A double-acting jar is disclosed comprising: an outer housing; an inner mandrel at least partially disposed telescopically within the outer housing to define a fluid chamber between the inner mandrel and the outer housing, the fluid chamber containing fluid and being sealed; a valve disposed within the fluid chamber on one of the inner mandrel and the outer housing; the valve having a downhole portion that is movable between a downhole seated position in which the valve seats against the one of the inner mandrel and the outer housing and an unseated position, the downhole portion having a downhole restriction surface; the valve having an uphole portion that is movable between an uphole seated position in which the valve seats against the one of the inner mandrel and the outer housing and an unseated position, the uphole portion having an uphole restriction surface; the other of the outer housing and the inner mandrel having a cooperating restriction surface that cooperates with the downhole restriction surface and the uphole restriction surface to set the double-acting jar for a jar.

TECHNICAL FIELD

This apparatus relates to double-acting jars, in particular to double-acting jars that are actuatable to deliver sequential and repetitive up or down jars to a tubing string.

BACKGROUND

Various components of conventional drill pipe, coiled tubing or other down hole tools may get stuck in the well bore at times. Jars are used in the oilfield industry to deliver jarring blows to a tubing string in order to free a stuck component, such as a stuck section of pipe. Jars are also used in fishing operations, in order to collect and free a object stuck in a downhole well. Under these circumstances, repetitive upjarring or downjarring with a jarring tool can be useful. Double-acting jars exist that are capable of performing this function to a most degree, although many traditional double-acting jars can only perform sequential up and down jars.

Adapting a jar tool to a coiled tubing application presents some challenges to overcome. A coiled tubing operation may involve a continuous pipe or tubing, which is uncoiled from a reel as it is lowered into the well bore, and can be used in drilling or workover applications for example. However, coiled tubing presents a number of working constraints to the design of a tool. First of all, due to the limited strength of the coiled tubing, limited compressive loads can be placed on the tubing by the rig operator. Essentially, this means that downhole tools which require compressive force to operate, such as a jarring tool, must be capable of operating with the limited compressive load capability of coiled tubing. In addition, in coiled tubing applications the overall length of the downhole tool becomes significant since there is limited distance available at the wellhead, for example between the stuffing box and the blowout preventor, to accommodate the bottom hole assembly. A typical bottom hole assembly may include additional tools, for example, a quick disconnect, a sinker bar, a release tool of some type, and an overshot. Thus, the length of the jarring tool itself becomes particularly significant since the entire bottom hole assembly may be required to fit within the limited distance between the stuffing box and blowout preventor to introduce it into a pressurized well. Furthermore, within these confines, the jarring tool may be required to have a large enough internal bore to permit pump-down tools to pass. Thus, the coiled-tubing jarring tool may have a limited overall wall thickness in view of limited outer diameter conditions.

SUMMARY

The jar disclosed herein is capable of being actuated to carry out sequential up and down jars, and repetitive upjars, and repetitive downjars, and is of a simple design.

A double-acting jar is disclosed comprising: an outer housing; an inner mandrel at least partially disposed telescopically within the outer housing to define a fluid chamber between the inner mandrel and the outer housing, the fluid chamber containing fluid and being sealed; a valve disposed within the fluid chamber on one of the inner mandrel and the outer housing; the valve having a downhole portion that is movable between a downhole seated position in which the valve seats against the one of the inner mandrel and the outer housing and an unseated position, the downhole portion having a downhole restriction surface; the valve having an uphole portion that is movable between an uphole seated position in which the valve seats against the one of the inner mandrel and the outer housing and an unseated position, the uphole portion having an uphole restriction surface; the other of the outer housing and the inner mandrel having a cooperating restriction surface that cooperates with the downhole restriction surface and the uphole restriction surface to set the double-acting jar for a jar, the cooperating restriction surface being dimensioned so that, from relative movement of the inner mandrel and the outer housing, the cooperating restriction surface is movable from above to below the valve with a neutral position in which a portion of the cooperating restriction surface is between the downhole restriction surface and the uphole restriction surface; the downhole restriction surface incorporating a first bypass that is configured to allow bypass of fluid in the chamber when the downhole restriction surface and the cooperating restriction surface move past each other during re-setting of the jar to the neutral position; the uphole restriction surface incorporating a second bypass that is configured to allow bypass of fluid in the chamber when the uphole restriction surface and the cooperating restriction surface move past each other during re-setting of the jar to the neutral position; first jarring surfaces on the inner mandrel and outer housing respectively for jarring contact with each other during a jar in a downhole direction; and second jarring surfaces on the inner mandrel and outer housing respectively for jarring contact with each other during a jar in an uphole direction.

