Swivel

Abstract

Two relatively rotatable, fluid conducting members of a swivel are interconnected by an improved assembly which includes a washpipe, mounting sleeves for connecting opposite ends of the washpipe to the fluid conducting members, and a tandem packing arrangement in at least one of the sleeves. A port formed in the sleeve containing the tandem packing arrangement communicates with the axial space separating the packings. Means are also provided for selectively locking each sleeve to the washpipe so that the packing in either sleeve can be made to function as a static seal or a dynamic seal depending on the position of the locking means. The improved washpipe assembly in one embodiment permits the swivel to be operated through two stages, and in another embodiment, through three stages before the packing must be replaced.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an assembly for interconnecting two relatively rotatable, fluid conducting members of a swivel. In one aspect, it relates to an improved washpipe assembly for use in drilling swivels.

2. Description of the Prior Art

In oilfield drilling operations which employ rotary drilling techniques, drilling fluid is circulated through the drill string and up the borehole returning to the system pit or tanks. The drilling fluid serves several important functions such as cooling the bit, carrying the cuttings away from the bit, plastering the borehole wall to prevent sloughing or caving of formations, and providing a hydrostatic head for controlling the influx of formation fluids. The swivel which is an essential component in all rotary drilling systems functions to rotatably support the drill string and to deliver drilling fluid to the rotating drill string. The swivel typically comprises a stationary support housing suspended on the drilling rig hoisting equipment and a tubular stem journaled to the housing. The housing, thus, rotatably supports the stem which in turn supports the drill string suspended in the well. A tube, referred to as a washpipe, interconnects the flow course of the stationary housing and the interior of the rotating stem and serves to conduct fluid from the stationary portion to the rotating portion of the swivel. The tube is normally secured to the stationary portion of the swivel with a static seal provided at the joint. In such an arrangement, relative rotation is between the tube and the swivel stem. A dynamic seal is required at this joint. In operations, the dynamic seal almost always fails before the static seal. When this occurs, the drilling operations must be interrupted and the washpipe assembly repacked or, alternately, replaced. Although most commercial swivels are designed to permit rapid interchange of washpipe assemblies, under certain operating conditions, the interruption of mud circulation or pipe movement even for short periods of time increases the risk of sticking the drill string. Under such conditions, it is desirable to continue drilling operations until it becomes necessary to replace the drill bit. Bit replacement requires withdrawing the drill string from the borehole. With the drill string out of the hole, the swivel washpipe assembly can be safely repacked or, alternatively, the complete assembly can be replaced.

SUMMARY OF THE INVENTION

The present invention provides an improved assembly for use in drilling swivels and similar devices where it is desired to interconnect two relatively rotatable, fluid conducting members in a fluid tight assembly. In a preferred embodiment, the improved assembly comprises a tube, mounting sleeves for connecting opposite ends of the tube to the stationary and rotating members of the swivel, a tandem packing arrangement mounted in one sleeve, packing mounted in the other sleeve, and means for selectively locking either sleeve to the tube. The tandem packing arrangement, preferably, includes two sets of self-energizing seal rings positioned in the sleeve to provide axially spaced sealing intervals. A port formed in this sleeve communicates with the space separating the axially spaced packings of the tandem packing arrangement. Means such as a plug or valve are also provided for closing the port. As discussed in detail below, the second set of packing rings remain essentially deactivated in the unloaded condition but becomes activated under hydraulic loading. The port and port closing means control the loading on the second set of seal rings.

The combination of the tandem packing arrangement and selectivity offered by the sleeve locking means permits the swivel to be operated through two stages and, preferably, through three stages with a different packing providing the dynamic seal in each stage. Tests have shown that the assembly of the present invention permits the swivel to be operated for a substantially longer time than possible with prior art swivels before the packing must be replaced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a drilling swivel with portions cut away to illustrate details of the washpipe assembly.

FIG. 2 is an enlarged sectional view of the washpipe assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in connection with a rotary drilling swivel, but it should be understood that the invention can also be applied in other systems where it is desired to couple two relatively rotatable, fluid conducting members in a fluid tight assembly.

