Boring or penetrating the earth – Below-ground impact members – Fluid-operated
Reexamination Certificate
1999-03-19
2001-03-20
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
Below-ground impact members
Fluid-operated
C166S178000
Reexamination Certificate
active
06202767
ABSTRACT:
This invention relates to a jar mechanism, and in particular a jar mechanism for imparting a jarring impact to an object located in a borehole.
Drilling jars are typically installed in a drill string and enable an operator to deliver a jarring impact to the drill string if the drill string becomes stuck in the borehole being drilled.
Drilling jars generally consist of an outer housing and an inner mandrel. The housing is generally connected to the drill string below the jar and the inner mandrel is connected to the drill string above the jar. The inner mandrel has a shoulder which forms a hammer, and the housing has an internal shoulder which forms an anvil. The outer housing and the inner mandrel are releasably connectable such that the hammer and the anvil are held in spaced apart relationship, until tension or compression exerted between the outer housing and inner mandrel exceeds a certain level. When this occurs, the outer housing and the inner mandrel are released and the hammer is permitted to travel upwardly or downwardly to strike the anvil, thus creating a jarring force on the drill string below the jar.
Conventionally, hydraulic drilling jars are known to have internal hydraulic chambers that are pressure compensated with the annulus between the hydraulic drilling jar and the well bore by apertures in the outer housing. These hydraulic drilling jars have the disadvantage that the apertures present weak points in the outer housing which can fail.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a jar mechanism comprising an outer body member; an inner body member movably mounted on the outer body member; a releasable locking mechanism for locking the inner body member with respect to the outer body member; and a piston section which permits a load to be applied between the inner body member and the outer body member after the locking mechanism has released.
Preferably, the jar mechanism further comprises at least one flow passage to permit fluid located in the annulus between the outer body member and the inner body member to flow from one side of the locking mechanism to the other.
Preferably, the locking mechanism is released by applying a force greater than a threshold force between the inner body member and the outer body member. Typically, the locking mechanism comprises a first lock member on one of the outer and inner body members, and a second lock member on the other body member, the first and second lock members being engageable with each other to lock the body members together.
Typically, one of the first and second lock members is biassed towards the other by a biassing mechanism. Preferably, the first lock member is mounted on the outer body member and the first lock member is biassed towards the second lock member by the biassing mechanism.
Typically, the second lock member comprises a formation on the inner body member, and preferably, the formation has a profile that may be engaged by a corresponding profile on the first lock member.
Typically, the biassing mechanism comprises a pair of spaced rings, where the first lock member is located between the rings, and at least one biassing device that biasses the first and second rings toward the first lock member.
Preferably, the biassing device exerts a biassing force in a direction transverse to the direction of movement of the first lock member. Typically, the biassing force is exerted in a direction substantially parallel to the direction of movement of the inner body member and the first lock member moves in a direction substantially perpendicular to the direction of movement of the inner body member relative to the outer body member.
Typically, the side of each of the spaced rings adjacent the first lock member are tapered, and the ends of the first lock member are correspondingly tapered with respect to the rings such that the biassing device biasses the rings towards each other to bias the first lock member towards the second lock member.
Preferably, the first lock member comprises a plurality of segments, the segments being arranged circumferentially around the second lock member, and the sum of the angles subtended by the segments is less than 360°. Typically, there is a flow passage between each segment.
Typically, the spaced rings each have a flow passage formed therein. Preferably, the flow passages are formed on the inner and outer circumference of the rings.
According to a second aspect of the present invention, there is provided a jar mechanism comprising an outer body member; an inner body member movably mounted on the outer body member; a fluid chamber defined by the inner and the outer body members; and a resistance mechanism in fluid communication with the fluid chamber; the inner and the outer body members being movable relative to each other between a first configuration in which the resistance mechanism resists relative movement between the inner and the outer body members, and a second configuration in which the resistance mechanism resists relative movement of the inner and the outer body members to a lesser extent than the first configuration; the resistance mechanism comprising two valve devices, each valve device resisting movement of fluid within the fluid chamber in one direction and the valve devices being arranged to resist the movement of fluid in opposite directions. Preferably, the valve devices are arranged in a spaced apart relationship, and more preferably, the valve devices divide the fluid chamber into three sections such that the fluid flows between the three sections of the fluid chamber.
Preferably, in the second configuration of the inner and outer body members, the resistance mechanism substantially does not resist relative movement of the inner and outer body members. Preferably, the fluid is retained in the fluid chamber by an upper seal and a lower seal. Typically, the jar mechanism forms part of a drilling jar. Typically, in the first configuration, the resistance mechanism co-operates with a piston section.
Preferably, the piston section is mounted on the inner body member. Typically, the valve devices are located in the fluid chamber between the inner and outer body members.
Typically, the resistance mechanism includes a bypass device for permitting the fluid to flow around the respective valve device in a direction opposite to the respective first and second directions. Preferably, when one of the valve devices is restricting the fluid flow, the bypass device permits fluid flow around the other valve device. Typically, the resistance mechanism further comprises a pair of moveable members, where one of the valve devices is mounted on each moveable member. Preferably, each moveable member includes a said bypass device. Preferably, a moveable member is moveable between a first configuration in which the bypass device is inoperative, such that the fluid located in the fluid chamber is forced to pass through the valve device of the same moveable member, and a second configuration in which the bypass device is operative, such that the fluid located in the fluid chamber is permitted to bypass the valve device of the same moveable member.
Preferably, the piston section comprises a releasable coupling device on the inner body member for coupling to each moveable member, such that, when the coupling devices are coupled to the corresponding moveable member, and the inner body member moves relative to the outer body member, the moveable members are moved, and preferably, the valve device of one of the moveable members restricts the fluid flow and the bypass device of the other moveable member bypasses the fluid flow. Typically, when the coupling device is released from the moveable members, the inner body member is not restrained from relative axial movement with respect to the outer body member; that is, the inner and the outer body members are in the said second configuration.
Preferably, the coupling devices of the piston section are enlarged diameter sections of the inner body member which slidably engage the inner c
International Petroleum Equipment Limited
Pezzuto Robert E.
Ratner & Prestia
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