These and other aspects of the device and method are set out in the claims, which are incorporated here by reference.

DETAILED DESCRIPTION

Drill jars provide a large transient force impact to a tubing string in either an upward or downward direction. A jar may have an inner mandrel disposed within an outer housing, defining a fluid chamber filled with hydraulic fluid in between the two. The hydraulic fluid may be gas or liquid. A tensile or compressive force is applied, through the tubing string, to either the outer housing or the inner mandrel of the jar, forcing the outer housing and inner mandrel to move relative to one another. The relative movement between the two is initially restricted within the fluid chamber as the jar is set, such that the energy of the tensile or compressive force builds up in the tubing string. As soon as the outer housing and inner mandrel move far enough relative to one another to release, the energy built up in the tubing string is transferred into rapid relative motion between the inner mandrel and the outer housing. Jarring shoulders on both the inner mandrel and outer housing then impact one another, releasing a large amount of kinetic energy into the tubing string and causing a striking blow to the stuck object.

Referring toFIG. 2, a double-acting jar10illustrated, comprising an inner mandrel12and an outer housing14. Inner mandrel12is at least partially disposed telescopically within outer housing14to define a fluid chamber16between inner mandrel12and outer housing14. Fluid chamber16contains fluid and is sealed at for example an uphole18end and a downhole end20.

Referring toFIGS. 1A and 2, a valve22is disposed within the fluid chamber16on one of the inner mandrel12and the outer housing14, in this case the inner mandrel12as shown. The valve22has a downhole portion24, and an uphole portion26, for example as shown. Portions24and26may be provided as part of the same valve as shown.

Referring toFIGS. 1A,1B, and1E, downhole portion24is movable between a downhole seated position (shown inFIG. 1E) in which the valve22seats against the one of the inner mandrel12and the outer housing14the valve is positioned on, and an unseated position (shown inFIGS. 1A and 1B). Referring toFIGS. 1A,1B, and1E, uphole portion26is movable between an uphole seated position (shown inFIG. 1B) in which the valve22seats against the one of the inner mandrel12and the outer housing14that the valve is positioned on, and an unseated position (shown inFIGS. 1A and 1D).

Referring toFIG. 1E, jar10may use a suitable seating configuration for seating downhole portion24and uphole portion26, for example engagement between an uphole facing seating shoulder30, and a seating surface32of the downhole portion24. Referring toFIG. 1B, an analogous configuration is illustrated for uphole portion26, with engagement between a downhole facing seating shoulder34and a seating surface38of the uphole portion26. Referring toFIG. 11, other seating configurations are possible, for example between a lateral seating surface32A of valve22, and a corresponding lateral seating shoulder30A as the valve22slides into the seated position.

Referring toFIG. 1A, downhole portion24has a downhole restriction surface40, and uphole portion26has an uphole restriction surface42. The other of the outer housing14and the inner mandrel12, in this case outer housing14, has a cooperating restriction surface44that cooperates with the uphole restriction surface42and the downhole restriction surface40to set the double-acting jar10for a jar. Setting the jar causes energy in the drill string to build up for jarring release.

