WO2015022667A2

WO2015022667A2 - Washpipe joint for an oil drilling plant

Info

Publication number: WO2015022667A2
Application number: PCT/IB2014/063923
Authority: WO
Inventors: Nunzio D'orazio; Ignazio CATALANO
Original assignee: Meccanotecnica Umbra S.P.A.
Priority date: 2013-08-14
Filing date: 2014-08-14
Publication date: 2015-02-19
Also published as: WO2015022667A3; ITTO20130694A1; EP3194706A2

Abstract

Washpipe joint (1) for an oil drilling plant comprising a fixed sleeve (2) adapted to be connected to a fixed conduit (3) for feeding the drilling fluid, a rotating sleeve (4) adapted to be connected to a rotating conduit (5) integral with a drilling set, and a pair of sealing rings (27, 28) integral with the fixed sleeve (2) and with the rotating sleeve (4), respectively, and cooperating with each other sliding axially under the thrust of elastic means (40) to form the seal between the fixed sleeve (2) and the rotating sleeve (4), characterized in that the sealing rings (27, 28) are arranged externally coaxial to a main conduit (60) defined by respective internal conduits (2a, 4a) coaxial and axially facing each other of the fixed and movable sleeves (2, 4) and are touched by a fraction of the flow rate of the drilling fluid through an auxiliary branch (64) connected in parallel to the main conduit (60); the main conduit (60) is convergent-divergent, and the auxiliary branch communicates with an area of minimum section of the main conduit (60) to facilitate the recall of the fraction of flow rate in the main conduit (60).

Description

"WASHPIPE JOINT FOR AN OIL DRILLING PLANT" TECHNICAL FIELD

The present invention relates to a washpipe joint for an oil drilling plant.

BACKGROUND ART

As is known, oil drilling is carried out by means of a rotating drilling set, comprising a plurality of hollow tubes or rods modularly connectable to one another, carrying at one end a cutting tool or chisel.

The rods are hollow and are used, in addition to pulling the chisel in rotation, to feed the drilling fluid in the cutting zone. The drilling fluid has various functions, including removing and transporting the cutting material generated by the chisel, cooling and lubricating the drilling set and preventing the collapse of the inner walls of the well. The drilling fluid (typically water- based, but also sometimes oil- or gaseous-based) is fed to the drilling set through a piping that leads into a fixed conduit coaxial to the drilling set, and a rotating conduit integral with the drilling set. The seal between said conduits, axially facing each other, needs therefore to be implemented .

To this end, a device is used which is called "washpipe joint" comprising, according to a known solution, a fixed sleeve configured to be connected to the fixed conduit, a rotating sleeve configured to be connected to the rotating conduit, a pair of sealing rings integral with the fixed sleeve and the rotating sleeve, respectively, and cooperating with each other frontally, sliding under the thrust of elastic means to achieve the seal between the fixed conduit and the rotating conduit.

Examples of washpipe joints of this type are described in EP-A-1 630 347 and WO2009/133115, which describe the features of the preamble of claim 1.

A problem associated with known washpipe joints is the relatively high frequency of works for the replacement of the sealing rings, which are subjected to the abrasive action of the drilling fluid and high operating temperatures. Since each plant shutdown is extremely expensive, increasing the duration of the sealing ring is a primary aim of this technology field.

Another problem associated with the prior art is that the sealing rings are exposed to the entire flow rate of fluid that runs through the seal; therefore, in case of leaks, a considerable leakage difficult to control may occur, with dispersion of the fluid in the surrounding area .

DISCLOSURE OF INVENTION

Therefore, the object of the present invention is to provide a washpipe joint of an improved type, which allows solving the drawbacks mentioned above. The object above is achieved with a washpipe joint according to claim 1.

BRIEF DESCRIPTION OF THE DRAWING

For a better understanding of the present invention, a preferred embodiment is described hereafter by way of non- limiting example only and with reference to the accompanying drawing, in which figure 1 shows an axial section thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the single figure, reference numeral

1 indicates as a whole a washpipe joint comprising an upper fixed sleeve 2 adapted to be fixed to a fixed conduit 3 for feeding the drilling fluid (schematically and partially shown) and a lower rotating sleeve 4 adapted to be fixed to the rotating conduit 5 (also only schematically and partially shown) . Sleeves 2, 4 are coaxial with each other and have respective internal conduits 2a, 4a arranged axially facing each other so as to define as a whole a main conduit 60 which connects the fixed sleeve 2 to the rotating conduit 3.

The fixed conduit 3 and the rotating conduit 5 define respective fixed planes PS and PI which delimit them downwards and upwards, respectively, and define the mounting constraints of seal 1, as will be described hereafter in greater detail.

