CN1304355A - Composite pipe structure heaving improved containment and axial strength - Google Patents

Abstract

A laminated composite fiber reinforced plastic pipe having high resistance to microcracking and delamination is disclosed. The tube wall structure of the tube comprises a multilayer laminate of an outer axial load-bearing layer and an inner layer in contact with its inner surface; wherein the outer axial load-bearing layer comprises a Reinforced continuous fibers with a wrap angle of 0° to +/- 30°; the inner layer contains reinforced continuous fibers embedded in a thermosetting resin binder at a wrap angle greater than +/- 30° with the longitudinal tube axis.

Description

Composite tube construction with high sealing and axial strength

technical background

The technical field of the present invention

This invention relates to pipes and tubing having fiber reinforced polymer composite laminated wall structures.

Related Technical Notes

The application of fiber reinforced plastic pipe (FRP pipe) in the piping system of chemical plants and as the casing for oil and gas well drilling and the casing and pipe for transporting crude oil and natural gas from downhole to the surface is growing.

For applications in the oil/gas field, FRP pipes are superior to carbon steel pipes in that they have excellent corrosion resistance, flexibility to meet the design requirements of mechanical properties, and good fatigue resistance. In addition, FRP pipes are much lighter than corresponding steel pipes for a given wall thickness.

The general preparation process of FRP pipes for high-pressure pipeline systems or casings (such as crude oil pipelines and oil well tubing) includes: impregnating filament rovings of high-strength materials (such as continuous glass filaments) with thermosetting resin compositions (such as epoxy resins) Resin), and then under a certain winding tension, the impregnated filament is wound back and forth on the mandrel to form a multi-layer interwoven filament winding tube blank. The filaments can be wound at an angle of 90° to the tube axis or at an angle of 0° plus or minus about 90° (+/−90°) to the tube axis. When the winding angle with respect to the longitudinal tube axis is between 0° and 90°, a helical filament winding pattern is formed. After reaching a predetermined wall thickness, the winding operation is stopped, the resin is allowed to cure, and the mandrel is withdrawn to form a cylindrical pipe with a fiber-reinforced wall structure. Such FRP pipes and methods of manufacture are disclosed, for example, in US Patent Nos. 2,843,153 and 5,330,807, the entire disclosures of which are incorporated herein by reference.

The construction of FRP pipes for onshore or offshore mineral fuel extraction must withstand the two fundamental forces to which they will be subjected, the first being the fluid (oil or drilling mud) transported through the pipeline at medium to high pressure ) The outer radial load applied in the direction perpendicular to the pipe wall, also known as the hoop load. The second type of force is the axial tensile load applied in a direction parallel to the pipe axis, and is generated by fluid pressure and/or the weight of the long pipe string suspended above the wellbore surface and/or connected between the wellbore and the offshore production operation platform force along the direction parallel to the tube axis. These pipe strings are often overhead 3000-10000 feet (about 850-2800 meters), therefore, the FRP pipe must be able to withstand more than about 2500 lbs. ² , (or 2.5Ksi) long-term axial stress.

FRP pipes with maximum hoop strength can be produced if the reinforcing fibers are wound at a wrap angle close to 90° (eg +/- 70° to 90°) to the pipe axis. Conversely, a tube with maximum tensile strength can be produced if the reinforcing fibers are wound at a wrap angle close to 0° (eg +/- 30° to 0°) to the tube axis. However, the axial tensile strength of the pipe wound at or near 90° is greatly reduced, and the hoop strength of the pipe wound at or near 0° is greatly reduced. Tubes wound at moderate wrap angles of +/-30° to +/-70° to the tube axis (as disclosed in US Patent 2,843,153) generally provide a compromise between hoop strength and especially axial strength, but their The strength may be difficult to meet the strength requirements for practical applications in fossil fuel mining operations.

A technique aimed at maximizing both hoop and axial strength is to lay down reinforced fiber composites in separate laminated layers, one on top of the other, with the fibers in each layer arranged at different angles to the tube axes In order to maximize the pipe's ability to withstand hoop stress and axial stress, and to minimize the expansion coefficient of the composite pipe. An example of such a construction comprising +/- 20° to +/- 60° fibrous layers alternating with 90° layers is disclosed in US Pat. No. 5,330,807. Other similar layered laminates are disclosed in US Patents 4,728,224 and 4,385,644.

Such laminates comprising multiple layers, such as 3-9 individual layers, are usually designed to optimize hoop or axial stiffness and thus do not need to take advantage of the anisotropic properties of unidirectional fiber composites. For example, alternating plies at 0 and +/-70 degrees does not take advantage of the maximum hoop strength of the +/-70 degree ply or the maximum axial strength of the 0 degree ply.

