WO2019046961A1

WO2019046961A1 - Hydrocarbon leak detection system and method for pipelines

Info

Publication number: WO2019046961A1
Application number: PCT/CA2018/051100
Authority: WO
Inventors: Dilip Tailor; Dennis Wong; Ronald J. Dunn; Nazanin KHALILI; Hani Naguib; Mark Phillip Brandon; Akshay SESHADRI; Haotian Shi; Miriam Rafaela BENINCA; Jeremy Joseph ELLIS
Original assignee: Shawcor Ltd.
Priority date: 2017-09-11
Filing date: 2018-09-07
Publication date: 2019-03-14
Also published as: CA3074601A1

Abstract

The invention relates to a leak detection system for detecting leaks along a length of pipeline. The leak detection system comprises a plurality of chemiresistive sensor elements which react electrically when exposed to organic liquids and vapors.

Description

HYDROCARBON LEAK DETECTION SYSTEM AND METHOD FOR PIPELINES

FIELD OF THE INVENTION

[0001] The Invention relates to an apparatus and method for the detection of liquids and vapors more specifically, for the detection of organic liquids and vapors, such as hydrocarbon based chemicals. The apparatus is particularly useful in detecting hydrocarbon liquids along a path, such as fuel leaks emanating from an oil pipeline. The apparatus contains a plurality of chemiresi stive sensor elements which react electrically when exposed to organic liquids and vapors.

BACKGROUND OF THE INVENTION

[0002] The detection of organic liquids, in particular, hydrocarbons such as fuels, is desirable. Early, accurate, and robust detection of leaks in hydrocarbon storage containers and conduits is extremely desirable, since such leaks can be very hazardous and damaging to the environment. In many cases, the hydrocarbon storage containers and conduits are underground or in remote locations; leaks can accumulate quickly over time, leading to contamination of ground water and damage to the environment.

[0003] Detection of leaks along pipelines have been a greater challenge. Oil and gas pipelines are built in some of the most remote, hostile environments on the planet, including the bottom of the ocean, in trenches across the Sahara desert, and across mountains and rough terrain. They are also built in farmers' fields and around large population centres. Oil and gas pipelines are built with the lifespan goal of many decades, and it is very difficult to predict where, along a pipeline, a leak will occur, since many variables are involved. Early, accurate and robust detection of leaks over long lengths of pipeline has been a challenge.

[0004] There are many existing systems for detection of such leaks, each with its advantages and disadvantages. One of the most commonly employed leak detection systems include use of fiber optic sensor technology, which is based on indirect measurement of temperature, strain, vibrations and/or acoustics. This often results in false positives.

[0005] Another, less commonly used system for leak detection is based on electric power cables, rather than the optical cables. The principle commonly used with these is based on change in either resistance or impedence of the "semi -conductive" insulation upon contact with hydrocarbons. Unlike the optical cables, these electrical cables senses the fuel directly by way of swelling or dissolving in the presence of the fuel, and hence reducing the possibilities of false positive signals. [0006] US patent 2,691,134, dating back to 1951, assigned to the Goodyear Tire and Rubber Company and incorporated herein by reference, discloses a device for detecting leakage of fuel from a container, which uses an electrically conductive plastic material that has resistance characteristics which are affected when fuel, such as gasoline, comes into contact with it. The plastic material is positioned at probable points of leakage around a container, and electric potential is passed through it. A change in resistance of the material is used to indicate that the material has been in contact with fuel. One embodiment of the plastic material is taught to be rubber having acetylene carbon black dispersed therethrough. The device is taught to have high sensitivity to exposure to fuel or fuel vapor. The patent also describes a group of leak-detecting devices containing this plastic material, connected on a circuit so that each device may be checked at a common point. The device is taught for discrete receptacles, such as an airplane fuel container. It is likely not suitable for use across long distances such as an oil or gas pipeline, due to the difficulty of scaling the device material's inherent resistance across long distances, and the inability of the taught device to pinpoint the location of a leak across a long distance.

[0007] US patent 4,631,952, dating to 1986, assigned to Chevron and also incorporated herein by reference, discloses an apparatus and method for sensing organic liquids, vapors and gases, utilizing a resistivity sensor comprising an intimate admixture (matrix) of conductive particles and a material capable of swelling in the presence of the liquid, vapor or gas to be detected. Swelling of the material, when placed in contact with oil or gas, causes a change in its resistance, which is easily measured. Upon exposure to the vapor, liquid or gas, the matrix swells, moving the conductive particles apart relative to one another, causing an increase in measured resistance. Exemplified materials for the matrix are synthetic rubber, polyvinyl chloride, polymethyl methacrylate, Tygon(r), silicone, and the like, with silicone being preferred, in admixture with conductive particles such as gold, platinum, silver, copper, nickel, stainless steel, ferrite, electrically conductive carbon, and the like, preferably carbon black. The conductive particles are taught to have a size range of 0.001 to 10 microns. A preferred detector material is taught to be two parts of Raven carbon black to one part RTV silicone polymer. The patent focuses again on discrete detection, for example, detection of hydrocarbon within a groundwater sample, and does not teach or contemplate detection over long distances. The swellable matrix has potential to be a reversible sensor - it is taught to return to its original resistance characteristics when the liquid, vapor or gas to which it has been subjected is removed.

