Stainless steel oil casing for carbon dioxide flooding enhanced oil extraction and manufacturing method of stainless steel oil casing

Abstract

The invention belongs to the technical field of carbon dioxide storage and utilization, and particularly relates to a stainless steel oil casing for carbon dioxide flooding enhanced oil extraction and a manufacturing method thereof. The stainless steel oil casing comprises the following chemical components in percentage by weight: less than or equal to 0.03% of C, 0.15%-0.3% of Si, less than or equal to 0.010% of P, less than or equal to 0.005% of S, 14.0%-18.0% of Cr, 0.5%-2% of Mn, 2.0%-3% of Ni, 1.0%-3.0% of Mo, 0.20%-0.30% of N, 0.5%-1.0% of Cu, 0.025%-0.1% of Nb, 0.015%-0.025% of V, 0.001%-0.003% of Ca, 0.01%-0.03% of Re and the balance of Fe and inevitable impurities. The yield strength of the stainless steel oil casing ranges from 758 MPa to 931 MPa, the tensile strength is larger than 862 MPa, the ductility is larger than or equal to 30%, the stainless steel oil casing has good obdurability matching and excellent corrosion resistance and low-temperature impact toughness, the applicable service temperature range is-50 DEG C to 180 DEG C, the stainless steel oil casing can be applied to the low-temperature environment caused by injection-production yield increase after carbon dioxide capture, and the service life of the stainless steel oil casing is prolonged. And two or three of carbon dioxide, hydrogen sulfide and chloride ions coexist in the corrosive medium working condition.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide storage and utilization, and particularly relates to a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding and a manufacturing method thereof. Background Art

[0002] As one of the carbon dioxide utilization and storage technologies, the CO2-EOR oil recovery technology geologically stores and utilizes carbon dioxide by means of mutual dissolution of carbon dioxide and crude oil, and at the same time achieves the purpose of increasing crude oil production and reducing carbon dioxide emissions during crude oil extraction. It has become a technical means for the main carbon dioxide capture, utilization and storage engineering projects in China. However, during the CO2-EOR oil recovery process, the injection of carbon dioxide causes the pipe string to be in a low-temperature environment. When carbon dioxide is injected into the well, especially in an environment with a high water content, a small amount of hydrogen sulfide or a large amount of chloride ions, etc., it will increase the risk of corrosion failure of the pipe string.

[0003] In the working environment of carbon dioxide injection, conventional low-alloy steel oil casings are prone to corrosion and cracking. At present, the existing stainless steel oil well pipe products are typically represented by Cr-Mo-Ni series martensitic stainless steels. Typical representative products include grades such as Super13Cr and HP 13Cr. Alloying technology means are mainly used to improve their comprehensive mechanical properties, and the price is expensive. Therefore, developing oil well pipe products with good low-temperature toughness, good corrosion resistance to carbon dioxide and relatively economical is of great engineering significance for solving the corrosion problem under harsh service conditions in CO2-EOR oil recovery. Summary of the Invention

[0004] In view of the above problems, the purpose of the present invention is to provide a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding and a manufacturing method thereof. The yield strength of the stainless steel oil casing of the present invention is 758 MPa to 931 MPa, the tensile strength is greater than 862 MPa, the elongation is ≥30%, the full-size longitudinal impact energy at -10°C is ≥130 J, and the full-size longitudinal impact energy at -50°C is ≥80 J. The structure is martensite structure. The product not only has good strength and toughness matching, but also excellent corrosion resistance and low-temperature impact toughness. The applicable service temperature range is -50°C to 180°C, and it can be applied to the low-temperature environment caused by post-injection production increase after carbon dioxide capture, as well as the corrosion medium working conditions where two or three of carbon dioxide, hydrogen sulfide and chloride ions coexist.

[0005] The technical solution of the present invention is: a stainless steel oil casing for carbon dioxide flooding enhanced oil recovery, the chemical composition of the stainless steel oil casing is as follows by weight percentage: C: ≤0.03%, Si: 0.15%~0.3%, P: ≤0.010%, S: ≤0.005%, Cr: 14.0%~18.0%, Mn: 0.5%~2%, Ni: 2.0%~3%, Mo: 1.0%~3.0%, N: 0.20%~0.30%, Cu: 0.5%~1.0%, Nb: 0.025%~0.1%, V: 0.015%~0.025%, Ca: 0.001%~0.003%, Re: 0.01%~0.03%, and the balance is Fe and unavoidable impurities.

