or this autonomous nodes In.