Heavy oil thermal utilization casing and preparation method thereof

Abstract

The present invention discloses a heavy oil hot-dip casing and a preparation method thereof, relating to the technical field of petroleum casing. The casing comprises the following chemical components by weight: C 0.20-0.30%, Si 1.00-1.15%, Mn 1.20-1.33%, Cr 0.60-0.85%, Mo 0.33-0.48%, Nb 0.03-0.10%, RE 0.001-0.004%, Al 0.010-0.030%, Ca 0.012-0.025%, P ≤ 0.015%, S ≤ 0.005%, N ≤ 0.005%, O+H+N ≤ 0.007%, with the remainder being Fe and unavoidable impurities. The casing has a room-temperature yield strength that meets the maximum requirements of 150 ksi steel grade, a total elongation greater than 23%, and a yield strength drop of no more than 16% of the room-temperature yield strength at 350°C.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum casing, in particular to a heavy oil thermal utilization casing and a preparation method thereof. Background Art

[0002] Heavy oil accounts for a significant portion of my country's oil and gas resources. Heavy oil production typically relies primarily on steam cycling, with temperatures reaching as high as 350°C. Repeated temperature fluctuations cause severe casing damage, including deformation, necking, breakage, and threaded joint stripping. Casing losses in thermal recovery wells typically exceed 30%, and in some areas, even reach 50-70%. Previous designs of casing strings for heavy oil thermal recovery wells were primarily stress-based, primarily considering material strength. However, under heavy oil thermal recovery conditions, casing materials are subject to creep and stress relaxation, and plastic strain fatigue occurs during thermal cycling. Without adequate consideration of these factors, existing products fail to meet the performance and quality requirements for heavy oil thermal recovery, a fundamental cause of the significant casing damage. To solve this problem, a strain-based casing string design method for heavy oil thermal recovery wells has been developed in recent years. In addition to strength requirements for thermal recovery casing, it also puts forward requirements for its elongation of uniform plastic deformation and the reduction range of high-temperature mechanical properties, so as to ensure that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery.

[0003] Although a series of high-strength casing products have been developed for heavy oil thermal recovery wells, these products do not include high-strength, high-uniform elongation thermal recovery casings based on the strain gauge casing string design concept. Therefore, it is imperative to develop a high-strength, sufficiently uniform elongation casing suitable for heavy oil steam huff-and-puff thermal recovery. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a heavy oil hot-adoption casing with high strength and sufficiently uniform elongation and a preparation method thereof.

[0005] The technical solutions of the present invention are as follows:

[0006] A first aspect of the present invention provides a heavy oil thermal utilization casing, wherein the heavy oil thermal utilization casing comprises the following chemical components, calculated by mass percentage:

[0007] C 0.20%~0.30%, Si 1.00%~1.15%, Mn 1.20%~1.33%, Cr 0.60%~0.85%, Mo 0.33%~0.48%, Nb 0.03%~0.10%, RE 0.001%~0.004%, Al 0.010%~0.030%, Ca 0.012%~0.025%, P≤0.015%, S≤0.005%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0008] Optionally, the heavy oil heat utilization casing includes the following chemical components, calculated by mass percentage:

[0009] C 0.20%~0.22%, Si 1.00%~1.02%, Mn 1.20%~1.22%, Cr 0.60%~0.65%, Mo 0.33%~0.35%, Nb 0.03%~0.05%, RE 0.001%~0.002%, Al 0.010%~0.014%, Ca 0.012%~0.014%, P≤0.012%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0010] Optionally, the heavy oil heat utilization casing includes the following chemical components, calculated by mass percentage:

[0011] C 0.21%~0.23%, Si 1.03%~1.05%, Mn 1.21%~1.23%, Cr 0.66%~0.69%, Mo 0.34%~0.36%, Nb 0.04%~0.06%, RE 0.002%~0.003%, Al 0.015%~0.017%, Ca 0.015%~0.017%, P≤0.012%, S≤0.003%, N≤0.004%, O+H+N≤0.006%, and the balance is Fe and unavoidable impurities.

[0012] Optionally, the heavy oil heat utilization casing includes the following chemical components, calculated by mass percentage:

[0013] C 0.21%~0.24%, Si 1.05%~1.08%, Mn 1.22%~1.24%, Cr 0.71%~0.75%, Mo 0.37%~0.39%, Nb 0.05%~0.07%, RE 0.002%~0.003%, Al 0.018%~0.020%, Ca 0.016%~0.018%, P≤0.011%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0014] Optionally, the heavy oil heat utilization casing includes the following chemical components, calculated by mass percentage:

[0015] C 0.23%~0.25%, Si 1.09%~1.11%, Mn 1.25%~1.27%, Cr 0.76%~0.79%, Mo 0.40%~0.42%, Nb 0.06%~0.08%, RE 0.003%~0.004%, Al 0.021%~0.024%, Ca 0.018%~0.020%, P≤0.012%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0016] Optionally, the heavy oil heat utilization casing includes the following chemical components, calculated by mass percentage:

