Toolstring and method for inner casing perforating, shattering annulus cement, and washing the first annulus in a second casing

Abstract

A method of sealing a partly or entirely annulus-cemented casing portion of a first casing in a second casing in a petroleum well, includes running a drill pipe string-conveyed perforating gun with a cement shattering device into said well; positioning said perforating gun at said cemented casing portion and activating first, shallow-perforating charges to make first, shallow perforations through said casing portion into thus making a perforated, cement-filled annulus portion and leaving said second casing intact; activating said cement shattering device to disintegrate all or part of said cement within said first perforated annulus portion; running a washing tool along said perforated casing portion, washing out said shattered cement from said perforated annulus portion. The washed-out casing portion may then be cut using a cutter tool and pulled out of hole, or cemented using a cementing tool, or a combination thereof.

Claims

1. A method of annulus cleaning an annulus-cemented casing portion of a first casing in a second casing in a petroleum well, comprising the steps of: running a drill pipe string-conveyed perforating gun into said well, wherein the perforation gun is run with a cement shattering device and a washing tool into said well; positioning said perforating gun at said cemented casing portion and activating first, shallow-perforating charges to make first, shallow perforations through said casing portion into a cement-filled annulus portion and leaving said second casing intact; activating said cement shattering device to provide combustion energy through said shallow perforations to disintegrate all or part of said cement within said first perforated annulus portion; and running the washing tool along said perforated casing portion, washing out all or part of said shattered cement from said perforated annulus portion.

2. The method of claim 1, further comprising the steps of: running a casing cutting tool into a portion of said perforated, washed-out casing portion, and cutting said first casing; and running a casing spear to set and hold in a top of said perforated, cut-off casing section, and pulling said cut-off casing section out of said second casing and out of hole.

3. The method of claim 1, further comprising the steps of: assembling said perforation gun with said cement shattering device first; then, assembling an automatic gun release AGR on said perforation gun; then, assembling said washing tool on said automatic gun release AGR; then, assembling a swivel on said washing tool; then, assembling a rotating casing cutter tool; then, assembling a casing spear tool; then, assembling said drill pipe string; and then, running the assembly into the well.

4. The method of claim 1, further comprising the step of: running a cementing tool and circulating in a cement slurry into at least said washed-out annulus around said perforated casing portion of said well for sealing said annulus.

5. The method of claim 4, wherein said cementing tool is said washing tool.

6. The method of claim 4, further comprising the step of: conducting said cementing via a cement stinger.

7. The method of claim 4, further comprising the step of: conducting said cementing via said wash tool, said cementing tool being said wash tool.

8. The method of claim 4, further comprising the steps of: after having washed said annulus, and optionally having circulated in spacer fluids or primer fluids, with the same wash tool, running into the well for said wash tool acting as a cementing tool to isolate lower perforations of said perforated casing section; circulating cement slurry through said perforations into said annulus and cementing said annulus, allowing return fluid with displaced wash fluid or other fluids such as spacer or primer fluids from said annulus through perforations above said cementing/wash tool back into the casing bore above the wash tool; and pulling said cementing/wash tool upwardly while cementing, an entire length of said perforated section's annulus, while circulating out wash fluid or other fluids via the first casing.

9. The method of claim 8, further comprising the step of: allowing cement slurry returning from the annulus being cemented back through perforations above said wash tool to pass downwardly through a bypass channel through said wash tool to allow cementing the casing bore below the wash tool as it is being pulled upwardly during the annulus cementing process.

10. The method of claim 1, wherein after activating said first shallow perforating charges of said perforation gun, displacing said annulus cement shattering device to a position adjacent to said perforations within said perforated casing portion, before said activation of said annulus cement shattering device.

11. The method of claim 1, said annulus cement shattering device comprising a second gun with slower-burning charges detonating in part via said first perforations into said perforated casing portion's annulus.

12. The method of claim 1, wherein said perforating gun and said annulus cement shattering device are combined on the same drill pipe string, with said shattering device below said perforating gun.

13. The method of claim 12, wherein after the step of perforating using the first perforation gun and forming first perforations at perforated casing section: an ignition cord of said first perforation gun activating a delay timer trigger device; pulling outwardly to place said annulus cement shattering device within said perforated casing section, within a delay time given by said delay timer trigger device; and said delay timer trigger device triggering said shattering device.

14. The method of claim 1, further comprising the steps of: using a perforation gun and cement shattering device arranged along a same length of a common stem; and after activating said first, shallow perforating charges of said perforation gun, activating said annulus cement shattering device along the same length of perforations of said perforated casing portion.

15. The method of claim 14, wherein for activating said annulus shattering device, using a said shatter tool with slow-burning higher-energy charges arranged as a cylindrical sleeve around said perforation gun's perimeter, covering and arranged to be broken up into fragments for being displaced partly through said perforations and ignited by said first, shallow-penetrating charges.

16. The method of claim 1, wherein for activating said annulus shattering device, using a said shatter tool with slower-burning higher-energy charges arranged as a series of single charges arranged interleaving with said first, shallow-perforating charges within said perforation gun's perimeter, and ignited with a short delay after said first, shallow-penetrating charges.

17. The method of claim 16, further comprising the step of: arranging said single charges in the form of tablets interleavingly arranged between said first shallow-penetrating charges and arranged for being set off by the energy released by said first charges.

