Wells – Valves – closures or changeable restrictors – Destructible element
Patent
1987-03-04
1989-01-10
Suchfield, George A.
Wells
Valves, closures or changeable restrictors
Destructible element
166319, 137 70, 1375137, 1375155, E21B 3410
Patent
active
047967048
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a drop-ball sub-assembly for a down-hole device, for example for use in an oil drilling rig or the like, and is particularly but not exclusively, useful in association with down-hole motor devices.
Generally a drilling rig for core retrievel comprises at the drilling end an inner core barrel and an outer barrel coaxially arranged and defining therebetween a flow space for drilling fluid. The inner core barrel needs to be flushed before drilling to remove detritus which may have been picked up during lowering to a drilling position, to exclude such detritus from a drilled core sample. Thus drilling fluid is used to flush the core tube immediately prior to drilling and then, in conventional tube drills, a ball is dropped from the surface to engage a seating at the upper end of the core barrel to cut off the flow of fluid into the core barrel. This is not possible with a rig using a down-hole motor and it has been proposed in GB-2 048 996B to provide a drop-ball sub-assembly below a drive device and above a core barrel, the sub-assembly including a drop-ball normally disposed in a lateral cavity outside a flow passage to the upper end of the core barrel and retained therein by a spring loaded sleeve. In operation flushing fluid is initially directed through the flow passage to achieve flushing and then the flow rate is increased to exert a force on the sleeve to drive it against the bias to register an aperture in the sleeve with the cavity, allowing the ball to drop out into the flow passage and fall onto a seating to close the upper end of the core barrel against flow of fluid thereinto.
Several down-hole tools or specialist devices which are hydraulically operated are dependent upon a change in the flow path of the drilling fluid or similar liquid to activate them or to allow them to carry out their specialist function.
A known method of creating this change in the flow path is to drop a steel ball into the flow path from the surface of the hole and allow the drilling fluid or similar liquid to carry the ball, assisted by gravity down the hole until the ball lodges in a suitably prepared seat within the down-hole tool or specialist device. The lodging of the ball in the seat closes off the main flow path and prevents the fluid from passing further down the hole. An alternative flow path through which the fluid would not normally flow is now the only path available to the fluid. The fluid by travelling down this alternative flow path has changed its course and can be used to perform the desired requirement of the down-hole tool or specialist device.
There are two distinct disadvantages in such a system, namely:
(i) When another down-hole tool is used in the drill-string, i.e. located between the hydraulically operated device and the surface whose design permits fluid flow through the tool but has an insufficient aperture to allow a ball to pass through it, e.g. a hydraulically operated down-hole positive displacement drilling motor or a turbine or a measurement-while-drilling monitor. the surface and the ball lodging in the seat provided in the down-hole device is prolonged and is non-productive.
Typical examples where a ball is used to operate down-hole devices are when coring and when retrieving junk from the bottom of the hole using a hydraulically operated junk retriever.
It is an object to provide an improved drop-ball sub-assembly for down-hole use, for example, in conjunction with a core barrel and an outer barrel of a drilling rig in which flushing fluid flow to the core barrel is required before taking a core sample in which a surface indication of the release of the ball and closure of the upper end of the core barrel to flushing fluid flow can readily be ascertained or in conjunction with down-hole tools dependent on change in flow path of drilling fluid or the like to activate them.
A drop-ball sub-assembly for down-hole use according to the present invention comprises a tubular casing defining a flushing fluid flow passage between inlet and outlet ends adapted for coup
REFERENCES:
patent: Re24659 (1959-06-01), Clark
patent: 3473609 (1969-10-01), Allen
patent: 3599713 (1971-08-01), Jenkins
patent: 3776258 (1973-12-01), Dockins, Jr.
patent: 4114704 (1978-09-01), Maurer et al.
patent: 4510994 (1985-04-01), Pringle
Forrest John
Stewart William
Tulloch Rory
Drilex UK Limited
Kisliuk Bruce M.
Suchfield George A.
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