[0006] The contents of the chemical elements Mn, N, Ni and Cu of the stainless steel oil casing satisfy the following in weight percentage: 5.5≤0.5A1+16A2+A3+0.3A4≤7.8, wherein A1, A2, A3 and A4 are the weight percentages of Mn, N, Ni and Cu elements respectively.

[0007] The contents of Nb and V in the chemical elements of the stainless steel oil casing satisfy the following in weight percentage: 0.04<B1+B2<0.12, wherein B1 and B2 are the weight percentages of Nb and V elements respectively.

[0008] The stainless steel oil casing has a yield strength of 758MPa-931MPa, a tensile strength greater than 862MPa, an elongation ≥30%, a full-size longitudinal impact energy ≥130J at -10°C, and a full-size longitudinal impact energy ≥80J at -50°C.

[0009] The stainless steel oil casing has a microstructure of martensite, and the volume content of martensite is greater than 95%.

[0010] The chemical composition of the stainless steel casing for enhanced oil recovery by carbon dioxide flooding is selected based on: C: Carbon is the main solid solution strengthening element and has an important influence on the strength of steel materials. However, when the carbon content is high, it can form carbides such as M23C6 with chromium and molybdenum elements, which deteriorates the processing performance, toughness and corrosion resistance of stainless steel, and also reduces the solubility of nitrogen in the melt. In order to achieve the purpose of the present invention, the C content is controlled to ≤0.03%.

[0011] Si: Silicon mainly plays a deoxidizing role. When its content is high, it promotes the formation of inclusions and the precipitation of harmful compounds, which is detrimental to the toughness and corrosion resistance of stainless steel. Therefore, the lower the content, the better, and it is limited to 0.15~0.30%.

[0012] Mn: Manganese can promote the dissolution of nitrogen and cooperate with nitrogen to facilitate the formation of austenite, significantly improving the hot working performance of stainless steel and enhancing its strength and toughness. At the same time, substituting part of the nickel element with manganese and nitrogen can reduce the cost of stainless steel alloys. However, too high a manganese content will reduce the corrosion resistance of martensitic stainless steel. To achieve the purpose of the invention, the designed range is 0.5 - 2%.

[0013] N: Nitrogen is one of the important elements in the martensitic stainless steel of the present invention. It can act synergistically with elements such as chromium and molybdenum, significantly improving the corrosion resistance of stainless steel, enhancing its strength, and also significantly inhibiting the precipitation of harmful phases to improve the tissue stability of the steel. Moreover, it can replace part of the nickel element to save the cost of stainless steel alloys. However, when the content is high, it will reduce the hot working performance of stainless steel, promote the precipitation of nitrides, and deteriorate the toughness and corrosion resistance of stainless steel. To achieve the purpose of the invention, the designed range is 0.2 - 0.3%.

[0014] Cr: Chromium is one of the main alloying elements of martensitic stainless steel. It promotes grain refinement and improves the corrosion resistance of stainless steel. However, when the content is too high, it is easy to promote the precipitation of nitrides and intermetallic compounds, significantly reducing the mechanical properties and corrosion resistance. Therefore, the chromium content is controlled between 14% and 18%.

[0015] Mo: Molybdenum significantly improves the corrosion resistance of stainless steel, promotes the formation of the surface passivation film, and increases the solubility of nitrogen, inhibiting the precipitation of nitrides. However, when the content is high, it promotes the precipitation of intermetallic compounds, deteriorating the hot working performance, mechanical properties, and corrosion resistance of stainless steel. Therefore, in the present invention, its content is controlled between 1.0 and 3.0%.

[0016] Ni: Nickel forms and stabilizes the austenite phase, significantly improving the corrosion resistance of stainless steel in reducing corrosive media, increasing the solubility of chromium and molybdenum in the steel, inhibiting the precipitation of intermetallic compounds, improving the tissue stability, making the strength and toughness of the steel reasonably matched, and also improving the performance of the chromium oxide film. However, when the nickel content is high, it not only reduces the solubility of nitrogen in stainless steel but also is scarce and expensive, significantly increasing the cost of stainless steel. Therefore, in the present invention, its content is controlled between 2.0 and 3.0%.

