Downhole cleaning tool and method

A downhole cleaning tool (120) for use in a drilled bore, such as an oil and gas well (100). The tool (120) comprises a tubular body (130) defining an internal bore (136) and at least one radially extending blade (148) defining a pocket (152) having sides and a base. A cam-activated radially extendable cleaning element (154) is mounted in the pocket (152) and is movable between a retracted position and an extended position. Multiple pockets (152) and cleaning elements (154) may be provided. The activating cam may be in the form of a pipe, which may be a single unitary part or may be in multiple parts. The parts of the multiple-part pipe may be axially spaced and may activate the cleaning elements in a staggered or sequential manner.

FIELD

This disclosure relates to a cleaning tool and cleaning method. Examples of the disclosure relate to a scraper for treating downhole tubing.

BACKGROUND

In the oil and gas exploration and production industry drilled bores are lined with metal tubing. The internal surfaces of the tubing may become contaminated with material, for example drill cuttings or cement residue. An operator may elect to clean the tubing, for example to provide a surface suitable for the creation of a seal with a packer or the like.

There have been proposals for providing tubing cleaning apparatus in which cleaning elements are initially retained in a body in a retracted or dormant position. The cleaning elements may be extended when required, the extending cleaning elements then contacting the internal surface of the surrounding tubing. Multiple cleaning elements may be arranged and located such that full circumferential contact between the cleaning elements and the tubing may be achieved by axial reciprocation of the apparatus, without requiring rotation of the apparatus. Examples of such apparatus are described in, for example, U.S. Pat. Nos. 10,526,871 and 8,905,126.

In U.S. Pat. No. 10,041,333 a drilling assembly features retracted scrapers and a closed circulation sub so that the drilling can commence with string pressure delivered to bit nozzles due to the circulation sub being in a closed position. When drilling is done and the bit is to be removed, a ball lands on a seat on a sleeve that acts as a piston to break scraper retainers for casing scraping deployment and to open the circulation port. A bypass opens around the seated ball when the sleeve shifts to allow flow around the seated ball for circulation while scraping.

U.S. Pat. No. 8,955,584 describes a method of drilling and cleaning a wellbore while rotating the drill string after full drilling depth is reached without running the drill string out the bore to install a clean-up work string. A drill string having a drill bit at one end includes at least one near bit selectively activatable cleaning tool mounted within the length of the drill string, the cleaning tool having a cleaning member adapted to be moved from a close-fitting stowed configuration within a recess in the tool body to a deployed configuration. The recess extends through the tool body and an inner surface of the cleaning member engages a surface of an axially displaceable sleeve which acts as a cam member.

U.S. Pat. No. 10,526,871 describes a downhole cleaning apparatus comprising a tubular body with a plurality of openings therethrough. Each opening defines at least part of a helix extending longitudinally and circumferentially about the tubular body. The downhole cleaning apparatus also includes a plurality of cleaning elements. Each cleaning element is configured to extend through an opening and to extend outwards from an outer surface of the tubular body.

SUMMARY

An aspect of this disclosure relates to a downhole cleaning tool for location in a bore, the tool comprising a tubular body defining an internal bore and at least one radially extending blade defining a pocket having sides and a base, and a radially extendable cleaning element mounted in the pocket and movable between a retracted position and an extended position.

The base of the pocket may be substantially planar or may comprise a substantially planar portion. The cleaning element may have an inner surface and the surface may be substantially planar or may comprise a substantially planar portion. The inner surface of the cleaning element may engage the base of the pocket when the element is in the retracted position, and the engaging surfaces may coincide or match to provide a relatively large contact area therebetween. In the extended position the inner surface of the cleaning element may be radially spaced from the base of the pocket.

The tool may include a cam member, and the radially extendable element may be operatively associated with a cam follower for engaging the cam member. The cam member may be provided internally of the body and the cam follower may extend through the base of the pocket into contact with the cam member. The cam follower may extend through a relatively small area port or opening in the base of the pocket, which opening may be arranged to have a minimal impact on the strength and rigidity of the body. The cam member may comprise an axially extending member, such as a sleeve, pipe or tube, and may extend along the internal bore of the body. The cam member may be in a sliding, sealing relationship with a wall of the internal bore of the body to isolate fluid in the internal bore of the body from external fluid. The cam follower may comprise a radially extending plunger having an outer end for engaging the radially extendable element and an inner end for engaging the cam member. The cam member may be translatable relative to the cam follower and may include a cam surface for engaging an inner portion of the cam follower. The cam surface may include a first portion and a second portion. Relative movement of the cam surface relative to the cam follower may not induce any movement of the cam follower while the cam follower is in contact with the first portion, the cam follower only being moved radially outwards when in contact with the second portion.

