WO2006014166A2

WO2006014166A2 - Linear drive assembly with rotary union for wellheads

Info

Publication number: WO2006014166A2
Application number: PCT/US2004/021627
Authority: WO
Inventors: Carl G. Waldenstrom; Michael A. Keffer
Original assignee: Applied Energy Products, Llc
Priority date: 2004-07-06
Filing date: 2004-07-06
Publication date: 2006-02-09
Also published as: US20080257555A1; WO2006014166A3

Abstract

A drive assembly for a progressive cavity pump includes a frame supported by the wel piping and a polish rod connected to the sucker rod. The polish rod is received by a rotary union formed by a sleeve portion rotatable with respect to a body portion with a seal structure that seals the sleeve and body portions during rotation. A mechanical drive, such as a hydraulic motor, electric motor or engine, has an output shaft that is linear with the polish rod and that has an axial passageway which receives the polish rod. A coupler mechanically couples an upper portion of the polish rod to the output shaft. The invention also includes a method of rotating a progressive cavity pump by this assembly.

Description

LINEAR DRIVE ASSEMBLY WITH ROTARY UNION FOR WELL HEAD APPLICATIONS AND METHOD IMPLEMENTED THEREBY

FIELD OF THE INVENTION

The present invention broadly concerns wells and drive assemblies therefore along with methods for pumping fluids from a down hole location in the well to the surface. More particularly, the present invention is directed to a linear drive assembly and pump assemblies incorporating in the same so that torque forces on the assembly are reduced. The invention specifically is directed to a drive assembly for a progressive cavity pump. The invention also relates to a rotary seal that may be used with these and other pump assemblies. Further, the invention is directed to methods accomplished by these pump assemblies.

BACKGROUND OF THE INVENTION

Since ancient days, humankind has been known to settle around convenient sources of fresh water, such as lakes, rivers, streams, springs and the like. These sources are normally exposed at the surface of the earth for ready access. However, early on it was further learned that subterranean water supplies could be tapped by digging or otherwise forming an access passageway to an underground source of water. In the last several hundred years, it has also been learned that water is not the only natural resource that may be found in subterranean formations. Primary among these are petroleum resources in the form of complex hydrocarbon chemicals that may be found in a fluid state. This can include both liquid oil as well as hydrocarbon gases.

Accordingly, it is known that wells can be drilled into such formations in order to tap these various resources, and often, an associated artificial lift is used to produce the resource from these wells. Such a pumping assembly, on one hand, may be used to withdraw the targeted resource from the well. On the other hand, the pumping assembly may be used to remove an unwanted material in a particular well application. An example of this latter situation is a natural gas well. Here, it is quite common for both the natural gas and fluid water to be present in the well. Should the pressure head from the column of water exceed the pressure of the gas in the formation, the gas cannot rise out of the well for collection. Accordingly, pumps are provided to remove water from such wells in order that the gas may travel upwardly through the well casing. One such type of pump is known as the progressive cavity pump that includes a rotor and a stator located down hole. The rotor is rotated by means of a sucker rod that extends upwardly through the delivery production tube to a location proximate the wellhead. A polish rod is connected to the sucker rod, and a drive assembly rotates the polish rod thereby to rotate the sucker rod so that the progressive cavity pump delivers fluid from the bottom of the well.

With this structure, it is necessary that the production tube be sealed and that sealing contact be made between the rotating polish rod and the production tube via such seal. In order to accommodate this need, it has been known in the past to provide a device known as a "stuffing box" that is mounted to a base secured to a well tubing. The stuffing box creates the seal and is constructed as a winding of carbon impregnating rope or the like located in the interior of the stuffing box. The polish rod extends through the stuffing box so that the surface of the polish rod is in pressurized contact with the carbon-impregnated rope in an attempt to form a rotatable seal between the polish rod and the stuffing box.

Problems result from this solution to providing a rotary seal, however. For example, if the carbon-impregnated rope is compressed too much against the polish rod, abrasion will form a groove in the polish rod which can cause severe leakage of the system. Such leakage is not only uneconomical, but it may also result in environmental damage. Indeed, such wells are monitored for leakage and any discovered leakage may result in a large fine to the operator.

It may also be appreciated that some form of a mechanical drive is necessary to rotate the polish rod so as to drive the pump. In the past, these drives have been of two primary types. On one hand, the polish rod may be driven by an electric motor. Such motors are usually constant speeds unless provided with fairly complicated and expensive frequency controller. Thus, the pumping speed is relatively constant. A second type of mechanical drive is the hydraulic motor. Here, hydraulic fluid is pumped from a hydraulic pump through the hydraulic motor which causes a drive shaft to rotate. The speed of the hydraulic motor may be varied by varying the flow of hydraulic fluid therethrough.

In either case, the conventional drive is usually mounted laterally of the polish rod. Here, the polish rod is provided with a pulley, and a second pulley is mounted to the output shaft of the mechanical drive. A drive belt then interconnects the output shaft and the polish rod so that rotation of the output shaft serves to rotate the polish rod thereby to power the pump. Such mounting, however, has many disadvantages. Various bearings in the assembly may become worn because of the torque created by the offset drive. The drive belts can wear and stretch so that substantial maintenance must be provided to maintain proper tensioning of the belt. If such drive belt breaks, naturally there would be no pumping in the well. Moreover, the bearing box which supports the weight of the polish rod, the sucker rod and the fluid in the well must be externally lubricated and maintained on a regular basis.

