STUFFING BOX ASSEMBLY

Abstract

A stuffing box assembly (4) comprising a primary housing (8) having a longitudinally oriented hollow bore (11) extending therethrough, a hanger assembly (9) within the longitudinally oriented hollow bore of the primary housing, and drive means (10) received within the hollow bore of the hanger assembly. The hanger assembly has a longitudinally oriented hollow bore extending therethrough. The drive means has means (15) to releasably secure the drive means to a pump rod such that the pump rod is hung from and supported within the primary housing by the hanger assembly. Rotation of the drive means causes a corresponding rotation of the pump rod. The hanger assembly includes one or more seals (17) to contain well fluids and to help prevent the flow of well fluids into the bore of the hanger assembly.

Description

FIELD OF THE INVENTION

This invention relates generally to oil well production equipment, and more particularly to a new and useful stuffing box assembly for use on an oil or other well driven into an underground formation.

BACKGROUND OF THE INVENTION

When pumping oil (or for that matter water or other fluids) from underground formations, typically a downhole pump is utilized wherein the pump is physically located deep within the well and used to pump the oil or fluid to the surface. In many such applications the downhole pump of choice is a screw or progressive cavity pump. Screw or progressive cavity pumps generally operate through the revolution of a pump rotor within a stator. A rotating pump rod extends from the surface to the downhole pump and is used to drive or rotate the rotor. A power supply, which most commonly would be comprised of a gas, diesel, hydraulic or electric motor, provides the means to rotate the pump rod, and hence the pump rotor. A series of seals are used to engage the rotating pump rod at or near the point where it exits the top of the well to prevent downhole fluids from leaking into the environment. Traditionally these seals and their related structural components have been referred to as a stuffing box.

In older reciprocating-type wells, a single stationary stuffing box was typically provided. In such applications packing material would normally be inserted into the stuffing box and compressed against a dedicated portion of the pump rod (that may be polished to present a smooth sealing surface) in order to minimize the leakage of well fluids. With the introduction of rotary or progressive cavity pumps, others have suggested the use of a rotating stuffing box as a means to help guard against a premature failure of packing material that can sometimes occur when using a more traditional stuffing box in a rotary pump application (for example see Canadian patent 2,095,937 issued Dec. 22, 1998). Such rotary stuffing boxes commonly employ a rotating or hollow shaft structure that is received about the pump rod such that the hollow shaft rotates in unison with the pump rod. The exterior portion of the hollow shaft can be hardened and machined to provide a smooth surface against which one or more seals act in order to help prevent leakage of fluid from the well. While these hollow shaft structures can be effective, they also add to the complexity of the stuffing box, its costs and weight.

In addition to stuffing boxes, the wellhead equipment on most oil wells includes a blowout preventer that may be used to seal around the pump rod in order to contain well fluids and maintain well control, particularly when pumping ceases. Blowout preventers have been produced in a wide variety of different configurations and, using an equally wide variety of different mechanical structures. Most commonly, blowout preventers are comprised of a pair of radially opposed rams having sealing surfaces on their inner ends such that when the rams are driven inwardly toward the pump rod they sealingly engage the exterior of the rod surface, thereby preventing the escape of fluids from the well. In some instances the blowout preventer, rams may include gripping inserts or gripping surfaces that serve the further function of engaging the surface of the pump rod to a degree that allows the rams to securely hold and retain the pump rod in place.

The surface equipment on an oil well will often include a number of additional components, such as casing heads, tubing string hangers, tubing string rotators, flow-tees, backspin inhibiting devices, drive heads etc. In many applications it is also necessary to employ some form of pump rod hanging device that serves the function of accepting the vertical load of the pump rod (which in deep wells can be significant) and transmitting that load to the well casing. Often the pump rod hanging device takes the form of a rod clamp that is secured or compressed about the exterior surface of the pump rod, typically at the top or upper end of the rod. Pump rod clamps are commonly designed to fit or mate within correspondingly shaped recesses in a drive gear or equivalent structures, such that rotation of the drive gear causes rotational movement of the rod clamp and thus the pump rod.

As a result of the need for a substantial number of mechanical components at the surface of an oil well, the height of the wellhead equipment can often become significant. As the height of the surface equipment (sometimes referred to as a Christmas tree) increases, so does its weight and the general necessity for larger and stronger flanges, bolts, threads and other such means that are used to hold adjacent components together. The height and weight of the wellhead components is even more significant where the well is not vertical, in which case the assembled equipment must be capable of accommodating the resulting bending moment. There is thus a desirability to minimize the height of surface production equipment that extends out of the ground above the well casing. There is also the need for the use of highly effective stuffing boxes and sealing mechanisms, and the need to simplify the mechanical systems that are utilized to hang and to rotate a pump rod within a well, and to seal against the rod when the pumping operation ceases.

SUMMARY OF THE INVENTION

The invention therefore, in one of its aspects, provides a stuffing box assembly that helps to address some of the deficiencies in currently available wellhead equipment. The stuffing box is contained within a housing that provides an effective means to seal against the pump or drive rod, and that contains a pump rod hanger with related bearing components and a mechanism that presents a simplified mechanical structure for driving the pump rod. In one embodiment the stuffing box may also contain an integrated blow out preventer. The invention also concerns a new and novel casing head.

