Flexible composite pipe for gathering and transportation in oil field, composite pipe joint and connecting method

Abstract

The invention belongs to the technical field of non-metal flexible composite pipes for oil and gas fields, and particularly relates to a flexible composite pipe for gathering and transportation in an oil field, a composite pipe joint and a connecting method. A flexible composite pipe for gathering and transportation in an oil field comprises a lining blocking layer, a heating function layer, a heat preservation function layer and an outer protection layer which are sequentially connected from inside to outside, the heating function layer comprises a flexible wide heat supply belt, a copper foil belt is arranged in the flexible wide heat supply belt, and a conductive nanometer coating is arranged on the outer surface of the copper foil belt. The flexible wide heat supply belt is spirally wound on the outer side of the lining barrier layer, the heat preservation function layer is of a sandwich structure and comprises an aerogel heat preservation belt, polyethylene films are arranged on the inner side and the outer side of the aerogel heat preservation belt respectively, and the outer protection layer is of a polyethylene multi-layer structure and comprises an outer protection layer innermost layer, an outer protection layer middle layer and an outer protection layer outermost layer. By means of the flexible wide heat supply belt and the aerogel heat preservation belt, heat preservation and heating integrated application of the flexible composite pipe for oil field gathering and transportation is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-metal flexible composite pipes for oil and gas fields, and particularly relates to a flexible composite pipe for oilfield gathering and transportation, a composite pipe joint and a connection method. Background Art

[0002] In recent years, as the main oil reservoirs enter the middle and late stages of development, the water cut of oilfield produced fluids has been increasing year by year, and the corrosion and aging of some gathering and transportation oil and produced water pipelines have become increasingly serious, bringing serious safety and environmental hazards. The flexible composite pipe for gathering and transportation oil has become an important solution for anti-corrosion and heat preservation of oilfield surface pipelines due to its advantages such as low thermal conductivity, corrosion resistance, anti-scaling and anti-waxing.

[0003] Since the existing flexible high-pressure composite transportation pipe for gathering and transportation oil did not consider the heat preservation and heating structure at the beginning of its design, when transporting the medium, the temperature drop along the composite pipe is large, the heat loss is high, and the fuel loss is much. The pipeline is prone to wax deposition, and in severe cases, it even blocks the transportation pipeline, causing economic losses and safety accidents. At present, most of the non-metal flexible composite pipes in oilfields are connected by crimped joints or internal expansion and external sleeve joints. The through-diameter at the connection of the pipe materials is difficult to reach 100%, and the joints are large in volume and poor in sealing performance, which is not convenient for mobile use and makes the on-site installation efficiency low. Moreover, some crimped joints or internal expansion and external sleeve joints use metal joints, and their thermal conductivity is generally in the range of 10-30 W / (m•K), which is dozens or even hundreds of times the thermal conductivity of the polymer materials of each layer of the flexible composite pipe, seriously affecting the overall heat preservation effect of the gathering and transportation pipeline. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a flexible composite pipe for oilfield gathering and transportation, a composite pipe joint and a connection method. By setting a flexible wide-width heating belt and an aerogel heat preservation belt in the flexible composite pipe, an integrated design of heat preservation and heating for the flexible composite pipe for oilfield gathering and transportation is realized, meeting the actual needs of the oilfield for the multi-functional integration of self-heating and heat preservation of the flexible composite pipe for gathering and transportation oil; and by using a non-metal through-diameter joint to replace the existing metal joint, complete through-diameter is achieved, which is convenient for the oilfield to perform pigging operations, and greatly reduces the heat loss at the connection of the existing joints. Moreover, this joint is made of all non-metal materials, is light in weight, makes the on-site construction tools more lightweight, is quick to assemble, and is convenient for on-site workers to operate.