While the above systems have been very useful in the past to drive rotary pumps, there remains a need for improved drive assemblies for progressive cavity pumps. There remains a need for drive assemblies that incorporate improved seal structures that can eliminate the disadvantages of the stuffing box. In addition, there is a need for such drive assemblies that reduce the lateral torque resulting from an offset mount. The present invention is directed to meeting these needs.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and useful drive assembly for progressive cavity pumps that may be used in a well provided with a delivery tube that extends from the surface location to a progressive cavity pump situated at a down hole location.

It is another object of the present invention to provide a new and useful rotating seal for a polish rod, for example, in progressive cavity pump applications.

It is a further object of the present invention to provide a drive assembly and method for a pump that eliminates torque forces resulting from offset side mounting of the drive assembly.

It is a still further object of the present invention to provide a drive assembly for progressive cavity pumps that has reduced risk of leakage and greater mechanical integrity.

According to the present invention, then, a drive assembly is provided for a progressive cavity pump. Here, the progressive cavity pump is located down hole in a well that is provided with a casing and a delivery tube with an interior and a sucker rod located in the delivery tube interior. The drive assembly includes a frame having a base portion adapted to be supported by the piping when the drive assembly is in an assembled state. A polish rod includes a lower end portion adapted to be connected to the sucker rod when in the assembled state whereby rotation of the polish rod acts to rotate the sucker rod. A rotary union is provided and includes a body portion and a sleeve portion secured together and adapted to receive the polish rod therethrough. The body portion and the sleeve portion are relatively rotatable with respect to one another and a seal structure is operative to substantially seal the body portion and the sleeve during rotational movement thereof. A mechanical drive is then supported by the frame when in the assembled state. The mechanical drive includes a drive body and a hollow output shaft extending along a linear drive axis. The shaft has an axial passageway therethrough that is sized and adapted to receive the polish rod such the polish rod is surrounded by the drive body. A coupling member is then operative to mechanically couple the output shaft and an upper portion of the polish rod whereby rotation of the output shaft rotates the polish rod and the sucker rod when in the assembled state. Examples of mechanical drives contemplated include hydraulic motors, electric motors, combustion engines, gearboxes and combinations of these assemblies.

In the rotary union used with this drive assembly, the sleeve portion mateably engages the body portion and includes at least one bearing element rotatably supporting the sleeve portion with respect to the body portion. The seal structure, for example, includes a first seal element constructed of a carbon material and a second seal element constructed of a ceramic material. A biasing spring is operative to bias the first and second seal elements together. Here, the first and second seal elements confront one another for rotationally sliding engagement whereby a substantial seal is maintained between the first and second seal elements during rotation of the sleeve portion relative to the body portion. The first and second seal elements may each have an annular shape, and the second seal element may be slidably disposed for axial movement within the body portion. Here, a pair guide pins may be mounted to the body portion to prevent rotation of the second seal element, and the second seal element is then supported by the guide pins. The body portion of the rotary union may also have a port formed therein approximate to the interface between the first and second seal elements. A friction cap is provided and is connected to an exposed portion of the sleeve portion for common rotation therewith when in the assembled state. This friction cap includes at least one friction cap seal operative to substantially seal against both the sleeve portion and the polish rod when in the assembled state.

In the disclosed embodiments, the mechanical drive includes a bearing member that axially supports the drive shaft and is operative to support a load, and it is desirable that it be capable of supporting at least 5000 pounds. The mechanical drive may also include a rotary speed detector element operative to monitor rotational speed of the output shaft. Here, the rotary speed detector may include a gear element secured to the output shaft with this gear element having peripheral gear teeth. A proximity switch is then disclosed proximate to the peripheral gear teeth and is operative to count consecutive ones of the peripheral teeth when the gear element is rotated thereby to indicate the rotational speed of the output shaft. The output shaft may include an exposed portion extending axially out of the drive body. This exposed portion may have a key structure formed thereon, and the coupler member may have a key way that is sized and adapted to engage this key structure. For example, the coupler member may be a friction block. This friction block may be detected by a shield supported by the frame so that the shield is in surrounding relation to the coupler member. A slinger element may also interface the coupler member in the frame.

The base portion of the frame is adapted to connect it to the piping and includes a stool portion connected to the base portion having a stool interior. Here, it may be understood that the piping may include a cross-member, and the base portion is then connected to the cross-member. In any event, the rotary union is disclosed to be located in the interior of the stool when in the assembled state.