Accordingly, in one of its aspects the invention provides a stuffing box assembly comprising a primary housing having a longitudinally oriented hollow bore extending therethrough; a hanger assembly within said longitudinally oriented hollow bore of said primary housing, said hanger assembly having a longitudinally oriented hollow bore extending therethrough; and, drive means received within said hollow bore of said hanger assembly, said drive means having means to releasably secure said drive means to a pump rod such that the pump rod is hung from and supported within said primary housing by said hanger assembly and such that rotation of said drive means causes a corresponding rotation of the pump rod, said hanger assembly including one or more seals to contain well fluids and to help prevent the flow of well fluids into said bore of said hanger assembly.

In a further aspect the invention provides a casing head for securing to the upper end of the casing of a well extending into an underground formation, the casing head including one or more side entry passageways to permit the introduction of coiled tubing or other tubular or elongate member into the wellbore of the casing without the removal of wellhead equipment positioned above said casing head.

In yet a further aspect the invention concerns a stuffing box assembly comprising a primary housing; a removable hanger assembly releasably and sealingly receivable within a longitudinally oriented hollow bore extending through said primary housing, said hanger assembly having a longitudinally oriented hollow bore extending therethrough; and, drive means sealingly receivable within said hanger assembly and extending through said hollow bore within said primary housing when said hanger assembly is received therein, said drive means including torque input means permitting for the transference of rotational torque from a power source to said drive means, said drive means having means to releasably secure said drive means to a pump rod such that rotation of said drive means causes a corresponding rotation of the pump rod when secured thereto, said drive means including one or more seals between said drive means and the pump rod, when said hanger assembly is received within said primary housing said hanger assembly hanging said drive means, and a pump rod when attached thereto, from said primary housing, said hanger assembly including bearings to facilitate the rotation of said drive means, said hanger assembly including one or more seals to seal against the exterior surface of said drive means to help prevent the flow of fluid between said drive means and said hanger assembly.

In still a further aspect the invention provides a stuffing box assembly comprising a primary housing; a hanger assembly within a longitudinally oriented bore extending through said primary housing, said hanger assembly having a longitudinally oriented bore extending therethrough; and, drive means sealingly received within said hollow bore of said hanger assembly, said drive means including torque input means permitting for the transference of rotational torque from a power source to said drive means, said drive means having means to releasably secure said drive means to a pump rod such that rotation of said drive means causes a corresponding rotation of the pump rod when secured thereto, said hanger assembly hanging said drive means, and a pump rod when attached thereto, from said primary housing, said hanger assembly including bearings to facilitate the rotation of said drive means, said hanger assembly including one or more seals to contain well fluids and to help prevent the flow of well fluid into said bore in said hanger assembly.

Further aspects and advantages of the invention will become apparent from the following description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings which show the preferred embodiments of the present invention in which:

FIG. 1 is a vertical cross-sectional view through a typical oil well that employs a progressive cavity pump and having attached to the wellhead a stuffing box assembly generally constructed in accordance with one of the preferred embodiments of the present invention;

FIG. 2 is a side elevational view of the stuffing box assembly shown in FIG. 1, having an electric drive motor attached thereto;

FIG. 3 is a side elevational view of the stuffing box assembly shown in FIG. 2, rotated 90°;

FIG. 4 is a cross-sectional view taken along the line of 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 3;

FIG. 6 is an exploded view of the stuffing box assembly (with a portion of its outer housing removed) shown in FIG. 2;

FIG. 7 is an enlarged detailed cross-sectional view taken along the line 7-7 of FIG. 6;

FIG. 8 is a vertical cross-sectional view of an alternate embodiment of the stuffing box assembly of the current invention having mounted thereon an electric motor;

FIG. 9 is an exploded view of the stuffing box assembly shown in FIG. 8;

FIG. 10 is an enlarged detailed cross-sectional view taken along the line 10-10 of FIG. 9;

FIG. 11 is a vertical cross-sectional view of one embodiment of the stuffing box assembly in accordance with the present invention shown in association with an electric motor and a casing head, and further including a separate scrap view of the tubing (with a tubing rotator attached thereto) and the stuffing box assembly (with a rod assembly) shown removed from the vertical cross-sectional view;

FIG. 12 is an enlarged view of the stuffing box assembly and casing head shown in FIG. 11 having the electric motor removed;

FIG. 13 is an upper side perspective view of the casing head shown in FIG. 12;

FIG. 14 is a side elevational view of the casing head shown in FIG. 13;

FIG. 15 is a sectional view taken along the line 15-15 in FIG. 14;

FIGS. 16 and 16A are vertical cross-sectional views of an alternate embodiment of the stuffing box assembly of the current invention having mounted thereon an electric motor;

FIGS. 17 and 17A are vertical cross-sectional views of a further alternate embodiment to that shown in FIG. 16;

FIG. 18 is a vertical cross-sectional view of a further embodiment to that shown in FIG. 17;

FIG. 19A is a further alternate embodiment to that shown in FIG. 18; and

FIG. 19B is a cross-sectional view taken along the line of 19B-19B in FIG. 19.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention may be embodied in a number of different forms. However, the specification and drawings that follow describe and disclose only some of the specific forms of the invention and are not intended to limit the scope of the invention as defined in the claims that follow herein.

