GB2481998A

GB2481998A - Apparatus and method for conveying a seismic signal into a subterranean location via a casing in the borehole

Info

Publication number: GB2481998A
Application number: GB1011792.7A
Authority: GB
Inventors: Laurie Linnett
Original assignee: BIOS TECHNOLOGIES LLP
Current assignee: BIOS TECHNOLOGIES LLP
Priority date: 2010-07-14
Filing date: 2010-07-14
Publication date: 2012-01-18
Also published as: GB201011792D0

Abstract

The invention relates to a system and method for seismic analysis of a subterranean formation. This is done using a transmission apparatus comprising a signal generator 20 for generating a vibrational signal to a subterranean transmission member 5 which then conveys the vibrational signal to a subterranean location. The signal generator 20 may comprise a vibrator having a hydraulic ram unit 35 for driving and actuating an impact member 40 which applies a vibration signal pulse to the wellbore casing (transmission member 5). At least one receiver 30 may be included for detecting the signal after it has passed through the subterranean location. The signal generator may be adapted to generate a signal so as to form a wave front and/or a standing wave in the transmission member 5. The vibrational signal may be emitted from more than one point from the transmission member (fig.2a).

Description

Sensing System and Method

Field of the Invention

The present invention relates to a system and method for remote sensing. In particular, but not exclusively, the invention relates to sonic or seismic analysis of the environment, or structure, around a tubular structure such as a pipeline, drill casing or the like.

Background to the Invention

In the field of drilling, including oil field exploration or geological probing, seismic measurements are particularly useful in providing data to operators for use in altering and optimising drilling parameters and/or assessing and analysing features of surrounding geological structure, such as characterising hydrocarbon containing formations.

For example, reflection seismology is used to probe the structure of geological formations in order to determine subsurface structure of rock formations, including the type or density of rock strata. This method typically involves providing a suitable vibration signal, for example by using an explosion or a vibrating or impacting source, and measuring the signal reflected from geological features.

Examples of seismic methods include downhole and crosshole seismic surveys.

Downhole surveys comprise applying a signal using a vibration source at the surface and detecting the signal and its reflections at various locations down a well bore.

Crosshole surveys comprise locating a vibration source in a first well bore and detecting the signal produced by the vibration source and its reflections using a receiver in a second well bore.

Crosshole seismic tomography techniques involve placing a string comprising a plurality of receivers in the second well bore and lowering a source into the first well bore and emitting signal pulses at a plurality of positions in the first bore. In this way, a multitude of signal paths can be used to construct a profile of the geological structure between the two bores.

This background serves to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the invention may or may not address one or more of the background issues

Summary of Invention

According to a first aspect of the present invention, there is provided a transmission apparatus comprising: a signal generator for generating a vibrational signal; a subterranean transmission member configured to convey the vibrational signal generated by the signal generator to a subterranean location.

The apparatus may comprise at least one receiver for detecting the vibrational signal and/or signals resulting therefrom.

The signal generator may be adapted to generate a plurality of signals.

The transmission member may comprise a hollow member, such as a tubular member, conduit or duct.

The transmission member may be provided in a borehole.

The transmission member may comprise a borehole casing, or other item of drilling or oil production apparatus, such as a drill pipe, transition pipe, production pipe and/or the like.

The transmission member may comprise a pipe, such as an oil pipeline. The transmission member may be a pipe usable to transport fluids such as oil, natural gas and/or water.

The transmission member may comprise piling or other architectural structure.

The transmission member may be metallic, such as a steel member.

The apparatus may comprise a plurality and/or an array of signal generators and/or receivers.

At least one signal generator and/or receiver may be adapted to be located above ground.

At least one signal generator and/or receiver may be adapted to be locatable downhole.

The signal source may comprise a vibrator. The vibrator may comprise an impact member. The impact member may be hydraulically actuatable. The impact member may be arranged for striking the transmission member in order to impart a vibration signal pulse to the transmission member.

