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FIBER OPTIC PUMPING WITH CAPSTAN CAPABILITY FOR SAFE PUMPING IN HIGH PRESSURE OR DEEP WELLS

IP.com Disclosure Number: IPCOM000085277D
Publication Date: 2005-Mar-02
Document File: 3 page(s) / 138K

Publishing Venue

The IP.com Prior Art Database

Abstract

Fiber optic "cable" can be pumped into small tubing such as control line that is either previously installed in a well or in preparation for installation into a well. This cable can be used for several things including DTS (Distributed Temperature Sensing). Often the pumping takes place at the well due to several reasons such as 1) failure and removal of previous fiber optic cable, 2) installation at a post well completion date due to delaying cost of fiber and monitoring, 3) completion installation of control line uses a control line hydraulic connect.

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FIBER OPTIC PUMPING WITH CAPSTAN CAPABILITY FOR SAFE PUMPING IN HIGH PRESSURE OR DEEP WELLS

Fiber optic "cable" can be pumped into small tubing such as control line that is either previously installed in a well or in preparation for installation into a well. This cable can be used for several things including DTS (Distributed Temperature Sensing). Often the pumping takes place at the well due to several reasons such as 1) failure and removal of previous fiber optic cable, 2) installation at a post well completion date due to delaying cost of fiber and monitoring, 3) completion installation of control line uses a control line hydraulic connect.

To reduce costs, some control line installations are not completed with the conventional U-turn with both control line ends at the surface. Instead, the control line is terminated in the well, often with a check valve to prevent well inflow to the control line. This type of installation requires high pumping pressures as the well hydrostatic must be overcome to start the pumping process.

One of the current methods to place Fiber optic "cable" in a well control line is to pump "flow" it in with a fluid (often water). To control the speed and direction of the fiber it is desirable to use a capstan. The capstan is an electronically controlled shaft that has one wrap of fiber around its perimeter. The pump pressure is inside the capstan housing and pulls the fiber tight onto the shaft. The use of the capstan provides good control of the fiber as well as an accurate measure of the length of the fiber that has been pumped. If no capstan is used, the fiber spool must be restricted by use of a brake that holds tension on the fiber. This can harm the fiber as the fiber on the outside of the spool must cut into inner layers of the fiber to hold the back tension. This damages the fiber.

The capstan has the disadvantage in that the capstan housing must contain the high pressures necessary to pump in long or deep control lines. The housing also has a rotary seal that must not leak as the shaft rotates. Due to the pressure, the housing must be kept reasonably small which dictates the capstan shaft must also be small. This small shaft diameter can damage the fiber as it is considerably smaller than that of the fiber spool. If the fiber is bent around too small of a shaft it will be stressed to the point of breaking. Typically the spool minimum diameter is 6 inches or more and the capstan shaft is around 2 inches.

The current capstan designs use a small tube diameter lubricator on one end of the capstan housing to minimize the fluid loss to the atmospheric pressure. The lubricator internal diameter may be just a few thousands (.001) of an inch larger than the fiber. This lubricator can be made up of one or more tubes of equal or stepped reducing diameters.

The other end of the capstan is commonly attached to a long section of heavy wall thickness 1/4 inch control line. This section is commonly referred to a...