Tubing saver rotator and method for using same

[0001] U.S. Provisional Application for Patent No. 60/371,393, filed Apr. 10, 2002, with title Tubing Saver Rotator and Method For Using Same which is hereby incorporated by reference. Applicant claims priority pursuant to 35 U.S.C. Par. 119(e)(i).

[0002] Not Applicable

[0003] 1. Field of the Invention

[0004] This invention relates to a tubing rotator assembly that sits inside a casing head for purposes of suspending and rotating the tubing string in an oil well.

[0005] 2. Brief Description of Prior Art

[0006] A typical wellhead is often comprised of a casing head which engages or is otherwise mounted to a casing string contained within a wellbore of a well at the surface. A mandrel bowl is mounted to the casing head and provides a support mechanism for the tubing string which is contained within the wellbore.

[0007] The production of fluids from an oil and gas well often involves the use of a downhole pump that can pump fluids to the surface through the tubing string. This downhole pump is often mechanically actuated through the use of a rod string located within the tubing string. The rod string is usually reciprocated up and down at the surface or, rotated at the surface to impart motion on the pump. The reciprocation or rotation of the rod string causes the rods to wear against the tubing, which may cause the tubing string to wear thin and develop a hole in the tubing. This wear action also wipes off chemical inhibitors that may be placed into a well to minimize corrosion of the tubing and rods by the production fluids. Thus, the wear action can also lead to tubing holes due to corrosion since the inhibitors are wiped off. These wear related holes in the tubing causes inefficient lift or no lift of the fluids to the surface and typically requires a rig to service the well. Reducing the failure frequency of the tubing strings will not only reduce operating costs but also will allow additional oil to be developed by reducing the economic production rate limit of each well.

[0008] Since 1927, several patents have been obtained on variations to tubing rotators that generally rotate the tubing manually or automatically to attempt to reduce the frequency of tubing holes developed due to the wearing action of the rods. Conventional casing heads are not typically able to be retrofitted to accommodate the necessary structure of a tubing rotator. Further, the tubing rotators of the prior art typically use gears and drive assembly to rotate the tubing. As a result, a housing is normally required to be attached above the casing head to provide room for the gearing and allow a rod to exit the tubing rotators of the prior art to allow manual rotation or automatic/continuous rotation of the tubing string.

[0009] These prior art designs therefore often include several seals to seal off the rod attached to the gears, seal the fluids between the casing and tubing, and further seal fluids produced up the tubing from exiting the tubing string into the atmosphere, ground, or annulus between the tubing and casing. The rotators with continuous rotation commonly have more corrosion holes due to wear than a manual or intermittent rotator, and fail when a gear mechanism fails and may damage the rotator or wellhead assembly due to the torque imparted on the gears. In addition, the positioning of a housing on top of the casing head is more costly and may involve the need to raise the pumping unit due to large spacing requirements between the casing head and the pump tee.

[0010] As will be seen from the subsequent description, the preferred embodiments of the present invention overcome these and other shortcomings of prior art.

[0011] There is need for a compact tubing rotator that may be operated manually, reduces the height clearance between the casing head and the pump tee, is inexpensive, has minimal seals to potentially fail and leak fluids, provides for replacement of rubbers or seals that protect the atmosphere and environment from leaking fluids without removing the tubing rotator or tubing string from the well, provides additional seals to minimize or stop contamination of the grease packed bearing housing from wellbore or external fluids, utilizes commonly available equipment to reduce costs of repairs, and provides ease of installation and use.

[0012] The present invention is an apparatus for attachment within an existing casing head or within a casing head modified to accept a bowl or ledge assembly. In the preferred embodiment, this apparatus has a bearing in which a tubing mandrel rests and allows one to rotate the tubing manually above the wellhead. It provides a low profile reducing the distance between the casing head and the pumping tee, which may eliminate the need for one to raise the pumping unit to fit on the rotator. In addition, the conventional seals located above the bowl assembly have less chance of leaking fluids located between the casing and tubing as a result of the seals installed in the present invention. In addition, if the conventional rubber element starts to leak, then one can change the sealing elements without having to remove the tubing rotator assembly or tubing string from the well.