The fixed sleeve 2 is substantially bell-shaped with a hollow cylindrical upper portion 6 and a lower portion 7 which internally forms a housing 8 having a greater diameter than the inner surface of the upper portion 6. A nut ring 9, which forms an outer annular flange 10, is externally tightened on an upper end of the upper portion.

A nut ring 13 is externally coaxially mounted on the upper portion 6, with freedom of axial movement, adapted to be tightened on the fixed conduit 3 to sealingly lock onto the same, acting axially against flange 10, a head surface 11 of the upper portion 6, provided with a front seal 12. In use, surface 11 lies in plane PS.

The rotating sleeve 4 has an outer thread 17 at the lower end thereof, on which an annular flange 18 is tightened, provided at the bottom with a front seat 19 for centering the rotating conduit 5, the purpose thereof will be clarified hereafter. A nut ring 21 provided with an internal thread 22, adapted to the connection with the rotating conduit 5, is fixed below flange 18 by a plurality of screws 19. Threads 17, 22 have such a direction as to oppose to the unscrewing in the direction of rotation of the rotating conduit 5. The rotating sleeve 4 is delimited at the bottom by a surface 23, which is adapted to cooperate with the head of the rotating conduit 5, with the interposition of a second front seal 12.

The rotating sleeve 4 has an intermediate annular projection 24, on which an annular rotating support 25 rests axially, rotationally integral with it thanks to a plurality of axial pins 26. The rotating support 25 accommodates a first sealing ring 27, which is rotationally integral with the rotating support 25, and thus with the rotating sleeve 4, conveniently by means of radial forcing.

The first sealing ring 27, or rotating ring, slidingly cooperates in axial manner with a second sealing ring 28, or fixed ring, mounted on a fixed support 29 mounted with possibility of axial sliding within housing 8 of the fixed sleeve 2 and externally coaxial to an upper end of the rotating sleeve 4, with which it delimits an annular passage 31.

More particularly, the fixed support 29 is substantially bell-shaped, with an upper tubular portion 30 sealingly accommodated in housing 8 and a lower flange portion 32, axially facing the lower portion 7 of the fixed sleeve 2. The fixed sealing ring 28 is mounted in a lower seat 33 of the flange portion 32 and is integral therewith, for example by means of welding or a mounting with interference. The flange portion 32 conveniently has an internal annular cooling chamber 34 which communicates with an inlet hole 35 and with an outlet hole 36 adapted to be connected by means of respective connecting flanges 37, 38 to respective feeding and discharge pipes of an external cooling circuit (not shown) . In order to make the annular chamber 34, the flange portion 32 of the fixed support 29 is conveniently made in two parts welded together, for example a flange 32a integral with the tubular portion 30 and an annular shaped end plate 32b connected to flange 32 by welding. Chamber 34 conveniently has an L-shaped section so as to surround as closely as possible the fixed sealing ring 28.

The fixed support 29 is pushed downwards, that is, towards the rotating support 25, by a plurality of springs 40 accommodated in a plurality of seats 41 equally angularly spaced of the lower portion 7 of the fixed sleeve 2 and prestressed so as to exert an axial thrust on the flange portion 32 of the fixed support 29. In this way, the sealing rings 27, 28 are kept in mutual contact under an axial load of predetermined intensity. A predetermined axial clearance is present between the fixed sleeve 2 and the fixed support 29.

Seal 1 finally comprises a mechanism 44 adapted to allow the axial contraction of the seal itself to allow the removal and mounting thereof between the fixed planes PS and PI.

Mechanism 44 is of the screw-nut type and comprises a first nut ring 45 with male screw function, slidingly mounted on the rotating sleeve 4 below the annular projection 24 and provided with a plurality of blind holes 46 for the actuation through a dedicated operating key, and a second nut ring 47 with female screw function, arranged externally coaxial with the first nut ring 45 and with the annular projection 24 and rigidly connected to the fixed sleeve 2 by a cylindrical wall 48 which encloses the entire sealing assembly 49 defined by the fixed and movable supports 25, 29 and the relative sealing rings 27, 28.

The cylindrical wall 48 is fixed to the lower portion 7 of the fixed sleeve 2 by a plurality of screws 50, and is fixed to the second nut ring 47 by a plurality of screws 51.

The cylindrical wall 48 defines a casing 53 with the flange portion 7 of the fixed sleeve 2 and with nut ring 47, accommodating the sealing assembly 49. Casing 53 is closed except for a pair of opposite radial holes 52 of the cylindrical wall 48 to allow the passage of the connecting flanges 37, 38. Nut ring 47 has an upper conical wall 54 sloping outwards, defining a collecting duct 55 with the cylindrical wall 48 for any leakage of drilling fluid from the sealing assembly 49. Such leakage may be discharged through drain holes 56 made in the cylindrical wall 48 at the bottom of collecting duct 55.