[0008] US patent 4,855,706, incorporated herein by reference, describes a reversible resistivity sensor based on a mixture of electrically conductive particles and a matrix, the sensor material being swellable upon contact with a liquid but not swellable on contact with the vapor or gas of said liquid. This sensor is described to be advantageous for being able to differentiate between a liquid (which affects its resistivity) and the vapor or gas of that liquid (which does not). Again described is a discrete sensor, for detecting at a specific point. An "elongated" sensor, useful for monitoring areas or lengths rather than discrete points is also disclosed, however, the "area or length" being contemplated is likely orders of magnitude less than an oil or gas pipeline, where the inherent resistance of the sensor would make readings meaningless if one was to use the configurations described in 4,855,706 over any meaningful distance of pipeline, such as 10's or 100's of kilometers.

[0009] US 7,859,273, incorporated by reference, also teaches a point sensor for detecting organic liquids using the swelling properties of silicone. A silicone/graphite based conductive matrix sensor is reversibly swellable in the presence of an organic liquid. The sensor can be formed on a printed circuit board, and the circuitry may convert a detected analog resistance to a binary output - providing one output when the resistance of the sensor corresponds to no contact with an organic liquid, and another output when the resistance of the sensor corresponds to contact with an organic liquid. The sensor may be mounted in a protective housing such as a tube.

[0010] US 6,777,947, incorporated by reference, relates to a cable for detecting corrosive liquids and for detection of the location of leaks. The cable comprises two sensing wires, and a core member around which the sensing wires are wrapped. The sensing wires have a center conductor and at least one conductive layer; one of the sensing wires has a non-conductive surface layer. The non-conductive surface layer is made of a material that, upon contact with the corrosive liquid, dissolves or is solubilised, exposing the conductive layer. This creates an electrical connection between the two sensing wires, which can be measured, and which is indicative of a leak somewhere along the sensing wires. The cable is advantageous over point sensor systems previously described because it can sense corrosive material continuously along the length of the wire. However, the location of the leak, along the sensing wire, is more difficult to pinpoint. The cable is also fairly complex and expensive, containing a continuity wire, at least two sensing wires, one of which is jacketed with a conductive polymer or a dissolving non-conductive surface layer, and various separator or containment braids. It appears that the entire cable is also disposable upon sensing a leak, since the corrosive material irreversibly changes the cable by dissolving the non-conductive surface layer of one of the sensing wires.

[0011] US 9,513, 185, incorporated by reference, also relates to a cable for detecting leaks of an electrically nonconductive liquid, such as a hydrocarbon. The cable contains a continuity wire, a power wire, a ground wire, a digital communication wire, and a detection/return wire, all within a loose braid which allows passage of hydrocarbon into the braid. The detection/return wire comprises a layer of a swellable silicone material that is conductive when it is not in the presence of a hydrocarbon leak, and is not conductive when in presence of a hydrocarbon leak - the swelling of the silicone material interrupts the conductivity of the cable. [0012] WO 2015/054784, incorporated by reference, describes a complex sensor system for detecting and monitoring structures for hydrocarbon leaks. The system comprises a sensor containing an admixture of conductive particles and swellable polymer, and a very elaborate circuit structure comprising a plurality of said sensors, forming a "skin" on the pipe or structure to be monitored. The system is extremely complex and appears to require a staggering amount of circuitry for effective monitoring of leaks on a relatively small scale.

[0013] A system utilizing a dissolvable or swellable conductive polymer admixture or matrix, as a sensor, that is able to detect leaks over long distances in a simple, robust, and effective manner, is desirable.

BRIEF DESCRIPTION OF THE FIGURES

[0014] Figure 1 A shows, in schematic view, a leak detection system of the present invention.

[0015] Figure IB shows, in schematic view, a further embodiment of the leak detection system of the present invention.

[0016] Figure 2 shows a further embodiment of the leak detection system of the present invention, derived from the system shown in Figure 1.

[0017] Figure 3 shows a further embodiment of the leak detection system of the present invention, derived from the system shown in Figure 2.

[0018] Figure 3 A shows further embodiments of the leak detection system of the present invention.

[0019] Figure 4 shows a modular, scalable leak detection system of the present invention, derived from the system shown in Figure 2.

[0020] Figure 5 shows a modular, scalable leak detection system of the present invention, derived from the system shown in Figure 3.

[0021] Figures 6A-D shows a schematic of further embodiments of the leak detection systems of the present invention.

[0022] Figure 7 shows a further embodiment of the leak detection system of the present invention, showing a parallel leak detection system with a communication line.

[0023] Figures 8-10 shows a further embodiment of the leak detection system of the present invention, derived from the system shown in Figure 7. [0024] Figure 11 shows a schematic of a further embodiment of the leak detection system of the present invention, derived as a hybrid of the system shown in Figure 3 and the system shown in Figure 6.

[0025] Figure 12 shows a modular, scalable leak detection system of the present invention, derived from the system shown in Figure 10.

[0026] Figure 13 shows a further embodiment of the leak detection system of the present invention.

[0027] Figure 14 shows a cross section of a cable comprising a further embodiment of the leak detection system of the present invention.

[0028] Figure 15 shows a schematic representation of the cable shown in Figure 14.

