WO2015160261A1

WO2015160261A1 - Wiper apparatus for pipes

Info

Publication number: WO2015160261A1
Application number: PCT/NO2015/050068
Authority: WO
Inventors: Ketil Oddvar BOTNMARK; Kjell Mikalsen
Original assignee: 2K Tools As
Priority date: 2014-04-14
Filing date: 2015-04-14
Publication date: 2015-10-22

Abstract

The present invention relates to a wiper apparatus (1) for cleaning the inside of a drill string of drilling mud or other well fluids during drilling operations, wherein the apparatus (1) is made to float on a liquid surface of the drilling mud in the drill string (20) or be suspended from a landing seat (10), wherein the landing seat is arranged in a landing sub (21), wherein the apparatus (1) comprises a landing member (2), at least one buoyancy body (3), at least one centering element (4), and at least one wiper member (5, 6, 7). The wiper apparatus (1) comprises a spacer (9) between an upper (30) and lower (31) portion of the apparatus (1), wherein the spacer (9) has such a length that the buoyancy body (3) and the centering element (4) will not be located in the landing sub or tool joint when the wiper apparatus (1) is suspended from or rests against the landing seat, the buoyancy body (3) and the centering element (4) being arranged in a lower portion (31) of the apparatus (1) and the landing member (2) being arranged in an upper portion (30) of the apparatus (1).

Description

Wiper apparatus for pipes

The present invention relates to an apparatus for cleaning a drill string of drilling mud and other fluids during tripping of the drill string.

During drilling for hydrocarbons offshore and onshore, it will be necessary at regular intervals to pull up the drill string having a bit or another tool affixed thereto. The drill string consists of coupled drill pipes, and when the drill string is pulled out, lengths of three coupled drill pipes are usually extracted at once and placed in a piperack. These, usually three, pipes are called a stand. The pulling out (tripping) is performed by pulling the drill string up and breaking it stand by stand or pipe by pipe until the whole drill string is pulled out.

In drilling operations, problems often occur due to drilling mud remaining inside drill pipes after pulling up the drill string, caused by poor or lack of cleaning. The mud dries and forms hard flakes and lumps. When the drill pipes are used again, the lumps and particles may be pumped down to the drill bit where they may clog one or more of the nozzles, with the consequence that the drill bit may be damaged. It is also likely cause problems with downhole tools and engines. In addition, large amounts of waste mud will often end up on the drill deck and on decks in storage areas. This creates unnecessary work with cleaning of decks, deposit of waste, and injuries caused by slippery and soiled decks.

In US 4287948, a wiper for use in a drill string is described. The wiper floats in the drilling fluid, and during tripping a peripheral ledge on the device wipes the inner wall of the drill string clean of fluid. The apparatus is provided with a mass and a volume such that it can float during tripping on a liquid surface of the drilling mud in the drill string. The apparatus comprises wiper devices.

WO 2006/006872- Al describes internal removal of drilling mud from a drill string by use of a bellows-shaped wiper being attached with weight and volume so that it floats on the surface of the drilling mud in the drill string during tripping. The wiper has at least one channel for allowing drilling mud to pass through. US 4.671.358-Al describes wiper plugs which are used in cementing procedures, where the wiper part lands and is fixated in a landing shoulder so that the wiper halts and opens a valve for allowing the cement to flow downwards through the valve.

A catalogue description from TAM International Inc. , 2005 (http://www.tamintl.com) discloses a product "Dart Catcher" with built-in landing profile, so that the wiper lands on a landing seat.

However, when the wiper is used in connection with tripping, situations may occur where the pumps must be activated in full speed, while the wiper is still inside the drill string. As a result, the wiper is pumped downwards until it might be stopped in the drill string, for example 5000 meters downwards. Further, it is an important requirement that the pumping of drilling mud shall continue unhindered, even after the wiper has come to a halt in the drill string.