At least one signal generator and/or receiver may be separate.

At least one signal generator and/or receiver may be integral.

At least one signal generator may comprise a transducer, which may be operable as both a signal source and a receiver.

At least one signal generator and/or receiver may comprise a piezoelectric transducer.

At least one signal generator and/or receiver may be connected or connectable to the transmission member. At least one receiver may be separate from the transmission member. The signal generator and/or receiver may be movable.

The one or more signal sources and/or receivers may be linked to a controller.

The vibrational signal may be a vibrational pulse, such as a ping or chirp.

The signal generator and/or receiver may comprise an ultrasonic signal generator and/or receiver. The vibrational signal may comprise sound. The signal may comprise an ultrasonic signal.

The controller may be arranged to control at least one signal generator to thereby control the form of the vibrational pulse.

The apparatus may be adapted to emit the vibrational signal from the transmission member. The apparatus may be adapted to emit the vibrational signal from the transmission member into a structure or environment adjacent or in the vicinity of at least a portion of the transmission member.

The apparatus may be adapted to emit the vibrational signal from substantially the whole of the transmission member.

The apparatus may be adapted to emit the vibrational signal from a portion of, or point on, the transmission member. Whilst the vibrational signal may be emitted from a portion of the transmission member in an appreciable or usable form, in some 1 5 configurations or situations, it will be appreciated that a low or transient emission of signal may occur at other parts of the transmission member.

The apparatus may be adapted to emit the vibrational signal from a plurality of portions of, or points on, the transmission member.

The apparatus may be adapted to emit the vibrational signal from a selectable point on or portion of the transmission member.

The signal generator may be adapted to generate the vibrational signal so as to form a wave front and/or standing wave in the transmission member. The apparatus may be adapted to control interference in the transmission member, which may comprise controlling interference in the transmission member so as to produce constructive interference in a portion, or at a point, of the transmission member.

The apparatus may be adapted to control a position of a wave front and/or the standing wave with respect to the transmission member.

The vibrational signal may comprise at least one and optionally a plurality of signal components. The signal components may comprise components having a plurality of frequencies and/or wavelengths and/or phase angles.

The apparatus may be adapted to control the vibrational signals in order to generate and/or control a location of the wave front of the signal and/or the standing wave, which may comprise controlling the frequency and/or wavelength and/or phase angle and/or relative timing of at least one signal component.

The position at which the signal is emitted by the transmission member may correspond to the position of the standing wave and/or wave front. In this way, the position of the portion of, or point on, the transmission member from which the signal is emitted may be controllable by controlling the frequency and/or phase angle and/or wavelength of the vibrational signal.

The emitted signal may comprise a signal suitable for performing a measurement or analysis.

The structure or environment adjacent the transmission member may comprise at least a portion of geological formation, which may comprise one or more rock strata and/or at least one fluid layer or fluid bearing layer, which may comprise a fluid, for example, oil and/or water.

The structure or environment adjacent the transmission member may comprise at least a portion of an architectural structure such as foundations of a building or other construction, a protective structure or the like.

The apparatus may be adapted to perform seismic analysis.

The vibrational signal may be a seismic signal.

The apparatus may be arranged to perform analysis, such as seismic analysis, of the environment surrounding the transmission member, which may be an environment external to the transmission member and/or an environment internal to the transmission member.

The apparatus may be arranged to perform seismic analysis by emitting a seismic vibrational signal from the transmission member and receiving the signal using the receivers.

The received signals may comprise reflections of the signal and/or a transmitted signal.

The received signal may comprise a signal that has at least partially travelled through the structure and/or environment adjacent the transmission member and/or between the transmission member and the receiver.

The apparatus may be operable to use the received signal to determine at least one material property, which may be a property of the environment or structure in the vicinity of the transmission member, which may be a property of a material on a path between the transmission member and the receiver.

The apparatus may be adapted to determine interfaces between materials.

The apparatus may be adapted to use the signal received by the receivers to generate a geological profile.

