High-strength and high-toughness fracturing sliding sleeve for unconventional oil and gas development and preparation method thereof

Abstract

The application provides a high-strength and high-toughness fracturing sliding sleeve for unconventional oil and gas development and a preparation method, and the chemical components of the fracturing sliding sleeve are as follows in percentage by mass: C: 0.32%-0.36%, Si: 0.17%-0.37%, Mn: 0.40%-0.60%, P: less than or equal to 0.015%, S: less than or equal to 0.005%, Cr: 1.28%-1.38%, Ni: 1.30%-1.60%, Mo: 0.33%-0.48%, V: 0.03%-0.08%, Ce: 0.006%-0.010%, Al: 0.015%-0.025%, Ca: 0.015%-0.025%, N: less than or equal to 0.006%, O+H+N: less than or equal to 0.008%, and the balance is Fe and other inevitable impurities. The fracturing sliding sleeve is of 130ksi-150ksi steel grade, the minimum room temperature yield strength is 1012MPa-1143MPa, the tensile strength is 1112MPa-1229MPa, the elongation is 21%-25%, and the transverse Charpy V-notch impact toughness at-20 DEG C is 93J-118J. The fracturing sliding sleeve can meet the demand of unconventional oil and gas development on high-strength and high-toughness fracturing sliding sleeve.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of design and manufacture of fracturing sliding sleeves for oil and gas development, and particularly relates to a high-strength and high-toughness fracturing sliding sleeve for unconventional oil and gas development and a preparation method. BACKGROUND

[0002] With the development of unconventional oil and gas resources, horizontal well staged fracturing tools have also developed. In recent years, the non-intervention unlimited level well completion fracturing sliding sleeve system has been developed in the world and applied to the fracturing of shale oil and gas horizontal wells, becoming a new horizontal well staged fracturing tool. This technology has the characteristics of "stability and high efficiency", "convenient construction", "accurate modification", etc., and is widely used in the development of unconventional oil and gas such as shale oil and gas. So far, this technology has been used in more than 300 wells and more than 12000 levels at home and abroad, and has achieved good results, and has become one of the important tools and technologies for oil and gas well fracturing.

[0003] The non-intervention unlimited level fracturing system mainly consists of an unlimited level fracturing sliding sleeve, a soluble guide + screw clamp, a screw clamp launcher, and a monitoring system. The single well sliding sleeve has a full bore, and is connected with the sliding sleeve and then enters the well. After normal cementing and well completion, the fracturing operation is waited; during the fracturing operation, the soluble guide + screw clamp are pumped into the sliding sleeve to open the corresponding sliding sleeve, and then the fracturing operation is performed; during the fracturing operation, the screw clamp launcher is remotely operated to pump the screw clamp and the soluble ball into the sliding sleeve under pressure, so that continuous and non-stop pumping operation is realized; after the screw clamp enters the sliding sleeve, the monitoring system can real-time locate the position of the screw clamp and judge whether the target sliding sleeve is opened.

[0004] In the non-intervention unlimited level well completion fracturing sliding sleeve system, the sliding sleeve is connected with the casing string together, and is a main structural part. During the operation, the sliding sleeve bears complex combined loads such as tension, compression, bending, torsion and internal pressure. In order to ensure the safe and reliable use of the sliding sleeve, the sliding sleeve is required to have high strength and good toughness. However, the strength and toughness of the steel material are usually in a trade-off relationship, that is, when the strength of the material is high, the toughness is usually low, and vice versa. For the sliding sleeve material, the United States usually uses 4140H medium carbon Mn-Cr-Mo low alloy steel, and China usually uses 42CrMo medium carbon low alloy steel thick wall pipe, which are both subjected to quenching and tempering heat treatment. When the yield strength is about 1000 MPa or higher, the Charpy V-notch impact toughness is 40J-60J, and the longitudinal and transverse toughness difference is large, and the risk of brittle fracture of the sliding sleeve is large. In order to meet the requirements of reasonable matching of high strength and high toughness of the sliding sleeve, and overcome the shortcomings of the prior art, it is urgent to provide a new type of sliding sleeve material and preparation process. SUMMARY

[0005] Therefore, the present application aims to provide a high-strength and high-toughness fracturing sliding sleeve for unconventional oil and gas development and a preparation method thereof to overcome the shortcomings of the prior art.

