WO2016115508A1

WO2016115508A1 - Molded composite centralizer

Info

Publication number: WO2016115508A1
Application number: PCT/US2016/013676
Authority: WO
Inventors: Stosch SABO; Matthew Stage
Original assignee: Weatherford Technology Holdings, Llc
Priority date: 2015-01-16
Filing date: 2016-01-15
Publication date: 2016-07-21

Abstract

The disclosure relates to a centralizer composed at least partially of a composite material, the centralizer having a matrix phase within the composite material; and a plurality of reinforcements distributed within the matrix phase, wherein the reinforcements are discontinuous. The centralizer may be a molded bow spring centralizer or a molded rigid centralizer.

Description

TITLE: Molded Composite Centralizer

BACKGROUND

[0001] Technical Field: Centralizers are used in holes and in tubulars in the petroleum and in other industries.

[0002] Bow spring centralizers must have sufficient ductility and flexibility to collapse yet sufficient strength to centralize a tubular according to the given application within a wellbore and/or casing. Commodity plastic rigid centralizers may disallow movement through restrictions. On the other hand, conventional bow spring centralizers may be expensive due to materials used. Thus there is a need for a plastic or composite molded centralizer able to withstand the side-wall, torsional, and pull-through forces during use.

BRIEF SUMMARY

[0003] The disclosure relates to a centralizer composed at least partially of a composite material, the centralizer having a matrix phase within the composite material; and a plurality of reinforcements distributed within the matrix phase, wherein the reinforcements are discontinuous. The centralizer may be a molded bow spring centralizer or a molded rigid centralizer.

BRIEF DESCRIPTION OF THE FIGURES

[0004] The exemplary embodiments may be better understood, and numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. These drawings are used to illustrate only exemplary embodiments, and are not to be considered limiting of its scope, for the disclosure may admit to other equally effective exemplary embodiments. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. [0005] Figure 1 depicts a schematic view of a well site having a drilling system with an exemplary embodiment of a molded bow spring centralizer.

[0006] Figure 2 depicts a perspective view of the exemplary embodiment of the centralizer of Figure 1 .

[0007] Figure 3 depicts a side view, slightly rotated, of an exemplary embodiment of a molded bow spring.

[0008] Figure 4 depicts an external/internal side view of the exemplary embodiment of the molded bow spring of Figure 3.

[0009] Figure 5 depicts a side view of an exemplary embodiment of the molded bow spring of Figure 3.

[0010] Figure 6 depicts a lower side view of an exemplary embodiment of the molded bow spring of Figure 3.

[0011] Figure 7 depicts a schematic external/internal side view of an exemplary embodiment illustrating the composite material of the molded bow spring.

[0012] Figure 8 depicts a side view of an exemplary embodiment of the molded bow spring having a coating.

[0013] Figure 9 depicts a perspective view of an exemplary embodiment of a molded bow spring.

[0014] Figure 10 depicts a top view of an alternate exemplary embodiment of a molded bow spring centralizer.

[0015] Figure 1 1 depicts a side view of an exemplary embodiment of a molded bow spring centralizer.

[0016] Figure 12 depicts a side view of an exemplary embodiment of a molded bow spring centralizer.

[0017] Figure 13 depicts a side view of an alternative exemplary embodiment of a molded composite rigid centralizer.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT(S)

[0018] The description that follows includes exemplary apparatus, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described exemplary embodiments may be practiced without these specific details. [0019] Figure 1 depicts a schematic view of a well site 60 having a drilling system 50. Although the depicted drilling system 50 is a terrestrial system in Figure 1 , it is to be appreciated that the disclosed embodiments may be practiced in alternate environments, including, but not limited to, offshore drilling units as well. For example, the wellbore 62 may be subsea having a wellhead located adjacent to the waterline and may have a drilling system 50 located on a platform adjacent the wellhead. Further, although wellbore 62 is depicted as a vertical wellbore, it is to be appreciated that the exemplary embodiments disclosed herein may be utilized with any cased or uncased wellbores 62, including curved, deviated and horizontal wellbores 62.

