Jarring device and method

Abstract

In a jarring device and method for applying an impact to a casing of a wellbore in a subterranean or subsea formation, the jarring device includes a hammer and a driving means for driving the hammer between a first position in which the hammer is spaced from the casing, and a second position in which the hammer contacts the casing, such that the driving means is operable during use to drive the hammer from the first position to the second position so as to impact the casing. The hammer is reciprocated by the driving means.

Claims

1. A jarring device for applying an impact to a casing of a wellbore in a subterranean or subsea formation, the jarring device comprising: a hammer; and a driving means for driving the hammer between a first position in which the hammer is spaced from the casing and a second position in which the hammer contacts the casing, such that the driving means is operable during use to drive the hammer from the first position to the second position so as to impact the casing, wherein the hammer is reciprocated by the driving means, and wherein the driving means is a shunt arranged to impact the hammer and thereby directly drive the hammer from the first position to the second position.

2. The jarring device as claimed in claim 1, further comprising a body wherein the hammer moves relative to the body when the hammer is driven from the first position to the second position.

3. The jarring device as claimed in claim 1, further comprising: a rotatable inner shaft, wherein the shunt is supported by the inner shaft, and wherein the inner shaft is arranged such that rotation thereof causes rotation of the shunt thereabout to cause the shunt to drive the hammer from the first position to the second position; and a sleeve disposed about the rotatable inner shaft, wherein the hammer is supported by the sleeve.

4. The jarring device as claimed in claim 1, wherein the driving means is a hydraulic, mechanical, or electromechanical actuator.

5. The jarring device as claimed in claim 1, further comprising a biasing mechanism arranged to bias the hammer to the first position and to return the hammer to the first position from the second position.

6. The jarring device as claimed in claim 1, wherein the hammer is a first hammer and the jarring device comprises a second hammer movable between a first position in which the second hammer is spaced from the casing and a second position in which the second hammer contacts the casing.

7. The jarring device as claimed in claim 6, further comprising a connection which connects the first hammer and the second hammer so that movement of either the first hammer or the second hammer causes the other of the first hammer and the second hammer to move synchronously therewith, wherein the driving means is operable to drive the second hammer from the first position in which the second hammer is spaced from the casing and the second position in which the second hammer contacts the casing.

8. The jarring device as claimed in claim 1, wherein the hammer is a first stage hammer and the jarring device comprises a second stage hammer movable between a first position in which the second stage hammer is spaced from the casing and a second position in which the second stage hammer contacts the casing, and wherein the driving means is a first driving means and the device comprises a second driving means operable to move the second stage hammer from its first position to its second position.

9. The jarring device as claimed in claim 1, wherein the hammer and the driving means comprise a stage, and wherein the jarring device comprises a plurality of stages.

10. An apparatus for removing a casing from a wellbore, comprising: the jarring device as claimed in claim 1, wherein the jarring device is disposed on a string; and a spear disposed on the string above the jarring device.

11. The apparatus as claimed in claim 10, further comprising a longitudinal jarring device arranged to provide jarring along the string in a longitudinal direction of the wellbore.

12. The apparatus as claimed in claim 10, further comprising a controller configured to control operation of the jarring device.

13. A method of applying an impact to a casing of a wellbore in a subterranean or subsea formation, the method comprising: positioning a jarring device within the casing, the jarring device comprising a hammer and a driving means for driving the hammer between a first position in which the hammer is spaced from the casing and a second position in which the hammer contacts the casing; and operating the driving means to impact the hammer and thereby directly drive the hammer from the first position to the second position to apply an impact to the casing, wherein the hammer is reciprocated by the driving means.

14. The method as claimed in claim 13, wherein the driving means comprises a shunt, and wherein operating the shunt comprises rotating the shunt about an inner shaft to cause the shunt to drive the hammer from the first position to the second position.

15. The method as claimed in claim 13, further comprising repeatedly applying impacts to the casing by driving the hammer, and changing the frequency of impacts by changing how frequently the hammer is driven by the shunt.

16. The method as claimed in claim 13, further comprising, after applying an impact to the casing, moving the jarring device within the casing to apply an impact to another part of the casing.

17. A method of removing a casing from a wellbore in a subterranean or subsea formation, the method comprising: applying an impact to the casing using the method as claimed in claim 13; and applying a force to the casing to pull the casing from the wellbore.

