WO2009099332A1

WO2009099332A1 - Data communication link

Info

Publication number: WO2009099332A1
Application number: PCT/NO2008/000044
Authority: WO
Inventors: Terje Lennart Lie
Original assignee: Tecwel As
Priority date: 2008-02-07
Filing date: 2008-02-07
Publication date: 2009-08-13

Abstract

There is provided a data communication link (120) for coupling a first apparatus (100) in data communication with a second apparatus (110). The first apparatus (110) and the communication link (120) are spatially moved in operation relative to the second apparatus (110). Moreover, the communication link (120) is operable to provide mechanical support for the first apparatus (100). The communication link (120) further includes one or more optical fibre waveguides (430) for coupling the first apparatus (100) in data communication with the second apparatus (110), wherein the one or more optical fibre waveguides (430) are disposed in a spatial formation in relation to the communication link (120) which at least partially isolates the one or more optical fibre waveguides (430) from mechanical stresses when the first apparatus (100) is moved in operation relative to the second apparatus (110). The communication link (120) is of advantage in that the one or more optical fibre waveguides (430) are operable to provide considerable communication bandwidth, for example for enabling very rapid real-time inspection and monitoring of boreholes (10), despite the communication link (120) being potentially exposed to harsh conditions.

Description

DATA COMMUNICATION LINK

Field of the invention

The present invention relates to data communication links, for example to data communication links for use in monitoring systems operable to monitor boreholes in connection with oil and/or gas exploration and/or extraction. Moreover, the present invention is concerned with methods of communicating data via data communication links, for example when monitoring boreholes in connection with oil and/or gas exploration and/or extraction.

Background of the invention

Referring to Figure 1 , a borehole indicated generally by 10 is formed in a region of ground 20 during gas and/or oil exploration. In an event that deposits of oil and/or gas are found substantially at an end of the borehole 10, the borehole 10 provides a route by which the oil and/or gas deposits are subsequently extracted. The borehole 10 itself is often several kilometres in depth and filled with liquid, for example with drilling mud when executing boring operations during oil and/or gas exploration; in such circumstances, a pressure at the end of the borehole 10 can be considerable, for example in an order approaching 1000 Bar. Moreover, on account of geothermal heating in lower strata of the region of ground 20, an ambient temperature within the borehole 10 is susceptible to approaching 150 ⁰C. Furthermore, the region of ground 20 is potentially itself porous and susceptible to fragmenting into quantities of gravel, sand and similar types of particles.

In order to successfully drill the borehole 10, it is conventional practice to line the borehole 10 along at least part of its length with one or more liner tubes 3Oa₁ 30b, 3Oc₁ 3Od. The liner tubes 30a to 3Od are operable, for example, to prevent water and other contaminants penetrating into the borehole 10 at upper regions of the ground 20. For reasons of economy, the borehole 10 is drilled to have a diameter sufficient for accommodating drilling and/or extraction apparatus 50 as well as providing for gas and/or oil extraction; the borehole 10 is not made to be unnecessarily large because drilling time to form the borehole 10 and associated costs would thereby be unnecessarily increased. In practice, the liner tube 30a is conveniently in an order of 200 mm in diameter. Many practical problems are often encountered when drilling the borehole 10; moreover, subsequent problems can arise when extracting oil and/or gas via the borehole 10. An example of such problems is that the liner tube 30a develops one or more leakage holes. The one or more leakage holes are susceptible to enabling water present in the region of ground 20 surrounding the borehole 10 to penetrate into a central region of the liner tube 30a. Moreover, the liner tube 30a itself is potentially susceptible to becoming obstructed with deposits transported up the liner tube 30a. Furthermore, the one or more leakage holes are susceptible to producing one or more paths through which oil and/or gas present within the liner tube 30a escapes into a region between an external surface of the liner tube 30a and the ground 20, such leakage potentially reducing a yield of oil and/or gas achievable from the borehole 10. When aforementioned one or more leakage holes and/or obstructions occur many kilometres underground, it is often very difficult to know at an above-ground region 40 what precisely is happening in the region of ground 20 in respect of the borehole 10. In view of the borehole 10 potentially costing many millions of dollars (US dollars) to drill and prepare for subsequent oil and/or gas extraction, reliable and efficient detection of defects arising in the borehole 10 is of considerable commercial importance. However, physical conditions within the borehole 10, for example in lower regions thereof, are very hostile on account of abrasive particles present, high ambient temperatures in an order of +150 ⁰C, high pressure approaching 1000 Bar and corrosive and/or penetrative fluids present in the borehole 10.

Various types of down-borehole tools are known. Referring to Figure 2, certain implementations of these tools each comprise a probe assembly 100 operatively inserted into the borehole 10 to be monitored, a data processing arrangement 110 in an above- ground region, and a flexible communication link 120 mutually coupling together the data processing arrangement 110 and the probe assembly 100. In operation, the probe assembly 100 senses one or more parameters within the borehole 10, for example temperature and/or pressure therein, using one or more sensors to generate one or more sensor signals which are then communicated via the communication link 120 to the data processing arrangement 110. At the data processing arrangement 110, the one or more sensor signals are at least one of: displayed on a display 130 in real-time, recorded in a data memory or data base 140 for subsequent analysis. Implementations of the tools, for example as illustrated in Figure 2, optionally enable real-time monitoring of boreholes to be achieved. A sliding fluid seal (not shown in Figure 2) is formed at the top of borehole 10 around a cable implementing the communication link 120 so as to seal the borehole 10 in an event that the borehole 10 is operating under excess pressure, for example as a result the borehole 10 intercepting a pressurized gas deposit in the ground 20. Alternatively, as illustrated in Figure 3, other implementations of these tools each comprise the probe assembly 100 which additionally includes a semiconductor data memory 150 locally therein for recording signals generated by one or more sensors of the probe assembly 100 in a first step S1 when the probe assembly 100 is employed to characterize the borehole 10. In such an implementation, the probe assembly 100 is operable to function as an autonomous apparatus which is moved blindly within a borehole 10 to collect data therefrom. In a step S2, the probe assembly 100 is then subsequently extracted from the borehole 10 to the above-ground region 40, whereat the probe assembly 100 is coupled to its associated data processing arrangement 110 for downloading data, as denoted by 160, from the data memory 150 of the probe assembly 100 to the data processing arrangement 110.

A technical problem is encountered when the probe assembly 100 in Figure 2 is employed to spatially inspect, for example by employing one or more optical cameras, an inside of a borehole 10 on account of a considerable amount of corresponding data which is generated. Measurements such as one or more temperatures within the borehole 10, one or more pressures within the borehole 10, and phase composition of fluid within the borehole 10 generally generate significantly less corresponding data in comparison to executing spatial inspection. In consequence, when spatial inspection is to be performed, severe technical demands are placed upon communication performance of the aforesaid communication link 120 in respect of data bandwidth or upon data memory capacity which must be provided robustly within the probe assembly 100 when operated in an autonomous manner.

It is thus desirable to be able to spatially inspect, in real-time, an inside of a borehole by using a probe assembly. On detection of a defect such as a leakage hole, it is desirable for the probe assembly to be maintained in a locality of the defect for a longer period to sample an enhanced amount of data, thereby enabling the defect to be identified and characterized to a greater degree of certainty. By identifying and characterizing one or more defects to a greater degree of certainty, repair or mitigation of the one or more defects are susceptible to being implemented in a more efficient and selective manner.

A technical problem which the present invention addresses is to provide an improved approach to implementing the communication link 120, so that the link 120 is capable of providing data communication rates which are susceptible to at least partially resolving conflicting constraints of, firstly, real-time monitoring of a borehole 10 and, secondly, providing spatial inspection of the borehole 10. Summary of the invention

An object of the present invention is to provide an improved communication link for use in monitoring systems, the communication link being operable to communicate data at a rate for accommodating real-time monitoring of boreholes whilst also enabling spatial inspection boreholes to be achieved.

According to a first aspect of the invention, there is provided a data communication link as claimed in appended claim 1 : there is provided a data communication link for coupling a first apparatus in data communication with a second apparatus wherein the first apparatus and the communication link are spatially moved in operation relative to the second apparatus, the communication link being operable to provide mechanical support for the first apparatus,

characterized in that

the communication link includes one or more optical fibre waveguides for coupling the first apparatus in data communication with the second apparatus, and the one or more optical fibre waveguides are disposed in a spatial formation in relation to the communication link which at least partially isolates the one or more optical fibre waveguides from mechanical stresses when the first apparatus is moved in operation relative to the second apparatus.

The invention is of advantage in that the one or more optical fibre waveguides are susceptible to providing an enhanced communication bandwidth in comparison to employing solely twisted pairs of electrical wires for providing data communication.

