Polymeric materials

Abstract

Polymeric materials for use in challenging situations in the oil and gas industry (e.g. challenging physical and chemical environments) are described. The polymeric materials comprise a polymeric material having a repeat unit of formula I and a repeat unit of formula II wherein Ph represents a phenylene moiety; wherein the repeat units I and II are in the relative molar proportions 95:5 to 80:20.

Claims

1. An oil and/or gas installation or apparatus for use in relation to an oil and/or gas installation, said installation or apparatus comprising a component which comprises a copolymer, wherein the copolymer comprises a repeat unit of formula
—O-Ph-Ph-O-Ph-CO-Ph-  I and a repeat unit of formula
—O-Ph-Ph-O-Ph-SO.sub.2-Ph-Ph-SO.sub.2-Ph-  II wherein Ph represents a phenylene moiety; wherein the repeat units I and II are in the relative molar proportions 95:5 to 80:20.

2. The installation or apparatus according to claim 1, wherein hydrogen sulphide and/or sour gas is present in the installation or apparatus.

3. The installation or apparatus according to claim 1, wherein said component is, at the same time, subjected to at least two of the following: a temperature in the range 150° C. to 350° C., a pressure in the range 40 MPa to 300 MPa, and an acidic gas such as containing hydrogen sulphide.

4. The installation or apparatus according to claim 1, wherein said component is selected from the following: seals, back-up rings, plugs and packers, motor winding slot liners, protector thrust bearings, motor pot heads, compressor vanes, bearings and bushes, thrust washers, valve plates, high pressure hoses, downhole sensors, marine risers, subsea umbilicals, hoses and sheaths.

5. The installation or apparatus according to claim 1, wherein said component which comprises said copolymer is arranged to guide the flow of a fluid, restrict the flow of a fluid, facilitate movement between two parts, facilitate support of one or more parts and/or facilitate connection of two or more parts.

6. The installation or apparatus according to claim 5, wherein said component which guides flow of a fluid comprises a carrier for oil and/or gas, wherein the carrier is a hose, a riser, a subsea umbilical or a sheath; wherein said component which restricts the flow of a fluid comprises a seal, back-up ring or plug; and wherein said component which facilitates movement between two parts, facilitates supports of one or more parts or facilitates connection of two or more parts comprises bearings, bushes, washers or valve plates.

7. The installation or apparatus according to claim 1, wherein said component which comprises said copolymer is a seal or back-up ring.

8. The installation or apparatus according to claim 1, wherein said repeat unit of formula I has the structure ##STR00007## and said repeat unit of formula II has the structure ##STR00008##

9. The installation or apparatus according to claim 1, wherein said copolymer includes 81% to 90 mol % of repeat units of formula I.

10. The installation or apparatus according to claim 1, wherein said copolymer includes 82% to 88 mol %, of repeat units of formula I.

11. The installation or apparatus according to claim 1, wherein said copolymer includes 10% to 19 mol % of repeat units of formula II.

12. The installation or apparatus according to claim 1, wherein said copolymer includes 12% to 18 mol % of repeat units of formula II.

13. The installation or apparatus according to claim 1, wherein the Tm of said copolymer is in the range 350° C. to 410° C.

14. The installation or apparatus according to claim 1, wherein said copolymer has a crystallinity of at least 25%.

15. The installation or apparatus according to claim 1, wherein said copolymer is part of a composition which includes said copolymer and a filler means.

16. A component which comprises a copolymer wherein the copolymer comprises a repeat unit of formula
—O-Ph-Ph-O-Ph-CO-Ph-  I and a repeat unit of formula
—O-Ph-Ph-O-Ph-SO.sub.2-Ph-Ph-SO.sub.2-Ph-  II wherein Ph represents a phenylene moiety; wherein the repeat units I and II are in the relative molar proportions 95:5 to 80:20, wherein said component is of a type which is arranged to guide the flow of a fluid, facilitate movement between two parts, facilitate support of one or more parts and/or facilitate connection of two or more parts.

17. The component according to claim 16, wherein said component which guides flow of a fluid comprises a carrier for oil and/or gas, wherein the carrier is a hose, a riser, a subsea umbilical or a sheath; said component which restricts the flow of a fluid comprises a seal, back-up ring or plug; and said component which facilitates movement between two parts, facilitates supports of one or more parts or facilitates connection of two or more parts comprises bearings, bushes, washers or valve plates.

18. The component according to claim 16, wherein said copolymer of said component is arranged to directly contact oil and/or gas associated with said installation in use.

