Wells – Pistons – fluid driven into well – Surrounding conduit valve or closure opened by piston
Reexamination Certificate
2000-07-31
2001-11-06
Suchfield, George (Department: 3672)
Wells
Pistons, fluid driven into well
Surrounding conduit valve or closure opened by piston
C166S153000, C166S155000, C166S179000, C166S193000
Reexamination Certificate
active
06311771
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims benefit of Great Britain application number 9723581.6, filed Nov. 7, 1997, which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plug for use in wellbore operations and an apparatus for launching said plug.
2. Description of the Related Art
During the construction of an oil or gas well a hole is bored in the ground. A string of casing is lowered down the hole and the annular space between the casing and the wellbore filled with cement.
In order to inhibit the cement mixing freely with other wellbore fluids it is normal to use two devices which are referred to as “cementing plugs”. When it is desired to cement the casing in place a first (bottom) cementing plug is released into the casing. The cement is then pumped into the casing and pushes the bottom plug downwardly. When the desired volume of cement has been introduced into the casing a top plug is introduced into the casing and pumped downwardly by a convenient fluid, typically sea water or circulating fluid. The cement then travels down the casing trapped between the bottom and top plugs. When the bottom plug reaches the bottom of the casing it lands on a one way valve known as a float collar. Pressure is applied to the top plug until a bursting disk in the bottom plug ruptures and allows the cement to be pushed through a flow bore in the bottom plug, through the float collar and upwardly into the annular space between the casing and the bore. The description thus far relates to normal operation. However, occasionally the bottom plug and the top plug are released simultaneously with the result that a large column of cement is pumped down the casing on top of the top plug. Since the top plug is designed to withstand high pressures it will not rupture and consequently the cement sets and has to be drilled out.
A large number of devices have been designed for preventing inadvertent simultaneous release of the bottom plug and top plugs and those which have been designed for use at the surface of a land well are generally satisfactory. However, the problem which does remain is when a casing is extended by a liner and it is necessary to cement the liner in position. In this case the bottom and top plugs have to be released remotely from the surface. Although there are a number of apparatus intended for inhibiting simultaneously release of the top and bottom plugs in these circumstances it is still not unknown for the plugs to be released simultaneously with expensive consequences.
SUMMARY OF THE INVENTION
The present invention approaches this problem from an entirely new angle and, whilst it is primarily intended for use with liner hanging and drilling equipment, can also be used at the surface.
According to the present invention there is provided a plug for use in wellbore operations, which plug comprises a body having a flow path therethrough and a cap for blocking flow of fluid through said flow path, characterized in that said cap is detachable from said body in use.
The present invention should not be confused with plugs of the type having hinged caps which are not detachable from the body in use.
Preferably, said plug further comprises a restraining device attached to said cap.
Advantageously, said restraining device comprises a flexible belt.
Preferably, said plug further comprises a sealing ring to provide a substantially fluid tight seal between said cap and said body of said plug.
Advantageously, said plug comprises elastomeric material.
Preferably, said cap is attached to said body by fingers.
The present invention also provides an apparatus for launching at least two plugs, said apparatus comprising a mandrel, a lower plug and an upper plug releasably disposed with respect to said mandrel, wherein said upper plug comprises a body having a flow path therethrough and a cap for blocking fluid flow through said path characterized in that said cap is detachable from said body in use.
Preferably, said apparatus further comprises a restraining device attached to said cap and to said mandrel.
Advantageously, said restraining device comprises a flexible belt.
Preferably, said restraining device is attached to said mandrel via a shear pin.
Advantageously, said shear pin is adapted to be sheared after completion of an operation intended to release said upper plug.
Preferably, said operation is landing of a dart intended to initiate release of said upper plug.
Advantageously, said apparatus further comprises a sealing ring to provide a substantially fluid tight seal between said cap and said body of said plug.
Preferably, said cap is attached to said body by fingers.
REFERENCES:
patent: 1527749 (1925-02-01), Raymond
patent: 1772871 (1930-08-01), MacClatchie
patent: 2560901 (1951-07-01), Smith
patent: 2907392 (1959-10-01), Ormsby
patent: 4164980 (1979-08-01), Duke
patent: 4624312 (1986-11-01), McMullin
patent: 5242018 (1993-09-01), LaFleur
patent: 5433270 (1995-07-01), LaFleur
patent: 5762139 (1998-06-01), Sullaway et al.
patent: 2 641 319 (1990-06-01), None
patent: WO 94/27026 (1994-11-01), None
Gudmestad Tarald
Tilton Frederick Thomas
Moser, Patterson & Sheridan L.L.P.
Suchfield George
Weatherford / Lamb, Inc.
LandOfFree
Plug for use in wellbore operations and apparatus for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plug for use in wellbore operations and apparatus for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plug for use in wellbore operations and apparatus for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597615