CN115572900B - Sulfide stress corrosion resistant oil casing and preparation method thereof - Google Patents

Abstract

The invention discloses an oil sleeve for resisting sulfide stress corrosion and a preparation method thereof, wherein the oil sleeve for resisting sulfide stress corrosion comprises the following chemical components in percentage by mass: 0.21 to 0.26 percent of C, 0.19 to 0.39 percent of Si, 0.65 to 0.75 percent of Mn, 0.95 to 1.05 percent of Cr, 0.35 to 0.55 percent of Mo or 0.70 to 1.10 percent of W, 0 to 0.25 percent of Ni, 0 to 0.25 percent of Cu, 0.035 to 0.065 percent of Nb or 0.035 to 0.065 percent of V, 0.005 to 0.010 percent of RE, 0.006 to 0.018 percent of Al, 0.006 to 0.010 percent of Ca, less than or equal to 0.012 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.002 percent of O, less than or equal to 0.00015 percent of H, less than or equal to 0.003 percent of N, and the balance of Fe and unavoidable impurities. Wherein Mo/P is more than or equal to 25 or W/P is more than or equal to 50; al/N is more than or equal to 2; (Ca+RE)/S is more than or equal to 3. The oil casing pipe resistant to sulfide stress corrosion provided by the invention has the advantages of high yield strength, good toughness and good sulfide stress corrosion resistance, the room temperature yield strength is more than 552-862 MPa, the tensile strength is more than 655-931 MPa, the total elongation is more than or equal to 14-18%, the Charpy impact toughness is more than or equal to 100J, and no fracture occurs in a NACE TM 0177A method hydrogen sulfide stress corrosion test for 720 hours, so that the comprehensive performance requirement of oil gas development in an acidic environment on the oil casing pipe can be met.

Description

Sulfide stress corrosion resistant oil casing and preparation method thereof

Technical Field

The invention relates to the technical field of oil casing, and in particular to an oil casing resistant to sulfide stress corrosion and a preparation method thereof.

Background Art

Acidic oil and gas account for a large proportion of my country's oil and gas resources, mainly distributed in oil and gas fields such as Southwest, Tarim, Daqing, Changqing, Dagang, and North China. In a hydrogen sulfide environment, steel materials are prone to sulfide stress corrosion damage under the synergistic effect of corrosive media and working stress, which often leads to serious consequences. The higher the strength of the steel material, the greater the probability of sulfide stress corrosion damage. With the development of deep wells, ultra-deep wells, and highly acidic oil and gas fields, not only are there high requirements for the strength and toughness of oil casing (tubings and casings), but also for the resistance to hydrogen sulfide corrosion, especially the resistance to hydrogen sulfide stress corrosion. The strength, toughness, and resistance to sulfide stress corrosion of steel materials often show a trade-off relationship, which makes the manufacture of high-strength oil casing and casing with resistance to sulfide stress corrosion very difficult.

Therefore, the prior art still needs to be improved and developed.

Summary of the invention

In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an oil casing and tubing resistant to sulfide stress corrosion and a preparation method thereof, aiming to solve the problem that the comprehensive performance of the existing oil casing and tubing, such as sulfide stress corrosion resistance, strength, toughness, etc., needs to be improved.

The technical solution of the present invention is as follows:

In a first aspect of the present invention, there is provided an oil casing and tubing resistant to sulfide stress corrosion, wherein the oil casing and tubing resistant to sulfide stress corrosion comprises the following chemical components by mass percentage:

C 0.21%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo 0.35%～0.55% or W 0.70%～1.10%, Ni 0～0.25%, Cu 0 ~0.25%, Nb0.035%~0.065% or V 0.035%~0.065%, RE 0.005%~0.010%, Al 0.006%~0.018%, Ca 0.006%～0.010%, P≤0.012%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥25 or W /P≥50;Al/N≥2;(Ca+RE)/S≥3.

Optionally, the sulfide stress corrosion resistant oil casing comprises the following chemical components in terms of mass percentage:

C 0.21%～0.24%, Si 0.21%～0.37%, Mn 0.68%～0.73%, Cr 0.96%～1.03%, Mo 0.35%～0.40% or W 0.70%%, Nb 0.035%～0.040% or V 0.035% ~0.038%, RE 0.005% ~ 0.010%, Al 0.006% ~ 0.011%, Ca 0.006%～0.010%, P≤0.011%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35 or W /P≥70;Al/N≥2;(Ca+RE)/S≥3.

Optionally, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.21%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo 0.35%～0.55% or W 0.70%～1.10%, Ni 0.18～0.25%, Cu 0.17 ~0.25%, Nb0.035%~0.065% or V 0.035%~0.065%, RE 0.005%~0.010%, Al 0.006%~0.018%, Ca 0.006%～0.010%, P≤0.012%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥25 or W /P≥50;Al/N≥2;(Ca+RE)/S≥3.

Optionally, the sulfide stress corrosion resistant oil casing comprises the following chemical components in terms of mass percentage:

C 0.22%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo 0.44%～0.55% or W 0.91%～1.10%, Ni 0.18～0.25%, Cu 0.17 ~0.25%, Nb0.059%~0.065% or V 0.060%~0.065%, RE 0.006%~0.009%, Al 0.012%~0.018%, Ca 0.007%～0.010%, P≤0.012%, S≤0.001%, O≤0.0019%, H≤0.00013%, N≤0.002%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35 or W /P≥90;Al/N≥2;(Ca+RE)/S≥10.

A second aspect of the present invention provides a method for preparing an oil casing resistant to sulfide stress corrosion, comprising the steps of:

The chemical components of the oil casing pipe resistant to sulfide stress corrosion as described above are prepared, smelted and continuously cast to obtain a continuously cast billet;

The continuous casting billet is subjected to perforation and hot continuous rolling to obtain a tube billet;

The tube blank is subjected to two tempering heat treatments to obtain the sulfide stress corrosion resistant oil casing.

Optionally, after smelting and continuous casting, the step of obtaining the continuous casting billet specifically includes:

The raw materials obtained by batching are sequentially smelted in an electric furnace or an oxygen-blown converter, fed with rare earth wire, refined outside the furnace, vacuum degassed, and fed with Si-Ca wire to denature inclusions to obtain molten steel;

The molten steel is cast into a rod-shaped continuous casting billet.