[0020] In Figure 1 , the well site 60 may have a wellbore 62 formed in the earth and may be optionally lined with a casing 64. The wellbore 62 may define an inner diameter 63, and the casing 64 may define an inner diameter 65. The drilling system 50 may include a derrick 52, pressure control devices 54, casing 64, a centralizer 10 and oilfield equipment 56. The one or more pressure control devices 54 at the well site 60 may control pressure in the wellbore 62. The pressure control devices 54 may include, but are not limited to, blow out preventers (BOPs), rotating control devices (RCDs), and the like. The pressure control device 54 is a drill-through device with a rotating seal that contacts and seals against a piece of oilfield equipment 56 for the purposes of controlling the pressure or fluid flow to the surface. The oilfield equipment 56 may be any suitable equipment to be sealed by the pressure control device 54 including, but not limited to, a tubular 70, a drill string, a bushing, a bearing, a bearing assembly, a test plug, a snubbing adaptor, a docking sleeve, a sleeve, sealing elements, a drill pipe, a tool joint, and the like. The oilfield equipment 56 or tubular 70 may define an axis or longitudinal axis 74 about which the centralizer 10 is longitudinally oriented. The centralizer 10 may have a plurality of collars or bodies 30 to which bow springs 20 are attached. The collars or bodies 30 may surround, engage, mount or couple to the outer diameter 72 of the tubular 70 or piece of oilfield equipment 56.

[0021] Figure 2 depicts a perspective view of the exemplary embodiment of the molded bow spring centralizer 10a (or centralizer 10) of Figure 1 . Figures 10-12 depict top and side views of an exemplary embodiment of a molded bow spring centralizer 10a. As depicted, the bow spring centralizer 10a has collars 30 which define a void throughbore 12 through which the tubular 70 or piece of oilfield equipment 56 may travel therethrough. The exemplary embodiment of the bow spring centralizer 10a of Figure 2 has two bodies or collars 30, a top collar 30a and a bottom collar 30b. A plurality of bow springs 20 may connect the top collar 30a and bottom collar 30b. Figures 3-6 depict perspective, top, side, and lower side views of an exemplary embodiment of a molded bow spring 20, respectively. Each bow spring 20 may have ends or end portions 22, for example a top end 22a and a bottom end 22b, to couple to the bodies 30a, 30b, and one or more arced portions 25. The ends 22 have a distance between them which may define the length 27 of the bow spring 20, as seen in Figures 3 and 5. Each arc 25 may have an apex 23, which may be located at a center point or midpoint 24 equidistant between the two ends 22 (or the middle of the length 27) of the bow spring 20. The plurality of arcs 25 and their apexes 23 may be arranged concentrically about the longitudinal or tubular axis 74 to define an outer diameter 14 of the bow spring centralizer 10a and a height (or depth) 26 of the bow springs 20. The height 26 can be seen in the view depicted in Figure 6. The outer diameter 14 and/or height 26 of the bow springs 20 may contact or engage the inner diameters 63 or 65 or the wellbore or hole 62 or casing/tubular 64, respectively, for the purpose of centralizing the piece of oilfield equipment 56 or tubular 70 within the wellbore 62 or casing 64. The outer diameter 14 and/or height 26 of the bow springs 20 may be adjusted or modified as necessary by one of ordinary skill in the art to centralize the tubular 70 or piece of oilfield equipment 56 within a particular wellbore 62 or casing 64. Additionally, as shown in Figure 2, the bow spring centralizer 10a may also include an embedded component 80. Although embedded component 80 is depicted as on or within the collar 30, the embedded component 80 may also be on a bow spring 20 of the bow spring centralizer 10a. By way of example only, the embedded component 80 may be an RFID tag. Alternatively or additionally, the embedded component 80 may be or also include, by way of example only, a piezoelectric sensor, a thermocouple, and/or a conductive network (which may be tailored for pressure measurement, temperature measurement, and/or structural-health monitoring, respectively). [0022] Each bow spring 20 may have simultaneous changing cross sectional geometry which is configured to maintain a constant or near-constant cross sectional area to maintain sufficient tensile/compressive strength during pull-through in the casing 64 or wellbore 62 and/or to withstand the various forces experienced during operation. For example, each bow spring 20 may have a variable thickness 28 and a variable width 29, which may simultaneously vary over the length 27 of the bow spring 20. Further, as can be seen in the exemplary embodiment of Figure 3 and Figure 5, the thickness 28 of bow spring 20 may vary from the ends 22 to the midpoint 24, such that the thickness 28a at an end 22 may be less than the thickness 28b at the midpoint 24. As can also be seen in the exemplary embodiment of Figure 3 and Figure 4, the width 29 of bow spring 20 may also vary from the ends 22 to the midpoint 24, such that the width 29a at an end 22 may be greater than the width 29b at the midpoint 24. In an exemplary embodiment, the bow spring 20 may have the greatest (or widest) width 29a and thinnest thickness 28a at the ends 22 (for torsional strength during rotation) and the least, narrowest width 29b and thickest or greatest thickness 28b at the midpoint 24 (for strength/stiffness against side-wall forces).

