Underwater pipe comprising a sheath made of a polypropylene homopolymer

Abstract

An underwater pipe, including a metal reinforcing layer around an inner polymeric sealing sheath capable of being in contact with hydrocarbons. The inner polymeric sealing sheath includes a homopolymeric polypropylene or a mixture of homopolymeric polypropylenes, wherein the homopolymeric polypropylene or the mixture has a density greater than 0.900 g/cm.sup.3, and a melt index measured at 230° C. under a mass of 2.16 kg of less than 10 g/10 minutes, its preparation method and its use for the transport of hydrocarbons. Such a sheath may be used in contact with hydrocarbons at high temperature.

Claims

1. An underwater flexible pipe for the transport of hydrocarbons comprising an arrangement that consists of a metal reinforcing layer that is directly contacting an inner polymeric sealing sheath, the metal reinforcing layer consisting of metallic tensile armor plies, each metallic tensile armor ply being defined by a helical winding of at least one metal wire and having a helical angle of less than 60°, wherein said pipe does not have an inner hydrocarbon-proof layer that prevents contact between said inner polymeric sealing sheath and hydrocarbons, wherein the inner polymeric sealing sheath consists of only one layer comprising a homopolymeric polypropylene or a mixture of homopolymeric polypropylenes, and wherein the homopolymeric polypropylene or the mixture has: a density greater than 0.900 g/cm.sup.3, and a melt index measured at 230° C. under a mass of 2.16 kg of less than 10 g/10 minutes, the inner polymeric sealing sheath being free of polyethylene.

2. The underwater pipe according to claim 1, wherein the homopolymeric polypropylene or the homopolymeric polypropylene mixture has: a density greater than 0.902 g/cm.sup.3, and/or a melt index measured at 230° C. under a mass of 2.16 kg of less than 5 g/10 min.

3. The underwater pipe according to claim 1, wherein the homopolymeric polypropylene or homopolymeric polypropylene mixture has a melting temperature of at least 145° C.

4. The underwater pipe according to claim 1, wherein the homopolymeric polypropylene has a degree of crystallinity of at least 40%, or the homopolymeric polypropylene mixture comprises at least one homopolymeric polypropylene having a degree of crystallinity of at least 40%.

5. The underwater pipe according to claim 1, wherein the homopolymeric polypropylene or the homopolymeric polypropylene mixture has a swelling rate of less than 30% by weight when it is brought into contact with Biofree EN 590 diesel at 110° C. for 6 hours.

6. The underwater pipe according to claim 1, wherein the homopolymeric polypropylene is an isotactic homopolymeric polypropylene, or the homopolymeric polypropylene mixture comprises at least one isotactic homopolymeric polypropylene.

7. The underwater pipe according to claim 6, wherein the isotactic homopolymeric polypropylene, or the at least one isotactic homopolymeric polypropylene of the homopolymeric polypropylene mixture, has an isotacticity rate of at least 93%.

8. The underwater pipe according to claim 6, wherein the isotactic homopolymeric polypropylene, or the at least one isotactic homopolymer of the homopolymeric polypropylene mixture, has a crystalline morphology more than 50% of the beta and/or alpha type.

9. The underwater pipe according to claim 1, wherein the weight ratio of homopolymeric polypropylene, or of the mixture of homopolymeric polypropylenes, in the inner polymeric sealing sheath is greater than 50% by weight relative to the inner polymeric sealing sheath.

10. The underwater pipe according to claim 1, wherein the homopolymeric polypropylene is crosslinked, or the homopolymeric polypropylene mixture comprises at least one crosslinked homopolymeric polypropylene.

11. A method for transporting hydrocarbons wherein the hydrocarbons are transported in the underwater pipe according to claim 1.

12. An underwater pipe for the transport of hydrocarbons comprising an arrangement that consists of an inner polymeric sealing sheath and a metal reinforcing layer consisting of a metal tube which is directly contacting the inner polymeric sealing sheath, wherein the pipe does not have an inner hydrocarbon-proof layer that prevents contact between the inner polymeric sealing sheath and hydrocarbons, wherein the underwater pipe is rigid, and the inner polymeric sealing sheath consists of only one layer comprising a homopolymeric polypropylene or a mixture of homopolymeric polypropylenes, and wherein the homopolymeric polypropylene or the mixture has: a density greater than 0.900 g/cm.sup.3, and a melt index measured at 230° C. under a mass of 2.16 kg of less than 10 g/10 minutes, the inner polymeric sealing sheath being free of polyethylene.