Optionally, the communication link has an uninterrupted length in a range of 1 km to 10 km. Such a relatively long uninterrupted length enables communication to, for example, in- borehole monitoring apparatus or deep-sea submerged apparatus operating at extremes of temperature and pressure.

Optionally, for example when the first apparatus is deployed in a borehole, the data communication link is adapted to be capable of supporting the first apparatus suspended on the communication link substantially vertically therefrom.

Optionally, in the data communication link, the formation of the one or more optical fibre waveguides includes at least one helical formation which is flexible in its longitudinal and lateral directions without substantially axially straining the one or more optical fibre waveguides. Employing such a helical formation, or an alternative formation operable to perform a similar strain relieving function to that provided by the helical formation, assists to reduce a risk of the one or more optical fibre waveguides fracturing in use when the communication link is subjected to mechanical strain.

Optionally, the data communication link includes an exterior cladding for defining at least one void within the exterior cladding, the at least one void being operable to accommodate the one or more optical fibre waveguides, and the at least one void being filled with a liquid and/or gel for mechanical supporting the one or more optical fibre waveguides in a stress- isolated manner. Inclusion of the liquid and/or gel is of benefit in that the communication link is not easily compressed and thereby deformed when subject to externally elevated pressure, for example when the first apparatus is operated down a borehole with a high ambient pressure potentially approaching 1000 Bar.

More optionally, the data communication link includes at least one structural core within the at least one void for providing the data communication link with axial rigidity for bearing a weight of the first apparatus in operation. Beneficially, the one or more optical waveguides are disposed in a helical manner around the at least one structural core. By employing a central structural core, the one or more optical fibre waveguides are automatically obliged to assume an at least partially helical formation around the structural core for stress-relieving purposes. Alternatively, the one or more optical waveguides are enclosed within the structural core, for example when implemented in a tubular manner, for example as a peripheral cladding.

More optionally, in the data communication link, the one or more optical fibre waveguides are attached at spatially periodic intervals along the communication link for preventing the one or more optical fibre waveguides slumping within the at least one void when in operation.

Optionally, the data communication link is employed for implementing a monitoring system: the data communication link in combination with the first and second apparatus constitute a monitoring system for monitoring within a borehole, the first apparatus being operable to function as a probe assembly operable to be moved within the borehole for sensing one or more physical parameters therein, the second apparatus being operable to function as a data processing arrangement located outside the borehole, and the data communication link being operable to convey sensor data indicative of the one or more physical parameters from the probe assembly to the data processing arrangement for subsequent processing and display and/or recording in data memory, wherein

(a) the probe assembly includes one or more sensors for spatially monitoring within the borehole and generating corresponding sensor signals;

(b) the probe assembly includes a digital signal processor for executing preliminary processing of the sensor signals to generate corresponding intermediately processed signals for communication via the data communication link to the data processing arrangement; (c) the data processing arrangement is operable to receive the intermediately processed signals and to perform further processing on the intermediately processed signals to generate output data for presentation and/or for recording in a data memory arrangement.

Optionally, the system is operable to generate the output data for presentation in real-time when the probe assembly is moved within the borehole.

Optionally, the system is operable in at least one of first and second modes, wherein:

(a) the first mode results in the system passively sensing noise sources present in the borehole generating radiation for sensing at the one or more sensors; and

(b) the second mode results in the system actively emitting radiation into the borehole and receiving at the one or more sensors corresponding reflected radiation from a region in and/or around the borehole for generating the sensor signals.

More optionally, the system is operable to be dynamically reconfigurable between the first and second modes when the probe assembly is being moved in operation within the borehole.

More optionally, with reference to the data communication link, the system is operable to communicate data bi-directionally between the data processing arrangement and the probe assembly, wherein the digital signal processor of the probe assembly is operable to being reconfigured between a first function of general sensing around in a region of the borehole in a vicinity of the probe assembly, and a second function of specific sensing in a sub-region of the region of the borehole in a vicinity of the probe assembly.

More optionally, the data communication link includes one or more twisted-wire pairs including material insulation and copper electric conductors embedded within the plastics material. The material insulation is beneficially plastics material insulation, although other types of insulation such as ceramic beads surrounding the conductors are feasible to employ.

Optionally, in relation to the data communication link, the data processing arrangement is located in operation remotely from the probe assembly, the data processing arrangement providing an interface for one or more users to control in real-time operation of the probe assembly, and for generating graphical images for presentation on one or more displays to the one or more users, the graphical images being representative of spatial features present within and/or around the borehole in a vicinity of the probe assembly.

Features of the invention are susceptible to being combined in any combination without departing from the scope of the invention as defined by the appended claims.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

Figure 1 is an illustration of a borehole furnished with a liner tube arrangement;

Figure 2 is a schematic illustration of a down-borehole probe arrangement for sensing physical parameters within a borehole and generating corresponding signals for communicating in real-time to a data processing arrangement remote from the borehole;

Figure 3 is a schematic illustration of a down-borehole probe arrangement for sensing physical parameters within a borehole and generating corresponding signals for data-logging locally within a probe assembly, for subsequent down-loading to a data processing arrangement when the probe assembly has been extracted from the borehole;

Figure 4 is a schematic illustration of a monitoring system for monitoring down boreholes;

Figure 5 is a schematic illustration of an optical waveguide assembly surrounded by a plastics material sleeve; Figure 6a is an illustration of a practical implementation of a data communication link for use with the system of Figure 2, the communication link including one or more optical waveguide assemblies as illustrated in Figure 5;

Figure 6b is an illustration of anchoring a helical-formed optical fibre waveguide assembly at periodic spatial intervals along a twisted-wire pair to prevent the fibre waveguide slumping down whilst also enabling the fibre waveguide to flex to accommodate stress;

Figure 6c is an illustration of anchoring a helical-formed optical fibre waveguide assembly and a twisted-wire pair at periodic spatial intervals along a structural core to prevent the fibre waveguide slumping down whilst also enabling the fibre waveguide to flex to accommodate stress;

Figure 7 is a more detailed illustration of component parts of the system in Figure 4, the components including a transducer array for receiving ultrasonic radiation from boreholes, and optionally for also interrogating such boreholes;

Figure 8 is an illustration of polar sensing angles of the transducer array of Figure 7;

Figures 9a and 9b are illustrations of signals present in the system of Figure 4 when in operation; and

Figure 10 is a flow diagram of signal processing operations executed within the system of Figure 4.

Description of embodiments of the invention

In overview, embodiments of the present invention include principal features akin to Figure 2, namely:

(a) a probe assembly 100 for spatially sensing within a borehole 10;

(b) a communication link 120 whose associated cladding 200 and/or structural core 210 are operable to mechanically support the probe assembly 100 when deployed within the borehole 10, and whose signal-guiding components are operable to convey signals transmitted from the probe assembly 100, and to convey control signals to the probe assembly 100; (c) a data processing arrangement 110 coupled via the communication link 120 to the probe assembly 100, the data processing arrangement 110 being operable to receive signals from the probe assembly 100 and to send instruction data to the probe assembly 100.

The probe assembly 100, the communication link 120 and the data processing arrangement 110 constitute a system as denoted by 300 in Figure 4.

In Figure 4, the system 300 is distinguished from subject matter presented and described in respect of Figure 2 in that:

(a) the probe assembly 100 includes a transducer array 320 coupled via a digital signal processor (DSP) 310 and then via the communication link 120 to the data processing arrangement 110; and (b) the data processing arrangement 110 includes a data processor 330 which is operable to receive data from the probe assembly 100 via the communication link 120; the data processor 330 is also operable to send control commands via the communication link 120 to reconfigure the digital signal processor (DSP) 330 in response to signals generated in operation by the transducer array 320. The system 300 is optionally susceptible to operating in a first passive mode and in a second active mode.

In the first passive mode, physical signals 350 that are generated in an environment of the borehole 10 propagate within the borehole 10 and are eventually received by the transducer array 320. The transducer array 320 generates corresponding electrical signals 360 which are conveyed to the digital signal processor (DSP) 310. Thereafter, the digital signal processor 310 performs primary processing of the electrical signals 360 to generate corresponding intermediate processed signals 370 which are communicated via the communication link 120 to the data processor 330. The data processor 330 then performs secondary processing on the intermediate processed signals 370 to generate corresponding output data. Moreover, the data processor 330 is optionally operable to store at least part of the intermediate processed signals 370 in the data memory 140. Moreover, the data processor 330 is optionally operable to store at least part of the output data in the data memory 140. Moreover, the data processor 330 is operable to present the output data on the display 130. In the second active mode, the data processor 330 is operable to send control signals 380 to the digital signal processor (DSP) 310 to drive the transducer array 320 with a drive signal 390 to cause the transducer array 320 to emit radiation 400 into the borehole 10. Optionally, the emitted radiation 400 is pulsed radiation comprising pulses punctuated by quiet periods; portions of the radiation 400 reflected from structures within and in near proximity to the borehole 10 are received back at the transducer array 320 as the physical signals 350 to generate the aforesaid electrical signals 360 which are subsequently processed in the digital signal processor 310 to subsequently generate the intermediate processed signals 370. The data processor 330 then performs secondary processing of the intermediate processed signals 370 to generate corresponding output data. Moreover, the data processor 330 is optionally operable to store at least part of the intermediate processed signals 370 in the data memory 140. Moreover, the data processor 330 is optionally operable to store at least part of the output data in the data memory 140. Moreover, the data processor 330 is operable to present the output data on the display 130.