Multiple cleaning elements may be provided. The cleaning elements may each be provided with an associated cam follower. The cleaning elements may be configured to be extended simultaneously or may be configured to be extended in a sequence. Sequential operation may be achieved by configuring the cam member to act on the cam followers in a sequential manner, for example the second portion on the cam surface may be in different positions relative to the respective cam followers or cleaning elements, resulting in a staggered cam action and a staggered deployment of the cleaning elements. Thus, the cleaning element deployment force generated by the cam member may be concentrated on a single cleaning element which is extended before the deployment force is applied to another cleaning element. This may be useful if retaining forces, such as friction or a shear retainer, must be overcome to extend the cleaning elements.

The cam member may be translated by any appropriate arrangement. In one example the cam member is engageable with an occluding member, such as a ball or dart, which permits creation of a fluid pressure differential across the occluding member, and creation of an axial fluid pressure force. The occluding member may be translatable from the cam member, or the cam member or the occluding member may be translatable to a position in which fluid may bypass the occluding member.

The radially extendable cleaning element may be biased towards the extended position. A spring or other biasing member may be provided to act between the base of the pocket and the cleaning element. One or more compression springs may be provided in combination with each cleaning element and multiple springs may be axially spaced along the element. The spring may be located within a blind bore in a rear face of the cleaning element. In other examples hydraulic pressure may be utilised to extend the cleaning element; in a drill string the pressure of the fluid being pumped down through the string is higher than the pressure of the fluid in the annulus surrounding the string, and the resulting pressure differential may be employed to exert a radial pressure force on the cleaning element.

The radial extension of the cleaning element may be restricted by a stop member. The stop member may extend between the cleaning element and the body. In one example a stop member extends through a radial bore in the cleaning element and engages the base of the pocket. The radial bore may be stepped, and the stop member may have a larger diameter head. The stop member may have a threaded end to engage with a corresponding threaded bore in the body. One or more stop members may be provided in each cleaning element. In another example the stop member may comprise a plate or other member fixed on the outside of the tool body and extending over a stepped cleaning element, or a stop member may extend through a slot in the element.

Where the cleaning element is provided in combination with a stop member and a biasing arrangement, the biasing arrangement may be adapted to urge the cleaning element to the maximum radial extension as permitted by the stop member. The stop member and the biasing arrangement may be adapted to permit a maximum radial extension of the cleaning element to describe a diameter larger than the diameter of tubing to be cleaned. Such an arrangement facilitates cleaning of inclined or horizontal tubing, where the weight of the tubing string will tend to offset the string to the low side of the tubing and will tend to urge the cleaning element radially inwards when engaging the low side of the tubing.

The radially extendable cleaning element may be releasably retained in the retracted position. One or more shear members may retain the cleaning element in the retracted position. A shear member, such as a shear pin, may extend between the cleaning element and another part of the tool. In one example a shear member extends between the cleaning element and an axially movable member, such as a cam member; the shear member may extend radially and be sheared on axial movement of the cam member relative to the tool body. Shearing of the shear member may be associated with initial movement of the cam member which may not produce any movement of an associated cam follower. In another example an elevated internal pressure may be generated to urge the cleaning member outwards from the retracted position to shear a retaining shear pin, or otherwise reconfigure a retaining arrangement. Such a pressure may be generated by temporarily blocking the through bore of the body using an occluding device such as a ball or dart. The occluding device could be subsequently sheared through a restriction, or the restriction shifted to permit fluid bypass around the device.

The radially extendable cleaning element and associated parts of the body may be adapted to minimise voids or spaces which may fill with material prior to activation of the tool and restrict movement of the cleaning element. When used in a drilling environment the tool will be located in drilling fluid carrying fine particulate material. This material tends to accumulate in and fill spaces and voids in downhole tools and in certain circumstances the tools may become “packed-off”, where the accumulation of material prevents operation of the tool. Alternatively, or in addition, the tool may be configured to facilitate movement or displacement of such particulate material. For example, if the material accumulates in and bridges a clearance gap between the cleaning element and the pocket the material may create a seal and prevent or restrict movement of the element. However, if some larger gaps or other passages are provided these may be less likely to be bridged and will facilitate flow of fluid in behind the element. Also, if the element is subject to reciprocal movement material may be drawn in behind the element as the element is extended, and subsequent expelling of this material may be facilitated by the provision of such larger gaps and passages. One or both opposing cleaning element and pocket surfaces may be provided with a draft angle or taper to facilitate the widening of the gap therebetween as the cleaning element is extended.

The radially extendable cleaning element may take any appropriate form and may comprise a rigid member having surface or edge configurations adapted to scrape, mill, or otherwise dislodge material from a cylindrical tubing surface. Surfaces or edges of the element may be formed or coated with wear-resistant materials. Alternatively, or in addition, the cleaning element may include flexible material, such as bristles, brushes or wiping blades.