13. An underwater flexible pipe for the transport of hydrocarbons, comprising an arrangement, from the outside to the inside: tensile armor plies, each tensile armor ply comprising a helical winding of at least one metal wire and having a helical angle of less than 60°, the tensile armor plies being directly around a pressure vault consisting of longitudinal metal wire wound with a helical winding at a helix angle between 75° and 90° as a metal reinforcing layer; an inner polymeric sealing sheath, the pressure vault directly contacting the inner polymeric sealing sheath; and a metal carcass, wherein the pipe does not have an inner hydrocarbon-proof layer that prevents contact between hydrocarbons and the inner polymeric sealing sheath, wherein the inner polymeric sealing sheath consists of only one layer comprising a homopolymeric polypropylene or a mixture of homopolymeric polypropylenes, and wherein the homopolymeric polypropylene or the mixture has: a density greater than 0.900 g/cm.sup.3, and a melt index measured at 230° C. under a mass of 2.16 kg of less than 10 g/10 minutes, the inner polymeric sealing sheath being free of polyethylene.

14. The underwater pipe according to claim 13, wherein the homopolymeric polypropylene or the homopolymeric polypropylene mixture has: a density greater than 0.902 g/cm.sup.3, and/or a melt index measured at 230° C. under a mass of 2.16 kg of less than 5 g/10 min.

15. The underwater pipe according to claim 13, wherein the homopolymeric polypropylene or homopolymeric polypropylene mixture has a melting temperature of at least 145° C.

16. The underwater pipe according to claim 13, wherein the homopolymeric polypropylene has a degree of crystallinity of at least 40%, or the homopolymeric polypropylene mixture comprises at least one homopolymeric polypropylene having a degree of crystallinity of at least 40%.

17. The underwater pipe according to claim 13, wherein the homopolymeric polypropylene or the homopolymeric polypropylene mixture has a swelling rate of less than 30% by weight when it is brought into contact with Biofree EN 590 diesel at 110° C. for 6 hours.

18. The underwater pipe according to claim 13, wherein the homopolymeric polypropylene is an isotactic homopolymeric polypropylene, or the homopolymeric polypropylene mixture that comprises at least one isotactic homopolymeric polypropylene.

19. The underwater pipe according to claim 18, wherein the isotactic homopolymeric polypropylene, or the at least one isotactic homopolymeric polypropylene of the homopolymeric polypropylene mixture, has an isotacticity rate of at least 93%.

Description

(1) Other features and advantages of the invention appear upon reading the description given below of particular embodiments of the invention, given for information but not limiting, with reference to FIGS. 1 and 2.

BRIEF DESCRIPTION OF THE DRAWINGS

(2) FIG. 1 shows a partial schematic perspective view of a flexible pipe according to the invention. It illustrates a pipe according to the invention comprising, from the outside to the inside: an outer polymeric sheath 10, an outer ply of tensile armor 12, an inner ply of tensile armor 14 wound in the opposite direction to the outer ply 12, a pressure vault 18 to take up the radial forces generated by the pressure of the hydrocarbons transported, an inner polymeric sheath 20, and an inner carcass 22 to take up radial crushing forces,
wherein the inner polymeric sealing sheath 20 comprises a homopolymeric polypropylene or a homopolymeric polypropylene mixture with a density and melt index as defined above.

(3) Due to the presence of the inner carcass 22, this pipe is said to be rough bore. The invention could also be applied to a so-called smooth-bore pipe, which does not include an inner carcass.

(4) Likewise, the scope of the present invention is not exceeded by eliminating the pressure vault 18, insofar as the helix angles of the threads constituting the armor plies 12, 14 are close to 55° and in the opposite direction.

(5) The armor plies 12, 14 are obtained by long-pitch winding of a set of metal or composite material wires, generally of substantially rectangular section. The invention also applies if these wires have a section of circular or complex geometry, for example of the auto-stapled T type. FIG. 1 shows only two armor plies 12 and 14, but the pipe could also include one or more additional armor pairs. The armor ply 12 is said to be external because it is here the outermost, starting from the inside of the pipe, before reaching the outer sealing sheath 10.

