Method and apparatus for washing an annulus

Abstract

Some examples of the present disclosure relate to a method for washing an annulus that at least partially surrounds a casing in a well. The method comprises locating a tool inside a wellbore casing, and flowing a washing fluid from an injection aperture on the tool and into the annulus via a first casing aperture in the casing. An inflow region of the casing is created having a reduced pressure relative to the annulus, and the method involves flowing the washing fluid from the annulus and into the inflow region of the casing through a second casing aperture in the casing.

Claims

1. A method for washing an annulus that at least partially surrounds a casing in a well, the method comprising: locating a tool inside the casing; flowing a washing fluid from an injection aperture on the tool into the annulus through a first casing aperture in the casing; creating an inflow region within the casing having reduced pressure relative to the annulus using a pressure reduction apparatus, wherein the pressure reduction apparatus comprises at least one fluid aperture disposed on at least one helically extending vane, configured to impart a helical component of velocity to an operating fluid when passed through the pressure reduction apparatus; and flowing the washing fluid from the annulus and into the inflow region of the casing through a second casing aperture in the casing.

2. The method according to claim 1, wherein the at least one fluid aperture establishes a swirl of the operating fluid at the inflow region, thereby establishing reduced pressure within the inflow region relative to the annulus.

3. The method according to claim 2, wherein the washing fluid and the operating fluid are the same fluid.

4. The method according to claim 2, comprising directing the operating fluid using the at least one helically extending vane on the tool.

5. The method according to claim 1, comprising providing a sealing arrangement between the tool and the casing to restrict flow of the washing fluid in the casing, wherein the sealing arrangement is positioned adjacent the injection aperture on the tool.

6. The method according to claim 1, comprising flowing the washing fluid from the injection aperture and into the annulus at the same time as the tool is moved relative to the casing.

7. The method according to claim 1, comprising: ceasing flow of the washing fluid from the injection aperture; moving the tool to a different location in the casing; and reinstating flow of the washing fluid through the injection aperture.

8. The method according to claim 1, comprising setting a plug downhole of the tool.

9. The method according to claim 1, comprising flowing cement through a cement bypass arrangement on the tool; and filling a region of the casing below the tool with cement to create a cement plug.

10. The method according to claim 1, comprising relieving pressure via a pressure bypass arrangement on the tool to reduce the effect of a surge in well fluid pressure acting on the tool.

11. A downhole apparatus for washing an annulus that at least partially surrounds a casing in a well, comprising: an external housing having a bore extending therethrough; a fluid injection port positioned on the housing; and a pressure reduction apparatus positioned uphole of the fluid injection port; wherein, in use, a washing fluid is passed through the fluid injection port and flowed towards the pressure reduction apparatus via the annulus to wash the annulus in the well; and wherein the pressure reduction apparatus comprises at least one fluid aperture disposed on at least one helically extending vane, configured to impart a helical component of velocity to an operating fluid when passed through the pressure reduction apparatus.

12. The downhole apparatus according to claim 11, wherein the at least one helically extending vane of the pressure reduction apparatus extends helically relative to the axis of the tool.

13. The downhole apparatus according to claim 11, comprising at least one of an upper seal located uphole of the fluid injection port, and a lower seal located downhole of the fluid injection port.

14. The downhole apparatus according to claim 13, comprising a bypass arrangement having an uphole bypass port positioned uphole of the upper seal and a downhole bypass port positioned downhole of the lower seal.

15. The downhole apparatus according to claim 11, comprising a releasable plug arrangement configured to be released form the downhole apparatus and set in the casing within which the apparatus is located.

16. The downhole apparatus according to claim 11, comprising a pressure bypass arrangement.

17. The method according to claim 1, comprising flowing cement from the tool and into the annulus.

18. A method for plugging a well which includes a wellbore casing and an annulus at least partially surrounding the wellbore casing, comprising: locating a tool inside the wellbore casing; flowing a washing fluid from an injection aperture on the tool into the annulus through a first casing aperture in the wellbore casing; creating an inflow region within the wellbore casing having reduced pressure relative to the annulus using a pressure reduction apparatus, wherein the pressure reduction apparatus comprises at least one fluid aperture disposed on at least one helically extending vane, configured to impart a helical component of velocity to an operating fluid when passed through the pressure reduction apparatus; flowing the washing fluid from the annulus and into the inflow region of the casing through a second casing aperture in the wellbore casing; and providing a plug in the well.

