GB2494170A

GB2494170A - Acoustic pipeline inspection

Info

Publication number: GB2494170A
Application number: GB201115110A
Authority: GB
Inventors: Robert Wilkinson; Geoffrey Harris George Bush
Original assignee: SONAR PIPELINE INSPECTION SYSTEMS Ltd
Current assignee: SONAR PIPELINE INSPECTION SYSTEMS Ltd
Priority date: 2011-09-01
Filing date: 2011-09-01
Publication date: 2013-03-06
Also published as: GB201115110D0

Abstract

A method for use in inspecting a pipeline 14 comprises inserting a pipeline inspection apparatus 10 comprising a transducer array 32 into the pipeline and transmitting an acoustic signal 44 from transducers 34 towards an internal wall surface 22 of the pipeline at an angle of incidence obliquely aligned relative to said internal wall surface. A signal 48 reflected from the internal surface is received by the transducer arrangement and used to determine or estimate a condition of the wall. A further acoustic transducer array 36 may be included and reflected signals combined with the obliquely reflected signals. Properties such as wall thickness, roughness, corrosion, defects, cracks, deposition of hydrates and surface hardness may be determined. The apparatus is typically mounted on a pipeline pig.

Description

I

PPELINE INSPECTION METHOD AND APPARATUS

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for infine inspection of a pip&ne using acoustic signals.

BACKGROUND TO THE INVENTION

Many industries utflise pipenes for the transportation of fluids, ncluthng iqLüds and gases, and even saNds, such as powders, fine artEculates, slurries, aggregates and the like. ft is desftable to be able to determine the condlUons of a pipeline during its service Nfc to identify compromised sections and permit appropriate maintenance and repair to be undertaken. Such inspections are critical in many industries, such as the o and gas industry, to minimise the frequency of faures within the pipeline, such as ass of structural integrity which may result in leakage of contaminant material into the environment, exposure of personnel to injury or the like.

Many pipehne inspection processes involve deploying an inspection apparatus through a pipehne mounted on a Pigging apparatus, or Pig, which is typicaHy driven by the fluid being communicated through the pipefine, for example by use of fins or annular blades. This permfts inspection to be achieved whe the pipeDne is operationaL Ultrasonic pipeNne inspection devices are known in the art, such as is disclosed in ER 0 684 446, in which ultrasonic signals are targeted at the inner surface of the pipeline from arrays of transducers mounted on the device. However, many known inspection devices are concerned only with the wall thickness of the pipeline, and seek to detect variations in the wall thickness, particularly reductions in wall thickness, along the length of the pipeline.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provide.d a method $0 for use in inspecting a pipeline, comprising: inserting a pipeline inspection apparatus comprising a transducer arrangement into a pipeNne; tranamifting an acoustic signal from the transducer arrangement towards an internS waN surface of the pipeline at an angle of incidence which is obliquely aligned relative to said internal wall surface: receiving a signal reflected from the internal wall surface of the pipeline and determining or estimating a condition of the wafi of the pipeline using the reflected signal.

The method may comprise transmitting at east a component of an acoustic signal from the transducer arrangement at an angle of incidence which is obkquely agned relative to said internal wall surface.

The determination or estimaUon of a condition of the waU of the pip&ine by use of the obque signal may be based on a direct measured property or parameter of the associated reflected signalS The determination or estimation of a condition of the wall of the pipeline may be based on calibration data for different sample conditions, heuristic or experiential analysis or the like.

The method may comprise determining an internal surface condition of the wall of the pipeline using the reflected signal associated with the transmitted oblique signaL The method may comprise determining an internal surface roughness condition of the wall of the pipeline using the reflected signal associated with the transmitted obque signaL A rneasur of the surface roughness may be used to determine or estimate other conditions of the wafl of the pipeline. For example, a measure of the surface roughness may permit a corrosion or erosion condition of the pipeline to be determined or estimated. Determining a surface roughness condition may permit a material deposition condition on the internal waH surface of the pipeline to be determined or estimated. For example, a surface roughness condition may be used to determine or estimate a material type which is deposited on an internal surface of the pipeline. Such a determination or estimation of features of the pipeline based on a surface roughness condition may be based on calibration data for different sample conditions, heuristic or experiential analysis or the lika A wall condition, such as a surface condition of the pipeline may he determined or estimated based on one or more parameters of the reflected signal associated with the transmitted oblique signal. A frequency parameter of the reflected signal may be used to deternne a condition ci the wafl of the pipeline. A wavelength parameter of the reflected signal may he used to determine a condition of the wall of the pipeline.

An amplitude parameter of the reflected signal may be used to determine a condition of the wall of the pipeline. A reflectivity parameter of the reflected signal may be indicative of a condition of the pipeline wall. For example, a ratio of the amplitudes of the transmitted and reflected signals may he indicative of a condition of the pipeline wall.

The method may comprise receiving a reflected signal whkTh is reflected from the internal wa surface of the pipeUne at a specular angle of reflection. It shothd be understood that the specular angle of reflection is equal to the angie of incidence, In this embodiment the method may comprise determining a condition of the wafl of the pipeflne using an ampUtude value or parameter of a specular reflected signal. For example, a surface roughness condiflon of an internal waD surface may be determined using an ampUtude value or parameter of a specular reflected signaL In this arrangement a specular reflected sign having a greater ampUtude may he indicative of a smoother surface condilion than a specular reflected signal having a smaller amplitude.

The method may comprise receiving a reflected signal which is reflected from the internal wail surface of the pipeline at a diffuse angle of reflection. It should be understood that the diffuse angle of reflection excludes the specular angle of reflection.