[0017] C 0.25%~0.27%, Si 1.12%~1.14%, Mn 1.28%~1.30%, Cr 0.81%~0.83%, Mo 0.43%~0.45%, Nb 0.07%~0.09%, RE 0.003%, Al 0.025%~0.027%, Ca0.021%~0.023%, P≤0.011%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0018] Optionally, the heavy oil heat utilization casing includes the following chemical components, calculated by mass percentage:

[0019] C 0.28%~0.30%, Si 1.13%~1.15%, Mn 1.31%~1.33%, Cr 0.83%~0.85%, Mo 0.46%~0.48%, Nb 0.08%~0.10%, RE 0.004%, Al 0.028%~0.030%, Ca0.023%~0.025%, P≤0.010%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0020] A second aspect of the present invention provides a method for preparing a heavy oil thermal utilization casing, comprising the steps of:

[0021] According to the present invention, the chemical composition of the heavy oil heat-using casing is subjected to batching, smelting, and continuous casting to obtain a continuous casting billet;

[0022] The continuous casting billet is subjected to hot piercing and hot continuous rolling to obtain a tube billet;

[0023] The tube blank is subjected to tempering heat treatment, heat straightening and then thread processing to obtain the heavy oil hot-using casing.

[0024] Optionally, after smelting and continuous casting, a continuous casting billet is obtained; and after hot piercing and hot rolling the continuous casting billet, a tube billet is obtained, specifically comprising:

[0025] The raw materials obtained by batching are sequentially subjected to oxygen-blown converter smelting, RE wire feeding, external refining, vacuum degassing, and Si-Ca wire feeding for modification of inclusions to obtain molten steel;

[0026] Casting the molten steel into a rod-shaped continuous casting billet;

[0027] The continuous casting billet is heated to 1180-1230° C. in a heating furnace, kept warm for 90-120 minutes, then hot-pierced at 1170-1200° C., hot-rolled at 950-1150° C., and cooled to obtain a tube billet.

[0028] Optionally, the step of subjecting the tube blank to quenching and tempering heat treatment, heat straightening, and then threading to obtain the heavy oil hot-adapted casing specifically includes:

[0029] In a protective atmosphere furnace, the tube blank is heated at a temperature of 890-910° C., kept at this temperature for 40-60 minutes, and then cooled by spraying water inside and outside at a cooling rate of 30° C. / s or higher. The tube blank is then tempered at a temperature of 585-640° C. for 90-120 minutes and then water-cooled. The tube blank is then hot-straightened at a temperature of 530-590° C. and then water-cooled. After thread processing, the heavy oil hot-adopting casing is obtained.

[0030] Beneficial Effects: The heavy oil thermal recovery casing provided by the present invention has excellent comprehensive performance, including high strength and sufficiently large elongation. Its room temperature yield strength can meet the steel grade requirements of 120 ksi, 125 ksi, 130 ksi, 135 ksi, 140 ksi, and 150 ksi, respectively. Specifically, its minimum room temperature yield strength is greater than 827 to 1034 MPa, its minimum tensile strength is greater than 965 to 1172 MPa, its total elongation is greater than or equal to 23%, its uniform elongation is greater than or equal to 12%, and its Charpy V-notch impact toughness at 0°C is greater than or equal to 100 J. The yield strength at 350°C decreases by no more than 16% of the room temperature yield strength, thus meeting the casing strength, plasticity, and strain fatigue life requirements for 350°C heavy oil steam thermal recovery deep wells. DETAILED DESCRIPTION

[0031] The present invention provides a heavy oil thermal utilization casing and a method for manufacturing the same. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0032] 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 are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] An embodiment of the present invention provides a heavy oil thermal utilization casing, wherein the heavy oil thermal utilization casing comprises the following chemical components, calculated by weight percentage:

[0034] C 0.20%~0.30%, Si 1.00%~1.15%, Mn 1.20%~1.33%, Cr 0.60%~0.85%, Mo 0.33%~0.48%, Nb 0.03%~0.10%, RE 0.001%~0.004%, Al 0.010%~0.030%, Ca 0.012%~0.025%, P≤0.015%, S≤0.005%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0035] RE is a rare earth element. In some specific embodiments, RE may be Ce (cerium).

[0036] In terms of composition design, the embodiments of the present invention propose to adopt a low C content, add Si, Mn, Cr, Mo, Nb microalloying, add rare earth (RE) elements, control harmful elements such as P, S, O, H, and N in the steel, use Al and Si fully deoxidized killed steel, and perform Ca treatment on the molten steel to achieve the comprehensive performance requirements of heavy oil thermal recovery casing that meets both high strength and sufficiently uniform elongation. The present invention designs the chemical composition and content of the heavy oil thermal recovery casing to achieve synergistic effects between the various elements, ultimately resulting in high strength and sufficiently large elongation, resulting in excellent overall performance. The room temperature yield strength can meet the steel grade requirements of 120 ksi, 125 ksi, 130 ksi, 135 ksi, 140 ksi, and 150 ksi, respectively. Specifically, the minimum room temperature yield strength is greater than 827 to 1034 MPa, the minimum tensile strength is greater than 965 to 1172 MPa, the total elongation is greater than or equal to 23%, the uniform elongation is greater than or equal to 12%, and the Charpy V-notch impact toughness at 0°C is greater than or equal to 100 J. The yield strength at 350°C does not drop by more than 16% of the room temperature yield strength, thus meeting the strength, plasticity, and strain fatigue life requirements of the casing for 350°C heavy oil steam thermal recovery deep wells. The casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery.

