Rotatable tubing anchor

A rotatable tubing anchor for anchoring a tubing string to a casing in a well, wherein a lock pin extending radially inward from a cylindrical drag body interacts with a lazy T portion of a lock slot in a peripheral surface of a mandrel positioned in the cylindrical drag body limits vertical and rotational movement of the mandrel in relation to the cylindrical drag body in a manner that enables retaining, controlling, setting, and releasing anchor slips on the rotatable tubing anchor for lowering a tubing string equipped with the rotatable tubing anchor and a down hole pump into a well, anchoring the tubing string to casing in the well against upward tension on the tubing string while allowing rotation of the tubing string, and releasing the rotatable tubing anchor from the casing to enable pulling the tubing string, rotatable tubing anchor, and pump out of the well.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention is related to oil well production equipment and more particularly to tubing anchors in oil well production tubing strings.

2. State of the Prior Art

Typical oils wells have well casings comprising lengths of larger diameter pipes set and cemented into well bore holes extending downwardly from the surface of the ground into or through one or more subterranean, oil-bearing, geological formations called reservoirs. Conventional completions in such wells include perforating the casing with holes at depths in one or more of the reservoirs that allow the crude oil and other fluids in the reservoir or reservoirs to flow into the well casing. Some wells have enough natural pressure in the reservoir to force the crude oil and other fluids all the way through the well casing to the surface of the ground, where the crude oil can be collected and transported away from the well for further refinement and use. Other wells do not have enough natural reservoir pressure to force the crude oil all the way to the surface of the ground, so pumps have to be used to lift the crude oil in the casing out of the well. Raising and collecting the crude oil from the well is commonly known as producing the well, and equipment used in that process is commonly called production equipment. There are many different kinds of production pumps used in oil wells for pumping crude oil in well casings to the surface of the ground, one of the oldest and yet most common popular of which is the reciprocating piston-type pump, sometimes also called sucker rod pump, stroking pump, traveling piston pump, or barrel pump.

Reciprocating piston-type pumps typically have a down-hole pump assembly comprising a hollow cylinder barrel mounted on the down-hole end of a string of production tubing that extends downwardly from a hanger on the well surface, through the well casing, and into the crude oil in the well casing. A piston containing a traveling, one-way check valve is positioned the cylinder barrel in a slidable manner that allows the piston and the traveling one-way check valve to move reciprocally upwardly and downwardly in the cylinder barrel, and a standing, one-way check valve is mounted on the bottom of the cylinder barrel. A sucker rod extends downwardly from a polish rod near the surface of the ground, through the production tubing string, and into the cylinder barrel where it is attached to the piston. The polish rod extends slidably through a stuffing box to connect the sucker rod to a pump jack or other pump driver for repetitively pulling the sucker rod upwardly and letting it down to reciprocate the piston in the cylinder barrel upwardly and downwardly. The stuffing box creates a seal around the polish rod to seal the interior of the tubing from the exterior of the well. The standing one-way check valve allows fluid in the casing to flow into the cylinder barrel as the piston is pulled upwardly by the pump jack and sucker rod, and the traveling one-way check valve allows that fluid in the cylinder barrel to flow through the piston as the piston moves downwardly in the cylinder barrel. Continuous reciprocal motion of the piston in combination with the one-way flow of fluid through the standing and traveling check valves results in the fluid in the well being pumped from the casing upwardly through the production tubing string to the surface of the well.