Optionally, the step of obtaining a tube billet after piercing and hot rolling the continuous casting billet specifically includes:

The continuous casting billet is heated to 1250-1280° C. in a heating furnace, kept warm for 90-120 minutes, then hot-pierced at 1200-1250° C., hot-rolled at 980-1180° C., and cooled to obtain a tube billet.

Optionally, the step of subjecting the tube blank to two tempering heat treatments to obtain the sulfide stress corrosion resistant oil casing specifically includes:

In a protective atmosphere furnace, the tube blank is first quenched at a temperature of 925-945° C., kept at this temperature for 40-60 minutes and then cooled, then first tempered at a temperature of 655-665° C., kept at this temperature for 90-120 minutes and then water-cooled, then hot straightened at a temperature of 600-640° C. and then water-cooled;

Then, the second quenching is performed at a temperature of 890-910°C, and the heat preservation is performed for 40-60 minutes before cooling. Then, the second tempering is performed at a temperature of 600-680°C, and the heat preservation is performed for 90-120 minutes before water cooling. Then, hot straightening is performed at a temperature of 530-610°C, and after water cooling, stress relief tempering is performed at a temperature of 550-630°C to obtain the oil casing resistant to sulfide stress corrosion.

Optionally, the tube blank is first quenched at a temperature of 925-945° C., kept at this temperature for 40-60 minutes, and then cooled at a cooling rate of 20-30° C./s;

and/or,

Then carry out a second quenching at a temperature of 890-910°C, keep warm for 40-60 minutes, and then cool at a cooling rate of 20-30°C/s.

Optionally, after the tube blank is subjected to two tempering heat treatments, before the sulfide stress corrosion resistant oil casing is obtained, the step of:

The pipe blank is threaded after two tempering heat treatments.

Beneficial effects: The sulfide stress corrosion resistant oil casing provided by the present invention has high yield strength, good toughness and good sulfide stress corrosion resistance, and its yield strength level can reach 80ksi, 95ksi, 110ksi, and 125ksi requirements respectively. Its room temperature yield strength is greater than 552-862MPa, tensile strength is greater than 655-931MPa, total elongation is ≥14-18%, Charpy impact toughness is ≥100J, and NACE TM 0177A method hydrogen sulfide stress corrosion test does not break for 720 hours, which can meet the comprehensive performance requirements of oil casing for oil and gas development in acidic environment.

DETAILED DESCRIPTION

The present invention provides an oil casing and casing resistant to sulfide stress corrosion and a preparation method thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

An embodiment of the present invention provides an oil casing and tubing resistant to sulfide stress corrosion, wherein the oil casing and tubing resistant to sulfide stress corrosion comprises the following chemical components in terms of mass percentage:

C 0.21% to 0.26%, Si 0.19% to 0.39%, Mn 0.65% to 0.75%, Cr 0.95% to 1.05%, Mo 0.35% to 0.55% or W 0.70% to 1.10%, Ni 0 to 0.25%, Cu 0 to 0.25%, Nb 0.035% to 0.065% or V 0.035% to 0.065%, RE (rare earth element) 0.005% to 0.010%, Al 0.006% to 0.018%, Ca 0.006%～0.010%, P≤0.012%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥25 or W/P≥50; Al/N≥2; (Ca+RE)/S≥3.

In terms of composition design, the embodiments of the present invention comprehensively consider the strength, toughness, corrosion resistance, process performance, safety, reliability and economy of the oil casing, adopt medium and low C content, control the Mn content, add Cr, Mo or W, Nb or V for micro-alloying, and may also add a small amount of Ni and Cu, and add rare earth elements (RE), control the content of harmful elements such as P, S, O, H, N in the steel, adopt Al, Si fully deoxidized killed steel, and perform Ca treatment on the molten steel. The present invention creatively designs the chemical composition and content of the oil casing, so that the elements produce synergistic effects, and finally the obtained sulfide stress corrosion resistant oil casing has high strength, good toughness (toughness is the guarantee of safe service of steel materials) and sulfide stress corrosion resistance, that is, the present invention obtains high toughness and sulfide stress corrosion resistance on the premise of ensuring that the oil casing has high strength. Its yield strength levels can reach 80ksi, 95ksi, 110ksi, and 125ksi requirements respectively, the room temperature yield strength is greater than 552-862MPa, the tensile strength is greater than 655-931MPa, the total elongation is ≥14-18%, the Charpy impact toughness is ≥100J, and the NACETM 0177A method hydrogen sulfide stress corrosion test does not break for 720 hours, which can meet the comprehensive performance requirements of oil casing and tubing for oil and gas development in sour environments.

Among them, C is the most important strengthening element. Too low a content is not conducive to improving strength, while too high a content is not conducive to toughness and corrosion resistance. In the embodiment of the present invention, its content is controlled within 0.21% to 0.26% according to the performance requirements and uses of the oil casing.

Si is a common element in steel, which has the functions of reducing and deoxidizing. It is also one of the effective elements to ensure the strength of oil casing, and has an important influence on strength and toughness, because Si can improve the hardness and strength of the solid solution in steel and increase the hardenability of steel. However, too high silicon content will deteriorate the thermal conductivity of steel, making the steel prone to crack curves. Therefore, in the embodiment of the present invention, the content of Si is controlled at 0.19% to 0.35% according to the performance requirements and uses of the oil casing.

Mn is mainly used to improve the hardenability of steel, thereby improving the strength of steel, but it has a large tendency to segregate and is easy to form Mn inclusions with S, which is unfavorable to the toughness and corrosion resistance of steel. It must be strictly controlled. In the embodiment of the present invention, the Mn content is controlled at 0.65% to 0.75% according to the performance requirements and use of the oil casing.

Cr is mainly used to improve the hardenability of steel, thereby improving the strength and tempering stability of steel. In the embodiment of the present invention, the content of Cr is controlled within a range of 0.95% to 1.05% according to the performance requirements and use of the oil casing.

Mo is mainly used to improve the hardenability of steel, thereby improving the strength and tempering stability of steel. In the embodiment of the present invention, the content of Mo is controlled within a range of 0.35% to 0.55% according to the performance requirements and use of the oil casing.

W is mainly used to improve the hardenability of steel, thereby improving the strength and tempering stability of steel. In the embodiment of the present invention, the content of W is controlled within a range of 0.70% to 1.10% according to the performance requirements and use of the oil casing.

Specifically, Cr, Mo, and W are strong carbide-forming elements. Carbides containing Cr and Mo or W are formed during the tempering of martensite, which can improve the hardenability, strength, and tempering stability of steel.