The apparatus may be adapted to stimulate and/or agitate the environment or structure surrounding the transmission member, which may comprise emitting the vibrational signal from the transmission member and/or vibrating the transmission member.

According to a second aspect of the present invention, there is provided a measurement system comprising: transmission apparatus according to the first aspect; and at least one receiver for receiving a vibrational signal transmitting via the transmission apparatus or a further vibrational signal arising therefrom.

At least one signal generator of the transmission apparatus and/or receiver may be located or be locatable downhole.

At least one signal generator of the transmission apparatus and/or receiver may be located or be locatable above ground.

The system may comprise a processing module for controlling the vibrational signals generated by the signal generator and/or analysing the signals received by the receiver.

The signal generator and/or receiver may comprise an ultrasonic signal generator and/or receiver. The vibrational signal may comprise sound.

According to a third aspect of the present invention, there is provided a method for transmitting a signal to a subterranean location comprising: applying a vibrational signal to a transmission member; and conveying the signal at least partially along the length of the transmission member to a subterranean location.

The transmission member may be a transmission member of a transmission apparatus of the first embodiment or the system of the second embodiment.

The method may comprise applying the vibrational signal to the transmission member above ground.

The method may comprise emitting the vibrational signal from the transmission member at the subterranean location.

The method may comprise emitting the vibrational signal from the transmission member into a structure or environment adjacent or in the vicinity of at least a portion of the transmission member.

The method may comprise emitting the vibrational signal from substantially the whole of the transmission member.

The method may comprise emitting the vibrational signal from a portion of the transmission member. Whilst the vibrational signal may be emitted from a portion of the transmission member in an appreciable or usable form, in some configurations or situations, it will be appreciated that a lower or transient emission of signal may occur at other points.

The method may comprise emitting the vibrational signal from a selectable portion of the transmission member.

The method may comprise generating the vibrational signal so as to form a wave front and/or standing wave in the transmission member. The method may comprise controlling interference in the transmission member, which may comprise controlling interference in the transmission member so as to produce constructive interference in at least a portion of the transmission member. The method may comprise controlling a position of a wave front and/or the standing in respect of the transmission member.

The method may comprise controlling the vibrational signals in order to generate and/or control a location of the wave front of the signal and/or the standing wave, which may comprise controlling the frequency and/or wavelength and/or phase angle and/or timing of at least one signal component.

The position at which the signal is emitted by the transmission member may correspond to the position of the standing wave and/or wave front. In this way, the position of the signal transmission position may be controllable by controlling the frequency and/or phase angle and/or wavelength of the vibrational signal.

The method may comprise detecting the vibrational signal and/or a signal deriving from the vibrational signal. The method may comprise detecting the signal emitted by the transmission member. The method may comprise detecting the signal emitted by the transmission member after it has passed through at least a portion of the structure or environment adjacent the transmission member.

The emitted signal may be a signal suitable for performing a measurement or analysis.

The method may comprise performing seismic analysis.

The vibrational signal may be a seismic signal.

The signal generator and/or receiver may comprise an ultrasonic signal generator and/or receiver. The vibrational signal may comprise sound. The vibrational signal may comprise an ultrasonic signal.

The method may comprise performing seismic analysis of the environment surrounding the transmission member, which may be an environment external to the transmission member and/or an environment internal to the transmission member.

The method may comprise geological analysis and/or fluid analysis.

The method may comprise stimulating and/or agitating the environment or structure surrounding the transmission member, which may comprise emitting the vibrational signal from the transmission member and/or vibrating the transmission member.

According to a fourth aspect of the invention, there is a method comprising: configuring a signal for transmission to a subterranean transmission member, the signal configured so as to be emitted at a particular location along a subterranean transmission member.

The transmission member may comprise casings, tubulars, or the like. The particular location may be a particular subterranean location.

The method may comprise configuring the signal so as to select the location for emitting a signal (e.g. select the location for emitting along the length of a transmission member).