[0013] This invention relates to a tubing rotator assembly that sits in a casing head for purposes of suspending and rotating the tubing string in an oil well. The assembly includes a mandrel bowl or mandrel support that rests in the casing head. The mandrel bowl has an interior ledge with a surface on which a bearing may be placed. A tubing mandrel is partially contained within the interior of the mandrel bowl with one end exiting the bottom of the mandrel bowl and attached to the tubing string in the well, and the opposite end of the tubing mandrel exiting the top of the mandrel bowl. The tubing mandrel has a ledge which is rotatably mounted to the mandrel bowl. Said ledge of the tubing mandrel is supported on the bearing, which bearing rests on the interior ledge of the mandrel bowl. The ledge of the tubing mandrel therefore engages and rotatably rides against the bearing. This arrangement allows the tubing to rotate by rotating the mandrel residing on the bearing disposed on the interior ledge of the mandrel bowl. The top of the tubing mandrel may be connected to a swivel, or be an integral part of the swivel, or connected to a union in such a manner to allow one to rotate the tubing by turning the mandrel and or rotating part of the swivel. Normally, one would use a handle or pipe wrench to manually turn the mandrel or swivel or union that extends above the wellhead or, a device known in the art may be applied to automatically turn the mandrel or swivel or union..

[0014] Seals are provided (but not necessary) to isolate the interior of the mandrel bowl from fluids from the well or outside the well, thereby preserving any lubrication of the bearings and minimizing corrosion or contamination inside the mandrel bowl area. Seals may also be placed on the outside of the mandrel bowl or bowl plate, or inside the casing head, in order to provide additional sealing of the fluids between the casing and tubing strings. A bowl plate is positioned on top of the mandrel bowl with seals preferred to allow sealing between the bowl plate and the mandrel bowl and also between the bowl plate and the tubing mandrel. This allows the tubing rotator assembly to be a self contained unit with connection ends above and below the mandrel bowl to allow connection to the tubing string below the mandrel bowl and connection to a swivel, union, or other material to allow fluids to exit the wellbore from the tubing.

[0015] FIG. 1 is a front view of a preferred embodiment of the present invention, a tubing saver rotator.

[0016] FIGS. 2-4 are front views of the tubing rotator saver of FIG. 1 without the standard equipment generally found on wellheads.

[0017] FIG. 5 illustrates a front view of an alternate embodiment of the present invention.

[0018] FIG. 6 illustrates a front view of a second alternate embodiment of the present invention.

[0019] FIGS. 1-4 illustrate a preferred embodiment of a tubing saver rotator assembly 100 made in accordance with the present invention. Generally, the present invention is an apparatus for attachment in an existing casing head or a casing head modified to accept a bowl or ledge assembly. This apparatus having a surface, such as a bearing in which a tubing mandrel rests and allows one to rotate the tubing above the wellhead. It provides a low profile reducing the distance between the casing head and the pumping tee, which may eliminate the need for one to raise the pumping unit to fit on the rotator. In addition, the conventional seals above the bowl assembly have less chance of leaking fluids located between the casing and tubing due to the seals potentially installed in the present invention. In addition, if the conventional seals do start to leak, one can change the sealing elements without having to remove the tubing rotator assembly 100 or tubing string (not shown) from the well. In the preferred embodiment, the present invention includes a pin end projecting upwardly from the mandrel or from the swivel joint. This allows a rig to pick up the mandrel and attach it to the pump tee above the wellhead and to the tubing string below the mandrel by simply screwing on two connections as will be further described. A conventional screwdriver or hex wrench will allow replacement of all the seals in the bowl and tubing mandrel assembly if replacement becomes necessary. If the fluids between the casing head and tubing string start to leak around the wellhead, sealing elements may be tightened to effect a good seal, or the seal elements may be replaced and tightened without removing the tubing rotator or tubing string with a rig. This provides ease and speed of repair by one person in lieu of a conventional rig job, which may help the environment and lower operating costs.

[0020] Referring to FIG. 1, the tubing saver rotator assembly 100 includes a mandrel bowl 1 having a ledge support 1A, said mandrel bowl 1 positioned on an interior lip 17A within a casing head 17. A tubing mandrel 2 having an extending mandrel ledge 10 is rotatably mounted to the mandrel bowl 1. In the preferred embodiment, said mandrel ledge 10 of the tubing mandrel 2 is substantially perpendicular to the length of the tubing mandrel 2 however, it is understood that the mandrel ledge 10 may be disposed at other angles in relationship to the tubing mandrel 2 and achieve the objectives described herein.

