Abstract:
An oil well sucker rod guide protects the rods and production tubing from frictional wear during the vertical reciprocation pumping action. The guide has a sleeve enveloping the sucker rod with raised ribs contacting the tubing in an opposed fashion. The raised ribs are circumferentially sequenced to contact the entire circumference of the tubing and provide oil flow-through passages between the sleeve and the tubing. The raised ribs have side and inside end walls angled and contoured to increase through-put of oil in the tubing.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to well production technology and more particularly concerns guides used to center sucker rods in well production tubing and to remove paraffin from the inner surface of the tubing. 
     Oil wells typically have a depth in a range of several hundred to several thousand feet. Sucker rods, each 25′ to 30′ long and ⅝″ to 1⅛″ inches in diameter, are linked together inside production tubing with a 2″ to 3″ inches inside diameter between an above-ground reciprocating jack and a bottom hole pump. 
     Deviation of the well components from vertical is a well-recognized problem. The production tubing axial alignment is going to deviate from vertical over its depth and the greater the well depth the more likely and more serious the deviation. The sucker rod string axial alignment is going to deviate from vertical between the jack and the pump because the pump reciprocation is delayed in comparison to the jack reciprocation. Whatever the cause, the deviation renders the rods, the rod couplings and the production tubing vulnerable to metal-to-metal frictional wear during well operation. Centering the sucker rods in the production tubing reduces such frictional wear. 
     Congealing paraffin is another well-recognized problem. In many oil wells, paraffin that remains mixed with warm-hot crude oil congeals as the oil cools while rising to the surface. The congealed paraffin coats the rods and the tubing and clogs the product flow paths. Removal of paraffin from the tubing wall increases the throughput of product from the well. 
     Sucker rod guides been devised for centering sucker rods inside their tubing and acting as a bushing to smooth out the pumping action. Some of these guides also serve the added purpose of scraping the tubing wall to break clogs and maintain acceptable rates of flow of product from the well. Some are made of plastic suitable to withstand hostile well conditions including high temperatures, harsh chemicals, sand or particulates, and even electrolysis. The problem with known sucker rod guides is that one of their primary purposes, maintaining high productivity, is often compromised in deference to another primary purpose, long-term operation. 
     As an example, if a guide does not adequately scrape the paraffin from the tubing, the tubing will eventually clog and reduce or cease production. In order to achieve adequate long term scraping, more and/or wider radial ribs are incorporated in the guide so as to increase its scraping circumference on the tubing. But incorporation of more and/or wider ribs structurally decreases the cross-sectional area of the product flow paths, reducing productivity. Thus, the benefit of increased production gained by better scraping is offset by lost production due to structurally constricted flow. 
     In another example, if a guide does not grip its rod securely enough to prevent it from sliding on its rod, its scraping benefit is sooner or later diminished or lost. In order to maintain longer grip security, the guide length is generally increased to increase its rod gripping surface. But a longer guide increases the drag on product flow through the guide, reducing productivity. Thus the benefit of increased production gained by longer connection between the guide and the rod is offset, once again by lost production due to structurally constricted flow. 
     It is, therefore, a primary object of this invention to provide a sucker rod guide which assists in maintaining an acceptable, long-term rate of product flow in a well production tubing. 
     It is also an object of this invention to provide a sucker rod guide which simultaneously affords a higher tubing contact area and a higher flow cross-sectional area than known guides. 
     It is another object of this invention to provide a sucker rod guide which simultaneously affords a higher flow cross-sectional area to guide length ratio than known guides. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the invention, guides for sucker rods reciprocating in a well production tubing are provided which will be attached at spaced intervals to the rod and extend diametrically from the rod to the production tubing. The guides are made of plastic material suitable to withstand the environmental and operational conditions in which they will be used. 
     The guide has a cylindrical sleeve with a lengthwise concentric passage and a plurality of ribs extending radially outwardly from the sleeve. Each of the ribs has a circumferential outer surface and their surfaces, taken together, define a common cylinder. Thus, in a single vertical stroke of the guide, the ribs have a 360° capability of contacting the surface of the inner wall of the production tubing. The outer circumference of the common cylinder defined by the outer circumferential surfaces of the ribs is so substantially congruent with the inner circumference of the production tubing during operation as to provide suitable frictional contact to remove paraffin over 360° of the inner wall of the production tubing during continuous pumping operation. The ribs also have sidewalls contoured to co-operate with the sleeve and the production tubing to define flow paths for passage of well product between the sleeve and the production tubing during reciprocation of the guide in the production tubing. At least one of the ribs has interior end walls inclined at an acute reverse angle, thereby increasing product throughput without decreasing available rib surface contact area with the production tubing. 
