US 3889579 A
A system for pumping oil and a method for constructing a system in which a pump, disposed at the bottom of the well, is connected to the pump drive, at the top of the well, by a single length of reinforced plastic sucker rod having specific constructions and characteristics is disclosed.
Description (OCR text may contain errors)
United States Patent Wiechowski et al.
[ June 17, 1975  OIL WELL PUMPING SYSTEM HAVING 3.034566 5/1962 lflgckay 156/44! 1 S K D 3.129.282 4/1904 ynn 0 403/275 REINFORCED PLAST UC F R0 3.226.805 H1966 Scott et al 1 1 1. 403/275  Inventors: Joseph W. Wnech skl. San 3.378.426 4/l968 Medney 1 1 150 441 Clemente; Delmar S. Miller, 3,442,738 5/l969 Scott et al 156/441 Newport Beach; Richard C, 3,474,737 Ill/I969 Norman ct alm. 417/53 Kostner, Orange a of Marzocchi i. 3.684.622 8/1972 Goldsworlhy l56/44l  Assignee: Poly-Trusions, Inc., Santa Ana.
Cahf' Primary Examiner--William L. Freeh  Filed: Jan. 7, 1974 Attorney, Agent, or FirmKnobbe, Martens. Olson. 1211 Appl. No.: 431,124 Bear 52 us. (:1. 92/3; 417/545; 92 222 ABSTRACT [5|] Int. Cl. F0413 17/00; F04B 47/02 A System for pumping 0i] and a method for Construcb  Fleld of Search 4l7/545-554, ing a System in which a pump, disposed at the bottom 417/437! 572; 156/731 441; 403/275 404; of the well. is connected to the pump drive, at the top 92/248 222 of the well, by a single length of reinforced plastic sucker rod having specific constructions and characl56] References and teristics is disclosed.
UNITED STATES PATENTS 3.002.046 9 1901 Clapper 403/275 12 Clams 8 Drawmg guns y g o o Y/ 00/55 Z, /1
PATENTEDJUN17 I975 SHEET PATENTEDJUN 17 ms v 8 9 9 l5 7 9 SHEET 3 V /V \\\\\\\\\\\\\\\\\\\\\\Y14 I OIL WELL PUMPING SYSTEM HAVING REINFORCED PLASTIC SUCKER ROD This invention relates to petroleum engineering and production, and more specifically to systems and methods for pumping petroleum to the surface in oil wells.
More particularly, this invention relates to the construction of a system for pumping oil in which a single, continuous sucker rod ranging from several hundred to several thousand feet in length is run down the well and connected at the bottom to a pump and at the top to a drive for the pump. A particular sucker rod comprising glass fibers extending longitudinally of the rod bonded together with a thermoset resin. which may have a passageway therethrough, may be filled to give a desired density. and may be protected with wrapped sheathing or extruded coating to give greater strength and resistance to abrasion is disclosed.
Conventionally, sucker rods for oil well pumping systems have been made of steel sections. These sections are carried to the oil well site and individually extended down into the well and joined together using special or conventional thread connections. Typically. each of the connections is larger than the rod and, therefore constitutes an obstruction to the flow of oil out of the well. Steel rod weighs about 4 pounds per foot and, consequently. a long sucker rod becomes so heavy that most of the energy input is required simply to move the rod up and down. As a result, much energy is wasted and only a minor part of the energy is available for actually pumping oil.
Other disadvantages of the conventional steel sucker rods include the tendency of connections to collect paraffin, which increases the obstruction to the flow of oil, thus reducing production and increasing pumping energy requirements. Also, the practical length of conventional steel sucker rods is limited by the high density inherent in such constructions. Depending upon the particular type of rod involved, there exists a length beyond which it is not practical, for a given installation, to extend the rod. When all of the pumping power available is expended in simply raising and lowering the rod, or when the weight of the rod itself approaches the tensil strength of the rod at the upper end, no further extension of the rod is feasible.
In many oil fields. for example in the Midland-Odessa oil field area. corrosion of the steel sucker rods is an extremely serious problem, requiring that the sucker rods be replaced as often as every few weeks.
