SULPHIDE STRESS CRACKING RESISTANT STEEL, TUBULAR PRODUCT MADE FROM SAID STEEL, PROCESS FOR MANUFACTURING A TUBULAR PRODUCT AND USE THEREOF

Abstract

The present invention relates to low alloy steels with a high yield strength that present an improved sulphide stress cracking behaviour. The present invention also relates to tubular products, such as tubes or pipes, made from said steel, as well as a process for manufacturing such tubular products. In addition, the present invention concerns use of such tubular products for well drilling and/or for production, extraction and/or transportation of oil and gas.

Claims

1. A steel having a chemical composition consisting of, in weight %, relative to the total weight of said chemical composition: 0.32C<0.46; 0.10Si0.45; 0.10Mn0.50; 0.30Cr1.25; 1.10Mo2.10; 0.10V0.30; 0.01Nb0.10; Fe, and one or more residual elements comprising Cu; and wherein the chemical composition satisfies formula between C, Si, Mn, Cr, Mo, V, Nb and Cu, the contents of which are expressed in weight %:
+1.5*1650 in which, =90+274*C25*Si64*Mn+22*Cr+17*Mo+268*V225*Nb+184*Cu, and =54+162*C86*Si49*Mn31*Cr+22*Mo+20*V172*Nb364*Cu.

2. The steel according to claim 1, having a yield strength greater than or equal to 862 MPa (125 ksi) in standards ASTM A370-17 and ASTM E8/E8M-13a.

3. The steel according to either claim 1, wherein the chemical composition contains in weight %, relative to the total weight of said chemical composition: 0.34C0.44.

4. The steel according to claim 1, wherein the chemical composition contains in weight %, relative to the total weight of said chemical composition: 0.20Mn0.40.

5. The steel according to claim 1, wherein the chemical composition contains in weight %, relative to the total weight of said chemical composition: 0.30Cr1.20.

6. The steel according to claim 1, wherein the chemical composition contains in weight %, relative to the total weight of said chemical composition: 1.10<Mo1.60.

7. The steel according to claim 1, wherein the chemical composition contains in weight %, relative to the total weight of said chemical composition: 0.11V0.25.

8. The steel according to claim 1, wherein the chemical composition contains in weight %, relative to the total weight of said chemical composition: 0.01Nb0.05.

9. The steel according to claim 1, wherein the sum of residual element contents is lower than 0.4% by weight of the total weight of the chemical composition.

10. The steel according to claim 1, having a microstructure made of at least 90% of tempered martensite.

11. A tubular product, made from the steel according to claim 1.

12. A process for manufacturing the tubular product of claim 11, the process comprising: (a) providing a steel having the chemical composition, (b) heating up the steel provided at (a) to a temperature ranging from 1100 to 1300 C., (c) hot forming the steel heated at (b) through hot forming processes, at a temperature ranging from 900 to 1300 C. to obtain a tubular product, (d) cooling down the tubular product obtained at (c) to room temperature, before carrying out the following sequences (e) and (f) at least once: (e) heating up the cooled tubular product to an austenitization temperature (AT) ranging from Ac3 to 1000 C. before keeping said tubular product at the temperature AT during a time comprised between 2 and 60 minutes to obtain an austenitized tubular product, and then cooling said austenitized tubular product down to ambient temperature to obtain a quenched tubular product, and either repeating sequence (e) one more time or carrying out the following sequence (f): (f) heating up the quenched tubular product to a tempering temperature (TT) ranging from 500 C. to Ac1 before keeping said tubular product at the temperature TT during a tempering time (Tt) comprised between 5 and 120 minutes, and then cooling said tubular product down to ambient temperature to obtain a quenched and tempered tubular product; it being understood that: Ac1=72310.7*Mn16.9*Ni+29.1*Si+16.9*Cr+6.38*W+290*As; and Ac3=910203*C15.2*Ni+44.7*Si+104*V+13.1*W+31.5*Mo30*Mn; Ac1 and Ac3 being expressed in C.

13. The process according to claim 12, wherein the sequence (e) is performed at least two times.

14. The process according to claim 12, wherein the sequences (e) and (f) are performed at least two times.

15. The process according to claim 12, wherein the tempering temperature (TT) ranges from 600 C. to Ac1.

16. The process according to claim 12, wherein the tempering time (Tt) is comprised between 10 and 60 minutes.

17. A method, comprising: well drilling, producing, extracting and/or transporting oil and gas with the tubular product according to claim 11.

Description

EXAMPLES

[0149] a) Tested Steels

[0150] The following compositions of steels according to the present invention (A-E) and comparative steels (F-P) have been prepared from the elements indicated in the table 1 below, the amounts of which are expressed as percent by weight, relative to the total weight of the chemical composition. Underlined values in the following table 1 are not in conformance with the invention.