[0005] The technical solution of the present invention lies in: a flexible composite pipe for oilfield gathering and transportation, which includes an inner lining barrier layer, a heating functional layer, a heat preservation functional layer, and an outer protective layer connected in sequence from the inside to the outside. The heating functional layer includes a flexible wide-width heating belt. A copper foil strip is provided inside the flexible wide-width heating belt, and a conductive nano-coating is provided on the outer surface of the copper foil strip. The flexible wide-width heating belt is spirally wound outside the inner lining barrier layer. The heat preservation functional layer is a sandwich structure, including an aerogel heat preservation belt, and polyethylene films are respectively provided on both the inner and outer sides of the aerogel heat preservation belt. The outer protective layer is a polyethylene multi-layer structure, including the innermost layer of the outer protective layer, the middle layer of the outer protective layer, and the outermost layer of the outer protective layer. The thickness of the outermost layer of the outer protective layer is greater than the thicknesses of the innermost layer of the outer protective layer and the middle layer of the outer protective layer.

[0006] An enhanced functional layer is provided between the aerogel heat preservation belt and the outer protective layer. The enhanced functional layer includes multiple fiber resin belts, and the fiber resin belts are spirally wound outside the aerogel heat preservation belt.

[0007] The inner lining barrier layer is extruded and formed by polyethylene pellets through a single-screw extruder, and its thickness is 35% - 42% of the overall wall thickness of the flexible composite pipe. The polyethylene pellets include LLDPE, antioxidant 1076, co-antioxidant DLTP, and anti-aging agent H. By weight percentage: LDPE: antioxidant 1076: co-antioxidant DLTP: anti-aging agent H = 99: 0.15: 0.15: 0.7.

[0008] The thickness of the flexible wide-width heating belt is 2 - 3 mm, the width is 75 - 80 mm, the winding angle is 15 - 35°, the thickness of the polyethylene film is 0.02 - 0.05 mm, the thickness of the heat preservation functional layer is 2 - 3 mm, the width is 80 - 150 mm, the thermal conductivity is 0.018 W / (m･K), and the winding angle is 15 - 20°.

[0009] The fiber resin belt is prepared from 65% polyester fiber and 35% polyethylene. The thickness of the fiber resin belt is 2 - 3 mm, the width is 65 - 70 mm, and the winding angle is 54.7°.

[0010] The thicknesses of the innermost layer of the outer protective layer and the middle layer of the outer protective layer are 1 mm, and the thickness of the outermost layer of the outer protective layer is 2 mm. The colors of the innermost layer of the outer protective layer, the middle layer of the outer protective layer, and the outermost layer of the outer protective layer are different, which are red, yellow, and black respectively.

[0011] A flexible composite pipe joint for oilfield gathering and transportation, which is used to connect a flexible composite pipe for oilfield gathering and transportation as described above, includes a non-metallic joint inner sleeve. The non-metallic joint inner sleeve contains a heating wire, the heating wire is in a spiral shape, straight threads are provided on the inner side wall of the non-metallic joint inner sleeve, and a glass fiber reinforced layer is provided on the outside of the non-metallic joint inner sleeve.

[0012] The glass fiber reinforced layer is formed by wet pre-impregnating epoxy resin with glass fiber and reciprocally spirally winding. The thickness of the glass fiber reinforced layer is the same as that of the non-metallic joint inner sleeve. The length of the glass fiber reinforced layer and the non-metallic joint inner sleeve is twice the inner diameter of the inner lining barrier layer, and the thickness of the non-metallic joint inner sleeve is twice the thickness of the inner lining barrier layer.