With reference to FIG. 1 there is shown in vertical cross section a typical oil well 1 that employs a progressive cavity pump 2 to lift oil to the surface. At the surface of the oil well the wellhead 3 has attached to it a stuffing box assembly 4 constructed in accordance with one of the preferred embodiments of the present invention. In the embodiment of the well shown in FIG. 1, an electric or hydraulic motor 5 provides the means by which a pump rod 6 is rotated in order to turn the rotor 7 of the progressive cavity pump. In this embodiment motor 5 is in a direct drive configuration with rotor 7.

Turning next to FIGS. 2 through 7, there is shown from various angles and with various degrees of cross sectioning the internal and external features and components of stuffing box assembly 4. As will be appreciated from an examination of those Figures, stuffing box 4 is comprised generally of a primary housing 8, a hanger assembly 9 (that in this embodiment is shown as being removable but that also may be permanently fixed to housing 8), and a drive means 10 (that in this embodiment is a drive rod but that, as discussed below, may also be a rotating mandrel). Primary housing 8 has a longitudinally oriented hollow bore 11 extending generally through its middle portion into which hanger assembly 9 is releasably receivable. As shown, hanger assembly 9 also has a longitudinally oriented bore 12 extending therethrough that is capable of sealingly receiving drive rod 10. Drive rod 10 is an elongate member that, when received within hanger assembly 9 with the hanger assembly situated within hollow bore 11 of primary housing 8, will preferably extend through the bottom of the primary housing. Drive rod 10 further has an upper end 13 and a lower end 14, with lower end 14 having means 15 thereon to releasably secure the drive rod to a pump rod such that rotation of the drive rod will cause a corresponding rotation of the pump rod. It will be appreciated that means 15 could be any one of a variety of different mechanisms that could be used to secure the drive rod to the pump rod, however, in most instances it is expected that means 15 will be a threaded connection that allows the two rods to be threaded together.

Hanger assembly 9 is designed and configured to hang drive rod 10, and a pump rod that may be attached thereto, from primary housing 8 when the hanger assembly is received within the primary housing. In order to facilitate the rotation of the drive rod and pump rod, the hanger assembly preferably includes bearings 16 as well as one or more seals 17 that seal against the exterior surface of the drive rod to prevent the flow of fluid between the drive rod and the hanger assembly. To help facilitate the seal between drive rod 10 and seals 17, the surface of the drive rod adjacent the seals may be polished or may have a smooth ceramic or other coating applied. Polishing or coating the rod not only helps to enhance the seal between the rod and seals 17 but also potentially extends the useful life of the rod.

In the embodiment of the hanger assembly shown in FIG. 7, bearings 16 include an upper bearing 32, a middle bearing 33 and a lower bearing 34. It will be understood that other configurations of bearings could also be used and that the various bearings generally accommodate thrust and/or rotary loads. It will also be apparent that the hanger assembly in this embodiment is manufactured in two primary sections; namely, a bottom portion 35 and a lock down nut 36 that are threaded together once the various bearings and seals have been put in place. A cap 43 may be screwed or bolted to the lock down nut and/or the bottom portion. The upper portion of the hanger assembly may include a grease nipple or lubrication port 37 to permit the introduction of grease or lubricants into the hanger assembly to help lubricate the various bearings and seals. In addition to seals 17 positioned in the lower portion of the hanger assembly to seal against the drive rod and maintain well control (two of which are shown, however, more or fewer of which may be utilized), the hanger assembly may also include an upper seal 38 to seal between the upper or top portion of the hanger assembly and the top portion of the drive rod. When received within the primary housing, hanger assembly 9 will be static while permitting drive rod 10 to be rotated. Accordingly, seals 17 and 38 are preferably dynamic seals that seal against the rotating exterior surface of the drive rod when it is received within the hanger assembly. A series of static seals 39 are used to seal the hanger assembly with housing 8 and to seal lock down nut 36 within bottom portion 35.

While hanger assembly 9 may be hung within hollow bore 11 of primary housing 8 in a number of different manners, in the embodiment shown in the attached drawings longitudinally oriented hollow bore 11 through the primary housing includes a first diameter portion 18 at its upper end in order to receive the hanger assembly and a second or lower, reduced diameter, portion 19. In this embodiment the first and second diameter portions 18 and 19 are connected by a sloped shoulder portion 20 that acts as a bearing surface against which a sloped exterior portion 21 of hanger assembly 9 bears when the hanger assembly is received within hollow bore 11 of the primary housing. The engagement of the sloped exterior surface 21 of the hanger assembly with the sloped shoulder 20 of hollow bore 11 results in a friction fit between the hanger assembly and the primary housing that securely and statically holds the hanger assembly within the housing such that the weight of the drive rod, and the pump rod attached thereto, that is borne by the hanger assembly is transmitted, via the sloped shoulder contact, to the body of the primary housing. One or more of the static seals 39 (see FIG. 7) are preferably placed between the exterior surface of the hanger assembly and the interior of hollow bore 11 of the primary housing in order to help prevent the flow of fluid between the primary housing and the hanger assembly. The hanger assembly may also include one or more lock pins to prevent the hanger assembly (and hence the drive rod) from rotating and/or lifting with primary housing 8, particularly in the event of a power loss, pump shut down or in a high pressure well. In a further embodiment sloped shoulder portion 20 could be a square or other shaped shoulder. It will also be appreciated that there could exist teeth, splines or other structures between the hanger assembly and the primary housing to prevent the hanger assembly from rotating. Alternately, the hanger assembly could be prevented from rotating by frictional engagement with the primary housing.

