US20120055677A1

US20120055677A1 - Rotating flow control diverter with riser pipe adapter

Info

Publication number: US20120055677A1
Application number: US13/222,813
Authority: US
Inventors: Michael Boyd
Original assignee: Individual
Current assignee: ELITE ENERGY HOLDINGS Ltd; ELITE ENERGY IP HOLDINGS Ltd
Priority date: 2010-08-31
Filing date: 2011-08-31
Publication date: 2012-03-08
Also published as: CA2751179A1

Abstract

The present invention is directed a rotating flow control diverter having a riser adapter. The riser adapter allows the rotating flow control diverter to be positioned in a riser string below the drilling platform. The rotating flow control diverter has two flanged connections that connect to the flanged connections of riser pipe such that the rotating flow control diverter becomes an integral part of the riser string. The rotating flow control device has means to circulate lubricating fluid in the bearing assembly without the need for external feed lines.

Description

FIELD OF THE INVENTION

The invention relates to a wellhead apparatus for well control and more particularly to an apparatus used to control and divert drilling and wellbore fluids and gases, and produced gas and solids during drilling and other operations, which connects to a rig riser.

BACKGROUND

In offshore drilling, the riser is a pipe that extends from the drilling platform down to the seafloor. Drilling mud and cuttings from the borehole are returned to the surface through the riser. The top of the riser is attached to the drillship, while its bottom is secured at the seafloor. A blowout preventer (BOP) stack is placed at the seafloor between the wellhead and the riser to provide protection against overpressured formations and sudden release of gas. The riser pipe diameter is typically large enough to allow the drillpipe, logging tools and multiple casing strings to pass through.
It is conventional to also have a BOP stack at the head of the riser and to mount a rotating blowout preventer or rotating flow control diverter at the top of the BOP stack. The rotating flow control diverter serves multiple purposes such as sealing pipe which moves in and out of the wellbore while allowing rotation of same. Typically a rotating flow control diverter consists of rubber strippers or sealing elements and an associated hollow quill that rotates with the drill string within a robust housing. Rotation of the strippers and the hollow quill is facilitated by a bearing assembly having an inner race rotates that with the drill string and an outer race that remains stationary with the housing. The bearing assembly is isolated from wellbore fluids and gases by seals.
The rotating flow control diverter may also divert fluids such as drilling mud, produced fluids, and surface injected air or gas into a recovery line. It is desirable that a rotating flow controller diverter last as long as other components and not be the reason operations are interrupted and result in non-productive time.
If the ability to maintain adequate lubrication of the bearings of a rotating flow control diverter is compromised, the bearings will fail quickly. Maximizing the longevity of the bearings is therefore a key objective in the design of rotating flow control diverter equipment. Conventionally, most bearing lubrication means require that a lubricant be injected or pumped into an annulus which houses the bearings to provide lubrication. Such lubrication systems may require elaborate external hydraulic mechanisms and seal arrangements to ensure adequate lubrication. U.S. Pat. No. 5,662,181 to Williams et al. and U.S. Pat. No. 6,244,359 to Bridges et al. both describe a variety of means to lubricate the bearing assembly of a rotating flow head.
While the use of a rotary flow control diverter at the top of the riser provides a pressure seal between the external environment and the well bore, its position at the head of the riser can be problematic. If the blow out preventer fails, or if there is a sudden release of gas or pressurized fluid into the riser pipe, control of the pressurized gas or fluid occurs at the level of the drilling platform. This can result in exposure of the drilling platform to danger and damage. For example, gas that is being released through a control port to relieve pressure may ignite resulting in an explosion.
Accordingly, there is a need for a rotary flow control diverter that can be used to create an additional pressure seal between the wellbore and the external environment which can be positioned in the riser string below the drill platform. It would be preferable if the apparatus could be maintained remotely, and if the device had a sealed bearing assembly that is relatively simple and robust. It would be advantageous if, in one embodiment, the improved rotating control flow diverter had means to efficiently circulate lubricating fluid within the sealed bearing without the need for an external hydraulic pumping system.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, the invention comprises a rotating flow control diverter for use in a riser string comprising;

- a) a tubular stationary housing having a lower flanged connection;
- b) a removable bearing assembly, the bearing assembly comprising an outer housing, bearing elements, and an axially rotatable inner tubular shaft;
- c) an elastomeric stripper element attached to the inner tubular shaft; and
- d) a locking clamp mounted on the outer housing for releasably securing the outer housing of the bearing assembly to the stationary housing; and
- e) a riser pipe adapter comprising;
  - i. a sleeved housing comprising an upper enclosure having a flanged connection for attachment to a flange of a riser pipe section and a lower enclosure, the lower enclosure being mounted on the stationary housing; and
  - ii. a locking clamp for releasably attaching the upper enclosure to the lower enclosure.