[0013] A connection method for a flexible composite pipe used in oilfield gathering and transportation, using a flexible composite pipe joint for oilfield gathering and transportation as described above to connect a flexible composite pipe for oilfield gathering and transportation as described above, includes the following steps: S1: Peel off and expose the inner lining barrier layer at the connection ends of the two flexible composite pipes, and pre-sleeve the non-metallic joint inner sleeve onto any one of the connection ends of the two flexible composite pipes, with the sleeved-in depth exceeding the length of the peeled-off section of the inner lining barrier layer; S2: Connect the inner lining barrier layers at the connection ends of the two flexible composite pipes by hot melt welding to form a hot melt weld seam. The welding heating temperature is 200 °C, the welding time is 60 s, and the welding pressure per unit area is 0.10 N / mm 2 ; S3: After cooling the welded inner lining barrier layer to room temperature, first use a flexible wide-width heating belt to wind and wrap the exposed inner lining barrier layer, and weld the copper foil strip of the flexible wide-width heating belt and the copper foil strip inside the flexible composite pipe with a welding torch; S4: Use an aerogel heat preservation belt to completely wrap the flexible wide-width heating belt; S5: Continue to wind and wrap with a fiber resin belt until the thickness is the same as that of the outer protective layer of the flexible composite pipe and then stop. During the winding process, simultaneously use a hot air gun to heat the fiber resin belt. The heating temperature is 80 - 100 °C, and gradually bond the resin fiber belts inside the outer protective layer of the flexible composite pipe into one body to form a fiber resin connection belt; S6: Move the non-metallic joint inner sleeve to the position wrapped by the fiber resin belt, use a clamping tool for positioning to make the non-metallic joint inner sleeve and the flexible composite pipe in a concentric position, perform electrofusion connection on it, remove the clamping tool after cooling to room temperature, and conduct a pressure resistance test on the connected flexible composite pipe. After passing the test, the connection is completed.

[0014] The technical effects of the present invention are as follows: 1. By arranging a flexible wide-width heating tape and an aerogel heat-insulating tape inside the flexible composite pipe, the present invention realizes the integrated design of heat preservation and heating for the flexible composite pipe used in oilfield gathering and transportation, meeting the actual requirements of the oilfield for the multi-functional integration of self-heating and heat preservation of the flexible composite pipe for gathering and transporting oil; 2. The present invention replaces the existing metal joint with a non-metallic full-bore joint, achieving a full bore, facilitating the pigging operation in the oilfield, greatly reducing the heat loss at the connection of the existing joints, and the joint is made of all non-metallic materials, with light weight, making the on-site construction tools more lightweight, quick to assemble, and convenient for on-site workers to operate; 3. The present invention uses a flexible wide-width heating tape made of a heating material as the heating functional layer of the composite pipe. Here, through the conductive coating on the flexible wide-width heating tape, the full coverage of the pipeline heating can be realized, overcoming the problem of uneven pipeline temperature caused by the partial heating of the traditional heating tape or heating pipe to the pipeline; 4. The present invention uses a fiber resin tape as the strengthening functional layer, making the fiber resin tape more evenly distributed on the pipeline circumference, with a more uniform strength distribution, and because of the presence of the resin, a bonding structure is formed between the layers of the pipeline concentric layer during the forming process; 5. The present invention forms the outer protective layer of the pipeline by multi-layer co-extrusion of polyethylene pellets of different colors, which can give an early warning of different degrees of damage to the outer protective layer caused by dragging and construction of the pipeline, facilitating the identification by on-site operators.

[0015] The following will be further described with reference to the accompanying drawings. Brief Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of a flexible composite pipe for oilfield gathering and transportation according to an embodiment of the present invention.

[0017] Figure 2 It is a schematic cross-sectional structural diagram of a flexible composite pipe for oilfield gathering and transportation according to an embodiment of the present invention.

[0018] Figure 3 It is a schematic connection structural diagram of a flexible composite pipe joint for oilfield gathering and transportation according to an embodiment of the present invention.

[0019] Reference numerals: 1 - inner lining barrier layer, 2 - copper foil tape, 3 - flexible wide-width heating tape, 4 - nano coating, 5 - heating functional layer, 6 - heat preservation functional layer, 7 - aerogel heat-insulating tape, 8 - fiber resin tape, 9 - outer protective layer, 10 - innermost layer of the outer protective layer, 11 - intermediate layer of the outer protective layer, 12 - outermost layer of the outer protective layer, 13 - strengthening functional layer, 14 - inner sleeve of the non-metallic joint, 15 - fiberglass reinforcement layer, 16 - fiber resin connection tape, 17 - hot melt weld seam, 18 - heating wire. Detailed Embodiments Embodiment 1