In the embodiment of the invention shown, stuffing box assembly 4 further includes a pair of radially opposed blowout preventer rams 23 that are situated in transverse bores 24 that extend through the primary housing. Transverse bores 24 are in communication with the exterior of the housing and with hollow bore 11 such that when driven inwardly towards the center of the housing, the blowout preventer rams sealingly engage each other and the exterior surface of drive rod 10. It will be appreciated by those skilled in the art that the particular form of rams used could vary from application to application. In most instances it is expected that the interior surfaces of the rams will be fitted with a seal that generally has a shape that conforms to the exterior surface of the drive rod. When the rams are driven inwardly and compressed up against the surface of the drive rod the seals will pack off the open area of the hollow bore in order to prevent the escape of well fluids past the rams.

In some instances it may be desirable for the interior surfaces of the rams to have gripping faces or, alternatively, gripping inserts (not shown) that can physically contact the exterior surface of the drive rod in order to securely hold it in place. The gripping faces or gripping inserts would typically be capable of holding both the vertical load of the drive rod and the pump rod attached thereto, as well as rotational torque that may be built up within the drive rod and pump rod on account of either the operation of the compressive cavity pump or the tendency for the pump rod to exhibit back spin when the pumping operation ceases and the weight of oil or fluid in the well bears directly upon the pump rotor. It will equally be appreciated that the blowout preventer rams will, typically include various other features and elements that are commonly used in blowout preventers, including ram stems and a mechanism to actuate the rams, whether it be through manually turning the stems or through the use of hydraulic, electric or pneumatic actuators.

As shown most clearly in FIGS. 2, 3 and 4, in one embodiment, stuffing box assembly 4 includes one or more locking mechanisms 25 that assist in retaining hanger assembly 9 within hollow bore 11 of primary housing 8. In FIGS. 2, 3 and 4, the locking mechanisms are comprised of a plurality of lock down or hold down screws 26 that are threadably received within the primary housing 8 of the stuffing box. Lock down screws 26 have interior ends that engage the exterior surface of hanger assembly 9 in order to prevent the hanger assembly from being lifted within the primary housing, particularly in the case of high pressure wells. Employment of lock down screws 26 maintains the seating of sloped exterior surface 21 of the hanger assembly with shoulder 20 of hollow bore 11, and in so doing also maintains the seating of seals 39 with the interior surface of hollow bore 11 to prevent the leakage of well fluids between the hanger assembly and the primary housing.

Rotational torque may be applied to drive rod 10 through the use of a variety of different mechanical and electro-mechanical means. The example of one of the preferred embodiments of the invention that is shown in the attached drawings is a direct drive system where drive rod 10 is driven directly by electric or hydraulic motor 5. In this instance the upper end of the drive rod includes a torque input means 27 that permits the transference of rotational torque from a drive source (in this case motor 5) to the drive rod, which in turn transfers rotational torque to a pump rod attached thereto. While input means 27 could itself take different forms, in the embodiment shown the input means comprises a recess within the upper end of the drive rod which is of a configuration and size such that the recess accepts the end of the shaft of motor 5 when the motor is mounted on top of primary housing 8. To permit the transference of rotational torque from the motor shaft to the drive rod, the motor shaft may be splined with the recess and the drive rod having a similar configuration or, alternatively, the motor may be equipped with a keyed shaft with the recess machined with an appropriate key way. In any event, it will be appreciated that through mounting motor 5 directly upon the upper surface of primary housing 8 such that the shaft of the motor is received within a corresponding configured recess in the upper end of drive rod 10, operation of motor 5 will result in a direct rotation of the drive rod and the pump rod attached thereto. It will also be appreciated that such a direct drive structure presents a number of advantages, not the least of which includes a more compact and simplified wellhead design, a more efficient drive structure (that eliminates the need for belts, chains, gears, pulleys etc.), the ability to more accurately control the speed of rotation of the drive rod and pump rod (particularly where a DC motor is utilized), a simplified structure that permits for the easy removal and replacement of the motor, a reduced wellhead height, and a mechanism by which backspin of the pump rod can be controlled and/or dissipated easily, economically and in a safe manner.

