Patent Application
20130034324
Optical fibers find use in a variety of applications. For example, in the drilling and completion industry, optical fibers are utilized to measure various conditions in a downhole environment as well parameters of downhole components. Exemplary optical fiber sensors include temperature sensors and strain sensors, which can be used to monitor deformation in downhole components. For applications such as strain sensing, it is important that optical fibers used in sensing be firmly attached or otherwise fixed in place relative to the components for which sensing is utilized. In addition, mechanisms for affixing optical fibers to substrates must also be able to withstand elevated temperatures and other conditions encountered downhole.
An optical fiber sensing apparatus includes: a substrate configured to deform in response to an environmental parameter; an optical fiber sensor including a core having at least one measurement location disposed therein and a protective coating surrounding the optical fiber sensor, the protective coating made from a polyimide material; and an adhesive configured to adhere the optical fiber sensor to the substrate, the adhesive made from the polyimide material.
A method of manufacturing an optical fiber sensing apparatus includes: disposing an optical fiber sensor on a surface of a substrate configured to deform in response to an environmental parameter, the optical fiber sensor including a core having at least one measurement location disposed therein and a protective coating surrounding the optical fiber sensor, the protective coating made from a polyimide material; and applying the polyimide material and bonding the polyimide material to the substrate.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Fiber optic sensors configured for measuring parameters such as strain, stress and deformation, as well as other parameters such as temperatures and pressure, are provided herein. In one embodiment, such sensors are incorporated in a downhole assembly for measuring parameters of components such as downhole tools, borehole strings and bottom hole assemblies (BHAs). An exemplary optical fiber sensing assembly includes an optical fiber coated with a protective layer made of a polyimide material, which is adhered to a substrate via the polyimide material. In one embodiment, the substrate is a metallic substrate for which parameters such as strain and deformation are to be measured. The assembly includes a deformable member such as a tube that is deformable in response to pressure and/or other forces. Such forces include, for example, axial forces and internal pressures exerted on the deformable member, e.g., in a downhole environment.
Referring to
The optical fiber sensor 12 is adhered to the substrate 14 via a polyimide material, which may include the polyimide coating 18 or an additional layer of polyimide that is fused to the polyimide coating 18 and adhered to the substrate 14. Exemplary polyimides include polyimides having a high glass transition temperature (Tg), such as a Tg greater than about 250 degrees C. In one embodiment, the polyimide materials have a Tg that is greater than temperatures found in a downhole environment. Examples of such polyimide materials include thermoplastic polyimides (TPI) such as PEEK and commercially available PI-2611 and PI-2525 from HD Microsystems, and composite polyimide materials such as composite polyimide/acrylate materials.
The optical fiber sensor 12 includes a core for transmission of optical signals, such as a silica core, and a cladding such as a doped silica cladding. In one embodiment, the polyimide coating 18 is adhered directly to the exterior surface of the cladding. Thus, in this embodiment, the optical fiber sensor 12 consists of only three layers, i.e., the core, the cladding and a polyimide material that acts as both a protective coating and an adhesive to secure the optical fiber sensor 12 in a fixed position relative to the substrate 14.
Deformation of the substrate, such as bending, expansion or contraction, causes effects such as micro-bends in the optical fiber 16, which in turn cause a change (e.g., a wavelength shift) in the signal returned by the measurement units. This signal change can be used to determine the deformation and estimate force and/or pressure based on the deformation. The optical fiber sensor 12 may be in communication with a user, control unit or other processor or storage device via suitable communication mechanisms.
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The embodiment shown in
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The components and configurations of the cables are not limited to the embodiments described herein. For example, the cables 20 may include other components such as additional electrical conductors for supplying power or communication. Furthermore, the type or configuration of the substrates is not limited.
Referring to
The borehole string 42 includes one or more pipe sections 48 or coiled tubing that extend downward into the borehole 44. In one example, the system 40 is a drilling system and includes a drill bit assembly. The system 40 may also include a bottomhole assembly (BHA). The system 40 and/or the borehole string 42 include any number of downhole tools 50 for various processes including drilling, hydrocarbon production, and formation evaluation (FE) for measuring one or more physical quantities in or around a borehole.