Cu is mainly used to improve the corrosion resistance of steel, and can also improve the hardenability and strength of steel. However, too high a content will also cause Cu brittleness. In the embodiment of the present invention, the Cu content is controlled within 0-0.25% according to the performance requirements and use of the oil casing.

Ni is mainly used to improve the hot brittleness that may be caused by the addition of Cu, and can also improve the hardenability of steel, thereby improving the strength and toughness of steel. In the embodiment of the present invention, the content of Ni is controlled at 0-0.25% according to the performance requirements and use of the oil casing.

Specifically, the addition of a small amount of Cu can improve the corrosion resistance of steel, and the addition of Ni can also improve the toughness of steel, while neutralizing the hot brittleness that may be caused by the Cu element. The addition of Cu and Ni improves the tempering stability and corrosion resistance of steel and improves the hot working process performance. In the embodiment of the present invention, a small amount of Cu and Ni are added to the high-grade steel casing to ensure that its corrosion resistance meets the design requirements.

Nb and V are strong carbide-forming elements. In addition to improving the hardenability of steel, their carbides are evenly distributed in the steel, which can hinder the growth of austenite grains to refine the grains and play a role in dispersion strengthening. Nb is added to the steel and forms NbC and NbN with C and N in the steel, which have the effect of hindering the growth of austenite grains and refining the grains, thereby improving the strength and toughness. V is added to the steel and forms VC and VN with C and N in the steel, which have the effect of hindering the growth of austenite grains and refining the grains, thereby improving the strength and toughness. In the embodiment of the present invention, one of Nb and V is selected for addition, and the content of Nb is controlled to be 0.035% to 0.065% or the content of V is controlled to be 0.035% to 0.065% to improve the hardenability of the steel, refine the grains, and thus improve the strength and toughness of the steel.

Al is an important deoxidizer. It forms oxides with oxygen to deoxidize. It forms nitrides with nitrogen to partially eliminate the adverse effects of N. It also refines grains and improves strength and toughness. It is best to control it at 0.006% to 0.018%.

Ca can improve the properties and morphology of inclusions, make the inclusions spherical and form composite inclusions, thereby reducing the brittleness of steel and improving the toughness and corrosion resistance of steel. In the embodiment of the present invention, the content of Ca is controlled at 0.006% to 0.010% according to the performance requirements and use of the oil casing.

RE element has multiple functions of purifying molten steel, refining grains, modifying inclusions, and alloying. It is a strong oxidant with deoxidation and desulfurization effects. At the same time, it can form compounds with hydrogen in steel, which can reduce the solid solution content of O, S, and H in steel, which is beneficial to improving the toughness and corrosion resistance of steel. Adding RE element to steel can transform sulfide, oxide, silicate and other inclusions in steel into composite inclusions such as rare earth sulfide, rare earth oxide, rare earth silicate, etc., spheroidize the original inclusions and reduce the brittleness of the original inclusions, all of which are beneficial to improving The toughness and corrosion resistance of steel; and the RE element can form high-melting-point compounds with harmful impurity elements such as Pb, Sn, Sb, As, Bi in steel, which plays a role in purifying molten steel, and is also beneficial to improving the toughness and corrosion resistance of steel; at the same time, it can refine the cast structure, reduce dendrite segregation, reduce the aggregation of eutectic carbides, and reduce the anisotropy of steel; RE can also improve the process properties of steel such as fluidity. In the embodiment of the present invention, the content of RE is controlled at 0.005% to 0.010% according to the performance requirements and uses of the oil casing.

P, S, O, H, and N are harmful elements, which mainly affect the plasticity, toughness, and corrosion resistance of steel. By controlling the harmful elements P, S, O, H, and N in steel, it is beneficial to improve the purity of steel and thus improve the toughness and corrosion resistance of oil casing. Specifically, the high N content is easy for Nb in the steel to form NbN, which increases the brittleness of the steel and is not conducive to improving the toughness of the oil casing. At the same time, the inventor has found through a large number of studies that harmful impurity elements such as P, S, O, H, and N have a great influence on the toughness and corrosion resistance of steel, and their contents need to be strictly controlled. Therefore, the P content is controlled at ≤0.012%, the S content is controlled at ≤0.003%, the O content is controlled at ≤0.002%, the H content is controlled at ≤0.00015%, and the N content is controlled at ≤0.003%.

Strictly control Mo/P or W/P so that Mo/P ≥ 25 (i.e., the ratio of Mo mass percentage to P mass percentage is greater than or equal to 25) or W/P ≥ 50 (i.e., the ratio of W mass percentage to P mass percentage is greater than or equal to 50) to control P segregation to ensure the uniformity of the composition of the casing and its corrosion resistance; strictly control Al/N ≥ 2 (i.e., the ratio of Al mass percentage to N mass percentage is greater than or equal to 2) to eliminate the adverse effects of N on toughness and corrosion resistance; strictly control (Ca+RE)/S ≥ 3 (i.e., the ratio of the sum of Ca mass percentage to RE mass percentage to S mass percentage is greater than or equal to 3) to control the sulfide inclusion modification treatment effect to further improve the toughness and corrosion resistance of the steel.

In one embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.21%～0.24%, Si 0.21%～0.37%, Mn 0.68%～0.73%, Cr 0.96%～1.03%, Mo 0.35%～0.40% or W 0.70%%, Nb 0.035%～0.040% or V 0.035% ~0.038%, RE 0.005% ~ 0.010%, Al 0.006% ~ 0.011%, Ca 0.006%～0.010%, P≤0.011%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35 or W /P≥70;Al/N≥2;(Ca+RE)/S≥3.

In this embodiment, the yield strength of the sulfide stress corrosion resistant oil casing can reach 80ksi or 95ksi, the room temperature yield strength is 589-719MPa, the tensile strength is 693-799MPa, the elongation is 25-29%, the Charpy impact toughness is ≥120J, and it can meet the NACE TM 0177A method 95% yield strength stress level (super sulfur resistant SS) 720 hours test without fracture requirements.

In a further embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.21%～0.22%, Si 0.28%～0.32%, Mn 0.70%～0.73%, Cr 0.96%～0.98%, Mo 0.37%～0.39%, Nb 0.040%, RE 0.005%～0.007%, Al 0.006%～0.008%, Ca 0.006%, P≤0.011%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35; Al/N≥2; (Ca+RE)/S≥3.