With reference to FIGS. 8, 9 and 10, there is disclosed therein an embodiment of stuffing box assembly 4 that includes means to pressurize the interior of the stuffing box for purposes of helping to lubricate seals 17 and also, if desired, to help maintain the pressure within the stuffing box above wellbore pressure as a means to deter the influx of well fluids into the stuffing box. In this embodiment the shaft of motor 5 includes a longitudinal hollow bore 28 that extends therethrough. Similarly, a longitudinally oriented hollow bore 29 extends through at least the upper end of drive rod 10 such that when the shaft of the motor is received within input means 27 longitudinal bore 28 within the motor shaft is in fluid communication with longitudinal bore 29 of the drive rod. As shown most clearly in FIG. 10, drive rod 10 is also formed with at least one transverse oriented exit port 30 that extends from the exterior surface of the drive rod to bore 29 such that bore 29 is effectively in fluid communication with the drive rods' exterior surface. Such a structure of hollow bores extending through the motor shaft and into the upper end of the drive rod, in combination with one or more exit ports 30, permits bore 28 within the motor shaft to be at least partially filed with oil and to have connected to, or associated therewith, a pressurization means to pressurize the oil. The pressurized oil (or for that matter other lubricant) is forced through the motor shaft, into the bore in the upper end of the drive rod, through the transverse passage, and into the interior of hanger assembly 9. Transverse exit ports 30 deliver pressurized oil to the exterior surface of the drive rod adjacent to, or in the general vicinity of, dynamic seals 17, thereby helping to lubricate the seals, pressurizing the interior of the stuffing box, and helping to maintain well control by deterring the influx of well fluids into the interior portions of the stuffing box. As mentioned, if desired the pressurization means can be designed so as to pressurize the oil or fluid injected into the stuffing box to such a level that the pressure within the interior of hanger assembly 9 exceeds the pressure of the wellbore.

The source of pressurization used to pressurize the interior of the stuffing box could be an exterior source of pressurized fluid (such as a hydraulic pump or accumulator) that is piped or otherwise connected to one or the other of bores 28 and 29. In the embodiment shown in FIGS. 8, 9, 10 the upper end of bore 28 within the motor shaft is sealed and a pressurization piston 31 is received therein. Piston 31 may be either spring or gas actuated. Regardless, in either instance the piston exerts a compressive force upon the oil received within bore 28. If desired the sealing of the upper end of bore 28 within the motor shaft can be accomplished through the use of a removable cap or nut 42 that permits an increase in the compression of the spring 41 used to energize piston 31. Alternately, when the piston is gas actuated a valve (such as a snifter valve) can be mounted in the top of the shaft to permit the addition of further gas in order to more highly pressurize the piston and thereby enhance or increase the pressurization of the oil within bores 28 and 29. A removable cap at the top of bore 28 will also allow for the level of oil within the bore to be checked periodically.

In an alternate embodiment to that as shown in FIGS. 8 and 10, an external source of pressurized oil or lubricant may be connected to a lubrication port 37 to permit the introduction of lubricant into the hanger assembly in order to lubricate the various bearings and seals. In such an embodiment the drive rod and/or the hanger assembly may be fitted with specialized lubrication ports to direct lubricant to particular seals, bearings, or other areas where lubrication may be desired. Whether it be through the use of a lubrication system such as that shown in FIGS. 8, 9 and 10, or a separate stand-alone lubrication system connected to the hanger assembly, it is expected that during operation the lubricant will be pressurized to the point where it will slowly seep past dynamic seals 17 and leak into the well. This will help to ensure that the seals are adequately lubricated, will assist in flushing debris from the bearing and keeping the bearings free of contaminants, and will also help to prevent the ingress of well fluids into the stuffing box. In most instances it is expected that the leakage of lubricant into the well will be something in the range of a few cubic centimeters per day, making the loss of lubricant negligible under the circumstances.

In a further embodiment of the invention, stuffing box assembly 4 includes a tubing hanger 44 that effectively hangs a tubing string 45 from primary housing 8. The tubing hanger may be any one of a wide variety of commonly utilized tubing hangers that permit tubing to be securely held within the wellhead while preventing the loss of fluids between the hanger and the internal bore of housing 8. In the embodiment shown in FIG. 11, tubing string 45 has secured thereto a downhole tubing rotator 46, such as that shown and described in U.S. Pat. No. 7,306,031. It will be appreciated by those having a thorough understanding of the invention that through permitting the incorporation of tubing hanger 44 within stuffing box assembly box 4, the overall height of the wellhead can be reduced; once again having associated beneficial effects. Furthermore, the utilization of a downhole rotator eliminates the need for an external tubing rotator and further reduces the size and weight of the exterior wellhead components.

In the embodiment of the invention shown in FIGS. 1 and 11 through 15, stuffing box assembly 4 is mounted upon a unique and novel casing head 47. In this embodiment the casing head contains one or more side entry passageways 48. In the attached Figures two such side entry passageways are incorporated within the casing head. During normal pumping operations side entry passageways 48 would typically be closed off through the use of removable plugs 49. Alternately, valves could be used in place of the plugs. Plugs 49 keep debris out of passageways 48 and also maintain well control. However, if for any reason (for example formation stimulation purposes) it should become necessary to insert coiled tubing or other tubular or elongate members into the well, plug 49 can be removed from one of the side entry passageways permitting the coiled tubing or other device to be inserted into the well without the need to disassemble wellhead equipment and without the need to pull the tubing from the well. It will be appreciated that particularly where a downhole tubing rotator 46 is utilized, the advantage provided by casing head 47 is significant in that it allows for the insertion of coiled tubing below the position of the tubing rotator. Otherwise, any activities requiring the insertion of coiled tubing or similar devices into the well would necessitate the removal of wellhead equipment, the pulling of the tubing string (at least to the point where the rotator is clear of the well head) and then the insertion of the coiled tubing, all of which increase costs and downtime of the well.