[0017] Cu: Copper can significantly reduce the work hardening rate of stainless steel, improving its plasticity and processing and forming performance. An appropriate amount of copper can promote the formation of the protective passivation film of chromium and enhance the self - repair ability of the film, thereby improving the corrosion resistance of stainless steel. Therefore, in the present invention, its content is controlled between 0.5 and 1.0%.

[0018] P, S: Sulfur and phosphorus are regarded as harmful impurity elements in austenitic stainless steel, which reduce the grain boundary bonding force and significantly degrade the hot working performance, corrosion resistance and mechanical properties of stainless steel. Therefore, the content control levels of sulfur and phosphorus should be reduced as much as possible. In this invention, it is specified that P ≤ 0.010% and S ≤ 0.005%.

[0019] Nb, Ti: Niobium and titanium have similar functions in stainless steel. Both can form C and N compounds, refine the grains, increase the strength of the steel, and also inhibit the formation of other types of precipitation phases. However, when the content is high, a large amount of carbonitride compounds are formed, deteriorating the plasticity, toughness and corrosion resistance. Therefore, in this invention, their content is controlled as follows: V: 0.015% - 0.025%, Nb: 0.025% - 0.1%.

[0020] Ca: Calcium can form sulfides with sulfur, improving the morphology of sulfide inclusions, which is very beneficial to enhancing the toughness of the steel. To achieve the purpose of the invention, the designed range of Ca content is 0.001 - 0.003%.

[0021] Re: Adding rare earth elements can significantly purify the molten steel, improve the purity of stainless steel, and has the functions of purifying grain boundaries, strengthening grain boundaries and refining grains. Therefore, in this invention, the mixed rare earth of lanthanum (La), cerium (Ce) and yttrium (Y) is added, with a ratio of 40%:30%:30%, and the preferred content of Re is 0.01 - 0.03%.

[0022] A manufacturing method of a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding. To manufacture a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding as described above, the following steps are included: S1: Conduct stainless steel smelting, deoxidation and nitrogen alloying under a nitrogen protection atmosphere to prepare a stainless steel ingot, and then perform elemental analysis, flaw detection and machining treatment to remove surface defects and black skin. S2: Reheat the ingot to above 1100°C and perform radial forging on the ingot with a large rolling ratio, where the radial reduction ratio is greater than 2. S3: After forging, use the hot piercing method to prepare the forged billet into a rough tube for oil pipe or casing, and then use the multi-pass hot rolling method to prepare it into a tube blank of the required specification for oil pipe or casing. S4: Heat the tube blank of the required specification after hot rolling to 100°C - 150°C above the AC3 phase transformation point, hold for a certain time, and then perform quenching treatment under the condition of rotary water cooling until it cools to room temperature. Then heat the steel pipe to 250°C - 300°C below the AC3 phase transformation point for tempering treatment and perform high-temperature straightening. S5: Perform non-destructive flaw detection on the entire tube body of the heat-treated tube blank. After the flaw detection is qualified, perform surface pickling, threading at the tube end, screwing on the coupling, hydrostatic test, installing the protection ring, spraying the label and painting to make the finished stainless steel oil casing.

[0023] In S4, the quenching heat treatment temperature is 980°C to 1030°C, and the holding time is 35 min to 45 min; the tempering heat treatment temperature is 600°C to 700°C, and the holding time is 45 min to 60 min.

[0024] The technical effects of the present invention are as follows: 1. The present invention uses inexpensive nitrogen element to replace part of the expensive nickel element and adds appropriate alloying elements, which not only reduces the cost of stainless steel alloy to a certain extent, improves the strength-toughness matching of the material, enhances the plastic toughness of the material, especially the low-temperature toughness, but also has good corrosion resistance at the same time. 2. The oil casing of the present invention meets the mechanical property requirements of 110 ksi steel grade oil casing, with a yield strength of 758 MPa to 931 MPa, a tensile strength greater than 862 MPa, an elongation rate ≥ 30%, a full-size longitudinal impact energy ≥ 130 J at -10°C, and a full-size longitudinal impact energy ≥ 80 J at -50°C, and the microstructure is martensite. 3. The oil casing product of the present invention not only has good strength-toughness matching, but also excellent corrosion resistance and low-temperature impact toughness, and is applicable to the service temperature range of -50°C to 180°C, and can be applied to the low-temperature environment caused by enhanced oil recovery after carbon dioxide capture injection, as well as the working conditions of corrosion media coexisting with two of carbon dioxide, hydrogen sulfide or chloride ions. Detailed implementation manners