As shown in FIG. 1, the main components of a swivel include an outer stationary body 10 having an inlet flow course 11 formed therein, a tubular stem 12 journaled to the body 10, a washpipe assembly 13 for interconnecting the flow course 11 and the interior of the stem 12, and a bail 14 for suspending the swivel on the drilling rig hoisting equipment.

The swivel body 10 is normally fabricated from three steel castings: a lower main housing 15, a housing cap or "bonnet" 16, and a fluid inlet connecting member 17. The parts 15, 16, and 17 normally are made separately and assembled as a unit by bolts or other fasteners. The fluid inlet connecting member 17, referred to in the art as a "gooseneck," defines the flow course 11 and is provided with a threaded outer end 18 for attachment to the drilling hose (not shown). The flow course 11 discharges through a downwardly opening projection 19, the lower end of which is threaded for connection to the washpipe assembly 13.

The stem 12 extends through the main housing 15 and has an upper threaded end 20 projecting above a closure plate 21 of cap 16. The stem 12 extends downwardly through the lower end of housing 15 terminating in a threaded end 22. The kelley joint and the remainder of the drill string are suspended from end 22.

A flange 23 secured to the stem 12 is journaled to an internal shoulder 24 of housing 15 by means of a thrust bearing 25. Upper and lower radial bearings 26 and 27 maintain the stem 12 in proper axial alignment within housing 15. The housing 15 is normally filled with oil to provide lubrication for bearings 25, 26, and 27.

The swivel thus comprises two relatively rotatable, fluid conducting members, e.g. connecting member 17 and stem 12, which must be coupled together in a fluid tight assembly. This is the function of the washpipe assembly 13.

The washpipe assembly 13 interconnects the downwardly extending projection 19 of member 17 and the upwardly projecting end 20 of stem 12. This assembly includes a washpipe 28, mounting sleeves 29 and 30 for connecting the washpipe 28 to the swivel, and packing mounted in each of the sleeves 29 and 30 to provide a seal about the outer periphery of the washpipe 28. The washpipe 28 is normally a short, hardened steel tube smoothly ground to minimize packing wear. The components of the washpipe assembly 13 are generally fabricated as a unit to permit replacement of the entire assembly when the packing fails.

As shown in FIG. 2, the upper and lower sleeves 29 and 30 and packings contained therein are similar in structure, although they need not be. The upper sleeve 29 includes a cylindrical body portion 33 and an end wall 34 having an opening 35 formed therein. The sleeve 29 surrounds an upper end portion of the tube 28, the clearance between the outer periphery of the tube 28 and the end wall 34 being sufficient to permit relative rotation of the two members. The interior of the sleeve 29 is provided with a pair of cylindrical surfaces 36 and 37 interconnected by a radial shoulder 38. These surfaces in combination with the outer periphery of the tube 28 define an annular space 39. The diameter of the cylindricad cylindrical 36 is larger than the diameter of the cylindrical surface 37 so that the radial dimension of the upper portion of the annular space 39 is substantially larger than that of the lower portion. The upper sleeve is provided with a tandem packing arrangement which includes an upper seal ring assembly 40 and a lower seal ring assembly 41. The seal rings of each assembly are sized to fit in sealing relationship in the sleeve 29. The tandem packing arrangement thus provides pressure seals at axially spaced intervals along washpipe 28. A thrust ring 42 engaging radial shoulder 38 separates the two seal ring assemblies 40 and 41. The thrust ring 42 which can be made of steel or other relatively hard metal serves to bear the hydraulic loading imposed on the upper assembly 40. The thrust ring 42 and end wall 34 provide means for separately supporting packings 40 and 41.