In this embodiment, the yield strength of the sulfide stress corrosion resistant oil casing can reach 80ksi, the room temperature yield strength is 589-595MPa, the tensile strength is 693-701MPa, the elongation is 28-29%, the Charpy impact toughness is ≥130J, and it can meet the NACE TM 0177A method 95% yield strength stress level (super sulfur resistant SS) 720 hours test without fracture requirements.

In a further embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.22%～0.24%, Si 0.21%～0.37%, Mn 0.68%～0.72%, Cr 1.01%～1.03%, Mo 0.35%～0.40%, Nb 0.035%～0.038%, RE 0.006%～0.010%, Al 0.009%～0.011%, Ca 0.007%～0.010%, P≤0.010%, S≤0.003%, O≤0.0017%, H≤0.00014%, N≤0.002%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35; Al/N≥2; (Ca+RE)/S≥3.

In this embodiment, the yield strength of the sulfide stress corrosion resistant oil casing can reach 95ksi, the room temperature yield strength is 703-719MPa, the tensile strength is 779-799MPa, the elongation is 25-26%, the Charpy impact toughness is ≥120J, and it can meet the NACE TM 0177A method 95% yield strength stress level (super sulfur resistant SS) 720 hours test without fracture requirements.

In one embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by weight percentage:

C 0.21%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo 0.35%～0.55% or W 0.70%～1.10%, Ni 0.18～0.25%, Cu 0.17 ~0.25%, Nb0.035%~0.065% or V 0.035%~0.065%, RE 0.005%~0.010%, Al 0.006%~0.018%, Ca 0.006%～0.010%, P≤0.012%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and unavoidable impurities; among which, Mo/P≥25 or W /P≥50;Al/N≥2;(Ca+RE)/S≥3.

In one embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.22%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo 0.44%～0.55% or W 0.91%～1.10%, Ni 0.18～0.25%, Cu 0.17 ~0.25%, Nb0.059%~0.065% or V 0.060%~0.065%, RE 0.006%~0.009%, Al 0.012%~0.018%, Ca 0.007%～0.010%, P≤0.012%, S≤0.001%, O≤0.0019%, H≤0.00013%, N≤0.002%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35 or W /P≥90;Al/N≥2;(Ca+RE)/S≥10.

In this embodiment, the yield strength of the sulfide stress corrosion resistant oil casing can reach 110ksi or 125ksi, the room temperature yield strength is 786-925MPa, the tensile strength is 821-984MPa, the elongation is 19-24%, the Charpy impact toughness is ≥100J, and it can meet the requirement of no fracture in the 720-hour test of 85% yield strength stress level (ordinary sulfur resistance S) of NACE TM 0177A method.

In a further embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.22%～0.25%, Si 0.30%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～0.98%, Mo 0.44%～0.48% or W0.91%, Ni 0.182～0.21%, Cu 0.171～0.20%, Nb0.059% or V 0.060%～0.065%, RE 0.007%～0.009%, Al 0.012%～0.015%, Ca0.007%～0.010%, P≤0.012%, S≤0.0010%, O≤0.0017%, H≤0.00013%, N≤0.002%, the balance is Fe and unavoidable impurities; among which, Mo/P≥35 or W/P≥90; Al/N≥2; (Ca+Re)/S≥10.

In this embodiment, the yield strength of the sulfide stress corrosion resistant oil casing can reach 110ksi, the room temperature yield strength is 786-796MPa, the tensile strength is 821-835MPa, the elongation is 23-24%, the Charpy impact toughness is ≥110J, and it can meet the requirement of no fracture in the 720-hour test of 95% yield strength stress level (super sulfur resistant SS) of NACE TM 0177A method. In this embodiment, while ensuring the high strength and high toughness of the oil casing, it still has good sulfide stress corrosion resistance.

In a further embodiment, the sulfide stress corrosion resistant oil casing comprises the following chemical components by mass percentage:

C 0.24%～0.26%, Si 0.19%～0.35%, Mn 0.66%～0.72%, Cr 0.97%～1.05%, Mo 0.53%～0.55% or W1.10%, Ni 0.22～0.25%, Cu 0.21～0.25%, Nb 0.065% or V 0.061%～0.063%, RE 0.006%～0.009%, Al 0.016%～0.018%, Ca 0.008%～0.009%, P≤0.010%, S≤0.0009%, O≤.0019%, H≤0.00012%, N≤0.002%, the balance is Fe and unavoidable impurities; among which, Mo/P≥50 or W/P≥100; Al/N≥2; (Ca+Re)/S≥15.

In this embodiment, the yield strength of the sulfide stress corrosion resistant oil casing can reach 125ksi, the room temperature yield strength is 875-925MPa, the tensile strength is 959-984MPa, the elongation is 19-21%, the Charpy impact toughness is ≥100J, and it can meet the requirement of no fracture in the 720-hour test of 85% yield strength stress level (ordinary sulfur resistance S) of NACE TM 0177A method. In this embodiment, while ensuring the high strength and high toughness of the oil casing, it still has good sulfide stress corrosion resistance.

In addition to the reasonable design of chemical composition and proportion content, the excellent comprehensive performance of the oil casing and tubing also requires the manufacturing process to affect the final performance of the oil casing and tubing. Different chemical composition designs require the use of different manufacturing processes to enable the oil casing and tubing to exert the best performance. The present invention develops a manufacturing process that matches the chemical composition of the above-mentioned proportion content, mainly through steelmaking (including refining outside the furnace, vacuum degassing), continuous casting, hot rolling in the austenite zone, two tempering heat treatments, heat straightening, stress relief tempering and other processes, so that the material obtains a fine and uniform tempered troostite microstructure, and effectively reduces the residual stress, so as to achieve a reasonable match of the strength, toughness, and hydrogen sulfide stress corrosion resistance of the oil casing and tubing. Specifically, an embodiment of the present invention also provides a method for preparing an oil casing and tubing resistant to sulfide stress corrosion, which includes the steps of:

S1. The components of the oil casing and casing resistant to sulfide stress corrosion according to the present invention are mixed, smelted and continuously cast to obtain a continuously cast billet;

S2, performing perforation and hot rolling on the continuous casting billet to obtain a tube billet;

S3, performing two tempering heat treatments on the tube blank to obtain the oil casing and tubing resistant to sulfide stress corrosion.