As explained in U.S. Pat. Nos. 5,139,090 and 5,327,975 issued to J. Land, both of which are incorporated herein for all that they disclose, in wells equipped with reciprocating piston-type pumps, rotating the production tubing string with respect to the sucker rod in the tubing string while concurrently placing the production tubing string in tension reduces severity of wear in areas where the sucker rod tends to rub against the inside surface of the tubing string and overall increases the useful life of the tubing string. Both of the aforesaid U.S. Pat. Nos. 5,139,090 and 5,327,975 describe apparatus and methods for anchoring the tubing string at or near the bottom of the well adjacent to the cylinder barrel in a rotatable manner to accommodate such tensioning and rotation of the production tubing string. The tubing anchor catcher with rotatable mandrel is described in the U.S. Pat. No. 5,327,975 as an improvement over the tubing rotator with down hole swivel described in U.S. Pat. No. 5,139,090. However, it has been found that tubing anchor catchers with rotatable mandrels made as described in the U.S. Pat. No. 5,327,975 are not reliably easy to set and are even more difficult to release and retrieve from the well, which results in problems when the tubing string, down hole pump components, and other production equipment in the well have to be removed from the well. Too often, inability to release those tubing anchor catchers quickly and easily is frustrating and time-consuming, sometimes causing the operator to resort to the back-up system of pulling hard on the tubing string to shear the shear pins in the anchor to release the slips that anchor the device in the well casing. Unfortunately, however, some tubing strings are in severely worn or in weakened condition, and such extraordinary tension breaks and severs the tubing string before the shear pins of the anchor shear, thereby causing the operator have to perform extraordinary recovery procedures, including, for example, drilling and fishing the remaining tubing and the tubing anchor catcher out of the well. Such extraordinary procedures not only add to the recovery time and costs but also destroy the tubing anchor catchers so that they cannot be used again.

The foregoing examples of related art and limitations related therewith are intended to be illustrative, but not exclusive or exhaustive, of the subject matter. Other aspects and limitations of the related art will become apparent to those skilled in the art upon a reading of the specification and a study of the drawings.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT

An example rotatable tubing anchor10is shown inFIG. 1as a diagrammatic illustration of one example embodiment and implementation of the invention, but recognizing that the invention recited in the claims below can also be implemented in myriad other ways and in myriad other apparatus once the principles are understood from the description herein. The example rotatable tubing anchor embodiment10includes a rotatable mandrel20extending through a cylindrical drag body52, which is part of an anchor assembly54. The mandrel20has a lock slot30(best seen inFIG. 2) that is milled or otherwise formed in the peripheral surface of the rotatable mandrel20for limiting axial and rotational movement of the mandrel20in relation to the drag body52and other components of the anchor assembly54. Additional description of the operative component parts of the example rotatable tubing anchor10are described below, but initial focus in this description is directed to the configuration of the lock slot30in the mandrel20, because the functions of the mandrel20, anchor assembly54, and other operative components are best understood in relation to the lock slot30. Suffice it to say at this point that rotation of the mandrel20in relation to the drag body52is very limited or even prohibited when the inner end51of the lock pin50(FIGS. 1,5, and6), which extends radially inward from the cylindrical drag body52of an anchor assembly54(seeFIGS. 5 and 6), is positioned in the lock slot30(FIG. 2), as will be explained in more detail below. Some limited vertical movement of the mandrel20along the longitudinal axis12is allowed by the lock pin50while the drag body52is stationary in the well casing50, as will be explained below, and the mandrel20is fully rotational 360 degrees in relation to the drag body52when the circumferential groove22around the peripheral surface of the mandrel20(FIG. 2) is aligned with the inner end51of the lock pin50.

Therefore, with reference now primarily toFIG. 2, the lock slot30in the mandrel20includes a vertical entrance portion32that extends vertically from the circumferential groove22substantially parallel to the longitudinal axis12of the mandrel20. The lock slot30also has a “lazy T” portion34, i.e., a portion34of the lock slot30that resembles a letter T lying on its side similar to a “lazy T” livestock brand. Therefore, that portion34of the lock slot30with the shape that resembles a lazy T livestock brand is sometimes referred to in this description as the lazy T portion34. The horizontal stem35of the lazy T in the lazy T portion34extends from the vertical entrance portion32to the cross-bar36of the lazy T in the lazy T portion34. Therefore, the cross-bar36of the lazy T portion34is also oriented vertically and substantially parallel to the longitudinal axis12. The upper extremity or edge37of the cross-bar36aligns with, and bears on, the lock pin50(FIGS. 1,3,5, and6) when the tubing string T, the rotating tubing anchor10, and the pump P are being lowered into the well casing C, as will be explained in more detail below. The lower extremity or edge38of the cross-bar36aligns with, and bears on, the lock pin50when the tubing string T, the rotatable tubing anchor10, and the pump P are being pulled out of the well, as will also be explained in more detail below.

