Patent Publication Number: US-2013233556-A1

Title: Rotating flow control diverter

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 gases and solids during drilling and other operations. 
     BACKGROUND 
     In the oil and gas industry it is conventional to mount a rotating blowout preventer or rotating flow control diverter at the top of a blowout preventer (BOP) stack beneath the drilling floor of a drilling rig while drilling for oil, gas or coal bed methane. The rotating flow control diverter serves multiple purposes including sealing pipe that is being moved in and out of the wellbore while allowing rotation of same. The rotating flow control diverter may also be used to contain or divert fluids such as drilling mud, produced fluids, and surface injected air or gas into a recovery line. 
     Typically a rotating flow control diverter consists of rubber strippers or sealing elements and an associated hollow quill that rotate with the drill string within a robust housing. Rotation of the strippers and the hollow quill is facilitated by a bearing assembly typically having an inner race rotates that with the drill string and an outer race that remains stationary with the housing. The bearing assembly is usually carefully isolated from fluids and gases in the wellbore by seals. 
     Downtime in drilling operations must be minimized to maximize efficiency and productivity. Further, it is imperative that production equipment must be robust and reliable to safeguard workers operating in the vicinity of such equipment. It is therefore desirable that a rotating flow controller diverter be designed to function in a trouble free manner, and that it is as durable as other associated drilling components. 
     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. 
     A common source of premature bearings failure in rotating flow head technology is the failure of a seal or seal stack that isolates the wellbore environment from entering the bearing assembly housing. In US Patent Application 2009/0161997, a sealed bearing assembly is described which attempts to maximize seal and bearing life. The lubricating fluid inside the bearing assembly is energized to a pressure intermediate the wellbore fluid pressure, and ambient atmospheric pressure. 
     Another major cause of bearing compromise in rotating flow control devices is heat. The bearing assembly generates considerable heat due to thrust loads on the internal components, particularly when drilling under high well bore pressure. With the generation of such heat, cooling of the lubricating fluid becomes critical to prevent degradation of the lubricant and to prevent premature failure of the bearing assembly. 
     One prior art solution is to fit the rotating flow control diverter with a remote support system to cool the fluid lubricant being utilized in the bearing assembly. Such remote support systems usually contain a coolant chiller/heat exchanger, lubricant reservoirs and pumps and they require a hydraulic system to move the fluid through the cooling loop. However, such prior art cooling systems are frequently complex and prone to undesired failure. Furthermore, the hydraulic system requires equipment and hoses that add to an already crowded work area, and which represent a safety risk to workers in the event of failure. 
     There is need in the art for an improved rotating control flow diverter having 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. It would also be advantageous if in a further embodiment there was means to cool the lubricating fluid being used to cool the bearings of the bearing assembly. There is also need for an improved method of circulating lubricating fluid within the bearing assembly of a rotating flow control device, and of cooling lubricating fluid being used in the bearing assembly of a rotating flow control diverter. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a rotating flow control diverter. In one embodiment, the apparatus comprises a rotating flow control diverter apparatus comprising;
         a. a stationary housing;   b. a sealed bearing assembly comprising;
           i. 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;   ii. a sealed fluid chamber disposed in the annular space, the fluid chamber containing lubricating fluid;   iii. bearing elements disposed within the fluid chamber, the bearing elements radially and axially supporting the inner tubular shaft;   iv. 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;   
           c. an elastomeric stripper element attached to the inner tubular shaft; and   d. means for releasably attaching the outer housing of the bearing assembly to the stationary housing;
           whereby rotation of the fan ring causes circulation of the lubricating fluid within the fluid chamber.   
               