Furthermore, currently commercially available composite materials suffer from serious disadvantages that make their application cost-effective and even moderate tube stresses. Microcracks and delamination of the pipe wall structure at or near the pipe joint and/or along the length of the pipe wall can provide a path for the leakage of fluid. Occurs when the pressure is less than 1/5-1/10 of the rapid burst pressure of the pipe. Water entering the pipe wall structure through these microcracks can attack the fiberglass surface and/or the binder resin, causing delamination and premature failure of the pipe.

While increasing the wall thickness can alleviate the problem of microcracking, this solution increases the cost of composite pipe and tubing as high as carbon steel pipe. Higher costs have been an obstacle to replacing carbon steel used at medium to high pressure (injection) with composite pipe and tubing. Similarly, for downhole applications, after the pipe wall is thickened, the effective cross section of fluid flow is smaller than that of carbon steel, and the diameter of the wellbore is limited. Therefore, the thickening of the pipe wall will affect the application of composite materials in the field of oil recovery. When this composite material is used in these fields, it is required to drill a larger diameter wellbore, thus increasing the additional drilling cost.

Increased wall thickness is not likely to significantly increase the axial strength of composite tubing, which limits the application of composites to downhole tubing, casing, and injection tubing into oil and gas wells to depths up to about 5,000 ft.

Therefore, the main purpose of the present invention is to provide a layered composite FRP pipeline system with qualified hoop strength and axial strength. This pipeline system has good micro-crack resistance and delamination resistance on the one hand, and another On the one hand, the thickness of the pipe wall is reduced, so it can be consistent with the carbon steel wellbore/casing size.

Summary of the invention

The present invention provides a fiber-reinforced plastic pipe having a hollow tubular body with a multi-layer pipe wall structure, and the fibers contained in each layer may be the same or different, and the fibers are consolidated with a resin adhesive and are aligned with the longitudinal direction of the pipe. The axis is oriented at a certain angle; the fiber-reinforced plastic tube includes: an outer axial bearing layer containing a plurality of first fibers and a first layer containing a plurality of second fibers radially arranged on the inner side of the outer layer and contacted and consolidated with the outer layer Two layers, wherein the first fibers have a thickness (diameter) of about 1 micron to less than 14 microns and are aligned at an angle from 0° to about +/-30° to the tube axis; the second fibers have a thickness (diameter) of From about 1 micron to about 24 microns and aligned at an angle greater than +/- 30° to the tube axis.

When the pipe is designed to be molded or cut into a male threaded joint on the outer wall surface of one or both ends of the pipe, the molded or cut threads go deep into/on the axial load-bearing layer of the pipe so that the layer Withstands almost all axial stresses generated by machinery during mining of fossil fuels. This reduces the mismatch of shear and axial strain between the axial load-bearing layer and the adjacent layer used to maximize the hoop strength of the pipe.

Brief description of the drawings

Figure 1 is a partial front view of a composite tube member of the present invention.

Figures 2 and 3 are cross-sectional views of two different commercially available composite tube wall sections having multilayer structures with different fiber orientations.

Figure 4 is a cross-sectional view of a pipe wall portion of a two-layer composite in which the fiber orientation in each layer is oriented in accordance with the present invention.

Detailed Description of the Invention

Referring to the drawings, Figure 1 illustrates a partial cross-sectional front view of a male threaded end of a pipe manufactured in accordance with one embodiment of the present invention. As shown, the composite pipe is constructed of a three-ply fiber reinforced polymer layer laminate as shown in 2, 3 and 4 respectively and optionally a fourth barrier or envelope layer as shown in 5 Elongated hollow pipe body 1; the pipe end part shown in 6 is a male thread tapered connection part formed by cutting or molding the outer reinforcement layer 4; the spiral pattern shown in 2 and 3 and the spiral pattern shown in 4 The horizontal line pattern shown depicts how the reinforcing fibers are wound, but does not indicate the fiber winding density. The fibers, referred to herein as filaments, may be bundled, coiled or twisted together prior to making the tube.

Layer 4 in Figure 1 is the axial load-bearing layer of the pipe and is designed to carry the load when many pipe sections are combined in a line and configured either horizontally (i.e. above or below ground) or vertically (i.e. under water and/or into In the wellbore) almost all the axial loads acting on the pipe. Axial loads are transmitted along layer 4 via two female nipples or connecting pipes (not shown) which are used to connect the male threads of the two pipe ends to be connected in the construction of the pipeline. The male threaded cone and cutting part 6 penetrates deep into the axial load-bearing layer 4, but preferably does not reach the lower layer 3.