The system 300 is optionally designed to be able to switch dynamically between the aforementioned first passive mode and second active mode. Alternatively, the system 300 is optionally designed to function only in the first passive mode. Yet alternatively, the system 300 is optionally designed to function only in the second active mode.

It will be appreciated from the foregoing that the system 300 is optionally operable to distribute data processing activities between the digital signal processor 310 and the data processor 330. Alternatively, the signals 360 generated by the transducer array 320 are streamed in substantially unprocessed form directly from the transducer array 320 via the digital signal processor 310 and subsequently as the data signal 370 via the communication link 120 to the data processing arrangement 110 for at least one of analysis, presentation and recording as one or more data archives in the data memory 140. Such streaming is beneficially achieved by implementing the communication link 120 in a manner capable of supporting relatively high data communication rates of several million megabytes per second or greater; such high data communication rates are feasible to achieve when the communication link 120 includes one or more optical fibre waveguides therein for use in conveying data in an optical format therethrough. Use of one or more optical-fibre waveguides for the communication link 120 is an important feature of the present invention. Optical fibre waveguides are known in contemporary telecommunications industries, wherein such waveguides in a mono-mode manner are susceptible to supporting fifty wavelength division multiplexed (WDM) data channels, each channel having a bandwidth of 50 GHz. The system 300 has been described in overview in the foregoing. However, before describing component parts of the system 300 in greater detail, other issues regarding the probe assembly 100 and the communication link 120 will next be elucidated. The borehole 10 is often at a pressure P which, in certain circumstances, can approach 1000 Bar. For example, the borehole 10 can often be many kilometres deep and filled with water, or with an abrasive multiphase mixture including oil, water and rock particles. When the probe assembly 100 is lowered into the borehole 10 filled with liquid to a depth of a kilometre or more, the pressure P acting upon the probe assembly 100 as well as the cladding 200 of the communication link 120 is potentially enormous. In such circumstances, a leakage hole in the liner tube 30a with many Bar differential pressure between a first region outside the liner tube 30a to a second region inside the liner tube 30a can result in a considerable flow of fluid between the first and second regions causing generation of acoustic radiation from a vicinity of the leakage hole. It is also feasible in certain situations that the borehole 10 is filled with gas at a high pressure approaching 1000 Bar on account of the borehole 10 intercepting a pressurized gas reservoir. Such high pressures in the borehole 10 risk forcing gas or liquid to ingress into an inside region of the probe assembly 100 and can also force gas into a polymeric material from which the cladding 200 is fabricated. For example, if the cladding 200 fabricated from polymeric material is suddenly depressurized from a high pressure of 1000 Bar pressure to nominal atmospheric pressure of 1 Bar (760 mm Hg), gas forced by such a high pressure to ingress into interstitial spaces within the polymeric material can suddenly cause the polymeric material to expand to form a foam-like material with microvoids therein, potentially causing permanent damage to the polymeric material as well as subjecting component parts housed within the cladding 200 to considerable mechanical stress. Optionally, as illustrated in Figure 1 , the inner liner tube 30a includes a sliding seal around a top region thereof as illustrated in Figure 1 to seal against the communication link 120 when the probe assembly 100 is employed within the borehole 10 when the borehole 10 is required in operation to exhibit an elevated pressure relative to ambient atmospheric pressure of nominally substantially 1 Bar (760 mm Hg). Although use of a polymeric material to form the cladding 200 to clad the communication link 120 is in many situations unavoidable, a casing of the probe assembly 100 is beneficially fabricated from a robust material which is resistant to abrasion and corrosion, for example fabricated from machined solid stainless steel material or seamless stainless steel tubing. Additionally, or alternatively, the casing of the probe assembly 100 is fabricated is fabricated, at least in part, from more exotic materials such as robust polymer materials, silicon carbide, silicon nitride, ceramic materials and similar. The transducer array 320 is beneficially implemented as an array of piezo-electric elements, for example fabricated from lead zirconate titanate (PZT) or similar strongly piezo-electric material. In operation, the transducer array 320 is susceptible to being excited by the drive signals 390 applied thereto to generate the radiation 400 as ultrasonic radiation, and also susceptible to receive the radiation 350 as reflected ultrasonic radiation for generating aforesaid electrical signals 360. Piezo-electric material of the transducer array 320 is optionally directly in physical contact with fluid present within the borehole 10 in order to obtain most efficient coupling of ultrasonic radiation. Alternatively, the transducer array 320 is operable to communicate with the interior region of the borehole 10 via one or more protective interfacing windows.

On account of the borehole 10 being potentially heated up to a temperature T approaching +150 ⁰C by geothermal energy in rock formations surrounding the borehole 10, there is a potentially severe limitation regarding power dissipation which can occur within the probe assembly 100 when in operation. When the probe assembly 100 is operating pursuant to the aforesaid second active mode, generating the drive signals 390 in drive amplifiers is susceptible to resulting in electrical power dissipation within the probe assembly 100. Moreover, data processing occurring in operation in the digital signal processor (DSP) 310 is susceptible to causing additional dissipation in both the first passive mode and in the second active mode. The data processing arrangement 110 is therefore beneficially implemented using semiconductor devices based upon CMOS technology which are not vulnerable to thermal runaway as a result of increase in minority-carrier currents therein during operation. Similarly, the drive amplifiers employed within the probe assembly 100 to provide the drive signals 390 are beneficially also based upon MOSFET devices which are capable of operating at elevated temperatures approaching 200 ⁰C without suffering thermal runaway.

On account of the liner tube 30a having an inside diameter in an order of 200 mm, the probe assembly 100 is manufactured to have a diameter in a range of 100 mm to 180 mm, more preferably to have a diameter of substantially 150 mm. Moreover, the cladding 200 and/or the optional associated structural core 210 of the communication link 120 is required to be strong enough to bear a weight of the probe assembly 100 when lowered kilometres down the borehole 10 including a weight of the cladding 200 and/or the structural core 210 itself. If the cladding 200 is relatively large in diameter, for example 25 mm or greater in diameter, it becomes too massive and is difficult to bend around pulleys of feed hoists above the borehole 10. Conversely, if the cladding 200 is relatively small in diameter, for example 4 mm or smaller in diameter, the cladding 200 is susceptible to becoming snarled on projections forming in operation on an inside-facing surface of the borehole 10 and is potentially unable to reliably bear its own weight and potentially also the weight of the probe assembly 100. In practice, with modern advanced cladding materials, for example by using one or more of carbon fibres, Kevlar and advanced nano-material fibres, it is feasible to provide sufficient robustness for the cladding 200 when the cladding has a diameter in a range of 5 mm to 15 mm, more preferable substantially in a range of 6 mm to10 mm, and most preferably substantially 8 mm.

In operation, the cladding 200 and/or the optional core 210 are susceptible to exhibiting strain when a stress arising from weight is applied thereto. The communication link 120 is optionally implemented to include one or more electrical pairs of electrically-conducting wires which are twisted together, namely twisted-wire pairs. The wires each include material insulation which is capable of stretching or moving under mechanical stress; the material insulation is beneficially implemented as plastics material insulation and/or ceramic insulating beads surrounding the wires. Moreover, each wire includes copper conductors therein for conveying electrical signals; copper is a ductile metal of relatively low weight, of high electrical conductivity, of relatively high resistance to oxidative corrosion, and is less prone to work hardening when subjected to repeated bending cycles. At each end of the communication link 120 are optionally included Ethernet line drivers matched to a transmission-line impedance of the one or more twisted-wire pairs of the communication link 120; data is thereby bi-directionally communicated in operation along the communication link 120 which is capable of enabling a data flow of several hundred kilobytes (kbytes) per second to be supported along the one or more twisted-wire pairs. It is however to be bourn in mind that conventional real-time video streaming often requires a communication bandwidth at least in the order of MHz. In order that the system 300 is capable of providing real-time video-rate three-dimensional monitoring of the borehole 10 in operation, the communication link 120 is arranged to include one or more glass optical-fibre waveguides therein. Moreover, the digital signal processor 310 is provided with optical drivers and the data processing arrangement 110 is correspondingly provided with optical receivers for interfacing to the one or more optical-fibre waveguides of the communication link 120.