[0020] As Figure 1 、Figure 2 As shown in the figure, a flexible composite pipe for oilfield gathering and transportation includes, from the inside to the outside, an inner lining barrier layer 1, a heating functional layer 5, a heat preservation functional layer 6, and an outer protection layer 9 that are connected in sequence. The heating functional layer 5 includes a flexible wide-width heating tape 3. A copper foil tape 2 is provided inside the flexible wide-width heating tape 3. A conductive nano-coating 4 is provided on the outer surface of the copper foil tape 2. The flexible wide-width heating tape 3 is spirally wound around the outside of the inner lining barrier layer 1. The heat preservation functional layer 6 is a sandwich structure and includes an aerogel heat preservation tape 7. Polyethylene films are respectively provided on both the inner and outer sides of the aerogel heat preservation tape 7. The outer protection layer 9 is a polyethylene multi-layer structure and includes an innermost layer 10 of the outer protection layer, a middle layer 11 of the outer protection layer, and an outermost layer 12 of the outer protection layer. The thickness of the outermost layer 12 of the outer protection layer is greater than the thicknesses of the innermost layer 10 and the middle layer 11 of the outer protection layer.

[0021] During actual use, in the heating functional layer 5 of the present invention, infrared heating is used for heating. After the copper foil tape 2 in the flexible wide-width heating tape 3 is electrified, it directly supplies power to the conductive nano-coating 4. Inner layer electrons in various nano-materials atoms in the conductive nano-coating 4 are excited and undergo energy level transitions under the action of an external electric field, transitioning from a low energy level to a high energy level; after a short excited state, they will quickly transition back to a lower energy level, and at the same time, the released energy is emitted in the form of electric and magnetic field energy packets to generate heat. This heat is transferred to the medium conveyed by the flexible composite pipe through the material of the inner lining barrier layer 1 to increase the temperature of the conveyed medium. At the same time, the aerogel heat preservation tape 7 isolates the heat transfer caused by the temperature difference inside and outside the pipeline, reducing the heat loss of the pipeline conveying medium. The present invention realizes the integrated design of heat preservation and heating of the flexible composite pipe for oilfield gathering and transportation by arranging a flexible wide-width heating tape and an aerogel heat preservation tape inside the flexible composite pipe, meeting the actual needs of the oilfield for the multi-functional integration of self-heating and heat preservation of the flexible composite pipe for gathering and transporting oil. Example 2

[0022] Preferably, on the basis of Example 1, in this embodiment, an enhanced functional layer 13 is provided between the aerogel heat preservation tape 7 and the outer protection layer 9. The enhanced functional layer 13 includes a plurality of fiber resin tapes 8. The fiber resin tapes 8 are spirally wound around the outside of the aerogel heat preservation tape 7.

[0023] During actual use, an enhanced functional layer 13 is provided between the aerogel heat preservation tape 7 and the outer protection layer 9 of the present invention. The enhanced functional layer 13 includes a plurality of fiber resin tapes 8. The fiber resin tapes 8 are spirally wound around the outside of the aerogel heat preservation tape 7, making the fiber bundles more evenly distributed on the pipeline circumference and the strength distribution more uniform. Example 3

[0024] Preferably, on the basis of Example 1 or Example 2, in this embodiment, the inner lining barrier layer 1 is formed by extruding polyethylene pellets through a single-screw extruder, and its thickness is 35% - 42% of the overall wall thickness of the flexible composite pipe. The polyethylene pellets include LLDPE, antioxidant 1076, co-antioxidant DLTP, and anti-aging agent H. By weight percentage: LDPE: antioxidant 1076: co-antioxidant DLTP: anti-aging agent H = 99: 0.15: 0.15: 0.7.

[0025] During actual use, when the polyethylene pellets of the present invention are extruded through a single-screw extruder, the extrusion temperature is 180 - 200 °C, the die temperature of the head is 190 - 200 °C, the screw speed is 55 r / min, and the inner lining barrier layer 1 can be customized in formula design according to the different properties of the conveyed medium. Example 4

[0026] Preferably, on the basis of Example 1, in this embodiment, the thickness of the flexible wide heat supply belt 3 is 2 - 3 mm, the width is 75 - 80 mm, its winding angle is 15 - 35°, the thickness of the polyethylene film is 0.02 - 0.05 mm, the thickness of the heat preservation functional layer 6 is 2 - 3 mm, the width is 80 - 150 mm, the thermal conductivity is 0.018 W / (m･K), and the winding angle is 15 - 20°.