In this embodiment the reflected signal may be correlated with a degree of scattering of the transmitted acoustic signal upon reflection from the internal wall surface. wherein the degree of scattering may be associated with a surface condition of the pipeDne, parficularly, but not exclusively, a surface roughness condition. The method may comprise determining a condition of the wall of the pipeline using an amplitude value or parameter of a diffuse reflected signal. For example, a surface roughness condition of an internal wall surface may be determined or estimated using an amptude value or parameter of a diffuse reflected signal. In this arrangement a diffuse reflected signal having a greater amplitude may be indicative of a rougher surface condition than a diffuse reflected signal having a smaDer amplitude.

The method may comprise: transmitting an acoustic signal from the transducer arrangement towards an internal surface ci the pipeline along a transmission path with an angle of incidence which is obliquely aligned relative to said internal surface; receiving a signal reflected from the internal surface of the pipeiine which travels along a reflection path which substantially coincides with the transmission path; and determining or estimating a condition of the wall of the pipeline using the reflected signal.

The method may comprise transmitting and receiving an associated reflected signal by a common transducer of the transducer arrangement. The method may comprise transmitting a signal from a first transducer of the transducer arrangement and receiving an associated reflected signal at a second, different transducer of the transducer arrangement.

The transducer arrangement may comprise one or more transducers. At least one transducer may be configured for transmitting an acoustic signal At least one transducer may be configured for receiving an acoustic signal At least one transducer may be configured for transmitting and receMng an acoustic signal At east one transducer may be configured [or transmitting an acoustic signal and receiving a reflection of the same acoustic signal A mounhng orientation of one or more transducers of the transducer arrangement may be adjustable. This may permit a transmission direction of an acoustic signal to be adjusted.

The transducer arrangement may comprise at east one transducer which defines a coupng surface ohquely agned relative to the internal waH surface of the pipeline, wherein the coupling surface is configured for transmitting an acoustic signa therefrom. in this arrangement the direction of the transmitted signal may be a function of the orientation of the coupng surface of the transducer. The coupng surface may be configured for transmitting an acoustic signal therefrom having a component which is normal to said coupling surface. The coupling surface may So be configured for receiving an acoustic signaL The pipene inspection apparatus may define a central axis which is aUgned substantiay parallel with the internal wall surface of the pipeline when located therein.

The transducer arrangement may comprise at least one transducer which is obliquely mounted on the pipehne inspection apparatus relative to the central axis thereof. The transducer arrangement may comprise at least one transducer which is mounted on a tapered surface of the pipeline inspection apparatus, such as a conical surface.

The method may comprise obliquely aligning a coupling surface of th.e transducer arrangement relative to the internal wall surface of the pipeline, and transmitting a signal from the coupling surface to define an oblique signal angle of incidence relative to said internal wa surface. The method may comprise transmitting a signal from the coupUng surface which has a component aligned normal thereto to define an obflque signal angle of incidence relative to the internal wall surface of the pipeline.

The method may comprise transmitting a signal from a coupling surface of the transducer arrangemen.t which has a component aligned normal thereto, wherein the coupling surface is obiiquely aligned relaflve to the internS surface to permit the normal component of the transmitted signal to define an obllque angle of incidence relative to the internal wall surface of the pipefine.

The method may comprise transmitting a signal from a coupling surface of the transducer arrangement which has a component ahgned obllquely thereto to define an obllque angle of incidence relative to the internal wall surface of the pipene. In this arrangement the coupllng surface may be allgned obllquely or parallel to the internal wall surface of the pipene. In some embodiments the coupllng surface may be allgned substantially parallel with the internal wall surfaceS wher&n a gnal is transmitted from a coupllng surface of the transducer which has a component which is obliquely allgned relafive to said coupling surface so as to define an oblique angle of incidence relative to the internal wall surface of the pipeline.

The method may comprise: transmitting an acoustic signal from the transducer affangement towards an internal wall surface of the pipeline at an angle of incidence which is normal relative to said internal wall surface; receiving a signal reflected tmm the internal wall surface of the pipeline; and determining or estimating a condiUon of the wall of the pipeline using the reflected signaL The method may comprise transmitting at east a component of an acoustic signal from the transducer arrangement at an angle of incidence which is normal relative to said internal wall surface, The determination or esfimation of a condition of the wall of the pipeline by use of the normal signai may be based on a direct measured property or parameter of the associated reflected signaL The determination or estimation of a condition of the wall of the pipeline may be based on calibration data for different sample conditions, heuristic or experiential analysis or the like.

The method may comprise determining a hardness condition of the wall of the pipeline using the reflected signal associated with the transmitted normal signaL A measure of the wall hardness may be used to determine or estimate other conditions of the wall of the pipeline. For example, a measure of wall hardness may permit a corrosion or erosion condition of the pipeline to be determined or estimated, Determining a hardness condition may permit a material deposition condition on the internal wall surface of the pipeline to be determined or estimated. For example, a hardness condition may be used to determine or estimate a material type which is deposited on an internal surface of the pipeline. Such a determination or estimation of e features of the pipeline based on a hardness condition may be based on calibration data for different sample conditions, heuhetic or experiential analysis or the ke.

A waH condition, such as a hardness condition of the pipeline may be determined or estimated based on one or more parameters of the reflected signal associated with the transmitted normal signaL A frequency parameter of the reflected signal may be used to determine a condition of the wali of the pipeline. A wavelength parameter of the reflected signal may be used to determine a condition of the wali ci the pipeline. An amplitude parameter of the reflected &gnal may be used to determine a condition of the wafl of the pipeline. A reflectivity parameter of the reflected signal may be indicative of a condition of the pipeline walL For example. a ratio of the amplitudes of the transmitted and reflected signS may be indicative of a condition of the pipeline wall In some embodiments a parameter, such as an amplitude parameter of a reflected signal associated with the transmitted normal signal may permit knowledge of an acoustic impedance of the wall of the pipeline to be obtained, wherein said acoustic impedance permits a determination or estimation of material hardness to be made, For example, in some embodiments a larger amplitude of a reflected signal may be associated with a harder material than a lower amplitude of the reflected signal.