Referring now primarily toFIGS. 1 and 7together, the example rotatable tubing anchor10is typically mounted near the bottom of a production tubing string T, just above a down-hole pump, such as the reciprocating piston-type pump P depicted diagrammatically inFIG. 7. As illustrated, for example, inFIG. 7, the tubing string T, the example rotatable tubing anchor10, and the down-hole pump P are positioned in the casing C of a well that is drilled into a geological formation G that bears oil, gas, water, or other fluid that is to be produced to the surface of the ground. Reciprocating piston-type pumps are typically mounted in a section of tubing at or near the bottom end of the production tubing string T. Accordingly, the pump P is shown inFIG. 7mounted in a bottom tubing section. The example rotatable tubing anchor10is shown inFIG. 7as connected between the bottom tubing section B and the rest of the tubing string T, although it could be in a different position, and other production equipment or appurtenances could also be included. Perforation holes H, which extend through the casing C and into the formation G, allow oil and other fluids F to flow from the formation F into the casing C. The production tubing string T is made long enough to position the pump P in the fluid F in the casing C. A sucker rod R extends downwardly from a polish rod (not shown) near the surface of the ground G, through the production tubing string T, to the pump P, where it is attached to a piston (not shown) in the pump P. The sucker rod R is reciprocated up and down, as indicated by arrow A, by a pump actuator (not shown) on the surface of the ground G to reciprocate the piston in the down hole pump P. The reciprocating piston in combination with standing and traveling check valves (not shown) in the pump P, pumps the fluid F through the production tubing T to the surface of the ground G.

The rotatable tubing anchor10is used to anchor the lower end of the production tubing string T to a particular location in the casing C. After the rotatable tubing anchor is set in immovable relation to the casing C, the production tubing string T is pulled upwardly against the rotatable tubing anchor10to place the tubing string T in tension, and the upper end of the tubing string T is then fastened at the well head (not shown) in such tension. A rotation drive mechanism (not shown) connected to the tubing string T at the well head slowly rotates the production tubing string T as the well is pumped. Such rotation of the tubing string T while the well is pumped extends the useful life of the tubing string T by eliminating spot wear in particular tubing sections that may be caused by the sucker rod R rubbing on localized spots on the inside surface of the production tubing string T, for example, where there is a bend or deviation in the tubing string T. The rotation of the tubing string T spreads such wear over larger areas around the inside surface of the tubing string T instead of allowing all of the wear to be concentrated in one spot. The rotating tubing anchor10accommodates such rotation of the tubing string T while anchoring the lower end of the tubing string T to the casing C in a manner that resists the upward pull on the production tubing string T, thereby holding the production tubing string T in tension as described above, which also reduces wear by minimizing bends and deviations where such rubbing of the sucker rod R on the tubing string T tends to occur.

Referring again toFIGS. 1,5, and6, the anchor assembly54of the rotatable tubing anchor10comprises the cylindrical drag body52through which the mandrel20extends, an upper slip assembly56, and a lower slip assembly58. The lower slip assembly58comprises a plurality of lower slips62mounted in the drag body52, and the upper slip assembly56comprises a plurality of upper slips60mounted in a cylindrical slip cage64, which is attached to, and extends upwardly from, the drag body52. The lower slips62anchor the rotatable tubing anchor10to the inside surface of the casing C when the lower slips62are set, as will be described in more detail below. However, persons skilled in the art are familiar with the structures and functions of slips in oil well equipment and probably do not need further explanations of slips or of the operation of slips. Also, persons skilled in the art will recognize that slips can be provided with other components, structures and assemblies for use in this invention once they understand the principles of the invention.