The tool may comprise multiple blades, which blades may be arranged at an angle to the body axis, that is the blades extend both axially and circumferentially around the body. The blades may collectively define one or more stabilisers. The blades may be separated by bypass flutes. A pocket may be included in two or more of the blades. The pocket may lie on an ellipse, that is an angled cross-section of the body. The pocket, and the associated cleaning element, may have parallel ends and sides and have a substantially rectangular form. Blades may be provided in a set or group, with the individual blades being spaced around a circumference of the body. Alternatively, or in addition, blades, or groups of blades, may be axially spaced along the body. The groups of blades may be circumferentially offset. The blades within a group may have a wrap angle of between 270 and 360° or more; the wrap angle for a blade is the angle from the front of the bottom or leading end of the blade to the back of the top or trailing end of the blade, and the wrap angle for the group is the sum of the wrap angles for each blade in the group. While the term “blades” is used herein, the skilled person will understand that this terminology is intended to encompass a variety of formations typically including a relatively thick body wall portion to accommodate the element-receiving pocket.

The body may be adapted for mounting in or on a tubing string, such as a string of drill pipe, and may be provided with appropriate end connectors, for example threaded connectors, such as pin and box connections. The body may be adapted to form part of a drill string and as such the body is configured to accommodate and withstand the torques and other forces associated with a drilling operation. The body may comprise one or more connected parts. For example, the body may be machined or otherwise formed from a single metal billet or may be from multiple parts.

The blade dimensions may be selected in accordance with the application and will typically be 8-16″ (20.3-40.6 cm) long.

The tool may be incorporated in a drill string and remain in a dormant configuration, with the cleaning element in the retracted position, during tripping in and drilling. Before tripping out or retrieving the drill string the cleaning tool may be positioned at a selected location in the bore and the cleaning element extended to contact the bore wall, which may be the surface of casing or other bore-lining tubing. The cleaning tool is then translated such that the cleaning element moves over the surface, removing or dislodging surface contamination. The cleaned surface may facilitate the subsequent location and sealing of, for example, a liner hanger.

Multiple cleaning tools may be incorporated in a drill string at axially spaced tool locations. The tools may have different cleaning diameters. For example, a distal cleaning tool may describe a smaller cleaning diameter than a proximal cleaning tool, allowing an operator to treat or clean multiple locations in bore-lining tubing of different diameters.

A further aspect of the disclosure relates to a downhole tool comprising; a tubular body defining an internal bore permitting passage of fluid therethrough; first and second actuating members located in the bore; and an occluding member, the occluding member being translatable into engagement with the first actuating member to occlude the body bore and permit creation of a fluid-generated force for translating the first actuating member into engagement with the second actuating member and then translating the second actuating member.

Another aspect of the disclosure relates to a method of actuating a downhole tool, the method comprising: translating an occluding member into a first actuating member located in a body of a downhole tool; creating a fluid-generated force across the occluding member to translate the first actuating member through the body to engage a second actuating member located in the body; and utilising the fluid-generated force to translate the second actuating member through the body.

The tool may comprise a third actuating member and the second actuating member may be translatable into engagement with the third actuating member for translating the third actuating member.

The first actuating member and the second actuating member may comprise sleeves, pipes or tubes.

The first actuating member and the second actuating member may be initially releasably retained relative to the body, for example by shear couplings such as shear pins.

The first actuating member and second actuating member may be initially axially separated or spaced apart and may have opposing surfaces that are initially spaced apart, but which engage when the first actuating member is moved into engagement with the second actuating member.

The first actuating member may be located above the second actuating member in the body.

The tool may comprise a catcher or stop for the first and second actuating members.

The first actuating member and the second actuating member may comprise a coupling or latch arrangement whereby the first and second actuating members are coupled together or may become latched together on the first actuating member engaging the second actuating member.

The first and second actuating members may be axially movable relative to the body.

The tool may further comprise first and second actuatable members mounted on the body, the first actuatable member for cooperating with the first actuating member and the second actuatable member for cooperating with the second actuating member.

The first and second actuatable members may be radially movable relative to the body.

The first and second actuatable members may comprise cam followers, and the first actuating member and the second actuating member may comprise cam members for cooperating with the cam followers.

The first and second actuatable members may comprise cleaning elements.

These aspects of the disclosure may have utility in actuating tools comprising multiple actuatable elements, allowing the elements to be actuated in sequence, rather than simultaneously. The available actuating force may thus be applied to an individual actuatable element, and then to another individual actuatable element, and so on. Alternatively, the available actuating force may be applied to a releasable coupling, such as a shear coupling, and then to induce movement of the actuatable element.

These aspects may be utilised in a cleaning tool as described herein and may also be utilised in a range of other tools featuring multiple elements that require actuation.