19. The method according to claim 18, comprising providing a plug in the annulus and within the wellbore casing.

Description

BRIEF DESCRIPTION

(1) FIG. 1 is a schematic illustration of a tool used for washing a well.

(2) FIG. 2 is a schematic illustration of injection apertures and a pressure reduction apparatus of the tool.

(3) FIG. 3A is a further schematic illustration of the pressure reduction apparatus, and FIG. 3B is a sectional view of the pressure reduction apparatus.

(4) FIGS. 4A and 4B are simplified illustrations of a method of use of the tool.

(5) FIGS. 5A and 5B are simplified illustrations of a further method of use of the tool.

(6) FIG. 6 is a schematic illustration of a tool comprising a pressure bypass arrangement.

(7) FIGS. 7A to 7C are sectional illustrations of the pressure bypass arrangement.

DETAILED DESCRIPTION

(8) FIG. 1 is a schematic illustration of a tool 10 used for washing an annulus region in a well. The tool 10 is attached to a tool string 12 via disconnect 14, and the tool string 12 is itself attached to a work string (not shown). The work string may be, for example, jointed pipe and/or coiled tubing, and may be used to convey the tool 10 into the well, and conduct fluid, e.g. a washing fluid, between the surface and the tool 10.

(9) The tool 10 comprises injection apertures 16 through which a fluid can be flowed, with cup seals 18, 20 provided on either axial side of the injection apertures 16. The cup seals 18, 20 provide a seal between the tool and the casing 40 and define an injection region 39 therebetween.

(10) The tool 10 further includes a pressure reduction apparatus 34 positioned uphole of the cup seals 18, 20 and the injection apertures 16, wherein the pressure reduction apparatus 34 comprises a plurality of fluid apertures 32 and vanes 36. The apertures 32 may be placed, and shaped, so as to confer a substantial circumferential component of velocity to an operating fluid flowing therethrough. For example, the apertures 32 may include nozzles, designed to increase the velocity to the operating fluid, and/or eject the operating fluid from the pressure reduction apparatus 34 in a helical direction.

(11) Similarly, the vanes 36 are configured to encourage flow in a radial direction of the fluid flowing from the apertures 32. As such, fluid passing from the pressure reduction apparatus 34 tends to swirl around the apparatus 34, thereby increasing the speed of fluid flow in this region and establishing a localized reduction in pressure. As will be described in more detail below, this area of reduced pressure encourages flow from an annulus region surrounding the casing 40, and as such the area adjacent the pressure reduction apparatus 34 within the casing 40 may be defined as an inflow region 23.

(12) In the present example the tool 10 further includes a perforation system 26 at the leading end of the tool 10 for use in establishing perforations in the casing 40. The perforation system 26 may comprise, for example, TCP guns, fluid jet perforating devices, chemical cutting devices, tubing punches, or the like. It should be noted that, although a perforation system 26 is shown in this example, in other examples a perforation system may not be necessary. Instead, the tool 10 may be run into a section of casing having pre-existing perforations, for example.

(13) The tool 10 further includes a burst disk sub 30, dart sub 22 and dart catcher 24. A dart (not shown) may be used to seat in the dart sub 22, thereby blocking flow through the dart sub 22. When flow through the dart sub 22 is blocked, fluid may only pass from the tool through the injection apertures 16 or the apertures 32 of the pressure reduction apparatus 34.

(14) The tool 10 includes a plug 28 axially downhole of the dart sub 22 and dart catcher 24. Although not shown, the plug 28 is attached to the tool 10 via a pressure release mechanism, such that the plug 28 may be released upon pressurization of the fluid in the tool 10. The skilled person will understand that there are several known release mechanisms that would be suitable for this purpose.