[0021] Said mandrel ledge 10 may be supported on the surface of the ledge support 1A of the mandrel bowl 1 or, as shown in the drawings, may be supported on a bearing 3, which bearing 3 rests on the ledge support 1A of the mandrel bowl 1. The mandrel ledge 10 and the ledge support 1A therefore captures the bearing 3 therebetween. The mandrel ledge 10 of the tubing mandrel 2 therefore engages and rotatably rides against the bearing 3. A bowl plate 4 is attached to the mandrel bowl 1 with bowl plate screws 5 selectively located around the bowl plate 4. A lower interior bowl seal 6, a bowl plate seal 7, and a mandrel plate seal 8 prevents fluid from contaminating said bearing 3.

[0022] The lower end of the tubing mandrel 2 is attached to the tubing string (not shown) with a lower connection 9, and the opposite end of the tubing mandrel 2 is attached to a swivel 12 with an upper connection 11. Said lower and upper connection means 9, 11, is known in the art. As shown in FIG. 1, the swivel 12 is attached to an upper end 2A of the tubing mandrel 2, which allows a lower part 12A of the swivel 12 to rotate with the tubing mandrel 2. An upper part 13 of the swivel 12 may be attached to a stationary pump tee (not shown). A swivel cap 14 connects the lower part 12A of the swivel 12 to the upper part 13 of the swivel 12, and seals 15, 16, and 21 are provided in the swivel 12 to prevent leakage or entry of fluids from the tubing mandrel 2 or environment. A union (not shown) could be used in lieu of the swivel 12 as well as substitution of other types of mechanisms known in the art to allow rotation or, the tubing mandrel 2 may be attached directly to the pump tee with the pump tee designed to allow some movement or rotation.

[0023] A rubber or packing element 18 is disposed on top of the bowl plate 4. A top plate 19 is then disposed on top of the rubber or packing element 18, said top plate 19 is compressed down to squeeze the rubber element 18 between the top plate 19 and the bowl plate 4 by a casing head dognut 20. The dognut 20 may be removed to grease the bearing 3 area if desired or to replace the top plate 19, rubber element 18, bowl plate 4, bowl plate screws 5, bowl plate seal 7, or mandrel plate seal 8. This arrangement allows most seals to be easily replaced by one person without removing the tubing mandrel 2 and mandrel bowl 1 which would normally require a rig in prior art designs. The dognut 20 may be tightened down from time to time if any wellbore fluids start to leak out of the casing head 17 or it may be tightened after replacing the rubber element 18. The seals 6, 7, and 8 reduce the chance that the rubber element 18 will leak and thereby provides extra sealing protection.

[0024] FIG. 2 illustrates the rotator assembly 100 shown in FIG. 1 without the standard equipment normally on certain wellheads. Thus a rig only needs to pick up the entire pre-assembled rotator assembly 100 and stab the bottom pin into the tubing string, lower the mandrel bowl 1 into the well with the rig, and then attach the swivel and/or pump tee (depending on if the rig desired to install the swivel separately or as one piece). The bowl 1 may then be packed off in the wellhead with the plates and rubber element that are standard equipment for that wellhead.

[0025] Various options may be chosen to enhance or reduce the cost of the rotator assembly 100. For example, the seals 6, 7, and 8 may be eliminated, however fluids may enter the bearing 3 area during installation or operation of the oil and gas well. Seals or packing could also be used between the mandrel bowl 1 and casing head 17 to provide extra backup seals or eliminate the need for the bowl plate seal 7. If care is taken during installation, the mandrel plate seal 8 may be eliminated if the rubber element 18 is providing a good seal. In addition, the mandrel plate seal 8 may be replaced with a seal between the outer diameter of the mandrel ledge 10 and the mandrel bowl 1, a seal between the tubing mandrel 2 and the inner diameter of the bowl plate 4, and/or a seal between the top plate 19 and the tubing mandrel 2. In addition, seals may be used between the bowl plate 4 and the casing head 17, or between the top plate 19 and the casing head 17, in order to provide additional backup seals, or to eliminate the rubber element 18.

[0026] FIG. 5 illustrates an alternate embodiment of a tubing saver rotator 200. The rotator assembly 200 includes a tubing mandrel 32 having an extending mandrel ledge 38. Said mandrel ledge 38 may be rotatably supported on a top surface 31A of a bottom plate 31 or, as shown in FIG. 6, may be supported on a bearing 33, which bearing 33 rests on the top surface 31A of the bottom plate 31. The mandrel ledge 38 and the bottom plate 31 therefore captures the bearing 33 therebetween. The mandrel ledge 38 of the tubing mandrel 32 therefore engages and rotatably rides against the bearing 33. As shown in FIG. 5, the bottom plate 31 disposed between an interior edge 50A of a casing head 50 and an exterior edge 32A of the tubing mandrel 32. The bottom plate 31 therefore supports the bearing 33. A mandrel plate 34 rests on top of the mandrel ledge 38 and is disposed between the interior edge 50A of the casing head 50 and the exterior edge 32A of the tubing mandrel 32. A lower interior bowl seal 36, exterior plate seal 35, and a mandrel plate seal 37 prevents fluid from contaminating said bearing 33.