In one embodiment, the locking clamp for releasably securing the outer housing of the bearing assembly to the stationary housing comprises a locking clamp ring rotatably mounted on the outer housing. In another embodiment, the locking clamp ring for releasably securing the outer housing of the bearing assembly to the stationary housing further comprises locking tabs that align with complementary locking tabs on the stationary housing.
In one embodiment, the locking clamp for releasably attaching the upper enclosure to the lower enclosure comprises a locking clamp ring mounted on the lower enclosure and in a further embodiment, a hydraulic cylinder actuates the locking clamp ring for releasably attaching the upper enclosure to the lower enclosure into a locked position.
In one embodiment, the rotating flow control diverter further comprises an interchangeable flange on the stationary housing. In one another embodiment, the interchangeable flange comprises an upper flange defined by the stationary housing and a second flange that is releasably secured to the upper flange. In another embodiment, the lower enclosure is defined by the stationary housing. In one embodiment, the bearing assembly comprises;

- (a) an outer housing and an axially rotatable inner tubular shaft, the outer housing and the axially rotatable inner tubular shaft defining an annular space between them;
- (b) a sealed fluid chamber disposed in the annular space, the fluid chamber containing lubricating fluid;
- (c) bearing elements disposed within the fluid chamber, the bearing elements radially and axially supporting the inner tubular shaft; and
- (d) at least one fan ring mounted on and rotating with the inner tubular shaft in a position such that fan ring is disposed within the fluid chamber whereby rotation of the fan ring causes circulation of the lubricating fluid within the fluid chamber.

In another embodiment of the present invention, the invention comprises a method of inserting a rotating flow control diverter having an upper end and a lower end into a riser string, the rotating flow control diverter having a flanged connection at its lower end, the method comprising the steps of;

- (a) mounting a sleeved riser adapter on the upper end of the rotating flow control diverter, the adapter having a flanged connection;
- (b) securing the flanged connection at the lower end of the rotating flow control diverter to the flanged connection of a riser pipe; and
- (c) securing the flanged connection of the adapter at the upper end of the rotating flow control diverter to the flanged connection of a riser pipe.

In one embodiment of the method, the flanged connection located at the lower end of the rotating flow control diverter is connected to the stack of a blow out preventer.
In another embodiment of the present invention, the invention comprises a riser pipe adapter for a rotating flow control diverter, comprising;

- (a) a sleeved housing defining an interior pressure bearing cavity, the housing comprising;
  - i. an upper enclosure having a flanged connection for sealed attachment to the flange of a riser pipe; and
  - ii. a lower enclosure, the lower enclosure being attached in a sealed manner to the rotating flow control diverter;
- (b) a clamp for releasably attaching the upper enclosure to the lower enclosure in a sealed manner.

In another embodiment of the present invention, the invention comprises an offshore drilling assembly comprising a riser string and a rotating flow control diverter, said riser string comprising a plurality of interconnected lengths of flanged riser pipe and the rotating flow control diverter inserted in the riser string between a first flanged riser pipe and a second flanged riser pipe, the rotating flow control diverter comprising;

- a. a tubular stationary housing having a lower flanged connection, the lower flanged connection being attached to the first flanged riser pipe;
- b. a removable bearing assembly, the bearing assembly comprising an outer housing, bearing elements, and an axially rotatable inner tubular shaft;
- c. an elastomeric stripper element attached to the inner tubular shaft;
- d. a locking clamp ring rotatably mounted, on the outer housing for releasably securing the outer housing of the bearing assembly to the stationary housing; and
- e. a riser pipe adapter comprising;
  - i. a sleeved housing comprising an upper enclosure having a flanged connection, said flanged connection being attached to the second flanged riser pipe, and a lower enclosure, the lower enclosure being mounted on the stationary housing; and
  - ii. a locking clamp ring for releasably attaching the upper enclosure to the lower enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like elements are assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention. The drawings are briefly described as follows:

FIG. 1 is a view of one embodiment of a rotating flow control diverter in longitudinal cross-section.