18. The method of claim 1, further comprising the step of: using a wash fluid while washing out said shattered cement from said perforated annulus portion, and subsequently using the same wash tool circulating in a spacer fluid into said washed-out perforated annulus portion to prepare the washed-out annulus portion for cementing.

19. The method of claim 1, further comprising the step of: arranging said wash tool above said first perforation gun.

20. The method of claim 1, further comprising the steps of: after having detonated said annulus cement shattering device, running into the well for said wash tool to isolate upper or near-upper perforations of said perforated casing section; normal circulating wash fluid through said perforations into said annulus and washing said annulus, allowing return fluid with washed-out cement and other debris from said annulus through perforations above said wash tool or via perforations below said wash tool and return via a bypass channel through said wash tool; and running downwardly while washing an entire length of said perforated section's annulus, while circulating out disintegrated cement particles and other debris within the first casing.

21. The method of claim 1, wherein said perforation gun, shattering tool, and washing tool are combined in one common tool string.

22. The method of claim 1, further comprising the step of: using an automatic gun release sub and disconnecting and dropping said shatter tool after having detonated it.

23. The method of claim 1, further comprising the step of: disconnecting and dropping said shatter tool and said perforation gun after having detonated said shatter tool.

24. A casing annulus cleaning tool string comprising: a drill pipe string with: a conveyed perforation gun; and a cement shattering device, wherein both the perforation gun and the cement shattering device are arranged near said drill pipe string's lower end, for being lowered into a casing with an annulus cemented casing portion about said casing in a petroleum well, wherein said perforating gun is arranged with: first, shallow-perforating charges for shooting first, shallow perforations through said casing portion into a first annulus, said shallow-perforating charges arranged for leaving a surrounding second casing intact; wherein said shattering device is arranged for being activated after said shallow-perforating charges to provide combustion energy through said shallow perforations to disintegrate all or part of said cement within said first perforated annulus, and wherein a washing tool is arranged above said perforation gun and cement shattering device on said drill pipe string, said washing tool for washing out said shattered cement from said annulus.

25. The casing annulus cleaning tool of claim 24, further comprising: a casing cutting tool arranged for cutting said first casing; a casing spear arranged to set and hold in a top of said perforated, cut-off casing section, and adapted for pulling said cut-off casing section out of said second casing and out of hole.

26. The casing annulus cleaning tool of claim 24, further comprising: an automatic gun release AGR on said perforation gun with said cement shattering device; said wash tool on said AGR; a swivel on said wash tool; a rotating casing cutter tool; a casing spear tool; and then said drill pipe string.

27. The casing annulus cleaning tool string of claim 24, wherein said washing tool is arranged for circulating in a cement slurry into said washed-out annulus and arranged for sealing said annulus.

28. The casing annulus cleaning tool string of claim 24, wherein said perforation gun and said annulus cement shattering device arranged consecutively, one above the other, wherein said perforation gun is arranged for being triggered first, and wherein said cement shattering device is arranged for subsequentially being displaced to a position adjacent to the firing position, i.e. the perforations of said perforation gun in said perforated casing section, before activation of said annulus cement shattering device.

29. The casing annulus cleaning tool string of claim 24, said annulus cement shattering device comprising a second gun with slower-burning charges arranged for detonating in part via said first perforations into said perforated casing portion's annulus.

30. The casing annulus cleaning tool string of claim 24, wherein said perforating gun and said annulus cement shattering device are combined on a same drill pipe string, with said shattering device below said perforating gun.

31. The casing annulus cleaning tool string of claim 24, comprising: an ignition cord of said first perforation gun activating a delay timer trigger device arranged for starting a delay time for pulling outwardly to displace said annulus cement shattering device to within said perforated casing section before triggering said shattering device.

32. The casing annulus cleaning tool string of claim 24, wherein said perforation gun and cement shattering device are arranged along the same length of a common stem, and wherein said perforation gun is arranged for firing said first, shallow perforating charges first, making perforations, said annulus cement shattering device arranged for firing subsequently along a same length of perforations of said perforated casing portion.

33. The casing annulus sealing tool string of claim 24, said annulus shattering device comprising slower-burning higher-energy charges as compared with said first charges, said slower-burning higher-energy charges arranged as a cylindrical sleeve around said perforation gun's perimeter, covering said first charges, and arranged to be broken up into fragments by, and partly displaced through said perforations, and to be ignited by said first, shallow-penetrating charges.

34. The casing annulus sealing tool string of claim 24, for activating said annulus shattering device, using a said shatter tool with slow-burning higher-energy charges arranged as a series of single charges arranged interleaving with said first, shallow-perforating charges within said perforation gun's perimeter, and for being ignited with a short delay after said first, shallow-penetrating charges.

35. The casing annulus sealing tool string of claim 24, wherein said wash tool is arranged above said first perforation gun.

36. The casing annulus sealing tool string of claim 24, having the instrument sequence of: a shattering tool at the bottom of the string; a perforation gun above said shattering tool or combined with said shattering tool; and a washing tool, with bypass channels, above said perforation gun.

37. The casing annulus sealing tool string of claim 24, an automatic gun release on said shatter tool and or perforation gun disconnectable upon firing of said shatter tool.