     In one embodiment, the means for releasably attaching the outer housing of the bearing assembly to the stationary housing comprises a locking clamp ring rotatably mounted on the outer housing, the locking ring having locking tabs that align with complementary locking tabs on the stationary housing. In another embodiment, the sealed fluid chamber comprises an upper cap and a lower seal whereby the fluid chamber is defined by the upper cap, the lower seal, the inner tubular shaft and the outer housing of the bearing assembly. 
     In one embodiment, the fan ring comprises a substantially flat member comprising a plurality of blades, mounted on the inner tubular shaft in a substantially transverse orientation, which may be substantially parallel to the upper cap and the lower seal. In one embodiment, rotation of the fan ring blades pressurizes lubricating fluid above or below the fan ring. 
     In another embodiment the apparatus comprises;
         a. a lubricating fluid outlet in fluid chamber for fluid communication with the fluid chamber, the fluid outlet being positioned between the upper cap and the fan ring; and   b. a lubricating fluid inlet for fluid communication with the fluid chamber, the fluid inlet being positioned between the lower seal and the fan ring.       

     In one embodiment there is an external lubricating fluid cooler connected to the fluid inlet and the fluid outlet whereby rotation of the fan ring causes the lubricating fluid to circulate in a loop from a position below the fan ring, to a position above the fan ring, through the fluid outlet, through the external cooler and into the fluid inlet and back to a position below the fan ring. In one embodiment the rotation of the fan ring is sufficient to circulate the lubricating fluid without the need for additional pumping energy. 
     In one embodiment, the external lubricating fluid cooler comprises an air to oil cooler and the apparatus further comprises an series of fan blades mounted on the inner tubular shaft externally of the fluid chamber and adjacent to the air to oil cooler. 
     In one embodiment there is an interchangeable flange on the stationary housing. In one 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 aspect of the present invention, the invention comprises a method of circulating and cooling the lubricating fluid of a bearing assembly of a rotating flow control diverter, the rotation flow control diverter comprising;
         a. a stationary housing;   b. a sealed bearing assembly comprising;
           i. 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;   ii. a sealed fluid chamber disposed in the annular space, the fluid chamber containing lubricating fluid;   iii. bearing elements disposed within the fluid chamber, the bearing elements radially and axially supporting the inner tubular shaft;   
           c. an elastomeric stripper element attached to the inner tubular shaft; and   d. means for releasably attaching the outer housing of the bearing assembly to the stationary housing;       

     the method comprising the steps of:
         a. mounting a fan ring on the inner tubular shaft in a position such that fan ring is disposed within the fluid chamber; and   b. rotating the inner tubular shaft thereby causing rotation of the mounted fan ring and circulation of lubricating fluid.       

     In one embodiment, the method comprises the further steps of
         a. providing a lubricating fluid outlet in the fluid chamber for fluid communication with the fluid chamber;   b. providing a lubricating fluid inlet for fluid communication with the fluid; and   c. situating an external cooler between the fluid inlet and the fluid outlet, whereby the lubricating fluid is circulated through the external cooler by rotation of the fan ring.       

     In another aspect of the present invention, it comprises a rotating flow control diverter apparatus comprising;
         a. a stationary housing;   b. a sealed bearing assembly comprising;
           i. 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;   ii. an upper cap and a lower seal;   iii. a sealed fluid chamber disposed in the annular space, the fluid chamber being defined by the upper cap, the lower seal, the outer housing and the inner tubular shaft, the fluid chamber containing lubricating fluid;   iv. bearing elements disposed within the fluid chamber, the bearing elements radially and axially supporting the inner tubular shaft;   v. at least one fan ring mounted on the inner tubular shaft in a position such that fan ring is disposed within the fluid chamber in a position between the upper cap and the lower seal in an orientation substantially transverse to the axis of rotation;   
           c. an elastomeric stripper element attached to the inner tubular shaft; and   d. means for releasably attaching the outer housing of the bearing assembly to the stationary housing;
 
wherein rotation of the fan ring creates a pressure differential within the fluid chamber.
       