Referring to Figure 5, there is shown a section of optical fibre waveguide assembly indicated generally by 410. The waveguide assembly 410 comprises an elongate optical glass or quartz waveguide 430 surrounded by a correspondingly elongate outer mechanical sleeve 420. The glass waveguide 430 is optionally a monomode waveguide including a central core having a first optical refractive index and diameter of circa 10 μm, and a cladding region having a second optical refractive index and a diameter of circa 100 μm surrounding the central core; alternatively, the glass or quartz waveguide 430 is a multimode optical fibre waveguide. In operation, optical radiation modulated with data launched at a shallow angle relative to a central axis 450 of the waveguide 430 is confined by optical internal reflection substantially within the core and propagates therealong with a power loss of circa 1 dB/km or less. As well known from contemporary telecommunications industry, similar types of optical fibre waveguides are susceptible to conveying data at data rates of ten's of Gigabytes/second by way of wideband wavelength-division-multiplexing (WDM).

Beneficially, the mechanical sleeve 420 is fabricated from a substantially optically transparent polymer material, for example from a polyacrylate plastics material, a polycarbonate plastics material or similar. Moreover, the mechanical sleeve 420 has a substantially circular cross-sectional profile as illustrated, although other cross-sectional profiles such as oval cross-sectional profiles are also feasible. Optionally, the mechanical sleeve 420 is provided with additional layers of protection, for example using plastics materials, rubber or similar. Optionally, the mechanical sleeve 420 is surrounded by ceramic and/or metal beads for providing additional protection.

Superficially, a personal skilled in designing monitoring apparatus for monitoring boreholes, incorporation of one or more of the waveguide assemblies 410 into the communication link 120 would seem a technically impossible task on account of issues of robustness and reliability. In contemporary telecommunications systems, optical fibre waveguides are carefully installed along communication routes, for example in underground conduits, and are left mechanically undisturbed for years during their service life. The one or more optical fibre waveguide assemblies 430 optionally included within the communication link 120 are, in contradistinction, subjected to potentially stressful movements which, without appropriate design, would result in the one or more waveguide assemblies 430 potentially fracturing and causing the system 300 to malfunction during deployment. From a German published patent application, DE 43 36 643 A1 (Siemens), it is known to house polymer optical fibre waveguides loosely within a gas-filled metal pipe with external protection therearound to provide a short-distance communication connection link; however, such an implementation of communication connection link is completely impractical for use in harsh environments where extreme temperatures and external pressures are to be tolerated, for example when the probe assembly 100 is deployed in the borehole 10.

Pursuant to the present invention, it is surprisingly found possible to include one or more optical fibre waveguides within the communication link 120 in a manner which is susceptible to enabling the communication link 120 to provide reliable service despite arduous operating conditions encountered in operation in the borehole 10. Referring again to Figure 5, it is known to include optical fibres wound onto spools of circa 2 cm diameter in fibre-optical gyroscopes (FOGs) employed in missile and aircraft inertial guidance systems; for example, use of optical fibre waveguides to construct a fibre-optical gyroscope is described in a published international PCT patent application no. PCT/US2003/026634 (WO 2004/020949A1) (Northrop Grumman Corp.). In such gyroscopes, the optical fibres wound onto spools form Mach-Zehnder optical interferometers which are required to exhibit very high optical stability in arduous conditions of vibration and acceleration, for example during missile launch and/or during turbulent missile flight trajectory. The mechanical sleeve 420 and the glass waveguide assembly 430 in Figure 5 are thus well able to cope with repeated lateral flexure denoted by 440. Moreover, rotational flexure as denoted an arrow 445 about a longitudinal axis 450 of the waveguide assembly 430 is also well tolerated by the mechanical sleeve 420 and the glass or quartz waveguide assembly 430. However, the waveguide assembly 430 is easily damaged by longitudinal stress being repeatedly applied thereto as denoted by an arrow 455. Such repeated longitudinal stress is susceptible to causing the waveguide assembly 430 to develop microscopic cracks and fractures which propagate transversely across the waveguide assembly 430 relative to the longitudinal axis 450. An occurrence of a few such microscopic cracks does not automatically cause the waveguide 430 to malfunction but causes optical attenuation within the waveguide assembly 430 to increase as well as causing optical reflections back along the waveguide assembly 430 to increase which diminishes a useable data bandwidth of the communication link 120 when including and utilizing one or more of the waveguide assemblies 430. However, gross fracture of the waveguide assembly 430 is also potentially susceptible to occurring when the waveguide assembly 430 is subjected to excessive longitudinal stress. It is not unknown, for example when the borehole 10 is filled with gas, for the probe assembly 100 to be observed in operation to bounce up and down within the borehole 10 when suspended therein by a length of several hundred metres or even kilometres of the cladding 200 and subjected to an abrupt movement, for example freeing itself from a protruding obstruction present within the borehole 10.

The present invention relates to the communication link 120 including one or more optical waveguide assemblies 430 therein for enabling a data communication bandwidth well in excess of 10's of Mbytes/second between the probe assembly 100 and the data processing arrangement 110 to be achieved, thereby enabling real-time three-dimensional monitoring of an inside of the borehole 10 to be achieved, for example without a need for data compression to be applied at the digital signal processor 310 of the probe assembly 100. The probe assembly 100 and the data processing arrangement 110 include optical drivers and receivers for providing in operation data transfer via the communication link 120 when the system is in use in the borehole 10.

In order to provide its advantages in respect of one or more waveguide assemblies 430 employed to implement the communication link 120, the one or more waveguide assemblies 430 are housed in the cladding 200 in a manner which prevents the one or more waveguides 430 from being subjected to longitudinal stress, namely in a direction along the arrow 455 in Figure 5.

Referring to Figure 6a, there is shown an implementation of a section of the communication link 120. The communication link 120 includes the aforementioned cladding 200 which is optionally integrally reinforced as denoted by 205 with at least one of:

(a) metal strengthening elements such as metal mesh, metal rings;

(b) carbon fibre mesh; and (c) Kevlar or similar woven flexible material mesh.

Such reinforcements are beneficially integrally molded into polymer plastics material employed to fabricate the cladding 200. The cladding 200 is beneficially provided as continuously-molded tubing in one piece to reach from the data processing arrangement 110 to the probe assembly 100, thereby providing a smooth outer surface to which a slidable fluid seal is susceptible to being implemented, for example when the borehole 10 is under considerable pressure even at its exit at ground level or sea-bed level. Plastics material employed to fabricate the cladding 200 is beneficially a radiation-hardened cross-linked flexible polymer of a type similar to that employed in high-tension electrical cables. Alternatively, the cladding 200 is fabricated from a reinforced nylon polymer. Alternatively, the cladding 200 is fabricated from a flexible polypropylene plastics material, optionally radiation-hardened polypropylene plastics material. Yet alternatively, the cladding 200 is fabricated from a polyamide plastics material which is optionally radiation-hardened. Furthermore, the cladding 200 is optionally fabricated from a mixture of plastics materials.

Optionally, the aforesaid structural core 210 included within the cladding 200. Optionally, the cladding 200 then functions at least in part as a structural support. The structural core 210 is beneficially fabricated from one or more strands of metal collected together into a bundle, for example high-tensile steel, copper, stainless steel. Optionally, the bundle of metal wires is a mixture of mutually different metals, for example a mixture of copper strands and stainless- steel strands. Alternatively, the aforesaid structural core 210 is fabricated from carbon fibres, Kevlar fibres, robust nanofibres, or similar high-strength non-metallic materials. Optionally, the structural core 210 comprises a mixture of such metal strands and such strands of non- metallic materials. A void 460 is provided between the cladding 200 and the structural core 210 for optionally accommodating one or more twisted pairs of wire 462 and accommodating one of more optical waveguide assemblies 410; the twisted pairs of wires 462 and/or optical waveguide assemblies 410 are disposed in a loose spiral manner around the structural core 210 as illustrated in Figure 6a so that the one or more optical fibre waveguide assemblies 410 are not longitudinally stretched as the cladding 200 is flexed and the structural core 210 suffers strain in operation. In view of the cladding 200 being subject to high external pressure in operation, for example, to pressures approaching 1000 Bar, the void 460 is beneficially filled with a highly-flexible substantially-uncompressible viscous liquid and/or gel; optionally, the liquid and/or gel is operable to enable the one or more optical waveguide assemblies 410 to move relative to the structural core 210 and the cladding 200 to avoid stressing the one or more assemblies 410. Moreover, the liquid and/or gel is beneficially non-flammable, capable of tolerating temperatures approaching at least +200 ⁰C, and an electrical insulator. Beneficially, the liquid and/or gel is based, at least in part, on silicone material.