The various features of the tools described above and in the appended claims may have utility in combination, and the features may also have individual utility and be provided in tools independently of the other features.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made toFIG.1of the drawings, a schematic of a downhole operation. The figure illustrates a well100that has been drilled from surface102through the earth104to access a subsurface hydrocarbon-bearing formation106. The well100includes a substantially vertical section108and a substantially horizontal section110. The vertical section108and a part of the horizontal section110have been lined with metal tubing in the form of casing112. In practice, it is likely that multiple coaxial casing sections will have been provided in the well, but for ease of illustration only a single casing112is shown. The casing112extends back to the surface102.

The distal portion of the well is provided with a liner114and a liner hanger116is provided at the upper or proximal end of the liner114and has been set to seal and secure the liner114to the lower or distal end of the casing112.

FIG.1illustrates the well100being drilled beyond the end of the liner114. A drill string118carrying a drill bit119has been run into the well100and the drill bit119rotated to extend the well100further through the formation106. The drill string118incorporates two cleaning tools120,122of the present disclosure. The drilling operation locates a smaller diameter distal tool120within the liner114and a larger diameter proximal tool122within the casing112. As will be described, once the drilling operation has finished, the drill string118is partially retrieved to locate the cleaning tools120,122at locations124,126where the liner114and casing112will subsequently be engaged by hangers or seals provided on other apparatus, such as a further liner and a completion. Once positioned in the locations124,126, the cleaning tools120,122are activated, as described in detail below, to extend a plurality of cleaning elements. The drill string118, and thus the tools120,122, are then translated axially through the well100such that the cleaning elements are moved across the surfaces of the liner114and the casing112at the locations124,126to remove or dislodge foreign material from the surfaces. The drill string118is subsequently retrieved to surface102and other apparatus is run into the well100and hangers or seals are set at the cleaned locations124,126.

Accordingly, in this example of the present disclosure the requirement to separately run cleaning or scraping tools into the well100to prepare the locations124,126to receive hangers or seals is avoided. Of course, the retrieval of the activated cleaning tools120,122through the well100will also serve to clean the surfaces of the liner114and the casing112above the locations124,126, and will also serve to ensure the drift diameters of the casing112and liner114, allowing for unobstructed subsequent installation of the next tubing and hangers.

The cleaning tool120will now be described in more detail with reference toFIGS.2to8of the accompanying drawings. The larger diameter cleaning tool122is substantially the same as the tool120but is configured to engage and clean a larger diameter surface.

The tool120comprises a generally cylindrical body130configured for incorporation in the drill string118, and to that end includes appropriate threaded end couplings, an upper box coupling132and a lower pin coupling134. The body130, which has been machined from a single metal billet, defines a through bore136and a body wall138. The bore136accommodates a cam member in the form of an axially translatable pipe140. Externally, the body wall138has been machined to form three axially spaced and circumferentially offset groups of stabiliser blades142,144,146. Each group142,144,146includes three blades148and the blades148within each group are separated by bypass flutes150.

The blades148each extend axially and circumferentially around the body130with a right-handed helix or spiral, and in this example each blade148has a wrap angle (the angle from the front of the bottom or leading end of the blade148ato the back of the top or trailing end of the blade148b) of 90-120°. The wrap angle for each group142,144,146is the sum of the wrap angles for each blade148in the group, that is between 270 and 360°. This provides a clear line of sight through the flutes150between the blades148and facilitates passage of drilling fluid and entrained material, and any material dislodged during a cleaning operation. The blades148of this example are 8-16″ (20.3-40.6 cm) long and feature tapered leading and trailing ends. Some or all of the blades148may be provided with wear-resistant pads or coatings, for example on the leading and trailing edges and on the outer diameter, to enhance blade longevity.

Each blade148defines an external pocket152for receiving a generally rectangular cleaning element154. The pocket152and element154are of complementary shape and dimensions, the element154being a close fit in the pocket152. The pocket sides152a,152band the ends152c,152dare parallel and meet at rounded corners, and a main axis of the pocket152lies on an ellipse, that is an angled cross-section of the body130. The base of the pocket and the opposing inner surface of the element154are substantially planar/flat. The resulting straight-sided pocket152and element154facilitates radial movement of the element154and provides for stability of the element154in the pocket. While a relatively close fit or some other form of close physical engagement between the pocket152and the element154may be desirable to ensure support for the radially extended element154, it may be advantageous to facilitate passage of fluid and material between the pocket152and the element154. For example, the corners of the element154may be cut off to provide passage for fluid and particulate material as the element154moves in and out of the pocket152. As noted above, the gap between the opposing surfaces of the pocket152and the element154may fill with fine particulate material which may increase the friction between the parts and may create a seal between the parts. A seal could prevent the element154from moving radially outwards due to the creation of a vacuum below the element154, and could prevent the element154from moving radially inwards if fluid or material became trapped between the element154and the base of the pocket152; the relatively large area passage created by cutting off the corners of the element154is unlikely to be bridged by fine particulate material and will ensure that fluid and material is not trapped behind the element154.