Essentially, in the example rotatable tubing anchor10, a lower cone27mounted on the mandrel20adjacent to the lower end28of the mandrel20is sized and shaped to wedge under the lower slips62between the slips62and the mandrel20when the mandrel20is pulled upwardly in relation to the drag body52, as best seen inFIGS. 10 and 11, which will be described in more detail below. Such wedging of the lower cone27on the lower slips62forces the lower slips62radially outward into engagement with the inside surface of the casing C, as illustrated inFIGS. 6,10, and11. When the lower slips62are engaged with the inside surface of the casing C in this manner, the anchor assembly54can resist a large, upwardly directed, pulling force on the production tubing string T and mandrel20, thus effectively anchoring the lower end of the production tubing string T in that position. To release the rotatable tubing anchor10from such anchored engagement with the casing C, therefore, the mandrel20with the lower cone27have to be moved downward in relation to the lower slips62and cylindrical drag body54so that the lower slips62can move radially inward to disengage from the inside surface of the casing C.

The upper slips60anchor the rotatable tubing anchor10to the inside surface of the casing C when the upper slips60are set. Setting the upper slips60is accomplished in a similar manner to setting the lower slips62, but opposite in direction. Essentially, the upper slips60can be set into engagement with the inside surface of the casing C to anchor the rotatable tubing anchor10in a fixed position in the casing C by moving the production tubing string T and mandrel20downwardly far enough in relation to the drag body52and slip cage64to force the upper cone25on the upper coupler24to wedge between the upper slips60and the mandrel20, thereby forcing the upper slips60radially outward into engagement with the inside surface of the casing C, as best seen inFIGS. 14 and 15. When the upper slips60are set into engagement with the casing C in that manner, the rotatable tubing anchor10can resist a large, downwardly directed, force on the mandrel20, thereby anchoring the rotatable tubing anchor10and production tubing string T from moving farther down the well. To release the upper slip assembly56, the production tubing string T and mandrel20with the upper cone25have to be moved upwardly in relation to the upper slip assembly56to allow the upper slips60to move radially inward, away from the inside surface of the casing C, as illustrated inFIGS. 8 and 9.

While the slips60or62are capable of anchoring the tubing string T very securely to the casing C when set, as explained above, it is important to prevent both the upper slips60and lower slips62from engaging the casing C as the production tubing string T, rotatable tubing anchor10, and pump P are being lowered into the well as well as when they are being pulled back out of the well. The lock slot30shown inFIG. 2, interacting with the lock pin50shown inFIGS. 1,3,5, and6, not only provides the function of preventing the upper slips60and lower slips62from being set while lowering the tubing string T, rotatable tubing anchor, and pump P into the well and while pulling them out of the well, but also enables the mandrel20to be manipulated into a position in relation to the drag body52in which the mandrel20is freely rotatable in relation to the drag body52when the lower slips62are set in anchored relation to the casing C.

For lowering the tubing string T, rotatable tubing anchor10, and pump P into the well, the relative positions of the mandrel20, including the lock slot30, in relation to the drag body52, including the lock pin50, and in relation to the slips60,62are best seen inFIGS. 8 and 9, keeping in mind the configuration of the lock slot30best seen inFIG. 2and the radially inner end51of the lock pin50best seen inFIGS. 5 and 6. InFIGS. 8 and 9, the example rotatable tubing anchor10is illustrated diagrammatically with a portion of cylindrical drag body52surrounding the lock pin50cut away to reveal the relevant portions of the lock slot30in the mandrel30in relation to the lock pin50. The lock pin50inFIGS. 8 and 9is shown with cross-hatching as the hexagonal head and radially outer portions of lock pin50are cut away along with the surrounding portion of the drag body52, thus leaving the radially inner portion of the lock pin50in its proper position in relation to the rest of the drag body52that is still visible in the view ofFIGS. 8 and 9. In this manner, the manipulations and relative positions of the mandrel20with its lock slot30in relation to the drag body52with its lock pin50can be visualized along with this description.

The mandrel20is of such a length, and the upper and lower cones25,27are at such a distance apart from each other, that when the mandrel20is positioned in the cylindrical drag body52in such a manner that the lock pin50extends into any position in the lazy T portion34of the lock slot30, neither one of the upper and lower cones25,27, respectively, are wedged into the respective upper and lower wedge assemblies56,58. Therefore, positioning the mandrel20in the cylindrical drag body52where the lock pin50extends into the lazy T slot portion34of the lock slot30keeps both the upper slip assembly56and the lower slip assembly58disengaged from the casing C, as illustrated, for example, inFIGS. 8 and 9. With both the upper slips60and the lower slips62disengaged from the casing C, the production tubing string T with the rotatable tubing anchor10and down hole pump P can be lowered into, or pulled out of, the well.