Referring toFIGS. 1C,1F, and1A, the cooperating restriction surface44is dimensioned so that, from relative movement of the inner mandrel12and the outer housing14, the cooperating restriction surface44is movable from above (shown inFIG. 1C) to below (shown inFIG. 1F) the valve22. Restriction surface44may have a neutral position (shown inFIG. 1A) in which a portion of the cooperating restriction surface44is between the downhole restriction surface40and the uphole restriction surface42. Referring toFIGS. 1A and 10, the restriction surface44may be fully between (shown inFIG. 1A) or partially between (shown inFIG. 10) the downhole restriction surface40and the uphole restriction surface42when in the neutral position.

Referring toFIG. 2, restriction surface44is spaced from uphole end18and downhole end20of fluid chamber16. In the embodiment illustrated inFIG. 2, restriction surface44is located on outer housing14, with valve22on inner mandrel12, although this orientation may be reversed. For example, cooperating restriction surface44may be on the inner mandrel12, with valve22positioned on outer housing14. Cooperating restriction surface44may be, for example, a shoulder, such as an annular shoulder. Restriction surface44may be of a suitable length for sufficiently setting valve22for a jar in either direction.

Referring toFIG. 1G, jar10, for example the downhole restriction surface40, incorporates a first bypass46that is configured to allow bypass of fluid in the chamber16, for example in the direction of flow lines48, when the downhole restriction surface40and the cooperating restriction surface44move past each other during re-setting of the jar10. Referring toFIG. 1D, jar10, for example the uphole restriction surface42, incorporates a second bypass50that is configured to allow bypass of fluid in the chamber16, for example in the direction of flow lines52, when the uphole restriction surface42and the cooperating restriction surface44move past each other during re-setting of the jar10. The first and second bypasses46and50, respectively, prevent the jar from setting while the cooperating restriction surface44is making its way back into the neutral position from a downjar or an upjar, respectively. This way, the jar10is not limited to performing jars in alternating directions only.

Referring toFIG. 1G, the first bypass46may be defined by one or more of the downhole portion24and the one of the inner mandrel12and the outer housing14that the valve is positioned on. Similarly, referring toFIG. 1Dthe second bypass50may be defined by one or more of the uphole portion26and the one of the inner mandrel12and the outer housing14that the valve22is positioned on. Referring toFIGS. 7A and 7B, the first bypass46may be defined from a downhole end58of the uphole restriction surface42to seating surface32of the downhole portion24. Similarly, the second bypass may be defined from an uphole end54of the downhole restriction surface44to seating surface38of the uphole portion26. In some embodiments, one or more of the first bypass46and the second bypass50comprise a channel60that extends between an outer exterior surface62to an inner exterior surface64of the valve22. Referring to7B and8B, more than one channel60may be provided, for example as shown.

Referring toFIGS. 7A and 7B, the first and second bypasses may effectively form flow passages that are exposed and fully defined when the jar is re-setting and the respective uphole or downhole portion that just carried out a jar is unseated. Referring toFIG. 1G, in the embodiment shown the first bypass46is defined by seating surface32, seating shoulder30, an undercut portion56of inner mandrel12, passage60, intermediate outer exterior surface62, and downhole end58of uphole restriction surface26. Referring toFIG. 7B, undercut portion56may be defined by a series of flats on the outer surface of inner mandrel12as shown. The purpose of undercut portion56may be achieved other ways, such as by defining a channel on exterior surface64of valve22or as a channel61(shown inFIG. 11) within inner mandrel12or valve22. Referring toFIG. 7B, in other embodiments the first bypass may be defined similarly, with the exception that instead of intermediate outer exterior surface62the first bypass is defined further by a passage66in intermediate outer exterior surface62to downhole end58. Passage66may be one or more of a reduced thickness section for example, a reduced or increased diameter section, a tapered section, and a slot. Passage66is illustrated inFIG. 7Bas a slot. Passage66is advantageous because intermediate outer exterior surface62can fit closely to restriction surface44, all they way to uphole restriction surface42, while still allowing fluid bypass to downhole end58. This means that, by the time restriction surface44reaches uphole restriction surface42, uphole restriction surface42is already aligned properly for entering cooperating restriction surface44. This reduces the chances of valve22jamming upon attempted setting. Referring toFIG. 8A, an embodiment is illustrated where intermediate outer exterior surface62comprises a reduced diameter surface relative to uphole restriction surface42. In this embodiment, passage66may still be provided as shown to aid in alignment. It should be understood that second bypass50may have the same corresponding characteristics as all embodiments of first bypass46. Also, plural bypasses may be present.