The method of the present invention may include any of the steps accomplished by the above-described structure. Accordingly, the invention contemplates the method of rotating a progressive cavity pump that is located down hole in a well wherein the well includes piping including a casing and a delivery tube extending downwardly from a surface location. Here, also, the well includes a rotatable sucker rod that extends upwardly from the down hole location through the delivery tube toward the surface location and wherein the polish rod is connected to the sucker rod such that rotation of the polish rod acts to rotate the sucker rod and where rotation of the sucker rod acts to rotate the rotor of a progressive cavity pump thereby to deliver fluid to the surface location. Broadly, the method includes the step of providing a mechanical drive that includes an axially oriented drive shaft that is hollow so as to have an axial passageway therethrough. The method then contemplates mounting the mechanical drive generally vertically of the casing with the polish rod extending through the axial passageway of the output shaft. The polish rod and the output shaft are then coupled whereby rotation of the output shaft will rotate the polish rod. This method provides a rotary union between the polish rod and the delivery tube thereby to substantially seal the delivery tube while allowing rotation of the polish rod wherein. Here, the rotary union includes a body portion and a sleeve portion that are relatively rotatable with respect to one another and wherein the rotary union includes a seal structure between the body portion and the sleeve portion. The method then includes coupling the sleeve portion to the polish rod in a substantially sealed manner.

In this method, the mechanical drive may be selected from a group consisting of hydraulic motors, electric motors, combustion engines, gearboxes and combinations of the same. The mechanical drive may be supported by a cross-fitting that is supported by the piping.

This method may also include the step of monitoring the rotational speed of the output shaft. The step of monitoring may be accomplished by detecting the speed of peripheral gear teeth of the gear element mounted to the output shaft. The step of protecting the speed of the peripheral gear teeth may be accomplished by a proximity switch disposed proximate to the peripheral gear teeth and operative to count consecutive ones of the peripheral teeth when the gear element is rotated thereby to indicate the rotational speed of the output shaft.

The method may also include the step of monitoring the level of fluid in the casing and/or delivery tube and adjusting the rate of rotation of the output shaft in response thereto. When the mechanical drive is a hydraulic motor, the step of adjusting the rate of rotation of the output shaft can be accomplished by varying the selected rate of which the hydraulic fluid is pumped through the hydraulic motor.

These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiments of the present invention when taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagrammatic view according to the prior art showing a well provided with a progressive cavity pump and a drive assembly;

Figure 2 is a perspective view of the drive assembly according to a first exemplary embodiment of the present invention;

Figure 3 is a side view in cross-section showing the base portion of the frame used to support the drive assembly of Figure 2; Figure 4 is a side view in cross-section of the rotary union and friction cap according to the present invention;

Figure 5 is a side view in elevation showing the hydraulic motor according to a first exemplary embodiment of the present invention;

Figure 6 is a top plan view of the hydraulic motor of Figure 5;

Figure 7 is a bottom plan view of the hydraulic motor of Figure 5;

Figure 8 is a side view in cross-section taken about lines 8-8 of Figure 5;

Figure 9 is an exploded perspective view of a coupler in the form of a friction block used in the first exemplary embodiment of the present invention;

Figure 10 is a bottom plan view of the friction block of Figure 9 shown in an assembled state;

Figure 11 is a side view in elevation showing a second exemplary embodiment of a drive assembly according to the present invention; and

Figure 12 is a side view in elevation showing a third exemplary embodiment of a drive assembly for a progressive cavity pump according to the present invention. DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The present invention broadly concerns drive assemblies and methods for driving a progressive cavity pump that is located down hole in a well. Here, such wells are known to be provided having a casing interior and a sucker rod located in a delivery tube within the casing interior whereby rotation of the sucker rod acts to rotate the progressive cavity pump. In the exemplary embodiments, the drive assembly is a linear drive having an output shaft that is coaxial with a polish rod that is connected to the sucker rod. Another aspect of the exemplary embodiments of the present invention includes a rotary union that substantially seals the production flow through the delivery tube and that includes a friction cap that seals against the polish rod with the rotary union providing a rotary seal whereby the polish rod may be rotated in a substantially sealed rotation in the rotary union.

In order to introduce the aspects of the present invention, reference may be first made to Figure 1 which is a diagrammatic view of a well provided with a progressive cavity pump and a drive assembly for that pump, all according to the prior art. In Figure 1 , it may be seen that well 10 includes a casing 12 that extends from a down hole location upwardly to a surface location to form a wellhead 14. A water delivery tube 16 is located coaxially within casing 12, and a progressive cavity pump 18 is provided with a rotor and is located at the down hole location within the interior of water delivery tube 16. A sucker rod 20 is located axially within water delivery tube 16 such that rotation of the sucker rod 20 acts to rotate progressive cavity pump 18 thereby to pump fluid from the down hole location to the surface location.

With continued reference to Figure 1 , a drive assembly 22 is provided to rotate sucker rod 20. Here it may be seen that drive assembly 22 includes a frame 24 that is mounted on cross-member 26 that, as is known in the art, communicates with the interior 13 of casing 12 so as to separate, for example, oil and natural gas from well 10. A stuffing box 28 rotatably receives a polish rod 30 therethrough with polish rod 30 being connected to sucker rod 20 whereby rotation of polish rod 30 will act to rotate sucker rod 20 thereby to drive pump 18. A bearing box 32 is mounted at an upper portion of frame 24 and the friction block 34 is mounted on an upper exposed end portion of polish rod 30 so that the weight of the polish rod 30, sucker rod 20 and any fluid in delivery tube 16 is supported by bearing box 32. A pulley 36 is attached to the output shaft of the bearing box at a location between bearing block 32 and friction block 34. A drive motor 40 has an output shaft 42 that is connected to a pulley 44 with pulley 44 acting to drive pulley 36 by means of a belt 38.