[0037] C is the main strengthening element in steel. A low C content is detrimental to improving the hardenability and strength of the steel, while a high C content is detrimental to the plasticity and toughness of the steel. Taking all factors into consideration, the C content should be controlled within the range of 0.20% to 0.30%.

[0038] Si is mainly used to improve the strength, oxidation resistance and thermal fatigue resistance of steel. Taking all factors into consideration, it is best to control it within the range of 1.00% to 1.15%.

[0039] Mn is mainly used to improve the hardenability of steel, thereby increasing its strength, but its content is too high will increase the tendency of segregation. Taking all factors into consideration, it is best to control it within the range of 1.20% to 1.33%.

[0040] Cr is mainly used to improve the hardenability of steel, thereby increasing its strength, oxidation resistance and corrosion resistance. However, too high a content will increase the cost. Taking all factors into consideration, it is best to control it within the range of 0.60% to 0.85%.

[0041] Mo is mainly used to improve the hardenability of steel to increase strength and tempering stability, while also improving corrosion resistance. However, excessive Mo content increases costs. Taking all factors into consideration, it is best to control Mo content within the range of 0.33% to 0.48%.

[0042] Nb is added to steel to form NbC and NbN with C and N in the steel, respectively, which inhibits austenite grain growth and refines the grains, thereby improving strength and toughness. Taking all factors into consideration, the content should be controlled within the range of 0.03% to 0.10%.

[0043] Adding a small amount of RE (rare earth elements) can purify molten steel, modify inclusions, and alloy, improving the strength and ductility of the steel. A content that is too low will have no desired effect, while a high content can easily create new inclusions and increase costs. Taking all factors into consideration, the ideal range is 0.001% to 0.004%.

[0044] Al is an important deoxidizer. It forms oxides with oxygen to deoxidize, and nitrides with nitrogen to partially eliminate the negative effects of nitrogen. It also refines grains and improves strength and toughness. To ensure effective nitrogen control, Al / N should be controlled to ≥ 2 (i.e., the ratio of the mass percentage of Al to the mass percentage of N is greater than or equal to 2). Taking all factors into consideration, the Al content should be controlled within the range of 0.010% to 0.030%.

[0045] Ca can improve the properties and morphology of inclusions, thereby enhancing the steel's plasticity, toughness, and corrosion resistance. To ensure the inclusion's ability to control deformation, it is necessary to control the Ca / S ratio to ≥ 2 (i.e., the ratio of the mass percentage of Ca to the mass percentage of S is greater than or equal to 2). Taking all factors into consideration, the Ca content should be controlled within the range of 0.012% to 0.025%.

[0046] P is a harmful element that mainly affects the plasticity and toughness of steel. Taking all factors into consideration, it is advisable to control P ≤ 0.015% (i.e., the mass content of P is less than or equal to 0.015%).

[0047] S is a harmful element that mainly affects the plasticity and toughness of steel. Taking all factors into consideration, it is advisable to control S ≤ 0.005% (i.e. the mass content of S is less than or equal to 0.005%).

[0048] O is a harmful element, primarily affecting the ductility and toughness of steel. H is a harmful element, primarily affecting the ductility and toughness of steel. N is a harmful element, primarily affecting the ductility and toughness of steel during strain aging. Taking all factors into consideration, it is recommended to control N to ≤ 0.005% (i.e., the N content by mass is less than or equal to 0.005%). Furthermore, O+H+N should be controlled to ≤ 0.007% (i.e., the sum of the O, H, and N content by mass is less than or equal to 0.007%).

[0049] In some embodiments, the heavy oil heat utilization casing comprises the following chemical components, calculated by weight percentage:

[0050] C 0.20%~0.22%, Si 1.00%~1.02%, Mn 1.20%~1.22%, Cr 0.60%~0.65%, Mo 0.33%~0.35%, Nb 0.03%~0.05%, RE 0.001%~0.002%, Al 0.010%~0.014%, Ca 0.012%~0.014%, P≤0.012%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0051] In this embodiment, the yield strength level of the heavy oil thermal recovery casing can meet the requirement of 120 ksi. At room temperature, the yield strength reaches 880-885 MPa, the tensile strength reaches 989-994 MPa, the total elongation reaches 26%, and the uniform elongation reaches 15%. At 0°C, the Charpy impact toughness reaches 120-122 J. At 350°C, the yield strength reaches 748-752 MPa, the tensile strength reaches 870-875 MPa, the total elongation reaches 29%, and the uniform elongation reaches 17%. The yield strength at 350°C does not drop by more than 16% of the room temperature yield strength. This ensures that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery, meeting the strength and strain fatigue life requirements for casing in 350°C heavy oil steam thermal recovery wells.

[0052] In some embodiments, the heavy oil heat utilization casing comprises the following chemical components, calculated by weight percentage:

[0053] C 0.21%~0.23%, Si 1.03%~1.05%, Mn 1.21%~1.23%, Cr 0.66%~0.69%, Mo 0.34%~0.36%, Nb 0.04%~0.06%, RE 0.002%~0.003%, Al 0.015%~0.017%, Ca 0.015%~0.017%, P≤0.012%, S≤0.003%, N≤0.004%, O+H+N≤0.006%, and the balance is Fe and unavoidable impurities.