Cables, made of steel strands in the form of a wire rope, have been suggested in lieu of sucker rods. This suggestion permits the use of a continuous length without connections but does not solve the problem of corrosion and is not entirely satisfactory inasmuch as the cable is flexible and does not efficiently transmit the pumping energy from the pump drive to the pump. A sucker rod comprising a plurality of straight. longitudinally extended, spaced, flexible steel rod wires embedded in plastic, produced by extrusion of the plastic around the wires has been proposed; however. to the extent that this proposal would tend to overcome the density and weight limitations inherent in the use of steel rods, it fails in loss of tensil strength. In addition, any small crack, pinhole, or other defect in the plastic surrounding the wires. would subject the wires to corrosive action which would be even more severe than would be expected in the case of the conventional sucker rod because of the small amount of load bearing material. No successful application of either of these proposed constructions is known.
The simple substitution of resin bonded glass fiber sucker rod sections for the conventional steel rod has also been proposed. According to this proposal, each length of the resin bonded glass structure is fitted at each end with a connector, typically made of steel and having a much larger diameter than the rod, to permit the lengths of the rod to be connected together in the manner typical of the conventional rod structure. While this structure may reduce the weight of the sucker rod to some extent. much of the weight improvement is lost by the necessity for numerous heavy, bulky steel connection fittings at the ends of each section of sucker rod. The obstruction of the oil flow channel typical of the conventional sucker rod. is retained and perhaps even aggravated by the necessity for the bulky connections. In addition, the connections are subject to corrosion.
All efforts to use resin bonded fiberglass connectors, by machining the rod, using threaded connections. etc.. which are known, have not succeeded. One of the principle problems appears to be that the machining of resin bonded fiberglass structure cuts the longitudinal fibers and weakens the rod and/or the connector. The use of numerous connectors which weaken the rod or which are bulky and not easily connected and disconnected has proven unsatisfactory.
This invention overcomes many of the problems and disadvantages inherent in the prior art devices. Chemical resistance is provided, overcoming the corrosion problem. Lightness coupled with high tensil strength overcomes the weight problems of the prior art, and the oil flow channel is left free of obstruction. These and other improved features of the present invention will become apparent upon consideration of the following.
A pumping system for oil wells and the like is constructed by placing a pump in an oil well near the bottom in a reservoir of petroleum to be pumped to the surface. A pump drive is placed at the top of the oil well and the pump drive is connected to the pump by a sucker rod. In this invention, the sucker rod is of sufficient length to reach from the drive to the pump and is constructed of a mulitplicity of glass fibers bonded together to form a semi-rigid rod. The bonding material is a thermosetting organic resin. Fittings are fixed at respective ends of the sucker rod for connection to the pump and to the drive. The sucker rod is run into the well and connected at the lower end to the pump and at the upper end to the drive to complete the pumping system. The sucker rod is fabricated by pulling a plurality of rovings of glass fibers. each comprising a multiplicity of fibers, through a coating vat or other resin application means to coat the fiber with a liquid thermosetting resin. The rovings coated with the resin are pulled through a forming die and the formed rod is pulled through a curing station where the thermosetting resin is cured to form a single, semi-rigid continuous rod having a length sufficient to extend from the drive to the pump.
The rod may be made in many configurations. For example, the rod may be hollow having a passage through the length thereof. The passage may be filled, fully or partially, with a weighting material. e.g. lead, particulate matter, beads, etc., and may include cables or conductors to communicate conditions in the well to the surface or to give control signals to devices in the well. The rod may be covered with one or more layers of bonded glass fibers helically wound or woven around the rod and may be protected from abrasion by an extruded or otherwise applied covering of abrasion resistant material.
The system is illustrated schematically in FIG. 1 and FIGS. 2, 3, 4, 5 and 6 illustrate various alternative configuration for the sucker rod.
FIG. '7 and FIG. 8 show examples of connector designs which can be used to connect the rod to the pump or to the drive.
The method of constructing the oil pumping system of the invention is illustrated schematically in FIG. I in which the well is indicated at l. The sucker rod 2 is carried to the well site in one continuous piece, or is fabricated on site. In the exemplary embodiment illustrated, the sucker rod is reeled on very large diameter reels, indicated at 3, and run down the well 1 and connected to the pump 4 which is disposed near the bottom of the well. Once the rod has been run down the proper length into the well, the upper end is connected to a pump drive 5.