     In another aspect of the present invention, it comprises a method of circulating and cooling the lubricating fluid in the bearing assembly of a rotating flow control diverter having a stationary housing, the bearing assembly being mounted on the stationary housing and comprising an outer housing and an axially rotatable inner tubular shaft and an elastomeric stripper element attached to the inner tubular shaft, the method comprising the steps of forming a sealed fluid chamber between the outer housing of the bearing and the inner tubular member, mounting a fan ring on the inner tubular member such that it is disposed in the sealed fluid chamber and rotating the fan ring. 
     In another aspect of the present invention, it comprises a method of circulating lubricating fluid in the sealed bearing assembly of a rotating flow control diverter having bearings disposed in a sealed fluid chamber and a rotating inner tubular shaft, the method comprising mounting a fan ring on the inner tubular shaft in a position such that it is disposed in the sealed fluid chamber; and rotating the fan ring; whereby rotation of the fan ring creates a pressure differential in the fluid chamber. 
    
    
     
       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 partial cutaway view showing a lock ring in place over the outer bearing housing and showing an external cooler mounted on the outer-housing and upper cap of a bearing assembly. 
         FIG. 5  is a transparent view of a lock ring showing the locking tabs. 
         FIG. 6  is a cross-sectional view of the outer housing of the bearing assembly. 
         FIG. 7  is a partial cross sectional view of the outer housing of the bearing assembly showing the fluid inlet. 
         FIG. 8  is a view of one embodiment of a rotating flow control diverter in longitudinal cross-section showing an interchangeable flange. 
         FIG. 9  is a view of one embodiment the stationary housing adapted to receive an interchangeable flange. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention relates to a novel rotating flow control diverter. 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. 
     A rotating flow control diverter generally comprises a stationary housing adapted for incorporation into a wellhead and a rotating quill portion adapted to establish a seal to a tubular such as tubing or drill pipe that is passed through the quill. 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 present apparatus is directed to a rotating flow control diverter ( 10 ) comprising a stationary housing ( 12 ) adapted at a lower end by a flange connection ( 15 ), to operatively connect with a wellhead or blow out preventer (not shown). As shown in  FIGS. 8 and 9 , In operation for diverting and recovering fluids and gases 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 selective discharge of well fluids and gases. 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 ( 17 ) for receiving fluid and gas from the wellbore. The rotating flow control diverter ( 10 ) has a sealed bearing assembly ( 14 ) having an axially rotatable inner tubular shaft ( 18 ) disposed therein. The inner tubular shaft ( 18 ) has an elastomeric stripper element ( 22 ) supported at a downhole end of the inner 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 ( 17 ) 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. 
     As already discussed and as depicted in  FIGS. 8 and 9 , openings ( 13 ) may be placed in the walls of the stationary housing ( 12 ) to allow the diversion of gases and fluids from the bore ( 17 ). 
     The bearing assembly ( 14 ) has a robust outer housing ( 16 ) which may be made from any suitable metallic material including, without limit, 41/30 alloy steel. The outer housing ( 16 ) and the inner tubular shaft ( 18 ) of the bearing assembly ( 14 ) form an annular space disposed in which is a sealed fluid chamber ( 28 ). The sealed fluid chamber ( 28 ) is enclosed by the outer housing ( 16 ), the inner tubular member ( 18 ) and an upper cap ( 26 ) and a lower seal ( 27 ) 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 fluid chamber ( 28 ) contains lubricating fluid (not shown) for lubricating the bearing elements (not shown). In addition to preventing the egress of lubricating fluid, the lower seal ( 27 ) acts to isolate the wellbore fluids and gases from the bearing assembly ( 14 ). The lower seal ( 27 ) may comprise any suitable sealing element commonly used for such purpose. The outer housing ( 16 ) has a tapered outside diameter and a lower end which is supported by the stationary housing ( 12 ). 
     Bearing elements (not shown) 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 embodiment, the bearing elements comprise a plurality of spring compressed bearings. 