SUMMARY OF THE INVENTION

[0029] According to one aspect of the present invention is provided a leak detection system comprising a conductive wire or tape, intermittently and repeatedly conductively interrupted by a plurality of lower conductivity sensors which swell or dissolve when placed in contact with a hydrocarbon, wherein each of said conductive sensors comprises (a) a

hydrocarbon swellable polymer, and/or (b) a hydrocarbon dissolvable polymer; in admixture with a conductive filler.

[0030] According to a further aspect of the present invention is provided a leak detection system comprising: (a) a continuous conductive sensor which swells or dissolves when placed in contact with a hydrocarbon, said continuous conductive sensor comprising (i) a hydrocarbon swellable polymer and/or (ii) a hydrocarbon dissolvable polymer in admixture with a conductive filler; and a plurality of non-continuous, low resistance conductive elements interspersed or intermittent within or otherwise conductively connected to said continuous conductive sensor.

[0031] According to certain embodiments, the hydrocarbon swellable polymer comprises any one or more of ethylene vinyl acetate, silicone, polyvinyl chloride, polymethyl methacrylate, Tygon(r), and synthetic rubber.

[0032] In certain embodiments, the hydrocarbon dissolvable polymer comprises any one or more of ethylene vinyl acetate, wax, proteins, and polyisobutylene.

[0033] In certain embodiments, the polymer is partially crosslinked.

[0034] In certain embodiments, the conductive filler comprises any one or more of microparticles or nanoparticles of: powdered graphite, crystalline graphite, carbon black, copper, aluminum, conductive polymers, nickel, gold, platinum, silver, copper, stainless steel, ferrite, electrically conductive carbon, graphene, carbon nano-tubes, carbon fibers, copper; and microspheres coated with or containing any one or more of said microparticles or nanoparticles.

[0035] In certain embodiments, the leak detection system also comprises a power source, connected to an end of the conductive wire or tape, or to the conductive sensor, and a resistance meter connected to an opposing end of the conductive wire or tape or conductive sensor.

[0036] In certain embodiments, the conductive wire or tape and the plurality of conductive sensors are affixed to an oil resistant flexible tape backing.

[0037] According to a further aspect of the present invention is provided a scalable leak detection system, comprising: (a) a plurality of sensor modules, each comprising a sensor, means for measuring a resistance across the sensor, and means for relaying: (x) information regarding the resistance across the sensor; and (y) a sensor identifier; through a communications line; (b) a power line for powering the plurality of sensor modules; and (c) a communications line.

[0038] In certain embodiments, the scalable leak detection system further comprises a communications bus for receiving the information relayed from the plurality of sensors through the communications line.

[0039] In certain embodiments, in the scalable leak detection system, the information relayed is in a digital form.

[0040] In certain embodiments, the scalable leak detection system comprises, as a sensor, a leak detection system as hereindescribed.

[0041] According to a further aspect of the present invention is provided a hybrid leak detection system comprising the scalable leak detection system and a parallel, discrete, RF leak detection system.

[0042] According to a further aspect of the present invention is provided a method of detecting a leak along a length of pipeline, or adjacent to a physical structure running alongside of said length of pipeline, comprising a leak detection system as hereindescribed.

[0043] According to a further aspect of the present invention is provided a method of detecting a leak along a length of pipeline, or adjacent to a physical structure running alongside of said length of pipeline, comprising the hybrid leak detection system as hereindescribed, said method comprising: (a) passing a current through the scalable leak detection system and detecting a leak by detecting an increase in resistance; and (b) pinpointing the leak to a specific location along the length of pipeline by utilizing a sweep frequency response analysis of a sensitive transmission line or waveguide. DETAILED DESCRIPTION

[0044] A leak detection system encompassing swellable or dissolvable sensors, in a serial, parallel, or hybrid detection array, is disclosed. The system is capable of being deployed over long distances of pipeline, and offers a commercially desirable detection interval and measurement interval resolution. The system is robust, inexpensive, highly sensitive and easy to deploy, relative to other known systems.

[0045] The system utilizes conductive polymer technology as a sensor for hydrocarbon. A "conductive polymer" is typically a polymer in admixture with a conductive filler, such as a conductive carbon filler. The polymer may be any polymer which dissolves or swells in the presence of hydrocarbon. Hydrocarbon dissolvable polymers may include ethylene vinyl acetate, wax, proteins, polyisobutylene, and mixtures thereof. Swellable polymers may include silicone, polyvinyl chloride, polymethyl methacrylate, Tygon (R), synthetic rubber, and mixtures thereof. The conductive filler may be powdered graphite, crystalline graphite, carbon black, such as acetylene carbon black, copper, aluminium, conductive polymers and particles, microparticles, or nanoparticles of nickel, gold, platinum, silver, copper, aluminium, conductive polymers, stainless steel, ferrite, electrically conductive carbon, graphene, carbon nanotubes, copper, and/or microspheres coated with the previously mentioned conductive compounds. The sensor can be an admixture of the polymer and the conductive filler to from a conductive composite. In the case of a swellable polymer, on contact with oil/hydrocarbon, the polymer swells, causing the relative distance between conductive fillers to increase and the conduction paths to break, thus increasing the resistance of the sensor to electrical current. In the case of a dissolvable polymer, on contact with oil, the polymer dissolves, breaking the conduction path and dramatically increasing the resistance of the sensor to electrical current. This increase in resistance can be quite rapid, depending on the polymer and the hydrocarbon types, occuring over a span of a few minutes to a few days from exposure to the hydrocarbon. Swellable polymer sensors may, for example, increase in resistance from a baseline of about 1.5 kQ to over 3 kQ. Dissolvable polymers may, for example, increase in resistance from a baseline of about 1.5 kQ to potentially near infinite resistance.

