CONTINUOUS CARBON FIBER SUCKER ROD AND METHOD OF MANUFACTURE

Abstract

A continuous length composite sucker rod assembly is provided for use in down-hole wells. The assembly can include a plurality of parallel composite strands forming an elongate rod. The strands can be encapsulated with a thermoplastic polymer by co-extrusion. A terminus can be affixed to both ends of the length of sucker rod by splaying the strands out into a conical cavity within the terminus and casting a polymer wedge plug. The resulting sucker rod assembly can be readily coiled in a transportable diameter by virtue of the composite strands being able to twist when the rod is coiled and untwist when the rod is un-coiled.

Claims

1. A method for manufacturing a length of rod, the method comprising: drawing a plurality of pultruded carbon fiber rods through a collector die to organize the plurality of pultruded carbon fiber rods into a predetermined cross-section shape; drawing the plurality of pultruded carbon fiber rods through an extrusion die; and encapsulating the plurality of pultruded carbon fiber rods in a jacket of heated thermoplastic polymer by extruding the heated thermoplastic polymer about the plurality of pultruded carbon fiber rods through the extrusion die.

2. The method as set forth in claim 1, further comprising spooling the encapsulated plurality of pultruded carbon fiber rods.

3. The method as set forth in claim 1, further comprising cooling the encapsulated plurality of rods after exiting the extrusion die.

4. The method as set forth in claim 1, further comprising fitting an end fitting cone onto at least one end of the length of rod, the end fitting cone further comprising a coupling pin.

5. The method as set forth in claim 1, wherein one or more of the pultruded carbon fiber rods comprises a composition of carbon fiber and epoxy.

6. The method as set forth in claim 5, wherein the composition further comprises one or more from a group comprising of fiberglass, phenolic resin, vinyl ester resin, polyester resin, benzoxyzene resin and cyanurate ester resin.

7. The method as set forth in claim 1, wherein the thermoplastic polymer comprises one or more of a group comprising of high density polyethylene, polyetherimide, polyphenylenesulfide and polyetheretherketone.

8. A system for manufacturing a length of rod, the system comprising: at least one spool for providing a supply of a plurality of pultruded carbon fiber rods; a collector die for organizing the plurality of pultruded carbon fiber rods into a predetermined cross-section shape; an extrusion die configured for encapsulating the organized plurality of pultruded carbon fiber rods with heated thermoplastic polymer to form the length of rod; and a puller unit configured for pulling the encapsulated plurality of pultruded carbon fiber rods from the at least one spool through the collector die and the extrusion die.

9. The system as set forth in claim 8, further comprising a take-up spool for spooling the length of rod.

10. The system as set forth in claim 8, further comprising a cooling trough configured for cooling the length of rod after exiting the extrusion die.

11. The system as set forth in claim 8, further comprising means for fitting an end fitting cone onto at least one end of the length of rod, the end fitting cone further comprising a coupling pin.

12. The system as set forth in claim 8, wherein one or more of the pultruded carbon fiber rods comprises a composition of carbon fiber and epoxy.

13. The system as set forth in claim 12, wherein the composition further comprises one or more from a group comprising of fiberglass, phenolic resin, vinyl ester resin, polyester, resin, benzoxyzene resin and cyanurate ester resin.

14. The system as set forth in claim 8, wherein the thermoplastic polymer comprises one or more of a group comprising of high density polyethylene, polyetherimide, polyphenylenesulfide and polyetheretherketone.

15. A length of rod comprising a plurality of pultruded carbon fiber rods encapsulated in thermoplastic polymer, manufactured using a method as set forth in claim 1.

16. A length of rod comprising a plurality of pultruded carbon fiber rods encapsulated in thermoplastic polymer, manufactured using a system as set forth in claim 8.

17. The length of rod as set forth in claim 15, further comprising an end fitting cone fitted onto at least one end of the length of rod, the end fitting cone further comprising a coupling pin.

18. The length of rod as set forth in claim 15, wherein one or more of the pultruded carbon fiber rods comprises a composition of carbon fiber and epoxy.

19. The length of rod as set forth in claim 18, wherein the composition further comprises one or more from a group comprising of fiberglass, phenolic resin, vinyl ester resin, polyester resin, benzoxyzene resin and cyanurate ester resin.

20. The length of rod as set forth in claim 15, wherein the thermoplastic polymer comprises one or more of a group comprising of high density polyethylene, polyetherimide, polyphenylenesulfide and polyetheretherketone.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1A is a side elevation cross-section view depicting a round carbon fiber sucker rod jacketed by an extruded polymer jacket and comprising 37 each 3.3 mm pultruded fiber rods.