To meet the challenges in relation to such situations where the pumps are reactivated, it is vital that this does not constitute a hindrance for the drilling fluids which are to be pumped through the drill string. It is also vital that the wiper apparatus is not pumped all the way down to a potential bottom hole assembly, for instance a drill bit, and causes damage there. In addition, it is not desirable that the wiper apparatus is pumped out of the drill string and goes astray down in the well, which might result in damages as well as complicated fishing operations. To avoid pumping the wiper apparatus down into the bottom hole assembly or out of the drill string, a so-called landing sub comprising a landing seat may be mounted. The landing seat may beneficially be formed as an integral part of the longitudinal bore in the landing sub, or alternatively be inserted loosely in the same bore. An embodiment of such a landing seat is discussed in NO 330743. The landing sub is advantageously mounted in the drill string by use of thread connections.

To ensure that drilling mud can flow as freely as possible past a wiper apparatus located in the drill string, a landing cone which is arranged to seat itself in a landing seat according to NO 330743 may be supplied with a central bore which is in connection with a central bore extending longitudinally through the wiper. The landing cone may further be designed with a number of flow channels which reduce the flow area past the landing cone/seat as little as possible. Below the landing cone, the drill pipe has a constriction, a so-called tool joint, which makes the flow area smaller than further down the drill pipe, where the diameter is larger.

Even with the measures that are provided in order to ensure that conventional wiper apparatus to the least possible extent shall prevent drilling mud from passing through the drill pipe, the problem remains that conventional wiper apparatus reduce the flow area excessively when located in the drill string. The drill operators want as little loss of flow as possible over the wiper device, and with smaller drill pipes with smaller ID, loss of flow over the wiper device must be further reduced if they are to be used.

The object of the present invention is to alleviate the above-mentioned problems in a simple way.

According to the present invention, a wiper apparatus is provided for cleaning a drill string of drilling mud during tripping of the drill string according to the characterizing part of independent claim 1.

Alternative or advantageous embodiments are disclosed in the dependent claims.

The invention will now be explained in further detail with reference to the

accompanying figures which display examples of advantageous embodiments of the invention:

Fig. 1 shows an embodiment of the present invention on the inside of a drill string, Fig. 2 shows the same embodiment as fig. 1, but with a different location in the drill string,

Fig. 3 shows an upper portion of an embodiment of the present invention,

Fig. 4 shows the same as fig. 3, slightly more detailed,

Fig. 5 shows a part of a lower portion of an embodiment of the present invention, and Fig. 6 shows a part of a lower portion of an alternative embodiment of the present invention.

A typical embodiment of the wiper apparatus 1 according to the invention is shown in figure 1. The wiper apparatus 1 comprises a landing member 2, a buoyancy body 3, one or more centering elements 4 and a number of wiper members 5, 6, 7. In figure 1, the wiper apparatus 1 is located in a drill string 20, the drill string 20 being inserted in a landing sub 21. The illustration is reduced/compressed for convenience. It will be understood that the individual elements that are cut through and contracted may be shorter.

Buoyancy body 3 may be tubular and may for example have an outer diameter of approx. 2/3 of the inner diameter of the drill string. The buoyancy body 3 may be made of metal, a metal alloy or a composite material. In an advantageous embodiment, the buoyancy body 3 may be made of aluminum. The buoyancy body 3 may be provided with bursting members 8 (see figure 3) which are made to burst if the pressure in the drill string exceeds a predetermined pressure. Thereby, such bursting members 8 ensure that the buoyancy body 3, which normally will be hollow and filled with air, will not collapse if the pressure in the drill string increases. The pressure in the drill string will increase, for example, if one starts to pump fluids through the drill string.

The wiper apparatus 1 may comprise one or more centering elements 4 which for example are provided in an upper and lower portion of the wiper apparatus 1; 30, 31, respectively. The terms "upper" and "lower" refer to a conventional vertical orientation of a drill string; however, a diagonal or horizontal orientation is also contemplated. In figure 1, only one set of the centering elements 4 is shown, these being provided on the lower portion 31 of the wiper apparatus 1. In the embodiment shown in figure 1, the wiper members 5, 6, 7 will be able to function as centering elements for the upper portion of the wiper apparatus 1. In figure 6, the centering element consists of a wiper member instead of more conventional centering elements.