[0023] The collar or body 30 may be generally ring-like or cylindrical in shape and define a void or throughbore 12 which may attach to, mount to, couple to, engage or surround the tubular 70 or piece of oilfield equipment 56. The collar 30 may be filament wound, compression molded, transfer molded, cast, or machined from a plastic, composite, metal, elastomer, or combination thereof. In one exemplary embodiment, the collar 30 may be formed from a composite material 40 similar to that of the composite material 40 which forms the bow spring 20 and the collar 30 and the bow springs 20 may be simultaneously fabricated by injection molding into a unitary body. In alternate exemplary embodiments, the collar 30 may be constructed of any suitable material, including metal. The collar 30 may be integrally molded into a unitary construction with the molded bow springs 20. Alternatively, the bow springs 20 may attach or couple to the collar 30 in any other manner known in the art including mechanical fastening such as welding or bolting; adhesive fastening; or other techniques as known in the art. Furthermore, the bow springs 20 may be aligned with the tubular 70 or throughbore 12 (as depicted in the Figures 1 -2, and 10-12) or at an angle (or spiral) to the axial direction of the tubular 70 to facilitate rotation (akin to as depicted in Figure 13).

[0024] Figure 7 depicts a schematic top view of an exemplary embodiment of the resin, plastic or composite material 40 forming the molded bow spring 20. Figure 8 depicts a side view of an exemplary embodiment of a coating 46 of the molded bow spring 20. The composite material 40 may be, by way of example only, a discontinuously reinforced thermoplastic elastomer 41 . Further, the composite material 40 may include a matrix phase 42 and a reinforcement phase 44. The matrix phase 42 may be selected from a group including styrenic block copolymers, polyolefin blend, thermoplastic polyurethane, thermoplastic copolyester, thermoplastic polyamide, thermoset resin (such as polyester, vinylester, epoxy, phenolic, bismaleimide, polyamide, polyimide, or polyurethane), thermoplastic resin, thermoplastic elastomer, rubber compound and any suitable material. The matrix phase 42 may be continuous. The reinforcement phase 44 may be filament, fiber, tow, yarn, or roving made up of ceramic, carbon, aramid, ultra-high-molecular-weight polyethylene (UHMWPE) (or its derivatives), synthetic fiber reinforcements or mixtures thereof approximately 1/8 inch to 2 inches (or 0.3175 to 5.08 cm) in length. Examples of aramids include those sold under the trade names TWARON and KEVLAR. Examples of UHMWPE include those sold under the trade names DYNEEMA and SPECTRA. The reinforcements 44 may be arranged discontinuously within the matrix 42 of the composite material 40. Additionally, as is seen in Figure 8, the bow spring 20 may optionally include a coating 46 to decrease wear or reduce friction when in use.