The cladding 200 beneficially has a wall thickness in a range of 2 mm to 5 mm, more optionally in a range of 2.5 mm to 3 mm. Moreover, the structural core 210 when optionally included has a diameter in a range of 1 mm to 3 mm. Furthermore, the void 460 has a lateral width in a range of 1 mm to 5 mm, more preferably in a range of 1.5 mm to 3 mm.

When manufacturing the communication link 120, the cladding 200 is beneficially fabricated as a molded continuous flexible tube. Thereafter, the structural core 210 together the one or more twisted pairs of wires 462 and the one or more optical waveguide guide assemblies 410 are then drawn along the cladding 200. Next, the void 460 thereby provided between the structural core 210 and the cladding 200 is filled with the aforesaid liquid and/or gel. Optionally, the gel is introduced into the void 460 as a liquid which is then allowed when in the void 460 to set to form the aforesaid flexible gel, for example cured by application of heat or after a period of time after being introduced into the void 460. Yet more optionally, the void 460 is filled along its length with alternating regions of gel and liquid to help support the one or more optical waveguide assemblies 410 incorporated therein, and to prevent the one or more waveguide assemblies 410 from slumping down to a bottom portion of the void 460 when the communication link 120 is in a vertical orientation in use whilst providing for flexibility of movement of the communication link 120 and adequate stress relief for the one or more waveguide assemblies 410. Yet more optionally, the one or more optical waveguide assemblies 410 are spatially periodically attached, for example at two-metre intervals along the communication link 120, to the one or more twisted wire pairs 462 so as the prevent the one or more waveguide assemblies 410 slumping to the bottom portion of the void 460 when the communication link 120 is in a vertical orientation in use in a borehole 10.

In operation, the communication link 120 is subjected to high pressures approaching 1000 Bar. Such high pressures are susceptible to resulting in gas penetrating into the cladding 200 and subsequently into the liquid and/o gel in the void 460. Subsequent sudden depressurization of the communication link 120 potentially results in gas pockets developing temporarily within the cladding 200 and the void 460; the gel and/or fluid within the void 460 is susceptible to flow along the communication link 120 to accommodate any stresses generated by occurrence of such gas pockets. Eventually any such gas pockets are susceptible to diffusing out through the cladding 200. The reinforcements 205 integrally present in the cladding 200 beneficially prevent the cladding 200 from expanding like a balloon in response to the temporary formation of gas pockets within the fluid- and/or gel- filled void 460 after sudden depressurization of the communication link 120.

Optionally, the structural core 210 is omitted and structural strength to the communication link 120 provided by the cladding 200. In such a situation, the optical fibre waveguide assembly 410 is beneficially pre-treated so that it preferentially assumes a helical spiral form within the void 460, for example by differentially treating the plastics material of the mechanical sleeve 420. Moreover, for situations when the structural core 210 is included or not, the void 460 includes features to prevent the optical waveguide assembly 410 from slumping down inside the void 460 as a result of the action of gravity.

The structural core 210 included substantially centrally within the cladding 200 is beneficially provided with spacer elements 464 therealong. The spacer elements 464 include a first portion to grip onto the structural core 210 and one or more lobes extending from the first portion, each lobe being provided with smooth rounded exterior surfaces so as not to abrade the one or more optical waveguides 410 in use. The one or more lobes have distal ends relative to the first portion, the distal ends being operable to abut onto an inside surface of the cladding 200. Optionally, the spacer elements 464 are fabricated from a molded plastics material, from rubber, from a ceramic material, or from a metal or metal alloy. The spacer elements 464 are optionally molded to the structural core 210 or bonded or otherwise firmly attached thereto. Spaces between the one or more lobes of the spacers 464 are operable to provide a region for loosely accommodating the one or more waveguides 410 in a helical or equivalent manner as elucidated in the foregoing. Examples of the spacer 464 are illustrated in Figure 6a as denoted by 464a, 464b, 464c corresponding to one, two and three lobes respectively. An alternative, or additional, feature to prevent the optical waveguide assembly 410 in helical form from slumping to a bottom of the void 460, for example when the communication link 120 is in a vertical orientation in use in a borehole 10, is to bind the fibre waveguide assembly 410 at periodical intervals to the twisted-wire pair 462 by way of fasteners, tie- wraps, clips, adhesive or similar as denoted by 468; such an implementation is illustrated in Figure 6b. The twisted-wire pair 462 is only susceptible to stretching to a limited extent in use, thereby defining an extent to which the optical waveguide assembly 410 in helical form is susceptible to being stretched out in a manner of a helical spring. Yet alternatively, or additionally, both the optical fibre waveguide assembly 410 and the twisted-wire pair 462 can be mechanically bound to the structure core 210 at spatially periodic intervals as illustrated in Figure 6c, thereby preventing the waveguide assembly 410 from slumping down in use within the void 460 whilst also allowing for movement in response to applied stress.

Referring back to Figure 4, the data processing arrangement 110 is implemented as a configuration of proprietary components and is susceptible to being installed on-land, on a sea-going vessel, in a submarine, and/or on an oil exploration platform, or on an air-borne vehicle via an additional wireless link, for example using a satellite wireless link. The data processor 330 and the display 130 are beneficially implemented using proprietary computing hardware; the data processor 330 beneficially has a data entry device, for example a keyboard and a computer tracker-ball mouse, for enabling one or more users 465 to control operation of the system 300. The data processor 330 is coupled in communication with the data memory 140 which is conveniently implemented by using at least one of: semiconductor memory, optical data memory, magnetic data memory.

Operation of the system 300 including the data communication link 120 will now be described in greater detail.

During exploratory drilling activities for gas and/or oil, expensive and complex equipment is used under the supervision of experienced technical staff. In consequence, drilling and lining the borehole 10 with the liner tubes 30 is an extremely expensive activity, for example often costing in a region of a million United States dollars per day. When such high costs are encountered, problems occurring within and around the borehole 10 need to be identified quickly and resolved promptly. Even an operation of removing a drill bit and its associated string from the borehole 10 is a major undertaking, in some cases corresponding to several days of expensive work. When applied to monitor the borehole 10, for example after removal of a drill bit and associated drive string therefrom, the system 300 needs to be highly reliable, susceptible to being rapidly deployed into the borehole 10, and to provide flexibility in use by way of real-time monitoring to avoid a need to repeatedly reinsert the probe assembly 100 into the borehole 10 when performing metrology and monitoring thereon.

Referring to Figure 7, the transducer array 320 comprises an array of one or more piezoelectric transducer elements 475 operable to at least receive ultrasonic radiation denoted by the radiation 350 from the borehole 10; there are n transducer elements in the transducer array 320. As elucidated in the foregoing, the radiation 350 is generated by one or more processes occurring in the borehole 10 when the system 300 is operating in the first passive mode, and is generated by reflection of the radiation 400 when the system 300 is operating in the aforesaid second active mode. As described earlier, the transducer elements 475 optionally ultrasonically communicate via an interfacing member 470 which transmits ultrasonic radiation therethrough as well as protects the transducer elements 475 from a harsh environment within the borehole 10.

The one or more transducer elements 475 in the transducer array 320 are operable to generate signals S,- e"⁸' wherein / is in a range of 1 to n; the signals S,- correspond to the electrical signals 360 described earlier. The digital signal processor 310 is operable to condition one or more of the signals S,- in a manner of a phased array algorithm to steer a direction of greatest sensitivity of the transducer array 320. Such steering is achieved by performing two principal steps in the digital signal processor 310.

The first step of beam forming involves selectively phase shifting and scaling the signals S,- under control of various control parameters. Moreover, the first step is performed in computing hardware of the digital signal processor 310 operable to execute a software product stored on a data carrier, for example the data carrier being a non-volatile semiconductor data memory associated with the digital signal processor 310, or the data carrier being semiconductor random access memory (RAM) into which software is downloaded via the communication link 120 when the system 300 is deployed in operation and/or prior thereto. In the first step, the signals S,- are subject to scaling and phase shifting operations as defined by Equation 1 (Eq. 1) to generate corresponding intermediate processed signals Hf.

H₁ = A₁S₁J" e™*¹*¹™"¹ Eq. 1

wherein j = square route of -1 ; ω = angular frequency of signal component of interest; t = time; θj = phase shift applied for beam forming purposes; Aj = scaling coefficient for beam forming purposes.

