Progressive Cavity Pump Rod Guide

Abstract

A rod guide receiver is molded directly onto the sucker rod and a rod guide or spinner is then molded directly onto the rod guide receiver, the spinner having a plurality of blades or fins molded as an integral part of a spinner body that is free to turn about the rod guide receiver. The rod guide receiver serves in the manner of a bearing race, having a pair of opposing stops to retain the spinner subsequently molded thereon. The spinner may also be referred to herein as a centralizing sleeve. The rod guide receiver and the spinner are both formed of polymeric materials, but of materials different from one another so that the rod guide is free to rotate about the rod guide receiver. Further, the vanes of the rod guide are formed in a zig-zag pattern to enhance the strength and effectiveness of the vanes in bearing against the inside surface of the well tubing.

Description

FIELD OF THE INVENTION

The present invention relates to the field of rod guides suitable for guiding a sucker rod within production tubing of an oil or gas well. More particularly, the invention relates to a rod guide assembly for guiding a rotary sucker rod which powers a progressive cavity pump in a well.

BACKGROUND OF THE INVENTION

In the oil and gas industry, primary and secondary recovery operations frequently use a rotating sucker rod string to operate a downhole rotary pump such as a progressive cavity pump. A progressive cavity pump is also used to pump water from a gas well, and for other operations. These pumps are often used because of their ability to pump viscous fluids and fluids containing significant amounts of solids. The sucker rod string is positioned within well tubing of circular cross section and the rod string is rotated by a mechanism at the well head. By this operation, crude oil is pumped to the surface and recovered.

During these types of operation, the sucker rod string warps so that portions of the rotating string rub against the well tubing. Typically, string deformation causes rubbing action at a localized area of the tubing rather than the entire inner circumference. This leads to local wear of the tubing and rod and is generally undesirable. Such rubbing may be due to a crooked tubing or to deliberate bends in the tubing.

To alleviate this wearing problem, rod guides have been positioned on the string at spaced-apart intervals along the string. These types of rod guides commonly comprise a circular center through which the string passes and a vaned outer body having a maximum diameter greater than that of the rod but smaller than the inside diameter of the tubing within which it is located. The outer diametric cross section defines arc portions which lie on a common circle centered on a central axis of the hollow center. The function of the rod guide is to contact the tubing to prevent direct contact between the string and tubing. As the rod guide contacts the tubing, the guide rotates with the string and thus rubs against the stationary tubing. The rubbing of the rotating rod against the stationary tubing damages the tubing, thereby reducing its life.

Various types of rod guides have been devised for guiding a sucker rod within production tubing. A rod guide that is capable of rotation with respect to the rod, and which does not rotate with the rod when the rod guide is in contact with the well tubing, has been shown to reduce tubing wear and thereby extend tubing lifetime. Many rod guides are intended for use with a reciprocating sucker rod, and other rod guides are primarily intended for use with a rotating sucker rod. Some guides have utility for either a reciprocating rod or a rotating rod, although design considerations generally dictate that a sucker rod guide be primarily intended for one application or the other, but not both.

As previously alluded to, compared to commonly used beam pumps which are powered by a reciprocating sucker rod, progressive cavity (PC) pumps are generally able to deal with a high concentration of sand or other particulate in the recovered fluid. In order to reduce friction wear between the vanes of the rod guide and the inside surface of the well bore tubing, such types of rod guides typically rotate relative to the sucker rod. To mount the rod guide to the sucker rod, the body of the guide commonly includes a gap or an opening into which the sucker rod is inserted. This action of mounting the rod guide weakens the body of the guide, and presents a region of the rod guide which can trap cuttings and other solids, which ultimately degrades the performance of the pump system as a whole and reduces the expected lifetime of the rod guide.

The disadvantages of the prior art are overcome by the present invention, and an improved rod guide particularly suited for a progressive cavity pump is hereinafter disclosed.

SUMMARY OF THE INVENTION

The present invention comprises a rod guide receiver molded directly onto the sucker rod and a rod guide molded directly onto the rod guide receiver, the rod guide having a plurality of blades or fins molded as an integral part of a guide body that is free to turn about the rod guide receiver. The rod guide receiver serves in the manner of a bearing race, having a pair of opposing stops to retain the guide subsequently molded thereon. The rod guide may also be referred to herein as a spinner or a centralizing sleeve. The rod guide receiver and the rod guide are both formed of polymeric materials, but of materials different from one another so that the rod guide is free to rotate about the rod guide receiver. Further, the vanes of the rod guide are formed in a zig-zag pattern to enhance the strength and effectiveness of the vanes in bearing against the inside surface of the well tubing.

These and other features of the present invention will be readily apparent to those of skill in the art when they study the following detailed description in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, more particular description of the invention, briefly summarized above, may be had by reference to embodiments thereof which are illustrated in the appended drawings.