19. The component according to claim 16, wherein said component which comprises said copolymer is a seal or back-up ring.

20. A method of assembling a part of an oil and/or gas installation, the method comprising: (i) selecting a component which comprises a copolymer or selecting apparatus or a device for use in relation to the oil and/or gas installation which comprises said copolymer; (ii) introducing said component, apparatus or device into said oil and/or gas installation; wherein said copolymer has a repeat unit of formula
—O-Ph-Ph-O-Ph-CO-Ph-  I and a repeat unit of formula
—O-Ph-Ph-O-Ph-SO.sub.2-Ph-Ph-SO.sub.2-Ph-  II wherein Ph represents a phenylene moiety; wherein the repeat units I and II are in the relative molar proportions 95:5 to 80:20.

Description

(1) Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying figures, in which:

(2) FIG. 1 is a cross-section through an assembly comprising a valve stem and valve housing.

(3) FIG. 2 is a graph of glass transition temperature (Tg) in ° F. versus pressure in psi for two polymers assessed using PVT apparatus; and

(4) FIG. 3 is a graph of tensile stress retention versus time (hours) for three polymers exposed to sour gas.

(5) The following materials are referred to hereinafter:

(6) PEEK—refers to Victrex® PEEK 450G; polyetheretherketone having an MV of 0.45 kNsm.sup.−2, obtained from Victrex Manufacturing Ltd;

(7) PEK—refers to Victrex® HT™ G22; polyetherketone having an MV of 0.22 kNsm.sup.−2, obtained from Victrex Manufacturing Ltd.

(8) In the following examples, the preparation and testing of polymeric materials are described.

EXAMPLE 1

(9) 4,4′-dihydroxybiphenyl (95.47 g, 0.5 mol), 4,4′-bis(4-chlorophenylsulphonyl)biphenyl (37.76 g, 0.075 mol), 4, 4′-difluorobenzophenone (BDF) (95.47 g, 0.4375 mol) and diphenylsulfone (422.7 g) were weighed into a 1 liter flanged flask. The flask was fitted with a mechanical stirrer (set at 125 rpm), a PTFE stirrer gland and a lid containing a condenser, nitrogen inlet, thermocouple inlet and inlet port. The mixture was stirred under nitrogen for 20 minutes at ambient temperature before being lowered into a metal bath at 180° C. Once the contents of the flask were fully molten and the contents temperature reached 180° C., Na.sub.2CO.sub.3 (54.98 g, 0.5188 mol) and K.sub.2CO.sub.3 (0.17 g, 0.00125 mol) both sieved to 125 μm were mixed and added to the flask. The contents of the flask were heated to 335° C. at 1° C./min and held at that temperature until the desired MV was reached as indicated by the torque rise on the stirrer. The required torque rise was determined from a calibration graph of torque rise versus MV. The reaction mixture was then poured into a foil tray, allowed to cool, pulverised and milled and then washed with 1 liter of acetone, 1 liter of cold water and then hot (50-70° C.) water until the conductivity of the waste water was <2 μS before drying in an oven at 120° C. overnight.

EXAMPLE 2—EVALUATION OF POLYMERS BY DIFFERENTIAL SCANNING CALORIMETRY (DSC)

(10) A Mettler Toledo, DSC1 Star.sup.e system with FRS5 sensor was used for Differential Scanning Calorimetry (DSC) measurements.

(11) The Glass Transition Temperature (Tg), the Cold Crystallisation Temperature (Tn), the Melting Temperature (Tm) and Heat of Fusions of Nucleation (ΔHn) and Melting (ΔHm) for the polymers from Examples 1 to 14 were determined by DSC.

(12) A sample of polymer powder (5 mg) from each of the examples 1 and 4-11 was scanned by DSC as follows: 1. Perform a preliminary thermal cycle by heating the sample from 30° C. to 450° C. at 20° C./min. 2. Hold for 5 minutes. 3. Cool at 20° C./min to 30° C. and hold for 5 mins. 4. Re-heat from 30° C. to 450° C. at 20° C./min, recording the Tg, Tn, Tm, ΔHn and ΔHm.

(13) From the DSC trace resulting from the scan in step 4, the onset of the Tg was obtained as the intersection of the lines drawn along the pre-transition baseline and a line drawn along the greatest slope obtained during the transition. The Tn was the temperature at which the main peak of the cold crystallisation exotherm reaches a maximum. The Tm was the temperature at which the main peak of the melting endotherm reach maximum.