The method may comprise determining or estimating a condition of the wall of the pipeline using the reflected signal which has reflected at least twice from the internal wall surface of the pipeline. This arrangement may permit diverging or deviated components of the transmitted normal signal to be eliminated, thus improving accuracy.

The method may comprise determining a condition of the wall of the pipeline based on the reflected signals associated with both the transmitted oblique signa and the transmitted normal signal. In such an arrangement the location ci reflection on the pipe wall of the transmitted signals may be a common location, or alternatively may be different but adjacent regions. The location of reflection may comprise adjacent regions in close proximity to each other. In some embodiments the reflected signal associated with the transmitted oblique signal may permit a surface roughness condition to be determined or estimated, and the reflected signal associated with the transmitted normal signal may permit a material hardness condition of the wall of the pipeline to be determined or estimated, Knowledge of both the surface roughness and material hardness at a common location within the pipeline may permit improved knowledge of the pipeline condition to be determined or estimated. For example, a combined surface roughness measurement and material hardness measurement may he unique to a particular condition, such as a particular material, state of corrosion or erosion or the like. The method may comprise determining or estimating a condition of the pipeline using knowledge of surface roughness and hardness, obtained from reflections ci transmitted obque and normal signals. In one embodiment the method may comprise providing a graphical plot of surface roughness and material hardness, wherein a particular pipeline condition may be determined based on said graphical p'ot.

This determination may be based on calibration data for different sample conditions, heuristic or experiential analysis or the like.

The method may comprise transmitting oblique and normal acoustic signals, relahve to the internal wal! surface of the pipeline, from different transducers of the transducer arrangement. The method may comprise transmittir.g oblique and normal acoustic signals, r&ative to the internal wall surface of the pipeline, from a common transducer.

A wa thickness condition of the pipeline wall may be determined from a reflected acoustic signal, and more particularly from a reflected acoustic signal associated with a transmitted normal signal. A wa thickness condition may be determined by use of signais reflected from internal and external walls of the pipeline, along with knowledge of lime of flight. A wall thickness condition may be determined by use of multiple echoes of signals reflected from internal and external waUs of the pipeline. Such use of multiple echoes may permit improved accuracy of a wall thickness condition to be determined.

A pipeline width, diameter or other internal dimension condition may be determined &orii a reflected acoustic signal, and more particularly from a reflected acoustic signal associated with a transmitted normal signaL A pipeline width, diameter or other internal dimension may be determined by use of signals reflected from an intema! wall surface of the pipeline., along with knowledge of time of flight.

The transducer arrangement may comprise a plurality of transducers. The transducers may be circumferentially arranged on the inspection apparatus. The transducer arrangement may comprise a first array of transducers configured to transmit one or more oblique signals. The transducer arrangement may comprise a second array of transducers configured to transmit one or more normal signals.

The transducer arrangement may be configured to transmit acoustic signals through a material contained within the pipeline. For example, the pipeline may contain a liquid, such as oil, a gas, such as hydrocarbon gas, or the like. The transducer arrangement may be configured to transmit acousUc. signals at frequencies in a range of, for example, 20kHz to 100MHz, For example, for transmission through a liquid medium the transducer arrangement may he configured to transmit acoustic signals at frequencies in a range ci, for example. 2MHz to 20MHz. For transmission through a gaseous medium the transducer arrangement may be configured to transmit acoustic signals at frequencies in the range of, for example, 100kHz to 500kHz, The method may comprise translating or moving the inspection apparatus through the pipefine and determining or estimating a condition of the pipeline at muftiple locations along the length oF the pipene. The inspection apparatus may he pumped through the pipeline, for example mounted on or as part of a Pig apparatus.

The method may comprise storing data associated with the reflected signal or signals within memory. In this arrangement said data may be uploaded and anaiysed, for example after the inspection apparatus has been retrieved from the pipeline. The data may be stored in a raw format. The data may be stored in a processed format, In such an arrangement the method may comprise processing data and then storing such processed data. Th arrangement may permit the required storage capacity to be reduced (or allow greater data set size) and permit a reduction of download and post processing time.

The method may comprise transmitting data associated with the reflected signal or signals to a remote location from the inspection apparatus. Said data may be transmitted wirelessly.

The method may comprise determining a position of the pipeline inspection apparatus within the pipeline. The method may comprise identifyng repeating features of a pipeline, such as joint regions including welded joint regions to determine a position of the pipeline inspection apparatus within the pipeHne.

The method may be configured for use with any pipeline or pipeline structure.

For example, the pipehne may comprise a surface pipeline, subsea pipeline, subterranean pipeline or the hke. The pipeline may be associated with or form part of a subterranean wellbore, such as a welibore for use in the exploration and production of resources from subterranean reservoirs, such as water, hydrocarbons or the like. The pipeline may be defined by a tubing string, such as a casing or liner string, which extends into a drilled bore, According to a second aspect of the present invention there is provided a pipeline inspection apparatus configured for use in the method according to the first aspect.

it should be noted that features associated with the pipeiRie apparatus defined in ration to the first aspect may be appflcable to this second aspect.

