UNDERWATER REMOTE INSPECTION APPARATUS AND METHOD

Technical field

The invention relates to the design of a remote in-situ underwater inspection apparatus and method for detecting leaks from underwater structures, risers and pipelines. More particularly, it relates to the detection of leaking fluids using fluorescence methods .

Background.

A significant proportion of the world's offshore structures are situated sub-sea or on the seabed. The size of these structures can range from small pipes to big production templates and pipelines that can be hundreds of kilometres long. These structures incorporate pipes, pipelines and risers.

The pipes are filled with a number of different fluids. These fluids can be hydrocarbons, injection water, hydraulic control fluids and a number of other fluids. The temperatures and pressures of these fluids can span over an extended range.

The loss of these fluids represents a financial loss and they can reduce the efficiency of the production. Additionally most of these fluids are harmful to the environment .

To ensure a clean and efficient production and transport of produced hydrocarbons the industry strives to detect and pinpoint leaks in their structures as soon as they occur. Additionally new and future regulations require the undertaking of regular surveys to detect leaks sub- sea.

Large leaks may be detected by monitoring the system internal operation parameters such as monitoring pressure drops in an enclosed system. Large pipelines can be internally checked using technology such as pig's searching for defects in the pipe.

Other methods used to detect these leaks are using external sensors, for example passive acoustic devices or fluorometers . These sensors can be mounted permanently on sub-sea structure or on underwater vehicles such as Remote Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) .

The passive acoustic devices detect and analyse the noise generated by fluids or gases when they leak from a pipe. The disadvantage of this method is that it is very difficult to pinpoint the exact location of the leak and that small leaks may not be detected at all.

The fluorescence systems rely on the fact that the leaking fluids fluoresce under certain excitation light. A disadvantage of this method is that the fluids must have a specific fluorescence spectrum that is different from the background fluorescence generated from other materials present in the vicinity such as organic material in the water. Another disadvantage with current systems is that they rely on single point detection methodology, which does not give a direct indication of the location of a leak within a wide field of view. These systems only give an average fluorescence reading in a given region but not visualising the leak. For example it is difficult to locate the exact point of leakage since in large sub-sea systems several pipes can be close together and the leaking fluid may have already diffused into a large volume of the water surrounding the leakage.

The main advantage of fluorescence sensors is its high sensitivity. Many fluorescent molecules produce very strong signals that can be easily picked up using a number of different sensors.

The problems of the exciting fluorescence based systems can be overcome by the present invention which discloses a novel method for locating the leaking location on the structure and provides a novel design of a fluorosensor apparatus which provide accurate location of the leaking fluids on subsea or underwater structures.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided apparatus for detecting leaks of fluorescing material from pipes or containers, the apparatus comprising an exciting means for effecting a fluorescence of the leaking fluid, a receiving means for receiving a picture of the induced fluorescence from the leaking fluid, a receiving means for receiving a picture of the observed scene, a processing means for processing and analysing the received fluorescence-picture and overlaying it to a live video of the scene determining the position and strength of the leak. This system makes it easier to locate fluorescence. The system can be used with an audible alarm. Using the real time video speed, the system can be used by an ROV pilot to directly navigate the ROV towards the leak.

The apparatus may comprise an exciter unit and a receiver unit mounted together.

The exciting means may comprise a light-source that projects a beam of light in the direction where the measurement is undertaken.

Preferably, the exciter unit comprises an array of high power light emitting diodes. Preferably, the exciter unit comprises an optical band pass filter to select the preferred excitation wavelength.

Preferably, the receiver unit comprises a high gain imaging camera, typically an intensified camera that is directed in the same direction as the exciter unit.

Preferably, the high intensified camera comprises a narrow optical band pass filter to select the preferred fluorescence wavelength which is different to the preferred excitation wavelength.

Preferably, the preferred fluorescence wavelength is out- with the band pass excitation wavelength and in most cases of longer wavelength.

Preferably, the receiver unit comprises a second camera that is directed in the same direction as the exciter unit, to provide an overlay picture of the structure under surveillance. Preferably, the second camera is mounted rigidly to the high intensifier camera.

Preferably, the apparatus comprises a first subsystem located beneath the surface of the water, and a second subsystem located at or above the surface of the water, the first and second subsystems being connected by a communication and power link.

Preferably, the first subsystem comprises an underwater receiving means for receiving a spectrally filtered fluorescence video signal, and a second receiving means for receiving a spectrally unfiltered video signal, and an underwater processing means for relaying the received video signals to the second subsystem.

Preferably, the second subsystem comprises a processing unit, a control unit, and a user interface.