In one embodiment, the system 40, the tools 50, pipe sections 48, the borehole string 42 and/or the BHA include at least one pressure, strain and/or force sensor, such as the optical fiber sensor 12 and/or the strain sensing cable 20. The pressure and/or force sensor is configured to measure various forces on system components, in the borehole 44 and/or in the surrounding formation. Exemplary forces include pressure from drilling, production and/or borehole fluids, pressure from formation materials, and axial and/or radial force on components of the borehole string 42, tool 50 or other downhole components of the system 40.
In one embodiment, the tool 50 and/or optical fiber sensor 12 are equipped with transmission equipment to communicate ultimately to a surface processing unit 52. Such transmission equipment may take any desired form, and different transmission media and connections may be used. The surface processing unit 52 and/or other components of the system 40 include devices as necessary to provide for storing and/or processing data collected from the optical fiber sensor 12 and other components of the system 40. Exemplary devices include, without limitation, at least one processor, storage, memory, input devices, output devices and the like.
In the first stage 61, a polyimide coated optical fiber sensor such as the sensor 12 is disposed on a surface of a substrate that is configured to deform in response to an environmental parameter. Examples of the substrate include the substrate 14, and cable components such as metal tubes 22, central member 24, wires 30 and cable core 32.
In the second stage 62, polyimide material making up the coating 18 and/or additional polyimide material is bonded to the substrate 14. In one embodiment, a liquid polyimide is applied to the optical fiber sensor 12 and the substrate is allowed to harden and cure (at room temperature or at another selected temperature) to form a bond between the optical fiber sensor and the substrate. In one embodiment, polyimide material making up the coating 18 and/or additional polyimide material is heated to beyond the glass transition temperature of the polyimide material. In one embodiment, only the polyimide coating 18 is used and heated. In another embodiment, an additional layer or film is disposed on the fiber sensor 12, and both the coating 18 and the additional layer of polyimide is heated. In yet another embodiment, the coating 18 is not directly heated, but rather liquid polyimide is applied to the fiber 12 and the substrate.
In the third stage 63, the polyimide material is allowed to cool or may be actively cooled to a temperature below the glass transition point. For example, the polyimide material is allowed to cool to room temperature. The cooling allows the polyimide to harden and bond to the substrate 14.
In the fourth stage 64, the cooled polyimide is optionally cured for a period of time to improve the bond between the polyimide and the substrate. For example, the polyimide is heated to an intermediate temperature such as 150 degrees C. for a selected period of time, e.g., at least about 16 hours.
There is provided a method of measuring an environmental or component parameter in a downhole system using the fiber optic sensing assembly 10. In a first stage, the optical fiber sensor 12 and/or cable 20 is deployed in the borehole 44 via the borehole string 42 and/or via other components, such as a drilling assembly or measurement sub. In a second stage, one or more signals are transmitted into the optical fiber sensor 12. For example, interrogation signals are transmitted into the optical fiber sensor 12 from the surface processing unit 52, and measurement locations such as Bragg gratings or Rayleigh scattering sections of the optical fiber sensor 12 reflect signals indicative of parameters such as strain and deformation.
The apparatuses and methods described herein provide various advantages over existing methods and devices. The sensing assemblies provide for effective strain sensing at high temperatures, as well as providing a substantially creep-free bond at high temperatures. Creep generally refers to degradation or other changes in a fiber sensor coating (e.g., adhesive deterioration) that develop over time and affect the detected wavelength shift in an optical fiber sensor. Another advantage is provided by the relatively few number of types of materials (e.g., a single polyimide material as protective coating and adhesive), which minimizes the number of materials used in the sensing apparatus and hence negates many material compatibility challenges that could arise.
In connection with the teachings herein, various analyses and/or analytical components may be used, including digital and/or analog systems. The apparatus may have components such as a processor, storage media, memory, input, output, communications link (wired, wireless, pulsed mud, optical or other), user interfaces, software programs, signal processors (digital or analog) and other such components (such as resistors, capacitors, inductors and others) to provide for operation and analyses of the apparatus and methods disclosed herein in any of several manners well-appreciated in the art. It is considered that these teachings may be, but need not be, implemented in conjunction with a set of computer executable instructions stored on a computer readable medium, including memory (ROMs, RAMs), optical (CD-ROMs), or magnetic (disks, hard drives), or any other type that when executed causes a computer to implement the method of the present invention. These instructions may provide for equipment operation, control, data collection and analysis and other functions deemed relevant by a system designer, owner, user or other such personnel, in addition to the functions described in this disclosure.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention.