[0025] Example 1

[0026] A stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding, the chemical composition of the stainless steel oil casing by weight percentage is: C: ≤ 0.03%, Si: 0.15% - 0.3%, P: ≤ 0.010%, S: ≤ 0.005%, Cr: 14.0% - 18.0%, Mn: 0.5% - 2%, Ni: 2.0% - 3%, Mo: 1.0% - 3.0%, N: 0.20% - 0.30%, Cu: 0.5% - 1.0%, Nb: 0.025% - 0.1%, V: 0.015% - 0.025%, Ca: 0.001% - 0.003%, Re: 0.01% - 0.03%, and the balance is Fe and inevitable impurities.

[0027] The present invention uses inexpensive nitrogen element to replace part of the expensive nickel element and adds appropriate alloying elements, which not only reduces the cost of stainless steel alloy to a certain extent, improves the strength-toughness matching of the material, enhances the plastic toughness of the material, especially the low-temperature toughness, but also has good corrosion resistance at the same time.

[0028] The contents of chemical elements Mn, N, Ni and Cu in the stainless steel oil casing meet the following by weight percentage: 5.5 ≤ 0.5A1 + 16A2 + A3 + 0.3A4 ≤ 7.8, where A1, A2, A3 and A4 are the weight percentages of Mn, N, Ni and Cu elements respectively.

[0029] The contents of chemical elements Mn, N, Ni and Cu in the stainless steel oil casing pipe satisfy by weight percentage: 5.5 ≤ 0.5A1 + 16A2 + A3 + 0.3A4 ≤ 7.8, where A1, A2, A3 and A4 are the weight percentages of Mn, N, Ni and Cu elements respectively. This can not only effectively exert the strengthening effect and corrosion resistance improvement effect of alloy elements such as Mn, N, Ni and Cu in the pipe, effectively control the content of Ni element, and realize the substitution of Mn and N elements for Ni element; but also can reduce the cost of alloy elements added to the pipe to a certain extent, avoid the reduction of plastic toughness and corrosion performance caused by too high N element content, so as to achieve the combination of economy and excellent performance of the stainless steel oil casing pipe.

[0030] The contents of chemical elements Nb and V in the stainless steel oil casing pipe satisfy by weight percentage: 0.04 < B1 + B2 < 0.12, where B1 and B2 are the weight percentages of Nb and V elements respectively.

[0031] The contents of chemical elements Nb and V in the stainless steel oil casing pipe satisfy by weight percentage: 0.04 < B1 + B2 < 0.12, where B1 and B2 are the weight percentages of Nb and V elements respectively. This can not only play the role of refining the grain and strengthening the original austenite during the pipe manufacturing process by Nb and V elements, but also avoid the formation of coarsened and continuous precipitation phases of Nb, V elements and other complex carbonitrides at grain boundaries and other positions during the tempering process, resulting in the deterioration of plastic toughness and corrosion performance.

[0032] The yield strength of the stainless steel oil casing pipe is 758 MPa - 931 MPa, the tensile strength is greater than 862 MPa, the elongation is ≥ 30%, the full-size longitudinal impact energy at -10 °C is ≥ 130 J, and the full-size longitudinal impact energy at -50 °C is ≥ 80 J.