     In a preferred embodiment, the ribs define reversing symmetric product flow paths. A first pair of lengthwise ribs symmetrically spaced at an obtuse angle from a diametric plane of the sleeve extend radially outwardly from one end portion of the sleeve. A second pair of lengthwise ribs centered on the diametric plane extend radially outwardly in opposite directions from a middle portion of the sleeve. A third pair of lengthwise ribs symmetrically spaced at the same obtuse angle as the first but oppositely from the diametric plane as the first extend radially outwardly from the other end portion of the sleeve. The first, second and third pairs of ribs have circumferential outer surfaces defining a common cylinder. Thus, in a single vertical stroke of the guide, the ribs have a 360° capability of contacting the surface of the inner wall of the production tubing. The outer circumference of the common cylinder defined by the outer circumferential surfaces of the ribs is so substantially congruent with the inner circumference of the production tubing during operation as to provide suitable frictional contact to remove paraffin over 360° of the inner wall of the production tubing during continuous pumping operation. All of the ribs have sidewalls co-operable to define reversing symmetric product flow paths for passage of well product between the sleeve and the production tubing during reciprocation of the guide in the production tubing. Each of the ribs of the first and third pairs have inner end walls inclined at an acute reverse angle, thereby increasing product throughput without decreasing available rib surface contact area with the production tubing. The outermost portions of the sleeve and the first and third pairs of ribs may be tapered toward the sleeve passage to streamline the flow paths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a perspective view of a sucker rod guide according to the invention; 
         FIG. 2  is another perspective view of the sucker rod guide of  FIG. 1 ; 
         FIG. 3  is a first elevation view of the sucker rod guide of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view taken along the line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view taken along the line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a cross-sectional view taken along the line  6 - 6  of  FIG. 3 ; 
         FIG. 7  is a second elevation view of the sucker rod guide of  FIG. 1  taken orthogonally in relation to  FIG. 3 ; 
         FIG. 8  is an end elevation view of the sucker rod guide of  FIG. 1  taken in the direction  8 - 8  of  FIG. 3 ; 
         FIG. 9  is a cross-sectional view taken along the line  9 - 9  of  FIG. 7 ; 
         FIG. 10  is a perspective view of the sucker rod guide of  FIG. 1  in a first orientation illustrating product flow paths through the guide during its down stroke in a well production tubing; 
         FIG. 11  is a perspective view of the sucker rod guide of  FIG. 1  in a second orientation rotated 180° from the orientation of  FIG. 10  illustrating product flow paths through the guide during its down stroke in a well production tubing; and 
         FIG. 12  is an end elevation view of the sucker rod guide of  FIG. 1  on a sucker rod in a production tubing. 
     
    
    
     While the invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment or to the details of the construction or arrangement of parts illustrated in the accompanying drawings. 
     DETAILED DESCRIPTION 
     In  FIGS. 1-12 , a preferred embodiment of an improved sucker rod guide  10  is illustrated. As best seen in  FIG. 12 , the guides  10  will be mounted at spaced intervals on and reciprocate with sucker rods R strung in a well production tubing T. 
     Looking first at  FIGS. 1 and 2 , each guide  10  has a cylindrical sleeve  11  with a lengthwise concentric passage  13  in which the sucker rod R will be gripped and a plurality of ribs  15 ,  17  and  19  which are arranged in pairs and extend radially outwardly from the sleeve  11 . 
     As best seen in  FIGS. 3 ,  6 ,  7  and  9 , two ribs  15   a  and  15   c  are on one end portion of the sleeve  11 , two ribs  17   b  and  17   e  are on a center portion of the sleeve  11  and two ribs  19   d  and  19   f  are on the other end portion of the sleeve  11 . 
     As best seen in  FIGS. 4 ,  5  and  8 , the one end portion ribs  15   a  and  15   c  are symmetrically spaced at an obtuse angle  21  bisected by a diametric plane  23  taken through the sleeve  11 , the center portion ribs  17   b  and  17   c  are symmetrically oppositely spaced on the diametric plane  23  and the other end portion ribs  19   d  and  19   f  are symmetrically spaced at an obtuse angle  25  bisected by the diametric plane  23  but on the opposite side of the sleeve longitudinal axis  27  than the one end portion ribs  15   a  and  15   c . 
     As best seen in  FIG. 8 , in a clockwise direction around the longitudinal axis  21  of the sleeve  11 , the ribs appear sequentially as  15   a ,  17   b ,  15   c ,  19   d ,  17   e  and  19   f . The outer circumferential surfaces of the ribs  15   a  and  15   c ,  17   b  and  17   c  and  19   d  and  19   f , taken together, define a common cylinder  29 . Thus, in a single vertical stroke of the guide  10 , the ribs  15   a ,  17   b ,  15   c ,  19   d ,  17   e  and  19   f  have a 360° capability of contacting the surface of the inner wall of the production tubing T. 