[0006] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] A high-strength and high-toughness fracturing sliding sleeve for unconventional oil and gas development, the chemical composition of which comprises, by mass percentage, C: 0.32%-0.36%, Si: 0.17%-0.37%, Mn: 0.40%-0.60%, P≤0.015%, S≤0.005%, Cr: 1.28%-1.38%, Ni: 1.30%-1.60%, Mo: 0.33%-0.48%, V: 0.03%-0.08%, Ce: 0.006%-0.010%, Al: 0.015%-0.025%, Ca: 0.015%-0.025%, N≤0.006%, O+H+N≤0.008%, and the balance being Fe and other unavoidable impurities.

[0008] Preferably, the chemical composition comprises, by mass percentage, C: 0.32%-0.33%, Si: 0.17%-0.30%, Mn: 0.40%-0.47%, P≤0.015%, S≤0.005%, Cr: 1.28%-1.31%, Ni: 1.30%-1.41%, Mo: 0.33%-0.38%, V: 0.04%-0.05%, Ce: 0.006%-0.007%, Al: 0.015%-0.018%, Ca: 0.015%-0.018%, N≤0.006%, O+H+N≤0.008%, and the balance being Fe and other unavoidable impurities.

[0009] Preferably, the chemical composition comprises, by mass percentage, C: 0.33%-0.34%, Si: 0.23%-0.27%, Mn: 0.49%-0.53%, P≤0.015%, S≤0.005%, Cr: 1.32%-1.34%, Ni: 1.42%-1.48%, Mo: 0.40%-0.42%, V: 0.05%-0.06%, Ce: 0.007%-0.008%, Al: 0.019%-0.021%, Ca: 0.019%-0.022%, N≤0.006%, O+H+N≤0.008%, and the balance being Fe and other unavoidable impurities.

[0010] Preferably, the chemical composition is as follows: C: 0.35% to 0.36%, Si: 0.29% to 0.37%, Mn: 0.55% to 0.60%, P≤0.015%, S≤0.005%, Cr: 1.35% to 1.38%, Ni: 1.52% to 1.60%, Mo: 0.43% to 0.48%, V: 0.07% to 0.08%, Ce: 0.009% to 0.010%, Al: 0.022% to 0.025%, Ca: 0.021% to 0.025%, N≤0.006%, O+H+N≤0.008%, and the balance being Fe and other inevitable impurities.

[0011] The application also provides a method for preparing the high-strength and high-toughness fracturing sliding sleeve for unconventional oil and gas development, which comprises the following steps of steelmaking, continuous casting, hot continuous rolling, die forging, post-forging heat treatment, rough machining, heat treatment and thread machining.

[0012] The steelmaking (including external refining and vacuum degassing) comprises the following steps of batching, electric furnace or oxygen blowing converter steelmaking, external refining and vacuum degassing to obtain the above chemical composition, and feeding Si-Ca wires to perform deformation control treatment on inclusions in the steel.

[0013] The continuous casting comprises the following steps of pouring the molten steel into a rod-shaped continuous casting billet, and adopting electromagnetic stirring and light pressing down technology during the continuous casting to control center segregation of the continuous casting rod billet.

[0014] The hot continuous rolling comprises the following steps of heating the continuous casting billet in a ring-shaped heating furnace, heating the furnace at 1180-1230 °C, heating for 90-120 min, hot-rolling the rod at 900-1200 °C, and then air cooling.

[0015] Preferably, the die forging comprises the following steps of heating the hot-rolled rod to 1150-1180 °C, holding for 60-90 min, stamping a thick-walled pipe at 1000-1150 °C, air cooling, fine forging at 880-930 °C, and controlling the forging ratio to be greater than or equal to 5 to control segregation in the raw material. The post-forging heat treatment is performed by utilizing the residual heat of forging to combine the forging deformation and the heat treatment phase change, so that better strengthening and toughening effects can be obtained, and energy can be saved. The post-quenching tempering is performed to prevent the inheritance of original poor organization, and the post-tempering water cooling is performed to avoid temper brittleness. The above measures are prepared for obtaining a good final organization state.