18. The method as claimed in claim 13, further comprising breaking up material surrounding the casing, wherein the material is cement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Certain embodiments of the invention are described below, by way of example only, and with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic view of an apparatus for removing casing from a wellbore comprising a jarring device according to the present invention;

(3) FIG. 2 is a schematic view of an apparatus for removing casing from a wellbore comprising a jarring device according to the present invention;

(4) FIG. 3 is a schematic view a jarring device according to the present invention;

(5) FIG. 4 is a schematic view of a stage of the jarring device of FIG. 3 with a first hammer and a second hammer in respective first positions;

(6) FIG. 5 is a schematic view the stage of FIG. 4 with the first hammer in a second position; and

(7) FIG. 6 is a schematic view of the stage of FIGS. 4 and 5 with the second hammer in a second position.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows a schematic depiction of a jarring device 100 in a wellbore in a subterranean formation. The wellbore is defined within the formation and is lined by a casing 10 along its length. The casing is surrounded by fill 12 such as cement and/or other material. The jarring device 100 is disposed on a string 14 within the casing 10. Also disposed on the string 14, above the jarring device 100, is a spear 16 which may be deployed into the casing 10 to fix the string 14 at a position within the casing 10. A longitudinal jar 18 is provided for applying jarring forces in the longitudinal direction of the string 14. A casing cutter 20 is also provided and may be used to cut the casing 10 to reduce the length of casing 10 to be pulled.

(9) In use, the jarring device 100 is used to apply impact and vibrational forces to the casing 10 in a lateral (e.g. radial) direction. These forces will break up the fill 12 (e.g. cement and/or other material) surrounding the casing 10 in the region of the jarring device 100. The jarring device 100 may be run along a length of the casing 10 the break up the fill 12 around that length and may make pulling the casing 10 from the wellbore easier.

(10) The casing cutter 20 is then used to cut the casing 10, and the spear 16 is engaged to anchor the casing 10 to the string 14. The string 14 is then pulled in order to pull the casing 10 from the wellbore. The jar 18 may be operated to apply longitudinal jarring forces to the string 14 to help dislodge the casing 10 from the surrounding fill 12 and remove the casing 10 from the wellbore. The jarring device 100 may also be operated to apply lateral forces to the casing 10 and help reduce the friction on the casing 10 from the surrounding fill 12 and further reduce the force needed to pull the length of casing 10 from the wellbore.

(11) FIG. 2 shows a similar apparatus as that of FIG. 1, but further comprising a vibrator 22 and another suitable component 24. The vibrator 22 may be operated while pulling on the casing 10 to help loosen the casing 10 from the surrounding fill 12. The vibrator 22 applies much smaller forces than does the jarring device 100.

(12) FIG. 3 shows a schematic view of a jarring device 100. The jarring device 100 is disposed in the casing 10 and comprises a plurality of stages 190, comprising a first stage 191 to an eighth stage 198. Each stage 190 comprises a driving means in the form of a shunt 110, a first hammer 120 and a second hammer 122. A connecting means 130 (such as a connecting rod or rods) rigidly connects the first hammer 120 to the second hammer 122. The shunt 110 is an eccentric disc and hence includes a protrusion 112 which contacts the hammers 120 and 122 during use to drive them between positions. Each stage 190 in the jarring device 100 of FIG. 3 is rotated by 90 degrees with respect to its neighbouring stages 190. The jarring device 100 comprises an inner string 142 and a sleeve 144 which are co-axial shafts connected in line with the string 14. The inner string 142 is rotatable with respect to the sleeve 144 and carries the shunt 110, and the sleeve 144 carries the first hammer 120 and second hammer 122.

(13) FIGS. 4 to 6 show a single stage 190 of the jarring device 100 at sequential moments of operation as the shunt 110 is rotated in a clockwise orientation by rotation of the inner string 142 to drive the first hammer 120 and the second hammer 122 alternately.

(14) FIG. 4 shows the stage 190 of the jarring device 100 with the first hammer 120 and the second hammer 122 in their respective first positions, each spaced from the casing 10. The shunt 110 is carried and rotated by the inner string 142, and in FIG. 4 its protrusion 112 is not contacting either hammer. The sleeve 144 supports the first and second hammers 120, 122 within openings therein so that they can move back and forth when driven by the shunt 110. Both the first hammer 120 and the second hammer 122 are spaced from the casing 10 so that in the depicted case neither hammer is applying a force to the casing 10.

(15) As an aside, the depicted arrangement of FIG. 4 is the neutral, or run-in-or-out, position of the stage 190 i.e. the position used for running the jarring device 100 along the casing 10.