FIG. 2 is a cutaway view of the bearing assembly and lubricating chamber, showing a fan ring of one embodiment.

FIG. 3 is a partial cutaway view showing a lock ring in place over the outer bearing housing.

FIG. 4 is a transparent view of a lock ring showing the locking tabs.

FIG. 5 is a diagrammatic view of one embodiment of the riser pipe adapter.

FIG. 6 is a view of one embodiment of a rotating flow control diverter and a riser adapter in longitudinal cross section.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention relates to a rotating flow control diverter having a riser pipe adapter. When describing the present invention, all terms not defined herein have their common art-recognized meanings. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. The following description is intended to cover all alternatives, modifications and equivalents that are included in the spirit and scope of the invention, as defined in the appended claims.
In this application, the term “lubricating fluid” and “lubricant” are used to interchangeably to refer to the lubricant used to cool and lubricate the bearings of a rotating flow control diverter. It can be understood that the lubricant employed with the present invention may be any suitable fluid lubricant, including, without limit, oil.
In the oil and gas industry offshore drilling operations conducted on the sea floor require the use of riser. A riser is a string of pipe that extends from the drilling platform down to the sea floor. The drilling platform may comprise a floating rig or a drill ship, or any like platform employed by the offshore drilling industry.
Once an initial wellbore has been established in the sea bed and casing has been cemented into place in the wellbore, a blow out preventer (BOP) is landed on and secured to the well head. The BOP is connected to the riser which extends to the surface. The BOP is tested following which drilling operations commence through the riser in an incremental manner. Drill pipe is lowered down through the riser and drilling mud is injected down through the drill pipe. Drilling mud and cuttings from the borehole are returned to the surface through the annular space between the riser and the drill pipe.
The riser string is comprised of sections of riser pipe that are flanged at each end. The flanged ends are secured by bolts, welds or both. The rotating flow control diverter of the present invention has an adapter facilitating insertion of the rotating flow control diverter between sections of riser pipe.
A rotating flow control diverter generally comprises a stationary housing adapted for incorporation into a wellhead and a rotating quill portion for establishing a seal to a tubular such as tubing or drill pipe. The quill is rotatably and axially supported by an internal rotating assembly comprising bearings and a seal assembly for isolating the bearings from well fluids.
As shown in FIG. 1, the rotating flow diverter (10) of the present invention comprises a stationary housing (12) adapted at a lower end by a flange connection (14), to operatively connect with the flange of riser pipe or a blow out preventer (not shown). The flange connection (14) can be an API flange or can be custom sized to match riser pipe flange connections.
In one embodiment, as shown in FIG. 6, the flange (14) of the stationary housing (12) comprises a double flange steel spool with one end of the spool being a custom flange (15) to match the stationary housing (12). Machined integrally to the spool is a second flange (19) that meets the required API flange specification. The use of such a double spool, allows the stationary housing (12) of the apparatus (10) to be a standard component that can have multiple lower flange sizes while remaining an integral component with no welded connections. The double flange spool comprises a custom upper flange (15) which will match the working pressure, custom profile and integrity of the rotating flow control diverter's stationary housing (12). The lower flange (19) on this spool will match API flange specifications to the selected flange size. For example, the lower flange may be a 13⅝″ 5000 PSI API flange.
In one embodiment, the double flange spool is connected to the stationary housing by bolting through an internal flange profile within the main body into tapped bolt holes (9) in the upper custom flange (15). A gasket/o-ring seal (not shown) provides pressure bearing integrity between the double flange spool and the rotating flow control diverter.
As shown in FIG. 5, in operation for diverting and recovering fluids from the wellbore, the stationary housing (12) can be fit with one or more outlets (13) along a side portion of the housing (12) for the discharge of well fluids. The stationary housing (12) may be made from any suitable metallic material including, without limit, 41/30 alloy steel.
The stationary housing (12) has a bore (16) fit with an internal assembly including a rotating tubular shaft (18) and a sealed bearing assembly (20). The tubular shaft (18) has an elastomeric stripper element (22) supported at a downhole end of the tubular shaft (18).