Referring toFIG. 6, in some embodiments downhole portion24and uphole portion26are separate valves. Referring toFIGS. 7A and 8A, exemplary embodiments of this may be envisioned by cutting valve22in half along the section lines7A and8A, respectively. Referring toFIG. 6, in these embodiments, one or more of an uphole end90of downhole portion24and a downhole end92of uphole portion26may define passage60. Referring toFIG. 9, in some embodiments, each of portions24and26may define a respective passage60, one or more of passages60being laterally spaced from respective ends90, or92, as shown.FIG. 9also illustrates an embodiment where a retaining shoulder94separates portions24and26.

Referring toFIGS. 2 and 4, jar10has first jarring surfaces70and72on inner mandrel12and outer housing14, respectively, for jarring contact with each other during a jar in a downhole direction. A downjar stroke is illustrated fromFIG. 2toFIG. 4. Referring toFIGS. 2 and 3, jar10has second jarring surfaces74and76on inner mandrel12and outer housing14, respectively, for jarring contact with each other during a jar in an uphole direction. An upjar stroke is illustrated fromFIG. 2toFIG. 3. It should be understood that first jarring surfaces70and72, and second jarring surfaces74and76may be formed at a suitable location on jar10, such that they are able to collide with one another to release the force of the jarring motion in a striking impact. The jarring surfaces may be positioned within or outside of fluid chamber16.

It should be understood that limited fluid transfer should occur across the valve22in order for restriction surface44to be able to move across the seated portion24or26during setting of the jar, unless the fluid in chamber16is compressible to a sufficient extent. Referring toFIG. 5B, one or more of the downhole portion24, the inner mandrel12, and the outer housing14may at least partially define a first metered bypass96that is configured to allow metered bypass of fluid in the chamber16when the restriction surface44cooperates with the downhole restriction surface40to set the double-acting jar10for a jar. Similarly, one or more of the uphole portion26, the inner mandrel12, and the outer housing14may at least partially define a second metered bypass98that is configured to allow metered bypass of fluid in the chamber16when the restriction surface44cooperates with the uphole restriction surface42to set the double-acting jar10for a jar.

Referring toFIGS. 1E,5A-5C, one or both of the first metered bypass96and the second metered bypass98may comprise one or more of a calibrated orifice100(shown inFIG. 5B) a calibrated pin102in orifice (shown inFIG. 5A), a calibrated grooved pin106in orifice (shown inFIG. 5C), a metering groove (not shown), and a close tolerance fit between the restriction surface44and one or more of the uphole and downhole restriction surfaces40and42, respectively (shown inFIG. 1E). Referring toFIG. 5B, the first and second metered bypasses96and98, respectively are defined by valve22, and comprise viscojets. Viscojets comprise calibrated orifices100, and may contain a one-way check valve99.

