Abstract
A method is for testing the pressure integrity of a barrier in an annulus outside a pipe string in a wellbore, the method including the steps of: establishing a fluid connection between an inside of the pipe string and an annulus out-side the pipe string at a first position and second positions in the wellbore, the second position being offset from the first position along the axial direction of the wellbore; establishing a temporary barrier between the fluid connections at the first and second positions in the wellbore; establishing a pressure differential across the temporary barrier; releasing a tracer from below the temporary barrier; and sniffing for tracer above the temporary barrier to verify a leakage through the temporary barrier and/or the barrier in the annulus. There is also disclosed a tool for executing such a method.
Claims
1.-17. (canceled)
18. A method for verifying the pressure integrity of a barrier in an annulus outside a pipe string in a wellbore, the method comprising the steps of: establishing a fluid connection between an inside of the pipe string and an annulus outside the pipe string at a first position in the wellbore; establishing a fluid connection between the inside of the pipe string and the annulus outside the pipe string at a second position in the wellbore, the second position being offset from the first position along the axial direction of the wellbore, and the barrier in the annulus being located outside the pipe string between the first and second fluid connections at the first and second positions; establishing a retrievable barrier between the fluid connections at the first and second positions in the wellbore; establishing a pressure differential across the retrievable barrier; releasing a tracer below the retrievable barrier in the wellbore; and sniffing for tracer above the retrievable barrier to verify a leakage through the retrievable barrier and/or the barrier in the annulus, wherein the step of sniffing for tracer above the retrievable barrier comprises: sniffing for tracer from a position A proximate the fluid connection through the pipe string at the first position in the wellbore; and sniffing for tracer from a position B, position B being closer to the retrievable barrier than position A, in the well.
19. The method according to claim 18, wherein the step sniffing for tracer comprises the steps of circulating well fluid by means of a fluid-carrying string from a position above the retrievable barrier to topside and sniffing for tracer topside.
20. The method according to claim 19, wherein the method further comprises the steps of: circulating well fluid by means of a fluid-carrying string by: positioning a circulation opening of the fluid-carrying string at position A proximate the fluid connection through the pipe string at the first position in the wellbore; circulating wellbore fluid from position A in the wellbore to topside; positioning a circulation opening of the fluid-carrying string at position B closer to the retrievable barrier in the well; and circulating wellbore fluid from position B in the wellbore to topside.
21. The method according to claim 20, wherein circulation from positions A and B is performed with the same circulation opening in the fluid-carrying string by moving the circulation opening between the two positions.
22. The method according to claim 20, wherein circulation from positions A and B is performed without moving the fluid-carrying string, as the fluid-carrying string is provided with two or more circulation openings that are selectively controllable to open/close.
23. The method according to claim 18, wherein the step of sniffing for tracer comprises the step of sniffing for or sampling tracer in the wellbore above the retrievable barrier.
24. The method according to claim 23, wherein the method comprises the steps of: sniffing for or sampling tracer at position A proximate the fluid connection through the pipe string at the first position in the wellbore; sniffing for or sampling tracer at position B closer to the retrievable barrier in the well.
25. The method according to claim 23, wherein the method is performed by means of a wireline or slickline.
26. The method according to claim 24, wherein the method is performed by means of a wireline or slickline.
27. The method according to claim 18, wherein sensor data is transferred to topside in real-time.
28. The method according to claim 18, wherein sensor data is stored in memory downhole and collected upon retrieval of the memory topside.
29. The method according to claim 18; wherein the method further comprises the step of removing the retrievable barrier in the well.
30. The method according to claim 18, wherein position B is 5 meters, preferably 3 meters and even more preferably 1 meter above retrievable barrier.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] In the following are described examples of preferred embodiments illustrated in the ac-companying drawings, wherein:
[0056] FIGS. 1-7 show steps in a first method carried out by means of a first tool according to the invention;
[0057] FIG. 8-14 show steps in a second method carried out by means of a second tool according to the invention; and
[0058] FIGS. 15-26 show steps in a third embodiment carried out by means of a third tool according to the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0059] In the following, reference numeral 1 will be used to denote a tool according to the present invention, while reference numeral 10 denotes a wellbore tool assembly according to the invention. The drawings are shown simplified and schematically and the various features therein are not necessarily drawn to scale. Identical reference numerals refer to identical or similar features in the drawings.