As shown in the attached Figures, in a preferred embodiment passageways 48 are arranged with their longitudinal axes at a “shallow” angle relative to the centre line of the wellhead to permit the coiled tubing or other tubular or elongate member to be inserted at a shallow angle of approach relative to the casing and any tubing string that may be received therein. In these regards, the “shallow” angle is preferably less than 45°, more preferably less than 30° and most preferably less than 20°. That is, a shallow angle of approach between the passageways and the tubing string will allow the coiled tubing or other member to be inserted while minimizing the potential for damage to either the coiled tubing or the tubing string.

Casing head 47 may also be configured to accept the tubing string hanger 44 or, alternately, and as shown in the attached Figures, the tubing string hanger may be located in primary housing 8. Lock down or hold down screws for the tubing string hanger may be located in the upper flange of the casing head.

FIG. 16 shows an alternate embodiment of the invention to that shown generally in FIGS. 8 through 10. In this embodiment, the drive means is not a drive rod but is instead a rotating mandrel 51 through which the pump or polished rod 6 is received. In the embodiment depicted in FIG. 16, the energy to drive the pump rod is provided by an electric or hydraulic motor 5 that is situated in a direct-drive configuration. In this particular embodiment the motor shaft 50 is preferably hollow (or at least the lower portion of it is preferably hollow) to be received about the upper end of the pump rod 6 and into rotating mandrel 51. A drive connection exists between the motor shaft 50 and the rotating mandrel that permits the transference of rotational energy from the motor shaft to the mandrel. In most instances it is expected that that drive connection will be in a form of a series of splines 52 on the motor shaft and the rotating mandrel, wherein the splines mesh together in order to allow for the transference of rotational torque. In other cases keys, shaped shafts and other drive connection mechanisms could equally be used in place of splines 52.

With reference once again to FIG. 16, it will be understood that when the pump rod extends through the hollow interior 53 of rotating mandrel 51, it will be necessary to transfer rotational energy from the mandrel to the pump rod in order to cause the rod to rotate. In this embodiment of the invention, the preferred mechanism for doing so comprises slips 54 that are inserted between the exterior surface of the pump rod and the interior diameter of mandrel 51. As shown, the lower portion of the hollow interior 53 of rotating mandrel 51 preferably decreases in diameter forming a generally conical shape into which slips 54 are received. The weight of pump rod 6 bearing against slips 54 will thus have the tendency to enhance the grip between the slips, the pump rod and the interior surface of the mandrel, to the point where rotation of the mandrel by motor shaft 50 will cause the simultaneous rotation of pump rod 6. In this manner the motor shaft, rotating mandrel and pump rod will all rotate in unison, effectively as a single component. Static seals 55 (for example o-rings) are preferably inserted between the bottom portion of the rotating mandrel and the pump rod to prevent the influx of well fluids into hollow interior 53. Otherwise, rotating mandrel 51 generally functions in a similar fashion to drive rod 10 in that it transfers the load of the pump rod onto thrust bearings within the hanger assembly with radial bearing facilitating the rotational movement of the mandrel.

A slightly different variation to the embodiment shown in FIG. 16 is depicted in FIG. 17. The embodiment of FIG. 17 is overall generally similar to that shown in FIG. 16 with the primary exception being that pump rod 6 is secured to rotating mandrel 51 through the use of a rod clamp 56 rather than slips 54. In this embodiment, rod clamp 56 has an outside diameter that is smaller than the inside diameter of hollow motor shaft 50 to allow the clamp to at least be partially received within the motor shaft. Rod clamp 56 will be securely held about the exterior surface of pump rod 6 (preferably through frictional engagement such as what would occur as a result of a conical shaped interior of rotating mandrel 51 and elements on the rod clamp that are able to deflect inwardly towards a rod when wedged against the conical sloping shape of the mandrel). Mandrel 51 also preferably contains splines (or drive dogs) 57 that transfer rotational movement of the mandrel to the pump rod. As shown in FIG. 17, in this variation the pump rod may also extend upwardly through the centre of motor 5.

The embodiment of the invention shown in FIG. 18 is yet a further version of that shown in FIGS. 16 and 17. Here, the pump rod 6 is shown as extending through the motor 5 (as in FIG. 17), however, rod clamp 56 is a more traditional polished rod clamp and it has been moved to a position above the motor as is more common in current drive heads. The weight of the pump rod is thus transferred from the rod to clamp 56, to motor shaft 50, and then ultimately to rotating mandrel 51 which, as is in case of the previously described embodiments, engages both thrust and radial bearings within hanger assembly 9.

FIG. 19 shows yet a further possible embodiment of the invention to that shown in FIGS. 16 through 18. Here the hollow motor shaft has a splined connection with a torque coupling 57 which transmits rotational torque from the motor shaft to rod clamp 56. Clamp 56 physically bears against the upper surface of rotating mandrel 51 and also contains in its lower end a rotating sleeve 57 that rotates with rod clamp 56 and that is splined to mandrel 51. Accordingly, rotation of motor shaft 50 causes torque coupling 57, rod clamp 56, rotating sleeve 58, rotating mandrel 51 and pump rod 6 to rotate in unison with the motor shaft. In this embodiment motor 5 can be more easily removed from the wellhead.