As noted above, the arrangement shown in Figure 1 has several disadvantages. On one hand, stuffing box 28 may be subject to leakage. This may be exacerbated by the offset mount of motor 40 with respect to the axis of polish 30 since this creates side loads and corresponding torques. The bearings in bearing box 32 and the drive motor 40 may become worn due to this side load. Moreover, the system shown in Figure 1 requires substantial maintenance, including adjusting or replacing belts 38 and the lubrication of bearing box 32. The inventive aspects of the disclosed embodiments are provided to reduce these issues.

Accordingly, a drive assembly for a progressive cavity pump according to a first exemplary embodiment of the present is introduced in Figure 2. Here, drive assembly 50 includes a frame 52 that includes a base portion 54 that is adapted to be supported by the piping of the well when in an assembled state. In Figure 2, it may be seen that base portion 54 is supported on a standard adapter fitting (not shown) internal of hollow shank 55 to secure to cross member 26 thereby to support it relative to casing 12. A stool portion 56 extends upwardly from base portion 54 and is formed by three upright members 58 so as to have an open interior 60. An annular top plate 62 is supported by upright members 58 and vertically spaced, parallel relation to base 54.

Drive assembly 50 is provided with a rotary union 64, the more detailed structure of which is described below, with rotary union 64 being threadably mounted into base portion 54. A friction cap 66 (with a pressure seal) is secured to rotary union 64, and it may be seen that polish rod 30 is coaxial with rotary union 64 and friction cap 66 and extends completely therethrough.

Similarly, polish rod 30 has an upper portion 33 that extends through a mechanical drive in the form of a hydraulic motor 68 that is supported on top plate 62. Friction block 34 clamps onto upper portion 33 of polish rod 30 and is enclosed by a cylindrical shield 70 and an annular rubber disc 72 that is slightly larger in diameter that shield 70. This disc 72 is secured by friction to polish rod 32 and may be referred to as a "slinger". It rotates with upper portion 33 of polish rod 32 and to any build-up of water, snow, dirt, debris and the like from its surface by centrifugal force. A hydraulic pump 74 is shown in diagrammatic form, and supplies hydraulic fluid to hydraulic motor 68 whereby flow of hydraulic fluid through conduits 76 and 78 causes the output shaft of the hydraulic motor to rotate, as described more thoroughly below.

With reference now to Figure 3, it may be seen that base portion 54 is adapted to be supported on the piping of the well. Here, it should be understood that the term "piping" may be either the well casing, the delivery tube or the cross- member. Base portion 54 is shown in Figure 3 to include a central cylindrical tube 80 to which an annular base plate 82 is connected. Tube 80 is internally threaded, at 84, so that it may threadably mate onto cross-member 26 by means of a standard threaded adapter fitting. An annular stanchion 86 is located on a side of plate 82 opposite tube 80 and mates with central opening 88 and lower annular base plate 90 of stool 56.

The exemplary embodiments of the present invention employ a new and useful rotary union that is best shown in Figure 4. Here, rotary union 64 is depicted and includes a body portion 92 and a sleeve portion 94 which is telescopically received in the interior of body portion 92 with body portion 92 and sleeve portion 94 being coaxial with one another. Sleeve portion 94 is supported for rotational movement with respect to body portion 92 by means of a pair of bearings 96 that are separated from one another by means of a bearing separator ring 98 and which are held in position by means of retaining rings 100 and 102. An outer portion of the sleeve portion 94 extends outwardly of body portion 92.

Body portion 92 has a threaded shank 104 that is adapted to thread into threads 85 of tube 80. Shank 104 is of reduced diameter so as to provide a shoulder 106 that will abut stanchion 86 when in the assembled state. Moreover, body portion 92 includes a central axially extending cavity 108 that is sized such that polish rod 30 may extend therethrough.

As noted above, sleeve portion 94 is mounted by bearings 96 for relative rotation with respect to body portion 92. Sleeve portion 94 includes an axially extending cavity 110 sized to received polish rod 30 therethrough. Sleeve portion 94 has an upper threaded shank 112 with a shoulder 114 supporting a washer 116. A circumferential groove 118 is provided to mount an annular rubber disc 120. This disc 120 is secured to sleeve portion 94 by friction and may be again be referred to as a "slinger". It rotates with sleeve portion 94 and serves to any build-up of water, snow, dirt, debris and the like from its surface by centrifugal force.