Drag pads66are mounted in the drag body52with a spring bias that forces the drag pads66radially outward from the drag body52into frictional engagement with the inside surface of the casing C in a manner known and understood by persons skilled in the art. The friction between the drag pads66and the casing C resists any longitudinal or rotational movement of the drag body52in relation to the casing C. Therefore, in order to move the drag body52up, down, clockwise, or counterclockwise in the casing C, enough force has to be applied to the drag body52by the tubing string T via the mandrel20and lock pin50to overcome the friction. Any convenient number of drag pads66can be used. The example rotatable tubing anchor10is shown with four drag pads66.

As explained above, when the mandrel20is positioned in relation to the drag body52in such a manner that the lock pin50is anywhere in the lazy T portion34of the lock slot30, none of the slips60,62are set, so the only significant resistance to movement of the rotatable tubing anchor10upwardly or downwardly in the casing C is the friction between the drag pads66and the casing wall C. For lowering the tubing string T with the rotatable tubing anchor10and pump P into the well, the mandrel20is manipulated in relation to the drag body52in such a manner as to get the cross-bar36of the lazy T portion34of the lock slot30aligned with the lock pin50. Then, as the tubing string T, rotatable tubing anchor10, and pump P are lowered into the well, the friction between the drag pads66and the inside surface of the casing C resists the downward movement of the drag body52in the casing C, which causes the mandrel20to move longitudinally downward in relation to the drag body52until the upper edge37of the lazy T portion34of the lock slot30contacts and bears against the lock pin50as illustrated inFIGS. 8 and 9. The weight or lowering force of the tubing string T applied on the mandrel20is then transferred via the lock pin50to the drag body52to overcome the friction between the drag pads66and the casing C and thereby push the rotatable anchor body10down the well in spite of the drag pads66dragging on the inside surface of the casing C. The position of the lock pin50illustrated inFIGS. 8 and 9against the upper edge37and also confined laterally by the adjacent lateral edges40,41of the lazy T cross-bar36(seeFIG. 9) prevent the mandrel20from rotating in relation to the drag body52so that the lock pin50cannot escape from the lazy T portion34of lock slot30as the rotatable tubing anchor10with the pump P are being pushed down the well by the production tubing string T.

Generally, the rotatable tubing anchor10with the pump P are pushed by the production tubing string T downwardly in the well casing C to a desired position where the pump P is immersed in the fluid F in the casing C as illustrated, for example, inFIG. 7. At the desired depth, the lower slips62are set against the inside surface of the casing C to anchor the production tubing string T at or near its lower end to the casing C in a manner that provides a strong resistance to an upward force. Therefore, when a strong upward force is pulled on the production tubing string T from the well head (not shown) at the surface of the ground, the anchored rotatable tubing anchor10strongly resists such upward force and prevents the portion of the string T that is attached to the mandrel20from moving in relation to the casing C. Consequently, when the lower slips62are set to anchor the rotatable tubing anchor10to the desired position in the casing C, an upward force pulled on the tubing string T from the surface of the ground will place the tubing string T in tension and thereby keep the lower slips62set by preventing lowering of the mandrel20and disengagement of the lower cone27from wedging the lower slips62into the casing C. As also explained above, applying such an upward force on the tubing string T at the well head at the surface of the ground to place the tubing string T intension also tends to keep the tubing string T as straight as possible and to minimize lateral movement of sections of the tubing string T in response to pumping fluid pressure pulses and mechanical forces and thereby minimizes wear from the reciprocal movement of the sucker rod R in the tubing string T. In order to set the lower slips62to anchor the rotatable tubing anchor10to the casing, the mandrel20has to be manipulated to disengage the lock pin50from the lazy T portion54of the lock slot30so that the mandrel20can be pulled upwardly in relation to the drag body52far enough to engage and wedge the lower cone27against the lower slips62, as best seen inFIGS. 10 and 11.