[0046] Example 1 : Serial Leak Detection System

[0047] Figure 1 A shows, in schematic view, a leak detection system of the present invention in its most simple form. The power source 2 sends power through sensor 6, which is a conductive polymer, and may be a swellable polymer, or a hydrocarbon dissolvable polymer, as previously described. Detection apparatus 8, such as a simple ohm meter, reads the resistance in the line. If the polymer comes into contact with a hydrocarbon, the polymer will swell or dissolve, greatly increasing the resistance in the line, which can be measured as an indicator of leakage. In its most basic form, the system cannot determine the location of the leak along the sensor 6, but can determine and indicate that a leak has occurred over the length of the line. [0048] The serial leak detection system of Figure 1 A is somewhat limited by the natural resistance of the conductive polymer, which is typically much more resistant to electrical flow than, for example, a copper or aluminum wire or strip. For example, it was found that a sensor tape made from ethylene vinyl acetate/graphene compound of distance 100 meters displayed a resistance of 2.1 ΜΩ. Upon exposure to oil, the resistance increased to 2.9 ΜΩ. This change was less than optimal to reliably validate the occurrence of an oil leak. It was found that the resistance change of the system should preferably be at least two times the initial resistance, but more preferably three to ten times in order to avoid false positive signals.

[0049] A serial leak detection system with a much longer range is described in Figure IB. Power source 2 sends power through conductive wire or tape 4, which is interrupted

intermittently with sensor 6. Sensor 6 is a conductive polymer, which may be a swellable polymer, or a hydrocarbon dissolvable polymer, as previously described. Detection apparatus 8, such as a simple ohm meter, reads the resistance in the line. Sensors 6 can be arranged at any desirable detection interval 12. For example, the leak detection system may have sensors 6 placed every metre, for a detection interval 12 of about one metre. The leak detection system may also have any desired measurement interval 14. For example, the leak detection system may have a measurement interval 14 of about 20 metres. In an example with a detection interval 12 of one metre and a measurement interval 14 of 20 metres, there would be 19 to 20 sensors 6 on the line. As described earlier, sensor 6 either swells, or dissolves, in the presence of hydrocarbons, such as an oil leak. This swelling or dissolving causes an interruption in the power signal sent from power source 2 to the detection apparatus 8, which is easily measured and indicates an oil leak at some point within measurement interval 14.

[0050] The novel basis of the design described in Figure IB is the deployment of discrete sensors over a long distance, while maintaining a relatively low initial resistance for the system, such that upon exposure to hydrocarbons, a two or preferably three times increase in the resistance or even higher is obtained.. For example, in Figure 1A, the sensor is a continuous tape and has a dimension of 100 m length x 5 mm width x 1.0 mm thickness. The resistance of the sensor was measured to be 2 ΜΩ. This was found to be too high of an initial resistance, as described above. However, if 1000 discrete sensor are deployed to comprise the system, with each sensor having a dimension 10mm long x 5mm wide xl .Omm thick, as shown in Figure IB, the cumulative resistance would be about 200 kΩ. Each discrete sensor was measured to have a resistance of about 0.2 kΩ. If 1000 discrete sensors are spaced 1.0 m apart, as shown in Figure IB, an overall sensor system of of 1.0 km length would be obtained, with a total resistance of 200 kΩ. It was found that with a sensor of 200 kΩ, upon exposure to hydrocarbons, the resistance readily escalates to three times the initial resistance within 10 - 30 minutes, and then to over 10 times in hour, depending on the sensor composition and the hydrocarbon type. This novel concept of dispersed discrete sensors allows fabrication of sensor cables over long distances (1000's of meters long) that are able to maintain an initial line resistance low enough for reliable measurement and hydrocarbon detection versus the continuous sensor tape.

[0051] Figure 2 shows a further embodiment of the leak detection system of Figure IB. Here, the conductive tape 4 is affixed to or imprinted onto an oil resistive flexible tape backing 10. The tape backing may be made of any appropriate composition which provides suitable flexibility, strength, and adherence to the conductive tape 4 and sensors 6. Flexible tape backing can be, for example, PET (polyethylene terephthalate). In certain preferred embodiments, for example, a nylon (polyamide) tape backing 10 can be used. The conductive tape 4 is applied by printing or extrusion etc. onto the tape backing, with gaps for sensors 6. Sensors 6 are then bonded or adhered to tape backing 10, for example by 3D printing, in electrical contact with conductive tape 4. As in the example of figure 1, when hydrocarbons, such as from an oil leak, come into contact with one or more sensor 6, the electrical signal from power source 2 to detection apparatus 8 is disrupted, in a manner which is easily measured and indicates the presence of an oil leak at some point within measurement interval 14.

[0052] Figure 3 shows a further embodiment of the leak detection system of Figure 2.