According to a third aspect of the present invention there is provided a pipeline inspection apparatus configured to be located within a pipeline, comprising: a body; a transducer arrangement mounted on the body and configured to transmit an acoustic signal towards an internal wafi surface of the pipene at an angle of incidence which is obUquy agned relative to said internal waU surface, and to rec&ve a signal reflected from the internal wafi surface of the pipene to permit a condition of the wa of the pipeUne to be determkned or estimated, It should be noted that features associated with the piperie apparatus defined in relafion to the first aspect may be appUcable to this third aspect.

The refRacted signal associated with the transmitted obHque signal may be for use in determining or estimating a surface roughness condition of the pipeline.

The body may define a central axis.

The transducer arrangement may comprise at east one transducer which is obUquely aligned relative to the central axis of the body. Such an oblique transducer aUgnment may permit a &gnai to be transmRted which is obliquely aUgned relative to the internal wall surface of a pipeline.

The transducer arrangement may be configured to transmit an acoustic signal towards an internal wall surface of the pipeline at an angle of incidence which is normal relative to said internal wail surface, and then receive a reflection of said normal signal.

The reflected signal associated with the transmitted normal signal may be for use in determining or estimating a hardness condition of the pipeline.

The transducer arrangement may comprise at least one transducer which is &igned parallel to a central axis of the body.

The apoaratus may be configured to be mounted on a device for deployment through a pipeline. The apparatus may be configured to be mounted on a Pig device.

The apparatus may form part of or define a Pig device.

The apparatus may comprise memory configured to store data associated with one or more reflected signals.

The apparatus may comprise one or more pressure sensors configured to measure a pressure withEn a pipeline, The apparatus may comprise a differential pressure sensor. Such a differential pressure sensor may be adapted to determine a differential pressure used to drive the apparatus through a pipeline, for exampe via a Pig device.

The apparatus may comprise a noise andlor vthration sensor. This may permit the noise generated by the apparatus when in operation wfthin a pipehne to be determined.

The apparatus may comprise one or more orientation sensors configured for use in determining an orientation of the apparatus. For example, the apparatus may comprise one or more gyroscopic devices. The apparatus may comprise one or more accelerometers.

The apparatus may ccm.phse one or more temperature sensors. At east one temperature sensor may be configured to determine a temperature of a mated& contained within the pipeline. Knowledge of such a materiS temperature may permit compensation or cabraUon of the transducer arrangement to be achieved, for example in accordance with changes in the speed of sound in the material according to changes hi temperature.

The apparatus may comprise an on-board power supply, such as a battery, [or example a compact battery arrangement. Such a battery arrangement may comprise a lithium-Ion battery Nickel Metal Hydride battery, alkaline battery or the like.

The apparatus may be configured to be activated when deployed within a pipehne. This may permit the apparatus to be deactivated until located within a pipeline. This may assist in permitting the apparatus to meet regulatory requirements, such as AlEX requirements. In one embodiment the apparatus may comprise a pressure operated switch. This may permit activation of the apparatus when exposed to pipeline pressure conditions, The apparatus may comprise a pressure reUef arrangement. This may permit the apparatus to be relieved of any internal pressure upon retrieval from the pipeline.

According to a fourth aspect of the present invention there is pro'ded a method for use in inspecting a pipeline, comprising: inserting a pipehne inspection apparatus comprising a transducer arrangement into a pipeline; transmitting an acoustic signal from the transducer arrangement towards an internal wall surface of the pipeline at an angle of incidence which is obliquely aligned relative to said internal wa surface; receiving a signal reflected from the internal wall surface of the pipeline associated with the transmitted obque signal; transmitting an acoustic signal from the transducer arrangement towards an internal waH surface of the pipene at an angle of incidence which, is normal relative to said internal wall surface; receiving a signal reflected from the internal waU surface of the pipene associated with the transmitted normal signal; and determining or estimating a condition of the wa of the pipeline using the reflected signals.

BRIEF DESCRIPI1ON OF THE DRAWINGS IC These and other aspects of the present invention wl now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic iUu&raticn of a pipeline inspection apparatus in accordance with an embodiment of the present invention, wherein the apparatus is shown mounted within a Pig device and being translated through a pipene; Figure 2 is an enlarged parhal crosssectional view of the apparatus of Figure 1; Figure 3 is an enlarged view of a portion of the apparatus of Figure 1, illustrating transmison and reception of acoustic signals; Figures 4A and 43 provide diagrammatic iflustrahons of reflections of an obliquely transmitted acoustic signal from pipe wafl surfaces with different surface roughness; Figures 5A and 53 provide diagrammatic iUustrations of reflections of a transmitted normal acoustic signal from pipe wa surfaces with different hardness; Figure $ provides a diagrammatic illustration of a plot of roughness and hardness values used to provide a determination of a pipe wall condition; Figure 7 is a diagrammatic illustration of a portion of a pipeline inspection apparatus in accordance with an alternative embodiment of the present invention; and Figure 8 provides a diagrammatic illustration of signals reflected from an internal surface of a pipeline after transmission from the apparatus in Figure 7.

DETAILED DESCRIPTION OF THE DRAWINGS

A pipeline inspection apparatus, generally identfied by reference numeral 10, in accordance with an embodiment of the present invention is shown in Figure 1. The apparatus 10 is mounted within a Pig device 12 which is deployed through a pipeline 14 in the direction of arrow 16 by a fluid 18 which is communicated through the pipeline 14 in this respect the Pig device 12 comprises a plurality of annular fins 20 which extend radiaHy towards the inner wali surface 22 of the pipeline 14 to present a large area to the moving fluid 18. The fluid 18 may be a liquid or gas, such as oH, water, hydrocarbon gas or the ke. The pipeline 14 may be a surface pipene, subsea pipeUne or a subterranean pipene. As wili be thscussed in further detaH below, the inspection apparatus 10 is configured to transmit acoustic signals from a transducer arrangement 21 and receive reflected signals from the inner wail surface 22 of the pipeline 14. Such reflected signals are then used to determine or estimate a condition of the w&l of the pipeline 14.

