Ultrahigh temperature cement slurry fluid loss additive, and preparation method and application thereof

Abstract

The application provides an ultra-high temperature well cementing cement slurry fluid loss additive and a preparation method and application thereof. The preparation method comprises the following steps: adding 2-20 parts by weight of calcium silicate hydrate nanocrystal nucleus into 300-500 parts by weight of deionized water and dispersing the same sufficiently; sequentially adding 30-80 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-40 parts by weight of an unsaturated amide, 2-20 parts by weight of a cyclic olefin monomer and 2-20 parts by weight of an unsaturated carboxylic acid into the obtained dispersion and dissolving the same completely; slowly adding a pH regulator into the obtained mixture to adjust the pH value of the system to 6-7, and then adding 0.05-1 parts by weight of a chelating agent and 0.02-0.5 parts by weight of a chain transfer agent, and slowly heating the system to 50-70 DEG C under stirring; slowly heating the system to 70-90 DEG C after heating, keeping the temperature for 0.5-3 hours after the reaction, and then obtaining the target product.

Description

TECHNICAL FIELD

[0001] The application relates to an ultra-high-temperature cementing slurry fluid loss reducer and a preparation method and application thereof, and belongs to the technical field of cementing additives for oil and gas wells. BACKGROUND

[0002] Cementing is a key link in well construction, and cementing safety and quality are directly related to the service life of oil and gas wells. With the gradual change of domestic oil and gas resource exploration and development to deep and ultra-deep layers, ultra-high-temperature cementing slurry and key additives thereof have become the key to ensuring the safety and effective operation of cementing operations in complex deep and ultra-deep wells. When the cementing slurry flows through the permeable formation in the cementing operation, the liquid phase of the cementing slurry seeps into the formation, and if the water loss is serious, the slurry body will thicken, the pump pressure will increase, and the thickening time will be shortened, so that the cementing slurry is difficult to pump and even causes cementing accidents; in addition, the liquid phase of the cementing slurry entering the reservoir will cause water sensitivity, pollute the reservoir to different degrees, and affect the oil and gas production, and even completely block the fluid channels of the oil and gas layer. Therefore, a fluid loss reducer is usually added to the system to control the water loss of the cementing slurry, and the addition of the fluid loss reducer plays a very important role in ensuring the comprehensive performance of the system, ensuring the safety of the operation and improving the cementing quality.

[0003] At present, there are many types of fluid loss reducers in China, mainly AMPS polymer fluid loss reducers, which have become the focus of domestic and foreign scholars because of their excellent molecular structure design, excellent temperature resistance and salt resistance, weak sensitivity and strong fluid loss reduction capacity. However, the AMPS copolymer fluid loss reducer still has some problems: ① the molecular structure contains a large amount of strong adsorption groups such as sulfonic acid and carboxylic acid, and has strong low-temperature retarding property, which affects the strength development of the cement stone; ② under the condition of ultra-high temperature and high alkali, the molecular structure of the polymer is easy to change or the molecular chain is easy to break, the high-temperature dispersibility is enhanced, the fluid loss reduction capacity is weakened, and the comprehensive performance of the cementing slurry is poor; ③ the amide group in the polymer is easy to hydrolyze at high temperature, the thickening time of the cementing slurry is "hanging upside down", and the risk of cementing operation is increased; ④ the long cementing slurry in the cementing section is circulated to the top of the slurry column, and the polymer is strongly adsorbed on the surface of the cement particles, so that the strength development of the cement stone at the top of the slurry column is slow or super-retarded, fluid channeling or annular pressure is easy to occur, and even cementing accidents may occur.