[0027] The lower end of the tubing mandrel 32 is attached to the tubing string (not shown) with a lower connection 39, and the opposite end of the tubing mandrel 32 is attached to a swivel 43 with an upper connection 41. The lower and upper connection means 39, 41 are known in the art. The swivel 43 is attached to an upper end 32B of the tubing mandrel 32, which allows a lower part 42 of the swivel 43 to rotate with the tubing mandrel 32. An upper part 43A of the swivel 43 may be attached to a stationary pump tee (not shown). A swivel cap 44 connects the lower part 42 of the swivel 43 to the upper part 43A of the swivel 43, and seals 45, 46, and 51 are provided in the swivel 43 to prevent leakage or entry of fluids from the tubing mandrel 32 or environment. A union (not shown) may be used in lieu of the swivel 43 as well as substitution of other types of mechanisms to allow rotation or, the tubing mandrel 32 may be attached directly to the pump tee with the pump tee designed to allow some movement or rotation.

[0028] A rubber or packing element 47 is disposed on top of the mandrel plate 34. A top plate 48 is then disposed on the rubber or packing element 47, said top plate 48 is compressed down to squeeze the rubber element 47 between the top plate 48 and the mandrel plate 34 by a casing head dognut 49. The dognut 49 may be removed to grease the bearing 33 area if desired or to replace the top plate 48, rubber element 47, mandrel plate 34, or mandrel plate seal 37.

[0029] Other options exist to use existing casing heads or modify the casing head design as shown in FIG. 5 to accept the bottom plate 31 that provides the top surface 31A of the bottom plate 31 for the bearing 33 to be rotatably supported on, with seals 35 and 36 positioned around the bottom plate 31, if desired. Further, other options exist to connect the mandrel plate 34 to the bottom plate 31 such as using bolts, supports, or other connection means known in the art.

[0030] The mandrel plate 34 may include additional seals (not shown) on the internal and/or external diameter of the mandrel plate 34, if desired. It should be further understood that in shallow wells, the bearing 33 may not be necessary to turn the tubing mandrel 32 if a good surface is provided between the bottom plate 31 and the mandrel ledge 38.

[0031] The purpose of the present invention is to have the mandrel bowl 1 (FIG. 1) or bottom plate 31 (FIG. 5) for the support of the tubing mandrel rotatable on the bearing surface attached to the string of tubing in the well. A bearing may or may not be used between the mandrel ledge and the bowl ledge support or bottom plate. The bearing would preferably be a thrust bearing and could be of the cylindrical roller bearing, needle bearing, tapered roller bearing, spherical bearing, and/or ball bearings. Thrust washers or a good surface between the mandrel ledge and the bottom plate could be used if the thrust weight is low enough to allow rotation of the tubing mandrel.

[0032] Referring again to FIG. 1, in the preferred embodiment seals are positioned between the tubing mandrel 2 and the mandrel bowl 1, between the bowl plate 4 and the mandrel bowl 1, and between the bowl plate 4 and the mandrel ledge 10. Additional or alternate seals to prevent installation contamination or contamination from outside fluids if the rubber element 18 leaks, or contamination from inside fluids into the bearing 3 area or external of the casing head 17, may be placed between the tubing mandrel 2 and an interior 4A of the bowl plate 4, between the mandrel ledge 10 and the mandrel bowl 1, between the tubing mandrel 2 and the top plate 19, between the mandrel bowl 1 and an interior 17B of the casing head 17, between the interior 17B of the casing head 17 and the bowl plate 4, and/or between the interior 17B of the casing head 17 and the top plate 19. From the above description it should be understood the present invention may allow the use of no seals or the use of any combination of seals between any combination of the tubing mandrel 2, bowl plate 4, top plate 19, rubber element 18, dognut 20, mandrel bowl 1, support ledges, and the casing head interior 17B. Likewise, referring to the embodiment of FIG. 5, it should be understood the present invention may allow the use of no seals or the use of any combination of seals between any combination of the tubing mandrel 32, bowl plate 34, top plate 48, rubber element 47, dognut 49, bottom plate 31, support ledges, and the casing head interior.