One embodiment of the sucker rod construction, absent the end connectors, is illustrated in FIG. 2. The rod 10 is made up of a multiplicity of glass fibers running generally parallel to each other longitudinally of the rod. The glass fibers are indicated by numeral 12 in FIG. 2 and are bonded together by a thermosetting resin 14.
The glass fibers may all be straight and unidirectional extending longitudinally of the rod. This gives great tensil strength to the rod, but such a rod is not highly resistant to longitudinal delamination; i.e. splitting along the longitudinal axis of the rod. Resistance to longitudinal splitting can be improved substantially by using all spun glass fiber roving or a mixture of spun roving glass fibers and straight unidirectional glass fi bers, the latter giving a higher tensil strength than the former. The spun glass fiber roving tends to give greater transverse strength and resistance to longitudinal splitting at very modest sacrifice in longitudinal tensil strength.
While this specification speaks mainly in terms of glass fibers, which are a preferred fiber for the purposes of this invention because of their high tensil strength, the invention is not limited to glass fiber usage, but would include inorganic fibers of various types, e.g. graphite fibers, as well as natural and synthetic organic fibers such as polyester fibers. Combinations of inorganic and organic fibers of the various types may be used to provide a proper balance of tensil strength, weight, resistance to abrasion, chemical resistance and transverse resistance to splitting. Glass fibers, other inorganic glass fibers and organic fibers, as well as various blends and mixtures of the same may be used in the various structures comprising bonded fibers disclosed hereinafter and discussed throughout this specification.
Polyester and epoxy organic resins are the preferred bonding materials for forming a rigid rod by bonding the fibers together. Polyester bonding of glass fibers, as a fabrication technique, is well known. While less commonly used, epoxy is also well known as a bonding material for forming glass fiber reinforced articles. The techniques of formulation and application of these resins to produce various types of structures is well known in the art and abundant descriptive information is available. Methods for forming elongate glass fiber reinforced structures generally of the type described herein are also well known. The pultrusion method, for example, is quite well known and various techniques for using this method in the fabrication of elongate articles has been described, see, for example, US. Pat. Nosv 3,556,888 and 3,674,601, and the method has been described in various technical publications; see, e.g. 1973-74 Modern Plastics Encyclopedia", page 428. Fibers, bonding resins, techniques and equipment generally suitable for producing the sucker rod constructions described herein are described in l973-74 Modem Plastics Encyclopedia and in technical literature cited therein, and generally in the literature.
Fibers such as carbon, graphite, boron, polyamides, polyesters, and other equivalents as well as glass may be bonded with polyesters, epoxies, thermoset acrylics, polycarbonates, vinyl esters, polyamides, ABS acrylonitrile-butadiene-styrene, and other equivalents as well as the better polyester bonding resins.
The sucker rod 10 is described here as being semirigid. A semi-rigid rod, within the meaning of the present invention, is one which is sufficiently flexible to be wound on a very large reel or equivalent carrier or capable of being bent without permanent deformation in a curve having a large radius of curvature. Generally speaking, the semi-rigid rod referred to in this invention has a diameter of from about inches to about 2 inches, or more, and its capability of being bent is limited to a radius of curvature of at least about five feet and typically of greater than 6.5 or 7 feet, but is must be capable of bending on a radius of curvature of about 15 feet to 20 feet. Another characteristic contemplated within the meaning of semi-rigid, as used here, is that the rod is sufficiently rigid to transmit compression force down the rod from the pump drive to the pump without being forced against the walls of the casing in such a manner as to cause severe abrasion and frictional resistance to movement. This characteristic is to be distinguished from a wire cable or plastic coated wire cable, suggested previously, which did not 'permit compressive forces to be transmitted downwardly through the rod. The semi-rigid sucker rod c0ntemplated by this invention does not substantially reduce the pump stroke at the bottom of the well by reason of slack in the rod, but rather transmits the majority of the downward movement of the pump drive to the pump.
