Patent Application
20080245533
The oil and gas recovery industry in recent years has increasingly discovered uses for optical fiber in signal conductance and sensory applications for the downhole environment. In view of the harshness of that environment, the delicate optical fibers must be protected yet disposed optimally to sense desired parameters to conduct signals to desired end devices.
In a sensory capacity, the fiber must be exposed to the parameter being measured to be able to register that parameter, strain as a parameter presents a particular difficulty because of the need for the fiber to be protected but also to be exposed to the strain in the environment being sensed. Solutions to the foregoing are well received by and beneficial to the art.
A fiber support arrangement for a downhole tool includes a tubular; at least one end ring positioning the tubular spaced radially from a downhole tool and lacking contact therewith; and a fiber supported at the tubular.
A method for supporting a fiber at a downhole tool includes disposing an outer support at a downhole tool, the support being radially outwardly positioned of the tool; supporting the support to a string axially spaced from each end of the downhole tool such that the downhole tool is lacking contact with the support; and mounting a fiber at the support such that the fiber is lacking contact with the downhole tool.
Referring now to the drawings wherein like elements are numbered alike in the several Figures:
Referring to
The fiber support arrangement 10 comprises at least one end ring and as illustrated two end rings 30 and 32 each having a fiber pass through 34 and 36, respectively and which may be sized to allow pass through of the fiber alone or the fiber inside of a conduit. End rings 30 and 32 have a radial dimension y sufficient to ensure a clearance between the sand screen assembly 12 (or other downhole tool) and a fully assembled fiber support arrangement 10 such that contact between the fiber support arrangement and the sand screen assembly (or other downhole tool) does not occur. The end rings may be fully annular structures or may be segmented as desired.
Extending from one end ring 30 to the other end ring 32 is a perforated tubular 38, which may be a metal tubular), the perforations being identified with the numeral 40. At an inside dimension surface 42 of the tubular 38 is a fiber conduit 44, which in one embodiment is strain transmissively disposed thereat. It is to be understood that in other embodiments, the fiber conduit is disposed to facilitate the fiber therein measuring or sensing temperature, seismic, pressure, chemical composition, etc. The conduit 44 may be a metal tube such as a quarter inch or eighth inch or sixteenth inch stainless steel tubular, for example. In one embodiment, the conduit 44 is welded by, for example, an induction welding technique to the inside surface 42 of tubular 38. In another embodiment, the fiber conduit is mechanically or adhesively attached to surface 42 (it is to be understood that adhesive processes are intended to include soldering and brazing processes). Broadly stated, any means of attachment of the fiber conduit 44 to the tubular 38 that allows for, in one embodiment, transmission of strain in the tubular 38 to the fiber conduit 44 without significant loss of magnitude or at least a reliably predictable loss in magnitude or in other embodiments facilitating or at least not hindering the measurement or sensing of such properties as seismic, temperature, pressure, chemical composition, etc. is sufficient for purposes of the invention disclosed herein. It is to be understood that combinations of sensitivities are also contemplated wherein one or more of the exemplary properties are sensed or combinations including at least one of the exemplary properties are sensed.
In order to ensure optimal function of a fiber 46 installed in the fiber conduit 44, consideration must be given to the means of attachment of the fiber conduit to the tubular 38. This is particularly true if a welding process or other heat intensive process is to be used for the affixation of the fiber conduit 44 to the tubular 38. Depending upon the heat to be applied and the resistance to heat damage a particular type of optical fiber 46 exhibits, it is possible to place the fiber in the conduit 44 before welding (or other heat process) or alternatively creates a requirement to place the fiber 46 in the conduit 44 after welding (or other heat process).
Regardless of process of attachment, the fiber 46 (either before or after conduit attachment) is installed in the conduit 44, the conduit or the fiber being adapted to allow the fiber to sense the target property. In one embodiment the fiber is embedded in a strain transmissive potting substance such as for example, epoxy inside the conduit 44. Such substance ensures that strain in the conduit 44, transmitted thereto by the tubular 38, is in turn transmitted to the fiber 46 where it will effect a frequency shift in the transmission wavelength of the fiber thus indicating at a remote location a strain and its magnitude.
In one embodiment of the support, a strip of perforated material is helically wound about an axis and welded at sides thereof to create the tubular form. This method is known to the art but pointed out here for the purpose of noting that the conduit 44 maybe strain transmissively or otherwise disposed at the strip before the strip is helically wound, as the strip is helically wound or after the strip is helically wound, as desired. In the event the conduit is to be placed after the strip is wound i.e. after tubular 38 is formed, then it is desirable to helically wind the conduit 44 first and install it in the tubular 38 as a helical coil prior to strain transmissive disposition thereof.
The completed tubular 38 and conduit 44 are disposed between the end rings 30 and 32 and secured there permanently. The conduit 44, as shown extends beyond the end rings 30 and 32 through pass throughs 34 and 36, respectively, and then to connectors (not shown).
As is illustrated, the conduit 44 is spaced from the sand screen assembly shroud 20 so as to make no contact therewith when installed. As is illustrated, the fiber support arrangement is attached to the base pipe 14 axially outside of the attachment points of the screen filter media 18 and shroud 20 and may be at the ends of such base pipe 14, if desired. As one of skill in the art will anticipate, one means of attachment of the end rings 30 and 32 to the base pipe 14 is by welding as shown.
While the embodiment illustrated in
In another embodiment, referring to
In other respects, the
Finally, and referring to
While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