[0033] Further purpose of this invention is to allow one to attach a swivel or union to the top of the tubing mandrel. Referring to FIG. 3, the swivel 12 may be attached to the upper end 2A of the tubing mandrel 2 or, as shown in FIG. 4, to allow for an integral part of the swivel 12 to be built as part of the tubing mandrel 2 (to reduce costs and also to reduce the clearance between the wellhead and pump tee). The swivel or union or the tubing mandrel may have edges placed on them to allow easier gripping of the tubing mandrel by a pipe wrench or a handle or automatic rotation device. In addition, one may place attachments to the rotator or swivel assembly to allow gearing or other means to rotate the tubing mandrel.

[0034] Referring now to FIG. 6, illustrating a second alternate embodiment of the present invention, a tubing saver rotator assembly 300 includes a mandrel bowl 110 having a ledge support 110 A, said mandrel bowl 110 positioned on a lip 117 of a flanged connection 120. Said flange connection 120 allows for connection to the wellhead with bolts (not shown) placed through bolt holes 120A and sealing provided by a conventional ring seal (not shown) seated in a ring grove 120B. An alternate arrangement is to integrally combine the mandrel bowl 110 and the flange connection 120.

[0035] A tubing mandrel 130 is stabbed into the mandrel bowl 110 and rests on the surface of the ledge support 110A of the mandrel bowl 110 or, as shown in FIG. 6, may be supported on a bearing 140, which bearing 140 rests on the ledge support 110A of the mandrel bowl 110. A bowl plate 145 is attached to the mandrel bowl 110 with bolt plate screws 115 selectively located around the bowl plate 145. Fluids are prevented from entering the bearing 140 area through a lower interior bowl seal 116, a bowl plate seal 118, and a mandrel plate seal 119. The lower end of the tubing mandrel 130 is attached to a tubing string (not shown) with a lower connection 125, and the opposite end of the tubing mandrel 130 is attached to a swivel 143 with an upper connection 126. Said swivel 143 attached to an upper end 132 of the tubing mandrel 130, and allows a lower part 133 of the swivel 143 to rotate with the tubing mandrel 130. An upper part 133A of the swivel 143 may be attached to a stationary pump tee (not shown). A union may be used in lieu of the swivel 143 as well as substitution of other types of mechanisms known in the art to allow rotation. Further, as known in the art, the tubing mandrel 130 may be attached directly to the pump tee.

[0036] A rubber or packing element 147 is disposed on top of the bowl plate 145. A top plate 148 is then disposed on top of the rubber or packing element 147, said top plate 148 is compressed down to squeeze the rubber element 147 between the top plate 148 and the bowl plate 145 by a casing head dognut 149. The casing head dognut 149 may be removed to grease the bearing 140 area if desired or to replace the top plate 148, rubber element 147, bowl plate 145, bowl plate screws 115, bowl plate seal 118, or mandrel plate seal 119. This arrangement allows most seals to be easily replaced by one person without removing the tubing mandrel 130 and mandrel bowl 110 which would normally require a rig in prior art designs. In the preferred embodiment, thread means 149A attaches the dognut 149 to the flange connection 120 as shown in FIG. 6, however other similar attaching means known in the art including flange means may be used. The seals 116, 118, and 119 reduce the chance that the rubber element 147 will leak and therefore provides extra sealing protection for emissions or entry of outside fluids into the wellhead.

[0037] Other enhancements or modifications to the flanged tubing saver rotator assembly 300 includes the addition of seals between any combination of the dognut 149, the flanged connection 120, the top plate 148, the tubing mandrel 130, the mandrel bowl 110, or the bowl plate 145. In addition, the flanged connection 120 and mandrel bowl 110 may be manufactured as one piece. In addition, the user may rely on the seals 116, 118, and 119 disposed around the mandrel bowl 110, in place of the dognut 149, top plate 148, and rubber element 147. One further example of modification to the tubing saver rotator assembly 300 as described above, is to have the flange connection 120 and the mandrel bowl 110 manufactured as one piece, and using seals 116, 118, and 119 to prevent emissions or fluid entry into the wellhead, with seals 118 and 119 being replaceable without requiring use of a rig.

[0038] Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of a presently preferred embodiment of this invention.

[0039] Thus the scope of the invention should be determined by the appended claims in the formal application and their legal equivalents, rather than by the examples given.