From a thorough understanding of the invention described herein and shown in the attached drawings it will become clear that the stuffing box assembly of the present invention presents a highly efficient, compact, structure that is capable of sealingly hanging a drive rod, and a pump rod attached thereto, within a well using a minimum number of well head components to reduce the overall height and weight of the wellhead. The design and structure of the stuffing box assembly and its primary housing allows for the integration of a blowout preventer/rod clamp within the same compact unit, thereby eliminating the need for a separate BOP and rod clamp. A simplified manner of applying rotational torque to the drive and pump rods is also provided that allows for the direct mounting of an electric or hydraulic motor on top of the stuffing box, hence eliminating the need for more complex drive gear systems that add to the weight of the wellhead equipment, increase expense, and in many instances provide off-balanced non-symmetrical loading of wellhead equipment. Where a hydraulic or DC motor is used to rotate the drive rod, there is greater ability to control the rotational speed of the drive and pump rods in a safe and inexpensive manner that can also be used to control back spin. As has also been described, the stuffing box assembly of the present invention provides a manner to easily and effectively pressurize the internal portion of the stuffing box in order to lubricate and enhance the effectiveness and longevity of its bearings and seals. The novel and unique casing head design of the invention presents a simple, fast and efficient means for coiled tubing to be inserted into the well without the need to disassemble wellhead components and without the need for cranes or boom trucks to pull the tubing string.

It is to be understood that what has been described are the preferred embodiments of the invention and that it may be possible to make variations to these embodiments while staying within the broad scope of the invention. Some of these variations have been discussed while others will be readily apparent to those skilled in the art. For example, while the invention has been described as used in association with a direct drive electric or hydraulic motor, it will be appreciated that the motor could equally be off-set from the centerline of the stuffing box with the rotation of the drive or pump rod accomplished through the use of conventional pullies and gears.

Claims

1. A stuffing box assembly comprising: a primary housing having a longitudinally oriented hollow bore extending therethrough;a hanger assembly within said longitudinally oriented hollow bore of said primary housing, said hanger assembly having a longitudinally oriented hollow bore extending therethrough; and,drive means received within said hollow bore of said hanger assembly, said drive means having means to releasably secure said drive means to a pump rod such that the pump rod is hung from and supported within said primary housing by said hanger assembly and such that rotation of said drive means causes a corresponding rotation of the pump rod, said hanger assembly including one or more seals to contain well fluids and to help prevent the flow of well fluids into said bore of said hanger assembly.

2. The stuffing box assembly as claimed in claim 1 wherein said hanger assembly includes bearings to facilitate the rotation of said drive means, said hanger assembly further including one or more seals to prevent the flow of fluid between said hanger assembly and said primary housing.

3. The stuffing box assembly as claimed in claim 2 wherein said drive means is a drive rod.

4. The stuffing box assembly as claimed in claim 3 further including a pair of radially opposed blowout preventer rams situated in transverse bores extending through said primary housing, said transverse bores in communication with said longitudinal bore through said primary housing such that said blowout preventer rams sealingly engage the exterior surface of said drive rod when said rams are advanced within said transverse bores toward said drive rod.

5. The stuffing box assembly as claimed in claim 2 wherein said longitudinally oriented hollow bore through said primary housing includes a first diameter portion and a second reduced diameter portion, said first and said second diameter portions connected by a shoulder portion, said shoulder portion acting as a bearing surface against which said hanger assembly is engaged, said shoulder portion bearing the weight of said hanger assembly, said drive means and a pump rod when attached thereto.

6. The stuffing box assembly as claimed in claim 2 wherein said primary housing includes one or more locking mechanisms to retain said hanger assembly within said primary housing.

7. The stuffing box assembly as claimed in claim 6 wherein said one or more locking mechanisms comprise one or more lock down screws.

8. The stuffing box assembly as claimed in claim 2 wherein said drive means includes torque input means permitting for the transference of rotational torque from a power source to said drive means and to a pump rod attached thereto.

9. The stuffing box assembly as claimed in claim 8 wherein said torque input means comprises a recess in the upper end of said drive means and said power source comprises an electric or hydraulic motor, said recess configured and sized to accept the shaft of said electric or hydraulic motor such that the operation of said motor causes a direct rotation of said drive means.

10. The stuffing box assembly as claimed in claim 2 wherein said drive means comprises a rotatable mandrel.

11. The stuffing box assembly claimed in claim 10 wherein said hanger assembly is hung and supported within the longitudinally oriented hollow bore of said primary housing by a shoulder portion on said primary housing.

12. The stuffing box assembly is claimed in claim 11 wherein said rotatable mandrel has a longitudinally oriented hollow bore for receiving a pump rod there through.

13. The stuffing box assembly as claimed in claim 12 wherein, the hollow bore through said rotatable mandrel has a reduced diameter portion, said mandrel including slips to engage a pump rod received through said hollow bore in said mandrel, said slips engaging the pump rod at said reduced diameter portion in order to hang the pump rod from said mandrel such that rotation of said mandrel causes a simultaneous rotation of the pump rod.