Description

FIGURE CAPTIONS

(1) The attached figures illustrate some embodiments of the claimed invention.

(2) FIG. 1 illustrates a well with a first and a second casing (C1, C2), wherein the first casing (C1) is cemented (101) or otherwise fixed in part of or all of the first annulus (A1) along a part (C10A) outside a casing portion (C10) of the first casing's (C1) extent. The first casing (C1) is surrounded along part or all of its length by said second casing (C2). The casing (C1) annulus (C10A) shall according to the invention be cleaned out of the previous partial or complete cement and sealed with new cement, without damaging the second casing or its surrounding second annulus cement.

(3) FIG. 2a is an illustration of the perforation gun (1) firing through a desired section; casing portion (C10) of the first casing (C1), while leaving the second casing (C2) generally intact.

(4) FIG. 2a further shows:

(5) Perforation gun (1) firing making first perforations (12) into first annulus (C10A) Separate perf. gun and shatter gun Casing section (C10) now being perforated

(6) FIG. 2b is an illustration of an embodiment of the invention wherein the perforation gun (1) is combined with a shattering tool (2); the perforation gun (1) fires and makes perforations (12) through the wall of the first casing (C1) making a perforated casing portion (C10). In the embodiment illustrated it fires through the shattering tool (2) portion of the combined tool, a cylindrical sleeve (211), and brings along second charge fragments (21F) from the cylindrical sleeve (211) through the perforations (12).

(7) Further FIG. 2b shows:

(8) C10 casing section now being perforated Perforation gun (1) making first perforations (12) into first annulus Combined perf gun and shatter gun

(9) FIG. 3a is an illustration of a shatterer device (2), in the embodiment of a second gun (20), has been pulled upwardly to the perforated casing section (C10). The second gun (20) is triggered. This incurs shattering of the first annulus' (C10A) cement (101), and partially releases the cement from the inner and outer casings (C1, C2). Please also see FIG. 10.

(10) Further FIG. 3a shows:

(11) shatter gun displaced and given delayed activation C10 perforated casing section now cemented in first annulus (C10A) now being shattered

(12) FIG. 3b is an illustration of a shatterer device (2) in the embodiment of a combined perforation gun (2) with a second charge (211) being ignited by the perforation charges and creates charge fragments (21F) which generate heat in the first annulus (C10A) and within the casing. Please also see FIG. 13.

(13) Further FIG. 3b shows

(14) Shatter gun triggered by perforation gun Shatter device (2), combined first and second gun firing second layers (211) charge fragments (21F) into annulus (C10A) for combustion C10 perforated casing section now cemented in first annulus (C10A) now being shattered

(15) FIG. 4 illustrates the tool string with the washing tool (3) run further into the casing so as for aligning the wash tool (3) with the perforated, annulus cement shattered casing section (C10). The wash tool (3) is aligned with the upper portion of the perforated casing section (10), and washes out the annulus (C10A) while being moved downwardly towards the bottom of the perforated casing section. This effectively removes shattered cement debris from the annulus (C10A) and thus prepares the annulus for being cemented. Before the washing step shown in FIG. 4, the perforation and/or shattering tool (1, 2) tool may be disconnected from the washing tool (3) using an ordinary ball-release sub below the washing tool (3) and the perforation tool (1). This is advantageous both due to operational safety, personal safety, and operation of ease.

(16) Further FIG. 4 shows:

(17) Washing downwardly C10 perforated casing section's annulus (C10A) now being washed out

(18) FIG. 5 illustrates the resulting washed-out annulus (C10A) along the perforated casing section (C10).

(19) Further FIG. 5 shows

(20) Washing downwardly finishing Wash fluid normalcirculated through drill pipe string and out via wash tool (3) wash tool (3) normalcirculating and washing annulus C10A top down with wash fluid C10 perforated casing section annulus (C10A) now being washed top down

(21) FIG. 6a shows the generally washed-out casing section (C10) annulus engaged the swab cups of the wash tool (3) near the lower perforations, while cement slurry is being pumped down via the conveying drill pipe string, out between the swab cups, and circulated without excessive force out into the washed-out, preferably spacer fluid primed annulus (C10A) lower portion. Excess cement re-entering above the wash tool may be by-passed down through a bypass channel in the wash tool in order to allow moving the wash tool upwardly while cementing.

(22) FIG. 6a further shows:

(23) Start cementing using wash tool Cement slurry circulated through drill pipe string and out via wash tool (3) Wash tool (3) circulating in cement to annulus (C10A) bottom up C10 perforated casing section annulus C10A now being cemented bottom up Option: gun (1) and shatter tool (2) disconnected after activation of shatter tool (2)

(24) FIG. 6b illustrates the wash tool having cemented the entire annulus up to the upper portion of the washed-out, now cement slurry filled annulus (C10A). The illustrated length of perforated, washed-out, now cement slurry filled annulus (C10A) is far longer in reality than illustrated here and may be 50 metres or more in order to provide a regulatory required length of cement sealed annulus.