[0054] In this embodiment, the yield strength level of the heavy oil thermal recovery casing can meet the requirement of 125 ksi. At room temperature, the yield strength reaches 915-920 MPa, the tensile strength reaches 1028-1034 MPa, the total elongation reaches 25.4%-25.6%, and the uniform elongation reaches 14.4%-14.6%. The Charpy impact toughness at 0°C reaches 116-119 J. At 350°C, the yield strength reaches 778-782 MPa, the tensile strength reaches 905-910 MPa, the total elongation reaches 28.3%-28.5%, and the uniform elongation reaches 16.3%-16.6%. The yield strength at 350°C does not drop by more than 16% of the room temperature yield strength. This ensures that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery, meeting the strength and strain fatigue life requirements for heavy oil steam thermal recovery wells at 350°C.

[0055] In some embodiments, the heavy oil heat utilization casing comprises the following chemical components, calculated by weight percentage:

[0056] C 0.21%~0.24%, Si 1.05%~1.08%, Mn 1.22%~1.24%, Cr 0.71%~0.75%, Mo 0.37%~0.39%, Nb 0.05%~0.07%, RE 0.002%~0.003%, Al 0.018%~0.020%, Ca 0.016%~0.018%, P≤0.011%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0057] In this embodiment, the yield strength level of the heavy oil thermal recovery casing can meet the requirement of 130 ksi. At room temperature, the yield strength reaches 949-955 MPa, the tensile strength reaches 1066-1073 MPa, the total elongation reaches 25%, and the uniform elongation reaches 14%. The Charpy impact toughness at 0°C reaches 113-115 J. At 350°C, the yield strength reaches 807-812 MPa, the tensile strength reaches 938-944 MPa, the total elongation reaches 28%, and the uniform elongation reaches 16%. The yield strength at 350°C does not drop by more than 16% of the room temperature yield strength, ensuring that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery, thus meeting the casing strength and strain fatigue life requirements for 350°C heavy oil steam thermal recovery wells.

[0058] In some embodiments, the heavy oil heat utilization casing comprises the following chemical components, calculated by weight percentage:

[0059] C 0.23%~0.25%, Si 1.09%~1.11%, Mn 1.25%~1.27%, Cr 0.76%~0.79%, Mo 0.40%~0.42%, Nb 0.06%~0.08%, RE 0.003%~0.004%, Al 0.021%~0.024%, Ca 0.018%~0.020%, P≤0.012%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0060] In this embodiment, the yield strength level of the heavy oil thermal recovery casing can meet the requirement of 135 ksi. At room temperature, the yield strength reaches 984-989 MPa, the tensile strength reaches 1106-1111 MPa, the total elongation reaches 24.5%-24.6%, and the uniform elongation reaches 13.4%-13.6%. The Charpy impact toughness at 0°C reaches 108-110 J. At 350°C, the yield strength reaches 836-841 MPa, the tensile strength reaches 973-978 MPa, the total elongation reaches 27.4%-27.6%, and the uniform elongation reaches 15.4%-15.7%. The yield strength at 350°C does not drop by more than 16% of the room temperature yield strength. This ensures that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery, meeting the strength and strain fatigue life requirements for casing in 350°C heavy oil steam thermal recovery wells.

[0061] In some embodiments, the heavy oil heat utilization casing comprises the following chemical components, calculated by weight percentage:

[0062] C 0.25%~0.27%, Si 1.12%~1.14%, Mn 1.28%~1.30%, Cr 0.81%~0.83%, Mo 0.43%~0.45%, Nb 0.07%~0.09%, RE 0.003%, Al 0.025%~0.027%, Ca0.021%~0.023%, P≤0.011%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0063] In this embodiment, the yield strength level of the heavy oil thermal recovery casing can meet the requirement of 140 ksi. At room temperature, the yield strength reaches 1018-1024 MPa, the tensile strength reaches 1131-1138 MPa, the total elongation reaches 24%, and the uniform elongation reaches 13%. At 0°C, the Charpy impact toughness reaches 105-108 J. At 350°C, the yield strength reaches 865-870 MPa, the tensile strength reaches 995-1001 MPa, the total elongation reaches 27%, and the uniform elongation reaches 15%. The yield strength at 350°C drops by no more than 16% of the room temperature yield strength. This ensures that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery, meeting the strength and strain fatigue life requirements for casing in 350°C heavy oil steam thermal recovery wells.