[0016] Preferably, the post-forging heat treatment comprises the following steps of air cooling after forging, heating at 680-700 °C for 60-90 min for tempering, and water cooling after tempering.

[0017] Preferably, the rough machining comprises the following steps of rough machining the sliding sleeve blank after die forging and post-forging heat treatment, and reserving a machining allowance of 1-3 mm.

[0018] Preferably, in the heat treatment process, the protective atmosphere furnace heating (to prevent decarburization), quenching heating temperature is controlled at 850-880 DEG C, holding time 60-90 min, then quenching, quenching cooling medium is PAG quenching liquid, control quenching liquid temperature is 20-40 DEG C, ensure that the quenching after basically get all the martensite structure, tempering temperature control at 550-590 DEG C, tempering time 90-120 min, to obtain fine and uniform tempering sorbite, grain size 9-10 level, after tempering water cooling to avoid possible temper embrittlement.

[0019] Thread processing procedure, according to the standard and user requirements, the sliding sleeve is finished machining, API standard thread or special thread is machined at the same time, and the thread is subjected to magnetic powder detection.

[0020] In order to ensure the infinite level completion fracturing to the high strength and high toughness of the sliding sleeve, the chemical composition and manufacturing process must be reasonably designed.

[0021] In the aspect of composition design, the present application adopts medium C, adds alloy elements Cr, Ni, Mo, V micro-alloying, and adds trace Ce element, controls harmful elements P, S, O, H, N in the steel, full deoxidization of Al-Si, and Ca treatment is carried out on the molten steel.

[0022] The role and content range of each main element are as follows:

[0023] C: is the main strengthening element in steel. The use of medium carbon is conducive to improving the hardenability of the steel, thereby improving the strength of the steel; but too high carbon content is not conducive to improving the plasticity and toughness of the steel. Comprehensive consideration, it is appropriate to control in the range of 0.32% to 0.36%.

[0024] Si: is a common element in steel, and also an important deoxidizer. It is appropriate to control in the range of 0.17% to 0.37%.

[0025] Mn: is a common element in steel, which has the effect of improving the hardenability and strength of the steel, but the segregation tendency of Mn element is larger, which needs to be strictly controlled. It is appropriate to control in the range of 0.40% to 0.60%.

[0026] Cr: is dissolved in steel to improve the hardenability and tempering stability of the steel, thereby improving the strength of the steel, but too high content will increase the cost. Comprehensive consideration, it is appropriate to control in the range of 1.28% to 1.38%.

[0027] Ni: is dissolved in steel to improve the hardenability of the steel, thereby improving the strength, and its addition can also improve the toughness of the steel, especially the low temperature toughness, but too high content will increase the cost. Comprehensive consideration, it is appropriate to control in the range of 1.30% to 1.60%.

[0028] Mo: Solid solution in steel for improving the hardenability and tempering stability of the steel, thereby increasing the strength of the steel, while adding Mo can inhibit the segregation of Mn and P, improve uniformity, improve the temper brittleness of the steel, Mo / P≥20 is better, but too high content will increase the cost. Considering, it is appropriate to control in the range of 0.33% to 0.48%.

[0029] V: Added to the steel with C, N in the steel to form VC, VN, has the effect of hindering the growth of austenite grains, refining the grains, thereby improving the strength and toughness, but too high content will form too much carbonitride and increase the brittleness of the steel and will lead to cost increase. Considering, it is appropriate to control in the range of 0.03% to 0.08%.

[0030] Ce: Has the multiple effects of purifying molten steel, refining grains, modifying inclusions, and alloying. Considering, it is appropriate to control Ce in the range of 0.006% to 0.010%.

[0031] Al: Combined with oxygen or nitrogen to form fine and uniform distribution of oxides or nitrides can play a role in refining grains, while improving strength and toughness, is also an important deoxidizer and nitrogen fixation agent, but too much content will affect the hot working performance of the steel. Considering, it is appropriate to control in the range of 0.015% to 0.025%, control Al / N≥2.