In many instances no downward force is applied directly from the pump drive, the downward force being derived from the weight of the sucker rod in the well. The semi-rigid sucker rod of this invention transmits the weight of the rod to the pump, a characteristic which distinguishes it from the flexible cable like rods previously proposed which tend to sag, coil and fold rather than transmit the downward compressive forcev The downward force resulting from the weight of the rod is an important factor in the design of sucker rods for oil well pumping. The steel rod, having a density of about 4 pounds per foot, is excessively heavy and transmits an undesirable and unneccessary downward force to the pump and the lower portions of the rod. A simple resin bonded glass fiber rod having a diameter of about l inch may be too light for some oil well pumping systems. The density of such a rod will be in the range of about 0.6 to about 0.8 of a pound per foot, depending upon the particular resin used and the ratio of resin to glass fiber in the rod.
Generally, a weight of at least about 1 pound per foot is desirable for proper operation of an oil well pumping system. One of the particularly advantageous features of this invention is that the density of the sucker rod can be varied uniformly along the length of the rod by adding filler materials to the resin formulation. For example, in formulating the bonding resin, high density fillers, such as lead phosphate. or other heavy metal salts or high density powders are added to the bonding resin. When the bonding resin is applied to the glass fiber roving, the filler is bonded as an integral part of the rod, increasing the density of the rod. By selecting an appropriate ratio of resin to glass to filler. a great variety of rod densities can be achieved.
Another method of achieving variable rod densites is illustrated in FIG. 3 in which the rod is constructed in the manner previously described of fibers 22 bonded together with a resin. filled or unfilled, 24, but the rod has a central core 26 of lead or other high density material. The core may be non-load bearing, as in the case of lead, or it may be load bearing material such as a steel wire. which would contribute to the tensil strength of the rod as well as increasing its density. The core may extend the full length of the rod or only part of the length, where variable density is desired. The high density portion of the rod may be placed at the bottom, at the top, or otherwise along the length of the rod. This rod is formed in the same manner except that in fabrication the glass fiber roving is positioned by the die around the central core element before the resin is cured.
A hollow center rod 30 made up of fibers 32 bonded together with a resin 34, in the manner previously described, but constructed so as to provide a hollow center 36 is illustrated in FIG. 4 as an alternative to the embodiment illustrated in FIG. 3. A pair of insulated wires, an electrical cable, or other means of communicating sensing or control signals between the bottom of the well and the top may be included in the hollow passageway through the center. Likewise, the density of the rod may be varied by adding granular high density material, such as lead shot, after the rod is in position.
FIG. 5 illustrates a rod of the type illustrated in FIG. 3 with additional structure; however, any of the preceeding rod constructions and other rod constructions can be used in the embodiment used in H6. 5. The rod 40, of FIG. 5, is, in the particular rod illustrated, made up of fibers 42 bonded by resin 44 surrounding a high density core 46 which, together, form the central rod construction 48. The rod 40 also includes a first sheath 50 and a second sheath 52 and an outer sheath 54. In the illustrative embodiment of FIG. 5, the sheath 50 is constructed of fibers wound around the central rod structure 48 helically so as to have a substantial transverse directional component and bonded together to form an integral sheath enclosing the entire central rod structure. Organic or inorganic fibers may be used but for this application, the organic polyamide (nylon), polyester Dacron), acrylic, polyvinyl alcohol, polypropylene and other organic fibers being preferred.
Sheath 52 is similarly constructed but, in the exemplary embodiment of FIG. 5, the sheath fibers are wound helically in the opposite direction. The purpose of the sheaths 50 and 52 is to protect the central load bearing and load transmitting rod 48 from abrasion and corrosion and to give the overall rod 40 greater resistance to longitudinal splitting resulting from delamination or separation of the fibers in the central rod structure 48. The density of the rod is increased by the addition of the sheath 50 and 52 and the tensil strength is also increased, but the increase in tensil strength is secondary to the accomplishment of the principal purposes of sheathing the central structure and this in crease in tensil strength is not equivalent to that which would be accomplished by merely increasing the diameter of the central structure.
The sheath 54 is an additional protective sheating extruded about the underlying structure. Typically, this sheathing would be made of polyamide (nylon), ultra high density polyethylene, polypropylene, Teflon (polytetrofluoroethylene), or other synthetic extrudable material. This material preferably has a higher resistance to abrasion than the underlying structure and may be self lubricating as is typical of the polymers mentioned.