14. The stuffing box assembly as claimed in claim 12 including a rod clamp, said rod clamp operatively securing the pump rod to said rotatable mandrel such that rotation of said mandrel causes a corresponding rotation of the pump rod, said rod clamp further transferring the axial or longitudinal load of the pump rod to said rotating mandrel.

15. The stuffing box assembly as claimed in claim 9 wherein said shaft of said motor includes a longitudinal hollow bore extending therethrough, when said shaft of said motor is received within said recess in the upper end of said drive means said longitudinal bore in said motor shaft is in fluid communication with a longitudinally oriented hollow bore extending through at least the upper end of said drive means, said bore in said drive means having at least one transverse oriented exit port in communication with the exterior surface of said drive means, said bore extending through said shaft of said motor being at least partially filled with lubricant and having associated therewith pressurization means to pressurize said lubricant, said pressurization means forcing said lubricant through said shaft of said motor into said bore within the upper end of said drive means and through said transverse exit port, said lubricant assisting in the lubrication of said seals and pressurizing the interior of said stuffing box.

16. The stuffing box assembly as claimed in claim 15 wherein said pressurization means pressurizes said lubricant to a level such that the lubricant pressure within said stuffing box exceeds the pressure of fluids within a well upon which said stuffing box is mounted to help prevent the flow of well fluids into said stuffing box.

17. The stuffing box assembly as claimed in claim 16 wherein the upper end of said longitudinal bore extending through said shaft of said electric or hydraulic motor is sealed, said pressurization means situated within said longitudinal bore in said motor shaft.

18. The stuffing box assembly as claimed in claim 17 wherein said pressurization means comprises a spring or gas actuated piston.

19. The stuffing box assembly as claimed in claim 2 including an external source of pressurized lubricant connected to the interior of said hanger assembly, said pressurized lubricant lubricating said one or more seals and pressurizing said hanger assembly to a higher pressure than the pressure of a wellbore upon which said stuffing box is mounted to help prevent the flow of well, fluids into said hanger assembly.

20. The stuffing box assembly as claimed in claim 1 in combination with a casing head, said casing head including one or more side entry passageways to permit the introduction of coiled tubing or other tubular or elongate member into the wellbore of a wellhead onto which said stuffing box assembly is mounted, said introduction of said coiled tubing or other tubular or elongate member occurring at a point below said stuffing box assembly and without the removal of said stuffing box assembly from the wellhead.

21. A casing head for securing to the upper end of the casing of a well extending into an underground formation, the casing head including one or more side entry passageways to permit the introduction of coiled tubing or other tubular or elongate member into the wellbore of the casing without the removal of wellhead equipment positioned above said casing head.

22. The casing head as claimed in claim 21 including removable plugs in said one or more side entry passageways to help prevent the ingress of debris into the wellbore and the escape of fluids from the wellbore.

23. The casing head as claimed in claim 22 wherein said one or more side entry passageways are arranged with their longitudinal axes at a shallow angle relative to the centerline of the wellhead to permit the coiled tubing or other tubular or elongate member to be inserted at a shallow angle of approach relative to the casing and any tubing string that may be received therein.

24. A stuffing box assembly comprising: a primary housing;a removable hanger assembly releasably and sealingly receivable within a longitudinally oriented hollow bore extending through said primary housing, said hanger assembly having a longitudinally oriented hollow bore extending therethrough; and,drive means sealingly receivable within said hanger assembly and extending through said hollow bore within said primary housing when said hanger assembly is received therein, said drive means including torque input means permitting for the transference of rotational torque from a power source to said drive means, said drive means having means to releasably secure said drive means to a pump rod such that rotation of said drive means causes a corresponding rotation of the pump rod when secured thereto, said drive means including one or more seals between said drive means and the pump rod,when said hanger assembly is received within said primary housing said hanger assembly hanging said drive means, and a pump rod when attached thereto, from said primary housing, said hanger assembly including bearings to facilitate the rotation of said drive means, said hanger assembly including one or more seals to seal against the exterior surface of said drive means to help prevent the flow of fluid between said drive means and said hanger assembly.

25. A stuffing box assembly comprising; a primary housing;a hanger assembly within a longitudinally oriented bore extending through said primary housing, said hanger assembly having a longitudinally oriented bore extending therethrough; and,drive means sealingly received within said hollow bore of said hanger assembly, said drive means including torque input means permitting for the transference of rotational torque from a power source to said drive means, said drive means having means to releasably secure said drive means to a pump rod such that rotation of said drive means causes a corresponding rotation of the pump rod when secured thereto,said hanger assembly hanging said drive means, and a pump rod when attached thereto, from said primary housing, said hanger assembly including bearings to facilitate the rotation of said drive means, said hanger assembly including one or more seals to contain well fluids and to help prevent the flow of well fluid into said bore in said hanger assembly.

26. The stuffing box assembly as claimed in claim 25 wherein said drive means is a rotating mandrel, said rotating mandrel having a longitudinally oriented hollow bore for securedly receiving the pump rod therein such that rotation of the rotating mandrel causes a corresponding rotation of the pump rod.