The second step of beam forming involves selectively summing one or more of the intermediate processed signals H,- as defined by Equation 2 (Eq. 2) to generate corresponding signals B_a__β representative of a component of radiation received at the transducer array 320 from a specific direction as follows:

ι=r wherein a, β = angles define the specific direction relative to an orientation of the transducer array 320 in which the transducer array 320 is preferentially sensitive for generating the signal B_{at β}\ and r, s = index values defining which intermediate signals Hj to be selectively summed to generate the signal B_{a: β}.

Optionally, the signals H_/ to be summed do not necessarily need to lie consecutively in series of index value i; for example appropriate scaled and phase-shifted signals S, for / = 1 , 10, 12, 15 can be selectively combined to generate the signal B_{aι β}. The angles a and β are susceptible to being defined, for example, as illustrated in Figure 8. A mathematic mapping relates the angles a, β to corresponding phase shift θ, and scaling coefficient A₁ are denoted by function G in Equation 3 (Eq. 3):

φ,A) = G(a,β) Eq. 3

wherein the function G is determined by a geometry and configuration of the transducer array 320. The function G is optionally pre-computed and stored as a mapping in data memory, for example in a form of a look-up table; the look-up table is beneficially stored irf at least one of the data processing arrangement 110 and the digital signal processor 310. Alternatively, the function G can be computed in real-time from parameters by way of a simulation in at least one of the data processing arrangement 110 and the digital signal processor 310. The signals B_{Oι β} are computed using at least Equations 1 and 2 (Eq. 1 and 2) in real-time and then communicated from the digital signal processor 310 via the communication link 120 to the data processor arrangement 110 for further processing there. Optionally, for example under control from the data processing arrangement 110 communicated via the communication link 120 to the probe assembly 100, the signals S,- are communicated directly in real-time, namely directly streamed, in a substantially unprocessed state via the communication link 120 to the data processing arrangement 110 and a majority of data processing then performed in the data processing arrangement 110.

As elucidated in the foregoing, the system 300 is optionally designed to economize on a way in which an available bandwidth of the communication link 120 is utilized in operation. Data flow reduction is susceptible to being achieved by one or more of following approaches:

(a) by dynamically instructing the probe assembly 100 only to send the signals S,- or the signals B_{Oβ β} corresponding to radially directions defined by B_{aι β} of special interest, thereby avoiding to process and send data for directions which are not of interest;

(b) by dynamically instructing the digital signal processor 310 only to process signals from a subset of the transducers 475, corresponding to a reduction in angular and spatial resolution, for example by dynamically adjusting values for limit indexes r, s; this saves computing effort and power dissipation within the probe assembly 100; (c) by dynamically instructing the digital signal processor 310 to send the signals corresponding to B_{aι β} or S,- at a reduced resolution, for example by only sending more significant bits of data bytes whilst maintaining computational accuracy within the digital signal processor 310; and

(d) by performing a fast Fourier transform at the digital signal processor 310 of the signal B_{aι β} to generate corresponding Fourier spectral coefficients F_a,_β and then by communicating the spectral coefficients F_{Oι β} via the communication link 120 to the data processing arrangement 110, namely by adopting a parameterized data compression process.

Optionally, in approach (d), the digital signal processor 310 is operable to compare, for example by a correlation-type technique or using a neural network approach, the Fourier spectral coefficients F_{aι β} with templates of frequency spectra of specific types of known defects occurring within boreholes, for example leakage holes, obstructions, cracks and so forth. In an event of the computed frequency spectral coefficients F_{Ot β} being sufficiently similar, within a threshold limit, to one or more of the frequency spectra of the one or more templates, a defect in the borehole 10 is deemed to have been found; in such case of finding a defect for the angles a, β, the digital signal processor 310 is operable to simply send an identification that one or more defects have been detected and a nature of the one or more defects. Such an extension of the approach (d) represents considerable data processing in the probe assembly 100 but also provides for a very high degree of data compression which potentially enables, for a given bandwidth available in the communication link 120, the probe assembly 100 to be advanced at a greater longitudinal velocity along the borehole 10 whilst simultaneously providing real-time monitoring. In an event that the borehole 10 is mostly free of defects along its length, such an approach as in (d) results in a relatively smaller amount of data exchange along the communication link 120 until a defect is found; in such an event that a defect if found, the system 300 is, for example, capable of dynamically switching from the approach as in (d) to comprehensive sampling of the signal β_{αj /?} when the probe assembly 100 is in close proximity to the detected defect and whilst the probe assembly 100 is manoeuvred more slowly relative to the detected defected.

When the system 300 is operated in the first passive mode, a signal B_{a, p} as illustrated in Figure 9a is often obtained. In Figure 9a, there is an absence of any drive signal Sd 390 applied to the transducer array 320; such absence is denoted by a horizontal line in Figure 9a. Noise generated within the borehole 10 is received at the transducer array 320 and gives rise to a resolved noise-like chaotic signal as illustrated in Figure 9a.

Conversely, when the system 300 is operated in the second active mode, the transducer array 320 is driven with the drive signals S_d 390 which are optionally phase shifted and amplitude adjusted so that the transducer array 320 emits a beam of ultrasonic radiation, namely the aforesaid radiation 400, in a preferred direction. Alternatively, the transducer array 320 is driven with the one or more signals S 390 to emit ultrasonic radiation, namely the aforesaid radiation 400, more omni-directionally. The one or more drive signals S_d 390 optionally include a temporal sequence of single excitation pulses mutually separated by a time duration Δt; such excitation single pulses approximate to pseudo-Dirac pulses and are capable of exciting a natural mode of resonance of the transducer array 320 such that the radiation 400 is emitted at a frequency of this natural mode of resonance. Conversely, when the drive signal S^ 390 is a periodically repeated sequence of a burst of pulses 600 as illustrated in Figure 9b, the frequency of the radiation 400 is susceptible to being at least partially defined by a pulse repetition frequency within the burst of pulses 600.

When operating in the second active mode, the burst of pulses 600 results in instantaneous direct signal breakthrough coupling, for example by way of direct electrostatic and/or electromagnetic coupling, giving rise to an initial detected pulse 610 which, optionally, can be gated out. A pulse wavefront in the radiation 400 propagates from the transducer array 320 to an inside facing surface of the liner tube 30a wherefrom a portion of the radiation 400 is reflected and propagates as a component of the radiation 350 back to the transducer array 320 to give rise to a reflected pulse 620 as shown in Figure 9b in the resolved signal B_a<p. A proportion of the radiation 400 is further coupled into the liner tube 30a and is reflected from an exterior facing surface of the liner tube 30a back through the liner tube 30a and further as another component of the radiation 350 back to the transducer array 320 to give rise after resolving to a weaker pulse 630 as shown in Figure 9b in the resolved signal B_{a> β}. In an event that an obstruction is present on an inside surface of the liner tube 30a, a pulse corresponding to the obstruction will be observed before the pulse 620. Moreover, in an event that the liner tube 30a is cracked or fractured, reflections forming the pulses 620, 630 will be confused, namely a convoluted and attenuated mixture of signal components.

In the first passive mode of operation of the system 300, spectral analysis, for example executed using a form of fast Fourier transform, of acoustic radiation generated by fluid flow through leakage holes and around an exterior of the liner tube 30a enables certain categories of defects to be detected. Conversely, when fluid flow is not occurring within the borehole 10, the second active mode of operation enables other types of defects to be identified. As elucidated in the foregoing, the system 300 is capable of being optimized for operating solely in either the first passive mode or solely in the second active mode. Alternatively, the system 300 is capable of being implemented to be able to function in both the first passive mode and the second active mode; for example, the system 300 is capable of being implemented to dynamically switch between the first and second modes in real-time when making measurements within the borehole 10.

Optionally, in order to reduce a quantity of data to be communicated via the communication link 120 when the system 300 is operating in the second active mode, the digital signal processor 310 is optionally configurable from the data processing arrangement 110 to analyze the signal B_{aι β} to identify times t_p when reflection pulses, for example the pulse 620, 630, occur after their corresponding excitation burst of pulses 600 or single excitation pulse, and to determine their corresponding amplitudes U, and then communicate time of reflected pulse information t_n and corresponding amplitude U as descriptive parameters via the communication link 120 to the data processing arrangement 110, thereby achieving potentially considerable data compression in comparison to communicating the signals B_{Oi β} directly to the data processing arrangement 110; a rate at which the probe assembly 100 is capable of being advanced along the borehole 10 whilst providing continuous monitoring of the borehole 10 is thereby potentially considerably enhanced in real-time.