[0025] Figure 9 depicts a perspective view of an exemplary embodiment of a molded bow spring 20 illustrating the multiple cross sectional areas 21 , which are defined by the thickness 28 and width 29 at a point along the length 27 of the bow spring 20. The changing cross sectional geometry may be configured to be of constant or near- constant cross sectional area 21 throughout the length 27 of the bow spring 20 by adjusting the thickness 28 and the width 29, such that, for example, the cross sectional area 21 a at the end 22 may be equivalent or nearly equivalent to the cross sectional area 21 b at the midpoint 24. The maintenance of a constant cross sectional area 21 throughout the length 27 of bow spring 20 may aid in withstanding the shear forces, and pull-through forces applied to the bow spring centralizer 10a during operations.

[0026] Side-wall forces may be created by the weight of the tubular 70 or oilfield equipment 56 pushing one or more bow springs 20 into the inner diameter 63 or 65 of the wellbore 62 or casing 64. These side-wall forces create a constant shear force or shear stress, which is dependent on the cross sectional area 21 of the bow spring 20, and independent of any width 29 versus thickness 28 ratios. The side- wall forces may also create a maximum moment force towards the midpoint 24 of the bow spring 20. In one exemplary embodiment, to reduce the maximum moment stress for a given load and material, the midpoint width 29b to midpoint thickness 28b ratio may be less than one. Thus, the center or midpoint 24 of the bow spring 20 may be thickest and narrowest to reduce or minimize stresses associated with side- wall loads, including the maximum moment force associated with the side-wall load.

[0027] Further, rotational forces result when the tubular 70 or oilfield equipment 56 is rotating and the wellbore 62 or casing 64 remains stationary. The rotational forces may also result in shear stress. The shear stress associated with the rotational force may remain constant with a constant area 21 . The moment stress is maximized where the bow spring 20 connects to the collar 30. Thus, the greater width 29a at both ends 22 of the bow spring 20 helps to reduce the stress resulting from rotational forces (as compared to the smaller width 29b of the midpoint 24). The cross sectional area 21 may remain constant throughout the length 27 to sustain the various shear forces experienced by the bow spring centralizer 10a.

[0028] Generally, the ratio of the midpoint width 29b to the midpoint thickness 28b may always be less than the ratio of the end width 29a to the end thickness 28a. In an exemplary embodiment of a bow spring 20, the end width 29a may always be greater than the end thickness 28a. In said exemplary embodiment, the midpoint width 29b may always be less than the end width 29a. Additionally, in the same exemplary embodiment, the midpoint thickness 28b may always be expected to be greater than the end thickness 28a.

[0029] The ratio of the end width 29a to the end thickness 28a may range between 1 .3:1 to 120:1 , with a currently preferred range between 2: 1 and 40:1 . The ratio of the midpoint width 29b to the midpoint thickness 28b may range between 0.125: 1 to 80: 1 , with a currently preferred range between 0.25: 1 and 40:1 . For any combination of end width 29a and end thickness 28a, and midpoint width 29b and midpoint thickness 28b, which fall within the above ranges, the ratio of midpoint width 29b to midpoint thickness 28b will be less than the ratio of end width 29a to end thickness 28a. Specific ratios for each dimension will vary depending on: material, the bow spring 20 length 27, the number of bow springs 20, tubular 70 or pipe diameter, tubular 70 or pipe weight, casing 64 or open-hole diameter, wellbore 62 temperature, wellbore 62 chemicals and/or minimum hole restriction size.

[0030] By way of example only, a 5.0 inch (or 12.7 cm) bow spring 20 may have an end thickness 28a of 0.188 inches (or 0.478 cm); an end width 29a of 4.0 inches (or 10.16 cm); a midpoint thickness 28b of 1 .0 inch (or 2.54 cm); and a midpoint width 29b of 0.5 inches (or 1 .27 cm). The arrangement of multiple bow springs 20 around the collars 30a, 30b may define an outer diameter 14 of the bow spring centralizer 10a. By way of example only, the outer diameter 14 may be 9 inches (or 22.86 cm), which may provide a 93% standoff at 520.0 lb. loading (or 2313.1 Newtons) when running in a 9.00 inch (or 22.86 cm) diameter hole with a casing 64 weight centered on a single bow spring 20. The described exemplary embodiment may also withstand a torsional load of 416.0 lb. (or 1850.5 Newtons) (assuming a coefficient of friction of 0.8, representative of mild steel on mild steel, a worst case scenario). This exemplary embodiment would meet or exceed the industry-standard requirements as listed in API 10D, in that the starting force is less than 520.0 lb. (or 2313.1 Newtons) and the restoring force of 520.0 lb. loading (or 2313.1 Newtons) generates greater than 67% standoff.