FIG. 1 is a side view of a portion of well tubing in section with a portion of sucker rod with a rod guide receiver and rod guide spinner of the present invention.

FIG. 2 is a side section view of a rod guide receiver and rod guide spinner of the present invention.

FIG. 3 is section view of the combination receiver and rod guide spinner, taken along section lines 3-3 of FIG. 2.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates a presently preferred embodiment of a rod guide receiver and rod guide spinner combination of the present invention. Well tubing 10 extends from a wellhead (not shown) down to a region below a progressive cavity pump 12. From the wellhead to the pump 12 may be many thousands of feet, and a sucker rod 14 extends this entire distance. Typically, the sucker rod 14 is made up of standard length segments and these segments are coupled together to form the desired total length.

A plurality of rod guide assemblies are mounted to the sucker rod 14 at spaced apart intervals. One such rod guide assembly 16 is illustrated in FIG. 1 for descriptive purposes. The sucker rod 14 and the rod guide assembly 16 both typically come in a variety of sizes and diameters to accommodate different operating conditions. The rod guide assembly 16 is arranged to fit within an inside diameter 18 of the well tubing 10. The progressive cavity pump 12 is coupled to the bottom end of the sucker rod 14 and is rotated by the sucker rod.

FIGS. 2 and 3 show more details of the rotating rod guide of the present invention. The rod guide assembly 16 comprises two parts. First, a rod guide receiver 22 is molded onto the sucker rod 14. The receiver 22 is preferably formed of a fiberglass reinforced polyphenylene sulfide compound, such as for example RYTON™ (PPS or R) or a synthetic molding resin containing polymers and copolymers of polyamides and their derivatives such as for example AMODEL® (PPAU or AF), that provides outstanding chemical resistance and mechanical properties even at elevated temperatures. RYTON™ is a trademark of Chevron Phillips Chemical Company and AMODEL® is a registered trademark of Solvay Advanced Polymers, L.L.C. The receiver 22 includes an upper stop 24, a lower stop 26, and cylindrical body 28 joining the upper and lower stops. The upper and lower stops are tapered at either end away from the cylindrical body to streamline the flow of fluids by the rod guide assembly.

Second, once the receiver is molded onto the sucker rod and cured, a spinner 30 is molded onto the receiver 22. The spinner 30 is preferably formed of AMODEL® (PPAU or AF) that is non-glass filled. Non-glass PPAU material is known in the industry but is typically used in plastic coated tubing applications. The dissimilarity of the materials of the receiver 22 and the spinner 30 allows the spinner 30 to rotate freely around the receiver against the cylindrical body 28. Also, once the spinner has been molded onto the receiver 22, a razor sharp blade is used to cut the length of the spinner before it is cooled. This step in the manufacturing process distracts the memory of the spinner material long enough that it cannot continue to cool and shrink, thereby binding on the receiver.

As shown in FIG. 3, although the rod guide spinner 30 is molded directly onto the cylindrical body 28 of the receiver 22, the manufacturing process results in a gap 32 between the rod guide spinner 30 and the cylindrical body. This allows the spinner to turn freely relative to the receiver. Also note that the spinner preferably comprises four vanes 34, although three vanes may be used, if desired. Four vanes provides superior centering capability for the assembly, but this also reduces the area available for fluid flow between the assembly 16 and the inside diameter 18 of the well tubing. This drawback may be somewhat alleviated by making the vanes 34 narrower but this in turn reduces the mechanical strength of the vanes to shear stress as the sucker rod rotates.

This problem is overcome by forming the vanes in a zigzag pattern along a line parallel to the axis of the sucker rod. Once such vane 34′ is illustrated in FIG. 1. By molding at least two bends 36 into each vane, the vane is made more resistant to shear stress, much as a peaked roof can hold a greater load than a flat roof.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. This invention is not to be construed as limited to the particular forms disclosed, since these are regarded as illustrative rather than restrictive. Moreover, variations and changes may be made by those skilled in the art without departing from the spirit of the invention.

Claims

1. A rod guide assembly on a sucker rod having an axis, the assembly comprising:

a. a rod guide receiver molded to the sucker rod along an axis, the receiver having an upper stop and a lower stop and a cylindrical body joining the upper and lower stops; and

b. a rod guide spinner molded onto the rod guide receiver, the receiver and spinner defining a gap therebetween, and the spinner having a body with plurality of vanes extending radially outwardly from the spinner body.

2. The rod guide assembly of claim 1, wherein the receiver and the spinner are molded of dissimilar materials.

3. The rod guide assembly of claim 1, wherein the receiver is formed of a fiberglass reinforced polyphenylene sulfide compound and the spinner is formed of non-glass filled synthetic molding resin containing polymers and copolymers of polyamides.

4. The rod guide assembly of claim 1, wherein the vanes define a zigzag pattern along a line parallel to the axis of the sucker rod.