The elastomeric stripper element (22) may be manufactured from any suitable material including rubber. As shown in FIG. 1, in one embodiment, the elastomeric stripper element (22) is essentially cone shaped being securably attached at the wider end to the inner tubular shaft (18) by means of complimentary inserts. The elastomeric stripper element (22) protrudes into the bore (16) of the stationary housing (12). The narrower end of the stripper element (22) has an inner diameter that is less than the tubulars, such as drill string, being passed through the inner tubular shaft (18) resulting in a stretch fit. Pressure exerted on the cone shaped elastomeric stripper element (22) by fluids and gases from the well bore below acts to further seal the stripper element (22) onto the tubular. The foregoing description of one embodiment of the stripper element is not intended to be limiting and one skilled in the art will recognize that any suitable stripper element commonly used in the industry may be employed with the present invention.
An annular space is formed between the stationary housing (12) and the hollow shaft (18), the lower portion of which is exposed to wellbore pressures. The sealed bearing assembly (20) is positioned in the annular space for axially and rotationally supporting the hollow shaft (18) in the stationary housing (12).
The sealed bearing assembly (20) has a robust outer bearing housing (24) and a cap (26) which encloses a lubricating fluid chamber (28) both of which may be made from any suitable metallic material including, without limit, 41/30 alloy steel. The upper cap (26) is attached to outer housing (16) using set screws (19) or such other suitable attachment means as would be selected by one skilled in the art. The sealed lubricating fluid chamber (28) contains lubricating fluid (not shown) for lubricating the bearing elements (31). The seals (30) isolate the wellbore fluids from the lubricating fluid chamber (28) and may comprise any suitable sealing element commonly used for such purpose. The outer bearing housing (24) has a tapered outside diameter and a lower end (23) which is supported by the stationary housing (12).
Bearing elements (31) disposed in the sealed fluid chamber (28) radially and axially support the inner tubular shaft (18). The bearing elements may comprise any suitable type used for like purposes by those skilled in the art, and may be arranged in any manner within the fluid chamber that provides appropriate axial and radial support to the inner tubular member (18). In one embodiment, the bearing elements comprise a plurality of spring compressed bearings.
As shown in FIG. 2, in one embodiment a fan ring (32) is used to create a differential pressure within the sealed fluid chamber (28) of the bearing assembly (20). This differential pressure causes the lubricating fluid to flow from one side of the fan ring (32) to the other side. In one embodiment, the fan ring (32) is oriented such fluid flows from below the fan ring (32) to above the fan ring (32). This internal circulation increases the cooling rate of the lubricating fluid within the bearing assembly (20) as it causes lubricating fluid to flow across the bearings (31) and upwards in the sealed fluid chamber (28).
The fan ring (32) is attached to the hollow shaft (18) within the bearing assembly and thus will rotate along with the hollow shaft. This differential pressure will cause the oil to transfer from the lower side to the upper side of the fan or vein ring creating an internal circulation path. In one embodiment, an external oil cooler is provided which draws oil from the high pressure side of the fan ring and returns it to the low pressure side. The circulation may be simply driven by pressure differential caused by rotation of the fan ring and will not need any additional pumping energy. The external cooler may be a simple oil-to-air cooler, with or without forced air.
Although the embodiment of the invention claimed and described comprises a fan ring (32) comprising a substantially flat member having a plurality of blades (34), one skilled in the art will recognize that any suitable component, such as a vein ring, or a bladed impeller that will cause differential pressure when rotated through the fluid within the fluid chamber (28) may be substituted for use with the present invention.
In one embodiment, as depicted in FIGS. 1, 3 and 6, a solid locking ring clamp (40) is used, the solid locking ring clamp (40) with locking tabs (42) that when rotated will engage stationary locking tabs (44) mounted to the rotating flow control diverter's (10) stationary housing (12) creating a locking force to secure the bearing assembly (20) to the stationary housing (12).
The locking clamp ring (40) may be machined from steel to have suitable strength. In one embodiment, the locking ring clamp (40) has an upper internal shoulder profile (43) designed to match an external shoulder profile (45) on the outer bearing housing (24). The external shoulder profile may include openings for the lock tabs (42) to pass through.
