Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-09-20
2001-07-24
Ben, Loha (Department: 2873)
Optical waveguides
With optical coupler
Particular coupling structure
C385S024000, C385S134000, C065S406000
Reexamination Certificate
active
06266465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the oil field industry. More particularly, the invention relates to fiber optics, conduits and junctions for use in the downhole environment.
2. Prior Art
In recent years fiber optic technology has been integrated into many different fields of endeavor particularly with respect to communicating information and power. Gains can be had on both fronts by employing optic fibers instead of wire conductors in many situations.
As one skilled in the use of optic fibers will recognize, the fibers are delicate and require protection to work reliably. For this reason it has been very difficult to employ optic fibers in the typically harsh downhole oil well environment. Temperature, pressure, vibration, chemicals, etc. are all common conditions downhole and are all deleterious to virtually all materials but particularly so with respect to delicate optic fibers.
Optic fibers have nevertheless been successfully employed in the downhole environment when properly clad and when run through empty hydraulic control conduit systems. This use has been successful for straight runs. The conduit protects the fiber from all of the aforementioned conditions and reliable fiber optic control has been achieved. The limited (to straight runs) downhole optic fiber usage has been very beneficial to the industry but remains limited, in the knowledge of the industry, since until this invention there has been no way to successfully split fiber off a main run to go in another direction. Running fiber in a primary wellbore and then splitting off some of it for a lateral has never been successfully attempted due to breakage of the fibers and vibration coupling. Existing hydraulic conduit “T” fittings when employed to split off fiber cause the fiber to break from contact with corners and tight bend radiuses and because they suffer vibration damage from contacting the walls of the conduit where vibration from the environment is strongest with respect to the space defined by the conduit.
SUMMARY OF THE INVENTION
The above-identified drawbacks of the prior art are overcome or alleviated by the angled optic fiber conduit unions and junctions of the invention.
Appropriately angled unions and junctions enable the heretofore contraindicated practice of splitting optic fibers off from the main conduit in the downhole environment to be directed to distinct places such as lateral boreholes or to other tools. Creating unions and junctions that maintain a minimum bend radius and to avoid significant corner contact pressure makes optic fiber distribution feasible and reliable in the downhole environment.
Although it is possible to split off optic fibers with conventional hydraulic conduit unions and junctions the fiber bend radius is relatively small, corner contact results and the fiber is pressed against one of the walls of the hydraulic conduit causing greater vibration coupling into the fiber. While the optic fibers can be made to work in this condition in the factory, the downhole environment in which these tools are employed is an environment of high pressure, high temperature and high vibration. These conditions in combination with the relatively small bend radius and the fiber being pressed against the conduit sidewall, thus coupling the fiber to vibration in the conduit, cause failure.
By carefully matching a bend in the union or junction to avoid too small a bend radius and consequently avoiding fiber pressure against the wall of the conduit, failure of the fiber occurs less often while allowing the use of optic fibers at all locations in a well even if the well is a multilateral well. For purposes of clarity, the bias contemplated herein is that supplied by the fiber itself in the bent condition.
The invention greatly expands the capability of manufacturers to build downhole systems with fiber optic communications.
In addition to bend radius the unions of the invention as well as the entirety of the fiber optic conduit is pressure sealed. This may be accomplished by any known sealing method that prevents ingress or egress of fluid. By sealing the conduit a protective fluid for the fiber optic could be employed within the conduit or it can contain simply air or even a vacuum and still prevent wellbore fluids from gaining entry thereto.
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Baker Huges Incorporated
Ben Loha
Cantor & Colburn LLP
LandOfFree
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