(14) The Heat of Fusion for melting (ΔHm) was obtained by connecting the two points at which the melting endotherm deviates from the relatively straight baseline. The integrated area under the endotherm as a function of time yields the enthalpy (mJ) of the melting transition: the mass normalised heat of fusion is calculated by dividing the enthalpy by the mass of the specimen (J/g). The level of crystallisation (%) is determined by dividing the Heat of Fusion of the specimen by the Heat of Fusion of a totally crystalline polymer, which is 140 J/g.

EXAMPLE 3—MELT VISCOSITY MEASUREMENT

(15) Melt viscosity was measured on a capillary rheometer operating at 435° C. at a shear rate of 1000 s.sup.−1 using a tungsten carbide die 0.5 mm×3.175 mm. The MV reading was taken 5 minutes after the polymer had fully melted, which is taken to be 5 minutes after the polymer is loaded into the barrel of the rheometer.

EXAMPLES 4-8

(16) The procedure of Example 1 was followed and the ratio of 4,4′-difluorobenzophenone (BDF) to 4,4′-bis(4-chlorophenylsulphonyl)biphenyl (LCDC) was varied as shown in Table 1. The Tg (onset), Tm, crystallinity and MV, assessed as described in Example 2 and 3 are also shown in the table for examples 1 and 4 to 8.

(17) TABLE-US-00001 TABLE 1 BDF:LCDC Tg onset Tm Example (mol %) MV @ 435° C. (° C.) (° C.) X (%) 4 90:10 0.57 188 408 39 1 85:15 0.53 198 403 33 5 82.5:17.5 0.52 202 401 29 6 80:20 0.50 203 396 27 7 75:25 0.47 213 397 23 8 70:30 0.50 207 372 13

EXAMPLE 9—SCALE UP OF EXAMPLE 1

(18) A 300 liter stainless steel reactor fitted with a lid, stirrer/stirrer guide, nitrogen inlet and outlet was charged with diphenylsulphone (115.8 kg) and heated to 160° C. Once the diphenylsulfone had fully melted, 4,4′-dihydroxybiphenyl (25.51 kg, 137 mol) 4,4′-diflurobenzophenone (26.16 kg, 119.9 mol) and LCDC (10.35 kg, 20.55 mol) were charged to the reactor under nitrogen. The contents were then heated to 180° C. and while maintaining a nitrogen blanket, dried sodium carbonate (15.03 kg, 141.8 mol) and potassium carbonate (0.095 kg, 0.685 mol), both sieved through a screen with a mesh of 125 micrometers, were added. The temperature was raised to 230° C. at 1° C./min and held for 60 minutes. The temperature was further raised to 335° C. at 1° C./min and held until desired melt viscosity was reached as determined by the torque rise of the stirrer. The required torque rise was determined from a calibration graph of torque rise versus MV. The reaction mixture was poured via a band caster into a water bath, allowed to cool, milled and washed with 2000 liters of acetone and 4500 liters of water. The resulting polymer powder was dried in a tumble dryer until the contents temperature measured 110° C.

EXAMPLE 10

(19) This was a repeat of Example 9, except that a lower MV polymer was obtained.

EXAMPLE 11

(20) This was a blend of the polymers of Examples 9 and 10 to achieve the specified MV.

(21) Results are provided in Table 2.

(22) TABLE-US-00002 TABLE 2 Example MV @ 435° C. Tg onset (° C.) Tm (° C.) X (%) 9 0.50 199 405 34 10 0.33 199 405 38 11 0.37 195 405 38

EXAMPLE 12—MECHANICAL TESTS

(23) Mechanical tests were undertaken on the material of Example 11 and compared to PEEK. Results are provided in Table 3.

(24) TABLE-US-00003 TABLE 3 Test Example 9 PEEK Tensile strength.sup.1 (MPa) 73 100 Tensile Elongation.sup.1 (%) 3 45 Tensile Modulus.sup.1 (GPa) 3.3 3.7 Flexural Strength.sup.2 (MPa) 149 125 Flexural Modulus.sup.2 (GPa) 3.2 4.1 .sup.1ISO 527 .sup.2ISO 178

(25) Selected materials were subjected to tests relevant to conditions experienced in many oil and gas installations. In such installations, where a pressure of greater than 69 MPa and greater than 149° C. is experienced, the conditions are known as High Pressure High Temperature (HPHT) conditions.

(26) Few polymers can operate under HPHT conditions; but one polymer which can is PEEK. PEEK was therefore selected for comparison with polymers according to preferred embodiments of the present invention.