[0032] Ca: Added to the steel can improve the properties and morphology of inclusions, thereby improving the plasticity and toughness of the steel, Ca / S≥3 is better. Considering, it is appropriate to control in the range of 0.015% to 0.025%.

[0033] P: Harmful element, mainly affects the plasticity and toughness of the steel. It is appropriate to control P≤0.015%.

[0034] S: Harmful element, mainly affects the plasticity and toughness of the steel. It is appropriate to control S≤0.005%.

[0035] O, H, N are harmful elements, mainly affecting the plasticity and toughness of the steel. Considering, it is appropriate to control O+H+N≤0.008%. Considering the great influence of N on the strain aging performance of the steel, it is appropriate to control N≤0.006%.

[0036] Compared with the 4140H medium-carbon Mn-Cr-Mo low-alloy steel and the 42CrMo medium-carbon low-alloy steel commonly used in the sliding sleeve, the C content is appropriately reduced (which is beneficial to improving the toughness), the Mn content is controlled (which controls the segregation), the Cr and Mo contents are increased (which improves the hardenability, the strength and the toughness), the Ni element is added (which improves the hardenability, the strength and the toughness, especially the low-temperature toughness), the V element is added (which refines the grain, improves the strength and the toughness) and the Ce element is added (which purifies the molten steel, refines the grain, modifies the inclusions, alloys, and improves the strength and the toughness), the inclusions are controlled by Ca treatment (which improves the toughness), and the harmful elements such as P, S, O, H and N in the steel are controlled (which improves the toughness), and the strength and the toughness level of the sliding sleeve is comprehensively improved through the individual action of each element and the synergistic effect thereof.

[0037] Compared with the prior art, the present application has the following advantages:

[0038] Reasonable matching of high strength and high toughness: through the optimized chemical composition design, the individual action of each alloying element and the synergistic effect thereof, and the unique preparation process including the improvement of the purity, the control of the inclusion properties and the morphology, the die forging and the segregation control, and the reasonable heat treatment for regulating the microstructure, the fracturing sliding sleeve has high strength and high toughness, the steel grade is 130 ksi-150 ksi, the minimum room temperature yield strength is 1012 MPa-1143 MPa, the tensile strength is 1112 MPa-1229 MPa, the elongation is 21%-25%, and the transverse Charpy V-notch impact toughness at-20 ℃ is 93 J-118 J. When subjected to complex load, the fracturing sliding sleeve has good deformation and fracture resistance, long service life and high safety and reliability, effectively adapts to the complex working conditions in the unconventional oil and gas exploitation, and improves the efficiency and the economic benefits of the unconventional oil and gas development. DETAILED DESCRIPTION

[0039] In order to make the purpose, the technical scheme and the advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the embodiments.

[0040] Unless defined, the technical terms used in the following embodiments have the same meanings as generally understood by those skilled in the art to which the present application belongs. The experimental methods are all conventional methods unless otherwise specified.

[0041] EMBODIMENTS

[0042] The chemical composition of the fracturing sliding sleeve with the minimum yield strength of 130 ksi, 140 ksi and 150 ksi respectively provided by the embodiments of the present application is shown in Table 1, wherein N≤0.006%, N+H+O≤0.008%, the balance is Fe and inevitable impurities.

[0043] Table 1 Chemical composition of the high-strength and high-toughness fracturing sliding sleeve (mass percent, %)

[0044]

[0045] The present application also provides a method for preparing high-strength and high-toughness fracturing sliding sleeves with minimum yield strength of 130 ksi, 140 ksi or 150 ksi, comprising the following steps:

[0046] ① Steelmaking: ingredient preparation, oxygen blowing converter steelmaking, feeding Si-Ca wire, obtaining the chemical composition in Table 1 through external refining and vacuum degassing.

[0047] ② Continuous casting: casting the molten steel into a bar-shaped continuous casting billet, and using electromagnetic stirring and light pressing down technology during continuous casting to control the center segregation of the continuous casting bar billet.