[0031] Figure 13 depicts a molded composite rigid centralizer 10b, an alternative exemplary embodiment of the molded composite centralizer 10. The rigid centralizer 10b may have a cylindrical body or pipe 90 which may be mounted to a tubular 70. Two or more straight, angled, or helical projections or fins 92 may extend radially from the cylindrical body 90. The projections 92 may be mounted, coupled or unitarily formed with the cylindrical body 90. Other means of connecting the projections 92 to the cylindrical body 90 are possible, as may be known to one of ordinary skill in the art. The cylindrical body 90 and/or the projections 92 may be constructed out of a resin, plastic or composite material 40, which may be a discontinuously reinforced thermoplastic elastomer 41 that includes a matrix phase 42 and a reinforcement phase 44 as similarly described previously for the bow spring centralizer 10a.

[0032] The composite material 40 for the rigid centralizer 10b may also include a coating 46 which reduces wear or friction (not illustrated in Figure 13). Additionally, the rigid centralizer 10b may also include an embedded component 80. By way of example only, the embedded component 80 may be an RFID tag. Alternatively or additionally, the embedded component 80 may be or also include, by way of example only, a piezoelectric sensor, a thermocouple, or a conductive network (which may be tailored for pressure measurement, temperature measurement, and/or structural-health monitoring, respectively).

[0033] The bow spring centralizer 10a and the rigid centralizer 10b may be constructed by compression, transfer or injection molding into a single-cavity or multi-cavity mold. Parts of the centralizers 10, such as the bow springs 20, the collar 30, the cylindrical body 90 and/or the projections 92, may also be constructed by compression, transfer or injection molding into a mold (which may also be a single- cavity or multi-cavity mold) and subsequently assembled together by means known in the art. The embedded component 80 may be embedded into the desired mold during the molding process.

[0034] The proposed materials for the matrix phase 42 and the reinforcement phase 44 may create the advantage of tailorable properties such as: strength, modulus, weight, impact resistance, wear resistance, chemical resistance, corrosion resistance, temperature resistance, and friction coefficient as a result of the variety of thermoset, thermoplastic, and fiber options available (such as the resin type, fiber type, fiber weight percentage, fiber length and aspect ratio, and molding methodology).

[0035] While the exemplary embodiments are described with reference to various implementations and exploitations, it will be understood that these exemplary embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. By way of example only, it is to be appreciated that not all the bow springs 20 or projections 92 of the centralizers 10 may necessarily be formed with the composite material 40. For example, a centralizer 10 may have several bow springs 20 or projections 92 which may be at least partially made of composite 40, and several bow springs or projections which may be more conventional, such as those made from entirely non-composite materials. Further, the width 29 and thickness 28 throughout the length 27 of the bow spring 20, as well as the length 27 and shape of the bow spring 20, may be varied as optimal for the situation desired by the operator of the drilling system 50. Additionally, the disclosed shape of the bow spring 20 (including, for example, the exemplary ratios of thicknesses 28 and/or widths 29 for the ends 22 and/or midpoint 24) may be adaptable for manufacture from a number of different materials, including, but not limited to steel, aluminum, other metals or alloys, and other composites or plastics, in addition to the disclosed composite material 40. Many variations, modifications, additions and improvements are possible.

[0036] Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.

Claims

CLAIMS:

1 . A centrahzer apparatus composed at least partially of a composite material, comprising

a matrix phase within the composite material; and

a plurality of reinforcements distributed within the matrix phase,

wherein the reinforcements are discontinuous.

2. The centrahzer apparatus of claim 1 , wherein the matrix phase is selected from the group consisting of styrenic block copolymers, polyolefin blend, thermoplastic polyurethane, thermoplastic copolyester, thermoplastic polyamide, thermoset resin, thermoplastic resin, thermoplastic elastomer, and rubber compound.