     This 360° capability may, however, not be achieved in any given stroke of the sucker rod string. Neither the production tubing T nor the sucker rod string are independently likely to be axially perfectly straight or together in perfect alignment. Furthermore, in order to minimize the likelihood of creation of back-pressure in the tubing T, the guide  10  must in any event be slightly less in diameter than the inner diameter of the tubing T. Therefore, like known sucker rod guides, the present sucker rod guides  10  are typically ⅛″ to 3/16″ in diameter less than the inner diameters of their tubing T, which ranges between 2″ and 3″. As with known guides, the sucker rod strings are incrementally rotated in the tubing T from stroke-to-stroke during operation so that the entire circumference of the guide  10  has the opportunity of contacting the entire circumference of the tubing T. 
     In this context, it can be said that the outer circumference of the common cylinder  29  defined by the outer circumferential surfaces of the ribs  15   c ,  17   b ,  15   c ,  19   d ,  17   c  and  19   f  is so substantially congruent with the inner circumference of the production tubing T during operation as to provide suitable frictional contact to remove paraffin over 360° of the inner wall of the production tubing T during continuous pumping operation. 
     Looking at  FIGS. 4 ,  5  and  8 , the ribs  15  and  19  have proximal non-radial sidewalls  35  and  39 , respectively, and distal radial sidewalls  45  and  49 , respectively, and the ribs  17  have parallel opposed chordal sidewalls  37  and  47 . Looking at  FIGS. 3 ,  6 ,  7  and  9 , the ribs  17  on the center portion of the guide  10  are lengthwise offset and are at least wide enough to contact those circumferential portions of the production tubing T not contacted by the end portion ribs  15  and  19 . They are also inverted with their ends tapered at different angles toward their respective ends of the guide  10 . The angle of convergence  51  of their innermost ends  53  is greater than the angle of convergence  55  of their outermost ends  57 . As shown, the greater angle of convergence  51  is 50° and the smaller angle of convergence  53  is 40°. The end portion ribs  15  and  19  have interior end walls  65  and  69 , respectively, inclined at an acute reverse angle  61 , thereby increasing product throughput without decreasing rib surface contact with the production tubing T. As best seen in  FIGS. 3 and 9 , the convergence angles  51  and  55  of the center portion ribs  17  and the contours of the junction zones of the proximal sidewalls  35  and  39  of the end portion ribs  15  and  19  with their interior end walls  65  and  69 , respectively, cooperate to streamline flow between their opposed surfaces and through the guide  10 . The outermost ends  75  and  79  of the ribs  15  and  19  are also tapered, as shown parallel to their respective interior end walls  65  and  69 . As herein described and best understood in reference to  FIGS. 3 and 6 , the guide  10  is symmetric about an end-to-end rotation axis  71 , so the guide  10  can be mounted on a sucker rod R with either end of the guide  10  up. 
     Looking at  FIGS. 10-12 , the flow paths defined by the sleeve  11  and ribs  15 ,  17  and  19  of the guide  10  and the inner wall of the production tubing T during the process of artificial lift can be understood. During the upstroke, the oil column  80  moves up the tubing T with the guide  10  a distance equal to the stroke of the pump jack (not shown). The lifted oil stays in that position during the down stroke. Oil does not flow around the guide  10  during the upstroke. During the down stroke, the guide  10  attacks and moves through the oil column  80 , gathering another quantity of crude equal to the stroke. The guide  10  passes through the column of oil  80 , splitting it initially into two main columns  81  and  82  which are further each split into two secondary columns  83  and  85  and  84  and  86  which are then converged into two columns  87  and  89  and back to one column  90  at the upper end of the guide  10 . A number of smaller splits  91  and convergences  93  occur at the leading edges of the ribs  15 ,  17  and  19  which are slightly spaced  95  from the inner wall of the tubing T, as best seen in  FIG. 12 , so the oil does flow around the guide  10  during the down stroke. The flow paths  91  and  93  relieve the back pressure which can otherwise be great enough to slow the reciprocating action of the lifting process. Each upstroke adds to the volume of the lifted oil column  90  until the lifted oil reaches the surface. The guide  10  serves mainly as a bushing or centralizer of the rod R in the tubing T and also provides the ribs  15 ,  17  and  19  as a sacrificial material for scraping the tubing T. The guide functions as a bushing or centralizer on both the upstroke and the down stroke, helping to prevent metal to metal contact of the rods R, couplings (not shown) and tubing T. 
     The guides  10  are made of plastic material chosen to withstand the environmental and operational conditions in which they will be used. They are molded to surround portions of the sucker rod R and substantially, within the constraints of accounting for axial misalignment and minimizing likelihood of back-pressure in the tubing T, fill the space between the surrounded portion of the rod R and the production tubing. Each guide  10  is a full circumference bushing and scrapes the full inner circumference of the production tubing T as the rods R reciprocate in the well. The angles and radii of the guide flow paths are streamlined to enhance the overall anti-turbulence or fluid dynamics of the guide  10 . Anti-turbulence surface materials may further enhance the guide&#39;s flow-through performance. 
     Thus, it is apparent that there has been provided, in accordance with the invention, a sucker rod guide that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in connection with a specific embodiment thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art and in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit of the appended claims.