[0064] In some embodiments, the heavy oil heat utilization casing comprises the following chemical components, calculated by weight percentage:

[0065] C 0.28%~0.30%, Si 1.13%~1.15%, Mn 1.31%~1.33%, Cr 0.83%~0.85%, Mo 0.46%~0.48%, Nb 0.08%~0.10%, RE 0.004%, Al 0.028%~0.030%, Ca0.023%~0.025%, P≤0.010%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

[0066] In this embodiment, the yield strength level of the heavy oil thermal recovery casing can meet the requirement of 150 ksi. At room temperature, the yield strength reaches 1087-1093 MPa, the tensile strength reaches 1208-1214 MPa, the total elongation reaches 23%, and the uniform elongation reaches 12%. At 0°C, the Charpy impact toughness reaches 101-104 J. At 350°C, the yield strength reaches 924-929 MPa, the tensile strength reaches 1063-1068 MPa, the total elongation reaches 26%, and the uniform elongation reaches 14%. The yield strength at 350°C drops by no more than 16% of the room temperature yield strength, ensuring that the casing can withstand large uniform plastic deformation and plastic strain fatigue without premature failure during heavy oil thermal recovery, thus meeting the strength and strain fatigue life requirements for casing in 350°C heavy oil steam thermal recovery wells.

[0067] The present invention develops a manufacturing process that matches the chemical composition ratios described above. This process primarily involves steelmaking (including refining outside the furnace, vacuum degassing, and Ca treatment), continuous casting, hot rolling in the austenitic zone, tempering heat treatment, heat straightening, and non-destructive testing. This process achieves a fine and uniform microstructure, thereby achieving a reasonable match between the strength, plasticity, and toughness of the casing. Specifically, an embodiment of the present invention further provides a method for preparing a heavy oil hot-adaptation casing, comprising the following steps:

[0068] S1. According to the embodiment of the present invention, the chemical composition of the heavy oil hot-using casing is batched, smelted, and continuously cast to obtain a continuous casting billet;

[0069] S2, hot piercing and hot rolling the continuous casting billet to obtain a tube billet;

[0070] S3, performing tempering heat treatment and heat straightening on the tube blank and then performing thread processing to obtain the heavy oil hot-using casing.

[0071] The chemical composition design and manufacturing process of the embodiment of the present invention have the effect of increasing strength and improving plasticity and toughness.

[0072] The preparation method of the present invention is aimed at the heavy oil thermal utilization casing with the above chemical composition, obtains the expected organizational structure and performance, fully utilizes the performance of the heavy oil thermal utilization casing, has low cost, and the process parameters in the process are easy to control. The obtained heavy oil thermal utilization casing has stable performance.

[0073] In step S1, in some embodiments, after smelting and continuous casting, the step of obtaining the continuous casting billet specifically includes:

[0074] The raw materials obtained by batching are sequentially subjected to oxygen-blown converter smelting, feeding RE wire (such as Ce wire), external refining, vacuum degassing, and feeding Si-Ca wire to denature inclusions to obtain molten steel;

[0075] The molten steel is cast into a rod-shaped continuous casting billet (electromagnetic stirring and soft reduction technology can be used during the continuous casting process to control segregation in the continuous casting billet).

[0076] In step S2, in some embodiments, the step of obtaining a tube billet after hot piercing and hot rolling the continuously cast billet specifically includes:

[0077] The continuous casting billet is heated to 1180-1230° C. in a heating furnace, kept warm for 90-120 minutes, then hot-pierced at 1170-1200° C., hot-rolled at 950-1150° C., and cooled (e.g., air-cooled) to obtain a tube billet (specifically, it can be sawed to a suitable length to obtain a tube billet).

[0078] In step S3, in some embodiments, the step of subjecting the tube blank to quenching and tempering heat treatment, heat straightening, and then threading to obtain the heavy oil hot-adapted casing specifically includes:

[0079] In a protective atmosphere furnace, the tube blank is heated at a temperature of 890-910° C., kept at this temperature for 40-60 minutes, and then cooled by spraying water inside and outside at a cooling rate of 30° C. / s or higher (e.g., 30-60° C. / s) to obtain a martensite structure. The tube blank is then tempered at a temperature of 585-640° C. for 90-120 minutes and then water-cooled (water cooling after tempering is to avoid possible temper brittleness) to obtain a tempered bainite structure. The tube blank is then hot-straightened at a temperature of 530-590° C. and then water-cooled. After threading (non-destructive testing can be performed before threading), the heavy oil hot-adapting casing is obtained.

[0080] Specifically, according to actual needs, API standard threads or special threads can be processed on both ends of the pipe section, and the threads can be subjected to magnetic particle inspection.

[0081] The present invention will be further described below by means of specific examples.

[0082] Example 1

[0083] Table 1 Chemical composition of heavy oil thermal casing in Examples 1-18

[0084]

[0085] In Examples 1-18 in Table 1, the content of each component is in percentage by mass, and the remainder to 100% is Fe and unavoidable impurities.

[0086] Example 1

[0087] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0088] Steelmaking: The ingredients are prepared according to the composition of the heavy oil hot-using casing of Example 1 shown in Table 1, and then the steel is subjected to oxygen-blown converter steelmaking, Ce wire feeding, off-furnace refining, vacuum degassing, and Si-Ca wire feeding to control deformation of inclusions to obtain molten steel;

[0089] Continuous casting: Molten steel is cast into rod-shaped continuous casting billets. During the continuous casting process, electromagnetic stirring and soft reduction technology are used to control segregation in the continuous casting billets.

[0090] Piercing and hot rolling: The continuous casting billet is heated in a ring-shaped heating furnace at a temperature of 1200°C for 120 minutes, then hot-pierced at 1170°C, and hot-rolled at 950°C to 1150°C (with an initial rolling temperature of 1150°C and a final rolling temperature of 950°C). After air cooling, the billet is sawn to a preset length to obtain a tube billet.