TABLE-US-00001 TABLE 1 tested steels Chemical Composition (Unit: mass %, Balance: Fe and Impurities) Steel C Si Mn Cr V B Mo P S Al N Ti 3.4N Nb Ni Cu W Co A 0.44 0.29 0.31 0.40 0.14 0.0011 1.29 0.008 0.001 0.03 0.004 0.02 0.01 0.03 0.030 0.030 0.04 0.003 B 0.44 0.30 0.30 0.39 0.21 0.0010 1.33 0.008 0.001 0.03 0.004 0.02 0.01 0.03 0.030 0.030 0.04 0.003 C 0.34 0.29 0.30 0.31 0.21 0.0009 1.51 0.008 0.001 0.03 0.004 0.02 0.01 0.03 0.040 0.030 0.04 0.003 D 0.43 0.33 0.31 1.00 0.15 0.0001 1.26 0.011 0.001 0.03 0.004 0.01 0.01 0.04 0.030 0.031 0.04 0.003 E 0.43 0.32 0.31 0.39 0.14 0.0001 1.25 0.011 0.001 0.03 0.004 0.01 0.01 0.03 0.030 0.023 0.04 0.003 F 0.34 0.32 0.31 1.00 0.15 0.0023 1.26 0.002 0.001 0.03 0.004 0.02 0.01 0.03 0.002 0.001 0.01 0.002 G 0.44 1.01 0.31 0.40 0.15 0.0001 1.89 0.011 0.002 0.03 0.004 0.01 0.01 0.03 0.030 0.023 0.04 0.003 H 0 31 0.32 0.28 0.53 0.14 0.0021 1.54 0.006 0.001 0.03 0.004 0.02 0.01 0.03 0.020 0.016 0.04 0.005 I 0.34 0.34 0.32 0.98 0.04 0.0001 1.22 0.009 0.001 0.03 0.005 0.01 0.02 0.08 0.040 0.020 0.01 0.003 J 0.33 0.34 0.78 0.98 0.10 0.0003 1.48 0.011 0.002 0.03 0.006 0.02 0.02 0.03 0.103 0.091 0.01 0.001 K 0.44 0.29 0.30 0.79 0.10 0.0012 0.84 0.008 0.001 0.03 0.004 0.02 0.01 0.03 0.030 0.030 0.04 0.003 L 0 59 0.29 0.31 0.98 0.15 0.0001 1.22 0.008 0.001 0.03 0.005 0.02 0.02 0.03 0.030 0.021 0.00 0.003 M 0.44 0.33 0.31 1.00 0.15 0.0001 1.92 0.011 0.001 0.03 0.004 0.01 0.01 0.03 0.030 0.024 0.53 0.003 N 0.36 0.81 0.20 0.50 0.16 0.0002 1.47 0.009 0.003 0.03 0.006 0.00 0.02 0.07 0.000 0.000 0.62 0.030 O 0.43 0.20 0.17 0.98 0.19 0.0011 1.45 0.007 0.001 0.03 0.003 0.02 0.01 0.03 0.031 0.027 0.04 0.003 P 0.42 0.21 0.46 1.00 0.19 0.0012 1.55 0.007 0.001 0.03 0.003 0.02 0.01 0.03 0.031 0.026 0.04 0.003

[0151] The coefficients and corresponding to each steel (A-P), as well as the result after computing the formula +1.5*165, are mentioned in the table 2 below. Underlined values in the following table 2 are not in conformance with the invention, i.e. the chemical composition of the steel does not satisfy formula (1).

TABLE-US-00002 TABLE 2 Steel Formula 1 A 70 88 29 B 90 90 60 C 64 81 13 D 81 63 20 E 65 86 19 F 51 61 28 G 63 41 29 H 39 71 35 I 12 40 106 J 24 5 124 K 61 66 7 L 124 96 117 M 95 82 60 N 39 41 66 O 109 88 86 P 88 74 40

[0152] b) Protocol

[0153] The steels (A-P) having the chemical compositions described in the table 1 above have been heated and then hot formed into seamless steel pipes of the desired dimensions by hot working using the Mannesmann-plug mill process.

[0154] After hot forming, the seamless steel pipes thus obtained have undergone the following process conditions summarized in the table 3, with:

AT ( C.): Austenitization temperature in C.
At: Austenitization time in minutes
TT: Tempering temperature in C.
Tt: Tempering time in minutes

[0155] The following steps, defined in table 3 and corresponding to steps (e) and (f) of the process of the present invention have been performed twice. In others words, the step of austenitization, cooling and tempering (AT1, At1, cooling A1, TT1, Tt1 and cooling T1) have been repeated (AT2, At2, cooling A2, TT2, Tt2 and cooling T2).