The thickness of the fibers in the adhesive layer 4 is from about 1 micron to less than 14 microns and at an angle (e.g. 0° to +/- 30°, more preferably up to about +/- 15° and most A configuration of about 0°) is preferred to allow the layer to achieve maximum axial tension load-carrying properties. The fibers shown at 4 in Figure 1 are arranged at a 0° angle to the tube axis, but it is known that this angle can vary up to +/-30°. The preferred thickness of the fibers of this layer is from about 1 micron to about 10 microns, with 7 microns being particularly preferred.

Layer 3 shown in FIG. 1 is the hoop bearing layer of the pipe comprising a second layer consolidated in contact with layer 4 and arranged radially inside layer 4 . The reinforcing fibers in layer 3 are arranged at a wrap angle greater than +/- 30°, more preferably greater than +/- 40° up to 90° to the longitudinal tube axis. If layer 3 is the only hoop load-bearing layer, the fiber is preferably wound in a configuration with a winding angle of at least +/-55°, more preferably about +/-70°, from the tube axis. The thickness of the reinforcing fibers in layer 3 is from about 1 micron to about 24 microns, preferably from about 10 microns to about 16 microns.

The layer 3 shown in Figure 1 may be the only hoop-bearing layer, or the hoop stress may also pass through an optional layer or layers, an additional layer arranged radially inside the layer 3 and consolidated in contact with it, such as a layer 2 to adjust. The preferred arrangement of the reinforcing fibers in layer 2 is such that the winding angle to the longitudinal tube axis is greater than the angle between the fibers in layer 3 and the longitudinal axis of the tube, up to 90°. The most preferred wrap angle of the fibers in layer 2 is at least +/-60[deg.] to the tube axis. The fibers of each hoop stress layer may be the same or different, and the thickness of the fibers is from about 1 micron to about 24 microns, preferably from about 10 microns to about 16 microns.

In a preferred embodiment of the present invention, wherein the pipe comprises three layers of composite reinforcement, the winding angle configurations of the fibers in each layer and the longitudinal tube axis are respectively: the fiber in layer 4 is about 0°, and the fiber in layer 3 is about 0°. +/-40° to +/-60°, and preferably about +/-55°, fibers in layer 2 are greater than +/-60°, preferably about +/-70°.

Layer 5 shown in Figure 1 is an optional layer which can be used as a protective layer or as a fiber reinforced wrapping layer to ensure that the fibers in layer 4 are firmly bonded to the resin binder. Layer 5 is not used as an axial load bearing layer, and the pipe end portion of layer 5 is cut away before forming tapered male nipple 6 .

The composite laminated tube of the present invention can be made by the well known wet-laid filament winding process such as disclosed in the aforementioned US Patent 2,843,153. According to this method, a continuous tow of reinforcing filaments is impregnated with a liquid resin material, preferably an uncured thermosetting resin, and wound under tension onto a rotating mandrel by a shuttle carriage moving laterally back and forth. Or the rotating mandrel itself can move back and forth and the carriage can be in a fixed position.

The impregnated fiber bundles are wound on the mandrel in a crossed (helical) pattern next to each other or adjacent to each other, and layered one on top of the other until the desired layer thickness is achieved. The angle at which the fiber is wound to the longitudinal mandrel can be controlled over a wide range as a function of the lateral speed at which the carriage moves the mandrel. After the first layer has reached the desired thickness (layer 2 in Figure 1), the winding process is adjusted to lay down a second layer of resin-impregnated fibers (layer 3 in Figure 1) at a different winding angle than layer 2, etc. It is also possible to lay down the axial load-bearing layer 4 using filament winding technology, but with a winding angle of 0° to the fiber mandrel. For the latter, resin-saturated prepreg tapes or sleeves, which can be laid up by hand, are also suitable as axial load-bearing layers of the required thickness. Alternatively, a longitudinal lay-up method is used in which the fibers at 0° are laid on top of the mandrel top layer 3 and secured by a 90° overwrap (as shown at 5 in FIG. 1 ).

The resinous material used as a binder for reinforcing fibers is preferably a thermosetting resin such as epoxy resin. Preferred epoxy resins for the practice of this invention include bisphenol A diglycidyl ester, bisphenol glycidyl ether, novolac glycidyl ether, and aliphatic polyepoxides, although other suitable epoxy resins may also be used. resin. In addition to epoxies, other suitable thermosetting polymers include phenolic resins, unsaturated polyesters, and polyimides. The degree of polycondensation of these resins is chosen such that the viscosity of the resin product is suitable for the operating conditions required to form the pipe body. Thermosetting polymers can be used with suitable hardeners such as aromatic polyamines, polyamides, aliphatic polyamines, polybasic acids, polybasic anhydrides, dicyandiamide, primary or secondary amines, mixtures of these hardeners, or commonly used as thermosetting resins. Any other hardener for the binder.