It should now be appreciated that sleeve portion 94 may freely rotate with respect to body portion 92 that is affixed to base member 54. However, it is also important that a fluid seal be maintained during this relative rotation. To this end, a seal structure is provided and, in the exemplary embodiment of the present invention, as illustrated in Figure 4, includes a first seal element 122 in the shape of an annular ring for example of a carbon compound that is mounted for axially sliding motion with respect to body member 92 by means of the pair of guide pins 124. First seal member 122 interfaces against the sidewall of cavity 108 to maintain a substantial seal therewith while undergoing such sliding motion. A second seal element 126 is an annular ring of ceramic material that is mounted to sleeve portion 94 and rotates correspondingly therewith. First seal element 122 and second seal element 126 have a rotationally sliding interface at 128 so that second seal element 126 maintains a substantially sealed relationship with first seal element 122 thereby relatively sealing body portion 92 and sleeve portion 94 during rotational movement. To facilitate this sealing interface at 128, first and second seal elements 122, 126 are axially biased towards one another. To this end, a biasing spring 130 is under compression and acts to axially advance first seal element 122 toward second seal element 126. With continued reference to Figure 4, cap member 66 is internally threaded so as to fit onto threaded shank 112. Friction cap 66 has a central opening 132 through which polish rod 30 may extend. A pair of compression O-ring gaskets 134 and 135 are located in the interior of friction cap 66 with O-rings 134 and 135 being separated from one another by means of an annular washer 136 a second washer 138 is provided between an upper O-ring gasket 134 and radially inwardly projecting flange 140 that defines central opening 132.

In assembly, friction cap 66 is threaded onto shank 112 so that O-ring 135 sealingly presses against rim 113 of shank 112 thereby providing a static seal against rim 113. This also acts to compress O-ring 134. Together, O-rings 134 and 135 seal against the surface of polish rod 30 when polish rod 30 extends through cavities 108 and 110 and through central opening 132. When polish rod is rotated, friction cap 66 as well as sleeve portion 94 undergo common, corresponding rotation while body portion 92 remains stationary in base 54. Seal elements 122 and 126 allow this rotation while maintaining a substantial seal so that any fluids that enter cavity 108 are prevented from leaking at the interface between sleeve portion 94 and base portion 92. Likewise, O-rings 134 and 135 prevent leakage around polish rod 30 and rim 113. A port 142 is provided through the sidewall of body member 92 at a location adjacent the seal structure formed by first and second seal elements 122, 126. This port helps prevent possible liquid build-up in the bearing area. Thus, port 142 can be used as a drain. Alternatively, port 142 may be fitted with a suitable leak detected device in order to monitor for any unwanted leakage at seal elements 122 and 126.

Another aspect of the first exemplary embodiment of the present invention resides in specially designed hydraulic motor 68. Hydraulic motor 68 is best illustrated in Figures 5-8. Here, it may be seen that hydraulic motor 68 includes an outer housing 144 which axially receives an output shaft 146 along the central drive axis thereof. Output shaft 146 includes linearly along the drive axis and has a axial passageway 148 therethrough that is sized and adapted to receive polish rod 30 therethrough. Thus, polish rod 30 is surrounded by the body of hydraulic motor 68 in the form of housing 144.

Output shaft 146 is supported for rotational movement relative to housing 144 by means of a lower bearing 150 and upper bearing 152 and a support bearing 154 that is constructed to withstand the load of polish rod 30, sucker rod 20 and any fluid in the well casing and/or delivery tube. To this end, support-bearing 154, which is located between bearings 150 and 152 proximate to bearing 152, should be robust enough to support the load without damage to hydraulic motor 68. For example, only, this load may be at least 5000 pounds. Hydraulic motor 68 includes ports 156 and 158 which are connected to conduits 76 and 78 so that hydraulic fluid may be pumped through motor 68. Such circulation rotatably drives output shaft 146 as is known in the art. Hydraulic motor 68 is further modified, however, by the inclusion of a gear 160 provided with peripheral gear teeth 162. A proximity switch 164 is mounted through housing 144 at a location proximate to gear 160 and acts to count the gear teeth 162 as output shaft 146 is rotated. The counting of the teeth accordingly correspond to the rate of rotation of shaft 146.

With reference to Figures 5, 6 and 8, it may be seen that output shaft 146 includes an axially exposed portion 166 that has a key structure 168 thereon. Key structure 168 is in the form of a stub shaft having a circular opening 170 formed therein to accommodate passage of polish rod 30. Key structure 168 is in the form of a rectangular stub shaft that is adapted to mate with friction block 34 with friction block 34 being further illustrated in Figures 9 and 10. In these figures, it may be seen that friction block 34 is formed by a pair of jaws 172 and 174 which may be clamped together by means of a plurality of bolts 176 each of jaws 172 has a channel formed therein such as channel 173 in jaw 172 and channel 175 in jaw 174. When assembled, channels 173 and 175 register with one another to form a cylindrical passageway 178 through which polish rod 30 may extend. Rectangular cutouts 178 and 179 are provided at one end of each channel 173, 175 so that, when jaws 172 and 174 are connected, cutouts 178 and 179 define a keyway 180 that receives key structure 168 of output shaft 146.