(25) FIG. 6b further shows:

(26) Cementing bottoms up Wash tool (3) injecting cement into washed annulus C10 perforated casing section's annulus now washed out

(27) FIG. 6c illustrates an embodiment wherein after washing out the annulus (C10A), the casing cutter tool (5) is activated and rotates to cut off the casing (C1) without cutting the second casing (C2). The cut is made in the washed-free casing section (C10) which should now be free of cement in the annulus (C10A). The cut may be made after the step of FIG. 6b wherein a cement plug is formed across part of the washed-out annulus (C10A) below the cut to be made, or conducted without any cement plug.

(28) FIG. 6c further shows:

(29) Cutting the washed-out casing section subsequent to FIG. 5 or FIG. 6b Cutter tool (5) cutting the washed-out casing section C10 perforated casing section annulus C10A casing now being cut

(30) FIG. 6d illustrates the further step after the cut is made in FIG. 6c, wherein the casing spear (6) has been moved to an upper portion of the cut-off section of casing (C1), and pulled out of hole.

(31) FIG. 6d further shows:

(32) Pulling severed-off casing section out of hole C10 perforated casing section's annulus (C10A) now washed out and section cut

(33) FIG. 7 illustrates the resulting plug sealing the annulus and the casing bore. If required for plugging wall-to-wall within the second casing, the cement slurry also in the casing bore may allow to settle and harden so as for plugging and abandoning the well below the plug. If required for sealing only the annulus, the cement slurry in the casing bore may be circulated out of the casing bore, (usually with reverse circulating).

(34) FIG. 7 further shows:

(35) Cement plug formed Wash tool (3) having formed cement plug

(36) FIG. 8 is, in the upper half, FIG. 8a, an illustration of a cross section of the first perforation gun (1) perforating shallowly and only through the first casing (C1), leaving the second casing (C2) generally intact. In the lower half, please see FIG. 8b, is illustrated the same position along the well, the same part of the perforated section (C10) wherein is fired the higher-energy slow-burning charges (21) of the shatterer device (2), the second gun (20). The result is illustrated in FIG. 10 below.

(37) FIG. 8c illustrates the same vertical sections of the same perforation gun (1) and shatterer device (2) with very short delay. The upper part illustrates an embodiment of the perforation gun (1) combined with a shatterer device (2) constituting one combined perforation and shatterer tool (1, 2), wherein the perforation gun fires shallow perforations (12) through the first casing (C1), and carries fragments (21F) of a second charge (21) through the perforations (12) and into the first annulus (A1). In the lower part is illustrated the same tool section a few milliseconds later, the situation after the perforation charges have set off, wherein the slower-burning charges 21F have spread, and ignite and combust.

(38) FIG. 8c further shows:

(39) Combined tool (1, 2) with slow-burning charges (21) ignited by perforation charges (20). Upper part: firing of perforation charges (20), and lower part: same tool section after perforation charges set off; later stage wherein the slow-burning charges (21F) spread, ignite, and combust.

(40) FIG. 9 is a photographic image of an ordinarily perforated dual casing with cement (101) inbetween, the inner casing removed after perforation and splitting away of half of the dual casing.

(41) FIG. 9 further shows:

(42) A laboratory test of a dual casing perforated using a conventional circulation gun (shooting holes through inner casing (C1), cement (101), second casing (C2). The inner casing (C1) has been removed from the shot assembly and it is seen that the first annulus cement (101) is intact between the holes.

(43) FIG. 10 is a photographic image of a perforated and shattered cement according to the invention.

(44) FIG. 10 further shows:

(45) Dual casing perforated and treated according to the present invention: Shallow perforations through inner casing (C1), and shot using second, slow-burning, energy rich charges which have broken up the first cement (101) between the perforation holes. We see that the cement is broken up and easily disintegrates.

(46) FIG. 11 is also a photographic image corresponding to FIG. 10, with the shattered cement picked away and removed from the annulus within the second casing.

(47) FIG. 11 further shows:

(48) Having removed the inner casing (C1) (for demonstrating the effect) from the annulus cement (101) broken up according to the invention: The cement is easily plucked away. This shows that a wash tool in the casing (1) may easily wash out the broken up cement (101) in the annulus (C10A)

(49) FIG. 12 illustrates an embodiment of the invention wherein the perforation gun and the shattering gun are combined in one common gun tool (1, 2), and further combined with a wash tool above, and a drill pipe string (0). Also shown is the embodiment wherein there is further included a swivel (3S), a casing cutter tool (5), and a casing stinger (6).

(50) FIG. 13 shows an embodiment of the invention also illustrated with details in FIG. 8c, and which is also illustrated in use in FIG. 3b. In this embodiment, said shatter tool's (2) slow-burning higher-energy charges (21) is arranged as a sleeve-shaped layer outside on and in combination with said perforation gun's (1) shallow-penetrating charges (11). In an embodiment a wash tool (3) is combined with this combined perforation and shatter tool (1, 2) and the entire tool is arranged for being run on a drill pipe string (0).

EMBODIMENTS OF THE INVENTION

(51) The invention will in the following be described and embodiments of the invention will be explained with reference to the accompanying drawings.