A vent shown as radial port 43 formed in sleeve 29 communicates with the axial space separating the seal ring assemblies 40 and 41 and provides means for relieving the pressure in that space. The outer end of the port 43 can be counterbored and threaded for receiving a plug or, alternatively, a valve. As described in more detail below, the vent port 43 and means for closing the vent port permit the seal ring assemblies 40 and 41 to function at different stages in the operation. Initially, the port 43 is open so that leakage of fluid past the upper seal ring assembly 40 bleeds to atmosphere. This prevents the buildup of pressure within that portion of the sleeve 29 which houses the lower seal ring assembly 41. The absence of pressure in this space prevents the lower seal rings from being energized. These seal rings in the unstressed condition thus are not subjected to severe wear as are the hydraulically loaded seal rings of assembly 40.

The sleeve 29 is adapted to be connected to the projection 19 by means of a packing nut 46. A face seal such as an 0-ring can be provided at the joint.

The lower sleeve 30 surrounding a lower end portion of tube 28 can be similar in structure to sleeve 29, having cylindrical body 47, an end wall 48, and a pair of internal cylindrical surfaces 49 and 50. The surfaces 49 and 50 in combination with the outer periphery of the washpipe 28 define an annular space 51. The diameter of surface 50 is larger than that of surface 49, with radial shoulder 52 interconnecting the two surfaces. A tandem packing arrangement comprising seal ring assemblies 53 and 54 is mounted in the sleeve 30. The tandem packing arrangement in the manner described above functions to provide axially spaced sealing intervals along the washpipe 28. A port 59 formed in the sleeve 30 communicates with axial space separating the seal ring assemblies 53 and 54. The outer end of the port 59 can be counterbored and threaded for receiving a plug or valve. A thrust ring 55 bears against the radial shoulder 52 and thus prevents hydraulic loading on packing assembly 53 from being imposed on packing assembly 54. The thrust ring 55 and end wall 48 provide means for separately supporting packings 53 and 54.

The lower sleeve 30 is connected to the upper end 20 of stem 12 by means of a packing nut 56, with a face seal being provided at the joint. Also included in the assembly, is a retainer 57 clamped between the sleeve 30 and the stem end 20. The retainer 57 maintains the washpipe 28 at the proper elevation in the assembly. In order to permit communication of fluid to the interior of the sleeve 30, the retainer 57 can be provided with several ports, two illustrated as 58.

As mentioned previously, the washpipe assembly 13 can be constructed as a unit. The unit is installed by placing the assembly between the confronting projections 19 and stem end 20, and then securing the packing nuts 46 and 56 to the mating threads provided in projection 19 and stem end 20.

An important feature of the present invention is the provision of means for controlling washpipe rotation. This feature in combination with the tandem packing arrangement, described previously, substantially increases the operating life of the washpipe assembly. The means for controlling washpipe rotation include set screws 61 and 62 which, respectively, extend through end portions of sleeves 29 and 30. The set screws 61 and 62 are threaded to sleeves 29 and 30, respectively, so that upon tightening either set screw, the sleeve associated therewith is locked to the washpipe 28. In the retracted position of the set screws 61 and 62, the washpipe 28 is detached from both sleeves 29 and 30. The washpipe 28 will remain stationary with sleeve 29 or rotate with sleeve 30 depending on the drag forces imposed on it by the packing assemblies. In accordance with the one aspect of the present invention, the washpipe 28 can be made to remain stationary with sleeve 29 by placing set screw 61 in the engaged position and set screw 62 in the retracted position as illustrated in FIG. 2. Alternatively, the washpipe 28 can be made to rotate with the lower sleeve 30 by reversing the positions of the set screws 61 and 62.