The locking clamp ring (40) is placed on the bearing assembly (14) and is then lowered onto the stationary housing (12) of the rotating flow control diverter (10). It engages stationary locking tabs (44) on the stationary housing (12) when the locking clamp ring (40) is rotated. This rotation will cause the two sets of locking tabs (42, 44) to engage and lock against each other as they each have an opposite taper profile. When the taper profiles bottom out, the clamping force of the ring will meet the requirements to properly secure the bearing assembly (12) including the outer bearing housing (16) onto the stationary housing (12). Having reference to FIG. 1, it can be seen that the outer housing (16) of the present rotating flow control diverter (10) is entirely supported by the stationary housing (12) and the locking ring (44) acts to prevent separation of the two components but is not load bearing itself.
The locking clamp ring (40) may be manually rotated by means of a hammer, wrench or remotely by means of a hydraulic cylinder (not shown) acting on the locking clamp ring (40). When the locking clamp ring (40) has been fully rotated into the closed position, a lock mechanism such as a tapered pin may be used to secure the locking tabs (42, 44) together. The pin may have external threads and be screwed into a machined hole on the top of the locking tabs (42) which will align into a hole on one of the locking tabs (44) on the stationary housing (12). This pin will act as a safety locking device to ensure the locking clamp ring (40) is in the fully closed position and cannot be reopened until the pin is removed. One skilled in the art will appreciate that other suitable clamping means may be substituted to hold the stationary housing (12) and the bearing assembly (20) components together without deviating from the spirit of the invention claimed herein
The rotating flow control diverter (10) of the present invention can be positioned in the riser string below the drilling platform. This is facilitated by a riser pipe adapter (50) that allows the rotating flow control diverter (10) to attach at its upper end to the flanged connection of a riser pipe. As shown in FIG. 6, the riser pipe adapter (50) is sleeved housing comprised of three main components, an upper enclosure (52) and lower enclosure (54) and a clamp (60) that secures them together. The adapter (50) may be made from any suitable material including, without limit, steel.
The upper enclosure (52) of the adapter (50) comprises a weld neck profile or an API or custom flange (58) to allow the riser pipe to be connected to the upper enclosure (52) while maintaining a pressure barrier. The lower enclosure (54) of the adapter may be bolted or welded or machined integrally into the stationary housing (12) of the rotating flow control diverter (10) with a seal assembly or may be custom forged or machined as part of the stationary housing (12). When the riser pipe adapter (50) is mounted to the stationary housing (12) and attached to the flanged connection of a riser pipe, it provides a pressure barrier from the external environment. The riser pipe adapter (50) provides an internal pressure bearing cavity enclosing the rotating flow control diverter's (10) bearing assembly (20) and main body clamp (40).
A clamp ring (60) holds the upper and lower enclosure components together, and may be activated by hydraulic cylinders (62) to provide a clamping force locking the upper and lower enclosures together providing a pressured seal load bearing structure. As a result, the adapter (50) provides sealed structure to further connect the riser pipe to the rotating flow control diverter. The clamp ring (60) may be a solid ring or split clamp. One skilled in the art will appreciate that other suitable clamping means may be substituted to hold the upper and lower enclosure components together without deviating from the spirit of the invention claimed herein.
The lower enclosure (54) may be ported to allow externally mounted hydraulic cylinder shafts (70) to pass through the lower enclosure (54) and activate the clamp ring (40) on the rotating flow control diverter (10).
It can be understood from the Figures that the flanged connection (58) of the riser adapter (50) and the flanged connection (14) of the stationary housing (12) can each be attached to the flange of a riser pipe allowing the rotating flow control diverter (10) to be sandwiched between riser pipe sections. In this manner, the rotating flow control diverter (10) may be positioned in the riser string below the drilling floor and actually forms an integral part of the riser string. In one embodiment, it is anticipated that the flanged connection (14) of the stationary housing (12) could be attached to the BOP stack positioned on the sea bed, with the flanged connection (58) of the riser adapter (50) being attached to the lower end of the riser string.
As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein.