[0004] Under the condition of ensuring the safety of cementing operation, anti-gas channeling agent or early strength agent is often added to the cement slurry system to improve the strength development rate of cement stone and avoid gas channeling when the cementing slurry is gelled in complex high temperature and high pressure gas wells. Therefore, the rapid development of the strength of the cement slurry after it is placed is an ideal state. In view of this, domestic and foreign researchers have modified AMPS copolymer fluid loss additive to improve its temperature resistance and salt tolerance, cement stone mechanical strength and cement slurry anti-gas channeling performance. For example, Chinese patent CN109503782A discloses an inorganic-organic polymer oil well cement fluid loss additive which is prepared by free radical aqueous solution polymerization method from itaconic acid, acrylamide monomer, AMPS, silane coupling agent and inorganic non-metallic materials (such as one or more of silicon carbide, silicon nitride, silicon dioxide and aluminum oxide). The inorganic non-metallic particles and the micro-crosslinked structure of the modified polymer are introduced into the existing polymer, which significantly improves the temperature resistance of the polymer. The results show that the fluid loss of the cement slurry containing 0.8% to 1.5% of the modified fluid loss additive can be controlled within 60 mL at 80 to 230℃. However, this technology uses micron-sized inorganic non-metallic particles (1 to 30 μm) and does not explain the influence of the modified fluid loss additive on the development of the mechanical strength of the cement stone. Zhang Jian et al. (Zhang Jian, Peng Zhigang, Zou Changjun, et al. Synthesis and characterization of polymer-based nano-SiO2 composite microspheres for cementing fluid loss additive [J]. Journal of the Chinese Ceramic Society, 2017, 45(11): 1649-1657.) prepared a composite microspherical fluid loss additive with core-shell structure by grafting styrene (St), butyl acrylate (BA) and methyl methacrylate (MMA) onto the surface of nano-SiO2. The temperature resistance and salt tolerance of the composite microspherical fluid loss additive are significantly improved, and it has no adverse effect on the comprehensive performance of the cement slurry. However, the ester bond on the surface of the composite microspherical fluid loss additive is easily hydrolyzed into carboxyl group under high temperature and strong alkali conditions, which is strongly adsorbed on the surface of the cement particles, thereby affecting the development of the strength of the cement stone at the top of the cement slurry column under large temperature difference.

[0005] In the existing technology represented by the above patents and literatures, although the temperature resistance and salt tolerance of the cementing fluid loss additive are significantly improved, there are still some problems in cementing complex oil and gas wells, especially in the process of cementing high temperature and high pressure complex gas wells. Therefore, it is of great significance to develop high temperature resistant and salt tolerant anti-gas channeling type high performance fluid loss additive to reduce the risk of annular gas channeling in complex gas wells or active oil and gas formations and ensure the quality of cementing. SUMMARY

[0006] In order to solve the above-mentioned shortcomings and deficiencies, one object of the present application is to provide a preparation method of ultra-high temperature cementing slurry fluid loss additive.

[0007] Another object of the present application is also to provide an ultra-high temperature cementing slurry fluid loss additive prepared by the above-mentioned preparation method.

[0008] Yet another object of the present application is to provide an ultra-high temperature cementing slurry containing the above-mentioned ultra-high temperature cementing slurry fluid loss additive.

[0009] Still another object of the present application is to provide the application of the above-mentioned ultra-high temperature cementing slurry fluid loss additive or the above-mentioned ultra-high temperature cementing slurry in cementing under complex working conditions. The ultra-high temperature cementing slurry fluid loss additive provided by the present application can solve the problems of poor temperature resistance, poor salt resistance and great influence on the strength development of cement stone of conventional AMPS polymer fluid loss additives, and has a good application prospect in cementing operations under complex working conditions such as deep and ultra-deep wells, complex natural gas wells and unconventional oil and gas wells.

[0010] To achieve the above objects, in one aspect, the present application provides a preparation method of an ultra-high temperature cementing slurry fluid loss additive, wherein the preparation method comprises:

[0011] (1) adding 2-20 parts by weight of calcium silicate hydrate nanocrystal cores with a certain particle size range into 300-500 parts by weight of deionized water and fully dispersing them;

[0012] (2) adding 30-80 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-40 parts by weight of unsaturated amide, 2-20 parts by weight of cyclic olefin monomer and 2-20 parts by weight of unsaturated carboxylic acid into the obtained dispersion liquid in sequence and completely dissolving them;

[0013] (3) slowly adding a pH adjusting agent to the mixed liquid obtained in step (2) to adjust the pH value of the system to 6-7, then adding 0.05-1 parts by weight of a chelating agent and 0.02-0.5 parts by weight of a chain transfer agent, and slowly heating to 50-70°C under stirring conditions;

[0014] (4) adding an initiator solution drop by drop to the system after heating in step (3), slowly heating to 70-90°C and maintaining this temperature for 0.5-3 h, to obtain the ultra-high temperature cementing slurry fluid loss additive.

[0015] As a specific embodiment of the above-mentioned preparation method of the present application, the average particle size of the calcium silicate hydrate nanocrystal cores is 50-1000 nm.

[0016] As a specific embodiment of the above-mentioned preparation method of the present application, the fully dispersing is achieved by ultrasonic dispersion treatment at 100 Hz±20 Hz for 20-60 min.

[0017] As a specific embodiment of the above-mentioned preparation method of the present application, the unsaturated amide includes but is not limited to one or more of N,N-dimethyl acrylamide, acrylamide and acryloyl morpholine, etc.

