Wells – With jar means for releasing stuck part
Reexamination Certificate
2000-02-04
2001-12-11
Dang, Hoang (Department: 3672)
Wells
With jar means for releasing stuck part
C175S299000
Reexamination Certificate
active
06328101
ABSTRACT:
This application is the U.S. national phase application of PCT International Application No. PCT/GB98/02388 filed Aug. 7, 1998.
The present invention relates to an impact enhancing tool, and particularly, but not exclusively, relates to a double acting impact enhancing tool for inclusion in a string of tubulars, where a drilling jar is also included in the string.
During the drilling of boreholes for oil and/or gas wells the drill pipe may become stuck in the borehole during drilling and it is not possible to move the stuck pipe by normal upward pulling or downward pushing forces. In order to free the drill pipe it may be necessary to deliver jarring forces to the drill string. Hence, it is common practice to include a drilling jar in the drill string and a jar enhancer located above the jar, and separated from the jar by a number of lengths of drill pipe. When activated, the jar exerts an upwardly or downwardly directed jarring force on the stuck drill pipe.
Jars generally consist of an outer body member and an inner body member where one of the members is connected to the drill string below the jar and the other member is connected to the drill string above the jar. There is normally a hammer device on one of the members and an anvil on the other member. The outer body member and the inner body member are releasably connectable such that the hammer and the anvil are held in a spaced apart relationship, until tension or compression exerted on the jar exceeds a certain level. When this occurs, the outer body member and the inner body member are released and the hammer is free to travel upwardly to strike the anvil, thus exerting the impact force required to release the stuck object.
In order to enhance the jarring impact delivered by the jar, an enhancer may be used in conjunction with the jar. The enhancer is normally located in the drill string above the jar and is usually separated from the jar by drill pipe. The weight of drill pipe between the jar and the enhancer is used to enhance the impact force delivered by the jar. When the jar is released, a portion of the enhancer accelerates upwards (or downwards) so that the weight of drill pipe accelerated contributes to the jarring force produced by the jar.
Conventional enhancers comprise an inner and an outer member which are slidable with respect to one another, with the outer ends of the members being coupled to the drill pipe above and below the tool. An energy storing means such as a compressible fluid is disposed between, and acts between, the inner and the outer members. The energy storage means in double acting enhancers are normally split into two chambers, such that the enhancer can be used to enhance the impact of the jar both in the upwards and downwards direction. Examples of the conventional tools are shown in UK Patent No 2123880, EP Patent No 0314130, UK Patent Publication No 2285996, UK Patent Publication No 2283259 and UK Patent No 2210082. However, all these conventional tools require two chambers to house the energy storing means, which therefore increases their complexity, length and cost.
Another example of a conventional impact enhancing tool is shown in PCT International Publication No WO 93/04258 (International Application No PCT/U.S. Ser. No. 92/05618) as being a double acting accelerator having a compressible fluid located in a single fluid chamber. Energy can be stored in the compressible fluid when there is movement of the inner mandrel with respect to the outer housing in either axial direction. However, this conventional tool further requires two coiled springs (in addition to the single fluid chamber) in order to centralise the tool prior to the energy being stored in the compressible fluid. This is important so that the maximum stroke of the tool, in either axial direction of movement, can be achieved. Therefore, the additional two coiled springs result in extra complexity within the tool, with the result that there are extra components required. Further, with the requirement of a chamber to house the fluid, there is the resulting disadvantage that if the integrity of the chamber is compromised, then the tool is effectively inoperative.
According to the present invention, there is provided an impact enhancing tool having a long axis and comprising an outer body member; an inner body member axially movable in relation to the outer body member; and spring means, optionally disposed between the body members, such that movement of the inner body member in either axial direction with respect to the outer body member causes energy to be stored in the spring means.
Preferably, energy is stored in the spring means by compression thereof. Typically, the spring means is disposed in an annulus formed between the inner and outer body members.
Preferably, the spring means is disposed between an upper compression device located at one end of the spring means, and a lower compression device located at the other end of the spring means, and preferably, the upper and lower compression devices butt against the respective ends of the spring means. The spring means may comprise a single spring, or a stack of bellville washer springs or the like, or an array of springs arranged side by side or otherwise extending between two axially spaced points of the device.
The compression devices optionally comprise one or more elements slidable in the tool, and optionally provide a shoulder to abut the spring means.
Typically, movement of the inner body member into the outer body member moves the upper compression device with respect to the outer body member whilst the lower compression device remains stationary with respect to the outer body member. Typically, movement of the inner body member out of the outer body member moves the lower compression device with respect to the outer body member whilst the compression device remains stationary with respect to the outer body member.
Preferably, the inner body member comprises an upper coupling surface and a lower coupling surface for respective coupling with the upper and lower compression devices to effect movement of the upper or lower compression devices, with respect to the outer body member. More preferably, the upper and lower coupling surfaces are respective upper and lower radially outwardly projecting shoulders.
Preferably, the outer body member comprises an upper seating surface and a lower seating surface against which the respective upper and lower compression devices seat to prevent movement of the upper or lower compression devices, with respect to the outer body member. More preferably, the upper and lower seating surfaces are respective upper and lower radially inwardly projecting shoulders.
Preferably, the inner body member further comprises a stroke restraint device which restrains the inner body member from moving further than a known distance with respect to the outer body member.
Typically, the inner body member comprises an upper and a lower stroke restraint device which make contact with respective upper and lower stroke restraint devices mounted on the outer body member. Preferably, the upper and lower stroke restraint devices mounted on the outer body member are respective said upper and lower radially inwardly projecting shoulders.
An example of an impact enhancing tool will now be described, by way of example only, with reference to the accompanying drawings in which:
FIG. 1
is a cross-sectional side view of an enhancer tool in accordance with the present invention, in a mid point or neutral configuration;
FIG. 2
is a cross-sectional side view of the tool of
FIG. 1
, in an open or stretched configuration;
FIG. 3
is a cross-sectional side view of the tool of
FIG. 1
, in a closed or compressed configuration;
FIG. 4
is a cross-sectional side view of the middle portion of the tool of
FIG. 1
, in greater detail;
FIG. 5
is a cross-sectional side view of the upper part of the middle portion of the tool shown in
FIG. 4
, in greater detail;
FIG. 6
is a cross-sectional side view of the lower part of the middle portion of the tool shown in
FIG. 4
,
Dang Hoang
International Petroleum Equipment Limited
Ratner & Prestia
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