An enlarged and partial crosssectional view of the inspection apparatus 10, removed from the Pig device 12 and pipeline 14, is shown in Figure 2, reference to which is now made. The apparatus 10 includes a housing 24 which defines a central lonaitudinai axis 26 which is intended to be aligned parallel with the pipeline 14. The housing encloses various electronic components, such as a battery pack 28 and a CPU and memory component 30. Mhough not shown, the apparatus 10 may includes various features to support appropriate safety measures, such as ATEX compliance.

For example, the apparatus 10 may include a pressure operated switch which permits the internal electronics and other associated equipment to be isolated and deactiv'ated until the apparatus 10 is located within a pressurised pipeline. Further, the apparatus may include a pressure rehef valve which assists to prevent explosion of the housing 24 if t has leaked and reached pipeline pressure during operaUon followed by return to atmospheric pressure when retrieved from the pipeline. Also, the housing 24 may be formed with pressure retaining functionality to prevent any internal explosion rupturing the housing 24 and potentially igniting surrounding explo&ve substances.

The transducer arrangement 21 is mounted on a leading end region of the apparatus 10 and comprises a first transducer array 32 composed of a single circumferential row of acoustic transducers 34 and a second transducer array 36 composed of two circumferential rows of acoustic transducers 38. In the embodiment shown the transducers 34, 38 are of the same type and are configured for both transmission and reception of acoustic signals. The first transducer array 32 is located on a conical or tapered portion 40 of the apparatus 10, such that each transducer 34 within the array 32 is obliquely aligned relative to the central axis 26, and thus the interna wall surface 22 of the pipeline 14 when located therein. The second transducer array 36 is located on a cylindrical portion 42 of the apparatus 10 such that each transducer 38 within the array 36 is aligned parallel to the central axis 26, and thus the internal wall surface 22 of the pipeline 14 when located therein, An enlarged diagrammatic view of the apparatus 10 within a pipellne 14 showing a single transducer 34, 38 of each array 32. 36 is shown in Figure 3 reference to which is now made, wherein operation of each transducer array 32, 36 in terms of transmission and reception of acoustic signals is illustrated, As will be discussed in detaiL the first transducer array 32 is configured to provide for a determination or esfimation of the roughness of the wall surface to be made. Also, the second transducer array 36 is configured to provide for a determination or estimation of the hardness of the pipellne wall to be made, and also to determine or estimate the wall thickness, Furthermore, the second transducer array 3$ is configured to provide for a determinaUon of internal pipe diameter and/or shape, such as ovallty, deformation or the lika Further conditions of the pipene may also be determined or esfimated based on a combinatbn of the data obtained from both the first and second arrays 32, 36, such as material identification or classifiesUon, Each transducer 34 of the first array 32 defines a coupllng or transmission/reception surface 34a which is configured to transmit a signal 44 into the pipellne medium 18 towards the inner pipeline surface 22 at an oMque angle of incidence. For clarity of the present descripfion signal 44 will be defined as a transmitted oblique signal. The frequency of the transmitted signS may be s&ected in accordance with a number of variables, such as the type of medium 18 present within the pipellne. In some embodiments a frequency of, for example, 2 MHz to 20MHz may be used where the medium 18 comprises a fluid, such as oll, Where the medium comprises a gas, such as hydrocarbon gas, a frequency of, ror example, 100kHz to 500kHz may be used.

The angle of incidence of the transmitted oblique signal 44 in the present embodiment is determined by the mounting orientation of each transducer 34 on the conical portion 40 of the apparatus 10. In some embodiments the mounting orientation of one or more of the transducers 34 within the first array 32 may be adjustable.

The transmitted oblique signal 44 will be reflected from the inner pipeline wall surface 22 in a number of directions in accordance with the conditions of the surface 22. In this respect a specular reflected signal 46 may result, which will propagate from the surface 22 at a specular angle ci reflection, that is an angle which equals the angle of incidence of the transmitted oblique signal 44. Furthermore, a diffuse reflected signal 48 may result. ln the present embodiment each transducer 34 is configured to receive a diffuse reflected signal 48 which pmpagates along a path which substantially coincides with the transmission path of the transmitted obllque signal 44. In this respect utihsing a transmitted ohqtie signs 44 permits the reflected diffuse signal 48 to be isolated from other reflected components, such as the reflected specthar component 46, thus improving accuracy while reducing the necessary signal analysis, data storage requirements and the Uke.

As will be discussed in further deta below, the diffuse reflected gnal 48 is correlated with a degree of scattering of the transmitted acoustic signal upon reflection from the internal wa surface 22, wherein the degree of scattering is assodated with a roughness condition of the pipeline wa surface 22. In this way the diffuse reflected signal 48 may provide information relating to the roughness of pipeline surface 22, which may be used to determine or estimate other conditions, such as corrosion, material deposition or the ke.

A correlation between surface roughness and the reflected diffuse signal 48 is illustrated in Figures 4A and 4B which show plots of a received reflected signal parameter (Rs) with respect to time U). In the present embodiment the received signal parameter of interest is signal energy, such as may be obtained based on an integration of reflected signal amplitude. In alternative embodiments a reflected signal amplitude parameter may be used. Figure 4A represents an output based on a pipeline waU surface having a lower roughness than that associated with Figure 48.