The system is similar, but contains return line 16 to enable the power source 2 and the detection apparatus 8 to be on the same side of the system. As would be understood by a person of skill in the art, this would enable the power source 2 and the detection apparatus 8 to be contained in a single module if desired. The cable design could be based on the tape system illustrated in Figure 2, where by the conductive tape 4 and the polymer sensor 6 is affixed to the flexible tape 10, and a parallel conductive tape 16 is affixed adjacently as a return wire, An alternate design for the fabrication of this concept is shown in Figure 3 A. This design enable the cable to be manufactured continuously by a cross-head extrusion process, and having a subsequent step for a notching machine to cut out a section of the sensor wire 4, thus creating a gap in the sensor wire circuit. The gap is connected by the sensor polymer 6 that remains on the rest of the cable as jacketing material. While the sensor wire is highly conductive, the higher resistance sensor polymer 6 will carry small current via the bridging at the notch area, and thus provide a defined resistance value, for example 0.2 kQ similar to the design shown in Figure IB. The construction of the cable design given in figure 3 is one example embodiment. It would be understood that other construction methods are also possible. For example, a cable construction whereby a gap is created in a continuous conductive wire or tape, and encapsulation of the gap with the sensor material. For example, a coax cable can be adapted to make a sensing cable with the described discrete sensors. A coax cable typically comprises of an inner conductor with an insulation, which is covered with some kind of conductive shielding material, for example, a copper braid. In this example, the shielding component is converted into a sensing cable, by cutting out discrete sections in the braid to create gaps, then encapsulating the gap with a sensor material. [0053] Figure 4 shows a further embodiment of the leak detection system of Figure 2. Here, the leak detection system is modular and scalable. Connector assembly 22 is used to connect two tape backings 10. In this manner, the leak detection system can be easily manufactured in defined lengths, which connect to one another to monitor longer sections of pipeline. For example, each defined length may be 20 metres, 10 of which can be connected to one another to form a 200 metre system. Figure 5 shows a modular and a scalable leak detection system of Figure 3. This system, while modular, requires two types of lines - an end line 17, with only one connector assembly 22 and the loop 15 of the return line 16, and an extension line 19, which has connector assemblies 22 at both ends. In certain embodiments (not shown), the system also has a third line - a beginning line, which is equivalent to an extension line 19, but with a built in power source 2 and/or detection apparatus 8.

[0054] The leak detection systems described above can be manufactured as shown in Figures 1-5, with "discrete" sensors 6 applied onto flexible tape backing 10. However, it would be advantageous from a manufacturing point of view, that in some instances to apply the sensor as a continuous laminate overtop of, or an extrusion surrounding, tape backing 10. Figure 6A is a cross-sectional, generally schematic representation of a leak detection system wherein sensor 6 is applied as a generally uniform laminate overtop of the flexible tape backing 10 onto which conductive tape 4 has been applied. As would be appreciated by a person of skill in the art, because conductive tape 4 is much more conductive than sensor 6, the overall resistance of such a leak detection system is generally equivalent to a system having only discrete sensors 6 as shown in Figure 2. Similarly, Figure 6B shows a cross-sectional, generally schematic representation of a leak detection system wherein sensor 6 is extruded overtop of the flexible tape backing 10 on which conductive tape 4 has been applied. As shown, the extruded sensor 6 completely envelops the conductive tape 4 and flexible tape backing 10. Such a system has an overall resistance generally equivalent to an equivalent system having discrete sensors as shown in Figure 2. Such a system has the added advantage that the sensor 6, which is an extruded polymer compound, provides some protection to conductive tape 4 and flexible tape backing 10.

[0055] In a further embodiment of the present invention, illustrated schematically in Figure 6C, the conductive tape and flexible tape backing is replaced by strips 5 of the conductive material. The strips of conductive material can be blended into the sensor polymer before extrusion, and extruded out with the molten sensor polymer to form the sensor tape. This results in a generally random distribution of conductive material strips 5 over the length of the sensor. This dramatically decreases the resistance, allowing for the sensor to be utilized over longer distances. Alternatively, material strips can be placed or inserted into the molten sensor polymer, or adhered overtop of the dry, extruded, sensor polymer.

[0056] Interestingly, electrically discontinuous shielding tape, sleeves, and strips are commercially available from a variety of manufacturers, for use as electromagnetic interference (EMI) shielding. Often, discontinuous shielding tape comprises discrete electrically conductive patches with shape, thickness and spacing designed to mitigate interactions with the transmitting electrical signals. Discontinuous shielding tape may be adhesive backed. Discontinuous shielding tape, sleeves or strips can be excellent starting materials for use in manufacturing of leak detection systems of the present invention, replacing or supplementing conductive tape 4 and flexible tape backing 10. For example, a sensor polymer 6 may be laminated onto a discontinuous shielding tape 7 to form a system such as the one schematically depicted in Figure 6D.

[0057] Example 2 - Parallel Leak Detection System with Communication Line

[0058] As can be appreciated, the leak detection system of Example 1 is excellent since it is simple and robust. However, over extremely long lengths, the resistance accumulated over a plurality of lengths of conductive wire or tape 4 and sensor 6 may become quite high. The higher this baseline resistance, the more difficult it is to determine whether a sensor has sufficiently swelled or dissolved.