According to the present invention, the wiper apparatus 1 comprises a spacer 9 between the upper and lower portion of the wiper apparatus 1. This spacer 9 comprises a rod or pipe element having a diameter which is significantly smaller than the smallest ID of the drill string (as previously mentioned, the smallest ID of the drill string is often at tool joint 22, i.e. the constrictions of the inside of the drill string at each joint of each drill pipe). The tool joint 22 itself often comprises thicker material, which results in a smaller inner diameter. The spacer 9 is provided with such a length that the lower portion of the wiper apparatus 1 will be located where the drill string has the largest ID when the upper portion of the wiper apparatus 1 is located in tool joint 22. The advantage of this embodiment is particularly evident when the wiper apparatus 1 is seated in a landing seat 10 and fluids need to be pumped down through the drill string. Since the tool joint 22 is located directly below the landing seat 10, the spacer 9 contributes to the lower portion of the wiper apparatus 1 being located in a part of the drill string with the largest ID. Such a situation is shown in figures 1, 3 and 4. The conventional wiper apparatus are compact enough so that the entire or parts of the buoyancy body, centering elements etc. will be located in tool joint 22 or in the landing sub 21. It will be understood that a landing sub also comprises a tool joint. In addition, a landing sub often has the same reduced flow area through tool joint 22, which then may be highly restricted. If the drill string is of a smaller type, the flow area through tool joint 22 will be unacceptably small if a space-demanding tool is located there as well. With a correctly adjusted spacer 9, the flow area will increase for normal drill pipes, and also allow the use of a wiper apparatus 1 in drill strings of a smaller type (with smaller ID).

The lower portion of the wiper apparatus 1 may comprise a nose piece 11 which for example may be coated with a shock-absorbing material.

The upper portion 30 of the wiper apparatus 1 comprises a landing member 2 which is designed to seat itself in a landing seat 10. The landing member 2 may be conical in shape or have any other suitable design. The landing member 2 is further designed not to block flow through the drill string, for instance by having flow channels 12 which give the largest possible flow area past the landing member. An example of how the flow channels 12 may be designed in the landing member is shown in figures 3 and 4. Alternatively, or additionally, the landing member 2 may be designed to allow fluids to flow on the outside of the landing member 2 when it is placed in the landing seat 10. Likewise, the landing seat 10 may be designed to reduce the flow area past the landing seat 10 as little as possible, both with and without the landing member 2 of the wiper apparatus 1 in place in the landing seat 10. For example, instead of the landing seat 10 forming a full ring, it may comprise a suitable number of, e.g. three or more, appropriately designed pegs, cams, longitudinal rails or slits arranged on the inside of a landing sub 21. A possible embodiment comprising longitudinal pegs is shown in figure 4.

The number of wiper members 5, 6, 7 arranged may be adapted according to need. It may be appropriate to arrange wiper members 5, 6, 7 with such a spacing that only one, or max. two, of the wiper members 5, 6, 7 are located in the tool joint when the wiper apparatus 1 passes. Figures 3 and 4 show two wiper members 5, 6 in the tool joint / landing sub. This will help reduce the risk that the wiper apparatus 1 becomes stuck. Further, the wiper members 5, 6, 7 may be designed with different diameters adapted to the normal ID of the drill string, the reduced ID through the tool joint and possibly the even more reduced ID through the landing sub, respectively.

As mentioned earlier, the tool joint 22 itself often comprises thicker material, which results in a smaller inner diameter. A potential smaller wiper member having a smaller outer diameter will be better suited to wipe drilling fluid residues from this smaller, inner diameter. One of the two wiper members shown in figures 3 and 4 may therefore have a smaller diameter adapted to the smallest ID of the drill string 20.

The wiper members may typically be made of polyurethane, HNBR or another flexible and chemically resistant material which allows the shape of the wiper device to change and maintain its wiper function even in cases where the inner diameter of the drill string varies slightly.

In use, the apparatus 1 is placed in a drill string 20 with an internal surface when tripping (breaking) of the drill string is to be initialted/performed. The drill string contains mud / drilling fluid with a drilling fluid surface, and possibly residues of hydrocarbons, cement, salt water etc. The buoyancy body 3 of the wiper apparatus 1 is provided with a mass and a volume adapted so that the device will stay afloat on the drilling fluid surface. The weight of the wiper apparatus ensures that it falls down to the liquid surface and places the peripheral ledge of the bottom wiper member at a short distance (for example at least approx. 10-15 cm) above the liquid surface.