Operation of the data processing arrangement 110 will now be further elucidated. When data is communicated from the probe assembly 100 via the communication link 120 to the data processing arrangement 110, the processing arrangement 110 is optionally operable to record the received data from the probe assembly 100 as a data log in the data memory 140. Such a record enables, for example, subsequent analysis to be performed after the probe assembly 100 has been extracted from the borehole 10, for example to perform noise reduction operations for increasing a certainty of detection of various types of defects in the borehole 10. The data processor 330 is operable to execute one or more software products which apply further analysis and condition of data received via the communication link 120 from the probe assembly 100.

In real-time, when the system 300 is functioning in the second mode of operation, the data processor 330 presents on the display 130 a local 3-dimensional view of an interior of the borehole 10 substantially at a depth z at which the probe assembly 100 is positioned within the borehole 10, for example refer to Figures 2, 3 and 5 for a definition of the depth z; in Figure 8, increasing depth z is in an upward direction in the drawing. Such representation on the display 130 in the second active mode of operation enables the one or more users 465 to visually spatially inspect the inside surface of the liner tube 30a in real-time. Time instances of receipt, for example, of the reflected pulses 620, 630 at the transducer array 320 provides an indication of the spatial location of the inside and outside surfaces of the liner tube 30a and also potentially an ultrasonic radiation view of material surrounding an exterior of the liner tube 30a.

Alternatively, in the first passive mode of operation of the system 300, there is provided an indication of potential defect or ultrasonic noise source as a function of the depth z and the angles a, β, see Figure 8. When the communication link 120 is implemented to provide sufficient communication bandwidth, for example by including one or more optical waveguide assemblies 430 in the communication link 120 to convey data, the sensor signals 360 generated by the transducer array 320 are communicated substantially unprocessed directly to the data processing arrangement 110 whereat considerable processing capacity can be easily provided remote from the borehole 10; comprehensive real-time processing for presentation simultaneously with data logging in the data memory 140 is thereby achievable. Alternatively, when the communication link 120 provides only very restricted communication bandwidth, for example via one or more electrical twisted pairs of electrical wires, different types of presentation are then optionally provided on the display 130 illustrating defect and/or noise type as a function of radial position as defined by the angles a, β, and the depth z.

When the system 300 is configured to function in the second active mode, the data processor 330 employs one or more software products which operate to map the signal B_{ai P} by a mapping function M to a Cartesian or a polar coordinate data array, namely w (x, y, z) or w (α, β, z), as denoted as a mapping step 700 in Figure 10 and described by Equation 4 (Eq. 4):

w (x, y, z) = M (B_{a, β} z) w (a, β, z) = M (B_a>β, z) Eq. 4

Values stored in elements w of the data array correspond to strength of reflected ultrasonic radiation, namely the aforesaid radiation 350, as determined from reflection pulse peak amplitude in the signal B_a,_β.

The signal B_{tti P}, for example as illustrated in Figure 9b, is optionally communicated to the data processing arrangement 110 in a data-compressed parameterized form as elucidated earlier. By action of the mapping function M, the data array w thereby has stored therein a spatial 3-dimensional image of an inside ultrasonic view of the borehole 10 wherein an array element w position is equivalent to a corresponding spatial position within the borehole 10.

Thereafter, in a gradient computation step 710, the data processor 330 is operable to apply a gradient-determining function to determine 3-dimensional gradients in element w signal amplitude values stored in the data array w (x, y, z) or w ( a, β, z), namely to determine whereat spatial boundaries between features are present in the ultrasonic image of the borehole 10 recorded in the data array w. Identification of spatial boundaries is also known as "iso-surface extraction" in the technical art of image processing and involves computation of partial differentials of the array elements w as provided in Equation 5 (Eq. 5):

dw dw dw dw dw dw

— , — , — or — , — , — Eq.5 dx dy dz da dβ dz

depending upon whether Cartesian or polar coordinate systems are employed. In a step 720, the one or more software products are then operable to enhance values in the data array w, for example by curve fitting techniques, to show more clearly whereat continuous boundaries occur in the elements w ( x, y, z) or w ( a, β, z) corresponding to stored image data stored in the data memory of the data processor 330. Such curve fitting operations offer a smoothing function so that images presented on the display 130 are not cluttered with irrelevant surface texture details, but nevertheless show relevant features regarding integrity and operation of the borehole 10. Optionally, a step of smoothing is alternatively performed before a step of extracting iso-surfaces is performed.

Thereafter, in a step 730, the data processor 330 is operable to read data from the element w of the data array and then write corresponding presentation values, after geometrical transformation when necessary, into a memory buffer serving the display 130.

Optionally, in an event that the one or more software products executing on the data processor 330 identify when extrapolating one or more boundaries in the image stored in the elements w of the data memory to be unclear, the data processor 330 is then operable in real-time to instruct, as denoted by 740, the digital signal processor 310 for specific values of the angles a, β io repeat measurements within the borehole 10 for resolving such lack of clarity in the image stored at the data processor 330. Such instruction to the digital signal processor 310 optionally includes one or more of:

(a) causing the probe assembly 100 to employ its digital signal processor 310 to appropriately phase shift and scale pursuant to Equations 1 and 2 (Eqs. 1 and 2) more of its electrical signals S,- to generate corresponding values of the signal B_a,_β thereby having greater directional definition and resolution, the signals B_a,_β being subsequently communicated to the data processing arrangement 110 for further data processing and subsequent presentation on the display 130;

(b) averaging, namely filtering, over numerous samples of the signal S,- to reduce noise for a limited range of specified angular sensing directions defined by the angles a, β, and then computing corresponding signals B_a,_β for communicating via the communication link 120 to the data processing arrangement 110 for subsequent further data processing thereat and thereafter presentation on the display 130;

(c) driving the transducer array 320 in the manner of a phased array so that more of its ultrasonic radiation 400 is delivered into a particular direction in which metrology and monitoring were previously unclear, acquiring further vales of the signal S,- and subsequently computing corresponding signals B_{a, β} for communication to the data processing arrangement 110 for further data processing at the data processing arrangement 110 and thereafter presentation on the display 130; and (d) acquiring a larger set of measurements over a given defined limited range of angles a, βso as to map out finer details of a feature present in the borehole 10, processing corresponding acquired signals S,- to generate corresponding signals B_a,_β, communicating the signals S^ via the communication link 120 to the data processing arrangement 110 for further data processing and eventual presentation on the display 130.

Beneficially, one or more of the users 465 as well as the data processing steps as illustrated in Figure 10 are able to invoke a reconfiguring of the probe assembly 100 to acquire enhanced information from one or more regions of the borehole 10. After the enhanced information is acquired b the system 300, the system 300 is beneficially operable to revert back to its previous configuration state to continue monitoring the borehole 10. Thus, during monitoring operations involving manoeuvring the probe assembly 100 of the system 300 along the borehole 10, the system 300 is optionally set to perform a method comprising steps of:

(a) performing a series of spatially coarse measurements along the borehole 10 whilst monitoring in real-time for any trace of one or more defects or other unusual features; (b) detecting one or more potential defects or other unusual features at a location along the borehole 10 in real-time;

(c) reconfiguring the probe assembly 100 to perform a selective more detailed series of measurements of the one or more defects or other unusual features; and

(d) after executing the more detailed series of measurements in step (c ), resuming the series of spatially coarse measurements along the borehole 10 as in step (a).

This method is capable of being employed when the system 300 is operating in its first passive mode or in its second active mode. Optionally, the system 300 is beneficially operable to dynamically switch in real-time between the first and second modes when performing the series of spatially coarse measurements along the borehole 10.

It will be appreciated that embodiments of the invention as described in the foregoing are susceptible to being modified without departing from the scope of the invention as defined by the appended claims.

Beneficially, the probe assembly 100 is furnished with one or more pressure sensors for measuring a pressure P present within the borehole 10 as the probe assembly 100 is manoeuvred in operation along the borehole 10. In an event that the probe assembly 100 detects that the pressure P in the borehole 10 becoming excessive, for example in excess of 500 Bar, the probe assembly 100 is operable to transmit a warning message to the one or more users 465.

Beneficially, the probe assembly 100 is furnished with a temperature sensor for measuring an operating temperature T within the probe assembly 100. In an event that the operating temperature T exceeds a predefined threshold temperature Th, the probe assembly 100 is operable to send a request to the data processing arrangement 110 to enable the probe assembly 100 to assume intermittent operation, wherein the digital signal processor 310 is permitted intermittently to enter a hibernating low-power state in order to provide the digital signal processor 310 with an opportunity to cool slightly by reducing electrical power dissipation therein. When in the hibernating state, advance of the probe assembly 100 along the borehole 10 is optionally temporarily halted.