FIG. 6 illustrates another variation in which the rod 60 has a central structure made up of a multiplicity of fibers 62 bonded by resin 64 in a hollow configuration having a passage 66 extending longitudinally of the rod. This passageway may be used in the manner previously discussed in connection with the illustrative configura tion shown in FIG. 4. The central core structure 68 is protected by a sheath 70 made up of a multiplicity of fibers, organic or inorganic as previously discussed, which are woven about the central structure to form a fabric sheath which is bonded together by a resin of the type previously discussed and which has a substantially transverse directional component. The central struc ture 68 is constructed in the manner previously discussed and the sheath is constructed by providing a weaving device at the point of fabrication, either before or after setting the resin, to weave the fibers around the central structure. The sheath is then saturated with a bonding resin and the sheath bonding resin is cured, as described in the patent and literature references included herein by reference previously.
Sheaths of the type described with respect to the il- Iustrative embodiment of FIG. 6 may be used in constructions such as illustrated in FIG. 5, alone or in combination with other sheaths. Likewise, the rod 60 illustrated in FIG. 6 can be further protected by the addi tion of a sheath of the type referred to at 54 in FIG. 5. Also, the central structure may be of any of the types heretofore described or referred to.
Any of the rod structures previously discussed can be given greater transverse strength, resistance to splitting, by incorporating, in the resin, short fibers to improve the lateral strength of the construction as well as by the use of spun glass fiber roving.
The advantages of the continuous reinforced plastic sucker rod in an oil well pumping system include the following: The sucker rod is chemically inert and the resin bonding and the fiber system can be varied to meet various environments. Chemical inertness can also be varied to meet particular requirements by appropriate sheathing materials. The rod is free of joints and consequently the sucker rod is considerably less expensive to manufacture, to install in the well and to remove from the well, and obviates the extreme disadvantage of the rod connectors interfering with flow through the casing and the collection of paraffin about these connections. The weight and linear density can be regulated to fall through the fluid column, ie, apply gravitational force of the proper magnitude to the pump, without slack, thus permitting efficient operation of the pump. The weight of the rod and the downward force on the pump can be varied to meet particular conditions of fluid viscosity, depth, etc. The longitudinal tensil strength, the transverse strength and the circumferential integrity of the rod can be tailored to meet particular strength requirements as required for handling and operation. The outer surface can be protected against abrasion as well as environment factors such as particularly severe corrosion. The rod can be constructed with a passage through its center and, therefore, can be used for instrumentation and for venting of gasses or lighter fluids from the bottom of the well or the injection of fluids down into the well.
Any connector suitable for securing the ends of the rod to the pump and to the pump drive, respectively, may be used.
Unlike the segmented rods of the prior art, the single connector at either end of this rod may be tapered to meet specific conditions and may be protected from corrosion by appropriate coating, or other protective measures, since the position of the connector is fixed by being connected to the pump at one end and to the pump drive at the other. Joints as required to connect the sucker rod to the pump and to the drive may be of the type described in National Bureau of Standards Re port No. NBSIR 73-129 Evaluation of GRP Rod and Rope Materials and Associated End Fittings", December 1972, Final Report.
The fittings illustrated in FIGS. 7 and 8 are intended as merely illustrative of the types which may be used and selection of a particular design depends on the environment and circumstances of use. In FIG. 7, the rod 80 extends into a cylindrical connector 82 which is threaded at one end and tapered at the other. The rod is held in the connector by a plurality of wedges illustrated at 84 and 86 which are pressed against the rod by the conical configuration of the cylinder 82. A potting compound, such as an epoxy thermosetting resin, indicated at 88 bonds the end of the rod in the cylinder and bonds the wedges in the cylinder to the cylinder and to the rod.
In FIG. 8, the rod 90 is held in the cylinder 92 simply by a potting compound 94. The potting compound would typically be an epoxy or other thermosetting adhesive resin. The thickness of the potting compound in 94 is exaggerated in FIG. 8 for illustrative purposes.