[0091] Tempering heat treatment and heat straightening: A heat treatment process of heating in a protective atmosphere furnace, quenching + high-temperature tempering is adopted. In the protective atmosphere furnace, the tube blank is heated at a temperature of 900°C and kept warm for 60 minutes. Then, it is cooled by spraying water inside and outside at a cooling rate of 30°C / s to obtain a martensitic structure; then, it is tempered at a temperature of 640°C for 120 minutes to obtain fine and uniform tempered bainite, and then water-cooled after tempering; then, it is heat straightened at a temperature of 590°C and then water-cooled; after thread processing, the heavy oil hot-adopted petroleum casing is obtained.

[0092] Example 2

[0093] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0094] Steelmaking: The difference from Example 1 is that the ingredients are prepared according to the composition of the heavy oil hot-using casing of Example 2 shown in Table 1;

[0095] Continuous casting: same as in Example 1;

[0096] Piercing and hot rolling: same as in Example 1;

[0097] Tempering heat treatment and heat straightening: same as in Example 1.

[0098] Example 3

[0099] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0100] Steelmaking: The difference from Example 1 is that the ingredients are prepared according to the composition of the heavy oil hot-using casing of Example 3 shown in Table 1;

[0101] Continuous casting: same as in Example 1;

[0102] Piercing and hot rolling: same as in Example 1;

[0103] Tempering heat treatment and heat straightening: same as in Example 1.

[0104] Example 4

[0105] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0106] Steelmaking: The only difference from Example 1 is that the heavy oil heat-using casing of Example 4 is dosed according to the composition shown in Table 1;

[0107] Continuous casting: same as in Example 1;

[0108] Piercing and hot rolling: same as in Example 1;

[0109] Tempering heat treatment and heat straightening: The only difference from Example 1 is that tempering is performed at a temperature of 630°C; and heat straightening is performed at a temperature of 580°C.

[0110] Example 5

[0111] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0112] Steelmaking: The only difference from Example 4 is that the heavy oil heat-using casing of Example 5 is dosed according to the composition shown in Table 1;

[0113] Continuous casting: same as Example 4;

[0114] Piercing and hot rolling: same as in Example 4;

[0115] Tempering heat treatment and heat straightening: same as in Example 4.

[0116] Example 6

[0117] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0118] Steelmaking: The only difference from Example 4 is that the heavy oil heat-using casing of Example 6 is dosed according to the composition shown in Table 1;

[0119] Continuous casting: same as Example 4;

[0120] Piercing and hot rolling: same as in Example 4;

[0121] Tempering heat treatment and heat straightening: same as in Example 4.

[0122] Example 7

[0123] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0124] Steelmaking: The only difference from Example 1 is that the heavy oil heat-using casing of Example 7 is dosed according to the composition shown in Table 1;

[0125] Continuous casting: same as in Example 1;

[0126] Piercing and hot rolling: same as in Example 1;

[0127] Tempering heat treatment and heat straightening: The only difference from Example 1 is that tempering is performed at a temperature of 620°C; and heat straightening is performed at a temperature of 570°C.

[0128] Example 8

[0129] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0130] Steelmaking: The only difference from Example 7 is that the heavy oil heat-using casing of Example 8 is dosed according to the composition shown in Table 1;

[0131] Continuous casting: same as Example 7;

[0132] Piercing and hot rolling: same as in Example 7;

[0133] Tempering heat treatment and heat straightening: same as Example 7.

[0134] Example 9

[0135] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0136] Steelmaking: The only difference from Example 7 is that the heavy oil heat-using casing of Example 9 is dosed according to the composition shown in Table 1;

[0137] Continuous casting: same as Example 7;

[0138] Piercing and hot rolling: same as in Example 7;

[0139] Tempering heat treatment and heat straightening: same as Example 7.

[0140] Example 10

[0141] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0142] Steelmaking: The only difference from Example 1 is that the heavy oil heat-using casing of Example 10 is dosed according to the composition shown in Table 1;

[0143] Continuous casting: same as in Example 1;

[0144] Piercing and hot rolling: same as in Example 1;

[0145] Tempering heat treatment and heat straightening: The only difference from Example 1 is that tempering is performed at a temperature of 610°C; and heat straightening is performed at a temperature of 560°C.

[0146] Example 11

[0147] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0148] Steelmaking: The only difference from Example 10 is that the heavy oil hot-using casing of Example 11 is dosed according to the composition shown in Table 1;

[0149] Continuous casting: same as Example 10;

[0150] Piercing and hot rolling: same as in Example 10;

[0151] Tempering heat treatment and heat straightening: same as Example 10.

[0152] Example 12

[0153] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0154] Steelmaking: The only difference from Example 10 is that the heavy oil hot-using casing of Example 12 is dosed according to the composition shown in Table 1;

[0155] Continuous casting: same as Example 10;

[0156] Piercing and hot rolling: same as in Example 10;

[0157] Tempering heat treatment and heat straightening: same as Example 10.