(52) The invention is a method of cleaning an annuluscemented (102) casing portion (C10) of a first casing (C1) in a second casing (C2) in a petroleum well, comprising the steps of: running a drill pipe string (0)conveyed perforating gun (1) with a annulus cement shattering device (2) into said well; positioning said perforating gun (1) at said cemented casing portion (C10) and activating first, shallow-perforating charges (11) to make first, shallow perforations (12) through said casing portion (C10) into thus making a perforated, cement-filled annulus portion (C10A) and leaving said second casing (C2) intact; activating said annulus cement shattering device (2, 20) to disintegrate all or part of said cement (102) within said first perforated annulus portion (C10A); running a washing tool (3) along said perforated casing portion (C10), washing out said shattered cement (102) from said perforated annulus portion (C10A).

(53) In an embodiment of the invention the method further comprises running a casing cutting tool (5) into a portion of said perforated, washed-out casing portion (C10A), and cutting said first casing (C1); running a casing spear (6) to set and hold in preferably a top of said perforated, cut-off casing section (C1, C10A), and pulling said cut-off casing section (C1, C10A) out of said second casing (C2) and out of hole.

(54) We may then achieve to remove the inner casing (C1) which was cement-stuck fixed in the second casing (C2), in case the inner casing shall be removed, or replaced with a new casing, or if a sidestep shall be conducted, also in case a cement plug shall be formed before pulling out the inner, previously stuck casing.

(55) The present invention is highly advantageous over prior art which is not capable of perforating the inner casing only and shattering only the cement in the inner casing's annulus without damaging the second casing. Prior art such as US2003/0037692 Liu fires charges indiscriminately through the casing, through cement, and far into the surrounding geological formation and injects sluminium powder to burn out the deep rock perforations, and to react with water in the formation to further combust. US2007/0095529 Bond describes shaped charges that forces oxygen-rich material into deep rock perforations to combust with oil in the geological formations. The present invention provides a far gentler method of penetrating only the first, inner casing, and uses secondary igniting charges to slower-acting shattering of the annular cement material without damaging the second casing. Thereby, the first casing may be washed free from its annulus, and may be cut and pulled.

(56) In a further embodiment of the invention the method comprises assembling said perforation gun (1) with said cement shattering device (2) first, then assembling the AGR (8) on said perforation gun (1), then assembling said wash tool (3) on said AGR (8); then mounting a swivel (3S) which allows rotation of the toolstring above the wash tool, which should not be rotated due to the rubber cups; then we mount a rotating cutter tool (5) on the swivel, and then said casing spear tool (6); and then said drill pipe string (0) which is used for running into the well.

(57) The casing spear tool (6) is advantageously in an embodiment arranged at the top of the toolstring BHA in order to have a good tensile strength margin throughout the DP string (0) and the casing spear tool (6) in order to pull out the casing. The washing tool (3), the swivel (3S), and the cutter tool (5) may in an embodiment of the invention be removed from the toolstring before engaging the casing stinger (6) in the top of the cut-off casing section to be pulled, in order to facilitate the tripping out. The AGR (8) has dropped the guns (2) after firing, anyway, we don't want misfired gun charges to the deck.

(58) In an embodiment of the invention, we run a cementing tool (7) and circulate in cement slurry (c) into at least said washed-out annulus (C10A) around said perforated casing portion (C10) of said well for sealing said annulus (C10A). This is done before a cut and pull operation described above, or instead of a cut and pull operation if the purpose is just to cement the first annulus between the inner and second casing (C1, C2).

(59) The annulus cement shattering device (2, 20) may in one embodiment be a tool arranged separate from and below the perforation tool (1), please see FIG. 2a, FIG. 3a, FIG. 4, FIG. 5, FIG. 8a, and FIG. 8b, and thus has to be displaced to the perforations (12) made by the perforating tool (1) before the annulus shattering device (2) is activated, such as defined in claims 2, 3, 4, and 5.

(60) The annulus cement shattering device (2) may in another embodiment be a tool extending along the same portion along the stem of the perforation tool (1) itself. The annulus cement shattering device (2, 20) may thus be embodied together with the perforation tool (1) and used such as defined in claims 6, 7, 8, and 9, please see FIG. 2b, FIG. 3b, FIG. 8c, FIG. 12, and FIG. 13. In this case, the shattering tool (2) may have a brief delay of being activated after the firing of the perforation tool (1) in order to utilize the perforations (12) formed by the perforation tool (1), for burning out the perforations but also the annulus (C10A) outside the perforations.

(61) The material in the annulus (C10A) be old, hardened cement, but not necessarily cement; it may also comprise compacted debris, clay, and other particles which seal the first casing annulus in the borehole or in a subsequent casing so that it may not easily be perforated, washed and pulled, or perforated, washed and sealed, either for replacement pulling, or plug and abandon, or for sealing an annulus leakage. Not all the annulus length (C10A) may necessarily comprise old cement or similar material preventing a good wash-out of the annulus, only part may be blocking. Anyway, the old cement must be shattered, disintegrated and washed out before freeing the casing for cutting and pulling, or new cement slurry is circulated in to form a proper seal of required length. The perforated and washed-out casing portion (C10) of the inner casing (C1) may comprise a non-perforated part of any length above the perforated section (C10).

(62) The length of the perforation gun (1) may be 50 to 100 metres or more, assembled screwed together from gun sections of lengths 6 m, 9 m, or other lengths. The length of the desired casing portion (C10) to be perforated depends on the length of the cemented annulus to be cut and pulled, or the length of the cemented annulus to be sealed properly, a length of 50 m or more, which may be more than previously existing zonal isolation lengths.