[0033] The microstructure of the stainless steel oil casing pipe is martensite structure, and the volume content of martensite structure is greater than 95%. Example 2

[0034] A manufacturing method of a stainless steel oil casing pipe for enhanced oil recovery by carbon dioxide flooding, manufacturing a stainless steel oil casing pipe for enhanced oil recovery by carbon dioxide flooding as described above, including the following steps: S1: Conduct stainless steel smelting, deoxidation and nitrogen alloying under a nitrogen protection atmosphere to prepare a stainless steel ingot, and then conduct element analysis, flaw detection and machining treatment to remove surface defects and black skin; S2: Reheat the ingot to above 1100 °C, and perform radial forging on the ingot with a large rolling ratio, and the radial reduction ratio is greater than 2; S3: After forging, the forged billet is made into a rough pipe of tubing or casing by hot piercing, and then the rough pipe is made into a pipe blank of tubing or casing with the required specifications by multi-pass hot rolling; S4: Heat the pipe blank with the required specifications after hot rolling to 100°C - 150°C above the AC3 phase transformation point, hold for a certain time, and then perform quenching treatment under the condition of rotary water cooling. Cool to room temperature, and then heat the steel pipe to 250°C - 300°C below the AC3 phase transformation point for tempering treatment, and perform high-temperature straightening; S5: Perform non-destructive testing on the entire pipe body of the pipe blank after heat treatment. After passing the inspection, perform surface pickling, threading at the pipe end, screwing of couplings, hydrostatic test, installation of protective rings, spraying of marks and painting to make the finished stainless steel oil casing.

[0035] In the S4, the quenching heat treatment temperature is 980°C - 1030°C, and the holding time is 35 min - 45 min; the tempering heat treatment temperature is 600°C - 700°C, and the holding time is 45 min - 60 min.

[0036] The oil casing of the present invention meets the mechanical property requirements of 110 ksi grade oil casing. The yield strength is 758 MPa - 931 MPa, the tensile strength is greater than 862 MPa, the elongation is ≥ 30%, the full-size longitudinal impact energy at -10°C is ≥ 130 J, the full-size longitudinal impact energy at -50°C is ≥ 80 J, and the structure is martensite structure. The oil casing product of the present invention not only has good strength and toughness matching, but also excellent corrosion resistance and low-temperature impact toughness. The applicable service temperature range is -50°C - 180°C, and it can be applied to the low-temperature environment caused by enhanced injection and production after carbon dioxide capture, as well as the working conditions of corrosion media with the coexistence of carbon dioxide, hydrogen sulfide or chloride ions, etc.

[0037] Adopt the manufacturing method of a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding as described in Example 2 to manufacture a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding as described in Example 1, specifically as in Examples 3 - 5 and Comparative Examples 1 - 3. The mass percentages (wt%) of the melting chemical elements of the stainless steel oil casing are shown in Table 1.

[0038] Table 1 Melting chemical compositions of the stainless steel oil casings of Examples 3 - 5 and Comparative Examples 1 - 3 of the present invention

[0039] As can be seen from Table 1: In Examples 3-5 of the present invention, the steel for stainless steel oil casings controls the elements C, Cr, Ni, and Mo, appropriately adds the elements Mn and N to replace the Ni element, and simultaneously adds elements such as Nb, V, Cu, and Re, while strictly controlling elements such as S, P, and Ca. In Comparative Examples 1-3, in Comparative Example 1, the C content was increased, the Mn element was not added, and the expensive nickel content was reduced; in Comparative Example 2, the Mn and N elements were increased, and the expensive nickel element was not added; in Comparative Example 3, a relatively high Ni element was added, while the inexpensive Mn and N elements were not added.

[0040] The manufacturing methods of the stainless steel oil casings in Examples 3-5 and Comparative Examples 1-3 are as follows, and the specific process parameters for the billet manufacturing are shown in Table 2.

[0041] Step 1: Smelt, deoxidize, and nitrogen alloy the designed components in Table 1 under a nitrogen protection atmosphere to prepare a stainless steel ingot, and then perform elemental analysis, flaw detection, and machining treatment to remove surface defects and black skin. Step 2: Reheat the ingot to above 1100 °C, and perform radial forging on the ingot with a large rolling ratio, where the radial reduction ratio is greater than 2. Step 3: After forging, use the hot piercing method to prepare the forged billet into a rough tube for an oil pipe or a casing, and then use the multi-pass hot rolling method to prepare the rough tube for the oil pipe or the casing with the required specifications. Step 4: Heat the rough tube with the required specifications after hot rolling to 100 °C - 150 °C above the AC3 phase change point, hold for a certain time, and then perform quenching treatment under the condition of rotating water cooling until it cools to room temperature. Then, heat the steel pipe to 250 °C - 300 °C below the AC3 phase change point for tempering treatment and perform high-temperature straightening. Step 5: Perform non-destructive flaw detection on the entire tube body of the billet after heat treatment. After passing the flaw detection, perform surface pickling, pipe end threading, coupling screwing, hydrostatic test, installing a protective ring, spraying marks, and painting to make a finished stainless steel oil casing.