(16) FIG. 5 shows the stage 190 of FIG. 4 when the shunt 110 has been rotated with respect to its position in FIG. 4 so that its protrusion 112 has contacted the first hammer 120 and driven the first hammer 122 to impact the casing 10. Rotation of the shunt 110 is driven by rotation of the inner string 142. The first hammer 120 is therefore shown in its second position contacting the casing 10 in FIG. 5. The first hammer 120 is mechanically and rigidly connected to the second hammer 122 by the connecting means 130. As such, as the shunt 110 drives the first hammer 120 the second hammer 122 is also moved (to the right in the orientation shown in FIGS. 4 to 6). Therefore, the impact of the first hammer 120 with the casing 10 carries the momentum of both the first hammer 120 and the second hammer 122. Thus in the depicted case a greater impact is applied to the casing 12 than would be the case if only the first hammer 120 were driven by the shunt 110 and the second hammer 122 were stationary. Since the second hammer 122 is mechanically and rigidly connected to the first hammer 120 by the connecting means 130, the second hammer 122 has moved to a third position in FIG. 5 in which it is spaced further from the casing 10 than in its first position. It will be appreciated that any suitable connection between the first hammer 120 and the second hammer 122 may act to couple the movement of the first hammer 120 and the second hammer 122 so as to combine their momentum for impacting the casing 10 when either the first hammer 120 or the second hammer 122 is driven by the shunt 110.

(17) After the impact depicted in FIG. 5 of the first hammer 120 with the casing 10 the shunt 110 will continue to rotate in a clockwise direction (according to the orientation shown in FIGS. 4 to 6). A biasing means (shown schematically with numeral 146) urges the first hammer 120 to return to its first position in which it is spaced from the casing 10. The second hammer 122 moves synchronously with the first hammer 120, and both hammers returned to their respective first positions the same as depicted in FIG. 4.

(18) FIG. 6 shows the case when the shunt 110 is rotated so as to drive the second hammer 122 by contact with the protrusion 112 into the casing 10. Second hammer 122 thus applies an impact to the casing 10. The first hammer 120 is moved with the second hammer 122 because of the connecting means 130 therebetween. As such the impact of the second hammer 122 with the casing 10 carries the momentum of both the first hammer 120 and the second hammer 122. In the case depicted in FIG. 6 the second hammer 122 is in its second position contacting the casing 10 in the first hammer 120 is in its third position spaced further from the casing 10 than its first position.

(19) FIGS. 4 to 6 depicts a schematic arrangement in which rotation of the shunt 110 alternately drives the first hammer 120 and the second hammer 122 to impact the casing 10. The impact of the hammers 120, 122 can be sufficiently forceful to crush fill 12 surrounding the casing 10 while not being so forceful as to break the casing 12. Repeated rotation of the shunt 110 causes the hammers 120, 122 to repeatedly move back in fore and repeatedly apply impacts to opposite sides of the casing 10.

(20) Returning to FIG. 3, the jarring device 100 comprises a plurality of stages 191 to 198 each rotated by an angle of 90° with respect to its neighbouring stages. The hammers 120 and 122 of stage 191 will move left and right (in the orientation shown in FIG. 3) applying lateral forces to the left hand side and right-hand side of the casing 10. The stage 192 is oriented at 90° with respect to the stage 191 and as such the first hammer 120 and the second hammer 122 will move in use forwards and backwards (i.e. into and out of the page in the orientation shown in FIG. 3) to apply impacts to the casing 10 at an angle of 90° as compared to the impacts of the first stage 191.

(21) The third stage 193 is rotated by an angle of 90° with respect to its neighbouring stages 192 and 194. The third stage 193 is therefore aligned with the first stage 191 but is driven by its shunt 110 half a rotation out of phase. As such during use the second hammer 122 of the third stage 193 impacts the casing 10 on the right-hand side at the same time as the first hammer 120 of the first stage 191 impacts the casing 10 on the left-hand side.

(22) The fourth stage 194 is rotated by 90° with respect to the third stage 193 and is aligned with the second stage 192. The fourth stage 194 is driven half a rotation out of phase compared to the second stage 192. In the case depicted in FIG. 3 the first hammer 120 of the second stage 192 will contact the casing 10 on the reader's side of the figure (i.e. out of the page) whereas the second hammer 122 (not shown) of the fourth stage 194 will contact the casing 10 behind the jarring device 100 (i.e. into the page) in the orientation shown in the figure. The fifth to eighth stages 195 to 198 are oriented the same as the first to fourth stages 191 to 194 respectively.

(23) The jarring device 100 may therefore be used to apply lateral impacts around the inside of the casing 10. In the exemplary case shown in FIG. 3 jarring impacts are applied to the casing 10 at 90° angles around the inside. It will be appreciated that any suitable number of stages 190 may be provided in the jarring device 100 as required and further that the stages 190 may be oriented by any suitable angle with respect to each other.

(24) It will also be appreciated that the connection means 130 may be omitted from the jarring device 100 and that any suitable number of hammers may be provided per stage 190 and spaced about the shunt 110 separated by any suitable angle(s) between them.

(25) By way of example, the first hammer may have a mass of about 25 kg and may move at a speed of about 10 meters per second when driven by the shunt. This may give a non-elastic impact of 250,000 N (kgm/s.sup.2) with the casing 10. The hammer travel distance may be in the range about 30-40 mm to achieve this force. Other masses, forces and travel distances may be used and may be determined on a case-by-case basis for each wellbore and casing.