The internal conduit 4a of the rotating sleeve 4 is convergent-divergent and has a geometric throat section 61 lying substantially in the plane of contact between the sealing rings 27, 28. These latter are arranged externally coaxial and at a certain radial distance with respect to the rotating sleeve 4, it defining an annular chamber 62 connected to conduit 4a by a plurality of holes 63 which open into an area of minimum section of conduit 4a. Holes 63 are preferably slightly inclined, so as to flow into conduit 4a in an effective throat section, as is known arranged slightly downstream with respect to the geometric throat section 61. The annular passage 31, the cooling chamber 34 and holes 63 define an auxiliary branch 64 of the drilling fluid circuit, connected in parallel to the main conduit 60.

The operation of seal 1 is as follows.

In use, the fixed sleeve 2 is rigidly connected to the fixed conduit 3 and the rotating sleeve 4 is rigidly connected to the rotating conduit 5 and rotates with it.

The drilling fluid is fed from the fixed conduit 3 to the rotating conduit 5 through the main conduit 60 formed by the fixed sleeve 2 and by the rotating sleeve 4.

A fraction of the flow rate is taken upstream of the effective throat section of conduit 4a, passes through the annular passage 31 and reaches chamber 62, where it lubricates and cools the sealing rings 27, 28, and is recalled inside conduit 4a through holes 63 due to the reduced pressure that is created in the throat section of conduit 4a.

In this way, the drilling fluid touches with continuity and in a controlled manner the sealing rings 27, 28, ensuring proper lubrication of the sealing surfaces and contributing to the removal of the heat that is generated by friction.

A further contribution to the cooling of the sealing rings 27, 28 is provided by chamber 34, connected to a water cooling circuit. This allows improving the thermal behavior of the sealing assembly 49, and thus its duration.

If any leaks should occur between rings 27 and 28, the fluid would collect in the collecting duct 55 and would not be dispersed. Moreover, since the flow rate affected by possible leaks is only the fraction that touches rings 27, 28, such leaks would in any case be small.

The mounting/removal operations of seal 1 are finally described hereafter.

As mentioned above, in use the fixed sleeve 2 is connected to the fixed conduit 3 by the nut ring 13 and the rotating sleeve 4 is connected to the rotating conduit by nut ring 21 and flange 18.

The mounting and removal operations must be carried out without removing the fixed and rotating conduits; therefore, seal 1 must be inserted/removed transversely within the space between the fixed planes PS and PI, which constitute fixed constraints.

Nut ring 13 is slidable with respect to the fixed sleeve 2 and can therefore be retracted along the upper portion 6 of the fixed sleeve 2 below the upper fixed plane PS. Flange 18 is instead fixed rigidly to the rotating sleeve 4, thus the maximum axial dimension of seal 1, excluding that of the nut ring 21 which may be preassembled (upon mounting) or left (upon removal) on the rotating conduit 5, consists of the axial distance H between the lower plane of flange 18 and the upper surface 11 of the fixed sleeve 2.

Such a distance H, in the mounting condition shown in figure 1, is greater than distance HO between the fixed planes PS and PI; in order to allow inserting/removing seal 1 radially from the plant without removing conduits 3, 5, distance H must be reduced to less than H₀.

To do so, mechanism 44 is used and, in particular, nut ring 45 is screwed into nut ring 47 by a wrench that engages holes 46.

When nut ring 45 comes into axial abutment against projection 24 of the rotating sleeve 4, it can no longer advance axially; continuing the rotation of nut ring 45, is produced an axial translation downwards of nut ring 47 with which the fixed sleeve 2 is integral through the cylindrical wall 48. This allows lowering the fixed sleeve 2, compressing springs 40, until distance H is less than Ho .

Starting from the above condition, the sequence of mounting operations is as follows:

- tighten nut ring 21 on the rotating conduit 5;

- insert seal 1 transversely between the fixed planes PS and PI, centering it on the rotating conduit 5 by means of seat 19;

fix flange 18 on nut ring 21 by means of screws 20;

- rotate (unscrew) nut ring 45 to return the washpipe joint 1 to its working height with the upper surface 11 of the fixed sleeve 2 in axial contact with the fixed conduit 3; and

- raise nut ring 13 and tighten it on the fixed conduit 3.

The removal sequence, substantially reverse to the previous one, is as follows:

- unscrew nut ring 13 from the fixed conduit 3 and lower it along the fixed sleeve 2;

- rotate (tighten) nut ring 45 to reduce the height of the washpipe joint 1;

- remove screws 20;

- disengage seat 19 from the rotating conduit 5 and remove seal 1.

An examination of the features of the washpipe joint 1 made according to the present invention clearly shows the advantages that it allows obtaining.

Firstly, the sealing rings are not impinged by the entire flow rate of the drilling fluid, but only by a fraction of the flow rate. However, thanks to the use of the convergent-divergent geometry of the conduit, the fraction of flow rate that touches the sealing rings exerts a continuous, controlled and effective lubrication and cooling of rings 27, 28.

