Fluid handling – Processes – Cleaning – repairing – or assembling
Reexamination Certificate
1997-11-24
2001-08-21
Walton, George L. (Department: 3753)
Fluid handling
Processes
Cleaning, repairing, or assembling
C137S315020, C137S322000, C137S614000, C166S087100, C166S091100, C166S097100, C166S242600, C166S330000, C251S148000
Reexamination Certificate
active
06276386
ABSTRACT:
BACKGROUND OF THE INVENTION
In one aspect, the present invention relates to a charging device suitable for use with a tubing system. In another aspect, the present invention relates to a method for precharging a tubing system to facilitate further assembly of a unit which contains the tubing system.
One type of subsea wellhead used in the oil and gas industry is the horizontal, or side valve tree (SVT). The SVT is formed from a spool body having a through passage for tubing placement and a side outlet for production. A tubing hanger having a through passage and a side outlet is positioned in the spool body, with the side outlet of the tubing hanger positioned in flow communication with the side outlet in the spool body, usually in alignment. The production tubing string extends downwardly from the tubing hanger, and the through passage through the tubing hanger is sealed above the side outlet of the tubing hanger, so that production fluids will flow up the production string and then turn to flow through the side outlets of the tubing hanger and the spool body.
A downhole safety valve is carried by the production tubing. This valve is hydraulically actuated. One of the challenges in side valve tree design is in providing hydraulic connectivity between the downhole safety valve and the rig or platform on the surface across an interface situated in the SVT.
A highly suitable assemblage for providing such hydraulic connectivity is disclosed in U.S. Pat. No. 5,582,438 to Wilkins et al. issued Dec. 10, 1996, the disclosure of which is incorporated herein by reference. This assembly relies on a pair of coupling elements, one carried in the spool body, the other by the tubing hanger assembly to establish the hydraulic flow passage when the tubing hanger assembly seats in the spool body. A difficulty, however, is sometimes presented in operation of this device, as well as other similar devices, as the tubing hanger assembly is lowered downhole. The problem is that the downhole safety valve, which is carried in the production tubing string, is designed to fail in the closed position in the event that its supply of hydraulic fluid pressure is interrupted. The valve being in the closed position as the tubing string is lowered downhole prevents fluid flow through the tubing string, and can cause problems in seating the tubing hanger in the spool body.
A method for maintaining the downhole safety valve in the open position as the tubing string is lowered into the well would be very desirable.
An apparatus which is well suited for causing the downhole safety valve to stay in the open position as the tubing string is lowered into the well would be very desirable.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a charging device for pre-charging a hydraulic system.
It is another object of the present invention to provide a system for testing and actuating downhole equipment.
It is another object of the present invention to provide a method for maintaining a downhole valve in an open position while the tubing string is lowered downhole.
SUMMARY OF THE INVENTION
One embodiment of the present invention is directed to an apparatus for charging a fluid line through a coupler such as a penetrator employed in a SVT. The apparatus comprises a body having a longitudinal axis, a first end and a second end. The body is formed from a sidewall defining a bore positioned along the longitudinal axis and extending therethrough. The first end of the body forms a substantially flat face. There is a stem having a portion positioned within the bore of the body and being movably mounted in the body for movement from a first position to a second position with respect to the body. The sidewall defines a port that extends therethrough and communicates with the bore. A valve means is mounted outside of the sidewall and positioned in flow communication with the port. The valve means is used to fill the body with hydraulic fluid as described below. There is a means adjacent to the first end of the body for fastening the substantially flat face of the body to a coupler. There is also an adjustment means attached to the stem for adjusting the position of the stem within the body. This construction enables the attachment of a charging device to a coupler that can effectively charge the hydraulic system extending from the coupler.
In another embodiment, there is provided a method for charging a downhole hydraulic system. The method employs a charging device as described above to charge hydraulic system through a coupler or hydraulic penetrator, in most cases, with hydraulic fluid.
According to the method, the charging device is charged with hydraulic fluid. The stem is moved so that the stem contacts the valve means in the coupler and moves the valve means to an open position. The hydraulic system is charged with hydraulic fluid to a desired pressure through the valve means on the charging device. A downhole valve is opened with the hydraulic pressure. The valve means in the coupler is then closed to maintain the desired pressure within the hydraulic system so that the downhole valve remains in an open position.
This same method may also be employed in the reverse to release the pressure from the hydraulic system, to close and/or test a particular downhole valve.
In another aspect of the invention, there is also provided a method for installing a tubing hanger having a production string depending therefrom in a subsea wellhead while maintaining a hydraulically actuated downhole valve in an open position.
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Buskop Wendy K.
Buskop Law Group
Kvaerner Oilfield Products, Inc.
Walton George L.
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