This invention relates to a tape assembly comprising a fiber optic cable. In particular to a tape for attaching a fiber optic cable to the surface of a tubular in a well.
There is significant interest in attaching sensors to the outside of casing or tubulars in subterranean wells to provide information on the changes in the downhole environment either continuously or periodically, particularly in oil and gas well bores. However one of the challenges is the transmission of information between the sensors and the surface.
Previously, cables have been attached to the outside of casing with clamps and other mechanical devices, to transmit information from the sensors to the surface, but the size of the cables used and the mechanical fixation methods has limited the applicability of the installation.
Generally it has not been considered appropriate to attach elongated objects of a significant diameter to a well casing in the cement path because there is a risk that there will be insufficient penetration of cement in the interstices between the casing and object and between the object and the wellbore wall, which would therefore result in a leak path from formation to the surface. In turn, such a path is a risk to the integrity of the isolation from formation to surface and thus unacceptable on environmental and safety grounds.
Another challenge is that wellbore environments may have extreme conditions in terms of e.g. pressure, temperature, pH or chemical environment. This has limited the possibility to attach sensors to the outer surface of a pipe without using clamps, as the attaching mechanism must first resist such extreme conditions and then have enough flexibility to follow the axial and circumferential geometry of the pipe.
The object of the invention is to overcome the limitations of the previous methods using a tape for attaching optic fibers to the outside surface of tubulars.
This invention provides an optical fiber tape assembly for attaching an optical fiber to the surface of a pipe for use in wellbore environments, particularly in subterranean wells comprising;
a tape having magnetic attachment means to enable attachment of the tape to the pipe; and
at least one optical fiber that runs substantially parallel to the longitudinal axis of the tape;
wherein the optical fiber is integral with the tape.
Preferably the longitudinal edges of the tape are tapered such that the tape has a trapezoid cross section.
In an embodiment, the attachment means of the assembly may be an adhesive layer on the tape.
The assembly can further comprise protective elements. The protection elements may be wires, the wires running parallel to the optical fiber, tubes with the optical fiber located inside the tube, and/or a coating layer for covering the optical fiber.
A second embodiment of the invention comprises a system for a wellbore, preferably subterranean well, comprising:
at least one section of pipe; and
a optical fiber tape assembly as described above; wherein the tape assembly is attached to the outer surface of the section of pipe.
The system can comprise at least two pipe sections and a wedge; wherein the wedge is located at a joint between two pipe sections and the tape assembly is attached over the wedge.
Another embodiment of the invention comprises a method for attaching a optical fiber to the surface of a pipe comprising; deploying a tape as described above from a storage device; and attaching the tape to the surface of the pipe as the pipe is deployed into a well.
The method can comprise attaching the tape longitudinally along the pipe as the pipe is being run into a well.
The method can comprise attaching protective elements to the outside surface of the tape as it is deployed from the storage device.
The method can further comprise attaching wedges at joints in the pipe and placing the tape over the wedges.
Preferably the method comprises using an apparatus as described above.
The apparatus according to the invention is applicable for attaching optical fibers to the surface of tubulars, in particular to the outer surface of a casing or tubular in a subterranean well. The optical fibers can be used for sensing and/or to transmit information up and/or down the wellbore. As shown in
In some situation numerous fibers can be integrated into the tape so that should one fiber break and therefore lose transmission capabilities other fibers are still present in the tape that can be used for continuing the monitoring or transmitting process. As shown in
Alternatively some measurements that can be made with the optical fibers in the tape may require the use of more than one fiber, or fibers of different types. For example where the cables are for making distributed temperature measurements, the preferred fiber type is one of multimode designs, in this situation for most applications it is preferred to employ a fiber loop to allow cancellation of losses. In other types of measurements such as those based on interferometry, a fiber supporting a single transverse mode, possibly having two independent polarization states, is preferred. In other measurements, high birefringence fibers are preferred in order to deliver light in a known state of polarization to a sensor. Other types of fibers that can be used include pressure sensitive fibers, such as a side-hole fiber the birefringence of which is a function of isostatic pressure.
As shown in
With reference to
The tape may comprise mechanical and/or chemical protection mechanisms. As shown in
In order to attach the fiber optic cable to the surface of the pipe, a tape having the optical fiber integrated into the body of the tape can be attached to the pipe as the pipe is run into the well. The sticking of the tape to the surface of the pipe will also secure the cable to the surface of the pipe. In most cases the tape will be attached longitudinally along the length of the pipe in a continuous manner, however in some situations it may be required to wrap the tape around the pipe, in order to provide circumferential coverage of the fiber about the pipe.
The tape can be applied to the pipe by applying a magnetic or adhesive layer to the tape. The tape 3 can be stored on a roll 8, as shown in
Where the tape requires protective wires these wires can be pre formed into the tape or attached to the tape as it is deployed in order to reduce the size of the reel that that tape is stored on. As shown in
The diameter of the pipe in the well can change along its length, for example at the junctions of a casing collar on the pipe. As the tape is attached to the surface these changes in diameter can cause unwanted stress to occur to the tape and optic fiber. As shown in
An alternative way of preventing damage when the tape passes over changes in the tubular dimensions is shown in
The cable assembly according to the invention can be used to support communication with sensors placed in the formation or at discrete positions along the well trajectory. It may also be a means of deploying distributed sensors along at least part of the well trajectory and provide measurements of the formation or information about the flow within the tubing. For example, in conjunction with permeable cement, the invention can be used to provide information on the pressure in the formation.
A further application is for at least one of the fibers in the tape to be used as an acoustic sensor, for example by means of coherent optical time-domain reflectometry techniques, and can be used in a number of seismic applications, such as permanent vertical seismic profiling or passive micro seismic detection, where small seismic events resulting from movement in the formation are detected and triangulated to provide information for example, on drainage of fluids or the position and status of geological faults.
The sensors can also be used for analysing the acoustic signal resulting from flow and thus indication of flow rates and/or presence of more than one phase, including the detection of solids. Very localised noise detection might also allow the presence of leaks behind casing to be detected and thus provide improved well integrity.
Various changes within the scope of the invention can also be made.
Number | Date | Country | Kind |
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08165852 | Oct 2008 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2009/006746 | 9/11/2009 | WO | 00 | 6/22/2011 |
Publishing Document | Publishing Date | Country | Kind |
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WO2010/037478 | 4/8/2010 | WO | A |
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