(15) FIG. 2 shows a section of the tool 10 in greater detail, including the casing 40 in which the tool 10 has been placed, and a surrounding formation 42. An annulus 46 is defined between the casing 40 and formation 42, and in the present example the annulus is filled with cement 44 which is to be at least partially removed by action of the tool. In alternative examples the annulus 46 may be filled with debris, for example from the original well drilling operation. Perforations 38 in the casing 40, created by the perforation system 26 (FIG. 1), establish fluid communication between the casing 40 and annulus 46. In this respect the presence of the seals 18, 20 provide or create a communication path between the injection region 39 and the inflow region 23 via the annulus 46.

(16) In use, washing fluid is pumped from surface and exits the tool 10 via the injection apertures 16 and into the injection region 39, and then into the annulus 46 via one or more of the casing perforations 38, illustrated by arrows A. In this respect, a perforation 38 which provides such communication of fluid into the annulus 46 may be defined as a first casing aperture 38a. A plurality of first casing apertures 38a may accommodate flow into the annulus 46.

(17) The washing fluid then moves upwardly through the annulus 46 and disrupts or breaks-up the cement 44, with the washing fluid and cement debris flowing back into the casing 40, specifically into the inflow region 23, via different casing perforations 38. In this respect, a perforation 38 which provides such communication of fluid from the annulus 46 may be defined as a second casing aperture 38b. A plurality of second casing apertures 38b may accommodate flow from the annulus 46. The washing fluid and entrained cement debris may then flow to surface in the direction of arrows B.

(18) A portion of the washing fluid also flows from the apertures 32 of the pressure reduction apparatus 34 (indicated by arrows G) and into the inflow region 23. The swirling motion of the fluid caused by the pressure reduction apparatus 34 creates a localized region of relatively lower pressure, at least relative to the pressure within the annulus 46. This lower pressure within the inflow region 23 assists to draw or encourage the washing fluid and cement debris into the casing 40 from the annulus 46. This can assist in providing a better cleaning or washing within the annulus 46.

(19) The tool 10 can be moved uphole and downhole relative to the casing 40 to wash an extended length of the annulus 46. As the tool 10 is moved uphole and downhole in the casing 40, the inflow region 23 and injection region 39 move with the tool 10. In this regard, a perforation 38 which at one stage functioned as a first casing aperture 38a (i.e., to allow flow into the annulus 46), may later function as second casing aperture 38b (i.e., to allow flow from the annulus 46).

(20) Using some prior washing techniques, there is a tendency for the washing fluid to spread out in the annulus, which can reduce the efficacy of the wash. However, the present invention negates such drawbacks, for example through use of pressure reduction apparatus to encourage flow of washing fluid and debris into casing 40.

(21) FIGS. 3A and 3B illustrate an example of the pressure reduction apparatus 34. The pressure reduction apparatus 34 comprises the apertures 32 and vanes 36, which as noted above encourage a swirling or turbulent flow region within the inflow region 23 (FIGS. 1 and 2). Apertures 32 are located on the outer circumferential surface of the vanes 36 (i.e. the tips of the vanes), as well as in the recessed sections between the vanes 36.

(22) FIG. 3B illustrates a sectional view of the pressure reduction apparatus 34. The pressure reduction apparatus 34 comprises a flow distribution sleeve 50 which includes a plurality of radial ports 56, wherein the flow distribution sleeve 50 is mounted within the apparatus 34 to define a distribution annulus 57 which communicates with all of the apertures 32. When the radial ports 56 are opened, fluid may thus flow from the apparatus 34.

(23) The pressure reduction apparatus 34 further includes an internal sleeve system 52 which functions to selectively close and open the radial ports 56 in the flow distribution sleeve 50, thus to selectively permit flow from the pressure reduction apparatus 34. The sleeve system 52 includes an upper sleeve 52a and a lower sleeve 52b, with the upper and lower sleeves 52a, 52b initially fastened to the flow distribution sleeve 50 via respective shear pins 54a, 54b. While the present example uses shear pins, multiple alternative options are possible, and in some cases resettable options may be used. When in the initial illustrated configuration, the lower sleeve 52b closes the radial ports 56 in the flow distribution sleeve 50. Each sleeve 52a, 52b includes a respective seat 53a, 53b for receiving an object, such as a ball or dart, dropped from surface. In the present example the seat 53b of the lower sleeve 52b defines a smaller diameter than the seat 53a of the upper sleeve 52a to facilitate sequential operation using appropriately sized objects.