With reference again to Figure 2, the assembly of drive assembly 50 according to this exemplary embodiment of the present invention may be fully appreciated. Polish rod 30 extends axially completely through drive assembly 50, and friction block 34 clamps onto upper end portion 33 of polish rod 30 to bear the weight thereof. Moreover, when friction block 30 is so mounted, key way 180 engages key structure 168. Moreover, this mounting transfers the weight of polish rod 30 onto output shaft 146 with this weight ultimately being born by support bearing 154 (Figure 8). Polish rod 30 extends downwardly through hydraulic motor 68, through friction cap 66 and through rotary union 64. Friction cap 66 is secured to rotatable sleeve portion 94 of rotary union 64 and, when screwed onto sleeve portion 94, seals against the outer surface of polish rod 30. Polish rod 30 extends through body portion 92 of rotary union 64 with sleeve portion 94 and body portion 92 being sealed for rotational movement as described above. Polish rod 30 extends downwardly through base portion 54, through cross-member 26 and into well casing 12 so that it has its lower end portion 31 connected to sucker rod 20, as illustrated in Figure 1.

In operation, the passage of hydraulic fluid through hydraulic motor 68 causes output shaft 146 to rotate. This acts to rotate friction block 34 and, due to the clamping of friction block 34 onto polish rod 30 acts to rotate polish rod 30 and, sucker rod 20 and progressive cavity pump 18. This rate of rotation is monitored by the detector in the form of proximity detector 164 that counts the consecutive gear teeth on gear 162. A leak detector 182 may be mounted in the sidewall of rotary union 64 to monitor for any unwanted leakage from first and second seal elements 122, 126.

A second exemplary embodiment of the present invention is illustrated in Figure 11. Here, drive assembly 250 employs an electric motor 268 instead of hydraulic motor 68. Sucker rod 30 extends axially through motor 68 with the output of motor 68 driving a planetary gear box 270 that is suitably provided with bearings robust enough to support the weight of polish rod 30, sucker rod 20 and the fluid in the well casing and/or delivery tube. Planetary gear box 270 includes an output shaft 276 that has a key structure engaging friction block 34 as described above. Moreover, it should be understood that output shaft 276 of planetary gear box 270 has an axial passageway therethrough through which polish rod 30 extends.

A third exemplary embodiment of the present invention is illustrated in Figure 12, here, drive assembly 350 again uses an electric motor 368 which may be optionally mounted above a spur gear reduction box 370 or below spur gear reduction box 370 (as shown in phantom). Again, spur gear reduction box 370 includes an output shaft 376 that engages friction block 34 so that rotation of output shaft 376 rotates polish rod 30 that is sealed by friction cap 66 and rotary union 64. Reduction gear box 370 is provided with bearings that are sufficiently robust to support the weight of polish rod 30, sucker rod 20 and the fluid in the well casing.

While the exemplary embodiments of the present invention have been described, on one hand, with respect to a hydraulic motor and, on the other hand, with respect to an electric motor, it should be understood that any suitable mechanical drive may be employed. Thus, in addition to hydraulic motors and electric motors, any mechanical drive may be an internal combustion engine, such as an rotary combustion engine, or may even be considered to be a gear box, such as gear boxes 270 and 370 which are driven but which have an output shaft to rotate sucker rod 30. Accordingly, it is contemplated that all such mechanical drives, currently existing or hereinafter developed may be employed to rotate sucker rod 30 with rotary union 64 maintaining the seal.

In addition to the structures described above, it should be further appreciated that the present invention contemplates a method implemented by any of these structures. Broadly, this method includes the step of providing a mechanical drive that includes an axially oriented drive shaft that has an axial passageway therethrough. The method then includes mounting the mechanical drive generally vertically of the casing of the well with the polish rod extending through the actual passageway of the output shaft. The method then includes the step of coupling the polish rod and the output shaft whereby rotation of the output shaft will rotate the polish rod. The method further includes providing a rotary union between the polish rod and the casing thereby to substantially seal the casing while allowing rotation of the polish rod and wherein the rotary union includes a body portion and a sleeve portion that are relatively rotatable with respect to one another and wherein the rotary union includes a seal structure between the body portion and the sleeve portion. The method then includes coupling the sleeve portion to the polish rod in a substantially sealed manner.

In this method, the mechanical drive may be supported by a cross-fitting that is supported by the piping, e.g., the delivery tube or the dross-member. The method may include the optional step of monitoring the rotational speed of the output shaft. Where this step is undertaken, the monitoring may be accomplished by detecting the speed of peripheral gear teeth of the gear element mounted to the output shaft. This detection may be accomplished by means of a proximity switch disposed proximate to the peripheral gear teeth. The method may also include the step of varying the rate of rotation of the output shaft.

Accordingly, the present invention has been described with some degree of particularity directed to the exemplary embodiments of the present invention. It should be appreciated, though, that the present invention is defined by the following claims construed in light of the prior art so that modifications or changes may be made to the exemplary embodiments of the present invention without departing from the inventive concepts contained herein.

