Description

COMPLEX PIPE MONITORING Technical Field

[0001] This invention relates to apparatus for monitoring a plurality of inner conduits housed within a tubular housing. More particularly, the invention relates to apparatus for monitoring a plurality of inner conduits housed within a tubular housing used in the oil and gas or the like industry.

Background Art

[0002] Conventionally oil and gas or the like industrial operations and production facilities involve continuous monitoring of the pipes used to transport various pressurised fluids to and from these operations or facilities. Continuous monitoring of the pipes is required to detect damage or breakage on a portion of the pipe.

[0003] In sub-sea oil and gas production or exploration operations, complex pipes carry fluids and/or electric cabling in both directions between the well head on the seabed and a platform on the surface or between two surface platforms. A platform may be fixed to the seabed or floating being anchored to the seabed using mooring lines. When a floating vessel is used, termed an FPSO (floating production storage and offloading) vessel, the complex pipes are preferably somewhat flexible to accommodate movement of the surface vessel and of the ocean currents. The complex pipes should preferably be able to flex during installation and retrieval.

[0004] Complex pipes may be deployed in a variety of shapes such as a "free hanging," "steep wave" and "U shape." Of course movements of the FPSO and the force of ocean currents may cause the shape of riser pipes to change.

[0005] Many different factors such as, for example, the force of ocean currents, the movements of the FPSO relative to the well head and movements of various parts of the pipes relative to other parts of the pipes, may also cause damage to the pipes. These factors cause damage to the pipes as a result of strain occurring on various points on the pipes. This strain may arise from bending, twisting, compression and pulling of the pipes. Pipes may also be damaged by banging or scraping against other objects such

as rocks, parts of the structure of the platform or parts of the sub-sea structure of the well installation.

[0006] In addition to monitoring the integrity of the pipes themselves, it is also desirable to monitor the integrity and functionality of pipes or conduits which are housed within some of these pipes. Mere monitoring of the external pipe in which these internal conveying pipes or conduits are housed does not necessarily provide adequate monitoring of the internal pipes or conduits.

[0007] The current invention provides an apparatus and method for monitoring the structural integrity and functioning of the internal pipes of complex pipes by providing sensors which are in close proximity to the internal pipe or conduit intended to be monitored. In this way a more accurate assessment of the structural integrity and functioning of the internal pipes may therefore be provided.

Disclosure of Invention

[0008] One aspect of the invention provides apparatus for monitoring a plurality of inner conduits for use in the oil or gas industry, the inner conduits being eccentrically housed within a tubular housing, the apparatus comprising:

- at least one sensor carrier located in the space between the inner conduits and the tubular housing;

- the sensor carrier having at least one optical fibre sensor means; and

- the sensor carrier being proximate at least one inner conduit.

[0009] In one form of the invention there may be as many sensor carriers as there are inner conduits to be monitored. Further according to the invention, each of the inner conduits may have at least one sensor carrier associated with it.

[0010] Even further according to the invention at least one of the inner conduits may have a portion of a sensor carrier associated with it. In one form of the invention each of the inner conduits has a portion of the sensor carrier associated with it.

[0011] The optical fibre sensor means may be used to monitor at least one physical parameter of at least one inner conduit, the physical parameter

consisting of the temperature, strain, pressure or vibration of the inner conduit.

[0012] In one form of the invention the integrity of the or each inner conduit is monitored. In another form of the invention the content within the or each inner conduit is monitored.

[0013] The invention also relates to a method of monitoring at least one inner conduit of a plurality of inner conduits housed within a tubular housing for use in the oil or gas industry, the method comprising, locating at least one sensor carrier in the space between the inner conduit and the tubular housing, the sensor carrier having at least one optical fibre sensor means and the sensor carrier being proximate the inner conduit.

[0014] In one form of the method of the invention the integrity of the inner conduit is monitored. In another form of the method of the invention the contents within the inner conduit is monitored.

[0015] Preferably, the tubular housing is at least partially locatable sub-sea.

[0016] Another aspect of the invention relates to a complex pipe comprising a tubular housing, at least one inner conduit and an apparatus for monitoring a physical parameter of at least one inner conduit consisting of strain, temperature, pressure or vibration of the inner conduit, the apparatus comprising a sensor carrier positioned in the space between the inner conduit and the tubular housing, the sensor carrier having at least one sensor means suitable for measuring the physical parameter, and the sensor carrier being proximate the inner conduit to be monitored.