(63) The length of the assembled shattering device (2) will most preferably be of the same length, particularly if it is assembled along the same stem length, as the assembled perforation gun itself. Having such extensive lengths of perforation gun and shattering device allows long lengths of casing to be perforated, shattered, washed-out, and cemented in one single trip.

(64) FIG. 1 illustrates a well with a first and a second casing (C1, C2), wherein the first casing (C1) is cemented (101) with existing cement in the first annulus (A1) along a part (C10A) outside a casing portion (C10) of the first casing's (C1) extent. The purpose is to free the first casing (C1) from a second casing (C2) in order to pull it out of hole. Alternatively, the purpose is to cement the first casing portion (C10) of the casing (C1) and to leave the second casing (C2) and its second annulus cement (102) or other fill, if present, intact as far as practical to achieve. The second casing may be cemented (102) in what is called the second annulus (A2) to the borehole wall (B0) as illustrated, or to a third casing on the outside of the second casing. In the present method it is desirable not to affect the second annulus but leave the second casing (C2) and its annulus cement (102) intact, regardless of whether we pull the first casing (C1) or we plug the first casing (C1) and its annulus

(65) The inner casing may be a 9 pipe having a wall thickness of 15 mm or more. The second, outer casing may be a 13 pipe having a similar wall thickness. Other casing dimensions may of course apply. In any way, the first and second casings (C1, C2) constitute part of the context of the present invention.

(66) FIG. 2a is an illustration of the perforation gun (1) firing through a desired section, a casing portion (C10) of the first casing (C1), while leaving the second casing (C2) intact with only minor scratches. Short-focus charges in the perforation gun (1) have the property of punching perforation holes through the first casing wall, and not through the second casing (C2) wall, which is left intact. But due to the perforations' relatively small charge and being geometrically focussed, only relatively narrow holes are made with short range, extending only into the concrete in the annulus (C10A); no major shattering of the first annulus cement (101) occurs. This is also visible from FIG. 10 wherein the inner casing from the split-up test setup has been removed for observing the cement status; the perforations punch a relatively small hole in the cement. So a major proportion of the so perforated casing section (C10) of the casing (C1) may remain fixed to the remaining, intact cement (101) and thus still be stuck to the cement (101) and to the second casing (C2), thus forming in a real well an obstacle to annulus washing of that part of the perforated casing.

(67) In an embodiment of the invention, the cement shattering device (2) comprises a second gun (20) with delayed, slow-burning charges (21) detonating in part via said first perforations into said perforated casing portion's (C10) annulus (C10A). In an embodiment of the invention, the perforating gun (1) (above) and said cement shattering device (2) (below) are combined on the same drill pipe string (0), please se FIGS. 2a and 3a. FIG. 3a is an illustration of a shatterer device (2), in the embodiment of a second gun (20), having been pulled upwardly to the perforated casing section (C10). The length of the second gun (20) may be the same as the length of the first perforation gun (1). The second gun (20) may be triggered by a delay timer (22) initiated by the firing of the first perforation gun. The second gun (20) fires slower burning charges (21, 21s) (please see FIG. 3a and FIG. 8b which are also of higher energy than the first short-focus charges (11). It is not necessarily a perforation gun as such, as it fires/combusts and the fire gases are pressed into and through existing perforations. This incurs a shock wave and thermal energy which in combination results in shattering of the first annulus' (C10A) cement (101) and shatters and burns it out, and partially releases the cement from the inner and outer casings (C1, C2). Please also see the result in FIG. 10, wherein in FIG. 10 the inner casing (C1) (removed) of a dual casing is perforated and treated according to the present invention: Shallow perforations through inner casing (C1), and shattered using second, slow-burning, energy rich charges which have broken up the first cement (101) between the perforation holes. We observe that the cement is broken up and easily disintegrates.

(68) So in an embodiment of the invention, after step (a) perforating using the first perforation gun (1) and forming first perforations at perforated casing section (C10); the following is conducted: activating a delay timer trigger device (22), pulling outwardly to place said shattering device (2) within said perforated casing section (C10); allowing said delay timer trigger device (22) to trigger said shattering device (2), shattering the annulus cement.

(69) This procedure using the delay timer trigger device (22) allows a certain time to activate the second gun (2), a delay which allows the pulling up to relocate the second gun (2) to where the first perforation gun (1) was fired.

(70) In an embodiment of the invention, the perforation gun (1) and the shattering device (2) are combined in the same section of the tool, please see FIG. 8c.

(71) In an embodiment of the invention shown in FIG. 4, one may arrange the wash tool (3) above said first perforation gun (1). Further, in an embodiment of the invention, after having detonated said shattering device (2), one may conduct: running into hole for said wash tool (3) to isolate upper perforations of said perforated casing section (10), normal circulating wash fluid through said perforations into said annulus (C10A), allowing return fluid from said annulus (C10A) through perforations above said wash tool (3), running downwardly while washing preferably the entire length of said perforated section's (C10) annulus (C10A), while circulating out cement and other debris within the first casing (C1). Please see FIGS. 4 and 5 below. An advantage of starting washing from the top of the perforated section (C10) is that one will only wash out debris from an upper part of the shattered annulus (C10A) cement debris initially, and may control the wash tool displacement speed downwardly according to how much cement debris is in suspension in the return flow at any time, a feature which is less controllable if one starts washing bottoms up of the shattered annulus, whereby one would run the risk of trying to lift too much debris at a time, risking blocking the wash tool from being pulled up in the casing.