According to a third aspect of the invention, there is provided a method of detecting leaks of fluorescent material, the method comprising the steps of: - Inducing a excitation light onto the structure to be surveyed; - Detecting a filtered intensified fluorescence video signal and relaying the signal to the second subsystem. - Detecting an unfiltered video signal and relaying the signal to the second subsystem; - Processing the video signals in a way that the filtered intensified fluorescent video is overlaid onto the unfiltered video and displayed on the user interface;

The method may comprise the additional steps of: - Multiplexing the two video signals in a way that only one video channel is being used to transmit the video signals to the second subsystem, using well known technologies.

The method may comprise the additional steps of: - Saving screenshots or video footages so they can be used for reference or further analysis at a later stage.

The method may comprise the step of transmitting a video signal to a subsystem located at or on the surface of the water.

The invention described is an apparatus and method for detecting leaks of fluorescing material from structures, pipes and containers. The apparatus is designed to be

deployed by any standard underwater means such as ROV, AUV, robot or diver and as a permanently fixed addition to underwater structures for constant monitoring.

The apparatus may include means for the induction and recording of fluorescence of leaking material, and the processing and display of the recorded fluorescence video signal. Video signal processing prepares the fluorescence signal in a way that will be displayed on the user interface and can be interpreted by an operator. The deployment of the apparatus and the detection of leakages are conducted underwater.

In the preferred embodiment, the apparatus is made up of two separate parts joined by a communication link. One part is deployed underwater, the other topside such as onboard a floating vessel, offshore platform or other surface facility. The topside part of the apparatus comprises a user interface, a control unit and a processing unit. The underwater part comprises a control unit, an exciting unit and receiving units.

An optional feature of the topside part is an interface allowing the operator to control and monitor the activity of the underwater unit.

Another optional feature of the topside part is a controlling unit that manages the data exchanged between the topside and underwater units.

Another optional feature of the topside part is a processing unit that prepares the data sent by the underwater unit.

An optional feature of the topside processing and control unit is a means to take a screenshot of the overlaid fluorescence video to be used for later references.

Another optional feature of the topside part is the ability to connect to a remote server in order to relay the video signal to a remote point.

An optional feature of the underwater part is that it is ruggedised to a standard adequate to prevent damage to any of its units during underwater deployment.

Another optional feature of the underwater part is that it can be fixed onto a rigid framework designed to bring the exciting unit and the receiving units in the correct position to excite fluorescence in the leaking material, and to receive the resulting video signals.

The framework must also be suitable for deployment by a platform such as an ROV or AUV so that exciting unit and receiving units are brought into correct proximity to the area under inspection.

Another optional feature of the underwater part is a means of conveying the video signal in real time to the topside part so that the leaks can be identified in real time during the course of the inspection.

Another optional feature of the exciting unit is it must be capable of operating underwater down to the operating depth of submersible vehicles.

An optional feature of the receiving units of the underwater part is a means to record a live fluorescence signal of the area under inspection such as an intensified camera with a sensitivity and wavelength range appropriate for detection of the fluorescence. Preferably, a narrow optical band-pass filter is used to select the preferred wavelength for the detection of the fluorescence.

An optional feature of the receiving units of the underwater part is a means to record a live video signal of the area under inspection such as a CCD or CMOS camera with or without intensification with a sensitivity and wavelength range appropriate for imaging of the surveyed area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the preferred embodiment of the present invention;

FIG. 2 is a perspective schematic of the preferred embodiment of the apparatus being deployed from an ROV;

FIG. 3 is a schematic of the excitation unit in the pressurised housing;

FIG. 4 is a schematic of the underwater receiver unit showing detail of the intensified camera with the band pass filter, the camera for the unfiltered image and the video relaying unit with the power supply.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the preferred embodiment of the present invention will be described based on the accompanying drawings .

Fig. 1 is a block diagram illustrating the preferred embodiment of the present invention.

In Fig. 1 a inspection apparatus according to the present invention includes an underwater exciting unit 1 for generating a light to be projected onto the area under investigation 2 to induce fluorescence from leaking material in the area under inspection. The fluorescence and light from the area under inspection 2 is detected by the underwater receiving units 3 where the two video signals are being captured and transferred to the underwater video processing unit 4.

The underwater video processing unit 4 relays the two video signals to the top side processing and control unit 5 using well-known techniques. The topside processing and control unit 5 processes and overlays the fluorescent video onto of the unfiltered video, using well-known techniques. The processing may include video noise filtering, particle size analysis, threshold analysis and pattern recognition. The overlaid information can be displayed using a colour coded format related to signal intensity or fluorescence pattern physical properties, such as size or shape.

The topside processing and control unit transfers the processed video signal to the topside user interface 6.

Fig. 2 is a view illustrating a schematic construction of a leak detection apparatus according to the preferred embodiment of the present invention.