[0017] The complex pipe is preferably a flexible pipe.

[0018] The complex pipe may also comprise a plurality of inner conduits of substantially the same dimensions, a set of spacers being positioned within the tubular housing for preventing the inner conduits from coming into contact with one another and the sensor carrier being attached to the spacers. The spacers allow for positioning of the sensor carriers comprising the sensors in close proximity to the inner conduits.

[0019] In one embodiment a complex pipe comprises four inner conduits of substantially the same dimensions, a set of spacers fixedly positioned within the tubular housing for preventing the inner conduits from coming

into contact with one another, and wherein said sensor carrier is fixedly attached to the spacers.

[0020] The sensor carrier may preferably be made of a polymeric material, and is shaped to match the outside surface of the inner conduit to be monitored for a tight fit and to allow effective transfer of properties to be measured from the inner conduit. The sensor carrier preferably comprises a plurality of optical fibre sensors. The sensor carrier may be in the shape of a rod, a strip, a plate, a cylinder, or a mat, or a shape having a rectangular cross section with at least one concave side shaped to fittingly match the outside shape of an inside conduit.

Brief Description of Figures in the Drawings

[0021] Embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-sectional view of a first embodiment of apparatus for monitoring the integrity of a inner conduit housed within a protective tubular housing according to the invention; Figure 2 shows a schematic cross-sectional view of a second embodiment of apparatus for monitoring the integrity of a plurality of inner conduits housed within a protective tubular housing, according to the invention; Figure 3 shows a schematic cross-sectional view of a third embodiment of apparatus for monitoring the integrity of a plurality of inner conduits housed within a protective tubular housing, according to the invention; Figure 4 shows a schematic cross-sectional view of a fourth embodiment of apparatus for monitoring the integrity of inner conduits housed within a protective tubular housing, according to the invention; and Figure 5 shows a schematic cross-sectional view of a fifth embodiment of apparatus for monitoring the integrity of inner conduits housed within a protective tubular housing, according to the invention.

Mode(s) for Carrying Out the Invention

[0022] Various preferred embodiments of the invention are shown in Figures 1 to 5, in which cross-sectional views of apparatus comprising a complex pipe 10 for monitoring either the integrity of or content within an inner conduit

housed within a tubular housing or outer pipe for use in the oil or gas industry are shown.

[0023] In Figure 1 complex pipe 10 is shown to include an outer protective pipe or tubular outer housing 12 and is one of a number of types of complex pipes such as a high pressure complex pipe for transporting fluids under pressure and electrical cabling in oil and gas industrial operations and production facilities. An inner conduit 14 is shown located inside housing 12. In this particular embodiment the apparatus is conforming to the outer shape of the inner conduit 14 to be monitored. Inner conduit 14 may be used as a conduit to convey fluids and/or a conduit to house electric cabling. Complex pipe 10 may, for example, be an umbilical for transporting electrical cables or a riser for transporting fluid or housing tubing in sub-sea well applications. These umbilicals or risers may be used to connect wells or facilities located on the seafloor to facilities which are located on floating vessels or on platforms above the sea surface.

[0024] For instance complex pipe 10 in the form of a flexible or rigid pipe may extend from a drilling platform or floating vessel down to the seafloor. Various fluids are transferred through said pipe from the wellhead to the surface and vice versa.

[0025] In another example complex pipe 10 may be an umbilical that extends from a drilling platform or floating vessel down to the seafloor. An umbilical is typically a complex flexible pipe that houses many inner conduits. The top of the umbilical may be attached to the floating vessel, while the bottom of the umbilical may be secured at the seafloor.

[0026] As shown in Figures 1 and 2, a sensor carrier 16 having a partly cylindrical shape is located in the space 18 between inner conduit 14 and outer housing 12. It can be seen that sensor carrier 16 is associated with inner conduit 14 in close proximity thereto, that is, it is on or spaced apart from inner conduit 14.