EXAMPLE 13—PVT (PRESSURE-VOLUME-TEMPERATURE) DATA

(27) The specific volume of each polymer tested was measured at temperatures up to 420° C. and pressures up to 200 MPa using a PVT (Pressure Volume Temperature) apparatus.

(28) Measurements were performed under isobaric conditions (at 5, 50, 100, 150 and 200 MPa), over a temperature range of 23° C. to 420° C. for each pressure.

(29) The following procedure was used to derive the Tg/pressure relationship.

(30) For each isobaric run, the first inflection point on the specific volume versus temperature curve was identified (1.sup.st inflection point is Tg, 2.sup.nd is melting point).

(31) The position of the inflection point was determined from the intersection of tangents drawn on the flat parts of the curve either side (of inflection point).

(32) The resulting Tg values were then used to construct a Tg versus pressure plot, as shown in FIG. 2.

EXAMPLE 14—CREEP/COMPRESSION DATA

(33) The extent of extrusion (creep) was assessed by measuring the depth of the rim of test “seal ring” samples after application of a load.

(34) The polymer from Example 11 together with a sample of PEEK was pre-conditioned in an oven at a temperature of 260° C. (the temperature of the test) for 24 hours. After being machined to the correct size, the “seal rings” were mounted into test jig also at 260° C. and allowed to heat soak for 4 hours before a load of 37 kN was applied to the top of the rings for 2 hours. The load contacts the top of the ring pushing the polymer down (extruding it). Since the diameter of the load is less than that of the ring as it forces the polymer down, a rim is formed on the outside from non-extruded material. The height of the rim gives an indication of the degree extrusion of the polymer.

(35) Under the test conditions the polymers were found to extrude as would be observed in the case of a back-up seal ring operating in a downhole oil and gas environment. The extent of extrusion was assessed by measuring the depth of the rim formed on the “seal ring” after the load was removed by using Vernier callipers at the highest point and then again at 90° to the highest point. Results are provided in Table 4.

(36) TABLE-US-00004 TABLE 4 Height of rim at Height of rim at 90° to highest point (mm) highest point (mm) Example 11 1.10 1.05 PEEK 2.26 2.08

(37) Referring to the table, the rim is found to be shallower for the Example 11 material which demonstrates that the polymer extruders less than for PEEK, where the rim is approximately twice as deep.

EXAMPLE 15—SOUR FLUID EXPOSURE TESTING

(38) The resistance of the polymer from Example 11 to sour fluids was measured along with PEEK and PEK for comparison. Sour fluid exposure tests were carried out in hydrogen sulphide gas (CK Gas Products Ltd., Hook UK) environments at high temperature and pressure.

(39) For each exposure test, the specimens were installed in the gas phases within a pressure vessel. Tests were carried out at 175° C. and a pressure of 20 bar to simulate downhole conditions in subsea wells in the oil and gas industry. The ISO-527 test bars were exposed to the fluids for up to 1000 hours.

(40) Results are represented in FIG. 3.

(41) Discussion

(42) A review of the PVT data shows that polymeric material according to a preferred embodiment shows an improvement in Tg across a range of pressure. Tg pressure dependence for a polymer in an oil and gas environment described herein is believed to be important. In particular, a positive relationship (Tg increasing with pressure) can advantageously enhance mechanical performance. FIG. 2 shows this to be the case for the Example 9 material. However, for PEEK, at an operating pressure of 30,000 psi, the Tg is approximately 480° F. (i.e. below the operating temperature (500° F.)), so it will soften and is likely to extrude. In contrast, the Tg of the Example 9 material is approximately 560° F. (i.e. its Tg is above the operating temperature) meaning the polymer will remain rigid and is unlikely to extrude. Thus the PVT data implies considerable mechanical performance advantages under HPHT conditions, for components made from the polymeric material.

(43) Additionally, the creep/compression data shows that the depth of the rim for the polymeric material according to the preferred embodiment is considerably less in comparison to PEEK, illustrating a clear performance advantage.

(44) Furthermore, the polymeric material according to the preferred embodiment is found to have chemical resistance under simulated subsea conditions (Example 15) comparable to PEEK, while outperforming PEK.

(45) Thus, overall, the polymeric material according to preferred embodiments is advantageous, showing improved properties compared to existing commercially used materials.

(46) The polymeric materials according to preferred embodiments may be used in challenging situations in the oil and gas industry, for example for seals, back-up rings, plugs and packers, motor winding slot liners, protector thrust bearings, motor pot heads, compressor vanes, bearings and bushes, thrust washers, valve plates and high pressure hoses, downhole sensors, marine risers, subsea umbilicals, hoses and sheaths.

(47) The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.