As explained above and shown inFIGS. 8 and 9, for lowering the production tubing string T with the rotatable tubing anchor10and pump P down the casing C, the mandrel20is positioned in relation to the drag body52in such a manner that downward movement of the mandrel20in relation to the drag body52is prohibited by the upper edge37bearing on the lock pin50, and rotation of the mandrel20in relation to the drag body52is prohibited by the upper lateral edges40,41on either side of the lock pin50. Further, the length of the cross-bar36of the lazy T portion34of the lock slot30does not allow enough upward movement of the mandrel in relation to the drag body52to set the lower slips62to anchor the rotatable tubing anchor10against the upward tension required for the tubing string T. Therefore, in order to set the slips62against the casing C to anchor the production tubing string T, the mandrel20has to be manipulated in relation to the drag body52in a manner that is effective to disengage the mandrel20from the drag body52and lock pin50, as best explained with reference toFIGS. 10 and 11, keeping in mind the configuration of the lock slot30as best seen inFIG. 2. For this explanation, it is also helpful to keep in mind that the drag pads66on the drag body52pressing by spring force against the casing C create enough friction to keep the drag body52with the lock pin50as well as the slips60,62and other components of the anchor assembly54stationary in relation to the casing C while the mandrel20moves up and down and rotates, as long as the mandrel20does not engage the lock pin50. Therefore, as long as the mandrel20does not engage the lock pin50, the mandrel20with its lock slot30can be moved up, down, and rotationally by manipulating the production tubing string T up, down, and rotationally while the drag body52, lock pin50, and slips60,62of the anchor assembly54remain stationary. The goal of the maneuver required to set the lower slips62is to get the mandrel20with its lock slot30disengaged from the lock pin50so that the mandrel20can be pulled upwardly by the tubing string T enough to wedge the lower cone27into the lower slips62. Also, the mandrel20has a circumferential groove22extending round its peripheral surface with a connection to the lock slot30(seeFIG. 2) at the entrance portion32of the lock slot30. The spacing of the circumferential groove22in relation to the lower cone27is such that the circumferential groove22aligns with the lock pin50when the mandrel20is positioned with the lower cone27wedged into the lower slips62, as illustrated inFIGS. 10 and 11. Consequently, the mandrel20rotatable, 360 degrees and more in relation to the stationary drag body52without constraint by or engagement with the lock pin50when the mandrel20is in the longitudinal position to engage and set the lower slips62. Therefore, the mandrel20can rotate freely about the longitudinal axis12in relation to the drag body52and lock pin50when the lower slips62are set to anchor the rotatable tubing anchor10and lower end of the tubing string T to the casing C.

To maneuver the mandrel20from the position for lowering the tubing string T, the rotatable tubing anchor10, and the pump P into the well, as shown inFIGS. 8 and 9, to the anchor position shown inFIGS. 10 and 11, the mandrel20has to be pulled upwardly by the production tubing string T enough to move the upper edge37of the lazy T portion34of the lock slot30upwardly and away from the stationary lock pin50, and then the mandrel20has to be rotated by the tubing string T to the right (i.e., counterclockwise16as shown inFIG. 2) in order to move the vertical entrance portion32of the lock slot30to the right into alignment with the stationary lock pin50. Then, with the vertical entrance portion32of the lock slot30aligned with the stationary lock pin50, the mandrel20has to be pulled by the tubing string T upwardly again to wedge the lower cone27into the lower slips62hard enough to force the lower slips62radially outward into anchored engagement with the inside surface of the casing C, as shown inFIGS. 10 and 11.