     As shown in  FIG. 2 , a fan ring ( 32  is used to create a differential pressure within the sealed fluid chamber ( 28 ) of the bearing assembly ( 14 ). 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 ( 14 ) as it causes lubricating fluid to flow across the bearings [not shown] and upwards in the sealed fluid chamber ( 28 ). 
     The fan ring ( 32 ) is mounted on the inner tubular shaft ( 18 ) within the bearing assembly and thus will rotate along with the inner tubular shaft ( 18 ). The fan ring ( 32 ) is mounted in a position such that it is substantially transverse to the axis of rotation of the tubular member ( 18 ) such that it is disposed within the sealed fluid chamber ( 28 ) between the upper cap ( 26 ) and the lower seal ( 27 ) in an orientation such that it is substantially parallel to the lower seal ( 27 ) and the upper cap ( 26 ). In a preferred embodiment, the fan ring is positioned closer to the upper cap ( 26 ) than the lower seal ( 27 ). The differential pressure in the lubricating fluid caused by the rotating fan ring ( 32 ) will cause the lubricating fluid to circulate within the fluid chamber ( 28 ) and in one embodiment, the lubricating fluid circulates by moving from below the fan ring ( 32 ), to a position above the fan ring ( 32 ). 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, the sealed fluid chamber ( 28 ) further comprises a fluid inlet ( 31 ) and a fluid outlet ( 33 ) for fluid communication with the sealed fluid chamber ( 28 ) from the exterior of the outer housing ( 16 ). The inlet and outlet may be, but does not have to be, the standard hydraulic inlet and outlets presently used on rotating flow control diverters. As shown in  FIGS. 6 and 7 , the fluid inlet ( 31 ) is positioned below the fan ring ( 32 ) proximate to the lower seal ( 27 ) and the fluid outlet ( 33 ) is positioned above the fan ring ( 32 ) proximate to the upper cap ( 26 ). As shown in  FIG. 7 , in one embodiment, the fluid inlet ( 31 ) opening is towards the upper end of the outer housing ( 16 ); however, a passage through the outer housing extends downwards and enters the fluid chamber ( 28 ) proximate to the lower seal element ( 27 ). In one embodiment, an external fluid lubricant cooler ( 35 ) is positioned between the fluid outlet ( 31 ) and the fluid inlet ( 33 ). The external cooler ( 35 ) draws heated lubricant through the fluid outlet ( 33 ) from the high pressure side of the fan ring ( 32 ) and returns cooled lubricant to the low pressure side of the fan ring ( 32 ) through the fluid inlet ( 31 ). The circulation may be simply driven by pressure differential caused by rotation of the fan ring ( 32 ) and will not need any additional pumping energy. The external cooler ( 35 ) may be a simple oil-to-air cooler, with or without forced air. As shown in  FIG. 4 , in one embodiment the cooler simply comprises a length of metal tubing mounted on the upper cap ( 26 ) connected at one end to the fluid inlet ( 31 ) and at the other end to the fluid outlet ( 33 ). The tubing of the external cooler ( 35 ) may be any suitable material that facilitates conductive and radiant heat transfer including, without limit, stainless steel. 
     It has been shown in testing that with the right type of lubricant, the fluid inlet and outlet may be directly interconnected without an external cooler with the lubricating fluid simply circulating through this loop as the fan ring is rotated. This is particularly so for production wells experiencing relatively low well bore pressures. 
     In one embodiment, an additional set of fan blades (not shown) may be mounted on the inner tubular shaft ( 18 ) externally of the bearing assembly, adjacent the cooler. This external fan when rotated by the inner tubular shaft ( 18 ) will create air movement to aid in the cooling of the lubricant as the air passes around the external cooler ( 35 ). 
     In one embodiment, as depicted in  FIGS. 1 ,  3  and  5 , 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&#39;s ( 10 ) stationary housing ( 12 ) creating a locking force to secure the bearing assembly ( 14 ) 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 ( 16 ). 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 ). Looking at  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. 
     In one embodiment, as shown in  FIG. 8 , the flange ( 15 ) of the stationary housing ( 12 ) comprises a double flange steel spool with one end of the spool being a custom flange to match the stationary housing ( 12 ) and machined integrally to it 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&#39;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 screwing bolts ( 7 ) through an internal flange profile within the main body through into tapped bolt holes ( 9 ) in the upper custom flange. A gasket/o-ring seal (not shown) provides the pressure bearer integrity between the double flange spool and the rotating flow control diverter.