The pocket152extends into but not through the body wall138, having a substantially planar base156against which a correspondingly shaped inner surface of the element154rests when the element154is in a dormant or radially retracted position; in an active or extended position the inner surface of the element is radially spaced from the pocket base. The body wall138is thus substantially continuous, despite the presence of multiple radially movable cleaning elements154, maintaining the strength and rigidity of the body130.

The element154is urged towards a radially extended position by two coil springs158located in blind bores160formed in the inner face of the element154and engaging the base of the pocket152. In the initial, dormant configuration the springs158are maintained in a compressed condition by a shear pin162which extends between the element154and the internal pipe140. The shear pin162is in a central portion of the element154within a generally cylindrical cam follower in the form of a plunger164. The plunger164is threaded to the inner face of the cleaning element154and extends through a port166in the body wall138. A domed inner end of the plunger164rests on an outer surface of the pipe140, the shear pin162extending through the centre of the plunger164and the domed surface to engage the pipe140. The pin162has a T-section and when fully engaged with the pipe140retains the element154in contact with the base of the pocket152. A circlip168is provided in the plunger164to retain the head of the sheared pin162.

The pin162is sheared by axial movement of the pipe140relative to the body130, the movement being induced by application of an axial force to the pipe140, as will be described in detail below. On shearing the pin162, and assuming there is nothing preventing outwards movement of the element154, the springs158push the element out of the pocket152to extend beyond the outer surface of the blade148. Movement of the element154is restricted by stop members in the form of two pins170which extend through stepped radial bores172in the element and engage with threaded blind bores in the pocket base156.

As was noted above, the cleaning tool120is located on a drill string118and is used in an environment where the tool120is surrounded by drilling fluid carrying fine particulate material. This material will tend to accumulate in and fill spaces and voids in the tool120. This effect may be reduced or minimised by filling voids and spaces with a material such as high-temperature grease or wax, however it is likely that some gaps and spaces will be infiltrated by particulate material. If, for example, particulate material migrates into and fills the narrow gap between the walls of the cleaning element154and the pocket152, it is possible that the extension force provided by the springs158will not be sufficient to extend the element154when the pin162is sheared. Accordingly, the tool120is configured to provide a significant extension force to the element154when the tool120is activated.

The inner domed end of the cleaning element plunger164engages the outer surface of the pipe140. With the tool120in the dormant configuration, the plunger164engages with a lower end of an axial recess or groove174in the pipe140. Nine grooves174are provided in the pipe140and are arranged as three axially spaced groups of three grooves174, each groove174accommodating the inner end of the one of the plungers164of each blade group142,144,146.

The pipe140is in sliding sealing contact with the wall of the body bore136, with upper and lower seals182,184ensuring fluid within the body bore136is isolated from external fluid; during a drilling operation the internal fluid pressure will tend to be significantly higher than the external fluid pressure. A further seal186is provided at an upper end of the pipe140, above a set of bypass ports188in the pipe wall. Initially the pipe140is axially fixed relative to the body by the shear pins162.

To activate the tool120, and release and extend the cleaning element154, the operator drops an occluding member in the form of a ball180into the drill string118. The ball180travels down through the string118until landing in the upper end of the pipe140. The ball180and the seal186allow creation of a differential fluid pressure force across the ball180and when the force reaches a predetermined level, equal or more than the cumulative shear ratings of the nine shear pins162present in the tool120, the pins162are sheared and the pipe140is moved downwards. The grooves174in the pipe140move downwards relative to the plungers164and as the grooves174move beyond the plungers164the cleaning elements154are pushed radially outwards from the body130. The pressure force across the ball180may be significant and will be sufficient to free the cleaning elements154from the pockets152. The springs158may then urge the freed elements154further from the pockets152.

Further movement of the pipe140relative to the body130, until the lower end of the pipe140engages a tool body bore stop190, does not change the position of the cleaning elements154. However, such further translation does move the upper end of the pipe140, the ball180, and the bypass ports188, into an enlarged portion192of the body bore136, such that fluid flowing through the drill string may then bypass the ball180and continue beyond the tool120. Circulation of fluid may be useful to assist with the cleaning operation, assisting in carrying material dislodged by the tool120to the surface. The open passage through the drill string118also allows the string118to self-drain as the string is retrieved.

The larger diameter cleaning tool122may be operated in a similar manner, by dropping a larger diameter ball into the tool122, following activation of the smaller tool120; the dimensions of the cam member/pipe within the tool122are selected such that the smaller ball180used in activation of the tool120will pass through the upper tool122.

FIGS.7and8illustrate a cleaning element154during a cleaning operation. InFIG.7the illustrated element154is located within a substantially vertical well section and the tool body130is substantially coaxial with the surrounding tubing. It will be noted that the inner end of the plunger164has been lifted clear of the surface of the pipe140by the springs158. In such a situation the radial extension of the various elements154provided on the body130is likely to be substantially the same.