As the drill string is lifted, the wiper apparatus will always stay on the liquid surface and wipe off the drilling mud that sticks to the inner surface of the drill string.

According to one embodiment of the wiper apparatus 1 of the present invention, the length may be approx. 4 m. A typical total weight of the wiper apparatus 1 may be approx. 5 kg. It will be understood that lengths as well as weights may be varied and adapted to the actual use and any special applications.

Figure 2 shows a situation where the landing member 2 of the wiper apparatus 1 is not in the landing seat. In this case, the length of the spacer 9 should be adapted so that the upper portion 30 and the lower portion do 31 not simultaneously pass respective tool joints 22. This also applies to the case where the landing member 2 of the wiper apparatus 1 is in the landing seat. In that case, the length of the spacer 9 should be adjusted so that the lower portion 31 is located in an area of the drill string between two tool joints 22.

Because the wiper apparatus 1 at all times will be located on top of the liquid surface, removing the wiper apparatus 1 during tripping of the drill string 20 will normally be easy. Generally, the liquid surface will be slightly above the drill deck when tripping starts. The liquid surface will fall as the drill string is pulled out because the fluid in the well in which the drill string 20 is located will take up the volume that the drill string 20 previously occupied.

If the liquid surface is so low that the wiper apparatus 1 is hard to catch for the operator, retrieving equipment suited for this purpose may be used to retrieve the apparatus 1.

According to an embodiment, the wiper apparatus 1 may be provided with a fish neck or other types of devices for coupling and attachment of fishing equipment for retrieving the apparatus.

Drilling mud has a varying self -weight. Accordingly, a favourable embodiment of the apparatus may have replaceable weights / weight elements or varying buoyancy of the buoyancy body 3.

Claims

C l a i m s

1.

Wiper apparatus (1) for cleaning the inside of a drill string of drilling mud or other well fluids during drilling operations, wherein the apparatus (1) is made to float on a liquid surface of the drilling mud in the drill string (20) or be suspended from a landing seat (10), wherein the landing seat is arranged in a landing sub (21), wherein the apparatus (1) comprises a landing member (2), at least one buoyancy body (3), at least one centering element (4), and at least one wiper member (5, 6, 7),

c h a r a c t e r i z e d i n t h a t the wiper apparatus (1) comprises a spacer (9) between an upper (30) and lower (31) portion of the apparatus (1), wherein the spacer (9) has such a length that the buoyancy body (3) and the centering element (4) will not be located in the landing sub or tool joint when the wiper apparatus (1) is suspended from or rests against the landing seat, the buoyancy body (3) and the centering element (4) being arranged in a lower portion (31) of the apparatus (1) and the landing member (2) being arranged in an upper portion (30) of the apparatus (1).

2.

Wiper apparatus (1) according to claim 1, wherein the length of the spacer (9) is adapted to the drill pipes in the drill string (20), so that the buoyancy body (3) is below the tool joint when the wiper apparatus (1) is located in the landing seat.

3.

Wiper apparatus (1) according to claim 2, wherein the length of the spacer (9) is between ¼ and ¾ of the length of a drill pipe used in the drill string (20).

4.

Wiper apparatus (1) according to claim 1, wherein at least one of the wiper members (5, 6, 7) has a diameter adapted for wiping of a reduced ID in the drill string (20).

5.

Wiper apparatus (1) according to claim 1, wherein one or more of the wiper members (5, 6, 7) function as centering elements (4).

6.

Wiper apparatus (1) according to claim 1, wherein the landing member (2) is provided with flow channels (12).

7.

Wiper apparatus (1) according to claim 6, wherein the spacer (9) has a diameter which results in a flow area in the drill string that is equal to or larger than flow area past the landing member (2), which is provided with flow channels (12).

8.

Wiper apparatus (1) according to claim 1, wherein the buoyancy body (3) comprises bursting members (8).