[0060] FIG. 1 shows a downhole tool 1 run into a wellbore 2 and connected to wellbore conveying means 3, here shown in the form of drill pipe 3. A connector 5 releasably connects the tool 1 to the drill pipe 3. The tool 1 connected to the drill pipe defines the wellbore tool assembly 10. The tool 1 is provided with an isolation member 7, here shown in the form of a bridge plug. Below the bridge plug 7 the tool 1 is provided a tracer release member 9 in the form of a pressurized canister. The canister 9 may be of the type disclosed in client's own WO2018/128549 A1, to which reference is made for a detailed disclosure of how tracer may be released in the well and by which mechanisms the release may be triggered. Below the canister 9, the tool 1 is provided with a centraliser 11 for maintaining the tool 1 in a central position in the wellbore 2. At its distal end, the tool 1 is provided with a device for establishing fluid communication between a pipe string 13, here in the form of a casing, and annulus 15 between the casing 13 and a not shown surrounding formation. In the shown embodiment the device for establishing fluid communication between the inside of the casing 13 and the annulus 15 on the outside is a perforation gun 19. The perforation gun 19, which is releasably connected to the lower end of the centraliser 11, is adapted to fire at two different positions along the tool 1 as will be explained with reference to the following drawings.
[0061] In FIG. 1 the tool 1 is positioned so that the perforation gun 19 is located adjacent a portion of the annulus 15 with cement 20, as best in the enlarged views, e.g. in FIG. 6. The aim of the method according to the invention is to verify the integrity of the ce-ment/barrier in the annulus as explained above and as will be exemplified in the following.
[0062] In FIG. 2 the tool 1 is shown after the perforation gun 19 has fired to create perforations 21 that establish fluid connection between the inside of the casing 13 and the annulus 15 at a first position P1 and a second position P2 in the wellbore 2. The distance between the two positions P1 and P2 may typically be in the order of 50 meters. However, this may vary depending on the type of well and relevant, applicable standards and regulations.
[0063] FIG. 3 shows the tool after the perforation gun 19 has been released from the rest the tool 1 and dropped into the wellbore 2.
[0064] In FIG. 4 the tool 1 has been moved further into the well so that the bridge plug is 7 placed between perforation 21 at positions P1 and P2, just above the perforations 21 at the lower position P2. The bridge plug 7 is then expanded to an isolating/sealing engagement with the inside of the casing 13 to create a temporary barrier inside the casing 13 between the two sets of perforations 21. Drag blocks 31 provide torsional resistance needed to set the bridge plug 7 by rotation of the drill pipe 3.
[0065] The drill pipe 3 is then separated from the tool 1 as shown in FIG. 5. The bridge plug 7 may provide sufficient axial friction to anchor the tool 1 in the wellbore 2 when separated from the drill pipe 3. Alternatively, the tool 1 may be provided with a not shown anchor in the form of slips or similar. Tracer 23 is now released from the canister 9 as shown in FIG. 6 and best seen in the enlarged section to the lower left. If the bridge plug 7 is properly set and sealing against the inside of the casing 13, the only possible route to leak for the tracer 23 is from the canister 9 inside the casing 13, out though lower perforations 21 at position P2 and into the annulus 15 with the cement 20. The pressure difference aims to drive the tracer 23 through the barrier/cement plug 20 in the annulus 15 and back into the casing 13 through the upper perforations 21 at position P1. Circulation of fluid from topside through the open end of the drill pipe 3 may now start. In the shown embodiment, the open end of the drill pipe 3 is placed at position A adjacent the upper perforations 21 at position P1. Detection of tracer 23 by means of a topside, not shown sen-sor/sniffer when circulating from this position, will be indicative of leak through the cement 20 in the annulus 15 as indicated in FIG. 7. To exclude a false negative result, the method may also include the step of retracting/retrieving the bridge plug 7 from its sealing engagement with the inside of the casing 13, whereby tracer “trapped” below the bridge plug will now be released into the wellbore so that it can be circulated topside and detected/sniffed. If still no tracer 23 is detected after retracting the bridge plug 7, then this is indicative that no tracer was released after all, and that the test cannot be trusted. Though not shown for this embodiment, it is also possible to circulate from different positions in the wellbore 2, including from the position shown in FIGS. 5-7 adjacent the upper perforations 21, as well as at a lower position (B) closer to the bridge plug 7 as explained above and exemplified below.
[0066] In FIG. 8, another embodiment of a tool 1 according to the invention is shown. Instead of the bridge plug shown in FIGS. 1-7, the tool 1 is now provided with two isolation members in the form of upper and lower sets of swab cups 71, 72. The canister 9 (here shown in blue colour) is integrated into the tool between the swab cups 71, 72. A cup-to-cup tool 73 is also provided between the swab cups 71, 72, above the canister 9. The cup-to-cup tool 73 provides fluid communication with the drill pipe 3, whereby the necessary overpressure to set the swab cups 71, 72 may be pumped from topside, through the pipe string 3 and out into the volume between the swab cups 71, 72 through one or more ports/openings in the cup-to-cup tool 73. This embodiment of the tool 1 is also provided with a perforation gun 19 at its distal end, the perforation gun 19 being releasably connected to the rest of the tool 1 so that it can be dropped after firing. At its proximal end, between the connector 5, connecting the tool 1 to the drill string 3, and the upper set of swab cups 71, the tool 1 provided with two selectively openable circulation openings 25, 27. The upper selectively openable circulation opening 25 is shown in the form of a circulation sub and the lower selectively openable circulation opening 27 in the form of a ball valve which is opened/closed by left hand/right hand rotation, respectively, of the drill pipe 3. The drag blocks 31 in certain embodiments also provide the torsional resistance needed to open/close the ball valve 27.