As mentioned previously, each of the seal ring assemblies 40, 41, 53, and 54 provide a pressure seal between the washpipe 28 and its associated mounting sleeve. The seal rings indicated by reference 65 may be of the type conventionally used in washpipe assemblies. These rings are generally molded from fiber reinforced elastomers in the form of "V" rings, "U" rings, "W" rings and the like. Such rings are self-energizing; that is, pressure tends to deform the rings placing them in sealing engagement with the confining walls of the space to be sealed. For high pressure surface, each seal ring assembly, in addition to the conventional seal rings, can include a plastic ring 63 and an anti-extrusion ring 64. The anti-extrusion ring fits into a recess formed in the plastic ring and bears against the end wall of the associated sleeve as in assemblies 41 and 54 or against the retainer 42 and 55 as in assemblies 40 and 53. The conventional self-energizing seal ring engaging the plastic rings of each ring assembly is provided with a flat surface to distribute the load thereon. The plastic rings can be made from any plastic bearing material including nylon, fluoroplastics, acetal and polycarbonate resins. The fluoroplastics, particularly polytetrafluoroethylene, are preferred, however, because of their low coefficient of friction, anti-stick properties, and high temperature resistance.

The anti-extrusion ring 39, preferably, is machined from a relatively soft bearing metal such as bronze, bronze alloy, copper alloy, and the like.

The packing assembly illustrated in the drawings can be operated through three stages. Initially, the washpipe assembly 13 is placed in operation with both of the vents 43 and 59 open and with the set screws 61 and 62 placed in the retracted position. The washpipe 28 is thus free to rotate with the sleeve 30 or remain stationary with sleeve 29, depending upon the drag forces imparted by the packing assemblies. Assuming that the drag forces are such to cause the washpipe 28 to rotate with the sleeve 30, the upper packing 40 of sleeve 29 functions as a dynamic seal and the lower packing 53 of sleeve 30 functions as a static seal. It should be noted that seal rings of assemblies 41 and 54 are not energized since the retainer rings 42 and 55 bear the hydraulic loading imposed on assemblies 40 and 53. Also, leakage of fluid past assemblies 40 and 53 escapes through ports 43 and 59, respectively. This prevents the buildup of pressure which would energize the seal rings. It should also be noted that although the seal rings are designed to provide an interference fit in the space being sealed, the rings in the unstressed condition are not subjected to severe wear as are rings in the loaded condition. The swivel is operated until the dynamic seal provided by the seal rings of assembly 40 becomes so worn that excessive leakage begins occurring. This will be indicated by excessive discharge of fluid through port 43. Without interrupting drilling operations, the washpipe assembly can be placed in condition for the second stage by simply closing port 43 with plug 66 and tightening set screw 61. In the second stage, the washpipe 28 remains stationary with the sleeve 29, the ring assembly 41 providing a static seal between the sleeve 29 and the washpipe 28. With the vent 43 closed, hydraulic pressure in the space separating the packing assemblies 40 and 41 energizes the packing 41 creating a fluid seal in the lower portion of annular space 39. The packing 53 in sleeve 30 in the second stage of operation functions as a dynamic seal since the sleeve 30 and packing ring assembly 53 contained therein revolve about the lower portion of the washpipe 28. With the vent 59 open, the rings of assembly 54 are not energized. Consequently, the seal rings of this assembly do not become worn by the relatively moving parts.

When the seal rings of assembly 53 becomes so worn that the fluid seal is no longer maintained, the operations are momentarily interrupted to place the washpipe assembly 13 in condition for the third stage. The vent 59 is closed with plug 67; set screw 61 is placed in the retracted position; and set screw 62 in the engaged position. In the third stage of operation, the washpipe 28 rotates with sleeve 30 with the packing assembly 54 providing a static seal therebetween. The packing assembly 41 functions as a dynamic seal between the relatively rotating sleeve 29 and washpipe 28. The swivel can be operated until the packing rings of the packing assembly 41 become so worn that the fluid tight seal is no longer maintained. At this time, the washpipe assembly 13 must be repacked or replaced.

In another embodiment of the invention, only one of the sleeves, e.g. sleeve 29, is provided with the tandem packing arrangement and the other sleeve, e.g. sleeve 30, with a single packing. In such an arrangement, the washpipe assembly 13 can be operated through two stages. In the first stage, the set screws 60 and 61 will be positioned such that relative rotation occurs between the washpipe 28 and sleeve 29. The assembly 40 thus functions as a dynamic seal and the packing in sleeve 30 as a static seal. When seal rings of assembly 40 fail, the positions of the set screws 60 and 61 can be reversed and the port 43 closed placing the washpipe assembly in condition for the second stage operation. In this stage, the single packing in sleeve 30 functions as a dynamic seal and the second packing assembly 41 of the tandem packing arrangement functions as a static seal.