The chemical composition and manufacturing process of the embodiment of the present invention are used in combination to achieve the effects of increasing strength, improving toughness, reducing residual stress, and improving corrosion resistance.

The preparation method of the present invention is aimed at the oil casing with the above chemical composition, obtains the expected organizational structure and performance, gives full play to the performance of the oil casing, has low cost, and the process parameters in the process are easy to control, and the obtained oil casing has stable performance.

In step S1, materials including but not limited to molten iron, scrap steel, etc. may be used as raw materials, and required alloy elements may be added during smelting.

In one embodiment, the step of obtaining the continuous casting billet after smelting and continuous casting specifically includes:

The raw materials obtained by batching are sequentially smelted in an electric furnace or an oxygen-blown converter, fed with rare earth wire, refined outside the furnace, vacuum degassed, and fed with Si-Ca wire to denature inclusions to obtain molten steel;

The molten steel is cast into a rod-shaped continuous casting billet.

In step S2, in one embodiment, the step of obtaining a tube billet after piercing and hot rolling the continuous casting billet specifically includes:

The continuous casting billet is heated to 1250-1280° C. in a heating furnace, kept warm for 90-120 minutes, then hot-pierced at 1200-1250° C., hot-rolled at 980-1180° C., and cooled to obtain a tube billet. Specifically, the tube billet can be sawed to a preset length according to actual needs.

In step S3, in one embodiment, the step of subjecting the tube blank to two tempering heat treatments to obtain the sulfide stress corrosion resistant oil casing specifically includes:

In a protective atmosphere furnace (to prevent decarburization), the tube blank is first quenched at a temperature of 925-945°C, kept at this temperature for 40-60 minutes, and then cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching, and then first tempered at a temperature of 655-665°C, kept at this temperature for 90-120 minutes, and then water-cooled to obtain fine and uniform tempered troostite with a grain size of 8-9, and water-cooled after tempering to avoid possible temper brittleness, and then hot straightened at a temperature of 600-640°C and then water-cooled;

Then, the second quenching is performed at a temperature of 890-910°C, and after keeping the temperature for 40-60 minutes, the steel is cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching. Then, the second tempering is performed at a temperature of 600-680°C, and after keeping the temperature for 90-120 minutes, the steel is water-cooled to obtain fine and uniform tempered troostite with a grain size of 9-10. Then, the steel is heat-straightened at a temperature of 530-610°C, and after water-cooling, the steel is stress-relieved and tempered at a temperature of 550-630°C to effectively eliminate the residual stress, thereby obtaining the oil casing and tubing resistant to sulfide stress corrosion. Among them, the tempering temperature, the heat-straightening temperature, and the stress-relieved and tempered temperature can be adjusted according to the steel grade.

In this embodiment, through the heat treatment process of double quenching + high temperature tempering and multiple recrystallization, the grains and structure are refined, and finally fine and uniform tempered troostite with a grain size of 9 to 10 can be obtained, thereby improving the strength, toughness and corrosion resistance of the oil casing.

Specifically, when the oil casing and casing resistant to sulfide stress corrosion comprises the following components in percentage by mass: C 0.21% to 0.22%, Si 0.28% to 0.32%, Mn 0.70% to 0.73%, Cr 0.96% to 0.98%, Mo 0.37% to 0.39%, Nb 0.040%, RE 0.005% to 0.007%, Al 0.006% to 0.008%, Ca 0.006%, P≤0.011%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, and the balance is Fe and unavoidable impurities; wherein Mo/P≥35; Al/N≥2; (Ca+RE)/S≥3. The steps of subjecting the tube blank to two tempering heat treatments to obtain the oil casing pipe resistant to sulfide stress corrosion specifically include:

In a protective atmosphere furnace (to prevent decarburization), the tube blank is first quenched at a temperature of 925-945°C, kept at this temperature for 40-60 minutes, and then cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching, and then first tempered at a temperature of 655-665°C, kept at this temperature for 90-120 minutes, and then water-cooled to obtain fine and uniform tempered troostite with a grain size of 8-9, and water-cooled after tempering to avoid possible temper brittleness, and then hot straightened at a temperature of 600-640°C and then water-cooled;

Then, the second quenching is performed at a temperature of 890-910°C, and after keeping the temperature for 40-60 minutes, the product is cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching. Then, the second tempering is performed at a temperature of 660-680°C, and after keeping the temperature for 90-120 minutes, the product is water-cooled to obtain fine and uniform tempered troostite with a grain size of 9-10. Then, hot straightening is performed at a temperature of 590-610°C, and after water cooling, stress relief tempering is performed at a temperature of 610-630°C to effectively eliminate residual stress, thereby obtaining the oil casing and casing resistant to sulfide stress corrosion.

Specifically, when the sulfide stress corrosion resistant oil casing comprises the following components in percentage by mass: C 0.22% to 0.24%, Si 0.21% to 0.37%, Mn 0.68% to 0.72%, Cr 1.01% to 1.03%, Mo 0.35% to 0.40%, Nb 0.035% to 0.038%, RE 0.006% to 0.010%, Al 0.009% to 0.011%, Ca 0.007% to 0.010%, P ≤ 0.010%, S ≤ 0.003%, O ≤ 0.0017%, H ≤ 0.00014%, N ≤ 0.002%, the balance is Fe and unavoidable impurities; wherein, Mo/P ≥ 35; Al/N ≥ 2; (Ca+RE)/S ≥ 3. The steps of subjecting the tube blank to two tempering heat treatments to obtain the oil casing pipe resistant to sulfide stress corrosion specifically include:

In a protective atmosphere furnace (to prevent decarburization), the tube blank is first quenched at a temperature of 925-945°C, kept at this temperature for 40-60 minutes, and then cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching, and then first tempered at a temperature of 655-665°C, kept at this temperature for 90-120 minutes, and then water-cooled to obtain fine and uniform tempered troostite with a grain size of 8-9, and water-cooled after tempering to avoid possible temper brittleness, and then hot straightened at a temperature of 600-640°C and then water-cooled;

Then, the second quenching is performed at a temperature of 890-910°C, and after keeping the temperature for 40-60 minutes, the product is cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching. Then, the second tempering is performed at a temperature of 640-660°C, and after keeping the temperature for 90-120 minutes, the product is water-cooled to obtain fine and uniform tempered troostite with a grain size of 9-10. Then, hot straightening is performed at a temperature of 570-590°C, and after water cooling, stress relief tempering is performed at a temperature of 590-610°C to effectively eliminate residual stress, thereby obtaining the oil casing and casing resistant to sulfide stress corrosion.