(6) The flexible pipe may also comprise layers not shown in FIG. 1, such as: a holding layer between the outer polymeric sheath 10 and the tensile armor plies 12 and 14, or between two tensile armor plies, one or more anti-wear layers of polymeric material in contact either with the inner face of the aforementioned holding layer, or with its outer face, or with both faces, wherein this anti-wear layer prevents the holding layer from wear through contact with metal armor. Anti-wear layers, which are well known to those skilled in the art, are generally made by helical winding of one or more ribbons obtained by extrusion of a polymeric material based on polyamide, polyolefins, or PVDF (polyvinylidene fluoride). Reference may also be made to the document WO 2006/120320 which describes anti-wear layers consisting of polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) or phenylene polysulfide (PPS) ribbons.

(7) FIG. 2 shows a partial schematic perspective view of a rigid pipe according to the invention. It illustrates a pipe according to the invention comprising, from the outside to the inside: a metal reinforcing layer 8, an inner polymer polymeric sheath 9 comprising a homopolymeric polypropylene or a mixture of homopolymeric polypropylenes of density and melt index as defined above.

EXAMPLE

Example 1: Swelling Rate of Polypropylenes in the Presence of a Petroleum Fluid at Elevated Temperature

(8) Samples of different families of polypropylene were weighed and then contacted with a petroleum fluid: the Biofree EN 590 diesel, and then weighed after contact for a certain time in this fluid. The difference in mass before and after contacting makes it possible to determine the degree of swelling.

(9) The swelling rate (mass percentage) of various families of polypropylene in the presence of a petroleum fluid: the Biofree EN 590 diesel, were compared and are provided in Table 1.

(10) TABLE-US-00001 TABLE 1 Swelling rate of various polypropylenes in the presence of Biofree EN 590 diesel swelling rate in presence density of Biofree EN 590 diesel fluid index according to at at at according to ISO 1183 110° C. 110° C. 120° C. ASTM D1238 revised in after after after polypropylene (g/10 min) 2012 6 h 188 h 115 h syndiotactic FINAPLAST 2.0 0.88 31% x x homopolymer 1251 from Total graft PPR 3221 from 1.8 0.902 110%  x x copolymer Total isotactic PPH3060 from 1.8 0.905 13% 21% 24% homopolymer Total isotactic Beta (β)-PP ™ 0.3 0.905 16% 33% 44% homopolymer BE60-7032 from Borealis metallocene Lumicene 10 0.902 88% x x static MR10MX0 copolymer from Total isotactic Hostallen PPH 0.3 0.915 14% 25% 39% homopolymer 2250 36 from Lyondell basell

(11) These results show that the homopolymeric polypropylenes used in the sheath of the pipe according to the invention have a low swelling rate in the presence of hydrocarbons at high temperatures.

Example 2: Resistance of Polypropylenes Upon Violent Decompressions

(12) Various families of polypropylene were placed in the presence of a petroleum fluid: consisting of 85% of CH.sub.4 and 15% of CO.sub.2 at 110° C. at 200 bar, and then the pressure was lowered to atmospheric pressure (1 bar) at a speed of 70 bar/min. The appearance of blisters on the surface of the polypropylenes after this treatment was monitored (Table 2).

(13) TABLE-US-00002 TABLE 2 appearance of blisters on the surface of various polypropylenes after violent decompressions fluid index density according according to ASTM to ISO 1183 polypropylene D1238 (g/10 min) revised in 2012 blistering syndiotactic FINAPLAST 1251 2 0.88 yes homopolymer from Total graft copolymer PPR 3221 from 1.8 0.902 yes Total isotactic PPH3060 from 1.8 0.905 no homopolymer Total isotactic Beta (β)-PP ™ 0.3 0.905 no homopolymer BE60-7032 from Borealis isotactic Hostallen PPH 2250 0.3 0.915 no homopolymer 36 from Lyondell basell

(14) These results show that the homopolymeric polypropylene used in the pipe according to the invention are capable of withstanding violent decompressions simulating production shut-downs.