InFIG.8, the tool body130is offset from the surrounding tubing, as may occur in an inclined or horizontal well. The body130lies closer to the low side of the well100(the left-hand side of the figure) and is spaced further from the high side of the well (the right-hand side of the figure). In this situation the springs158push the element154on the high side of the well out of the body130far enough to achieve contact with the wall of the surrounding tubing.

Axial movement or reciprocation of the drill string118results in corresponding axial translation of the activated cleaning tools120,122, the extended cleaning elements154scraping the walls of the liner114and the casing112. The arrangement of the elements154is such that full circumferential or 360° contact between the elements154of each tool120,122and the surrounding tubing wall is achieved without requiring rotation of the string118. Where the tools120,122are incorporated in a drill string118, rotation of the string118and tools120,122is likely to be possible, such that the 360° coverage is not critical. However, in other applications the tools120,122may be used, for example, in a dedicated well bore clean-up run where rotation is not available and the ability to achieve 360° coverage is more important.

The skilled person will understand that the dimensions and arrangement of the cleaning tools120,122may vary depending on the application. However, by way of example, the primary dimensions of a cleaning tool120for use in 7″ casing (casing having an outer diameter of 7″ (178 mm)) will be described. The inside diameter of the casing will depend on the casing weight, for example a 26 lbs/ft (38.7 kg/m) casing may have an i.d. of 6.276″ (159.4 mm). The tool120may have an overall length of 7.7 ft (2.35 m) and the blades148may describe a diameter of 5.81″ (148 mm). With the cleaning elements154fully extended the tool120describes a diameter of 6.760″ (172 mm). The external bypass area while dormant within a 7″ (178 mm) 26 lbs/ft (38.7 kg/m) casing is 8.69 in2(5.605 mm2) and while scraping with the cleaning elements154extended is 7.99 in2(5.154 mm2). Each cleaning element is 7″ (178 mm) long and 1″ (25.4 mm) wide and is inclined at 15° to the axis of the tool120. The plunger164is ⅞″ (22.23 mm) in diameter. The port166is slightly larger than the plunger164and as such is less than 1/10thof the area of the pocket base156and thus has no significant effect on the structural integrity of the body130.

The tool120may be arranged to receive a 1.72″ (44 mm) diameter ball180and the tool120may be activated by a pressure across the ball180of 1500 psi (10.3 MPa).

FIGS.9and10of the drawings illustrate an alternative tool220which shares many features with the tool120described above. However, the tool220features a body230formed from multiple parts230a-erather than a single part. Such an arrangement allows a part which has been damaged to be replaced, without having to replace the whole body230.

Reference is now made toFIGS.11and12of the drawings, which illustrate a cam member/pipe340of a further alternative cleaning tool. The pipe340differs from the pipes140,240of the tools120,220described above, in that the grooves374which cooperate with plungers on the sealing elements have different axial extents, in particular the length of the upper or proximal group of grooves374abeing less than the intermediate grooves374b, which are in turn shorter than the lower of distal grooves374c(Length 1<Length 2<Length 3). Thus, once the pipe340has been moved axially downwards relative to the tool body from the initial dormant or inactive position and the cleaning element retaining pins have been sheared, a further first increment of movement will push the plungers of the upper group of cleaning elements outwards, while the plungers of the intermediate and lower group of elements remain in the dormant or retracted position. A second increment of movement will push the intermediate plungers outwards to extend the second group of elements, and a final third increment of movement will extend the lower group of elements.

This staged or staggered operation offers several advantages. The initial movement of the pipe340causes the element retaining pins to shear. In addition to the force required to shear the pins the only other significant resistance to the movement of the pipe340will be the friction between the pipe and the surrounding body. Thus, the operator can predict with a reasonable degree of certainty what level of piston force across the occluded pipe will be required to shear the pins and release the elements. The further first increment of movement only extends the upper group of three elements, such that substantially all the axial force being applied to the pipe340will be effective to urge the upper elements radially outwards. The operator may thus be confident that the elements will be extended and freed from the pockets, even when the clearance gaps between the elements and the pockets have been filled with particulate material. Similarly, the subsequent second and third increments will extend the intermediate group of elements and then the lower or distal group.

It will be apparent to the skilled person that a cleaning tool in accordance with this disclosure may take other forms from those described above. For example, the number and arrangement of blades148, pockets152, and cleaning elements154may be varied.

Reference is now made toFIGS.13to19of the drawings, which are a variety of views of a further alternative cleaning tool420. As will be described, the tool420is provided with an alternative configuration cam member/pipe440that provides for staged release and extension of the elements454associated with each blade group442,444,446.