The method may comprise configuring the signal by using a plurality of signal components. Each signal component may have a particular frequency and/or phase angle such that the signal is emittable at a particular location along a subterranean transmission member. Some or all of the frequencies of the signal components may provided by using particular wavelength(s). Each signal component may differ. The frequency and/or wavelength and/or phase angles may be selected based on material properties of the transmission member.

The method may be for emitting a signal into a structure surrounding a transmission member. An emitted signal may allow for measurement of a structure surrounding a subterranean transmission member. The method may be for providing seismic analysis of a structure (e.g. a structure at a subterranean location).

The method may comprise configuring the signal such that it is emittable at a plurality of particular locations along a subterranean transmission member.

The method may comprise configuring the signal so as to provide a signal front a particular location along a transmission member. A signal front may be a region of increased pressure, such as oscillatory pressure. A signal front may be provided by constructive and/or destructive interference. The method may comprise configuring the signal such that each signal component interacts and/or interferes at a particular location along a transmission member in order to emit a signal at that particular location.

The method may comprise configuring the signal so as to be emittable at a plurality of locations. The method may comprise changing, or varying, one or more of the signal components in order to move a location of an emittable signal.

The method may comprise transmitting the signal in a transmission member (e.g. casing, etc.). The method may comprise receiving an emitted signal having been emitted from the transmission member at a particular location.

The method may comprise receiving an emitted signal having been communicated via the transmission member and structure (e.g. strata, etc.), the structure being at, or adjacent the transmission member. The method may comprise determine the structure (e.g. determining one or more properties of the structure) based on the received emitted signal. The method may comprise using the received signal to determine one or more characteristics of a subterranean structure.

The method may comprise providing a characteristic map of structure by emitting signals at a plurality of location along the transmission member and receiving the emitted signals. The signals may be emitted sequentially at each respective location (e.g. at particular intervals along the transmission member). The signals may be emitted simultaneously at each particular location, or interval.

The structure may be structure at a subterranean location, and may comprise strata, or the like.

According to a fifth aspect of the invention there is a method comprising: using a received signal to determine one or more characteristics of a subterranean structure, the received signal having been emitted from a subterranean transmission member, such as a particular location of a subterranean transmission member, and having been communicated through the subterranean structure.

According to a sixth aspect of the invention, there is provided apparatus comprising: a signal generator for generating a vibrational signal, the signal generator configured for communicating the vibrational signal to a subterranean transmission member for conveying a generated vibrational signal to a subterranean location.

The apparatus may be configured to provide a signal comprising a plurality of signal components. Each component may have a particular frequency and/or phase angle.

According to a seventh aspect, there is provided a computer program configured to provide the any of the features of the third and/or fourth aspects.

The computer program may be provided on a computer readable medium.

The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. For example, it will readily be appreciated that features recited as optional with respect to the first aspect may be additionally or alternatively applicable with respect to any of further aspects, etc., without the need to explicitly and unnecessarily list those various combinations and permutations here.

Corresponding means for performing one or more of the discussed functions are also

within the present disclosure.

Description of the Drawings

Various embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, of which: Figure 1 is a schematic of a transmission system according to an embodiment of the invention; Figure 2(a) is a schematic of a transmission system according to an embodiment of the invention; Figure 2(b) is a schematic of a signal for use with the transmission system of Figure 1 or Figure 2(a); Figure 2(c) is a schematic of a signal generated in a casing of the transmission system of Figure 2(a); Figure 2(d) is a schematic of the signal of Figure 2(c) in the casing; Figure 3 is a schematic of a transmission system according to an embodiment of the invention; Figure 4 is a schematic of a transmission system according to an embodiment of the invention; Figure 5 is a schematic of a transmission system according to an embodiment of the invention; Figure 6 is a schematic of a transmission system according to an embodiment of the invention; and Figure 7 is a schematic of a transmission system according to an embodiment of the invention.