Referring toFIG. 5A, a calibrated pin102is fitted in an orifice104. The pin102is calibrated to allow a desired metering rate of fluid through orifice104. Referring toFIG. 5C, a calibrated grooved pin106, with for example having a spiral groove much like a screw, is positioned through an orifice108. Calibration refers to the dimensions being tailored to allow a desired metering rate of fluid when a pressure differential is present. A metering groove may be positioned at a suitable location, for example on one or more of restriction surface44, surfaces42and surface40, to allow a desired rate of fluid to be metered. Grooves of this kind include spiral grooves. A close tolerance fit refers to surfaces40and42being machined to fit with restriction surface44with a close tolerance that allows fluid to meter across the valve22through the annular gap between restriction surface44and the set one of surfaces40and42during build-up of the pressure differential. Sufficient metering bypasses may also be accomplished in other suitable ways. Referring toFIG. 5D, one or both of the first metered bypass96and the second metered bypass98may comprise a gap112defined by a piston ring110. One or more piston rings110may be positioned on one or more of the cooperating restriction surface44, the downhole restriction surface40, and the uphole restriction surface42to achieve this effect. One or more of surfaces40,42, and44may be defined by one or more piston rings. Each piston ring110defines a gap112, such as a calibrated gap, between the ends111of the piston ring110to facilitate metering of fluid. The piston ring may be set in place in a corresponding groove113, for example in the valve22as shown.

Referring toFIG. 5A, in some embodiments metered bypasses96and98are connected, forming a collective metered bypass. This may be advantageous in that it may require less parts to construct than a system with two distinct metered bypasses. Referring toFIGS. 5A-C, in embodiments where the metering bypasses do not include a close tolerance fit, the restriction surface44and surfaces40,42may effectively seal, for example using O-rings111or a positive seal fit.

Referring toFIGS. 1A-1H, operation of jar10during a sequence of an upjar and then a downjar is illustrated. Referring toFIG. 2, the entire jar10is illustrated with valve22in the neutral position. Referring toFIG. 1A, outer housing14slid from neutral in an uphole direction relative to inner mandrel12. Referring toFIG. 1B, as soon as restriction surface44moves over an initial portion of uphole restriction surface42to bias the uphole portion26into the uphole seated position, the jar10is set for an upjar and the fluid pressure differential is established across valve22. The pressure differential restricts the upward relative motion of outer housing14over inner mandrel12as restriction surface44moves over uphole restriction surface42, storing potential energy in the drill string. Referring toFIG. 1C, when restriction surface44clears uphole restriction surface42, the stored energy is suddenly released and transferred into rapid relative motion of outer housing14over inner mandrel12. Referring toFIG. 3, the rapid motion of outer housing14relative to inner mandrel12is abruptly halted upon colliding impact between second jarring surfaces74and76as shown, delivering an upward jarring impact.

Referring toFIG. 1D, jar10is then re-set, by relative movement of outer housing14in the downhole direction. When restriction surface44reaches and moves across uphole restriction surface42, second bypass50allows fluid bypass to occur across the valve22, preventing build up of the fluid pressure differential. Referring toFIG. 1E, this allows restriction surface44to return to the neutral position, from which an upjar or a downjar may be carried out as desired.

Referring toFIG. 1E, in this case a downjar is desired to be carried out. Thus, outer housing14is slid from neutral in a downhole direction relative to inner mandrel12. As soon as restriction surface44moves over an initial portion of downhole restriction surface40to bias the downhole portion24into the downhole seated position, the jar10is set for a downjar and the fluid pressure differential is established across valve22. The pressure differential restricts the downward relative motion of outer housing14over inner mandrel12as restriction surface44moves over downhole restriction surface40, storing potential energy in the drill string. Referring toFIG. 1F, when restriction surface44clears downhole restriction surface40, the stored energy is suddenly released and transferred into rapid relative motion of outer housing14over inner mandrel12. Referring toFIG. 4, the rapid motion of outer housing14relative to inner mandrel12is abruptly halted upon colliding impact between first jarring surfaces70and72as shown, delivering a downward jarring impact.

Referring toFIG. 1G, jar10is then re-set, by relative movement of outer housing14in the uphole direction. When restriction surface44reaches and moves across downhole restriction surface40, first bypass46allows fluid bypass to occur across the valve22, preventing build up of the fluid pressure differential. Referring toFIG. 1H, this allows restriction surface44to return to the neutral position, from which an upjar or a downjar may be carried out as desired.