[0027] During actual use, the thickness of the polyethylene film of the present invention is 0.02 mm, the thickness of the heat preservation functional layer 6 is 3 mm, the width is 150 mm, and the thermal conductivity is 0.018 W / (m･K), which can isolate the heat transfer caused by the temperature difference inside and outside the pipeline and reduce the heat loss of the conveyed medium in the pipeline. Example 5

[0028] Preferably, on the basis of Example 1 or Example 4, in this embodiment, the fiber resin tape 8 is made of 65% polyester fiber and 35% polyethylene. The fiber resin tape 8 has a thickness of 2 - 3 mm, a width of 65 - 70 mm, and a winding angle of 54.7°.

[0029] During actual use, the fiber resin tape 8 of the present invention is made of 65% polyester fiber and 35% polyethylene. By winding multiple layers of fiber resin tapes 8 in positive spiral and negative spiral, the enhanced functional layer is formed to ensure the structural strength of the flexible composite pipe. Example 6

[0030] Preferably, based on Embodiment 1 or Embodiment 5, in this embodiment, the thickness of the innermost layer 10 and the middle layer 11 of the outer protective layer is 1 mm, and the thickness of the outermost layer 12 of the outer protective layer is 2 mm. The innermost layer 10, the middle layer 11, and the outermost layer 12 of the outer protective layer have different colors, which are red, yellow, and black, respectively.

[0031] During actual use, the innermost layer 10, the middle layer 11, and the outermost layer 12 of the outer protective layer of the present invention have different colors, which are red, yellow, and black, respectively. When different color layers are exposed after the outer protective layer 9 is worn during construction, corresponding remedial measures are taken according to different wear thicknesses. Embodiment 7

[0032] As Figure 3 shown, a flexible composite pipe joint for oilfield gathering and transportation is used to connect a flexible composite pipe for oilfield gathering and transportation as described above. It includes a non-metallic joint inner sleeve 14, and a heating wire 18 is contained inside the non-metallic joint inner sleeve 14. The heating wire 18 is in a spiral shape. A straight thread is provided on the inner side wall of the non-metallic joint inner sleeve 14, and a fiberglass reinforcement layer 15 is provided outside the non-metallic joint inner sleeve 14.

[0033] During actual use, a flexible composite pipe joint for oilfield gathering and transportation of the present invention includes a non-metallic joint inner sleeve 14. A heating wire 18 is contained inside the non-metallic joint inner sleeve 14. The heating wire 18 is in a spiral shape. A straight thread is provided on the inner side wall of the non-metallic joint inner sleeve 14. The joint with a fully non-metallic bonding structure is lighter in weight, has better fatigue performance, is more convenient and faster in construction, can effectively reduce the heat loss caused by the high thermal conductivity of the metal connection joint, and the pipeline has 100% through diameter at the joint connection. Embodiment 8

[0034] Preferably, based on Embodiment 7, in this embodiment, the fiberglass reinforcement layer 15 is formed by reciprocally and spirally winding wet-preimpregnated epoxy resin with fiberglass. The thickness of the fiberglass reinforcement layer 15 is the same as the thickness of the non-metallic joint inner sleeve 14. The length of the fiberglass reinforcement layer 15 and the non-metallic joint inner sleeve 14 is twice the inner diameter of the inner lining barrier layer 1. The thickness of the non-metallic joint inner sleeve 14 is twice the thickness of the inner lining barrier layer 1.

[0035] During actual use, the fiberglass reinforcement layer 15 of the present invention is formed by reciprocally and spirally winding wet-preimpregnated epoxy resin with fiberglass. The thickness of the fiberglass reinforcement layer 15 is the same as the thickness of the non-metallic joint inner sleeve 14, ensuring the connection strength of the flexible composite pipe joint. Embodiment 9