Rather than a one-piece pipe as provided on the tools described above, this tool420comprises a pipe440that is in three parts, a proximal pipe440a, an intermediate pipe440b, and a distal pipe440c. In an initial configuration, in which the cleaning elements454are retained in a retracted, inactive configuration, opposing end surfaces494of the pipes440a,440b,440care axially spaced apart, with a lower surface494aof the proximal pipe440aspaced apart from an upper surface494baof the intermediate pipe440b, and a lower surface494bbof the intermediate pipe440bspaced apart from an upper surface494cof the distal pipe440c.

Coupling or latch arrangements496are provided between the pipes440a,440b,440c, providing for a degree of relative axial movement between but preventing axial separation of the pipes440a,440b,440c. In particular, the lower end of the proximal pipe440ais provided with latch fingers496afor engaging with an internal profile496baon the upper end of the intermediate pipe440b, and the lower end of the intermediate pipe440bis provided with latch fingers496bbfor engaging with an internal profile496con the upper end of the distal pipe440c.

The outer surface of each pipe440a,440b,440cincludes three recesses474for receiving the inner domed ends of the plungers464of the cleaning elements454associated with the respective blade group442,444,446. The recesses474each further include a blind bore to accommodate the inner end of a shear pin462.

The upper end of the proximal pipe440ais profiled to receive an occluding member in the form of a dart or ball480. Upper and lower seals482a,482bare provided on the exterior of the pipe440ato provide a sliding seal with the inner surface of the tool body bore436and isolate the ports466in the tool body436that accommodate the plungers464. Corresponding seals are also provided on the exterior of the intermediate and lower pipes440b,440c. The upper end of the proximal pipe440ais of slightly larger diameter than the remainder of the pipe440aand features a further exterior seal486, and the transition between the different diameter pipe portions forms a shoulder498which, as will be described, is engageable with a stop490formed by the lower end of an enlarged bore portion492surrounding an upper portion of the pipe440a, for retaining the pipe440awithin the tool body bore436. The upper end of the pipe440afurther includes elongated bypass ports488which, when the pipe440ahas been axially translated, permit fluid to flow around the occluding ball480.

The tool420differs from the tools120,220in other respects, as will now be described.

Each cleaning element454is urged radially outwardly by four coil springs458, rather than two springs as with the tool120described above. The springs458engage the base of the respective pocket. The bores460that accommodated the springs458also feature smaller-diameter passages461providing fluid communication with the outer face of the element454thus reducing the likelihood of the elements454being pressure-locked in the pockets452. The passages461open into grooves463which extend across the width of the elements454to provide scraping edges to enhance the cleaning effect provided by the elements454. A shallow wear-indicating groove465extends axially along the outer face of each element454between the two intermediate scraper grooves463.

Further, the radial extension of each element454is controlled by a pair of retaining pins470which extend across the stabiliser blades448, between the pocket sides452a,452band through respective radial slots472provided in the element454. The arrangement for retaining the shear pins462within the elements454is also slightly different, with the shear pin-retaining circlip468being provided in a more readily accessible location adjacent the outer surface of the element454, with a cylindrical rod469being provided within the element bore471between the circlip468and the head of the pin462.

FIG.19illustrates a cleaning element454and illustrates the 30° taper at the upper and lower edges of the element454, which assists in the collapse or radially inwards compression of the elements454when the activated tool420is being pushed or pulled through the casing and encounters a diameter change or a restriction. Further, the depth/height of the elements454is reduced at the leading and trailing corners455to mimic the helical form of the adjacent stabiliser blades448; as with the tool120described above, the cleaning elements454are generally rectangular and feature a flat/straight lower surface and straight sides, and in the absence of the depth/height reduction the corners455would extend proud of the helical blades448. With the illustrated cleaning element and pocket configuration there is no requirement for the base of the cleaning element to be provides with a complex curved form to allow cooperation with an external cam surface on the pipe440. In the retracted configuration the flat lower surface of each element engages the corresponding surface of the corresponding pocket452. Such surfaces are relatively easy to machine and provide for stable mounting of the retracted element in the pocket.

The tool420is operated in a generally similar manner to the tools described above. When it is desired to activate the tool and extend the elements454, the operator pumps the ball480from surface and into the tool420, to land on the upper end of the pipe440a, as illustrated inFIG.14. It is likely that the momentum of the ball480, and the column of fluid travelling behind the ball480, will generate a downwards axial force sufficient to shear the three pins462engaging the pipe440aand move the pipe440adownwards. Further downwards movement of the pipe440aalso moves the recesses474downwards relative to the associated plungers464, thus pushing the plungers464, and the associated elements454, radially outwards. The elements454associated with the first blade group442are thus extended/activated, and may then be moved further radially outwards, above the surface of the adjacent stabiliser blades448, by the action of the springs458.