(24) When it is desired to open the radial ports 50, and thus permit flow from the pressure reduction apparatus 34, an object (not shown) is dropped to engage the seat 53b of the lower sleeve 52b. The impact force, and/or pressure developed behind the object shears pins 54b with the lower sleeve 52b then moved to open the ports 56 and permit a fluid (e.g. a washing fluid) to flow from a main bore 58 of the pressure reduction apparatus 34 and ultimately through the fluid apertures 32. The object responsible for shifting the lower sleeve 52b may be removed, for example by being degradable, pushed past its seat 53b or the like, thus maintaining the main bore 58 open.

(25) When the ports 56 are to be closed, an object (not shown) of a larger diameter is dropped to engage the seat 53a of the upper sleeve 52a. The impact force, and/or pressure developed behind the object shears pins 54a with the upper sleeve 52a then moved to occlude the ports 56.

(26) FIGS. 4A and 4B illustrate the tool 10 in use for washing a casing 40. The tool 10 is held adjacent the perforations 38 closest to the surface. Washing fluid is flowed through the injection apertures 16 and passes through the perforations 38 in the casing 40. The washing fluid flows in the direction of arrows C, through the annulus 46 and back inside the casing 40. The pressure reduction apparatus 34 encourages the washing fluid to re-enter the casing via perforations 38 adjacent, or nearest to, the pressure reduction apparatus 34.

(27) Washing fluid is continually flowed through the injection apertures 16 as the tool 10 is moved downhole, as shown in FIG. 4B. The rate of movement downhole of the tool 10 is proportional to the rate at which washing fluid is flowed through the injection apertures 16. The tool may be moved in an incremental step-wise motion. Alternatively, the tool may be moved in a continuous motion through the casing. As the tool is moved, washing fluid is flowed through perforations 38 further downhole, thereby washing the section of the casing 40 located further downhole.

(28) As shown by the arrows C of FIG. 4B, as the pressure reduction apparatus 34 is moved downhole with the tool 10, the washing fluid re-enters the casing through perforations 38 adjacent the pressure reduction apparatus 38. Using the tool 10 in this way, the entire section of casing 40 in the region of the perforations 38 may be washed.

(29) The operation described in FIGS. 4A and 4B may be performed multiple times to improve the quality of the washing of the casing. Further, the operation may be performed multiple times, using more than one type of washing fluid.

(30) The plug 28 of the tool 10 is illustrated in FIG. 4A. Once the tool 10 has been moved to the position shown in FIG. 4B, the plug 28 may be installed or set in the casing 40, to act as a support for future operations, for example future cementing operations. The plug 28 may be set in the casing 40 once the tool 10 has reached the position show in FIG. 4B, or alternatively, the tool 10 may be moved further downhole before the plug 28 is set.

(31) As the plug 28, as well as some other parts of the tool 10, defines a relatively large diameter, there may be a problem whereby sudden influxes or kicks in pressure into the casing 40 are unable to quickly bypass the plug 28, and have the effect of forcing the tool 10 in the uphole direction. This can cause the work string to rapidly spool from the well, which can be dangerous. A bypass arrangement, such as that described later with reference to FIGS. 7A to 7C may be used to mitigate against such issues.

(32) FIGS. 5A and 5B illustrate a use of the tool 10 to flow a fluid such as cement into the casing. Such flow of cement may be performed immediately following a washing operation as described above. In the present example the tool 10 is placed with the injection apertures 16 adjacent the furthest downhole of the perforations 38 in the casing 40. As shown, plug 28 is placed in the casing to support a cement plug formed on top thereof. Cement is then flowed through the tool 10, through the injection ports 16, and through the perforations 38 in the casing 40 in the direction of arrows D. As the cement fills the annulus, and moves in the uphole direction through the annulus, the cement will re-enter the casing 40 and flow through upper bypass ports 60. Upper bypass ports 60 then direct the cement through a fluid bypass (not visible) and out through lower bypass ports 62. The cement is then able to fill the casing below the tool 10 and on top of the previously set plug.