As mentioned above, when the mandrel20is positioned for the lower cone27to set the lower slips62into anchoring engagement with the casing C as shown inFIGS. 10 and 11, the circumferential groove22in the mandrel20aligns with the stationary lock pin50, which enables the mandrel20to rotate freely 360 degrees in relation to the lock pin50, drag body52, slips62, and other components of the anchor assembly54. Such capability of the mandrel20to rotate 360 degrees (and continuously more than 360 degrees during production operations) in relation to the anchor assembly54is necessary to accommodate the rotational movement of the tubing string T during production operations, as explained above. However, to further enable and accommodate such free rotation of the mandrel20in relation to the drag body52and other components of the anchor assembly54, the lower cone27is mounted in a rotatable manner on the mandrel20with a thrust bearing70(best seen inFIG. 5) between the lower cone body27and a shoulder or ring72, which is part of, or attached to, the mandrel20. Therefore, the upward force applied by the mandrel20to the lower cone27is born by the thrust bearing70in a near frictionless manner that allows the mandrel20to rotate in relation to the lower cone27as the lower cone27is wedged tightly against the lower slips62and remains stationary in relation to the lower slips62and other components of the anchor assembly54.

For pulling the example rotatable tubing anchor10and pump P out of the well, the mandrel20has to be maneuvered to release the lower slips62from casing C and then positioned as shown inFIGS. 12 and 13in which the lower edge38of the lazy T cross-bar36abuts the lock pin50. With the lower slips62released and the mandrel20in that position, an upward force applied by the tubing string T to the mandrel20can pull the rotatable tubing anchor10along with the pump P out of the well. The upward force on the mandrel20is transferred by the lower edge38of the lazy T portion34of the lock slot30to the lock pin50and thereby to the drag body52. When sufficient upward force is applied to the mandrel20and drag body52to overcome the friction between the drag pads66and the casing C, the rotatable tubing anchor10and the pump P can be pulled upwardly through the casing C to the surface of the ground G.

To release the lower slips62and move the mandrel20from the anchored position shown inFIGS. 10 and 11to the pull-out position shown inFIGS. 12 and 13, the tubing string T is used to apply a downward force on the mandrel20to push the lower cone27away from the lower slips62, thereby releasing the lower slips62from the casing C. The tubing string T is also rotated to rotate the mandrel20to align the entrance portion32of the lock slot30with the stationary lock pin50, and then lowered farther to move the entrance portion32downward and around the lock pin50until the stem35of the lazy T portion34of the lock slot30aligns with the lock pin50. The approaches to the entrance portion32of the lock slot30from the circumferential groove22can be tapered, as illustrated for example at the diagonal edges44,45at the intersection of the circumferential groove22with the entrance portion32, to facilitate aligning the entrance portion32with the lock pin50and capturing the lock pin50into the lock slot30. With the stem35aligned with the lock pin50, the tubing string T is then used to rotate the mandrel20to the left (i.e., clockwise17as shown inFIG. 2) until the cross-bar36of the lazy T portion54of the lock slot30aligns with the lock pin50. Finally, with the cross-bar36aligned with the lock pin50, the tubing string T can be pulled upwardly, which pulls the mandrel20upwardly in relation to the lock pin50and drag body52until the bottom edge38of the lazy T portion34of the lock slot30abuts the lock pin50, at which point the upward force applied on the mandrel20by the tubing string T is transferred to the drag body52via the lock pin50, and the entire assembly of the tubing string T, rotatable tubing anchor10, and pump P can be pulled out of the well.

In the example rotatable tubing anchor10shown inFIG. 5, the ring72is a shear ring, which is attached to the mandrel20with a plurality of shear pins74. The shear pins74extend through the shear ring72and into the groove76in the mandrel20(FIGS. 2 and 5). While this shear ring72feature is not essential, it does provide an alternate way of releasing the lower slips62, if necessary, in the event an operator is unable to release the lower slips62by the manipulations described above. A large enough upward force pulled by the tubing string T on the mandrel20with the lower slips62still set and anchored to the casing C will shear the shear pins74, thereby releasing the mandrel20from the shear ring72and from the lower cone27. With the shear pins74sheared and the shear ring72free to slide on the mandrel20, the lower cone27can drop by gravity away from the lower slips62and thereby release the lower slips62from the casing C to disengage the rotatable anchor device10from the casing C. The tubing string T, rotatable anchor device10, and pump P can then be pulled out of the well.