In FIGS. 7 and 8, thread connectors are illustrated but it will be apparent that bayonet connectors, hook connectors, or connectors of any other desired configuration may be utilized. These connectors may be of substantial length to extend along the rod a sufficient distance to distribute the stress in the rod throughout the entire rod construction, thus obviating one of the difficulties faced in providing a multiplicity of connectors for fiberglass rods. Where many connectors are required, the connectors must, to be of useable weight and to minimize construction time, be comparatively short and such connectors often tend to concentrate stresses in the skin portions of the rod.
It will be apparent that one or more of the protective sheaths may be peeled back or removed at the entry point into the connector to provide direct fastening of the load bearing central structure to the connector.
In the illustrated embodiments, the rods are shown as being generally circular; however, other cross sectional shapes, such as eliptical to aid in reducing the diameter of the core and giving the rod greater flexibility in one dimension than in the other may be fabricated, as might be required for particular systems.
The embodiments illustrated in the drawings are intended to illustrate the various constructions which may be used in the oil well pumping system of the invention and are not intended to limit the invention to the structures specifically illustrated. Likewise, while the preferred materials and embodiments have been principally discussed, and other illustrative materials have been referred to, the itemization of various specific materials is not intended to be exhaustive of equivalent materials and equivalent steps. For example, while this invention generally contemplates a single rod in a well, an equivalent construction can be found, in appropriate circumstances, where two or perhaps more long lengths of rod were so joined as, in effect, to be one length or equivalent to one length within the system under consideration. Finally, while the invention and many of its facets have been described in considerable detail, it is contemplated that the scope of the invention will be according to the definitions in the claims and is not limited to the specific illustrative examples set forth in the body of the specification.
What is claimed is: 1. A pumping system for oil wells and the like which comprises a pump in a well near the bottom thereof, a pump drive near the top of the well, and a sucker rod drive connecting the drive to the pump, the improvement wherein:
the sucker rod is of sufficient length to reach from the drive to the pump, said rod being constructed ofa multiplicity of glass fibers bonded together into a semi-rigid rod by a set organic resin; and
fittings affixed at the respective ends of the sucker rod for connection to the pump and to the drive respectively.
2. The system defined in claim 1 wherein the sucker rod comprises a single, continuous, semi-rigid rod consisting essentially of generally parallel elongate glass fibers running lengthwise of the rod and resin bonding the fibers together.
3. The system defined in claim 2 wherein the sucker rod comprises a single, continuous, semi-rigid rod consisting essentially of generally parallel elongate glass fibers running longitudinally of the rod, thermoset resin bonding the fibers together, and a high density filler, said rod having a density of at least about I pound per foot and less than 4 pounds per foot sufficient to transmit energy from the drive to the pump.
4. The system defined in claim 2 wherein the sucker rod comprises a single, continuous, semi-rigid rod consisting essentially of generally parallel glass fibers running lengthwise of the rod and thermoset resin bonding the fibers together in a rod configuration having a passageway extending along the length of the rod.
5. The system defined in claim 4 wherein the sucker rod comprises a dense filler material in said passageway for at least a portion of the length of the rod of give the rod an average density of greater than I pound per foot and less than about 4 pounds per foot sufficient to transmit pumping force efficiently to the pump.
6. The system defined in claim 4 wherein the sucker rod comprises means in the passageway for permitting communication of sensing signals or control signals be tween the pump and a station outside the well.
7. The system defined in claim 2 wherein the sucker rod further comprises at least one sheath enclosing the rod 8. The system defined in claim 7 wherein the sheath comprises a multiplicity of glass fibers having a substantial transverse directional component bonded together to enclose the rod to thereby increase the delamination resistance and abrasion resistance of the sucker rod.
9. The system defined in claim 8 wherein the sheath comprises a multiplicity of glass fibers running helically around the rod along the length thereof, and thermoset resin bonding said helically extending fibers together in at least one continuous sheath enclosing the rod.
10. The system defined in claim 8 including a sheath which is an extruded, flexible polymer layer having greater abrasion resistance than the resin bonded glass fiber material.
H. The system defined in claim 8 wherein the sheath comprises a multiplicity of glass fibers woven to form a fabric sheath around the rod along the length thereof, and thermoset resin bonding said fiber sheath together in at least one continuous sheath enclosing the rod.
12. The system defined in claim ll including a sheath which is an extruded, flexible polymer layer having greater abrasion resistance than the resin bonded glass fiber material.
i l =1 l