Specifically, when the oil casing and tubing resistant to sulfide stress corrosion comprises the following components, measured by mass percentage: C 0.22% to 0.25%, Si 0.30% to 0.39%, Mn 0.65% to 0.75%, Cr 0.95% to 0.98%, Mo 0.44% to 0.48% or W 0.91%, Ni 0.182 to 0.21%, Cu 0.171 to 0.20%, Nb 0.059% or V 0.060% to 0.065%, RE 0.007% to 0.009%, Al 0.012% to 0.015%, Ca 0.007% to 0.010%, P≤0.012%, S≤0.0010%, O≤0.0017%, H≤0.00013%, N≤0.002%, the balance is Fe and unavoidable impurities; wherein, Mo/P≥35 or W/P≥90; Al/N≥2; (Ca+Re)/S≥10. The steps of subjecting the tube blank to two tempering heat treatments to obtain the sulfide stress corrosion resistant oil casing specifically include:

In a protective atmosphere furnace (to prevent decarburization), the tube blank is first quenched at a temperature of 925-945°C, kept at this temperature for 40-60 minutes, and then cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching, and then first tempered at a temperature of 655-665°C, kept at this temperature for 90-120 minutes, and then water-cooled to obtain fine and uniform tempered troostite with a grain size of 8-9, and water-cooled after tempering to avoid possible temper brittleness, and then hot straightened at a temperature of 600-640°C and then water-cooled;

Then, the second quenching is performed at a temperature of 890-910°C, and after keeping the temperature for 40-60 minutes, the product is cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching. Then, the second tempering is performed at a temperature of 620-640°C, and after keeping the temperature for 90-120 minutes, the product is water-cooled to obtain fine and uniform tempered troostite with a grain size of 9-10. Then, hot straightening is performed at a temperature of 550-570°C, and after water cooling, stress relief tempering is performed at a temperature of 570-590°C to effectively eliminate residual stress, thereby obtaining the oil casing and casing resistant to sulfide stress corrosion.

Specifically, when the oil casing and tubing resistant to sulfide stress corrosion comprises the following components, measured by mass percentage: C 0.24% to 0.26%, Si 0.19% to 0.35%, Mn 0.66% to 0.72%, Cr 0.97% to 1.05%, Mo 0.53% to 0.55% or W 1.10%, Ni 0.22% to 0.25%, Cu 0.21% to 0.25%, Nb 0.065% or V 0.061% to 0.063%, RE 0.006% to 0.009%, Al 0.016% to 0.018%, Ca 0.008% to 0.009%, P≤0.010%, S≤0.0009%, O≤.0019%, H≤0.00012%, N≤0.002%, the balance is Fe and unavoidable impurities; wherein, Mo/P≥50 or W/P≥100; Al/N≥2; (Ca+Re)/S≥15. The steps of subjecting the tube blank to two tempering heat treatments to obtain the sulfide stress corrosion resistant oil casing specifically include:

In a protective atmosphere furnace (to prevent decarburization), the tube blank is first quenched at a temperature of 925-945°C, kept at this temperature for 40-60 minutes, and then cooled at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching, and then first tempered at a temperature of 655-665°C, kept at this temperature for 90-120 minutes, and then water-cooled to obtain fine and uniform tempered troostite with a grain size of 8-9, and water-cooled after tempering to avoid possible temper brittleness, and then hot straightened at a temperature of 600-640°C and then water-cooled;

Then, the second quenching is performed at a temperature of 890-910°C, and after keeping the temperature for 40-60 minutes, the cooling is performed at a cooling rate of 20-30°C/s to ensure that all martensitic structures are basically obtained after quenching. Then, the second tempering is performed at a temperature of 600-620°C, and after keeping the temperature for 90-120 minutes, water cooling is performed to obtain fine and uniform tempered troostite with a grain size of 9-10. Then, hot straightening is performed at a temperature of 530-550°C, and after water cooling, stress relief tempering is performed at a temperature of 550-570°C to effectively eliminate residual stress, so as to obtain the oil casing and casing resistant to sulfide stress corrosion.

In one embodiment, after the tube blank is subjected to two tempering heat treatments, before the sulfide stress corrosion resistant oil casing is obtained, the following steps are further included:

The pipe blank is threaded after two tempering heat treatments.

In this embodiment, API standard threads or special threads can be processed on the pipe section according to actual needs, and the threads can be subjected to magnetic particle inspection.

The following describes it in detail through specific embodiments.

Example 1

Steelmaking: The ingredients are prepared according to the composition of the sulfide stress corrosion resistant oil casing of Example 1 shown in Table 1 below, sponge iron and high-quality scrap steel are used as raw materials, and then smelting in an electric furnace, feeding rare earth wire, refining outside the furnace, vacuum degassing, feeding Si-Ca wire to modify the inclusions, and obtaining molten steel;

Continuous casting: The molten steel is cast into rod-shaped continuous casting billets. During the continuous casting process, electromagnetic stirring and soft pressure reduction technology are used to control the segregation in the continuous casting billets;

Piercing and hot rolling: The continuous casting billet is heated in a ring-shaped heating furnace at a temperature of 1270°C for 110 minutes, then hot-pierced at 1230°C, hot-rolled at 1000°C, and after cooling, sawn to a preset length to obtain a tube billet;

Heat treatment: First quenching and tempering heat treatment: In a protective atmosphere furnace, the tube blank is first quenched at 935°C, kept at this temperature for 50 minutes, sprayed with water inside and outside for quenching, and then cooled at a cooling rate of 25°C/s to ensure that all martensitic structures are basically obtained after quenching; then the first tempering is carried out at 660°C for 110 minutes to obtain fine and uniform tempered troostite with a grain size of 8, and water-cooled after tempering to avoid possible temper brittleness; then hot straightening is carried out at 620°C and then water-cooled;

Second quenching and tempering heat treatment: then carry out the second quenching at 900°C, keep warm for 50 minutes, spray water quenching inside and outside, and then cool at a cooling rate of 25°C/s to ensure that basically all martensitic structures are obtained after quenching; then carry out the second tempering at 670°C, keep warm for 110 minutes and then water cool to obtain fine and uniform tempered troostite with a grain size of 9; then carry out hot straightening at 600°C and water cool; then carry out stress relief tempering at 620°C to effectively eliminate the residual stress and obtain an oil casing and tubing resistant to sulfide stress corrosion, recorded as 80SS (yield strength 80ksi level, super sulfur resistance).