The downwards axial movement of the pipe440abrings the lower surface494aof the proximal pipe440ainto contact with the upper surface494baof the intermediate pipe440b. Further downwards movement of the pipe440anow also results in downwards movement of the intermediate pipe440b. The momentum of the ball480and the following fluid column will still likely be sufficient to generate a downwards axial force sufficient to shear the three pins462engaging the pipe440band move the pipe440bfurther downwards to move the pipe recesses474downwards relative to the associated plungers464, thus pushing the plungers464, and the associated elements454, radially outwards. The cleaning elements454associated with the second blade group444are thus extended/activated.

This is then repeated for the distal pipe440c, the continuing downwards axial movement of the pipes440a,440bbringing the lower surface494bbof the intermediate pipe440binto contact with the upper surface494cof the distal pipe440c. The pipes440a,440b,440cmove downward together and shear the three pins462engaging the pipe440cand move the pipe440cfurther downwards to move the pipe recesses474downwards relative to the associated plungers464, thus pushing the plungers464, and the associated cleaning elements454, radially outwards. The elements454associated with the third blade group446are thus extended/activated.

Further downwards axial movement of the coupled pipes440a,440b,440cis prevented by the shoulder498engaging the stop490.

In use, it is likely that the pipes440a,440b,440care moved, and the elements448of the three blade groups extended, in quick succession, without any operator intervention, immediately following the ball480landing in the upper end of the pipe440a. However, in other operations, the ball480may drop or be pumped more slowly into the tool420. The operator may then build up pressure above the ball480sufficient to move the proximal pipe440aand extend the proximal cleaning elements454. The operator may then choose to operate the tool420with only the proximal elements454extended. More likely the operator will continue to apply pressure to the ball480and the occluded pipe440ato move and release the other pipes440b,440c, and release and extend all the elements454.

This arrangement for actuating the cleaning elements454reduces the magnitude of the forces required to fully activate the tool420, by separating the initiation of movement of the pipes440a,440b,440c. Thus, movement of the proximal pipe440arequires the static friction associated with achieving movement of the relatively short length of pipe440aand associated parts to be overcome, together with the shearing of the three associated pins462. Once these forces have been overcome the proximal pipe440awill move relatively easily and urge the plungers464, and the associated elements454, radially outwards. Once the elements454associated with the first blade group442are extended/activated the forces being applied to the ball480and the pipe440aare then effectively dedicated to the release and translation of the intermediate pipe440band its associated elements454. Similarly, once the cleaning elements454associated with the intermediate pipe440bhave been extended, the coupled pipes440a,440bwill move relatively easily and the forces being applied to the assembly are effectively dedicated to the release and translation of the distal pipe440cand the extension of the associated cleaning elements454.

The use of multiple pipes440a,440b,440cto provide a cam member to actuate the tool420facilitates manufacture of the tool420. The individual pipes440a,440b,440care machined separately and substantially without reference to the other pipes. On the other hand, manufacturing a one-piece pipe such as the pipes140,240,340described above requires nine spaced-apart recesses and associated elements to be accurately located relative to one another and to the corresponding elements mounted on the tool body. This requires the machining and assembly of the tool to comply with very fine tolerances and can substantially increase manufacturing costs.

The illustrated example provides three actuating members in the form of the pipes440a,440b,440c, but in other examples only two actuating members could be provided, or four of more actuating members could be provided.

In another example the separate pipes may not be coupled or latched together and may land on a stop or restriction provided in the tool body bore below the lowermost pipe.

In another example, seals may be provided between the cleaning elements and the pockets, and the inner faces of the elements may be arranged to experience internal tool pressure, allowing pressure to be utilised to urge the cleaning elements outwards. Furthermore, seals may be provided between the plungers and the surrounding body ports to prevent ingress of fluid and material from the exterior of the tool into the tool bore, or to permit the plungers to act as pistons and urge the elements radially outwards in response to internal tool pressure.

The illustrated examples use a fluid pressure force-actuated cam member to shear the cleaning element retaining pins and provide an initial cleaning element-extending/releasing force. The extending force may be useful to free the cleaning elements from the pockets should the gaps between the elements and the pockets become packed with material. Once freed from the pockets, the springs may provide for further radial movement of the cleaning elements. As noted above, a pin-shearing or element-extending force may also be provided using the difference in pressure between the interior and the exterior of the body by providing seals on the plungers or the elements and exposing the inner sides of the plungers or elements to internal pressure. In such a situation the radial movement induced by the hydraulic pressure differential may be restricted to prevent the hydraulic pressure urging the elements into contact with the tubing, as this could potentially provide an excessive extending force. This may be achieved by restricting the radial movement of a pressure-activated plunger and permitting the element to move radially outwards of the plunger, for example by providing a flexible link between the plunger and the element or allowing the element to move radially outwards independently of the plunger. The plunger may be stepped or otherwise configured to limit or restrict radial movement.

In a further example of the disclosure a tool may be provided without a cam and may rely solely on hydraulic pressure to control and extend the cleaning elements.

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