[0048] ③ Hot continuous rolling: heating the continuous casting billet in a ring-shaped heating furnace, the heating furnace temperature is 1190℃, the heating time is 120min, hot continuous rolling into a bar at 900℃-1190℃, then air cooling, and cutting to a suitable length.

[0049] ④ Die forging: heating the hot continuous rolling bar to 1170℃, holding for 90min, stamping into a thick-walled pipe at 1000℃-1150℃, air cooling; fine forging at 880℃-930℃, the final forging temperature is 880℃, the forging ratio is controlled to be greater than or equal to 5, air cooling after forging, 700℃ tempering for 90min, and water cooling after tempering.

[0050] ⑤ Rough machining and final heat treatment: rough machining the sliding sleeve blank after die forging and heat treatment after forging, leaving a machining allowance of 1.5mm, and then performing final heat treatment. The heat treatment process is heating in a protective atmosphere furnace (75% N2+25%H2 nitrogen-hydrogen mixed reducing atmosphere by volume fraction to prevent oxidation and decarburization), quenching + high-temperature tempering. The quenching heating temperature is 860℃, the holding time is 70min, then quenching, the quenching cooling medium is PAG quenching liquid, the quenching liquid temperature is controlled to be 20℃-40℃, and it is ensured that the quenching is basically obtained all martensite structure; the tempering temperature is controlled to be 550℃-590℃ (adjusted according to different steel grades), the tempering time is 120min, the structure is tempered sorbite, the grain size is 9-10 grade, and water cooling after tempering. The key preparation process parameters of fracturing sliding sleeves of different steel grades are shown in Table 2.

[0051] ⑥ Finishing and threading: finishing the sliding sleeve according to the standard and user requirements, simultaneously machining API standard threads or special threads, and performing magnetic powder detection on the threads.

[0052] Performance characteristics: the high-strength and high-toughness fracturing sliding sleeve material of the application has excellent strength and toughness and other comprehensive performance (see Table 2) after proper preparation process (steel grade is 130ksi~150ksi, room temperature yield strength is 1012MPa~1143MPa, tensile strength is 1112MPa~1229MPa, elongation is 21%~25%, transverse Charpy V-notch impact toughness at-20℃ is 93J~118J. It can meet the demand of unconventional oil and gas development for high-strength and high-toughness fracturing sliding sleeve.

[0053] Among them, the yield strength of the 130ksi steel grade fracturing sliding sleeve reaches 1012MPa~1018MPa, the tensile strength is 1112MPa~1119MPa, the elongation is 25%, the transverse Charpy V-notch impact toughness at-20℃ is 113J~118J.

[0054] The yield strength of the 140ksi steel grade fracturing sliding sleeve reaches 1073MPa~1079MPa, the tensile strength is 1166MPa~1173MPa, the elongation is 23%, the transverse Charpy V-notch impact toughness at-20℃ is 104J~108J.

[0055] The yield strength of the 150ksi steel grade fracturing sliding sleeve reaches 1137MPa~1143MPa, the tensile strength is 1223MPa~1229MPa, the elongation is 21%, the transverse Charpy V-notch impact toughness at-20℃ is 93J~96J.

[0056] The same number in Table 1 and Table 2 corresponds to the same embodiment.

[0057] Table 2 Key preparation process and performance of high-strength and high-toughness fracturing sliding sleeve of the embodiment

[0058]