[0059] The parallel leak detection system of Example 2 addresses this challenge. A schematic of this system is shown in Figure 7. Here, the power source 2 provides both a power line 26 and a ground line 24 spanning the length of the system. A plurality of sensor modules 28 each tap into this power line 26. The sensor modules 28 contain a swellable or dissolvable conductive polymer, as described above, and a system for measuring the resistance across this polymer when power is passed through it. This system also has means for relaying a

communication signal down the communications line 30, which can be read or relayed by communications bus 32. Thus, in this system, the length is essentially infinitely scalable, since the resistance along the power line is not relevant to the measuring of the leak. Interestingly, in this system, as depicted in Figure 7, the detection interval 12 and the measurement interval 14 are identical, meaning the source of the leak can be pinpointed within the distance between any two sensors.

[0060] Figures 8 and 9 show an embodiment of this parallel leak detection system. A cable 37 comprises an external jacket 36 and a shielding and/or reinforcing braid 34, enclosing ground line 24, power line 26 and communication line 30. The cable 37 is interspersed with a plurality of sensor socket 38 along its length. The sensor socket 38 is a waterproof housing for connecting the lines contained within cable 37 to sensor body 44, through sensor connectors 40 and sensor socket connectors 42. Sensor body 44 comprises a weatherproof o-ring 46 which seals sensor body 44 when fixed to sensor socket 38. Sensor body 44 also comprises conductive polymer strip 54 which is operatively connected at both ends to Printed circuit board 60 which contains microprocessor and circuits 58 which are, in turn, operatively connected to sensor socket connectors 42. Polymer sensor strip 54 may be affixed to sensor body 44 with another weatherproof o-ring 60 to prevent damage to the microprocessor and circuits 58. Polymer strip 54 is surrounded by shroud 50 containing a plurality of apertures 52 which are large enough and in sufficient quantity to admit hydrocarbons while still allowing the shroud 50 to protect the polymer strip 54 from impact damage and the like.

[0061] Microprocessor and circuits 58 send power through the polymer strip 54 and measure the resultant resistance. Where there is a change in resistance indicating an oil leak, microprocessor and circuits 58 send a signal to communication line 30 indicating that this is the case.

[0062] As can be appreciated, a digital signal can be used, which may also indicate a unique identifier for the specific sensor body 44, which will allow a user to pinpoint the exact location of the leak to a single sensor body 44.

[0063] Leak detection can be continuous, by constantly sending power through the polymer strip 54, or it may be controlled remotely, for example, by sending a signal to the sensor body 44 through communication line 30. For example, each sensor body 44 along the line, having a unique identifier, could be signalled, sequentially or in a user-defined order, to test the polymer strip 54. Testing each sensor body 44 intermittently, rather than having constant testing, may extend the usable life of the system, and decrease power consumption. For example, sensor microprocessor and circuits 58 can be "woken" once an hour by a signal from communications line 30, perform a near-instantaneous measurement of the resistance of the polymer strip 54, send a signal back along line 30, then go back to sleep, with the entire testing routine taking less than one second. In this manner, hundreds, or thousands, of sensor bodies 44 can be routinely and individually tested in sequence quite easily, allowing for the system to measure leaks over kilometers with meter accuracy.

[0064] As can also be appreciated, with a sophisticated digital system such as this one, in the case of sensor failure, an individual sensor could be "shut down" remotely, or simply ignored.

[0065] As can be illustrated in Figure 10, the parallel leak detection system features a detection interval 12 which is identical to the measurement interval 14.

[0066] Example 3 - Hybrid leak detection system.

[0067] As can be appreciated, the leak detection system of Example 2 is excellent in that it provides a robust, easy to install system that provides a lot of information about the size and location of a leak, extreme accuracy in measurement interval (the measurement interval is identical to the detection interval), and extreme customization in that each sensor can be activated and deactivated individually. However, as can also be appreciated, having relatively sensitive and relatively expensive electronics at each sensor socket is not ideal in some situations, and many situations may not need the resolution this system provides. [0068] The "hybrid" leak detection system of Example 3 addresses this challenge, by combining the advantages of the systems of Example 1 and 2 into a hybrid system.

[0069] Figure 11 shows a schematic view of an exemplification of the hybrid leak detection system of the present invention. Power source 2 provides power via ground line 24 and power line 26 along the length of the system. Local printed circuit board 62 draws power from the power line 26 and works much like the printed circuit board 56 and microprocessor 58 of Example 2. However, in Example 2, the printed circuit board 56 and microprocessor 58 test one conductive polymer sensor 54. In this hybrid system, the local printed circuit board 62 tests a serial leak detection system of Example 1 with certain length. That is, local printed circuit board 62 sends power down line 4, through a plurality of sensors 6, and back to the local printed circuit board 62 through return line 16. Thus, the local printed circuit board 62 can be controlled, and can send signals along communications line 30 much like in Example 2, but it "reads" a plurality of sensors. Regional PCB 64 receives signals from the plurality of local printed circuit boards 62, and processes these signals to permit the user to determine whether, and where, a leak exists along the system. Optionally, regional PCB 64 also sends signals to the local printed circuit boards 62 to "wake" or "sleep" the circuits. This system provides the low cost and robustness of Example 1, extended along long distances, with acceptable measurement interval 14 much like Example 2.

[0070] Figure 12 shows one exemplification of the hybrid leak detection system of the present invention. Figure 12 shows one length of cable; a plurality of such cables can be connected end to end through connectors 66, 68. As shown, each length of cable is one "digital node", with one local printed circuit board 62 (as described for Example 2) either imbedded within the cable (as shown), or within one of the connectors 66, 68 (not shown). Each length of cable comprises a plurality of sensor sockets 38, each containing a conductive polymer sensor 54 connected in serial to the other conductive polymer sensors housed in the other sensor sockets 38, and in turn to the local PCB 62. Each polymer sensor 54 is protected by shroud 50 as described in Example 2.