The cooling action of chamber 34 contributes to the optimization of the thermal behavior of the sealing assembly 49, increasing the useful life of the sealing rings 27, 28.

Moreover, in case of leakage, the leaks are only small and are collected in the collecting duct 55, from which they can be discharged in a controlled manner without dispersion in the surrounding area.

Finally, the mounting and removal of the washpipe joint 1 are fast and simple thanks to the use of mechanism 44.

Claims

1. A washpipe joint for an oil drilling plant comprising a fixed sleeve (2) adapted to be connected to a fixed conduit (3) for feeding drilling fluid, a rotating sleeve (4) adapted to be connected to a rotating conduit (5) integral with a drilling set, the fixed and rotating sleeves (2, 4) defining respective internal conduit (2, 4) coaxial and axially facing each other so as to form as a whole a main conduit (60) for drilling fluid, and a pair of sealing rings (27, 28) integral with the fixed sleeve (2) and the rotating sleeve (4) and axially sliding in cooperation with each other under the thrust of elastic means (40) to obtain the seal between the fixed sleeve (2) and the rotating sleeve (4), characterized in that the sealing rings (27, 28) are arranged externally coaxial with the main conduit (60) and are contacted by a fraction of the flow rate of drilling fluid through an auxiliary branch (64) connected in parallel to the main conduit (60), the main conduit (60) being convergent-divergent, the auxiliary branch communicating with an area of minimum section of the main conduit (60) to facilitate the recall of the fraction of flow rate in the main conduit (60), and by comprising a cooling chamber (34) adjacent to said sealing rings (27, 28) and adapted to be connected with a cooling circuit.

2. The washpipe joint according to claim 1, characterized in that the cooling chamber (34) is formed in a first annular support (29) housing one (27) of the sealing rings (27, 28) .

3. The washpipe joint according to claim 2, characterized in that the support (29) is annular and is carried by the fixed sleeve (2) in a position externally coaxial with the rotating sleeve (4) so as to form therewith an annular passage (31) which is part of the auxiliary branch (64) and communicates with the main conduit (60) upstream of said area of minimum section (61) .

4. The washpipe joint according to claim 3, characterized in that the auxiliary branch comprises an annular chamber (62) adjacent to the sealing rings (27, 28), which communicates with said annular passage (31) and with said area of minimum section (61) .

5. The washpipe joint according to one of claims 2 to 4, characterized in that another (28) of said sealing rings (27, 28) is housed in a second annular support (25) rigid with and carried by the rotating sleeve (4) .

6. The washpipe joint according to claim 5, characterized in that said elastic means consist of a plurality of springs (40) compressed between the fixed sleeve (2) and the first annular support (29) to exert on the latter an axial thrust towards the second annular support (25) .

7. The washpipe joint according to one of the preceding claims, characterized by comprising an external casing (53) which encloses the sealing rings (27, 28) and forms a collecting duct (55) for collecting possible leakage .

8. The washpipe joint according to one of the preceding claims, characterized by being configured to be mounted between fixed planes (PS, PI) defined respectively by the fixed conduit (3) and the rotating conduit (5), and by comprising a device (44) configured to reduce the axial dimensions of the washpipe joint (1) for the purposes of assembly and disassembly of said fixed plans (PS, PI) .

9. The washpipe joint according to claim 8, characterized in that said device (44) is a screw-nut type.

10. The washpipe joint according to claim 9, characterized in that said device (44) comprises a first nut ring (45) with a male screw function coaxially arranged with respect to the rotating sleeve (4) and a second nut ring (47), with a female screw function, rigidly connected to the fixed sleeve (2), the rotating sleeve (4) defining an axial stop (25) for the first nut ring (45) so that a tightening of the first nut ring (45) in the second nut ring (47) produces an axial approach of the fixed sleeve (4) with respect to the rotating sleeve (4) .

11. The washpipe joint according to claims 7 and 10, characterized in that the connection between the second nut ring (47) and the fixed sleeve (2) is made by way of a cylindrical wall (48) fixed between said second nut ring (47) and to a flange portion (7) of the fixed sleeve (2) and defining therewith said outer casing (53) which encloses the sealing rings (27, 28) .

12. The washpipe joint according to claim 11, characterized in that said collecting duct (55) for collecting possible leakage is defined between the second nut ring (47) and the cylindrical wall (48) .

13. The washpipe joint according to claim 11, characterized in that the second nut ring (47) has a conical upper surface (56) sloping towards the cylindrical wall (48) and forming therewith the collecting duct (55) .

14. The washpipe joint according to claims 2 and 12 characterized in that said cylindrical wall (48) has a pair of holes (52) for the passage of connecting flanges (37, 38) from the cooling chamber (34) to the cooling circuit.