In some embodiments, the valve22may be configured so that less energy is required to jar in one direction than in the other direction. For example, the clearance between the downhole restriction surface40and the cooperating restriction surface44may be greater than the clearance between the uphole restriction surface42and the cooperating restriction surface44, so that a downjar requires less weight on the drill string to carry out. This may be advantageous, particularly in coiled tubing applications where the compressive strength of the drill string is limited relative to the tensile strength of the drill string. Referring toFIG. 12, a valve22made according to this embodiment is illustrated. The jar10may be adapted with an appropriate mechanism to ensure that valve22can only be installed in the proper orientation, namely with downhole portion24directed towards downhole end20of the fluid chamber16. An exemplary mechanism of this sort may be achieved by providing a set of orientation-specific corresponding profiles25and26, respectively, on the valve22and the one of inner mandrel12and outer housing14that valve22is positioned on. This way, it is impossible to assemble the jar10with the valve22oriented backwards.

Double-acting jar10may be used with a jar enhancing device (not shown), in order to compound the jarring force of jar10. Ajar enhancing device may be connected, for example, either directly or indirectly above jar10in the tubing string. Jar enhancers are useful additions with jar10, for example, during a coiled tubing jarring operation, because they allow additional force to be built up for a jar, without imposing additional strain on the already limited compressive and tensile stress of the tubing string itself.

Jars10of the type disclosed herein may be used in, for example, fishing, drilling, coiled tubing, and conventional threaded tubing, operations. The use of up, down, above, below, uphole, downhole, and directional language in this document illustrates relative motions within jar10, and are not intended to be limited to vertical motions and motions carried out while jar10is positioned downhole. It should be understood that jar10may be used in any type of well, including, for example, vertical and deviated wells.

Referring toFIG. 2, fluid chamber16may comprise a floating seal19at at least one of uphole and downhole ends18and20, respectively. Floating seals19allow pressure differentials between fluid chamber16and outside of jar10to equalize, which may prevent a fluid chamber16from collapsing under extreme fluid pressures such as those experienced downhole. In some embodiments, valve22is annular in shape. Referring toFIG. 9, the valve22may not be annular, for example as illustrated by the section view.

Referring toFIG. 2, fluid chamber16need not be annular in shape. In some embodiments, there may be one or more fluid chambers16, each one operating according to the embodiments disclosed herein for jarring operation. Plural valves22, and plural restriction surfaces44may also be employed. Either or both of inner mandrel12and outer housing14may be individually composed of, for example, one or more units connected together. Each unit may be, for example, threadably connected together as is well known in the art, and as is illustrated in the figures. Outer housing14and inner mandrel12may be, for example, tubulars. In the embodiment illustrated inFIG. 2, in a downhole application, outer housing14may be connected, directly or indirectly, to a tubing string (not shown), whereas inner mandrel12would be connected, directly or indirectly, to, for example, a fishing tool (not shown). In some embodiments, this orientation is reversed. It should be understood that jar10can be oriented upside down in a well, and still carry out the intended function of the jar. In addition, valve22may be positioned on outer housing14in the reverse orientation of that shown in the figures.

As indicated above, the double-acting jar disclosed herein may be used with coiled tubing. Jar10is advantageous for coiled tubing operations, because it is adapted to deliver powerful jarring blows in repetitive or sequential uphole and downhole directions, within a tool length that is much shorter than other double-acting jars, which incorporate multiple valves and restrictions. In some embodiments, compressible hydraulic fluid may be used.

A suitable alignment mechanism may be used to align one or more of portions24and26in the jar10, for example alignment splines (not shown) an engaging exterior surface, for example surfaces64or62of valve22.

In the claims, the word “comprising” is used in its inclusive sense and does not exclude other elements being present. The indefinite article “a” before a claim feature does not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.