[0071] This system allows for increased robustness, since each sensor housing is smaller and does not need to contain electronics. Electronics can be protected and integrated into the cable, as shown, or integrated into the cable connector, depending on which is easiest to manufacture. In this manner, the system can easily detect oil leaks for many kilometers. For example, with a 30 metre cable, each cable having sensor sockets containing simple sensors at every metre, a system of 255 nodes (each node being one cable, with one local printed circuit board 62) could cover a distance of over 7.5 km, with a detection interval 12 of 1 metre and a measurement interval 14 of 30 metres, which would be quite suitable for pipeline applications - leaks could be detected at every metre of pipeline, and reported back with 30 metre accuracy, which is more than adequate for damage minimization purposes. [0072] Example 4 - Long-distance Serial-based Leak Detection System

[0073] As discussed above, one of the disadvantages of the serial leak detection system of Example 1 is that, over extremely long distances, the resistance accumulated can be quite high; the higher the baseline resistance, the more difficult it is to determine whether a sensor has swelled or dissolved. The long distance serial-based leak detection system provides the robust and simple system over long distances.

[0074] Figure 13 shows this further embodiment of the leak detection system.

Conductive tape 4 is affixed to or imprinted onto an oil resistant flexible tape backing 10, with gaps for sensors 6, which are bonded or adhered to the tape backing 10, in electrical

communication with the conductive tape 4. It would be appreciated to someone of skill in the art that, instead of as shown, the sensors 6 could be extruded or laminated onto the entire surface of the flexible tape backing 10, or the flexible tape backing 10 could be coated, in its entirety, with the conductive oil swellable or oil soluble polymer that is used to make sensors 6, since the resistance of the sensor 6 is typically orders of magnitude higher than the resistance of conductive tape 4. At intervals, a portion of conductive tape 4 (or, as shown, sensor 6) is fed to a return line 16, optionally, but not necessarily, through a one way diode 88. Lead lines 80, 82, 84, 86, complete the circuits. In this way, the system comprises a plurality of serially-connected sensors, each individually testable to create measurement interval 14 and detection interval 12, as shown. A multiplex apparatus 90 can be used to rapidly switch and measure the resistance coming from the various circuits. In the case of a leak, resistance at one of the sensors 6, proximal to the leak, will increase, and can be measured.

[0075] Example 5 - Long Distance Hybrid System Using Network Analyzer

[0076] Use of S-parameters responses from a vector network analyzer (VNA) and/or time domain reflection and transmission (TDR/TDT) measurements can be used to approximate the location of a leak. See, for example, US patent Nos. 5,410,255, and 4,797,621, and the PAL-AT coaxial cable and probe system available from PermAlert Environmental Specialty Products, inc. Cables and monitor boxes are commercially available, and fairly proficient at detecting and positioning leaks. However, the cost of monitoring, including the sophisticated, computerized, monitoring panels, is not commercially viable for monitoring over hundreds of kilometers of pipeline. Currently commercially available panels from PermAlert, for example, have a maximum range, for the most expensive panel (AT80K), of 7,500 feet (2.5 km).

[0077] In contrast, the Long-distance Serial -based leak detection system of Examples 1 or 4 provide a extremely robust, low maintenance detection of leaks over long distances, but does not provide pinpointing of exactly where the leak is, over that distance. [0078] The long distance hybrid system of this example utilizes two sensor cables - a first similar to that shown in Examples 1 and 4, and a second similar in construction to coaxial cables but designed to meet the specific low structural return loss and low attenuation

requirements for this application and desired frequency of operation. The first cable provides simple, robust and cheap monitoring, with a detection interval and a measurement interval that is, for example, the length of the cable - for example, 1 km. This could be continuously monitored via data transmission to a satellite or other wireless means. The second cable provides leak resolution (detection and measurement interval) of a much shorter interval, i.e. 10 meters , depending on the dynamic range of the system, at a given range of frequencies and cable design. Optionally, and as shown in Figure 14 (showing a cross-section of a sensor cable having both a long distance serial-based leak detection system and a VNA leak detection system), both cables are integrated in one hybrid cable 94. Figure 14 shows a single hybrid cable 94, in cross section. The cable comprises a core 95, made out of a material that provides EMI shielding, floor noise reduction, pull strength and the appropriate shape and impact resistance. Within an opening or groove in the core 95, and accessible to the outside environment, are a resistance sensor cable 97 or strip, as previously described as the leak detection systems of Examples 1 and 4. Also within an opening or groove in the core 95 is a VNA leak detection cable 99 as commercially available. Finally, and optionally, the core 95 may have a further opening or groove for a further cable 101 that is either a spare cable, a ground cable, or a communications cable. Optionally, the hybrid cable 94 can be enveloped in sheath 103, for example a braided sheath, which would be porous to hydrocarbons.