Example 2

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the oil casing and casing resistant to sulfide stress corrosion of Example 2 are prepared according to the ingredients shown in Table 1 below; blast furnace molten iron and high-quality scrap steel are used as raw materials;

(2) Smelting in an oxygen-blown converter;

The obtained oil casing and tubing is resistant to sulfide stress corrosion and is recorded as 80SS (yield strength 80ksi level, super sulfur resistance).

Example 3

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 3 are prepared according to the ingredients shown in Table 1 below;

(2) Second quenching and tempering heat treatment: second tempering temperature 650°C, straightening temperature 580°C, stress relief tempering temperature 600°C;

The obtained sulfide stress corrosion resistant oil casing is recorded as 95SS (yield strength 95 ksi level, super sulfur resistance).

Example 4

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 4 are prepared according to the ingredients shown in Table 1 below; blast furnace molten iron and high-quality scrap steel are used as raw materials;

(2) Smelting in an oxygen-blown converter;

(3) Second quenching and tempering heat treatment: second tempering temperature 650°C, straightening temperature 580°C, stress relief tempering temperature 600°C;

The obtained sulfide stress corrosion resistant oil casing is recorded as 95SS (yield strength 95 ksi level, super sulfur resistance).

Example 5

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 5 are prepared according to the ingredients shown in Table 1 below;

(2) Second quenching and tempering heat treatment: second tempering temperature 650°C, straightening temperature 580°C, stress relief tempering temperature 600°C;

The obtained sulfide stress corrosion resistant oil casing is recorded as 95SS (yield strength 95 ksi level, super sulfur resistance).

Example 6

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 6 are prepared according to the ingredients shown in Table 1 below; blast furnace molten iron and high-quality scrap steel are used as raw materials;

(2) Smelting in an oxygen-blown converter;

(3) Second quenching and tempering heat treatment: second tempering temperature 630°C, straightening temperature 560°C, stress relief tempering temperature 580°C;

The obtained sulfide stress corrosion resistant oil casing is recorded as 110SS (yield strength 110 ksi level, super sulfur resistance).

Example 7

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 7 are prepared according to the ingredients shown in Table 1 below;

(2) Second quenching and tempering heat treatment: second tempering temperature 630℃, straightening temperature 560℃, stress relief tempering temperature 580℃;

The obtained sulfide stress corrosion resistant oil casing is recorded as 110SS (yield strength 110 ksi level, super sulfur resistance).

Example 8

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 8 are prepared according to the ingredients shown in Table 1 below; blast furnace molten iron and high-quality scrap steel are used as raw materials;

(2) Smelting in an oxygen-blown converter;

(3) Second quenching and tempering heat treatment: second tempering temperature 630°C, straightening temperature 560°C, stress relief tempering temperature 580°C;

The obtained sulfide stress corrosion resistant oil casing is recorded as 110SS (yield strength 110 ksi level, super sulfur resistance).

Example 9

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 9 are prepared according to the ingredients shown in Table 1 below;

(2) Second quenching and tempering heat treatment: second tempering temperature 610℃, straightening temperature 540℃, stress relief tempering temperature 560℃;

The obtained sulfide stress corrosion resistant oil casing is recorded as 125S (yield strength 125ksi level, ordinary sulfur resistance).

Example 10

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 10 are prepared according to the ingredients shown in Table 1 below; blast furnace molten iron and high-quality scrap steel are used as raw materials;

(2) Smelting in an oxygen-blown converter;

(3) Second quenching and tempering heat treatment: second tempering temperature 610℃, straightening temperature 540℃, stress relief tempering temperature 560℃;

The obtained sulfide stress corrosion resistant oil casing is recorded as 125S (yield strength 125ksi level, ordinary sulfur resistance).

Embodiment 11

The preparation method of the oil casing resistant to sulfide stress corrosion is basically the same as that in Example 1, except that:

(1) The ingredients of the sulfide stress corrosion resistant oil casing of Example 11 are prepared according to the ingredients shown in Table 1 below;

(2) Second quenching and tempering heat treatment: second tempering temperature 610℃, straightening temperature 540℃, stress relief tempering temperature 560℃;

The obtained sulfide stress corrosion resistant oil casing is recorded as 125S (yield strength 125ksi level, ordinary sulfur resistance).

Table 1 Chemical composition of the sulfide stress corrosion resistant oil casing in Examples 1-11

The sulfide stress corrosion resistant oil casing prepared in Examples 1-11 were subjected to grain size test, yield strength test, tensile strength test, elongation test, Charpy V-notch impact toughness test, and NACE TM 0177 A method 720 hours hydrogen sulfide stress corrosion test. The results are shown in Table 2 below.

Table 2 Performance of sulfide stress corrosion resistant oil casing in Examples 1-11

The above test results show that the sulfide stress corrosion resistant oil casing prepared by the present invention through appropriate preparation technology and reasonable chemical composition design has excellent comprehensive properties such as strength, plasticity, toughness, and hydrogen sulfide stress corrosion resistance, and can meet the comprehensive performance requirements of oil casing in the development of sour oil and gas fields.

It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims (10)