[0042] Table 2 Process parameters for manufacturing the billets of the stainless steel oil casings in Examples 3-5 and Comparative Examples 1-3 of the present invention

[0043] The mechanical properties and corrosion properties of Examples 3-5 and Comparative Examples 1-3 are shown in Table 3 and Table 4 below. Table 3 shows the mechanical property test results of the stainless steel in the examples of the present invention and the steel pipes in the comparative examples. After heat treatment, three test specimens were taken from each test steel to test its tensile strength, yield strength, and impact toughness. Table 4 shows the uniform corrosion performance of the stainless steel in the examples of the present invention and the comparative examples under different corrosion conditions. Three test specimens were taken to test their corrosion rates in a high-temperature and high-pressure autoclave, and the average corrosion rate of the three specimens was taken. Among them, the corrosion condition 1 was that the total test pressure was 12 MPa, the partial pressure of CO2 was 5 MPa, and Cl -The ion is 1.5×10 5 mg / L, the flow rate is 3 m / s, and the test temperature is 180°C; Corrosion condition 2 is that the total test pressure is 12 MPa, the CO2 partial pressure is 2.6 MPa, the H2S partial pressure is 0.01 MPa, and the test temperature is 120°C.

[0044] It can be seen from Table 3 that: in Examples 3 to 5, after the stainless steel oil casing pipe is processed by smelting, electroslag remelting, forging, pipe making and appropriate heat treatment processes using the chemical components described in the present invention, the yield strength of the stainless steel oil casing pipe is 780 MPa to 925 MPa, the tensile strength is 920 MPa to 1020 MPa, the elongation is 38% to 48%, the full-size longitudinal impact energy at -10°C is 135 J to 150 J, and the longitudinal impact energy at -50°C is 83 J to 98 J. In the comparative examples, the strength indexes of the steel pipes in Comparative Example 1 and Comparative Example 2 are respectively equivalent to those in Example 3 and Example 5, but their elongation and longitudinal impact energy at -10°C and -50°C are significantly lower than those in the examples of the present invention; although the mechanical properties and impact energy at -10°C of Comparative Example 3 are equivalent to those in Example 4, the low-temperature impact toughness at -50°C is slightly lower than that in Example 4, and its pipe material cost is higher than that in Example 4. It can be seen that the stainless steel oil casing pipe product of the present invention not only has excellent strength and toughness matching at normal temperature, but also has high impact toughness at low temperature, meets the service performance requirements of P110 steel grade oil casing pipes in the API 5CT standard, and can meet the low-temperature environment caused during the enhanced oil recovery injection process of carbon dioxide; moreover, it reduces the pipe material cost to a certain extent.

[0045] It can be seen from Table 3 and Table 4 that: the stainless steel oil casing pipes produced by the present invention in Examples 3 to 5 have an average corrosion rate of less than 0.01 mm / a under the test conditions of a total test pressure of 12 MPa, a CO2 partial pressure of 5 MPa, Cl - The ion is 1.5×10 5 mg / L, the flow rate is 3 m / s, and the average corrosion rate is less than 0.01 mm / a under the test temperature of 180°C. The average corrosion rate is less than 0.015 mm / a under the conditions of a total test pressure of 12 MPa, a CO2 partial pressure of 2.6 MPa, a H2S partial pressure of 0.01 MPa, and a test temperature of 120°C. In the comparative examples, the strength indexes of the steel pipes in Comparative Example 1 and Comparative Example 2 are respectively equivalent to those in Example 3 and Example 5, but the corrosion rates under the corrosion test conditions are significantly higher than those in Example 3 and Example 4; considering the test error, the corrosion rate of Comparative Example 3 is equivalent to the corrosion rates in the two working conditions of the examples, which also shows that the use of inexpensive Mn and N elements in the pipe material chemical composition can achieve the function of replacing expensive Ni elements while achieving comparable corrosion performance. It can be seen that the stainless steel oil casing pipe product of the present invention has excellent corrosion resistance and can be applied to the service conditions of oil and gas wells containing complex corrosion media such as a certain amount of hydrogen sulfide, carbon dioxide or chloride ions.

