Wells – Valves – closures or changeable restrictors – Destructible element
Patent
1997-11-20
1999-08-24
Schoeppel, Roger
Wells
Valves, closures or changeable restrictors
Destructible element
166192, 137 71, E21B 2304, E21B 3414
Patent
active
059413093
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to tools for use in wellbores which are actuated by means of actuating balls.
It is well known that actuating balls are widely used in the oil and gas drilling industry to operate a variety of downhole tools. These tools may be used for drilling, testing, completing and remedial work. Conventional actuating balls are typically made from steel, bronze, plastic, bakelite or composite materials, and once received by a downhole tool, remain in the well configuration until removed by mechanical or manual means. Thus, once a conventional actuating ball is received by a tool, it remains an obstruction to fluid flowing down the tubing string until removed as described. In certain circumstances, the removal of a deployed actuating ball can be essential for the completion of a downhole operation, and the mechanical or manual methods presently employed for removal can be inconvenient and extremely expensive.
It is an object of the present invention to provide means for actuating a downhole tool with an actuating ball without the actuating ball becoming an obstruction to fluid flowing through the tool once the tool has been actuated.
A first aspect of the present invention provides a method of actuating a tool located in a wellbore, the method comprising the sequential steps of: in the tool for receiving the actuating ball; force to the seat and thereby actuate the tool, the force being transmitted to the seat through the actuating ball; and
It is preferable for the frangible actuating ball to be located on the seat by introducing the actuating ball into a fluid flow travelling down the tubing string. It is further preferable for the step of breaking the actuating ball to include pumping fluid down the tubing string so as to increase the force transmitted by the actuating ball and thereby break the actuating ball.
Thus, the method of the present invention involves introducing an actuating ball into the tubing string and progressing the actuating ball down the string towards the tool to be actuated. The actuating ball may be progressed down the tubing string by the action of gravity or a fluid flowing within the string. Once the actuating ball is received by the seat, the flow of fluid down the tubing string is restricted or prevented, and therefore, a pressure differential across the actuating ball is generated. The pressure differential results in a force being applied to the seat of the tool which may be harnessed to actuate the tool. Once the tool has been actuated, the actuating ball remains located on the seat forming an obstruction. When the obstruction generated by the actuating ball is to be removed, the actuating ball is broken into a plurality of small fragments which are then removed by the flow of fluid down the tubing string. The actuating ball may be broken using one of a number of possible techniques, but it is preferably broken by pumping fluid down the tubing string so as to increase the pressure differential across the actuating ball until the structure of the ball fails.
A second aspect of the present invention provides a frangible actuating ball for use in the aforementioned method, the frangible actuating ball comprising a frangible wall provided with a pressure relief port adapted to equalise the pressure exerted on the sides of the wall. When the actuating ball is suspended in a downhole fluid flow, the pressure relief port allows fluid surrounding the actuating ball to flow into the ball and equalise the pressure exerted on the inner and outer surfaces of the frangible wall. Failure of the actuating ball structure on exposure to the hiqh hydrostatic pressures found at well depths is thereby prevented. However, the pressure relief port does not equalise the pressure differential generated when the actuating ball is received by the seat and does not therefore prevent the tile ball from failing when required.
Preferably, the frangible wall has a spherical shape and is preferably provided as two separate portions attached to one another by suitable attachment means. Th
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patent: 4557331 (1985-12-01), Stout
patent: 4589495 (1986-05-01), Langer et al.
patent: 4945947 (1990-08-01), Westra et al.
patent: 5070941 (1991-12-01), Kilgore
patent: 5180016 (1993-01-01), Ross et al.
patent: 5411049 (1995-05-01), Colvard
patent: 5413180 (1995-05-01), Ross et al.
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