Claims

We claim:

1. A drive assembly for a progressive cavity pump located downhole in a well that is provided with piping and a sucker rod located in an interior region of the piping, comprising:

(A) a frame including a base portion adapted to be supported by said piping when said drive assembly is in an assembled state;

(B) a polish rod including a lower end portion adapted to be connected to said sucker rod when in the assembled state whereby rotation of said polish rod acts to rotate said sucker rod;

(C) a rotary union including a body portion and a sleeve portion secured together and adapted to receive said polish rod therethrough, said body portion and said sleeve portion being relatively rotatable with respect to one another and including a seal structure operative to substantially seal said body portion and said sleeve portion during rotational movement thereof;

(D) a mechanical drive supported by said frame when in the assembled state and including a drive body and an output shaft extending along a linear drive axis, said output shaft having an axial passageway therethrough that is sized and adapted to receive said polish rod such that said polish rod is surrounded by said drive body, said mechanical drive being selected from a group consisting of hydraulic motors, electric motors, combustion engines, and gear boxes; and

(E) a coupler member operative to mechanically couple said output shaft and an upper portion of said polish rod whereby rotation of said output shaft rotates said polish rod and said sucker rod when in the assembled state.

2. A drive assembly according to claim 1 wherein said base portion is adapted to connect to said piping and including a stool portion connected to said base portion and having a stool interior.

3. A drive assembly according to claim 2 wherein said rotary union is located in the stool interior when in the assembled state.

4. A drive assembly according to claim 1 wherein said sleeve portion matably engages said body portion and including at least one bearing element rotatably supporting said sleeve portion with respect to said body portion.

5. A drive assembly according to claim 1 wherein said seal structure includes a first seal element constructed of a carbon material and a second seal element constructed of a ceramic material.

6. A drive assembly according to claim 5 wherein said rotary union includes biasing spring operative to bias said first and second seal elements together.

7. A drive assembly according to claim 4 wherein said outer body portion has a port formed therein proximate to said seal structure.

8. A drive assembly according to claim 1 wherein said outer body portion is threadably connected to said base portion when in the assembled state.

9. A drive assembly according to claim 1 including a friction cap connected to an outer sleeve end of said sleeve portion for common rotation therewith when in the assembled state, said friction cap including at least one friction cap seal operative to substantially seal against both said sleeve portion and said polish rod when in the assembled state.

10. A drive assembly according to claim 1 wherein said mechanical drive includes a bearing member axially supporting said drive shaft and operative to support a load of at least 5000 pounds.

11. A drive assembly according to claim 1 wherein said mechanical drive includes a rotary speed detector operative to monitor rotational speed of said output shaft

12. A drive assembly according to claim 11 wherein said rotary speed detector includes a gear element secured to said output shaft and having peripheral gear teeth and further including a proximity switch disposed proximate to the peripheral gear teeth and operative to count consecutive ones of the peripheral teeth when said gear element is rotated thereby to indicate the rotational speed of said output shaft.

13. A drive assembly according to claim 1 wherein said output shaft includes an exposed portion extending axially out of said drive body, said exposed portion having a key structure formed thereon, said coupler member having a keyway sized and adapted to engage said key structure.

14. A drive assembly according to claim 1 wherein said coupler member is a friction block.

15. A drive assembly according to claim 1 including a shield supported by said frame so that said shield is in surrounding relation to said coupler member.

16. A drive assembly according to claim 15 including a slinger element interfacing said shield and the upper portion of said polish rod.

17. A drive assembly according to claim 1 wherein said mechanical drive is a hydraulic motor and including a hydraulic pump assembly operative to supply pressurized hydraulic fluid to said hydraulic motor.

18. A drive assembly for a progressive cavity pump located downhole in a well that is provided with piping and a sucker rod located in an interior of the piping, comprising:

(C) a rotary union adapted to receive said polish rod therethrough and operative to substantially seal the piping interior while allowing rotation of said polish rod, said rotary union including:

(1) a body portion;

(2) a sleeve portion matably engaging said outer body portion and rotatable with respect thereto;

(3) at least one bearing element rotatably supporting said sleeve portion with respect to said body portion; and

(4) a first seal element substantially sealing with said sleeve portion;

(5) a second seal element substantially sealing with said body portion, said first and second seal elements confronting one another for rotational engagement whereby a substantial seal is maintained between said first and second seal elements during rotation of said sleeve portion relative to said body portion;

(D) a mechanical drive supported by said frame when in the assembled state and including an output shaft; and

19. A drive assembly according to claim 18 wherein said first seal element has an annular shape and is constructed of ceramic and wherein said second seal element has and annular shape and is constructed of carbon compound.

20. A drive assembly according to claim 18 wherein said second seal element is slideably disposed for axial movement in said body portion.

21. A drive assembly according to claim 20 wherein said rotary union includes biasing spring operative to axially bias said first and second seal elements together.

22. A drive assembly according to claim 20 including a pair of guide pins mounted to said body portion, said second seal element supported by said guide pins.

23. A drive assembly according to claim 18 wherein said body portion of said rotary union has a port formed therein proximate to an interface between said first and second seal elements.

24. A drive assembly according to claim 18 wherein said body portion of said rotary union is threadably connected to said base portion when in the assembled state.

25. A drive assembly according to claim 18 including a friction cap connected to an outer sleeve end of said sleeve portion of said rotary union for common rotation with said sleeve portion when in the assembled state, said friction cap including at least one friction cap seal operative to substantially seal against both said sleeve portion and said polish rod when in the assembled state.