Specific Description

Figure 1 shows transmission apparatus 1 comprising a wellbore casing 5 for insertion into a borehole. The weilbore casing 5 is coupled with a signal generator 20 at an above ground 25 portion of the wellbore casing 5. A plurality of receivers 30 are provided at ground surface 25 locations and spaced apart from the wellbore casing 5.

The signal generators 20 are adapted to apply a vibration signal pulse to the wellbore casing 5. In use, the wellbore casing is partially located in a well bore below the ground surface 25.

The wellbore casing 5 comprises one or more metallic tubular members, as is known in the art.

The signal generator 20 comprises a vibrator, the vibrator having a hydraulic ram unit for driving and actuating an impact member 40. The impact member 40 is shaped and sized to compliment the wellbore casing 5, in order to spread the impact force over an area of the wellbore casing 5, distribute the impact and minimise the possibility of damage to the casing 5. The vibrator 20 is mountable on, or adjacent to, the casing 5 such that the impact member 40 may strike the casing in a controlled manner upon actuation by the hydraulic ram in order to generate a vibrational signal 45. Optionally, the casing 5 is provided with a striking plate (not shown), to receive impact from the vibrator 20 and arranged to transmit vibrational signals to the casing 5, in order to prevent damage to the casing.

The receiver 30 may be any form of suitable seismic receiver known in the art, such as a geophone.

Vibrations applied to the casing 5 by the signal generator 20 may be transmitted along the metallic casing 5 and radiated out into the vicinity of the casing 5. The receivers 30 are operable to detect the signal 45 and any reflections of the signal from geological formations and interfaces. Seismic analysis is performed on the received data using suitable techniques as would be apparent to a person skilled in the art.

In the above example, the vibrations are radiated from substantially the whole length of the casing 5. However, it will be appreciated that the system may be adapted to radiate from one or more discreet portions or points of the casing 5, as shown in Figure 2(a).

For example, the signal generator 20 is operable to produce signals 46 that comprise a plurality of signal components 47a-47h, each component 47a-47h having a different frequency. The signals 46 are applied to the casing by the signal generator 20. The frequency of the components 47a-47h and a phase angle at which they enter the casing 5 can be varied, an example of which is shown in Figure 2(b). In this way a complex signal can be provided. As is shown in Figure 2(c), a signal front 48 can formed, for example, using resonance and/or interference effects, which in this example is movable along the length of the pipeline. This movement may be gradual, or at intervals, which can be regular or irregular. The signal front 48 may be part of a standing wave. The position of the signal front 48 depends on a variety of factors such as the length of the casing 5 and/or timing and/or frequency and/or wavelength and/or phase angle of the signals. By controlling one or more of these properties of the signals, the signal generator 20 is operable to control the position of the maximum of the signal front 48 in the casing 5, as shown in Figure 2(d).

It will be appreciated that in other examples, the apparatus 1 is configured to communicate the signal with the casing at or below (e.g. roughly below, substantially below, immediately below, etc.) the ground 25.

Here, the amplitude of the signal emitted at a controlled portion 3 of the casing 5 can be significantly greater than amplitude of the signal achievable at other portions of the casing 5. In this way, the system 1 is operable to effectively operate as a point emitter from a selectable portion of the casing 5.

It will also be appreciated that the signals may be controlled to produce multiple maxima in the standing wave pattern, for example, through use of second, third and/or subsequent harmonics. In this way, the system 1 is operable as two or more point emitters whose position along the length of the casing 5 is controllable.

By using this standing wave technique, the position of the casing 5 at which the signal is emitted may be controlled to be any position on the casing 5, and without provision of dedicated transmission apparatus. In this way, the complexity and costs of the system are reduced and the number of parts that may potentially fail are minim ised.

