GB2354272A - Wellhead cleanup tool - Google Patents

Abstract

A cleanup tool (1) particularly for use with the stepped internal profile of a wellhead (2) has a fluid inlet and internal passage (6) which communicates with axial outlet and a number of radial outlets (11). In use, if the tool does not contact the wellhead, fluid flow occurs through the annulus formed by the outside of the tool (1) and the inside of the wellhead (fig 2), thus cleaning the wellhead. If the tool contacts the wellhead internally by bearing ring (13), fluid passes into inlet port (16) and out through radial ports (11). In order to clean wellheads of different internal profiles the tool (1) can be formed as two barrel sections (17, 18, fig 4) which slide vertically. Various methods are described which show means by which the ports (11) can be selectively opened and these include the use of a shear sleeve which may be sheared by mechanical action, or by the build up of hydrostatic pressure as a result of a ball being dropped from the surface onto ball seat (21, figs 5-8). Brushes (10) may also be present on the tool and the tool may be rotated relative to the wellhead.

Description

1 2354272 I WELLHEAD CLEANUP TOOL 2 3 The present invention relates to

borehole clean up, 4 particularly a tool for cleaning up the stepped region of 5 a wellhead. 6 7 Boreholes are typically lined with a concrete casing. In 8 order to maximise production from the well it is 9 necessary to clean out the casing, removing debris and 10 contaminants. 11 12 one region of the borehole which is particularly hard to 13 clean is the wellhead. The wellhead is stepped in 14 diameter, with a larger diameter at the top. A typical 15 prof ile is shown in Figure 1. The diameters A, B, C and 16 D are of commonly standardised dimensions, but there is 17 some variation between steps E and F from well to well. 18 19 Due to the stepped profile, tools adapted to clean the 20 main body of the borehole with brushes and jets of 21 cleaning fluid will not be of the correct diameter to 22 clean the upper steps. At the present time, the stepped 23 profile of the wellhead cannot be properly cleaned.

2 1 Successfully cleaning the stepped region of the wellhead 2 would significantly improve fluid flow in the region of 3 the wellhead and so have benefits for production. 4 5 The primary aim of the present invention is -to provide 6 apparatus for cleaning stepped profile borehole casing. 7 8 A further aim of the present invention is to provide 9 apparatus for cleaning stepped profile borehole casing 10 that can adapt readily to the particular vertical 11 distances between steps. 12 13 Running a workstring is time consuming and therefore 14 expensive. For this reason, it is desirable to be able 15 to run a workstring with tools to carry out a variety of 16 functions. therefore, a still further aim of the present 17 invention is to provide apparatus for cleaning stepped 18 profile borehole casing that can be integrated into a 19 workstring and can also be employed only when required. 20 21 According to the present invention there is provided a 22 cleanup tool for cleaning stepped regions of boreholes, 23 the tool comprising a tool body into which fluid may flow 24 axially, a plurality of radial outlets which correspond 25 in position to the profile of a stepped region of a 26 borehole and an engagable means for encouraging fluid to 27 exit through the radial outlets. 28 29 Preferably, the tool body is adapted to be incorporated 30 into a workstring. 31 32 The tool body may comprise a plurality of axially 33 slidably mounted barrels adapted to rest on steps in the 34 profile of a borehole and thereby to enable the position 3 1 of the plurality of outlets to correspond to the profile 2 of the stepped region of a borehole. 3 4 Springs may be provided to oppose the axial motion of the 5 slidably mounted barrels. 6 7 The engagable means for encouraging fluid to exit through 8 the radial outlets may comprise a valve activated by a 9 ball dropped down the workstring. 10 11 Alternatively, the engagable means for encouraging fluid 12 to exit through the radial outlets may comprise a valve 13 that is engaged by the axial movement of a shear sleeve 14 when the shear sleeve bottoms out on a step in a 15 borehole. 16 17 Alternatively, the engagable means for encouraging fluid 18 to exit through the radial outlets may comprise an outlet 19 from which axially flowing fluid passes, a plug which 20 acts to reduce fluid flow between the external surface of 21 the tool and the internal surface of the borehole, and an 22 inlet through which fluid may enter the body of the tool 23 and subsequently exit through the radial outlets. 24 25 Preferably, the plug comprises a means for engaging a 26 step in the internal surface of a borehole. 27 28 Preferably also, the means for engaging a step in the 29 internal surface of a borehole comprises a curved 30 profile. 31 32 Preferably also, the means for engaging a step in the 33 internal surface of a borehole may be rotatably mounted 34 on the tool body.