The apparatus consists of a pressurised housing 7 which incorporates the underwater excitation unit 1 and a second pressurised housing 9 which incorporates the underwater receiving unit 3 and the underwater video processing unit 4. The underwater excitation unit 1 projects a beam of light 8 onto the area under inspection 2.

The pressurised housing 7 is fixed securely to the pressurised housing 9. Both housings point towards the area under inspection.

Fig. 3 is a view illustrating a schematic construction of the pressurised housing 7 incorporating the underwater excitation unit 1. The underwater excitation unit 1 consists of a power and control module 10 for the light emitting diode array 11. An optical band pass filter 12 filters the light so that only the preferred excitation light exits the unit.

FIG. 4 is a schematic of the pressurised housing 9 showing detail of underwater receiving unit 3 and the underwater video processing unit 4. The underwater receiving unit 3 consists of a narrow band pass optical filter 13 where the incoming light is filtered to select the preferred wavelength of the target material. The

light is then focused using an objective 14. The light is then amplified using an intensification module 15. The intensification module 15 is equipped with an auto gain amplifier so that it enables the system to cope with a wide range of light intensity. The video signal is then captured using a camera 16.

An unfiltered image is captured using a second camera 18 attached to a focusing objective 17.

The two video signals are then transmitted to the topside processing and control unit 5.

The topside processing and control unit 5 applies known video processing techniques to analyse and overlay the two video signals and display them in a way that can be easily interpreted. The process involves softwares that identify the different concentration present in the field of view of the system and displays it on the user interface unit. These video processing techniques are well known to those skilled in the art of video processing.

The status information can then be sent to server networks located anywhere in the world via standard telecommunication means such as radio, telephone and satellite links.

Various modifications may be made within the scope of the invention herein intended.

In one alternative embodiment the system can be used to detect different dyes, optical brighteners, oil and any other products that can fluoresce.

In another alternative embodiment the system can be used for the analysis of living organisms like algae's and corals. For example the system can be used for the analysis of the effectiveness of biocides on living cells and the change in fluorescence can be recorded.

In another alternative embodiment the system can be used for the detection of any fluorescent solids, fluids or gases.

In another alternative embodiment the system can be used for navigational help when finding the source of a leak.

In another alternative embodiment the system can be used for navigational help when under water structures are marked using fluorescent markers.

In another alternative embodiment the system can be used for navigational help when under water structures are marked using different fluorescent markers to allow an automated system to follow the markers and receive information from them.

In another alternative embodiment the system can be used either underwater, on the surface, airborne or in space.

In another alternative embodiment the system can be used with multiple excitation units to increase the range of the system.

In another alternative embodiment the system can be used with multiple excitation units with different wavelength so that different materials can be excited and various materials can be distinguished from one another.

In another alternative embodiment the system can be used with more than one intensified cameras set-up each with a different preferred band pass filter to detect different wavelengths to detect several materials at the same time and distinguish between them.

In another alternative embodiment the excitation unit can be used in a way that the exciting light is modulated. Using further processing of the received video signal it is possible to extract the background signal from the fluorescence signal.

In another alternative embodiment the excitation unit can be used in a way that the exiting light is modulated. Using gated detectors information about the distance to objects in the field of view and the fluorescence can be derived.

In another alternative embodiment the excitation unit can be used in a way that the exiting light is gated. Using gated detectors information about the concentration of the present fluorescing materials can be derived.

In another alternative embodiment the excitation unit can use flash-lamps, lasers, xenon arc lamps and other light sources.

In another alternative embodiment the underwater receiving unit can use cooled CCD cameras and other image producing optical sensors.

In another alternative embodiment in the underwater receiving unit the unfiltered camera can use an intensified camera to enable a better sight of the scene under low light conditions.

In another alternative embodiment in the underwater receiving unit the unfiltered camera can be fitted with an optical filter of preferred wavelength in order to filter unwanted light. This can be used to enhance vision for the operator.

In another alternative embodiment the two subsystems previously described as the complete system can be built as one unit deployed temporarily or permanently underwater. When a pre-specified fluorescence signal is detected the unit can then trigger a response such as activating a communication link or a secondary apparatus linked to it.

In another alternative embodiment the two subsystems previously described as the complete system can be built as one unit built into an apparatus that can be used by a diver. The information will be displayed directly to the diver using a standard incorporated display.

In another alternative embodiment the fluorescence information can be displayed to the end user using a head-mounted display.

Many of other alternative forms of the present invention will be apparent from the foregoing of methods and apparatus. Accordingly, the structures and techniques hereinabove depicted and described are only illustrative and not intended as limitations to the scope of the present invention.