The system 1 is described above as being operable as part of a seismic analysis system, for collecting structural information regarding the environment between the casing 5 and the receivers 30. However, the system 1 is operable for other applications that utilise vibrational signals. For example, the system 1 may be operable to produce a vibrational signal, as shown in Figure 2(c), which results in agitation of the casing 5 and/or a structure adjacent the casing 5. This may be useful, for instance, in removing debris from around the casing, freeing up flow of oil, releasing equipment stuck in a bore, or the like. The intensity of the agitation may be enhanced using resonance, constructive interference or standing wave effects, which may be for example, modifications of the techniques for controlling the wavefront position described above.

Furthermore, the position of the agitation position is controllable using the standing wave technique described above. In this way, the agitation can be provided at selected target areas and thereby avoiding agitation to other areas, which may, for example, contain more delicate geological structure or mechanical components.

In the above embodiments, the signal generator 20 is located at the surface 25 and the signal transmitted down the drill casing 5. By allowing the signal generator 20 to be located at the surface 25 and transporting and emitting the signal via the drill casing 5, the signal may be transmitted downhole using existing structures and without having to lower dedicated tools downhole. This may minimise the disturbance to drilling operations.

In an alternate embodiment, as shown in Figure 3, one or more signal generators 20 are located on a downhole section of the drill casing 5. In this way, the signal is propagated from the bottom of the casing 5 upwards, which may be used to obtain an alternate or complimentary data set.

In a further alternate embodiment, as shown in Figure 4, the receivers 30 are located down a second well bore 50. Crosshole seismic survey techniques may then be performed using the received data. In this way, 2D and 3D geological maps can be produced.

Although the technique is described above in relation to applying and transmitting seismic signals via a wellbore casing 5, it will be appreciated that analogous techniques may be used in relation to other signal transmitting structures such as drill pipe, transmission pipe, production pipe, piling or foundation columns or the like.

An example of the application of the above technique to pipelines 55, is shown in Figure 5. In this way, a signal generator 20 at the surface (or optionally on a subterranean section of the pipeline 55) may be used to apply a signal to an existing pipeline 55. One or more receivers 30 are provided at the surface and in the vicinity of the pipeline 55 for detecting the signal and reflections of the signal from geological formations in the vicinity of the pipeline 55. In this way, properties of geological structure in the vicinity of the pipeline 55 may be probed or monitored without having to prepare dedicated bore holes.

Similarly, an example of the application of the technique to piling, foundation or support columns 60 for buildings or other architectural structures 65 such as roads, bridges and the like, is shown in Figure 6. This application may be helpful, as geological formations below the architectural structure 65 may be monitored over time in order to predict adverse geological phenomena, such as weakening of geological formations or subsidence, without having to drill new bores, which may have a detrimental effect on the geology below the architectural structure 65. In architectural structures 65 not having suitable piling columns or the like, one or more dedicated transmission structures may optionally be implanted into the ground under or in the vicinity of the structure to allow seismic data to be regularly collected and monitored.

Furthermore, in addition to probing the environment surrounding a transmission member such as a casing, pipeline, piling or other tubular structure, imparting vibrations to a transmission member, such as a pipeline 70, using a signal generator 20 may be used to determine properties of materials within the transmission member 70, as shown in Figure 7. For example, the density or flow rate of fluid within the transmission member 70 may affect the vibrational properties of the transmission member 70, which may be detected by a suitable detector 30 attached to the transmission member 70, such as a piezoelectric transducer. As the force of vibration required in this application may be less than that required for seismic analysis, signal generators 20 that impart a lower force, such as transducers, including piezoelectric transducers may be used.

A skilled person will appreciate that variations of the disclosed arrangements are possible without departing from the invention. For example, whilst the signal generator 20 is described as a hydraulically driven impact unit, it will be appreciated that other suitable signal generators, such as piezoelectric transducers or electromagnetic transducers, may be used. In addition, although in various specific embodiments, the technique is described as being applied to wellbore casings 5, pipelines 55, 70 and architectural piling 60, it will be appreciated that the technique may also be applied to perform seismic analysis in other applications. Furthermore, whilst the operation of the system as one or more point emitters is described in relation to a seismic apparatus having the signal generator and receivers above ground, it will be appreciated that this technique may also be applicable to other embodiments described above, such as cross-hole analysis, a system having the signal generator and/or one or more receivers downhole and/or pipeline and/or architectural structures. Accordingly the above description of the specific embodiment is made by way of example only and not for the purposes of limitation.