Claims

What is claimed is:

1. A rotating flow control diverter for use in a riser string comprising;

a) a tubular stationary housing having a lower flanged connection;

b) a removable bearing assembly, the bearing assembly comprising an outer housing, bearing elements, and an axially rotatable inner tubular shaft;

c) an elastomeric stripper element attached to the inner tubular shaft; and

d) a locking clamp mounted on the outer housing for releasably securing the outer housing of the bearing assembly to the stationary housing; and

e) a riser pipe adapter comprising;

i. a sleeved housing comprising an upper enclosure having a flanged connection for attachment to a flange of a riser pipe section and a lower enclosure, the lower enclosure being mounted on the stationary housing; and

ii. a locking clamp for releasably attaching the upper enclosure to the lower enclosure.

2. The rotating flow control diverter of claim 1 wherein the locking clamp for releasably securing the outer housing of the bearing assembly to the stationary housing comprises a locking clamp ring rotatably mounted on the outer housing.

3. The rotating flow control diverter of claim 2 wherein the locking clamp ring for releasably securing the outer housing of the bearing assembly to the stationary housing further comprises locking tabs that align with complementary locking tabs on the stationary housing.

4. The rotating flow control diverter of claim 1 wherein the locking clamp for releasably attaching the upper enclosure to the lower enclosure comprises a locking clamp ring mounted on the lower enclosure.

5. The rotating flow control diverter of claim 4 further comprising a hydraulic cylinder to actuate the locking clamp ring for releasably attaching the upper enclosure to the lower enclosure into a locked position.

6. The rotating flow control diverter of claim 1 further comprising an interchangeable flange on the stationary housing.

7. The rotating flow control diverter of claim 6 wherein the interchangeable flange comprises an upper flange defined by the stationary housing and a second flange that is releasably secured to the upper flange.

8. The rotating flow control diverter of claim 1 wherein the lower enclosure is defined by the stationary housing.

9. The rotating flow control diverter apparatus of claim 1 wherein the bearing assembly comprises;

(a) an outer housing and an axially rotatable inner tubular shaft, the outer housing and the axially rotatable inner tubular shaft defining an annular space between them;

(b) a sealed fluid chamber disposed in the annular space, the fluid chamber containing lubricating fluid;

(c) bearing elements disposed within the fluid chamber, the bearing elements radially and axially supporting the inner tubular shaft; and

(d) at least one fan ring mounted on and rotating with the inner tubular shaft in a position such that fan ring is disposed within the fluid chamber whereby rotation of the fan ring causes circulation of the lubricating fluid within the fluid chamber.

10. A method of inserting a rotating flow control diverter having an upper end and a lower end into a riser string, the rotating flow control diverter having a flanged connection at its lower end, the method comprising the steps of

(a) mounting a sleeved riser adapter on the upper end of the rotating flow control diverter, the adapter having a flanged connection;

(b) securing the flanged connection at the lower end of the rotating flow control diverter to the flanged connection of a riser pipe; and

(c) securing the flanged connection of the adapter at the upper end of the rotating flow control diverter to the flanged connection of a riser pipe.

11. The method of claim 8, wherein the flanged connection located at the lower end of the rotating flow control diverter is connected to the stack of a blow out preventer.

12. A riser pipe adapter for a rotating flow control diverter, comprising;

(a) a sleeved housing defining an interior pressure bearing cavity, the housing comprising;

iii. an upper enclosure having a flanged connection for sealed attachment to the flange of a riser pipe; and

iv. a lower enclosure, the lower enclosure being attached in a sealed manner to the rotating flow control diverter;

(b) a clamp for releasably attaching the upper enclosure to the lower enclosure in a sealed manner.

13. An offshore drilling assembly comprising a riser string and a rotating flow control diverter, said riser string comprising a plurality of interconnected lengths of flanged riser pipe and the rotating flow control diverter inserted in the riser string between a first flanged riser pipe and a second flanged riser pipe, the rotating flow control diverter comprising;

a. a tubular stationary housing having a lower flanged connection, the lower flanged connection being attached to the first flanged riser pipe;

b. a removable bearing assembly, the bearing assembly comprising an outer housing, bearing elements, and an axially rotatable inner tubular shaft;

c. an elastomeric stripper element attached to the inner tubular shaft;

d. a locking clamp ring rotatably mounted on the outer housing for releasably securing the outer housing of the bearing assembly to the stationary housing; and

e. a riser pipe adapter comprising;

i. a sleeved housing comprising an upper enclosure having a flanged connection, said flanged connection being attached to the second flanged riser pipe, and a lower enclosure, the lower enclosure being mounted on the stationary housing; and

ii. a locking clamp ring for releasably attaching the upper enclosure to the lower enclosure.