That is, a lower surface roughness wiU result in a lower proportion of the transmitted oblique signal 44 being scattered or diffused upon reflection such that the energy of the diffuse reflected signal 48 will be lower than compared with a rougher surface condition.

A roughness indication using the first transducer array 34, such as illustrated in Figures 4A and 48 may be used to determine or estimate an actual surface roughness value. Such a determination or estimation may be based on calibration data for different sample conditions, heuristic or experiential analysis or the like.

Alternatively, or additionally, the output roughness indicators illustrated in Figures 4A and 48 may be used to determine or identify changes along the length of a pipeline. In this case actual roughness values may not be required.

Referring once again to Figure 3 operation of a transducer 38 forming part of the second transducer array 36 will now be described. Each transducer 38 defines a coupling or transmission/reception surface 38a which is configured to transmit a signal into the pipeline medium 18 towards the inner pipeline surface 22. In the embodiment shown as mentioned above, each transducer 38 is mounted on a cylindrical portion 42 of the apparatus and as such the coupling surface 38a is, in use.

aligned substantially parallel wth the pipeline inner surface 22. Accorthngly, the signal is transmitted normal to the inner surface 22. For clarity of the present description signal 50 will be defined as a transmitted normS signal.

A portion of the transmilled normal signal 50 is reflected from the inner surface, returning to the transducer 38 as a first reflected &gnal 52. This first reflected signal 52 will be received by the transducer 38, but will also be reflected from the apparatus 10 back towards the inner surface 22 of the pipeline 14, resulting in a second reflected signal 58 being received by the transducer 38. Also, a poton of the transmitted signS is transmitted into the wail of the pipeline 14 and reflected from the outer pipeline IC) surface 54, returning to the transducer 38 as a third reflected signal 56.

A graphics illustration of the reflected signals 52, 56, 68 with respect to time is shown in Figure 5A. Similar to Figures 4A and 43, the illustration in Figure 5A utHises a reflected signal parameter (Re) which in the present embodiment is signal energy.

As shown, the first reflected signal 52 is received at time ti, and the third reflected signal 56 is received at time t2. Knowledge of ti and t2, and of the speed of sound in the medium 18 and the pipe wall will permit a wall thickness to be obtained.

Furthemiore, knowledge of ti and the speed of sound in the medium 18 will permit a pipe inner dimension, such as diameter to be obtained. Such a pipe inner dimension may be obtained by use of results or data acquired from pairs, or all transducers in the array 36. Such measurement of pipe inner dimension may permit knowledge of the diameter, shape. such as ovality, deformation and the like in the pipeline to he obtained.

The energy or amplitude of one or both of the first reflected signal 52 and the second reflected signal 58 (i.e., those signals reflected from the inner wail surface 22), may be used to determine or estimate a hardness condition of the pipeline wall In this respect the energy or amplitude of the first and second reflected signals 52, 58 may be correlated with the acoustic impedance of the pipeline wall, wherein said acoustic impedance is associated with material hardness. Specifically, a reflected signal with a greater energy or amplitude may provide an indication that reflection has been achieved from a pipeline wall material having a higher acoustic impedance (or more accurately a higher acoustic impedance differential between the medium 18 and the pipeline wall), which in turn may provide an indication of an increased material hardness. This is illustrated with additionai reference to Figure 58, which represents the energy parameters of reflected signas 52a, 56a, 58a which have been reflected from a harder surface than those reflected signals 52, 56, 58 illustrated in Figure 5k in this reaped, the reflected signals in Figure SB have larger energy signatures than those hi Figure 5k The signal parameter values (Rs) in Figures 5A and SB may be used to determine or estimate an actual materia! hardness value, Such a determination or estimation may be based on cabration data for different sample conditions, heuristic or expehenti analysis or the like. Alternetiv&y, or addftionally, the output hardness indicators Uustrated En Figures 5A and SB may be used to determine or identj changes in hardness along the length of a pipeline. In this case actual hardness values may not be required.

As noted above, one or both of the first and second reflected signifis 52, 58 may be used for determining or estimating a material hardness condition. In some embodiments the second reflected signal 58 may be preferred as this may have lower contamination from any diverging effects of the transmitted normal signal 50. Further, the second reflected signal 58 may permit more sensitive equipment and signal analysis techniques to be used.

As discussed above, the reflected signals associated with the first and second transducer arrays 32, 36 may independently provide information for determining or estimating conditions of the pipeline 14. However, in some embodiments the infonnatian from both transducer arrays 32, 36 may be combined to permit further or more accurate condition determination to be achieved. For example, as iflustrated in Figure 6, values of the roughness and hardness obtained by the transducer arrays 32, 36 at common locations along the length of the pipeline may be plotted against each other. In Figure 6 point A represents the values obtained from Figures 4A and 5A (Is., smoother and softer), and point B represents the values obtained from Figures 48 and 58 (Lw, rougher and harder). Each point may be indicative of a particular condition, such as material type, corrosion level or the like. For example, the particular combination of hardness and roughness values at point A may permit a determination to be made that at that point in the pipeline a wax hydrate deposit is present. Further, the particular combination of hardness and roughness values at point B may permit a determination to be made that at that point in the pipeline there are no or little material deposits, but that advanced corrosion is present. Such increased level of knowledge may permit appropriate remedial steps to be determined with no or minimal further investigations.

In some embodiments appropriate calibration data based on known samples may be obtained and made available during a pipeline inspection to permit comparisons with the inspection data to assist in determining or estimating the condition of the pipeUne.