[0046] Table 3 Mechanical property test results of the test stainless steel oil casing pipes in Embodiments 3-5 and Comparative Examples 1-3 of the present invention

[0047] Table 4 Uniform corrosion performance of the stainless steel pipes in Embodiments 3-5 and Comparative Examples 1-3 of the present invention

[0048] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A stainless steel oil casing pipe for enhanced oil recovery by carbon dioxide flooding, characterized in that: The chemical composition of the stainless steel oil casing pipe by weight percentage is as follows: C: ≤0.03%, Si: 0.15% - 0.3%, P: ≤0.010%, S: ≤0.005%, Cr: 14.0% - 18.0%, Mn: 0.5% - 2%, Ni: 2.0% - 3%, Mo: 1.0% - 3.0%, N: 0.20% - 0.30%, Cu: 0.5% - 1.0%, Nb: 0.025% - 0.1%, V: 0.015% - 0.025%, Ca: 0.001% - 0.003%, Re: 0.01% - 0.03%, and the balance is Fe and unavoidable impurities.

2. The stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding according to claim 1, wherein: The contents of the chemical elements Mn, N, Ni, and Cu in the stainless steel oil casing pipe by weight percentage satisfy: 5.5 ≤ 0.5A1 + 16A2 + A3 + 0.3A4 ≤ 7.8, where A1, A2, A3, and A4 are the weight percentages of the elements Mn, N, Ni, and Cu respectively.

3. The stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding according to claim 1, wherein: The contents of the chemical elements Nb and V in the stainless steel oil casing pipe by weight percentage satisfy: 0.04 < B1 + B2 < 0.12, where B1 and B2 are the weight percentages of the elements Nb and V respectively.

4. The stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding according to claim 1, wherein: The yield strength of the stainless steel oil casing pipe is 758 MPa - 931 MPa, the tensile strength is greater than 862 MPa, the elongation is ≥30%, the full-size longitudinal impact energy at -10°C is ≥130 J, and the full-size longitudinal impact energy at -50°C is ≥80 J.

5. The stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding according to claim 1, wherein: The microstructure of the stainless steel oil casing pipe is martensite structure, and the volume content of the martensite structure is greater than 95%.

6. A manufacturing method of a stainless steel oil casing pipe for enhanced oil recovery by carbon dioxide flooding, for manufacturing a stainless steel oil casing pipe for enhanced oil recovery by carbon dioxide flooding as described in Claim 1, characterized in that: It includes the following steps: S1: Conduct stainless steel smelting, deoxidation, and nitrogen alloying under a nitrogen protection atmosphere to prepare a stainless steel ingot, and then conduct elemental analysis, flaw detection, and machining treatment to remove surface defects and black skin. S2: Reheat the ingot to above 1100°C, and perform radial forging on the ingot with a large rolling ratio, and the radial reduction ratio is greater than 2. S3: After forging, use the hot piercing method to prepare the forged billet into a rough pipe for oil pipe or casing, and then use the multi-pass hot rolling method to prepare the rough pipe into the required specification oil pipe or casing billet. S4: Heat the required specification billet after hot rolling to 100°C - 150°C above the AC3 phase transformation point, hold for a certain time, and then perform quenching treatment under the condition of rotating water cooling until cooled to room temperature. Then heat the steel pipe to 250°C - 300°C below the AC3 phase transformation point for tempering treatment and perform high-temperature straightening. S5: Conduct full-body non-destructive flaw detection on the heat-treated billet. After passing the flaw detection, perform surface pickling, pipe end threading, coupling screwing, hydrostatic test, installing a protective ring, spraying marks, and painting to make the finished stainless steel oil casing pipe.

7. The manufacturing method of a stainless steel oil casing for enhanced oil recovery by carbon dioxide flooding according to claim 6, characterized in that: In S4, the quenching heat treatment temperature is 980°C - 1030°C, the holding time is 35 min - 45 min, the tempering heat treatment temperature is 600°C - 700°C, and the holding time is 45 min - 60 min.

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