[0067] FIGS. 9 and 10 show the firing and release of the perforation gun 19. As shown in FIG. 11, the tool 1 is run further into the wellbore 2 so that the upper set of swab cups 71 is positioned just above the lower set of perforation 21 at position P2, while the circulation sub 25 is placed at a position A adjacent the upper perforations 21 at position P1. The ball valve 27 is placed below the circulation sub closer to the upper set of swab cups 71 at a position B in the wellbore 2. FIG. 12 shows the tool 1 as tracer 23 is being released from the canister 9 between the sets of the swab cups 71, 72 as best seen in the enlarged view to the lower left in the figure. If the barrier 20 in the annulus is leaking, tracer will leak out through the upper perforations 21 at position P1, as indicated in FIG. 13. Circulation of wellbore fluid from topside may now start, as indicated in FIG. 14, and any leaked tracer may be detected by a not shown sniffer topside. Since both the both the ball valve 27 and circulation sub 25 are selectively openable, it is possible to selectively circulate from ei-ther of the positions B and A, respectively, whereby it becomes possible to distinguish between a leak originating from the upper set of swab cups 71 and the cement 20 in the annulus between the perforations 21 at positions P1 and P2. After circulation has been performed from both positions A and B, the pressure gradient across the upper set of swab cups 71 may be equalised and the sealing engagement between the swab cups 71, 72 and the inside of the casing ceases. False negatives may thus be detected as explained above.
[0068] FIG. 15 shows a third embodiment of a tool 1 according to the present invention. The tool 1 is releasably connected to the drill pipe 3 at connector 5. Below the connector 5, the tool 1 is provided with a flapper valve 29 and set of drag blocks 31 as disclosed above. where the drag blocks 31 may be used to anchor the tool 1 torsionally in the wellbore 2 to detach the drill pipe 3 from the tool 1 by rotation. In some aspects the tool 1 according to this third embodiment is quite similar to the tool 1 of the second embodiment shown in FIGS. 8-15, but instead of being provided with selectively openable fluid circulation openings, the drill pipe 3 is adapted to detach from tool 1 so as to circulate from the open, distal end of the drill pipe 3, similar to the first embodiment shown with reference to FIGS. 1-7.
[0069] In FIGS. 15-17, the tool 1 is positioned adjacent the cemented annulus portion that is to be tested, the perforation gun 19 is fired, the gun 19 is released from the rest of the tool 1 and dropped into the well. In FIG. 18 the tool 1 is positioned with the upper set of swab cups 71 just above the lower set of perforations 21 at position P2. The sets of swab cups 71, 72 are exposed to a pressure gradient by pressurizing the volume between the swab cups 71, 72 through the cup-to-cup tool 73, as disclosed above, whereby they expand to a sealing engagement with the inside of the casing 13. The sets of swab cups 71, 72, when properly set may provide sufficient axial friction to anchor the tool 1 in the wellbore. Alternatively, the tool 1 may be provided with a not shown anchor in the form of slips or similar. The drill pipe 3 then detaches from the tool 1, thereby also closing the flapper valve 29. As shown in FIG. 19, the open, distal end of the drill pipe 3 is then positioned at position A near the upper perforations at position P1. Tracer 23 is released from the canister 9 between the sets of swab cups 71, 72, as indicated in FIG. 20. If the sets of swab cups 71, 72 are properly set and sealing against the inside of the casing 13, the integrity of the annulus cement barrier 20 may be tested and verified by means of the tools and methods according to the invention disclosed herein. In FIG. 21, the enlarged detail to the left indicates tracer 23 that has leaked through the cement barrier 20 and back into the casing 13 at position P1.
[0070] FIG. 22 shows a situation where the upper set of swab cups 71 are not properly set and tracer 23 is leaking through the temporary barrier. FIG. 23 shows that the open end of the drill pipe 3 is moved lower into the well to circulate from a position B closer to the upper set of swab cups 71. Circulation from this position may detect a leak that occurred due to a failing swab cup 71 shown in FIG. 22. As shown in FIG. 24, the drill pipe 3 is stung back into the tool 1, whereby the flapper valve 29 is opened again and the overpressure built up between the sets of swab cups 71, 72 is equalised through the cup-to-cup tool 73 and allowed to migrate up the drill pipe 3. The drill pipe 3 is then once again detached/stung out of the tool 1 so as to circulate to verify that tracer 23 was indeed released from the canister 9 as indicated in FIG. 25. Finally, as shown in FIG. 26, the drill pipe 3 is stung back into the tool 1, and the tool 1 may be retrieved from the well.
[0071] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.
[0072] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