[0018] As a specific embodiment of the above-mentioned preparation method of the present application, the cyclic olefin monomer includes, but is not limited to, one or more of N-vinylpyrrolidone, N-vinylcaprolactam, dimethyl-dipropenyl ammonium chloride, and sodium styrene sulfonate.

[0019] As a specific embodiment of the above-mentioned preparation method of the present application, the unsaturated carboxylic acid includes, but is not limited to, one or more of acrylic acid, itaconic acid, maleic anhydride, maleic acid, fumaric acid, and propylene tricarboxylic acid.

[0020] As a specific embodiment of the above-mentioned preparation method of the present application, the pH regulator includes, but is not limited to, sodium hydroxide.

[0021] As a specific embodiment of the above-mentioned preparation method of the present application, the stirring speed is 200 rpm ± 50 rpm.

[0022] As a specific embodiment of the above-mentioned preparation method of the present application, the chelating agent includes, but is not limited to, one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, iminodisuccinic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, and trisodium salt of hydroxyethylenediaminetetraacetate.

[0023] As a specific embodiment of the above-mentioned preparation method of the present application, the chain transfer agent includes, but is not limited to, one or more of mercaptopropionic acid, mercaptoethanol, isopropyl alcohol, dodecanethiol, hydroquinone, and dihydroquinoline.

[0024] The preparation method provided by the present application does not have specific requirements for the order of adding the chain transfer agent and the chelating agent, and the order of adding the two can be adjusted according to the actual operation requirements on site, as long as the purpose of preparing the ultra-high temperature well cementing slurry fluid loss additive can be achieved.

[0025] As a specific embodiment of the above-mentioned preparation method of the present application, the mass concentration of the initiator solution is 3% to 30%.

[0026] As a specific embodiment of the above-mentioned preparation method of the present application, the amount of the initiator is 0.2% to 1.5%, based on 100% of the total weight of 2-acrylamido-2-methylpropanesulfonic acid, unsaturated amide, cyclic olefin monomer, and unsaturated carboxylic acid.

[0027] As a specific embodiment of the above-mentioned preparation method of the present application, the initiator includes, but is not limited to, one or more of potassium persulfate, ammonium persulfate, hydrogen peroxide, azobisimidozolinium hydrochloride, and azobisimidoformamidine hydrochloride.

[0028] As a specific embodiment of the above-mentioned preparation method of the present application, in steps (3) and (4), the heating rate of the slow heating is 0.5-2℃ / min.

[0029] As a specific embodiment of the above-mentioned preparation method of the present application, the preparation method further comprises: after the reaction is completed, naturally cooling the reaction system to room temperature to obtain the ultra-high temperature cementing slurry fluid loss additive.

[0030] In the above-mentioned preparation method of the present application, the polymer obtained by polymerization of 2-acrylamido-2-methylpropanesulfonic acid, unsaturated amide, cyclic olefin monomer and unsaturated carboxylic acid monomers is grafted on the surface of the calcium silicate hydrate nanocrystal core by hydrogen bond or ionic bond, etc. In addition, 2-acrylamido-2-methylpropanesulfonic acid, unsaturated amide, cyclic olefin monomer and unsaturated carboxylic acid monomers are also preferentially grafted on the surface of the calcium silicate hydrate nanocrystal core during the preparation process, and then the monomers grafted on the surface of the crystal core further copolymerize with other monomers to form a polymer. Regardless of the reaction process, since the calcium silicate hydrate nanocrystal core is an amorphous structure with a large specific surface area, not a regular round particle, and the polymer molecular chain is not completely grafted on the surface of the crystal core, therefore, after the reaction is completed, there are still a large number of exposed active sites on the surface of the crystal core in the obtained fluid loss additive, which can induce the cement hydration product to normally generate, grow and develop on the surface thereof.