26. In a well provided with piping including a casing and a delivery tube extending from a surface location and having a casing interior, said well including a cross-fitting mounted to and upper end of said piping, a progressive cavity pump located downhole in said casing, a sucker rod connected to said progressive cavity pump and extending upwardly toward the surface location and a polish rod connected to said sucker rod whereby rotation of said polish rod acts to rotate said sucker rod and rotation of said sucker rod acts to rotate said progressive cavity pump thereby to pump fluid from a lower portion of said well through said delivery tube for discharge out of said cross-fitting, the improvement comprising a frame including a base portion secured to said cross-fitting and supported by said piping, a rotary union secured to said base portion and operative to substantially seal the piping interior, said rotary union receiving said polish rod therethrough and including a body portion and a sleeve portion secured together and being relatively rotatable with respect to one another and including a seal structure operative to substantially seal said outer body portion and said sleeve during rotational movement thereof, a mechanical drive supported by said frame and including a drive body and an output shaft extending along a linear drive axis, said shaft having an axial passageway therethrough that is sized and adapted to receive said polish rod such that said polish rod is surrounded by said mechanical drive, a coupler member operative to mechanically couple said output shaft and an upper portion of said polish rod whereby rotation of said output shaft rotates said polish rod.

27. The improvement of claim 26 wherein said rotary union includes at least one bearing element rotatably supporting said inner sleeve portion with respect to said outer body portion.

28. The improvement of claim 26 wherein said seal structure includes a first seal element and a second seal element axially confronting one another.

29. A drive assembly according to claim 28 wherein said rotary union includes a biasing spring operative to axially bias said first and second a first seal elements together.

30. The improvement of claim 26 wherein said outer body portion has a port formed therein proximate to said first seal element.

31. The improvement of claim 26 wherein said outer body portion is threadably connected to said base portion when in the assembled state.

32. The improvement of claim 26 including a friction cap connected to an outer sleeve end of said inner sleeve portion for common rotation therewith when in the assembled state, said friction cap including at least one friction cap seal operative to substantially seal against both said sleeve portion and said polish rod when in the assembled state.

33. The improvement of claim 26 wherein said mechanical drive is a hydraulic motor that includes a rotary speed detector element operative to monitor rotational speed of said output shaft.

34. The improvement of claim 33 wherein said rotary speed detector includes a gear element secured to said output shaft and having peripheral gear teeth and further including a proximity switch disposed proximate to the peripheral gear teeth and operative to count consecutive ones of the peripheral teeth when said gear element is rotated thereby to indicate the rotational speed of said output shaft.

35. The improvement of claim 26 wherein said output shaft includes an exposed portion extending axially out of said motor body, said exposed portion having a key structure formed thereon, said coupler member having a keyway sized and adapted to engage said key structure.

36. A method of rotating a progressive cavity pump located at a downhole location in a well that includes piping extending from a surface location and having an interior and wherein a rotatable sucker rod extends upwardly toward the surface location and wherein a polish rod is connected to said sucker rod whereby rotation of said polish rod acts to rotate said sucker rod and rotation of said sucker rod acts to rotate said progressive cavity pump thereby to pump fluid to the surface location, comprising:

(A) providing a mechanical drive that includes an axially oriented output shaft with an axial passageway therethrough;

(B) mounting said mechanical drive generally vertically of said piping with said polish rod extending through the axial passageway of said output shaft;

(C) coupling said polish rod and said output shaft whereby rotation of said output shaft will rotate said polish rod;

(D) providing a rotary union between said polish rod and said piping thereby to substantially seal the piping while allowing rotation of said polish rod wherein said rotary union includes a body portion and a sleeve portion that are relatively rotatable with respect to one another and wherein said rotary union includes a seal structure between said body portion and said sleeve portion; and

(E) coupling said sleeve portion to said polish rod in a substantially sealed manner.

37. A method according to claim 36 wherein said mechanical drive is supported by a cross-fitting that is supported by said piping.

38. A method according to claim 37 including a step of monitoring the rotational speed of said output shaft.

39. A method according to claim 38 wherein the step of monitoring the rotational speed is accomplished by detecting the speed of peripheral gear teeth of a gear element mounted to said output shaft.

40. A method according to claim 39 wherein detection of the speed of the peripheral gear teeth is accomplished by a proximity switch disposed proximate to the peripheral gear teeth and operative to count consecutive ones of the peripheral teeth when said gear element is rotated thereby to indicate the rotational speed of said output shaft.

41. A method according to claim 40 including the step of adjusting the rate of rotation of said output.

42. A drive assembly according to claim 41 wherein the mechanical drive is a hydraulic motor and wherein the step of adjusting the rate of rotation of said output shaft is accomplished by varying the selected rate at which hydraulic fluid is pumped through said hydraulic motor.

43. A drive assembly for a progressive cavity pump located downhole in a well that is provided with piping having an interior and a sucker rod located in the interior, comprising:

(C) a rotary union and friction cap assembly adapted to receive said polish rod therethrough and operative to substantially seal the piping interior and to substantially seal against said polish rod while allowing rotation of said polish rod therein when in the assembled state;

(D) a hydraulic motor supported by said frame when in the assembled state and including a motor body and an output shaft extending along a linear drive axis, said shaft having an axial passageway therethrough that is sized and adapted to receive said polish rod such that said polish rod is surrounded by said hydraulic motor; and