[0079] The leak detection system of Example 5 can be seen, in a generally schematic form, as applied onto a section of pipeline 105, in Figure 15. The hybrid detection cable 94 is run along the length of the pipeline 105, in close proximity to the pipeline 105. The hybrid detection cable 94 has resistance detection nodes 107 and VNA detection nodes 109 at regular intervals along its length. Resistance detection nodes 107 measures the resistance along a discrete length of the hybrid detection cable 94, by measuring resistance of the resistance sensor cable 97. For example and as shown in Fig. 15, each resistance detection node 107 measures the resistance along one km of the resistance sensor cable 97. The resistance detection node 107 is, in preferred embodiments, above ground (even where the hybrid detection cable 94 and the pipeline 105 are below ground), so that it can be easily accessed for power supply, measurement and data transmission as well as for repairs and maintenance. The resistance detection node 107 continuously, or optionally, at programmed intervals or on demand, measures electrical resistance along the resistance sensor cable 97, and sends a signal when the resistance spikes (i.e. when a leak is detected). In certain embodiments, the resistance detection node 107 is wirelessly connected, operated, and measured from a remote location. It is noted that in certain

embodiments, and as shown, the location of the leak along the 1 km of resistance sensor cable 97 on which resistance is measured is not known, but a user will then know that somewhere along that km there is a hydrocarbon leak. For each resistance detection node 107, there is also a RF detection node 109, which is also above ground, and connected to the RF detection cable 99. However, the RF detection node 109, in preferred embodiments, does not comprise a RF detection panel.

[0080] In use, when a leak is detected through the measurement of resistance along the resistance sensor cable 97 by resistance detection node 107, a user is alerted. The user will know which km location of pipeline contains the leak, but not where along that km the leak is located. A user can then drive or otherwise travel to the location of the resistance detection node 107 which has detected a leak, and can connect a detection panel (either a frequency or time domain measurement system)to the corresponding RF leak detection cable 99, through RF detection node 109, in this manner pinpointing the leak, often to a 5-10 m location along the 1 km.

[0081] In this manner, installation and operation cost is dramatically decreased over the use of RF leak detection cable along the entire length of the pipeline, since the time domain or frequency domain network analyzer, a major cost and wear point, is only utilized to pinpoint a leak once a leak has been identified using the relatively cheaper, robust, resistance leak detection system of the current invention.

Claims

CLAIMS What is claimed is:

1. A leak detection system comprising a conductive wire or tape, intermittently and

repeatedly conductively interrupted by a plurality of lower conductivity sensors which swell or dissolve when placed in contact with a hydrocarbon, wherein each of said conductive sensors comprises (a) a hydrocarbon swellable polymer, and/or (b) a hydrocarbon dissolvable polymer; in admixture with a conductive filler.

2. A leak detection system comprising: (a) a continuous conductive sensor which swells or dissolves when placed in contact with a hydrocarbon, said continuous conductive sensor comprising (i) a hydrocarbon swellable polymer and/or (ii) a hydrocarbon dissolvable polymer in admixture with a conductive filler; and a plurality of non-continuous, low resistance conductive elements interspersed or intermittent within or otherwise conductively connected to said continuous conductive sensor.

3. The leak detection system of claim 1 or 2 wherein the hydrocarbon swellable polymer comprises any one or more of ethylene vinyl acetate, silicone, polyvinyl chloride, polymethyl methacrylate, Tygon(r), and synthetic rubber.

4. The leak detection system of claim 1 or 2 wherein the hydrocarbon dissolvable polymer comprises any one or more of ethylene vinyl acetate, wax, proteins, and polyisobutylene.

5. The leak detection system of any one of the preceding claims where the polymer is

partially crosslinked.

6. The leak detection system of claim 1 or 2 wherein the conductive filler comprises any one or more of microparticles or nanoparticles of: powdered graphite, crystalline graphite, carbon black, copper, aluminum, conductive polymers, nickel, gold, platinum, silver, copper, stainless steel, ferrite, electrically conductive carbon, graphene, carbon nano-tubes, carbon fibers, copper; and microspheres coated with or containing any one or more of said microparticles or nanoparticles.

7. The leak detection system of claim 1 or 2, further comprising a power source, connected to an end of the conductive wire or tape, or to the conductive sensor, and a resistance meter connected to an opposing end of the conductive wire or tape or conductive sensor.

8. The leak detection system of claim 1, wherein the conductive wire or tape and the

plurality of conductive sensors are affixed to an oil resistant flexible tape backing.

9. A scalable leak detection system, comprising: a. a plurality of sensor modules, each comprising a sensor, means for measuring a resistance across the sensor, and means for relaying: (x) information regarding the resistance across the sensor; and (y) a sensor identifier; through a communications line;

b. a power line for powering the plurality of sensor modules;

c. a communications line.

10. The scalable leak detection system of claim 8 further comprising a communications bus for receiving the information relayed from the plurality of sensors through the

communications line.

11. The scalable leak detection system of claim 8 wherein the information relayed is in a digital form.

12. The scalable leak detection system of claim 8 wherein the sensor comprises a leak

detection system of claim 1.

13. A hybrid leak detection system comprising the scalable leak detection system of claim 1 or 2 and a parallel, discrete, RF leak detection system.

14. A method of detecting a leak along a length of pipeline, or adjacent to a physical

structure running alongside of said length of pipeline, as the hybrid leak detection system of claim 12, comprising:

a. passing a current through the scalable leak detection system and detecting a leak by detecting an increase in resistance;

b. pinpointing the leak to a specific location along the length of pipeline by utilizing a sweep frequency response analysis of a sensitive transmission line or waveguide.