The amount of resin coated on the fibers of the formed pipe body should be such that the volume fraction of the fibers in the cured product is at least about 40%, more preferably about 50-70%, and even more preferably about 55-65%, with the remainder being epoxy resin composition.

The reinforcing fibers, filaments, bundles or bundles of filaments may comprise continuous glass filaments, graphite filaments, aramid or ^Kevlar® fibers (poly-paraphenylene terephthalamide fibers) filaments or these long A mixture of filaments, these reinforcing fibers have extremely high tensile strength. The thickness (diameter) of the filaments used in the axial load bearing layer is from about 1 micron to less than 14 microns, with about 1 micron to about 10 microns being preferred, and 7 microns being particularly preferred. The thickness of the filaments used in the hoop support layer is from about 1 micron to about 24 microns, with about 10 microns to about 16 microns being preferred. The glass fibers may preferably be coated with a material such as aminopolysiloxane which improves the wettability and adhesion of the fiber surface to the resin binder.

After the resin-wetted composite tube is combined on the mandrel, the combined structure is heated to a temperature sufficient to cure the resin, such as 100°-170°C, and the resin is cured for about 30 minutes to 12 hours. After curing, the combined structure Remove the mandrel.

Referring again to Figure 1, the thicker axial load-bearing layer 4 should be able to adequately carry the axial load (eg at least 20 ksi) acting on the pipe during the expected long-term use. Typically, the axial load bearing layer thickness should be 50% or less of the tube wall thickness, most preferably from about 20% up to 50% of the tube wall thickness.

The remainder of the pipe wall comprises the hoop bearing layer 3 or layer 3 and layer 2 . The hoop load-bearing layers are capable of sustaining long-term hoop stresses in excess of about 15 ksi, and the preferred configuration of the layers is such that the layers are also capable of carrying a minimum axial stress of about 4 ksi.

FRP pipes made according to the present invention can have an outside diameter of about 2-36 inches and are typically used in oil/gas production and transportation. Tubing for downhole applications can be divided into two categories: tubing, with an outside diameter of 4.5 inches (nominal) and less; and casing, with an outside diameter of greater than 4.5 inches (nominal).

As described above, FRP pipes constructed in accordance with the present invention provide a mode of separately controlling axial stress and hoop stress along the pipe wall section, which can increase the hoop strength and axial strength while reducing the pipe wall thickness. Increased up to 100%.

For example, Figure 2 shows a section of a commercially available pipe rated at 2000 psig, with an outside radius of 1.37 inches, an inside radius of 0.97 inches, and a wall thickness of 0.4 inches. The tube wall is composed of five layers of glass fiber wound at +/-70° from the inner wall to the outer wall alternately laminated with four thinner layers of glass fiber wound at 0°.

Figure 4 shows a cross-section of a similar tube made in accordance with the present invention, but with a wall thickness of only 0.25 inches and only a single +/- 70° would angle from the inner wall to the outer wall, with a thickness of 0.15 inches of glass Fiber plies and a single axial load-bearing ply containing glass fibers with a 0° wrap angle and a thickness of 0.10 inches. The volume fraction of fibers in each case was about 60%.

The tensile stress and hoop stress evaluations of each pipe structure were compared, and the results showed that the hoop strength and axial strength of the pipe structure in Fig. 4 were about 60% and about 70% higher than those of the commercially available pipe structure in Fig. 2, respectively. This means that not only is this tubing 60-70% more cost-effective, but it can drill wells about 60-70% deeper than the 5,000 feet currently available with commercially available tubing.

Another advantage provided by the piping system manufactured in accordance with the present invention is the reduction of the axial strain mismatch between the layers, since the primary layer carrying the axial stress is a single outer layer. When the applied axial load is a shear load acting on both sides of the pipe wall, axial strain (deformation) occurs. Axial strain over the entire pipe wall cross-section can, over time, lead to delamination and micro-cracking of the pipe wall, resulting in what is known as leakage and premature failure of the pipe.

Figures 2 and 3 illustrate the construction of two commercially available axial strain mismatched multi-layer pipes and also illustrate the axial loads applied to the pipes through the pipe joints (schematically indicated). The figure clearly illustrates the strains on the outer layers carrying the directional tensile load and the additional strains at the interfaces of the layers.

Figure 4 illustrates the reduced axial strain mismatch for the tube design of the present invention, where almost all axial loads are supported by the 0° outer layer.