[0023] FIG. 1B is a side elevation cross-section view depicting a round carbon fiber sucker rod jacketed by an extruded polymer jacket and comprising 30 each 3.3 mm pultruded fiber rods.

[0024] FIG. 1C is a side elevation cross-section view depicting an oval carbon fiber sucker rod jacketed by an extruded polymer jacket and comprising 29 each 3.3 mm pultruded fiber rods.

[0025] FIG. 1D is a side elevation cross-section view depicting a polygonal carbon fiber sucker rod jacketed by an extruded polymer jacket and comprising 37 each 3.3 mm pultruded fiber rods.

[0026] FIG. 1E is a side elevation cross-section view depicting a polygonal carbon fiber sucker rod jacketed by an extruded polymer tube drawn down onto 37 each 3.3 mm pultruded fiber rods.

[0027] FIG. 2 is a side elevation view depicting a system carrying out a continuous extrusion process, comprising strand spools, collector plate, cross head extruder, water chill trough downstream of the hot extrusion die, a caterpillar puller device and take up spool.

[0028] FIG. 3 is a side elevation view depicting one embodiment of a terminus end fitting and a short length of rod exiting the end fitting.

DETAILED DESCRIPTION OF EMBODIMENTS

[0029] In some embodiments, a continuous sucker rod assembly can be provided, comprising of a plurality of parallel carbon fiber and epoxy composite strength elements, referred to as “strands” to create a light weight, corrosion and fatigue resistant sucker rod assembly. While carbon fiber/epoxy composite strands are uniquely suited for the sucker rod application, other high strength fibers and matrix resins can be also used in the manner described herein. The individual pultruded strands, in some embodiments, can be 2 to 3 millimeters (“mm”) in cross-section when made from carbon fiber and epoxy resin although smaller and larger diameter strands can be employed depending on the application. The number of strands bundled together can determine the strength and stiffness of the continuous sucker rod. The individual strands can be held together by encapsulating the strands in a thermoplastic polymer, such as High Density Polyethylene (“HDPE”), Polyetherimide (“PEI”), Polyphenylenesulfide (“PPS”), Polyetheretherketone (“PEEK”) or any other suitable thermoplastic polymers for down-hole use, as well known to those skilled in the art.

[0030] In some embodiments, a method to encapsulate the bundle of pultruded carbon fiber strands can comprise the steps of running the bundle of strands through a cross-head extruder to form a polymer jacket over and around the bundled strands. By this method, long lengths of bundled rod on the order of 1,000 to 12,000 feet in length can be practically encapsulated to be handle-able and coil-able.

[0031] In some embodiments, the function of the thermoplastic encapsulation can be three-fold. First, it can provide a means of holding the bundle of parallel composite strands together. Second, it can allow the composite strands to twist a small amount when the sucker rod is coiled. Third, it can provide a wear-resistant encapsulation of the strength elements when they rub against the inner wall of the oil well tubing as the surface unit moves the rod up and down to actuate the down-hole pump.

[0032] When a carbon fiber sucker rod made in this manner is coiled, the bundled high modulus strands, which are parallel when encapsulated, can progressively twist since the thermoplastic encapsulation is an unreinforced and lower modulus material. The amount of twist can be very small at any specific location along the length of the sucker rod. However, the twist over a long length of sucker rod can be significant because it progressively develops as the sucker rod is coiled. The twist can be automatically and naturally removed as the sucker rod is deployed off the spool due to the elastic properties of the encapsulation polymer. This is in contrast to a monolithic pultruded composite rod wherein the outer fibers are put in extreme tension and the inner fibers are put in extreme compression when the rod is coiled and the resin matrix is too stiff to allow twist when coiling. Additionally, there is significant inter-laminar shear stress when a monolithic composite rod is coiled. This results in significant strain energy and potential damage to the composite.

[0033] In some embodiments, a carbon fiber rod can be manufactured in the following manner. The carbon fiber/epoxy composite strands can first be pultruded. Carbon fiber and epoxy can be used in some embodiments, but other high-strength fibers such as fiberglass and matrix resins such as phenolic, vinyl ester, polyester resin, benzoxyzene, cyanurate ester, amongst others well known to those skilled in the art, can be used in combination with the fiber to make the strands. In some embodiments, the strands can be pultruded in multiple streams at lengths of 2,000 to 12,000 feet, the length dependent only on the length of the carbon fiber spool and coiled on individual spools after pultrusion. Because of the small size of the individual strands, they can be coiled on conventional cable spools as small as 18 inches in diameter when the rods are in the 2 to 3 mm diameter range.