[0027] Sensor carrier apparatus 16 includes a sensor assembly (not shown) comprising an assembly of optical fibre strain sensors. These optical fibre sensors may include optical fibre Bragg gratings sensors, also known as "FBG", spatially deployed to respond to predetermined strains and other

desired measurements such as, but not limited to Hoop strain, temperature, bending stresses, vibration and other related measurement.

[0028] Preferred sensor carriers for the embodiments shown in Figures 1 and 2 may be apparatus as disclosed in EP1635034 A1 by the title "Structural member bend radius and shape sensor and measurement apparatus' filed on 27 August 2004 which is incorporated herein by reference for all purposes. The sensor carrier apparatus as disclosed in said EP1635034A1 patent application may include optical fibre Bragg grating (FBG) strain sensors each having a resonant wavelength of 1550 nm and a spectral line width of 0.07nm. The sensor carrier apparatus disclosed is in the form of a carrier rod, having a circular cross-section which is of epoxy resin and has a diameter of about 5mm. The strain FBG sensors are provided in a set of optical fibres which are embedded within the carrier rod. In the example shown there are three optical fibres. The optical fibres are embedded close to the surface of the carrier rod and are substantially equally spaced from one another around the carrier rod. In this way the FBG strain sensors are mechanically coupled to the carrier rod at three measurement locations located generally within a single cross-sectional plane of the carrier rod and are equally spaced around the surface of the carrier rod.

[0029] Other types of sensors may be incorporated in sensor carrier apparatus 16, but optical fibre sensors are preferred because of their versatility, reliability and size.

[0030] The optical fibre sensors included in apparatus 16 are placed so that they are able to monitor various characteristics of inner conduit 14 or its contents relating to, for example, the thermal behaviour, geometry, turbulence fluid flows generating vibration, bending and other related mechanical characteristics. These various characteristics may be monitored with the help of sensors included in a sensor carrier 16 which may make various measurements relating to at least one physical parameter such as, for example, temperature, mechanical strain, pressure and vibration of the inner conduit 14.

[0031] The monitoring of inner conduits 14 by the sensors on sensor carrier apparatus 16 may be used to assist in preventing structural failure due to, for example, fatigue, corrosion, erosion, or blockage caused by the deposition of parts of the fluid flow components in these conduits 14, such deposits as wax, hydrates, scales, asphaltines and the like.

[0032] In the second embodiment of the invention as shown in Figure 2, protective tubular housing 10 is shown to include four inner conduits 14 located inside the outer housing 12, each of the inner conduits has a partly cylindrical shaped sensor carrier 16 associated with it and in close proximity to the inner conduits. There are four inner conduits 14 shown by way of example in Figure 2, but the intention of this graphical representation is not to limit the invention to monitor four inner conduits 14. Figure 2 represents an embodiment of the invention where more than one inner conduit is to be monitored. Each sensor carrier apparatus 16 is shaped to fit in the space between an inner conduit 14 and the outer housing 12. Each sensor carrier apparatus 16 is also in close proximity to the inner conduits 14 so that the sensors are close enough in order to effectively obtain measurements relating to the integrity of an inner conduit 14 with which it is in close proximity.

[0033] The four conduits 14 may be, for example, a bundle of conduits in a sub- sea umbilical cable which are used for one of a number of different functions such as, for example, chemical injection, hydraulic control, communication, power cables, and so on.

[0034] The sensor carriers 16 as shown in the embodiments illustrated in Figures 1 and 2 may be deployed in place by a variety of methods including extruding or embedding the sensor carrier into the umbilical cable at the time of manufacturing.

[0035] Another preferred method includes embedding the sensor carriers in place during manufacturing of the complex pipe or securely attaching the sensor carriers using a variety of well known methods to the outer surface of the inner conduits to be monitored. By way of example an "engineered adhesive" such as a flexible adhesive epoxy may be used to securely attach the sensor carrier to the inner conduits at the time of manufacturing

of the complex pipe and before the inner conduits are deployed into the protecting tubular housing.

[0036] In the third embodiment of the invention as shown in Figure 3, complex pipe 10 is shown also to include more than one inner conduit 14. In this example four conduits 14 are located inside outer housing 12, but in this embodiment the sensor carrier 16 is comprised of a complex structure which is associated and in communication with all four conduits 14. Sensor carrier 16 is in the form of two plates deployed perpendicularly from one another at half their width. In Figure 3 a set of spacers 20 are shown, each spacer 20 extending from one side of the inside wall of housing 12 to the opposing side of the inside wall. The spacers 20 are used to keep each of the four conduits 14 separated from each other. The sensor carrier 16 and the sensors in the form of the two plates can be attached to the spacers 20 or they can be incorporated into the spacers 20 themselves.