[0036] A connection method for a flexible composite pipe used in oilfield gathering and transportation, using a flexible composite pipe joint for oilfield gathering and transportation as described above to connect a flexible composite pipe for oilfield gathering and transportation as described above, comprising the following steps: S1: Peel off and expose the inner lining barrier layer 1 at the connection ends of the two flexible composite pipes, and pre - sleeve the non - metal joint inner sleeve 14 onto any one of the connection ends of the two flexible composite pipes, with the sleeved - in depth exceeding the length of the peeled - off section of the inner lining barrier layer 1; S2: Connect the inner lining barrier layers 1 at the connection ends of the two flexible composite pipes by hot - melt welding to form a hot - melt weld 17. The welding heating temperature is 200 °C, the welding time is 60 s, and the welding pressure per unit area is 0.10 N / mm 2 ; S3: After cooling the welded inner lining barrier layer 1 to room temperature, first wind the flexible wide - width heating tape 3 to wrap the exposed inner lining barrier layer 1, and weld the copper foil tape 2 of the flexible wide - width heating tape 3 and the copper foil tape 2 inside the flexible composite pipe using a welding torch; S4: Use the aerogel heat - insulating tape 7 to completely wrap the flexible wide - width heating tape 3; S5: Continue to wind and wrap with the fiber - resin tape 8 until it reaches the same thickness as the outer protective layer 9 of the flexible composite pipe and then stop. During the winding process, simultaneously heat the fiber - resin tape 8 with a hot air gun. The heating temperature is 80 - 100 °C, and gradually bond the resin - fiber tapes inside the outer protective layer 9 of the flexible composite pipe into one body to form a fiber - resin connection tape 16; S6: Move the non - metal joint inner sleeve 14 to the part wrapped by the fiber - resin tape 8, position it with a clamping tool to make the non - metal joint inner sleeve 14 and the flexible composite pipe in a concentric position, perform electro - fusion connection on them, remove the clamping tool after cooling to room temperature, and conduct a pressure resistance test on the connected flexible composite pipe. After passing the test, the connection is completed.

[0037] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A flexible composite pipe for oilfield gathering and transportation, Characterized in that: It includes an inner lining barrier layer (1), a heating functional layer (5), a heat insulation functional layer (6) and an outer protective layer (9) connected in sequence from inside to outside. The heating functional layer (5) includes a flexible wide-width heating tape (3). A copper foil tape (2) is arranged inside the flexible wide-width heating tape (3). A conductive nano-coating (4) is arranged on the outer surface of the copper foil tape (2). The flexible wide-width heating tape (3) is spirally wound outside the inner lining barrier layer (1). The heat insulation functional layer (6) is a sandwich structure and includes an aerogel heat insulation tape (7). Polyethylene films are arranged on both the inner and outer sides of the aerogel heat insulation tape (7). The outer protective layer (9) is a polyethylene multi-layer structure and includes an innermost layer of the outer protective layer (10), a middle layer of the outer protective layer (11) and an outermost layer of the outer protective layer (12). The thickness of the outermost layer of the outer protective layer (12) is greater than the thicknesses of the innermost layer of the outer protective layer (10) and the middle layer of the outer protective layer (11).

2. The flexible composite pipe for oilfield gathering and transportation according to claim 1, Characterized in that: An enhanced functional layer (13) is arranged between the aerogel heat insulation tape (7) and the outer protective layer (9). The enhanced functional layer (13) includes a plurality of fiber resin tapes (8). The fiber resin tapes (8) are spirally wound outside the aerogel heat insulation tape (7).

3. The flexible composite pipe for oilfield gathering and transportation according to claim 1, Characterized in that: The inner lining barrier layer (1) is extruded and formed by polyethylene pellets through a single-screw extruder. Its thickness is 35% - 42% of the overall wall thickness of the flexible composite pipe. The polyethylene pellets include LLDPE, antioxidant 1076, co-antioxidant DLTP and anti-aging agent H. By weight percentage: LDPE: antioxidant 1076: co-antioxidant DLTP: anti-aging agent H = 99: 0.15: 0.15: 0.

7.

4. The flexible composite pipe for oilfield gathering and transportation according to claim 1, Characterized in that: The thickness of the flexible wide-width heating tape (3) is 2 - 3 mm, the width is 75 - 80 mm, and its winding angle is 15 - 35°. The thickness of the polyethylene film is 0.02 - 0.05 mm. The thickness of the heat insulation functional layer (6) is 2 - 3 mm, the width is 80 - 150 mm, the thermal conductivity is 0.018 W / (m･K), and the winding angle is 15 - 20°.