[0059] The above only describes the preferred embodiments of the application and does not limit the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A high strength and high toughness fracturing sliding sleeve for unconventional oil and gas development, characterized in that: The chemical composition in percentage by mass is as follows: C: 0.32-0.36%, Si: 0.17-0.37%, Mn: 0.40-0.60%, P≤0.015%, S≤0.005%, Cr: 1.28-1.38%, Ni: 1.30-1.60%, Mo: 0.33-0.48%, V: 0.03-0.08%, Ce: 0.006-0.010%, Al: 0.015-0.025%, Ca: 0.015-0.025%, N≤0.006%, O+H+N≤0.008%, the balance being Fe and other inevitable impurities. The preparation method comprises the steps of steelmaking, continuous casting, hot continuous rolling, die forging, post-forging heat treatment, rough machining, heat treatment and thread machining processes. The hot continuous rolling comprises the following steps: heating the continuous casting blank in a ring heating furnace, the heating furnace temperature is 1180-1230 DEG C, the heating time is 90-120 min, hot rolling the blank into a rod at 900-1200 DEG C, and then air cooling; the post-forging heat treatment comprises the following steps: air cooling after forging, tempering at 680-700 DEG C for 60-90 min, and then water cooling after tempering; in the heat treatment process, the blank is heated in a protective atmosphere furnace, the quenching heating temperature is controlled at 850-880 DEG C, the holding time is 60-90 min, then quenching, the quenching cooling medium is PAG quenching liquid, the quenching liquid temperature is controlled at 20-40 DEG C, the tempering temperature is controlled at 550-590 DEG C, the tempering time is 90-120 min, and then water cooling after tempering.

2. The high strength and high toughness fracturing sliding sleeve for unconventional oil and gas development according to claim 1, characterized in that: The chemical composition in percentage by mass is as follows: C: 0.32-0.33%, Si: 0.17-0.30%, Mn: 0.40-0.47%, P≤0.015%, S≤0.005%, Cr: 1.28-1.31%, Ni: 1.30-1.41%, Mo: 0.33-0.38%, V: 0.04-0.05%, Ce: 0.006-0.007%, Al: 0.015-0.018%, Ca: 0.015-0.018%, N≤0.006%, O+H+N≤0.008%, the balance being Fe and other inevitable impurities.

3. The high strength and high toughness fracturing sliding sleeve for unconventional oil and gas development according to claim 1, characterized in that: The chemical composition in percentage by mass is as follows: C: 0.32-0.33%, Si: 0.17-0.30%, Mn: 0.40-0.47%, P≤0.015%, S≤0.005%, Cr: 1.28-1.31%, Ni: 1.30-1.41%, Mo: 0.33-0.38%, V: 0.04-0.05%, Ce: 0.006-0.007%, Al: 0.015-0.018%, Ca: 0.015-0.018%, N≤0.006%, O+H+N≤0.008%, the balance being Fe and other inevitable impurities. The chemical composition in percentage by mass is as follows: C: 0.32-0.33%, Si: 0.17-0.30%, Mn: 0.40-0.47%, P≤0.015%, S≤0.005%, Cr: 1.28-1.31%, Ni: 1.30-1.41%, Mo: 0.33-0.38%, V: 0.04-0.05%, Ce: 0.006-0.007%, Al: 0.015-0.018%, Ca: 0.015-0.018%, N≤0.006%, O+H+N≤0.008%, the balance being Fe and other inevitable impurities.

4. The high strength and high toughness fracturing sliding sleeve for unconventional oil and gas development according to claim 1, characterized in that: The chemical composition in terms of mass percentage is as follows: C: 0.35%-0.36%, Si: 0.29%-0.37%, Mn: 0.55%-0.60%, P≤0.015%, S≤0.005%, Cr: 1.35%-1.38%, Ni: 1.52%-1.60%, Mo: 0.43%-0.48%, V: 0.07%-0.08%, Ce: 0.009%-0.010%, Al: 0.022%-0.025%, Ca: 0.021%-0.025%, N≤0.006%, O+H+N≤0.008%, the balance being Fe and other inevitable impurities.

5. The high strength and high toughness fracturing sliding sleeve for unconventional oil and gas development according to claim 1, characterized in that: The die forging comprises the following processes: heating hot-rolled bar to 1150-1180 DEG C, holding for 60-90 min, stamping into thick-walled pipe fittings at 1000-1150 DEG C, and air cooling; fine forging at 880-930 DEG C, with the forging ratio controlled to be greater than or equal to 5.

6. The high strength and high toughness fracturing sliding sleeve for unconventional oil and gas development according to claim 1, characterized in that: The rough machining comprises the following processes: rough machining of the die forging and the pre-heat treated slide sleeve blank after forging, with a machining allowance of 1-3 mm reserved.

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