TABLE-US-00003 TABLE 3 process conditions Steel AT1 At1 Cooling A1 TT1 Tt1 Cooling T1 AT2 At2 Cooling A2 TT2 Tt2 Cooling T2 A 880 C. 10 min oil 700 C. 20 min air 880 C. 15 min oil 695 C. 30 min air B 900 C. 10 min oil 700 C. 20 min air 900 C. 15 min oil 710 C. 30 min air C 920 C. 10 min water 700 C. 20 min air 920 C. 15 min water 708 C. 30 min air D 880 C. 10 min water 700 C. 20 min air 880 C. 15 min water 708 C. 30 min air E 880 C. 10 min oil 700 C. 20 min air 880 C. 15 min oil 700 C. 30 min air F 920 C. 10 min water 700 C. 20 min air 940 C. 15 min water 715 C. 30 min air G 930 C. 10 min oil 700 C. 20 min air 930 C. 15 min oil 720 C. 30 min air H 920 C. 10 min water 700 C. 20 min air 920 C. 15 min water 710 C. 30 min air I 920 C. 10 min water 700 C. 20 min air 940 C. 15 min water 690 C. 30 min air J 920 C. 10 min water 700 C. 20 min air 940 C. 15 min water 698 C. 30 min air K 910 C. 10 min oil 700 C. 20 min air 910 C. 15 min oil 710 C. 30 min air L 850 C. 10 min oil 700 C. 20 min air 850 C. 15 min oil 725 C. 30 min air M 880 C. 10 min oil 700 C. 20 min air 880 C. 15 min oil 725 C. 30 min air N 920 C. 10 min water 700 C. 20 min air 940 C. 15 min water 710 C. 30 min air O 880 C. 10 min oil 700 C. 20 min air 880 C. 15 min oil 725 C. 30 min air P 880 C. 10 min oil 700 C. 20 min air 880 C. 15 min oil 725 C. 30 min air

[0156] c) Results

[0157] The microstructure, mechanical behavior and SSC resistance of the seamless steel pipes (A-P) thus obtained are summarized in the following table 4. The SSC resistance of the seamless steel pipes (A-K and N) is also shown in FIG. 1. [0158] PAG is the prior austenite grain size index as defined in standard ASTM E112-13. [0159] YS in MPa and ksi is the yield strength obtained in tensile test as defined in standards ASTM A370-17 and ASTM E8/E8M-13a. [0160] UTS in MPa and ksi is the tensile strength obtained in tensile test as defined in standards ASTM A370-17 and ASTM E8/E8M-13a. [0161] SSC is the sulphide stress corrosion cracking resistance evaluated according standard NACE TM0177-2016 Method A. The SSC test consists in immersing the test specimens under load in an aqueous solution adjusted to pH 3.5 with the addition of acetic acid and sodium acetate in a test solution of 5 mass % NaCl. The solution temperature is 24 C., H.sub.2S is at 0.1 atm., CO2 is at 0.9 atm. The testing duration is 720 hours, and the applied stress is 90% of the yield strength. A successful test implies no failure on the specimens after 720 hours.

TABLE-US-00004 TABLE 4 results obtained for the seamless steel pipes (A-P) PAG YS UTS Steel (ASTM) Microstructure (MPa) (MPa) SSC A 12.0 Tempered Martensite 968 1010 Pass B 12.0 Tempered Martensite 940 983 Pass C 12.0 Tempered Martensite 955 993 Pass D 13.0 Tempered Martensite 961 1019 Pass E 13.0 Tempered Martensite 929 975 Pass F 12.0 Tempered Martensite 917 989 Fail G 12.5 Tempered Martensite 877 947 Fail H 12.0 Tempered Martensite 906 961 Fail I 12.0 Tempered Martensite 915 991 Fail J 10.5 Tempered Martensite 887 982 Fail K 11.0 Tempered Martensite 928 992 Fail L 13.0 Tempered Martensite 948 990 Fail M 13.0 Tempered Martensite 874 909 Fail N 13.0 Tempered Martensite 883 945 Fail O 13.0 Tempered Martensite 904 941 Fail P 12.0 Tempered Martensite 900 945 Fail

[0162] The results thus obtained show that the steels according to the present invention (A-E), having particular contents of C, Si, Mn, Cr, Mo, V and Nb and satisfying formula (1), present a better yield strength as well as a better sulphide stress cracking resistance than comparative steels (F-P).

[0163] As displayed in FIG. 1, surprisingly, comparative steels (G-K and N) having elements contents outside the composition ranges of the invention and having chemical compositions that do not satisfy formula (1), exhibit lower yield strength and worse sulphide stress cracking resistance than steels according to the present invention (A-E). Furthermore, the inventors were flabbergasted to observe that comparative steel F having elemental contents within the composition ranges of the invention but having a chemical composition that does not satisfy formula (1), also exhibit lower yield strength and worse sulphide stress cracking resistance than steels according to the present invention (A-E).

[0164] Astonishingly, comparative examples (M, O and P) having chemical compositions that do satisfy formula (1), but having contents outside the composition ranges of the invention, also exhibit lower yield strength and worse sulphide stress cracking resistance than steels according to the present invention (A-E).