In use, the apparatus 10 may be translated Song the required length of the pipene 14 with a sampflng rate selected according to the speed of the Pig apparatus to obtain data at appropriate interv&s. Data coected via the transducers in the embodiment shown is stored in the memory component 30 of the apparatus 10, preferably in raw format, with the data retrieved foowing removal of the apparatus tO from the pipehne 14. Appropriate analy&s of the data may then subsequently be performed. This arrangement permits the size and complexity of the apparatus 10 to be minimised, as the requirement for signal processors End the like is eliminated or substantiay reduced (although the apparatus 10 may be capable of perForming some processing of the data prior to storage).

A pordon of a pipeline inspection apparatus, generafly identified by reference numeral 60, in accordance with an alternative embodiment of the present invention is shown in Figure 7. The inspection apparatus 60 in Figure 7 is simar in many respects to the apparatus 10 first shown in Figure 1, and for brevity only the differences wiH be highlighted, with common features being deFined by common reference numerals. In the present described embodiment, the apparatus 60 includes a transducer array which includes at least one transducer 62 capable of transmitting both an obHque signal 44 and a normal signal 50 from a coupling surface 62a. In the iHustrated embodiment the coupling surface 62a is aUgned substantially parallel with the pipeline inner surface 22, and is capable of transmitting a highly diverging signal having a diverging component to define the transmitted obque signal 44, and a normal component to define the transmitted normal signal 50. The transmitted oblique signal will be reflected from the inner wall surface 22 to create a diffuse reflected signal 48 which is received by the transducer 62. Also, the transmitted normal signal will be reflected fmm the inner surface 22 and produce a first reflected signal 52 and a second reflected signal 58. In other embodiments further rebounded reflections between the apparatus 60 and pipeline wall 22 may be present, although for the present discussn only the first two are considered. Further, a reflection from the outer wall surface 54 will be present, although this has been omitted from Figure 7 for clarity.

Figure 8 illustrates the form of the reflected signals 48, 52, 58 with respect to time using the apparatus 60 of Agure 7. In the particular embodiment iUustrated reflected signal 48 from the transmitted oblique signal 48, and the first reflected signal 52 from the transmitted normal signai 50 temporally overlap. Appropriate signal analysis may be performed to iso'ate each component, pardcSrBy to isolate signal 48 which represents a backscatter component of the complete response. in this way reflected signal 48 may be used to provide a deten'nhiation or estimation of the roughness or the pipeline surface 22, simdar to thai described above.

Further, the second reflected signal based on the transmitted normal signal 50 may be used in the determinaUon or estimation of a pipeUne material hardness condftion in a simar manner to that defined above. In this respect by using the second reflected signal 58, as opposed to the first reflected signal 52, contamination from reflected signal 48 may be eminaIed or substantiay reduced, However, in other embodiments the second reflected signal may not be of interest, and appropriate values obtained via signals 48 and 52 only.

Afthough not iustrated in any deta above, the alternatve embodfrnents may include a number ci add[tional features. For example, a differential pressure sensor may be provided to determine a force required to propel the Pig device 12 through the pipeline 14. Also, an absolute pressure sensor may be provided to determine the pipeline operathig pressure. Further, a noiseMbration sensor may be provided to perm analysis of the noise generated by the Pig device 12 as it passes along the pipeline. Arrangernenf.s for position or orientation sensing may be provided. For example, accelerometers, gyroscopic devices and the Bike may be provided, Further, temperature sensors may be provided. Such temperature sensors may permit the temperature of the pipeline medium 18 to be determined to permit compensation of temperature dependencies in the transducers.

It should be understood that the embodiments described her&n are merely exemplary and that various modifications may be made thereto without departing from the scope of the present invention. For example, the apparatus may be deployed through a pipeline in any suitable way. For example, the apparatus may comprise an onboard propulsion arrangement, such as a track system. Also, any suitable number> arrangement and combination of transducers and/or transducer arrays may be used to provide the transmitted oblique and normal signals. Also, signals may be transmitted and received from different transducers.

