Wells – Processes – Operating valve – closure – or changeable restrictor in a well
Reexamination Certificate
1999-02-17
2001-04-24
Neuder, William (Department: 3672)
Wells
Processes
Operating valve, closure, or changeable restrictor in a well
C166S383000, C166S386000, C166S317000, C166S324000, C166S332300, C166S334400
Reexamination Certificate
active
06220359
ABSTRACT:
TECHNICAL FIELD
The invention generally relates to valves for downhole use in oil and gas wells. More particularly, the invention relates to downhole safety valve.
BACKGROUND OF THE INVENTION
In oil and gas wells, uncontrolled downhole fluid pressures can cause a dangerous situation. Depending on the downhole conditions, it is usually possible to predetermine a threshold pressure differential between a higher fluid pressure in an area exterior of the downhole tubing string adjacent where a safety-valve is to be positioned, and a lower fluid pressure interior of the tubing string that is considered to present an undesirable or possibly dangerous situation. For example, excessive fluid pressure in a production zone that is unbalanced by fluid pressure interior of the tubing string adjacent the production zone may present a highly dangerous situation in which hydrocarbons and gases may be driven at uncontrolled pressures uphole through the tubing string. In extreme cases, this can result in a blow-out of the well. A safety valve is intended to automatically actuate when such a condition occurs.
Another situation where this type of tool is valuable is if a leak develops in the tubing string above the valve that allows fluid pressure to communicate into the annular, where annulus pressure is harder to control. In this situation, it would be advantageous to have a valve that would automatically shut in the well.
It would be advantageous to have a safety valve that could be re-opened in response to a sufficient increase in interior fluid pressure over the exterior fluid pressure, whereby the downhole fluids can be pumped through the safety valve back into the formation.
It would also be advantageous to have a safety valve that would open a circulating valve after closing the fluid flow through the safety valve, whereby fluid can be circulated between the tubing string and the annulus while the flow through the safety valve is closed.
To operate successfully in the harsh and remove downhole environments, a simple and reliable safety valve structure and method would be highly advantageous.
SUMMARY OF THE INVENTION
According to the invention, a safety valve is provided for downhole use in a well. In general, the safety valve includes a housing having an interior fluid flow passage therethrough and at least one circulating port in the housing for providing fluid communication between the interior fluid flow passage and the exterior of the housing. A piston is operatively positioned within the housing for movement between a first position and a second position in response to a fluid pressure differential between the interior fluid flow passage and the exterior of the housing. A slip is operatively connected to the piston, whereby over a first range of the movement of the piston the slip moves with the piston, and over a second range of the movement of the piston the slip does not move with the piston. A first valve is positioned within the housing for opening and closing the interior fluid flow passage of the housing, and a second valve is positioned within the housing for opening and closing the circulating port. An operative connection is provided between the slip and either one of the first and second valves, whereby the first range of the movement of the piston operates the one valve. An operative connection is provided between the piston and the other one of the first and second valves, whereby the second range of the movement of the piston operates the other valve.
The valves for controlling flow and for controlling circulation can be connected to be operated sequentially by the piston. For example, the range of movement of the piston is preferably structured such that when the piston moves from the first position to the second position, the first valve closes and then the second valve opens. When the piston moves in the reverse direction from the second position to the first position, the second valve closes and then the first valve opens. The second valve for controlling the circulation port is preferably located uphole of the first valve, which is normally expected to be the lower pressure side of the safety valve.
According to the invention of the safety valve, a break-away release is used that breaks in response to a predetermined force related to the fluid pressure exterior of the housing. The break-away release is adapted to break before the fluid pressure exterior of the housing can cause the piston to move. The break away release is preferably a rupture disk operatively positioned between the piston and the fluid pressure exterior of the housing.
The invention also includes a method of operating a downhole safety valve. The method includes the step of operatively mounting a piston in a housing for movement between a first position and a second position. The method also includes the step of operatively connecting a slip to the piston, whereby over a first range of the movement of the piston the slip moves with the piston, and over a second range of the movement of the piston the slip does not move with the piston. A first valve is positioned within the housing for opening and closing an interior fluid flow passage of the housing, and a second valve is positioned within the housing for opening and closing a circulating port between the interior fluid flow passage and the exterior of the housing. A slip is operatively connected to one of the first and second valves, whereby the first range of the movement of the piston operates the one valve. The piston is operatively connected to the other one of the first and second valves, whereby the second range of the movement of the piston operates the other valve. The step of exposing the piston to a fluid pressure differential between the interior fluid flow passage and the exterior of the housing causes to move the piston between the first position and the second position, thereby operating the first and second valves.
The steps of constructing and operating the downhole safety valve can be performed such that when the piston moves from the first position to the second position, the first valve closes and then the second valve opens; and when the piston moves in the reverse direction from the second position to the first position, the second valve closes and then the first valve opens. When the valve is oriented for downhole use, the second valve is preferably located uphole of the first valve.
The inventive method includes the step of operatively positioning a break-away release that breaks in response to a predetermined force related to the fluid pressure exterior of the housing. The break-away release is adapted to break before the fluid pressure exterior of the housing can cause the piston to move. The break away release is preferably a rupture disk operatively positioned between the piston and the fluid pressure exterior of the housing.
These and other aspects and advantages of the invention will become apparent to persons skilled in the art from the following drawings and detailed description of a presently most preferred embodiment of the invention.
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Booth John F.
Halliburton Energy Service,s Inc.
Herman Paul I.
Neuder William
Walker Zakiya
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