4 1 The present invention will now be described with 2 reference to the following diagrams in which:

3 4 Figure 1 shows a cross-section through a wellhead with a stepped internal casing; 6 Figure 2 shows a half-sectional elevation through a 7 cleanup tool in a wellhead whilst the tool is not 8 bottomed out; 9 Figure 3 shows a half-sectional elevation through a cleanup tool in a wellhead whilst the tool shoulder 11 it bottomed out on a wellhead shoulder; 12 Figure 4 shows a half-sectional elevation through a 13 cleanup tool which can adapt to the particular 14 spacing between steps in the given wellhead; Figure 5 shows a half-sectional elevation through an 16 embodiment of a cleanup tool incorporating a ball 17 seat before it is activated; 18 Figure 6 shows a half-sectional elevation through an 19 embodiment of a cleanup tool incorporating a ball seat after is have been activated; 21 Figure 7 shows a half-sectional elevation through an 22 embodiment of a cleanup tool incorporating a shear 23 sleeve before it is activated; and 24 Figure 8 shows a half-sectional elevation through an embodiment of a cleanup tool incorporating a shear 26 sleeve after it has been activated.

27 28 figure 2 shows in half-sectional elevation a cleanup tool 29 1 for use in a borehole wellhead 2 which has at least one 30 step 3 in its diameter. Figure 3 shows in half-sectional 31 elevation the same cleanup tool bottomed out on a 32 shoulder of the wellhead. 33 1 The cleanup tool is f ixedly mounted in a workstring 2 through upper and lower box connections 4, 5 and moves 3 and rotates with the workstring.

4 Cleaning fluid is passed down the throughbore 6 of the 6 workstring and cleanup tool. At or below the base of the 7 cleanup tool, cleaning fluid is pumped out of the 8 workstring into the central (cased)shaft of the borehole 9 where it circulates upwards.

11 The body of the tool comprises in the present example 12 three stepped outer cylindrical faces 7, 8, 9 designed 13 to correspond to the stepped inner circumference of the 14 wellhead, leaving only a small gap.

16 Two types of cleaning means are also provided. A 17 plurality of brushes 10 brush debris from the wellhead.

18 A plurality of radial outlets 11 also act to remove 19 debris from the wellhead when cleaning fluid is forced through conduits 12.

21 22 In the configuration shown in Figure 2, where the tool is 23 not bottomed out on a shoulder of the wellhead, cleaning 24 fluid returns to the surface through the annulus formed between the outside circumference of the cleanup tool and 26 the inner circumference of the cleanup tool and the inner 27 circumference of the wellhead. This annulus is small 28 relative to the cross-sectional area of the actual 29 wellhead itself and so the cleaning fluid flows faster in the annulus than above or below the tool. The increased 31 flow rate near the inner surface of the wellhead leads to 32 efficient cleaning. Due to the correspondence between 33 the stepped outer cylindrical faces and the internal 34 circumference of the wellhead, the flow rate remains high 6 1 throughout the stepped region and so the tool is 2 efficient at cleaning stepped wellheads. The cleanup 3 tool may be rotated by turning the workstring. 4 5 Figure 3 shows the circumstance when the cleanup tool is 6 lowered onto a shoulder of the wellhead. A main bearing 7 ring 13 is provided which sits between a bearing 8 retaining ring 14 and an upper bearing ring 15. the 9 bearing retaining ring 14 has a curved profile and it is 10 this curved profile which bottoms out on the step of the 11 wellhead forming a partial seal. Due to the curved 12 profile, a partial seal will be formed despite the 13 variations which are found in practise between the 14 diameters of the stepped internal circumference of 15 different wellheads. 16 17 Due to the partial seal, pressure forces cleaning fluid 18 through one or more ports 16 into conduits 12 thereby 19 ejecting cleaning fluid out of the outlets 11 which also 20 act to clean the internal circumference of the wellhead. 21 22 The seal may be partial or complete. The seal requires 23 merely to ensure that much of the cleaning fluid passes 24 through the ports and thereby out the radial outlets, 25 although a better seal will improve the quality of the 26 resulting cleaning. 27 28 It would be advantageous in practice to be able to rotate 29 the workstring and cleanup tool in order to move the 30 brushes and jets around the internal circumference of the 31 wellhead and to operate other workstring functions.