3. The centrahzer apparatus of claim 2, wherein the plurality of reinforcements are selected from the group consisting of ceramic, carbon, aramid, ultra-high- molecular-weight polyethylene, ultra-high-molecular-weight polyethylene derivatives, and synthetic fiber reinforcements.

4. The centrahzer apparatus of claim 3, wherein the plurality of the

reinforcements have a length between 0.3175 cm to 5.08 cm.

5. The centrahzer apparatus of claim 4, further comprising

a bow spring composed of the composite material; and

a collar attached to an end of the bow spring.

6. The centrahzer apparatus of claim 5, wherein the bow spring has a thickness and a width, wherein the thickness and the width are variable between the end of bow spring and a midpoint of the bow spring.

7. The centrahzer apparatus of claim 6, wherein a thickness at the midpoint is greater than a thickness at the end.

8. The centrahzer apparatus of claim 7, wherein a width is at the end is greater than a width at the midpoint.

9. The centrahzer apparatus of claim 8, wherein the width at the end is greater than the thickness at the end.

10. The centrahzer apparatus of claim 3, further comprising a coating on the bow spring.

1 1 . The centrahzer apparatus of claim 5, wherein the collar and the bow spring are unitary.

12. The centralizer apparatus of claim 3, wherein the centralizer apparatus is rigid.

13. The centralizer apparatus of claim 4, further comprising

a body, wherein the body is cylindrical; and

a projection connected to and extending radially away from the body.

14. An apparatus for centralizing a piece of oilfield equipment in a wellbore

comprising

a collar surrounding the piece of oilfield equipment; and

a bow spring constructed of a composite material and attached at an end to the collar, wherein the composite material comprises a matrix phase and a plurality of reinforcements within the matrix phase, and further wherein the reinforcements are discontinuous.

15. The apparatus according to claim 14, wherein the bow spring comprises a thickness, wherein the thickness is variable along a length of the bow spring and a width, wherein the width is variable along the length of the bow spring.

16. The apparatus according to claim 15, wherein the thickness is greatest at a midpoint of the bow spring, and wherein the width is greatest at the end of the bow spring.

17. The apparatus according to claim 16, further comprising a cross sectional area of the bow spring defined by the thickness and the width and wherein the cross sectional area is constant across the length of the bow spring.

18. A bow spring apparatus having a length defined between two ends of the bow spring, and further having a midpoint, comprising

a thickness, wherein the thickness is variable along the length of the bow spring;

a width, wherein the width is variable along the length of the bow

spring; and

wherein a width at the end is greater than a thickness at the end;

wherein a width at the midpoint is less than the width at the end; and further wherein a thickness at the midpoint is greater than the thickness at the end.

19. A method for centralizing a tubular within a wellbore, comprising the steps of: mounting a centralizer having a plurality of bow springs around the tubular; and

centralizing the tubular with the plurality of bow springs, wherein the bow springs comprise a composite material, and further wherein the composite material comprises a matrix phase and a plurality of reinforcements within the matrix phase, and further wherein the reinforcements are discontinuous.

20. The method according to claim 19, further comprising the step of reducing friction with a coating on the bow spring.

21 . The method according to claim 20, further comprising the step of minimizing a side-wall load with the bow springs , wherein the bow springs have a thickness greatest at a midpoint of the bow springs.

22. The method according to claim 21 , further comprising the step of minimizing a rotational force with the bow springs, wherein the bow springs have a width greatest at an end of the bow springs.

23. A method of making a bow spring for a centralizer, comprising the steps of:

injecting a composite material into a mold, wherein the composite

material comprises a matrix phase and a plurality of

reinforcements within the matrix phase, and further wherein the reinforcements are discontinuous, and wherein the mold defines a bow spring; and

removing the bow spring from the mold.

24. The method of claim 23, further comprising the step of coating the bow spring with a friction reducing coating.

25. The method of claim 24, further comprising the step of embedding an

embedded component within the mold.