(33) Once the cement has begun to fill the casing 40 downhole of the fluid injection apertures 16, the tool 10 can be moved uphole, while continually flowing cement though the tool 10. In this way, the tool 10 can be used to place cement in the annulus 46 and the casing 40. The rate of movement of the tool 10 in the uphole direction is proportionate to the rate at which the cement is flowed through the tool 10 so as to allow an even distribution of cement in the casing 40 and annulus 46. The tool 10 can be moved in a continuous motion through the casing 40, or in an incremental step-wise motion.

(34) The flowing of cement into the casing 40 may be performed after the casing has been washed. The washing of the casing may permit a better bond to be achieved between the casing and the cement.

(35) FIG. 6 schematically illustrates the tool 10 as described above with the addition of a pressure bypass arrangement 260. The pressure bypass arrangement 260 is located above the tool. In some examples the pressure bypass arrangement 260 may be provided separately from the tool 10, or as an integrated feature.

(36) FIGS. 7A to 7C illustrate the internal detail of the pressure bypass arrangement 260. In this example, the pressure bypass arrangement 260 forms a part of the tool 10, and comprises an array of pressure bypass ports 264.

(37) FIG. 7A illustrates the pressure bypass arrangement 260 in a normally closed configuration, meaning that a sleeve assembly 266 of the pressure bypass arrangement 260 is occluding the array of pressure bypass ports 264. The sleeve assembly 266 is partially housed in an annulus 268 formed between a shear sleeve 270 and an outer housing 272 of the pressure bypass arrangement, and partially housing in a central bore 280 of the pressure bypass arrangement 260. Spring 274 biases the sleeve 266 towards the closed position.

(38) The shear sleeve 270 is attached to a flapper valve assembly comprising a flapper valve 278 which can be opened to allow fluid through the central bore 280 of the pressure bypass arrangement 260 and closed to substantially block flow therethrough. The flapper valve 278 comprises a flapper aperture 282, in this example located in the center thereof, to allow a reduced fluid flow therethrough.

(39) FIG. 7B illustrates the pressure bypass arrangement 260 in a run-in configuration. In this configuration, fluid flowing in the uphole direction as a result of the tool 210 being run downhole, impinges on the sleeve assembly 266 and flapper valve 278, and creates a build-up of pressure beneath the flapper valve 278. Once the pressure beneath the flapper valve builds to a threshold level, the sleeve assembly 266 moves in an uphole direction, compressing the spring 274. This has the effect of removing the occlusion to the pressure bypass ports 264 caused by the sleeve assembly 266 to allow fluid communication between the central bore 280 and the casing (not shown). A fluid in the central bore 280 is then permitted to flow from the central bore and into the casing in the direction of arrows D. As a result of the flapper aperture 282, some fluid is also permitted to continue to flow through the central bore 280 of the pressure bypass arrangement, in the direction of arrows E. In opening the pressure bypass ports 264 the tool 210 may be run downhole more quickly.

(40) FIG. 7C illustrates the pressure bypass arrangement 260 in a circulating configuration. In this configuration, the tool 210 may be used to circulate a fluid in a well (not shown). As such, fluid is flowing in the downhole direction, as illustrated by arrows F, through the central bore 280 of the pressure bypass arrangement, and flapper valve 278 is opened. The downhole flow of fluid causes spring 274 to bias the sleeve assembly 266 towards the downhole direction, thereby closing the array of pressure bypass ports 264.

(41) The pressure bypass arrangement 260 may improve the safety of operation of the tool 10 by allowing the tool to react more preferably to sudden influxes, or kicks, of pressurized fluid in a well. For example, a sudden influx of pressure into the pressure bypass arrangement may create a brief flow of fluid in the uphole direction through the pressure bypass arrangement. Such an up-flow of fluid may act on the sleeve assembly 266 in an uphole direction to open pressure bypass ports 264, thus allowing the pressurized fluid to escape from the tool 210 and into the casing (not shown). In doing so, an operator may be able to avoid an influx of pressure physically moving the tool 10, and the entire associated tool string, back uphole, as sudden uphole movement of the tool string may cause safety concerns at the surface of the well.