[0158] Example 13

[0159] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0160] Steelmaking: The only difference from Example 1 is that the heavy oil heat-using casing of Example 13 is dosed according to the composition shown in Table 1;

[0161] Continuous casting: same as in Example 1;

[0162] Piercing and hot rolling: same as in Example 1;

[0163] Tempering heat treatment and heat straightening: The only difference from Example 1 is that tempering is performed at a temperature of 600°C; and heat straightening is performed at a temperature of 550°C.

[0164] Example 14

[0165] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0166] Steelmaking: The only difference from Example 13 is that the heavy oil hot-using casing of Example 14 is dosed according to the composition shown in Table 1;

[0167] Continuous casting: same as Example 13;

[0168] Piercing and hot rolling: same as in Example 13;

[0169] Tempering heat treatment and heat straightening: same as Example 13.

[0170] Example 15

[0171] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0172] Steelmaking: The only difference from Example 13 is that the heavy oil hot-using casing of Example 15 is dosed according to the composition shown in Table 1;

[0173] Continuous casting: same as Example 13;

[0174] Piercing and hot rolling: same as in Example 13;

[0175] Tempering heat treatment and heat straightening: same as Example 13.

[0176] Example 16

[0177] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0178] Steelmaking: The only difference from Example 1 is that the heavy oil heat-using casing of Example 16 is dosed according to the composition shown in Table 1;

[0179] Continuous casting: same as in Example 1;

[0180] Piercing and hot rolling: same as in Example 1;

[0181] Tempering heat treatment and heat straightening: The only difference from Example 1 is that tempering is performed at a temperature of 585°C; and heat straightening is performed at a temperature of 530°C.

[0182] Example 17

[0183] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0184] Steelmaking: The only difference from Example 16 is that the heavy oil heat-using casing of Example 17 is dosed according to the composition shown in Table 1;

[0185] Continuous casting: same as Example 16;

[0186] Piercing and hot rolling: same as in Example 16;

[0187] Tempering heat treatment and heat straightening: same as Example 16.

[0188] Example 18

[0189] A method for preparing a heavy oil hot-using petroleum casing comprises the following steps:

[0190] Steelmaking: The only difference from Example 16 is that the heavy oil hot use casing of Example 18 is dosed according to the composition shown in Table 1;

[0191] Continuous casting: same as Example 16;

[0192] Piercing and hot rolling: same as in Example 16;

[0193] Tempering heat treatment and heat straightening: same as Example 16.

[0194] The heavy oil hot-use casings prepared in Examples 1-18 were subjected to tensile property tests at room temperature and 350°C, including yield strength test, tensile strength test, total elongation test, uniform elongation test, and Charpy V-notch impact toughness test at 0°C. The results are shown in Tables 2 and 3 below.

[0195] Table 2. Room temperature tensile properties and impact toughness at 0°C of the heavy oil hot-use casings prepared in Examples 1-18

[0196]

[0197]

[0198] Table 3. Tensile properties of the heavy oil hot-using casings prepared in Examples 1-18 at 350°C

[0199]

[0200]

[0201] In the table, 120SH, 125SH, 130SH, 135SH, 140SH and 150SH correspond to steel grades of 120ksi, 125ksi, 130ksi, 135ksi, 140ksi and 150ksi casing respectively.

[0202] The above results show that the heavy oil hot-using casing provided by the present invention has high strength and sufficient elongation, and has excellent comprehensive performance, as shown below:

[0203] At room temperature, the yield strength of 120SH heavy oil hot-dip casing is 880-885 MPa, the tensile strength is 989-994 MPa, the yield strength ratio is 0.89, the total elongation is 26%, the uniform elongation is 15%; the Charpy V-notch impact toughness at 0°C is 120-122 J.

[0204] At room temperature, the yield strength of 125SH heavy oil hot-dip casing is 915-920 MPa, the tensile strength is 1028-1034 MPa, the yield strength ratio is 0.89, the total elongation is 25.4%-25.6%, and the uniform elongation is 14.4%-14.6%; the Charpy V-notch impact toughness at 0°C is 116-119 J.

[0205] At room temperature, the yield strength of 130SH heavy oil hot-dip casing is 949-955 MPa, the tensile strength is 1066-1073 MPa, the yield strength ratio is 0.89, the total elongation is 25%, the uniform elongation is 14%; the Charpy V-notch impact toughness at 0°C is 113-115 J.

[0206] At room temperature, the yield strength of 135SH heavy oil hot-dip casing is 984-989 MPa, the tensile strength is 1106-1111 MPa, the yield strength ratio is 0.89, the total elongation is 24.5%-24.6%, and the uniform elongation is 13.4%-13.6%; the Charpy V-notch impact toughness at 0°C is 108-110 J.

[0207] At room temperature, the yield strength of 140SH heavy oil hot-dip casing is 1018-1024 MPa, the tensile strength is 1131-1138 MPa, the yield strength ratio is 0.90, the total elongation is 24%, the uniform elongation is 13%; the Charpy V-notch impact toughness at 0°C is 105-108 J.

[0208] At room temperature, the yield strength of 150SH heavy oil hot-dip casing is 1087-1093 MPa, the tensile strength is 1208-1214 MPa, the yield strength ratio is 0.90, the total elongation is 23%, the uniform elongation is 12%; the Charpy V-notch impact toughness at 0°C is 101-104 J.