The transducer array 320 is described briefly in the foregoing. The array 320 is susceptible to being implemented in various configurations, for example at least one of:

(a) a rectangular matrix of mutually perpendicular rows and columns of individual transducer elements, for example cut from a single slab of polarized piezo-electric material, for example by using a fine diamond saw; peripheral edges of the matrix are optionally straight or curved; the rectangular matrix is beneficially mounted at a bottom surface of the probe assembly 100 facing down the borehole 10 when the probe assembly 100 is in operation;

(b) a series of individual transducer elements arranged in one or more ring formations; the one or more ring formations are beneficially mounted at one or more ends of the probe assembly 100, or radially around an radial side wall of the probe assembly 100;

(c) in one or more rows or a spiral formation around a peripheral surface of the probe assembly 100 in a substantially longitudinal direction along the probe assembly 100.

Optionally, the probe assembly 100 further includes an electronic compass for measuring a direction of the Earth's north and south magnetic poles at the probe assembly 100 in order to provide a corresponding orientation signal for communicating via the communication link 120 to the data processing arrangement 110; receipt of such an orientation signal enables the data processor 330 to correct for the angle β as shown in Figure 6 when the probe assembly 100 is lowered into the borehole 10 and revolves during its descent into or during subsequent extraction from the borehole 10. Alternatively, or additionally, to employing a compass to determine an orientation of the probe assembly 100, a gyroscopic sensor is employed to provide an angular reference.

The probe assembly 100 beneficially has an exterior diameter "d" in a range of 100 mm to 180 mm, more beneficially a diameter in a range of 120 mm to 160 mm, and most beneficially substantially a diameter of substantially 150 mm. Moreover, the probe assembly 100 beneficially has a longitudinal length "L", disregarding attachment of the cladding 200 and its associated communication link 120, in a range of 0.5 metres to 5 metres, more beneficially in a range of 1 metre to 3 metres and beneficially substantially 1.5 metres.

The system 300 is capable of being adapted to perform one or more of the following functions:

(a) Well leak detection, wherein the system 300 is operable to function as a Well Leak

Detector (WLD); (b) Well sand detection, wherein the system 300 is operable to function as a Well Sand Detector (WSD);

(c) Well flow detection, wherein the system 300 is operable to function as a Well Flow Detector (WFD); and

(d) Well annular flow detection, wherein the system 300 is operable to function as a Well Annular Flow monitor (WAF).

The system 300 is optionally optimized to perform one of functions (a) to (d). Alternatively, the system 300 can be optimally designed to perform several of these functions and to dynamically switch between such functions when in use. Certain of the functions (a) to (d) are serviced in the aforementioned first passive mode, whereas other of the functions (a) to (d) are addressed by the system 300 operating in its second active mode. In general, a cost and complexity of the system 300 increases as it is required to be more versatile in performing diverse functions.

Although use of the communication link 120 in conjunction with the probe assembly 100 and the data processing arrangement 110 is described in the foregoing, the communication link 120 is susceptible to being used in other types of systems which are susceptible to experiencing hostile environments, for example: (a) submerged undersea telecommunication links subject to considerable flexure in use, for example as aquatic vessels change their spatial position relative to an oil exploration and/or production platform; (b) submerged electrical power cables to submarine equipment and sea-bed mounted equipment, for example linking a surface aquatic vessel to a submarine in off-shore petrochemicals facilities; and

(c) in underground mining equipment when flooding or submerged operation is required.

Expressions such as "including", "comprising", "incorporating", "consisting of, "have", "is" used to describe and claim the present invention are intended to be construed in a nonexclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

Claims

1. A data communication link (120) for coupling a first apparatus (100) in data communication with a second apparatus (110) wherein said first apparatus (110) and said communication link (120) are spatially moved in operation relative to said second apparatus (110), said communication link (120) being operable to provide mechanical support for said first apparatus (100),

characterized in that

said communication link (120) includes one or more optical fibre waveguides (430) for coupling said first apparatus (100) in data communication with said second apparatus (110), and said one or more optical fibre waveguides (430) are disposed in a spatial formation in relation to said communication link (120) which at least partially isolates said one or more optical fibre waveguides (430) from mechanical stresses when said first apparatus (100) is moved in operation relative to said second apparatus (110).

2. A data communication link (120) as claimed in claim 1 , wherein said communication link (120) has an uninterrupted length in a range of 1 km to 10 km.

3. A data communication link (120) as claimed in claim 1 or claim 2, wherein said communication link (120) is adapted to support said first apparatus suspended on said communication link (120) substantially vertically therefrom.

4. A data communication link (120) as claimed in any one of the preceding claims, wherein said formation of said one or more optical fibre waveguides (430) includes at least one helical formation which is flexible in its longitudinal and lateral directions without substantially axially straining said one or more optical fibre waveguides (430).

5. A data communication link (120) as claimed in any one of claims 1 to 4, wherein said data communication link (120) includes an exterior cladding (200) for defining at least one void (460) within said exterior cladding (200), said at least one void (460) being operable to accommodate said one or more optical fibre waveguides (430), and said at least one void (460) being filled with a liquid and/or gel for mechanical supporting said one or more optical fibre waveguides (430) in a stress-isolated manner.

6. A data communication link (120) as claimed in claim 5, wherein said data communication link (120) includes at least one structural core (210) within said at least one void (460) for providing said data communication link (120) with axial rigidity for bearing a weight of said first apparatus (100) in operation.

7. A data communication link (120) as claimed in claim 6, wherein said one or more optical waveguides (430) are disposed in a helical manner around said at least one structural core (210).

8. A data communication link (120) as claimed in claim 6 or 7, wherein said one or more optical fibre waveguides (430) are attached at spatially periodic intervals along said communication link for preventing said one or more optical fibre waveguides slumping within said at least one void (460) when in operation.

9. A data communication link (120) as claimed in any one of the preceding claims, wherein said data communication link (120) in combination with said first and second apparatus (100, 110) constitute a monitoring system (300) for monitoring within a borehole (10), said first apparatus (100) being operable to function as a probe assembly (100) operable to be moved within said borehole (10) for sensing one or more physical parameters therein, said second apparatus (110) being operable to function as a data processing arrangement (110) located outside the borehole (10), and said data communication link (120) being operable to convey sensor data indicative of said one or more physical parameters from the probe assembly (100) to the data processing arrangement (110) for subsequent processing and display and/or recording in data memory (140),

wherein

(a) said probe assembly (100) includes one or more sensors (320) for spatially monitoring within the borehole (10) and generating corresponding sensor signals (360);

(b) said probe assembly (100) includes a digital signal processor (310) for executing preliminary processing of the sensor signals (360) to generate corresponding intermediately processed signals (370) for communication via said data communication link (120) to the data processing arrangement (110); (c) said data processing arrangement (110) is operable to receive said intermediately processed signals (370) and to perform further processing on said intermediately processed signals (370) to generate output data for presentation (130) and/or for recording in a data memory arrangement (140).

10. A data communication link (120) as claimed in claim 9, wherein said system (300) is operable to generate said output data for presentation (130) in real-time when said probe assembly (100) is moved within the borehole (10).

11. A data communication link (120) as claimed in claim 9 or 10, wherein said system (300) is operable in at least one of first and second modes, wherein:

(a) said first mode results in said system (300) passively sensing noise sources present in the borehole (30) generating radiation (350) for sensing at the one or more sensors (320); and (b) said second mode results in said system (300) actively emitting radiation into the borehole (10) and receiving at said one or more sensors (320) corresponding reflected radiation from a region in and/or around the borehole (10) for generating said sensor signals (360).

12. A data communication link (120) as claimed in claim 11 , wherein said system (300) is operable to be dynamically reconfigurable between said first and second modes when said probe assembly (100) is being moved in operation within said borehole (10).

13. A data communication link (120) as claimed in any one of claims 9 to 12, wherein said system (300) is operable to communicate data bi-directionally between said data processing arrangement (110) and said probe assembly (100), wherein said digital signal processor (310) of said probe assembly (100) is operable to being reconfigured between a first function of general sensing around in a region of the borehole (10) in a vicinity of the probe assembly (100), and a second function of specific sensing in a sub-region of said region of the borehole (10) in a vicinity of the probe assembly (100).

14. A data communication link (120) as claimed in any one of claims 9 to 13, wherein said data communication link (120) includes one or more twisted-wire pairs including plastics material insulation and copper electric conductors embedded within said plastics material.

15. A data communication link (120) as claimed in any one of claims 9 to 14, wherein said data processing arrangement (110) is located in operation remotely from the probe assembly (100), said data processing arrangement (110) providing an interface for one or more users (465) to control in real-time operation of the probe assembly (100), and for generating graphical images for presentation on one or more displays (130) to the one or more users (465), said graphical images being representative of spatial features present within and/or around said borehole (10) in a vicinity of said probe assembly (100).