The present invention will be further illustrated with the following non-limiting examples.

Example 1

The hoop and axial stresses of composite pipes made according to methods known in the art are calculated on the basis that the outer layer is made of commercially available fibers with a diameter of 14 microns, with a resin binder at 0° The fiber-reinforced tube formed by winding an angular arrangement is carried out with a volume fraction of fibers in the outer layer of about 60%. The inner layer in contact with the outer layer is made of the same fibers as the outer layer, the volume fraction of the inner layer fibers in the resin binder is 60%, and the fiber wrapping angle is +/-70°.

When such pipe is used in an oil production facility for a long period of time (10-30 years), it is subjected to an external pressure averaging about 2000 psi and a tensile load averaging 21000 psi. Thus, the outer layer of such pipe must withstand a hoop stress of 2.6 ksi and an average axial stress of about 21.8 ksi, and the inner layer must withstand a hoop stress of 15 ksi and an average axial stress of 4.9 ksi.

The results of the calculations are shown in Table 1 and show that the layers formed by conventional fibers with a diameter of 14 microns arranged at an angle of 0° are not strong enough to withstand long-term use.

Table 1 The actual axis actual axial stress stress stress (KSI) (KSI) (KSI) outer layer of the actual axial stress stress stress stress (KSI) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI) (KSI) outer layer 15 20 4.9 5

The data in the above table shows that the calculated long-term hoop strength of the 0° layer is 2ksi, which cannot meet the required 2.6ksi during use. It is not feasible to increase the hoop strength by increasing the fiber volume fraction, because the increase of the volume fraction will form an undesirably large void volume. Furthermore, it is not feasible to increase the hoop strength by increasing the total amount of fibers and thereby increasing the thickness of the outer layer, because the additional fiber will increase the material cost, and the additional thickness will increase the manufacturing, transportation and equipment costs.

Example 2

The hoop stress and axial stress of the composite pipe of the present invention are calculated. As in Example 1, the 0° outer fiber layer is in contact with the +/- 70° inner fiber layer, both layers contain a resinous binder with a fiber volume fraction of 60% in the adhesive layer. However, according to the invention, the fiber diameter of the outer fibrous layer is 7 microns. The calculated strength data are listed in Table 2.

Table 2

Required Circumference Actual Circumference Required Axial Actual Axial

Stress Stress Stress Stress Stress

(ksi) (ksi) (ksi) (ksi) outer layer 2.6 2.8 21.8 ＞60

Claims (10)

1. A kind of elongated, hollow tube-shaped, concentric with the longitudinal axis, composed of at least two layers of fiber layers arranged at a certain angle to the longitudinal axis of the tube and consolidated with a resin adhesive. A fiber-reinforced plastic pipe, the fiber-reinforced plastic pipe comprising: an outer layer containing a plurality of first fibers and a second layer containing a plurality of second fibers radially arranged inside and adjacent to the outer layer, wherein the first fibers The thickness of the second fiber is about 1 micron to less than 14 microns and is aligned at an angle of 0° to about +/-30°; the thickness of the second fiber is about 1 micron to about 24 microns and is aligned at an angle of greater than +/-30° . 2. The tube of claim 1, wherein the first fibers are aligned at an angle of less than about +/- 15° to said longitudinal tube axis, and the fibers have a thickness of from about 1 micron to about 10 microns. 3. The tube of claim 1, wherein the first fibers are aligned at an angle of about 0° to said longitudinal tube axis and the fibers have a thickness of 7 microns. 4. The pipe of claim 1 wherein said axial load bearing layer is 50% or less of said pipe wall thickness. 5. The tube of claim 1, wherein the second fibers are aligned at an angle greater than about +/- 40° up to 90° from said longitudinal tube axis, the fibers having a thickness of from about 10 microns to about 16 microns. 6. 5. The tube of claim 5, wherein the second fibers are aligned at an angle greater than about +/- 55° from said longitudinal tube axis. 7. The tube of claim 1 further comprising a third layer disposed radially inwardly of the second layer and bonded in contact with said second layer, wherein the third fibers have a wrap angle greater than the wrap angle of said second fibers, Up to 90°, the thickness of the third fibers is from about 1 to about 24 microns. 8. The tube of claim 7, wherein the second fibers are aligned at an angle greater than about +/-40° up to about +/-60° from said longitudinal tube axis, and the third fibers are aligned at an angle greater than about +/-60° from said longitudinal tube axis. Arranged at an angle of about +/- 60° up to 90°. 9. The pipe of claim 1, wherein said resin binder is a thermosetting resin. 10. The pipe of claim 1, wherein said thermosetting resin is an epoxy resin.