(72) FIG. 4 illustrates the tool string with the washing tool (3) run further into the casing so as for aligning the wash tool (3) with the perforated, annulus cement shattered casing section (C10). In a preferred embodiment of the invention the wash tool (3) is aligned with the upper portion of the perforated casing section (10), and washes out the annulus (C10A) while being run downwardly towards the bottom of the perforated casing section. This effectively removes shattered cement debris from the annulus (C10A) and thus clears the annulus (C10A) between the inner casing (C1) from the outer casing (C2).

(73) FIG. 5 illustrates the resulting washed-out annulus (C10A) along the perforated casing section (C10). Here we have illustrated only a short cemented section; the perforating and shattering tools (1, 2) may have been used along a length of the casing section (C1) longer than the perforating and shattering tools (1, 2), which may have been fired multiple times with relocation of the tools for each firing, but the washing process using the wash tool may be done in one continuous sequence while pumping from the surface through the drill pipe string (and possibly through a casing stinger and vibrator).

(74) Further, in an embodiment of the invention, the tool sequence may be as follows, please see FIG. 6: combining in sequence as illustrated in the attached drawings: shattering tool (2) at the bottom of the string, said perforation gun (1) above it, or integrated with the shattering tool, the washing tool (3), preferably with bypass channels, above the perforation gun. The washing tool may be arranged with a through bore for supplying the wash tool with wash fluid, and with a ball passage for triggering the perforation gun (1), and requiring another ball diameter for closing the wash tool (3) in the bottom to direct the wash fluids, namely wash fluid, then spacer fluid, then cement slurry.

(75) FIG. 6a shows the generally washed-out casing section (C10) annulus engaged the swab cups of the wash tool (3) near the lower perforations, while cement slurry is being pumped down via the conveying drill pipe string, out between the swab cups, and circulated without excessive force out into the washed-out, preferably spacer fluid primed annulus (C10A) lower portion. Excess cement re-entering above the wash tool may be by-passed down through a bypass channel in the wash tool in order to allow moving the wash tool upwardly while cementing.

(76) FIG. 6b illustrates the wash tool having cemented the entire annulus up to the upper portion of the washed-out, now cement slurry filled annulus (C10A). The illustrated length of perforated, washed-out, now cement slurry filled annulus (C10A) is far longer in reality than illustrated here and may be 50 metres or more in order to provide a regulatory required length of cement sealed annulus.

(77) FIG. 6c illustrates an embodiment wherein after washing out the annulus (C10A), a casing cutter tool (5) is activated and rotates to cut off the casing (C1) without cutting the second casing (C2). The cut is made in the washed-free casing section (C10) which should now be free of cement in the annulus (C10A). The cut may be made after the step of FIG. 6b wherein a cement plug is formed across part of the washed-out annulus (C10A) below the cut to be made, or conducted without any cement plug.

(78) FIG. 6d illustrates the further step after the cut is made in FIG. 6c, wherein a casing spear (6) has been moved to an upper portion of the cut-off section of casing (C1), and pulled out of hole.

(79) Advantageously the perforation gun (1) is dropped after firing of the shattering device (2). An advantage of dropping the perforation gun (2) and the shattering device (2) is threefold: a) there will then be no perforation guns or shattering tools to retrieve and disconnect section by section on deck after the pulling out of the drill pipe string and the wash tool (3) after the cementing operation is done. Rig time is saved. b) There will be no health safety risk from misfired guns or shattering tools upon disconnecting section by section; only the wash tool is retrieved on surface. c) the guns and shattering tools are disposed of in a lower section of the well such as the rathole below the plugged casing section, if possible, thus not requiring transport away from the platform and subsequent recycling of such potentially hazardous material.

(80) FIG. 7 illustrates the perforated, washed-out section (C10) now plug cemented.

(81) FIG. 8 is, in the upper half, FIG. 8a, an illustration of a cross section of the first perforation gun (1) perforating shallowly and only through the first casing (C1), leaving the second casing (C2) generally intact, usually with only minor radial deformation just outside the perforations formed. The shallow range perforation charges (11) are focussed onto the proximal casing wall (C1), and do not focus on, nor perforating the second casing wall (C2). In the lower half, please see FIG. 8b, is illustrated the same position of the casing along the well, the same part of the perforated section (C10) wherein is fired the higher-energy slow-burning charges (21) of the shatterer device (2), the second gun (20). The slower-burning charges partly burn into the perforations and further from the perforations into first annulus (C10A) with its cement (101) and cracks it and disintegrates the cement into smaller pieces and also burns around the pieces and also opens up along the cement (101)/casing (C1, C2) interface. The result is illustrated in FIG. 10 below. FIG. 8c illustrates an embodiment of the perforation gun (1) combined with a shatterer device (2) constituting one combined perforation and shatterer tool (1, 2). In this embodiment of the invention, the shallow-range perforation charges (11) are triggered, usually by a common ignition cord (111), and perforate, shatter and ignite a surrounding layer comprising a second, slower burning explosive charge (21). The second charge (21) may comprise a cylindrical layer (211) which is fragmented into charge fragments (21F), please see the upper part of FIG. 8c. The charge fragments (21F) are partly brought along by the firing of the perforation charges (11) and brought out through the perforations (12) and end up in the annulus (A1). Partly, they remain as a partly or entirely shattered cylindrical layer (211) on the perforation gun. In the lower part of FIG. 8c, it is illustrated that those fragments (21F) have been ignited by the energy release of the firing perforation charges (11) and burn slower, but release more energy than the perforation charges (11), into the cemented, now partly cracked up first annulus (A1). The energy release of the charge fragments (21F) further cracks up and disintegrates the cement in the first annulus and partly or entirely releases the cement from the first and second casing. The energy released from the now fragmented layer (211) within the first casing (C1) in the tool's annulus will also contribute to the cracking up of the annular cement in the first annulus (A1).