It is preferred, however, that the tandem packing arrangement be provided at both ends of the washpipe because of the advantages derived from one additional stage.

Claims

We claim:

1. An assembly for interconnecting a pair of relatively rotatable, fluid conducting members which comprises:

a tube;

a first sleeve surrounding a portion of one end of said tube and being adapted for connection to one of said members;

first and second packings mounted in said sleeve and being arranged therein to provide fluid seals between said sleeve and said tube at axially spaced intervals;

means within said first sleeve for separately supporting said first and second packings;

port means in said first sleeve for venting the space between said packings;

means for selectively closing said port means;

a second sleeve surrounding a portion of the other end of said tube and being adapted for connection to the other of said members;

a packing mounted in said second sleeve for providing a fluid seal between said sleeve and said tube; and

means for selectively locking said first and second sleeves to said tube.

2. The invention as recited in claim 1 wherein said first and second packings each include self-energizing seal rings.

3. The invention as recited in claim 2 wherein each of said packings includes a ring of deformable resin and a metal anti-extrusion ring, said anti-extrusion ring being positioned adjacent the minimum gap between said sleeve and said tube in the sealed interval to prevent the extrusion of the resin ring.

4. An assembly for interconnecting a pair of relatively rotatable, fluid conducting members which comprises:

a tube;

first and second mounting sleeves for connecting opposite ends of said tube to said members, said sleeves being secured to said members and said tube being relatively rotatable with respect to said sleeves;

first and second packings mounted in each of said sleeves for providing fluid seals between each of said sleeves and said tube at axially spaced intervals;

means in each of said sleeves for separately supporting said first and second packings;

port means in each of said sleeves for venting the space between said first and second packings contained therein;

means for selectively closing each of said port means; and

means for selectively locking each of said sleeves to said tube.

5. The invention as recited in claim 4 wherein said first and second packings in each of said sleeves each includes a plurality of self-energizing seal rings.

6. In a swivel having two relatively rotatable, fluid conducting members interconnected by a washpipe assembly including a washpipe and sleeves for mounting the washpipe to said members, said washpipe being relatively rotatable with respect to both of said sleeves, the improvement wherein one of said sleeves contains a tandem packing for sealing the space between said one sleeve and said washpipe at axially spaced intervals, means for supporting each packing of said tandem packing within said one sleeve; port means in said one sleeve for venting the space between the packings of said tandem packing means mounted in the other of said sleeves for sealing the space between said other sleeve and said washpipe.

7. The invention as recited in claim 6 wherein said packing includes a second tandem packing for sealing the space between said other sleeve and said washpipe at axially spaced intervals, port means in said other sleeve for venting the space between the packings of said second tandem packing, and means for selectively closing said port means.

8. A washpipe assembly for use in a drilling swivel having a stationary inlet conduit and a rotating tubular stem which comprises:

a washpipe;

an upper sleeve for connecting the upper end of said washpipe to said stationary inlet conduit;

first and second packing assemblies positioned in said upper sleeve to fluid seal the radial space between said upper sleeve and said washpipe at axially spaced intervals;

means in said upper sleeve for separately supporting said packing assemblies contained therein;

port means in said upper sleeve for venting the space between said packing assemblies contained therein;

means for selectively closing said port means in said upper sleeve;

a lower sleeve for connecting the lower end of said washpipe to said rotating tubular stem;

first and second packing assemblies positioned in said lower sleeve to fluid seal the radial space between said lower sleeve and said washpipe at axially spaced intervals;

means in said lower sleeve for separately supporting said packing assemblies contained therein;

port means in said lower sleeve for venting the space between said packing assemblies contained therein;

means for selectively closing said port means in said lower sleeve; and

means for selectively locking said upper and lower sleeves to said washpipe.