32 Clearly, this would be difficult if the curved profile 33 which contacts the stepped wellhead were not mounted on 34 bearings. Without this feature, friction would make it 7 1 difficult to rotate the cleanup tool and the cleanup tool 2 would readily be damaged. 3 4 It will be noted that the above invention, whilst highly 5 effective in cleaning stepped wellheads which correspond 6 in shape to the particular cleanup tool, would be less 7 effective for cleaning wellheads which do not correspond 8 in shape with the cleanup tool. As mentioned above, the 9 diameters of steps are standardised but the distance 10 between steps may vary between wells. 11 12 An alternative embodiment able to adapt to wellheads with 13 different spacings between steps is show in half14 sectional elevation in Figure 4. Two barrels 17 and 18 15 are adapted to slide vertically. Each is keyed to 16 prevent rotational movement. When the tool bottoms out 17 on the stepped region of the wellhead, the slidable 18 barrels 17, 18 are slid by the profile of the wellhead to 19 the correct vertical height to clean the wellhead. 20 Springs 19 and 20 act to push the barrels 17, 18 21 downward. Bearing rings may or may not be provided at 22 the base of each barrel. 23 24 Figure 5 illustrates in half-sectional elevation an 25 alternative embodiment of a cleanup tool. This tool is 26 provided with a ball seat 21 attached to a sleeve 22a on 27 which are mounted seals 22b and a shear pin 23. The 28 sleeve 22a initially blocks a port 24 and cleaning fluid 29 forced down the throughbore passes out the base of the 30 tool and flow upwards. However, a ball may be dropped 31 down the throughbore to the ball seat 21, blocking flow 32 of cleaning fluid. A buildup of pressure will then ensue 33 until the pressure on the ball exceeds the capacity of 34 the shear pin 123 which then shears, allowing the ball 8 1 seat 21 and sleeve 22a to move down, opening access to 2 the port 24. 3 4 Figure 6 shows in half-sectional elevation the 5 configuration once the pin has sheared and the port is 6 opened. The ball 25 remains in the throughbore and so 7 cleaning fluid follows a new flow path through the port 8 into conduits 26 and out through outlets 27. 9 10 Figure 7 shows in half-sectional elevation a further 11 embodiment. In this embodiment there is provided a shear 12 sleeve 28 which is prevented from moving vertically by a 13 shear pin 29 and ins prevented from rotating relative to 14 the mandrel by a key 30. As before, flow of cleaning 15 fluid is initially axially through the tool. fluid 16 cannot reach the outlets as a port 31 is blocked by a 17 section of the sleeve 32 bounded by seals 33. 18 19 In order to operate the jets, the tool is bottomed out on 20 a shoulder of the wellhead. The resulting force shears 21 the shear pin 29 and so the shear sleeve 28 is pushed up 22 the body of the tool, opening the port 31. Figure 8 23 shows in half-sectional elevation the resulting 24 configuration in which cleaning fluid is now supplied to 25 the outlets. 26 27 It will be clear to one skilled in the art that the 28 various features described herein may readily be combined 29 in different ways. 30 31 Further modifications and improvements may be 32 incorporated without departing from the scope of the 33 invention herein intended.

9 1 MAIMS:

2 3 1 A cleanup tool suitable for cleaning regions of 4 stepped or varying diameter in a well-bore, the tool comprising a tool body having an inlet for receiving 6 fluid, wherein the inlet communicates with a passage 7 defining a fluid path within said body, wherein the 8 passage is associated with a first generally axial 9 outlet and a plurality of radial outlets at least some of which are provided at varying radial 11 distances from a central longitudinal axis, and an 12 engageable means for selectively encouraging fluid 13 in the tool body to exit through the radial outlets.

14

Claims (1)

1. 2. A cleanup tool as claimed in Claim 1 wherein the

   16 tool body has. a varying outer diameter which 17 substantially corresponds to the profile of a region 18 of stepped or varying diameter in a borehole.

   19 3. A cleanup tool as claimed in Claim 1 or 2 wherein 21 the region in the borehole is the well head.

   22 23 4. A cleanup tool as claimed in any one of the 24 preceding Claims, wherein the tool body is adapted to be incorporated into a workstring.

   26 27 5. A cleanup tool as claimed in any one of the 28 preceding Claims, wherein the tool body comprises a 29 plurality of cylindrical barrels that are axially slidable relative to a central part of the tool 31 body, wherein the barrels are adapted to rest on 32 steps in the profile of the wellbore wall or casing.

   33 1 6. A cleanup tool as claimed in Claim 5 wherein springs 2 are provided to oppose the axial motion of the 3 slidably mounted barrels.

   4 7. A cleanup tool as claimed in any one of the 6 preceding Claims wherein the engagable means for 7 encouraging fluid to exit through the radial outlets 8 may comprise a valve, wherein the valve is movable 9 between a first position where the first outlet is 10 open to a second position where the first outlet is 11 closed. 12 13 8. A cleanup tool as claimed in any one of the 14 preceding Claims wherein the engagable means for 15 encouraging fluid to exit through the radial outlets 16 may comprise a valve, wherein the valve is movable 17 between a first position where the radial outlets 18 are closed or obturated and a second position where 19 the radial outlets are open and not obturated. 20 21 9. A clean up tool as claimed in Claim 7 or 8, wherein 22 the valve includes a dropped ball or dart.

   23 24 10. A cleanup tool as claimed in Claim 7 or 8 wherein, in use, movement of the valve from the first 26 position to the second position is enabled by 27 weight-setting the tool such that a shearable sleeve 28 is sheared and moves to forcibly act on the valve. 29 11. A cleanup tool as claimed in any one of the 31 preceding Claims wherein the radial outlets are 32 associated with a different inlet to the first 33 inlet.

   34 11 1 12. A cleanup tool as claimed in any one of the 2 preceding Claims wherein the tool body incorporates 3 mechanical cleaning members.

   4 13. A cleanup tool as claimed in Claim 12 wherein the 6 mechanical cleaning members are brush bristles.

   7 8 14. A cleanup tool as claimed in any one of the 9 preceding Claims wherein the tool body comprises a 10 bearing to facilitate rotation of the body relative 11 to the stepped or varying diameter region of the 12 borehole when the body is resting thereon. 13