[0034] After pultrusion, the strands can be individually unspooled and brought together into a parallel bundle using collector plates. There can be a generally round natural nesting geometry to the bundle since it is made of a plurality of parallel strands that are typically round. For example, a bundle of 37 pultruded rods (12) of 3.3 mm diameter can form sucker rod (10) having a polygon cross-section shape approximately ¾ inches round, as shown in FIG. 1A, wherein pultruded rods (12) can be encapsulated in extruded HDPE jacket (14). Other naturally generally round bundles, meeting the strength and stiffness requirements of typical oil wells, can use 14, 19 or 30 strands of pultruded rods (12) to form sucker rod (10) encapsulated in jacket (14), although other combinations can be used. FIG. 1 B shows a bundle comprising 30 pultruded rods (12) encapsulated in jacket (14) to form sucker rod (10). The bundled configuration can also be tailored to create a generally oval cross section that is more easily coiled. FIG. 1C shows an oval bundle comprising 29 pultruded rods (12) encapsulated in jacket (14) to form sucker rod (10). In some embodiments, sucker rod (10) can be formed as a bundle with a polygonal cross-section shape. As an example, FIG. 1D shows a polygonal bundle comprising 37 pultruded rods (12) encapsulated in jacket (14) to form sucker rod (10). In this example, sucker rod (10) comprises a 6-sided polygonal cross-section shape although it is obvious to those skilled in the art that sucker rod (10) can comprise a polygonal cross-section shape of any number of sides.

[0035] In some embodiments, the composite strands can be run through a cross-head screw extrusion machine die. Referring to FIG. 2, in some embodiments, a plurality of pultruded rods (12) can be drawn from spool (16) (which can include up to 37 separate 4 foot diameter spools, each containing up to 10,000 feet of 3.3 mm diameter pultruded carbon rod), and drawn through die (18). In some embodiments, die (18) can be perfectly round in cross section even though the bundle of strands may be a polygon. Thermoplastic polymers such as HDPE, PEI, PPS or PEEK can be introduced to extrusion die machine (20) in pellet form, which can be stored in pellet hopper (22) for feeding into die machine (20). In some embodiments, extrusion die machine (20) can melt and pressure the thermoplastic pellets into extrusion die machine (20) as rods (12) are pulled by traction unit (26) just downstream of extrusion die machine (20). In some embodiments, extrusion die machine (20) can be configured to form a sucker rod having a round cross-section shape, as shown in FIGS. 1A and 1B. In some embodiments, extrusion die machine (20) can be configured to form a sucker rod having an oval cross-section shape, as shown in FIG. 1C. In some embodiments, die (20) can be configured to form a sucker rod having a polygonal cross-section shape, as shown in FIG. 1D.

[0036] In other embodiments, an HDPE tube can be co-extruded and continuously drawn down onto the outside of rods (12) as HDPE tube (15) cools (as well known to those skilled in the art), wherein the drawn down HDPE tube (15) can comprise a “leather-like” outer surface once it has been drawn down onto rods (12) to form sucker rod (10), as shown in FIG. 1E.

[0037] In some embodiments, traction unit (26) can comprise a dual caterpillar tractor belt mechanism. In other embodiments, traction unit (26) can comprise reciprocating gripper pullers as used in pultrusion machines. The feed rate of thermoplastic polymer to fully encapsulate the bundle of carbon fiber strands can be proportional to the speed in which the strands are pulled through the extrusion die. Composite strands can be drawn from their respective supply spools as the product is pulled through the collector plates and the extrusion die in a continuous manner. In some embodiments, water chill bath (24) can be placed between hot extrusion die machine (20) and puller system (26) to cool finished sucker rod (10) product exiting die machine (20), to be spooled onto take up spool (28) for transport to a well site.

[0038] A short length of exposed strands (with no extruded jacket) can be left at the beginning and the end of the continuous length of sucker rod to facilitate affixing the terminus as described in U.S. Provisional Application No. 62/003,437 and U.S. Provisional Application No. 61/903,194, which are incorporated into this application by reference in their entirety. Referring to FIG. 3, as an example, sucker rod (10) can be fitted with end fitting cone (30) using the techniques as described in these applications, wherein cone (30) can further comprise wrench flats (32) and threaded coupling pin (34). Wrench flats (32) enable the use of a wrench to engage flats (32) for threading coupling pin (34) into an adjoining coupler as well known to those skilled in the art (not shown) for coupling to another length of sucker rod (10) (not shown). The resultant product can then be a continuous long length of carbon fiber sucker rod (10) on the order of 1,000 to 12,000 feet in length, or more.

[0039] While the assemblies and methods described herein can be used as a continuous composite sucker rod, one skilled in the art will immediately recognize that such assemblies and methods can be used for making any long length of composite cable that needs to be stored in a reasonable diameter without damage due to coiling.

[0040] Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications can be made to these embodiments without changing or departing from their scope, intent or functionality. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the invention is defined and limited only by the claims that follow.