It will be clear to the skilled person that modifications may be made without significant changes to the operation described.

Claims

Claims 1. Transmission apparatus comprising: a signal generator for generating a vibrational signal; a subterranean transmission member configured to convey the vibrational signal generated by the signal generator to a subterranean location.
2. Apparatus according to claim 1, comprising at least one receiver for detecting a vibrational signal and/or signals resulting therefrom.
3. Apparatus according to claim 1, wherein the transmission member comprises at least one of: a borehole casing; drill pipe; transition pipe; production pipe.
4. Apparatus according to any of the preceding claims, configured to emit a vibrational signal substantially from a portion of, or point on, the transmission member.
5. Apparatus according to any of the claims 1 to 3, the apparatus configured to emit a vibrational signal substantially from a plurality of portions of, or points on, the transmission member.
6. Apparatus according to any of the preceding claims adapted to emit a vibrational signal from a selectable point on, or portion of, the transmission member.
7. Apparatus according to any of the preceding claims, wherein the signal generator is adapted to generate a vibrational signal so as to form a wave front and/or standing wave in the transmission member.
8. Apparatus according to claim 7 adapted to control a position of a wave front and/or a standing wave with respect to the transmission member.
9. Apparatus according to any of the preceding claims, wherein the apparatus is adapted to control interference in the transmission member so as to produce constructive interference in a portion, or at a point, of the transmission member.
10. Apparatus according to any of the preceding claims, wherein the apparatus is configured to provide vibrational signals comprising a plurality of signal components, each signal component having particular frequencies and/or wavelengths and/or phase angles.
11. Apparatus according to any of the preceding claims, wherein structure or environment adjacent the transmission member comprises at least a portion of geological formation, such as rock strata and/or at least one fluid layer or fluid bearing layer, such as oil and/or gas.
12. Apparatus according to any of the preceding claims, wherein the apparatus is arranged to perform seismic analysis by emitting a seismic vibrational signal from the transmission member and receiving a signal using receivers.
13. A measurement system comprising: transmission apparatus according to any of the claims 1 to 12; and at least one receiver for receiving a vibrational signal transmitting via the transmission apparatus or a further vibrational signal arising therefrom.
14. A system according to claim 13, wherein at least one signal generator of the transmission apparatus and/or receiver is located or locatable above ground.
15. A method for transmitting a signal to a subterranean location comprising: applying a vibrational signal to a transmission member; and conveying the signal at least partially along the length of the transmission member to a subterranean location.
16. The method according to claim 15 comprising applying the vibrational signal to the transmission member above ground.
17. The method according to claim 15 or 16 comprise emitting the vibrational signal from a selectable portion of the transmission member.
18. The method according to any of the claims 15 to 17, comprising generating the vibrational signal so as to form a wave front and/or standing wave in the transmission member.
19. The method according to any of the claims 15 to 18 comprising controlling interference in the transmission member so as to produce constructive interference in at least a portion of the transmission member.
20. The method according to any of the claims 15 to 19 wherein the vibrational signal comprises a plurality of signal components, each signal component comprising a particular frequency and/or wavelength and/or phase angle.
21. The method according to claim 20, comprising controlling the vibrational signals in order to generate and/or control a location of a wave front of the signal and/or a standing wave by controlling the frequency and/or wavelength and/or phase angle and/or timing of at least one signal component.
22. The method according to any of the claims 15 to 21 comprising detecting the signal emitted by the transmission member after it has passed through at least a portion of the structure or environment adjacent the transmission member.
23. The method according to any of the claims 15 to 22 comprising performing seismic analysis.
24. Apparatus substantially as described herein, with reference to the accompanying figures.
25. Methods substantially as described herein, with reference to the accompanying figures.