[0031] On the other hand, the present application also provides the ultra-high temperature cementing slurry fluid loss additive prepared by the above-mentioned preparation method of the ultra-high temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

[0032] Calcium silicate hydrate (C-S-H) is the main product of Portland cement hydration, which contributes greatly to the development of mechanical strength of cement stone. The "crystal nucleus template" effect of nanocrystalline nucleus can reduce the potential barrier of C-S-H gel generation, induce rapid dissolution of C3S and generation of calcium hydroxide crystals, and promote the in-situ growth of hydration products on the crystal nucleus, thereby accelerating the hydration process of cement and improving the mechanical strength of cement stone. Meanwhile, the polymer is grafted onto the surface of C-S-H nanocrystalline nucleus through ionic charge and calcium ion chelation, which can significantly improve the temperature resistance and fluid loss control ability of the polymer fluid loss additive. In addition, the introduction of amide substances with strong hydration groups, stable five-membered ring rigid monomers and strong adsorption unsaturated carboxylic acid monomers into the structure of the polymer can improve the temperature resistance, high-temperature adsorption and environmental adaptability of the polymer. In summary, the innovative design of the molecular structure of the polymer fluid loss additive modified by the nanocrystalline nucleus of calcium silicate hydrate can not only significantly reduce the influence of AMPS polymer on the cement hydration process and promote the development of strength, but also improve the ability of the fluid loss additive to control fluid loss under high temperature and ultra-high temperature conditions, thereby greatly improving the temperature range of the obtained fluid loss additive.

[0033] In another aspect, the application further provides an ultra-high temperature cementing slurry containing the ultra-high temperature cementing slurry fluid loss additive described above.

[0034] In still another aspect, the application further provides the application of the ultra-high temperature cementing slurry fluid loss additive described above or the ultra-high temperature cementing slurry described above in cementing under complex working conditions.

[0035] As a specific embodiment of the application described above, the complex working conditions include deep wells, ultra-deep wells, complex natural gas wells and unconventional oil and gas wells.

[0036] Compared with the prior art, the application has the following beneficial effects:

[0037] 1) The surface grafting modification technology is used in the application to combine the nanocrystalline nucleus of calcium silicate hydrate with the polymer organically, so that a nanocrystalline nucleus modified polymer fluid loss additive with good comprehensive performance is obtained, and the temperature resistance and fluid loss control ability of the polymer fluid loss additive are significantly improved. At the same time, the use of the fluid loss additive is also beneficial to the development of the low-temperature strength of cement stone.

[0038] 2) The performance of the fluid loss additive provided by the application is stable, the temperature range is wide (20-240℃), the anti-saturation salt water ability (i.e. the salt resistance) is strong, the fluid loss performance is excellent, the anti-channeling effect is obvious, the adaptability is strong, the early strength development of cement stone is beneficial, the transition time of the static gel strength of cement slurry from 48Pa to 240Pa can be significantly shortened, and the late mechanical property development of cement stone is not adversely affected. The comprehensive performance of the fluid loss additive is better than that of conventional AMPS polymer fluid loss additives.

[0039] 3) The preparation method of the fluid loss additive provided by the application is simple, green, safe and environmentally friendly, the conditions are mild, the raw material cost and processing cost are low, and large-scale production and popularization can be carried out.

[0040] 4) The fluid loss additive provided by the application can be applied to various cement slurry systems for well cementing, can meet the technical requirements of well cementing under complex working conditions such as deep wells, ultra-deep wells, complex natural gas wells and unconventional oil and gas wells, and has a wide application market. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0042] Figure 1 The G-class cement slurry with the fluid loss additive provided by Example 1 mixed in Test Example 1 (the mixing amount is 4% bwoc) is subjected to a thickening curve at 240℃x100MPa.

[0043] Figure 2 The G-class cement slurry with the ultra-high temperature well cementing fluid loss additive provided by Example 1 mixed in Test Example 2 (the mixing amount is 3% bwoc) and the G-class cement slurry with the well cementing fluid loss additive provided by Comparative Example 1 mixed (the mixing amount is 3% bwoc) are subjected to a cement stone strength development curve comparison chart under the condition of 60℃x21MPa.

[0044] Figure 3 The G-class cement slurry with the ultra-high temperature well cementing fluid loss additive provided by Example 1 mixed in Test Example 3 (the mixing amount is 3% bwoc) and the G-class cement slurry with the well cementing fluid loss additive provided by Comparative Example 1 mixed (the mixing amount is 3% bwoc) are subjected to a cement slurry static gel strength development curve comparison chart under the condition of 60℃x21MPa. DETAILED DESCRIPTION

[0045] The ranges disclosed herein are presented in terms of "about" a value and "about" a range. When such about values and about ranges are used, it will be understood that the endpoints of the ranges are not to be understood as limited to the precise values. It will be further understood that the endpoints of the ranges can be combined with one another to form ranges further within the scope of the ranges. Additionally, it will be understood that the ranges can be combined with other ranges to form further ranges within the scope of the ranges. For example, a range of "about 1 to about 5" can be understood to include a range of "about 1 to about 3", a range of "about 1 to about 4", a range of "about 1 to about 2", a range of "about 2 to about 5", a range of "about 2 to about 4", a range of "about 3 to about 5", a range of "about 3 to about 4", and a range of "about 4 to about 5".