[0037] The shape of the sensor carrier apparatus 16 can be modified to accommodate the space available between the outer housing 12 and the inner conduits 14, and they may be in a variety of forms such as, for example, rods, strips, plates, cylinders, a shape conforming to the void space between the inner conduits and so on. The sensor carrier apparatus is generally preferred to be made out of a compliant material although the present invention may be carried out with a sensor carrier made out of a number of other materials. A compliant material is such a material that is designed to allow the transfer of stress, and examples are anisotropic materials or composite materials among others, these materials have the tendency to conform to the surface to which it is applied. A Fiber-Reinforced Plastic "FRP", also known as Fiber- Reinforced Polymer, is a composite material comprising a polymer matrix reinforced with fibres. The fibers are usually fiberglass, carbon, or aramid, while the polymer is usually an epoxy, vinylester or polyester thermosetting plastic. FRPs are commonly used in the aerospace, automotive, marine, and construction industries. The preferred type of FRP material is an epoxy reinforced fiberglass. The sensor carrier may be

securely attached to the inner conduit by means of a flexible epoxy adhesive or may be, by way of example, but not to limit this disclosure, strapped or clamped to the inner conduits. The sensor carrier may also be placed in a void left for that purpose in the space between the inner conduits.

[0038] As previously described, there are different types of sensors which may be incorporated in sensor carrier apparatus 16. The optical fibre sensors are generally preferred because of their versatility, size and reliability. These optical fibre sensors are distributed at a number of spaced locations along the length of each sensor carrier apparatus 16 or attached to the spacers 20 wherein the carrier apparatus 16 is incorporated into the spacers 20.

[0039] The fourth embodiment of the invention is shown in Figure 4. Complex pipe 10 in this example of the invention is shown to include more than one inner conduit 14. In this particular example of the invention four inner conduits 14 located inside outer housing 12 are separated from each other by a spacer 22 in the form of two plates deployed perpendicularly from one another at half their width. There is further a sensor rod located at the junction between the two spacer plates and one of these sensor rods is also located on each of the four ends of the two spacer plates. Each sensor rod has the required sensors embedded into it to measure the desired properties of the inner conduits. In this example the four inner conduits 14 are similar in shape and there are also a further five conduits 24 of a different shape also located inside outer housing 12. In this embodiment the sensor carrier 16 comprises of a structure which is associated with and in close proximity to conduits 14 and/or conduits 24. In Figure 4 a set of inter-connecting spacers 22 are shown to be located at substantially right angles from one another and are distributed between the various conduits 14 and 24 so as to keep them all safely separate from one another and prevent them from coming into contact with one another. The sensor carrier 16 may either be securely attached to spacers 22 or embedded into spacers 22. As in the previously described embodiments of the invention, there are different types of sensors which may be incorporated in sensor carrier apparatus 16 in the fourth embodiment, but

optical fibre sensors are preferred because of their versatility, size and reliability. These optical fibres are distributed along and in the perimeter of the sensor rods.

[0040] In the fifth embodiment of the invention as shown in Figure 5, the complex pipe 10 is also shown to include by way of example, four conduits 14 located inside outer housing 12. In this embodiment the sensor carrier 16 comprises a complex structure which is associated with and in close proximity to all four conduits 14.

[0041] In Figure 5, sensor carrier 16 is shown to have a generally rectangular shape with concave sides 28 designed to match the outside diameters of the inner conduits 14. It is foreseen that structure 26 may comprise a series of sections distributed throughout the length of outer housing 12, or it may be a single longitudinal structure which extends along the length of outer housing 12.

[0042] As in the previously described embodiments of the invention, there are different types of sensors which may be incorporated in sensor carrier 16 in the fifth embodiment, but optical fibre sensors are preferred because of their versatility, size and reliability. These optical fibres may be distributed on or along the sensor carrier 16, or each section thereof, as the case may be, or may even be embedded therein.