[0209] The heavy oil thermal recovery casing in each embodiment exhibits a yield strength drop of approximately 15% and a tensile strength drop of approximately 12% at 350°C compared to room temperature, meeting the relevant standard requirement of a strength drop of no more than 20%. This further reduces the yield strength ratio, increases the total elongation and uniform elongation, and enhances operational safety. This meets the casing strength, plasticity, and strain fatigue life requirements for heavy oil steam thermal recovery wells.

[0210] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, 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

1. A heavy oil heat utilization casing, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.20%~0.30%, Si 1.00%~1.15%, Mn 1.20%~1.33%, Cr 0.60%~0.85%, Mo 0.33%~0.48%, Nb 0.03%~0.10%, RE 0.001%~0.004%, Al 0.010%~0.030%, Ca 0.012%~0.025%, P≤0.015%, S≤0.005%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

2. The heavy oil heat utilization casing according to claim 1, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.20%~0.22%, Si 1.00%~1.02%, Mn 1.20%~1.22%, Cr 0.60%~0.65%, Mo 0.33%~0.35%, Nb 0.03%~0.05%, RE 0.001%~0.002%, Al 0.010%~0.014%, Ca 0.012%~0.014%, P≤0.012%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

3. The heavy oil heat utilization casing according to claim 1, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.21%~0.23%, Si 1.03%~1.05%, Mn 1.21%~1.23%, Cr 0.66%~0.69%, Mo 0.34%~0.36%, Nb 0.04%~0.06%, RE 0.002%~0.003%, Al 0.015%~0.017%, Ca 0.015%~0.017%, P≤0.012%, S≤0.003%, N≤0.004%, O+H+N≤0.006%, and the balance is Fe and unavoidable impurities.

4. The heavy oil heat utilization casing according to claim 1, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.21%~0.24%, Si 1.05%~1.08%, Mn 1.22%~1.24%, Cr 0.71%~0.75%, Mo 0.37%~0.39%, Nb 0.05%~0.07%, RE 0.002%~0.003%, Al 0.018%~0.020%, Ca 0.016%~0.018%, P≤0.011%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

5. The heavy oil heat utilization casing according to claim 1, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.23%~0.25%, Si 1.09%~1.11%, Mn 1.25%~1.27%, Cr 0.76%~0.79%, Mo 0.40%~0.42%, Nb 0.06%~0.08%, RE 0.003%~0.004%, Al 0.021%~0.024%, Ca 0.018%~0.020%, P≤0.012%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

6. The heavy oil heat utilization casing according to claim 1, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.25%~0.27%, Si 1.12%~1.14%, Mn 1.28%~1.30%, Cr 0.81%~0.83%, Mo 0.43%~0.45%, Nb 0.07%~0.09%, RE 0.003%, Al 0.025%~0.027%, Ca 0.021%~0.023%, P≤0.011%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

7. The heavy oil heat utilization casing according to claim 1, characterized in that: Calculated by mass percentage, the heavy oil thermal casing comprises the following chemical components: C 0.28%~0.30%, Si 1.13%~1.15%, Mn 1.31%~1.33%, Cr 0.83%~0.85%, Mo 0.46%~0.48%, Nb 0.08%~0.10%, RE 0.004%, Al 0.028%~0.030%, Ca 0.023%~0.025%, P≤0.010%, S≤0.003%, N≤0.005%, O+H+N≤0.007%, and the balance is Fe and unavoidable impurities.

8. A method for preparing a heavy oil hot-using casing, characterized in that: Including steps: The heavy oil hot-using casing according to any one of claims 1 to 7 is subjected to batching, smelting, and continuous casting to obtain a continuous casting billet; The continuous casting billet is subjected to hot piercing and hot continuous rolling to obtain a tube billet; The tube blank is subjected to tempering heat treatment, heat straightening and then thread processing to obtain the heavy oil hot-using casing.

9. The preparation method according to claim 8, characterized in that After smelting and continuous casting, a continuous casting billet is obtained; after hot piercing and hot rolling the continuous casting billet, a tube billet is obtained. The steps specifically include: The raw materials obtained by batching are sequentially subjected to oxygen-blown converter smelting, RE wire feeding, external refining, vacuum degassing, and Si-Ca wire feeding for modification of inclusions to obtain molten steel; Casting the molten steel into a rod-shaped continuous casting billet; The continuous casting billet is heated to 1180-1230° C. in a heating furnace, kept warm for 90-120 minutes, then hot-pierced at 1170-1200° C., hot-rolled at 950-1150° C., and cooled to obtain a tube billet.

10. The preparation method according to claim 8, characterized in that The steps of subjecting the tube blank to quenching and tempering heat treatment, heat straightening, and then threading to obtain the heavy oil hot-using casing specifically include: In a protective atmosphere furnace, the tube blank is heated at a temperature of 890-910° C., kept at that temperature for 40-60 minutes, and then cooled by spraying water inside and outside at a cooling rate of 30° C. / s or higher. The tube blank is then tempered at a temperature of 585-640° C. for 90-120 minutes and then water-cooled. The tube blank is then hot-straightened at a temperature of 530-590° C. and then water-cooled. After thread processing, the heavy oil hot-adopting casing is obtained.

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