In some circumstances, an operator may find that one or more sections of tubing in the tubing string T are so badly worn or otherwise deteriorated that the tubing string T breaks between the surface of the ground and the rotatable tubing anchor10so that the remaining portion of the tubing string T under the break is no longer in tension. Instead, the weight of that remaining portion of the tubing string T under the break pushes the mandrel20with the lower cone27down in relation to the drag body52and releases the lower slips62from the casing C. In that situation, the entire rotatable tubing anchor10, the remaining portion of the tubing string T under the break, and the pump P would fall to the bottom of the well. The upper slips60and upper cone25are optional, but they can be provided to prevent or arrest such a fall, as illustrated inFIGS. 14 and 15. If the tubing string T breaks as described above, the weight of the remaining portion of the tubing string T under the break pushes the mandrel20downward enough in relation to the drag body52and slip cage64to force the upper cone25to wedge against the upper slips60, as illustrated inFIGS. 14 and 15, and thereby drive the upper slips60radially outward into anchoring engagement with the inside surface of the casing C. Such engagement of the upper slips60with the casing C prevents the rotatable tubing anchor10, tubing string T, and pump P from falling farther down the well, which makes it easier to recover them from the well with conventional “fishing” tools and techniques.

In order for the mandrel20to move downward in relation to the drag body52enough to set the upper slips60, the downward motion of the mandrel20in relation to the drag body52has to be able to capture the lock pin50in the upper extremity33of the entrance portion32as shown inFIGS. 14 and 15. Therefore, the mandrel20has to be rotated to position in relation to the drag body52in which the entrance portion32aligns with the lock pin50. Since the tubing string T in the circumstance described is broken between ground and the rotatable tubing anchor10as explained above, the mandrel20cannot be rotated by manipulation of the tubing string T. To mitigate this problem, the mandrel20can be made self-aligning by providing the circumferential groove22with an upper edge46that curves or slants upwardly toward the entrance portion32of the lock slot30to act as a cam surface to cam the mandrel20into such alignment. The upper edge46can be curved to provide such a slant as shown, for example, inFIGS. 2,8,12, and13, or the slant can be provided by a straight upper edge slanted toward the entrance portion32. If two lock slots30are used as mentioned above, the upper edge46can be slanted toward the respective entrance portions32of both lock slots30. Therefore, with the weight of the tubing string T pushing down on the mandrel20and the upper edge46bearing on the lock pin50, the upper edge46cams the mandrel20to rotate until the entrance portion32moves into alignment with the lock pin50, whereupon the mandrel20drops farther to set the upper slips60as described above. With the upper slips60set in that manner, the rotatable tubing anchor10will remain anchored to the casing C as long as the upper cone25is wedged against the upper slips60. Then, if the portion of the broken tubing string T that is still connected to the mandrel20is captured, for example, with a “fishing tool”, then an upward pull on that portion of the tubing string or on the coupler24will pull the upper cone25away from the upper slips60, thereby releasing the rotatable tubing anchor10to be pulled out of the well with the pump P.

Although the description above is provided with reference to oil wells, this invention is applicable to any type of well in which reciprocating piston pumps are used to pump a fluid through a production tubing string, including, but not limited to water wells. Also, while the lazy T portion34of the lock slot30in the mandrel20is shown and described as extending to the right of the entrance portion32, the lazy T portion34could extend to the left of the entrance port32as would be understood by person skilled in the art once they understand the principles of the operations and functions described above. The drag body52and slip cage64are shown and described as two components, although they could be one component or any other structure that provides the functions described above.

The foregoing description provides examples that illustrate the principles of the invention, which is defined by the claims that follow. Since numerous insignificant modifications and changes will readily occur to those skilled in the art once they understand the invention, it is not desired to limit the invention to the exact example constructions and processes shown and described above. Accordingly, resort may be made to all suitable combinations, subcombinations, modifications, uses, and equivalents that fall within the scope of the invention as defined by the claims. The words “comprise,” “comprises,” “comprising,” “composed,” “composes,” “composing,” “include,” “including,” and “includes” when used in this specification, including the claims, are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, or groups thereof.