Claims

<claim-text>CLAIMS: 1. A method for use in inspecting a pipene, compri&ng: inserting a pipeiine inspection apparatus comprising a transducer arrangement into a pipene; transmitting an acoustic signal from the transducer arrangement towards an internal waU surface of the pipeline at an angle of incidence which is obquely agned relative to said internS wall surface; receiving a signal reflected from the internal wall surface of the pipefine; and determining or estimating a condition of the wall of the pipeline using the reflected signal.</claim-text> <claim-text>2. The method of claim 1 comprising determining an internal surface cond Won of the wall of the pipeline using the reflected signal associated with the transmitted obUque signal.</claim-text> <claim-text>3. The method of claim I or 2, comprising determining an internal surface roughness condition of the waD of the pipeine using the reflected signal associated with the Iranamitted obDque signal.</claim-text> <claim-text>4, The method of claim 1, 2 or 3. wherein a wall condition, such as a surface condition of the pipeline is determined or estimated based on one or more parameters of the reflected signal associated with the transmitted oblique signal.</claim-text> <claim-text>5. The method of any preceding claim, wherein at least one of a frequency parameter, wavelength parameter, energy parameter, amplitude parameter and reflectivity parameter of the reflected signal is indicative of a condition of the pipeline waH.</claim-text> <claim-text>6. The method of any preceding caim, comprising receiving a reflected signal which is reflected from the internal wail surface of the pipeline at a specular angle of reflection.</claim-text> <claim-text>7, The method of any preceding claim, comprising receMn.g a reflected signal whch is reflected from the internal wa surface of the pipene at a diffuse angle of reflecUon.</claim-text> <claim-text>8. The method of claim 7, wherein the dtffuse reflected &gnal is correlated with a degree of scattering of the transmitted acoustic signal upon reflection from the internal waU surface, wherein the degree of scattering is associated with a surface condition of the pipene.</claim-text> <claim-text>9. The method of any oreceding claim, comprising: transmitting an acoustic signal from the transducer arrangement towards an internal surface of the pipeline aong a transmission path with an angle of incidence which is obliquely aUgned relative to said internal surface; receiving a signal reflected from the internal surface of the pipeline which travels along a reflection path which substantialiy coincides with the transmission path; and determining or estimating a condition of the wafi of the pipeline u&ng the reflected signaL 10. The method of any øreceding claim, comprising transmittLng and receiving an associated reflected signal by a common transducer of the transducer arrangement.11, The method of any preceding darn, comprising obliqueLy aligning a coupling surface of the transducer arrangement relafive to the internal wali surface of the pipene, and transmitting a signal from the coupling surface to define an oblique signal angle of incidence relative to said internal wali surface.12. The method according to any preceding claim, comprising transmitting a signal from a coupling surface of the transducer arrangement which has a component aligned norm& thereto, wherein the coupling surface is obliquely aligned relative to the internal surface to permit the normal component of the transmitted signal to define an oblique angle of incidence relative to the internal wall surface of the pipeline, 13. The method according to any preceding claim, cornprng: transmitting an acoustic signal from the transducer arrangement towards an hiternal wall surface of the pipellne at an angle of incidence which is normal relative to said internal wall surface; receMng a signal reflected from the internal wall surface of the pipehne; and S determining or estimating a conthtion of the wall of the pipeline ung the reflected signaL 14. The method according to claim 13, comprising determining a hardness condition of the wall of the pipellne using the reflected signal associated with the transmitted normal signal.is. The method according to claim 13 or 14, wherein a wall condition of the pipeline is determined or estimated based on one or more parameters of the reflected signal associated with the transmitted normal signal.16. The method according to claim 15, wherein the parameter of the reflected signal comprises at least one of a frequency parameter, a wavelength parameter, and energy parameter, an amptude parameter and a reflectivity parameter.17. The method according to any one of claims 13 to 16, comprising relating a parameter of a reflected signal associated with the transmitted normal signal with an acoustio impedance, wherein said acoustic impedance permits a determination or estimation of material hardness to be made.18. The method according to any preceding claim, comprising determining or estimating a condition of the wall of the pipeline using a reflected signal which has reflected at least twice from the internal wall surface of the pipeline.19: The method according to any one of claims 13 to 18, comprising determining a condition of the wall of the pipeline based on the reflected signals associated with both the transmitted oblique signal and the transmitted normal signal.20. The method according to c'aim 19, wherein the reflected signal associated with the transmitted oblique signal permits a surface roughness condition to be determined or estimated, and the reflected signal associated with the transmitted normal signal may permit a materia! hardness condition of the waD of the pipeDne to be determined or estimated.21. The method according to daim 20, wherein a combined surface roughness measurement and material hardness measurement is associated with a particuiar condition including at east one of a particular material and a state of corrosion.22. The method according to claim 20 or 21, comprising providing a graphical plot of surface roughness and material hardness, wherein a particular pipene condition is determined based on said graphical plot.23. The method according to any preceding claim., comprising transmitting oblique and normal acoustic signals, relative to [he internal wall surface of the pipeline, from different transducers of the transducer arrangement.24. The method according to any one of claims 13 to 23, comprising determining a waU thickness condition of the pip&ine from a reflected acoustic signal associated with a transmflied normal signaL 25. The method according to any one of clams 13 to 24, comprising determining a pipeHne inner thmension from a reflected acoustic signal associated with a transmitted normal signa.25. The method according to any preceding claim, wherein [he transducer arrangement comprises a plurality of transducers circumferentially arranged on the inspection apparatus.27. The method according to any preceding claim, comprising transmitting one or more oblique signals from a first array of transducers? and transmitting one or more normal signals from a second array of transducers.28. The method according to any preceding claim. comprising translating or moving the inspection apparatus through the pipelno and determining or estimating a condition of the pipehne at multiple locations along the length of the pipeline.29. The method according to claim 28, wherein the inspection apparatus is moved through the pipeline mounted on or as part of a Pig apparatus.30. A pipeline inspection apparatus configured to be located within a pipeline, comprising: a body; a transducer arrangement mounted on the body and configured to transmit an acoustic signal towards an internal wali surface of the iCilflC at an angle of incidence which is obliquely aligned relative to said internal wail surface, and to receive a signal reflected from the internS wali surface of the pipeline to permit a condition of the wali of the pipeline to be determined or estimated.31. The apparatus according to claim 30, wherein the body defines a central axis and the transducer arrangement comprises at least one transducer which is obliquely aligned relative to the central axis of the body to permit a signal to be transmitted which is obliquely aligned relative to the internal wall surface of a pipeline.32. The apparatus according to claim 30 or 31, wherein the transducer arrangement is configured to transmit an acoustic signal towards an internal wall surface of the pipeline at an angle of incidence which is normal relative to said internal wall surface, and then receive a reflection of said normal signal.33. A method for use in inspecting a pipeline, comprising: inserting a pipeline inspection apparatus comprising a transducer arrangement into a pipeline; transmitting an acoustic signal from the transducer arrangement towards an internal wall surface of the pipeline at an angle of incidence which is obliquely aligned relative to said internal wall surface; receiving a signal reflected from the internal wail surface of the pipeline associated with the transmitted oblique signal; transmitting an acoustic signal from the transducer arrangement towards an internal wall surface of the pipeline at an angle of incidence which is normal relative to said internal wall surface; receiving a signai reflected from the internal wall surface of the pipeline associated with the transmitted normal signal; and determining or esthuating a condition of the wall of the pipeline using the reflected signals.</claim-text>