5. The flexible composite pipe for oilfield gathering and transportation according to claim 2, Characterized in that: The fiber resin tape (8) is prepared from 65% polyester fiber and 35% polyethylene. The thickness of the fiber resin tape (8) is 2 - 3 mm, the width is 65 - 70 mm, and the winding angle is 54.7°.

6. The flexible composite pipe for oilfield gathering and transportation according to claim 1, Characterized in that: The thickness of the innermost layer (10) and the middle layer (11) of the outer protective layer is 1 mm, and the thickness of the outermost layer (12) of the outer protective layer is 2 mm. The innermost layer (10), the middle layer (11) and the outermost layer (12) of the outer protective layer have different colors, which are red, yellow and black respectively.

7. A flexible composite pipe joint for oilfield gathering and transportation, used to connect a flexible composite pipe for oilfield gathering and transportation as described in Claim 1. It is characterized in that: It includes a non-metallic joint inner sleeve (14). The non-metallic joint inner sleeve (14) contains a heating wire (18) inside. The heating wire (18) is in a spiral shape. The inner side wall of the non-metallic joint inner sleeve (14) is provided with straight threads, and a fiberglass reinforcement layer (15) is arranged outside the non-metallic joint inner sleeve (14).

8. A flexible composite pipe joint for oilfield gathering and transportation according to Claim 7. It is characterized in that: The fiberglass reinforcement layer (15) is formed by wet pre-impregnating epoxy resin with fiberglass and reciprocally spirally winding. The thickness of the fiberglass reinforcement layer (15) is the same as that of the non-metallic joint inner sleeve (14). The length of the fiberglass reinforcement layer (15) and the non-metallic joint inner sleeve (14) is twice the inner diameter of the inner lining barrier layer (1). The thickness of the non-metallic joint inner sleeve (14) is twice the thickness of the inner lining barrier layer (1).

9. A connection method for a flexible composite pipe for oilfield gathering and transportation, using a flexible composite pipe joint for oilfield gathering and transportation as described in Claim 7 to connect a flexible composite pipe for oilfield gathering and transportation as described in Claim 1. It is characterized in that: It includes the following steps: S1: Peel off and expose the inner lining barrier layer (1) at the connection ends of the two flexible composite pipes. Advance the non-metallic joint inner sleeve (14) to any one of the connection ends of the two flexible composite pipes, and the insertion depth exceeds the length of the peeled section of the inner lining barrier layer (1). S2: The inner lining barrier layers (1) of the connecting ends of the two flexible composite pipes are connected by hot melt welding to form a hot melt weld (17). The welding heating temperature is 200 °C, the welding time is 60 s, and the welding pressure per unit area is 0.10 N / mm 2 ; S3: After cooling the welded inner lining barrier layer (1) to room temperature, first use the flexible wide-width heating belt (3) to wind and wrap the exposed inner lining barrier layer (1), and weld the copper foil strip (2) of the flexible wide-width heating belt (3) and the copper foil strip (2) inside the flexible composite pipe with a welding torch. S4: Use the aerogel heat preservation belt (7) to completely wrap the flexible wide-width heating belt (3). S5: Continue to wind and wrap with the fiber resin belt (8) until the thickness is the same as that of the outer protective layer (9) of the flexible composite pipe and then stop. During the winding process, simultaneously use a hot air gun to heat the fiber resin belt (8), and the heating temperature is 80 - 100 °C. Gradually bond the resin fiber belts inside the outer protective layer (9) of the flexible composite pipe into a whole to form a fiber resin connection belt (16). S6: Move the non-metallic joint inner sleeve (14) to the winding and wrapping position of the fiber resin belt (8), use a clamping tool for positioning to make the non-metallic joint inner sleeve (14) and the flexible composite pipe in a concentric position, perform electrofusion connection on them, remove the clamping tool after cooling to room temperature, and conduct a pressure resistance test on the connected flexible composite pipe. After the test is qualified, the connection is completed.

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