(82) FIG. 9 is a photographic image with a laboratory experiment having run a perforation gun (1) of an ordinarily perforated dual casing (C1, C2) with cement (101) inbetween, the image showing the inner casing (C1) having been removed after perforation and splitting away of half of the dual casing. It is seen that the annulus cement (101) is intact after shooting and removal of the inner casing. Such a shot casing would not be possible to annulus-cement because the cement is still generally intact between the perforations and is not easily washed out as it is too compact and fluid proof between the holes punched.

(83) FIG. 10 is a photographic image of a perforated and shattered cement according to the invention, here shown in a split outer casing, with the inner casing removed. It is seen that the cement is shattered and disintegrated. The dual casing (C1, C2, and cement (101) is treated according to the present invention: Shallow perforations through inner casing (C1), and the annulus cement (101) shattered using second, slow-burning, energy rich charges which have broken up and disintegrated the first cement (101) between the perforation holes. We see that when the perforated inner casing (C1) is removed from the split setup, the cement is shattered broken up and easily disintegrates. This cement is feasibly washed out using standard wash tool techniques described in relation to FIG. 4 and FIG. 5.

(84) FIG. 11 is also a photographic image corresponding to FIG. 10, with the shattered cement picked away and removed from the annulus within the second casing. One will see that the perforations do not extend through the second casing. The removal of the shattered cement as conducted in this image is a purely mechanical removal which may be done by hand in the situation shown in the picture of FIG. 11, but the corresponding wash-out step as shown in FIGS. 4 and 5 is done using a high pressure wash tool (3). The washing-out procedure may use a washing pressure of up to 1000 Bar or more on the drill pipe string holding the wash tool.

(85) In an embodiment of the invention, one may conduct a disconnecting and dropping procedure of said shatter tool (2) after having detonated it. Such Further, one may conduct disconnecting and dropping of said shatter tool (2) and said perforation gun (1) after having detonated said shatter tool (2), as they are most preferably not retrieved to the surface after firing. This is a safety precaution in case one or more of the charges should have misfired, which has proven highly dangerous when such misfired charges fire on deck.

(86) In an embodiment of the invention, one may arrange said shatter tool's (2) slow-burning higher-energy charges (21) in combination with said perforation gun's (1) shallow-penetrating charges (11) in one common stem, preferably interleavingly, and arranged for firing them in sequence, first, the shallow punching charges (11), then the shattering charges (21) with a slight delay so as for the punching charges (11) to have penetrated the inner casing. Please see FIG. 12.

(87) In an embodiment of the invention, one may arrange said shatter tool's (2) slow-burning higher-energy charges (21) in combination with said perforation gun's (1) shallow-penetrating charges (11), please see FIG. 13, in one common stem as discussed under FIG. 8c. In an embodiment of the invention, for activating said annulus shattering device (2, 20), one may use a said shatter tool (2) with slow-burning higher-energy charges (21) arranged as a series of single charges (21, 113), please see FIG. 8c, said single charges (113) arranged interleaving with said first, shallow-perforating charges (11) within said perforation gun's (1) perimeter, and ignited with a short delay after said first, shallow-penetrating charges (11). The single charges (21, 113) in the form of tablets (113) interleavingly arranged between said first shallow-penetrating charges (11) and arranged for being set off by the energy released by said first charges (11). The perforating charges are arranged in the tool stem and fire through a cylindrical surrounding layer of a second charge (211) which is slower-burning, but has a higher combustion energy than the perforation charges (11). The second charge (211) disintegrates into second charge fragments (21F) which are brought through the perforations (12) through the first casing (C1) and combust to shatter and disintegrate the annular cement between the first and second casings (C1, C2). In such an embodiment, there is no need for any delay firing device.

(88) TABLE-US-00001 Components list 0 drill pipe string (0) 1 dp conveyed perforation gun (1) 2 cement shattering device (2) 20 cement shattering device (20) 11 shallow-perforating charges (11) 12 first, shallow perforations (12) in cement-filled casing portion (C10) 3 annulus washing tool (3) 3S swivel (3S) 5 casing cutter tool (5) 6 casing spear (6) 7 cementing tool (7) (which may be the washing tool (3)) 8 Automatic Gun Release (8) 102 cement (102) in cement-filled casing portion (C10) C10 cement-filled casing portion (C10) C1 casing (C1) C10A first washed-out annulus (C10A) C2 second casing (C2) to remain intact