1. An oil casing resistant to sulfide stress corrosion, characterized in that, in terms of mass percentage, the oil casing resistant to sulfide stress corrosion includes the following chemical components: C 0.21%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo0.35%～0.55% or W 0.70%～1.10%, Ni 0～0.25%, Cu 0～0.25%, Nb 0.035%～0.065% or V 0.035%～0.065%, RE 0.005%～0.010%, Al 0.006%～0.018%, Ca0.006%～0.010%, P≤0.012%, S≤0.003% , O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and inevitable impurities; among them, Mo/P≥25 or W/P≥50; Al/N≥2; (Ca+RE )/S≥3; the preparation method of the oil casing resistant to sulfide stress corrosion includes the steps: According to the composition of the above-mentioned anti-sulfide stress corrosion oil casing, the raw materials obtained are smelted in an electric furnace or an oxygen-blown converter, fed with rare earth wire, refining outside the furnace, vacuum degassed, and fed with Si-Ca wire to remove inclusions. Perform denaturation treatment to obtain molten steel; Cast the molten steel into a rod-shaped continuous casting billet; The continuous casting billet is heated to 1250-1280°C in a heating furnace, kept for 90-120 minutes, then hot-pierced at a temperature of 1200-1250°C, and hot-rolled at a temperature of 980-1180°C. After cooling, The tube blank is obtained; in a protective atmosphere furnace, the tube blank is quenched for the first time at a temperature of 925 to 945°C, kept for 40 to 60 minutes, then cooled, and then quenched for the first time at a temperature of 655 to 665°C. Fire, keep warm for 90-120 minutes and then water-cool, then perform heat straightening at a temperature of 600-640°C and then water-cool; Then perform the second quenching at the temperature of 890~910℃, keep it for 40~60min and then cool it, then perform the second tempering at the temperature of 600~680℃, keep it for 90~120min, then water-cool, and then cool it at 530~610℃ Thermal straightening is performed at a temperature of 550 to 630° C., and after water cooling, the oil casing is destressed and tempered at a temperature of 550 to 630° C. to obtain the oil casing resistant to sulfide stress corrosion. 2. The oil casing resistant to sulfide stress corrosion according to claim 1, characterized in that, in terms of mass percentage, the oil casing resistant to sulfide stress corrosion includes the following chemical components: C 0.21%～0.24%, Si 0.21%～0.37%, Mn 0.68%～0.73%, Cr 0.96%～1.03%, Mo0.35%～0.40% or W 0.70%, Nb 0.035%～0.040% or V 0.035% ~0.038%, RE 0.005%~0.010%, Al 0.006%~0.011%, Ca 0.006%~0.010%, P≤0.011%, S≤0.003%, O≤0.002%, H≤0.00015%, N≤0.003%, The balance is Fe and inevitable impurities; among them, Mo/P≥35 or W/P≥70; Al/N≥2; (Ca+RE)/S≥3. 3. The oil casing resistant to sulfide stress corrosion according to claim 1, characterized in that, in terms of mass percentage, the oil casing resistant to sulfide stress corrosion includes the following chemical components: C 0.21%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo0.35%～0.55% or W 0.70%～1.10%, Ni 0.18～0.25%, Cu0 .17～0.25%, Nb 0.035%～0.065% or V 0.035%～0.065%, RE 0.005%～0.010%, Al 0.006%～0.018%, Ca0.006%～0.010%, P≤0.012%, S≤0.003 %, O≤0.002%, H≤0.00015%, N≤0.003%, the balance is Fe and inevitable impurities; among them, Mo/P≥25 or W/P≥50; Al/N≥2; (Ca+ RE)/S≥3. 4. The oil casing resistant to sulfide stress corrosion according to claim 3, characterized in that, in terms of mass percentage, the oil casing resistant to sulfide stress corrosion includes the following chemical components: C 0.22%～0.26%, Si 0.19%～0.39%, Mn 0.65%～0.75%, Cr 0.95%～1.05%, Mo0.44%～0.55% or W 0.91%～1.10%, Ni 0.18～0.25%, Cu0 .17～0.25%, Nb 0.059%～0.065% or V 0.060%～0.065%, RE 0.006%～0.009%, Al 0.012%～0.018%, Ca0.007%～0.010%, P≤0.012%, S≤0.001 %, O≤0.0019%, H≤0.00013%, N≤0.002%, the balance is Fe and inevitable impurities; among them, Mo/P≥35 or W/P≥90; Al/N≥2; (Ca+ RE)/S≥10. 5. A method for preparing oil casing resistant to sulfide stress corrosion, which is characterized by including the steps: After the chemical composition of the oil casing resistant to sulfide stress corrosion according to any one of claims 1 to 4 is batched, smelted and continuously cast, a continuous cast billet is obtained; After perforating and hot rolling the continuous cast billet, a tube billet is obtained; The tube blank is subjected to two quenching and tempering heat treatments to obtain the oil casing resistant to sulfide stress corrosion. 6. The preparation method of oil casing resistant to sulfide stress corrosion according to claim 5, characterized in that, after smelting and continuous casting, the step of obtaining the continuous casting billet specifically includes: The raw materials obtained by batching are smelted in an electric furnace or an oxygen-blown converter, fed with rare earth wires, refining outside the furnace, vacuum degassed, and fed with Si-Ca wires to denature inclusions to obtain molten steel; The molten steel is cast into a rod-shaped continuous casting billet. 7. The preparation method of oil casing resistant to sulfide stress corrosion according to claim 5, characterized in that the step of obtaining a tube blank after perforating and hot rolling the continuous casting billet specifically includes: The continuous casting billet is heated to 1250-1280°C in a heating furnace, kept for 90-120 minutes, then hot-pierced at a temperature of 1200-1250°C, and hot-rolled at a temperature of 980-1180°C. After cooling, Obtain tube blank. 8. The preparation method of oil casing resistant to sulfide stress corrosion according to claim 5, characterized in that the said tube blank is subjected to two quenching and tempering heat treatments to obtain the oil resistant to sulfide stress corrosion. The steps of casing include: In a protective atmosphere furnace, the tube blank is quenched for the first time at a temperature of 925 to 945°C, kept for 40 to 60 minutes, then cooled, and then tempered for the first time at a temperature of 655 to 665°C, and kept for 90 Water cooling after ~120 minutes, then hot straightening at a temperature of 600~640°C and then water cooling; Then perform the second quenching at the temperature of 890~910℃, keep it for 40~60min and then cool it, then perform the second tempering at the temperature of 600~680℃, keep it for 90~120min, then water-cool, and then cool it at 530~610℃ Thermal straightening is performed at a temperature of 550 to 630° C., and after water cooling, the oil casing is destressed and tempered at a temperature of 550 to 630° C. to obtain the oil casing resistant to sulfide stress corrosion. 9. The preparation method of oil casing resistant to sulfide stress corrosion according to claim 8, characterized in that the tube blank is quenched for the first time at a temperature of 925 to 945°C, and then kept for 40 to 60 minutes. , cooling at a cooling rate of 20~30℃/s; and / or, Then perform the second quenching at a temperature of 890 to 910°C. After holding the temperature for 40 to 60 minutes, cool at a cooling rate of 20 to 30°C/s. 10. The preparation method of oil casing resistant to sulfide stress corrosion according to claim 5, characterized in that, after the tube blank is subjected to two quenching and tempering heat treatments, the oil casing resistant to sulfide stress corrosion is obtained. Before casing, there are also steps: Thread processing is performed on the tube blank after two quenching and tempering heat treatments.