[0046] In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand for the full set of real combinations of a to b, wherein a and b are both real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand for these numerical combinations.

[0047] In the present application, unless otherwise stated, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form new technical solutions.

[0048] In the present application, unless otherwise stated, all the technical features and preferred features mentioned herein can be combined with each other to form new technical solutions.

[0049] In the present application, unless otherwise stated, "comprising" mentioned herein represents open-ended, and can also be closed. For example, the "comprising" can represent that other materials and / or elements not listed can also be included, or only the listed materials and / or elements can be included.

[0050] In addition, unless otherwise stated, the substances used in the embodiments of the present application are all conventional substances, which can be obtained by commercial purchase or prepared in the laboratory by existing conventional methods.

[0051] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present application, the technical solutions of the present application will be described in detail below in conjunction with the following specific embodiments, but it should not be understood as limiting the scope of the present application.

[0052] Example 1

[0053] The present embodiment provides a super-high temperature well cementing cement slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0054] Take 10 g of calcium silicate hydrate nanocrystal core with an average particle size of 95 nm, add it to 300 g of deionized water, and ultrasonic dispersion treatment at 100 Hz for 30 min;

[0055] Add 75 g of 2-acrylamido-2-methylpropanesulfonic acid, 15 g of N,N-dimethylacrylamide, 5 g of N-vinylpyrrolidone, and 5 g of itaconic acid to the obtained solution in sequence and completely dissolve;

[0056] Slowly add 20 g of sodium hydroxide to adjust the pH of the system to 7, then add 0.1 g of disodium ethylenediaminetetraacetate and 0.05 g of mercaptopropionic acid, and slowly warm up to 60°C under the condition of 200 rpm stirring;

[0057] Add 6 g of 10% ammonium persulfate solution to the system drop by drop, slowly warm up to 70°C, and after 2 h of reaction, naturally cool down to room temperature to obtain a milky white viscous liquid, which is an ultra-high temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

[0058] Example 2

[0059] The present embodiment provides an ultra-high temperature cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0060] Take 20 g of calcium silicate hydrate nanocrystal core with an average particle size of 95 nm, add it to 300 g of deionized water, and ultrasonic dispersion treatment at 100 Hz for 30 min;

[0061] Add 75 g of 2-acrylamido-2-methylpropanesulfonic acid, 15 g of N,N-dimethylacrylamide, 5 g of N-vinylpyrrolidone, and 5 g of itaconic acid to the obtained solution in sequence and completely dissolve;

[0062] Slowly add 20 g of sodium hydroxide to adjust the pH of the system to 7, then add 0.1 g of disodium ethylenediaminetetraacetate and 0.05 g of mercaptopropionic acid, and slowly warm up to 60°C under the condition of 200 rpm stirring;

[0063] Add 6 g of 10% ammonium persulfate solution to the system drop by drop, slowly warm up to 70°C, and after 2 h of reaction, naturally cool down to room temperature to obtain a milky white viscous liquid, which is an ultra-high temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

[0064] Example 3

[0065] The present embodiment provides an ultra-high temperature cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0066] Take 10 g of calcium silicate hydrate nanocrystalline core with an average particle size of 100 nm, add it to 400 g of deionized water, and ultrasonic dispersion treatment at 120 Hz for 20 min;

[0067] Add 60 g of 2-acrylamido-2-methylpropanesulfonic acid, 20 g of acryloyl morpholine, 10 g of N-vinyl pyrrolidone, and 10 g of maleic anhydride to the obtained solution in sequence and completely dissolve;

[0068] Slowly add 18 g of sodium hydroxide to adjust the pH of the system to 6.5, then add 0.2 g of imidodisuccinic acid and 0.08 g of mercaptoethanol, and slowly warm up to 50°C under the condition of 200 rpm stirring;

[0069] Add 8 g of 10% potassium persulfate solution to the system drop by drop, slowly warm up to 80°C and keep the reaction for 2 h, then naturally cool down to room temperature to obtain a milky white viscous liquid, which is an ultra-high temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystalline core modified polymer fluid loss additive.

[0070] Example 4

[0071] This example provides an ultra-high temperature cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0072] Take 15 g of calcium silicate hydrate nanocrystalline core with an average particle size of 200 nm, add it to 340 g of deionized water, and ultrasonic dispersion treatment at 100 Hz for 60 min;

[0073] Add 67 g of 2-acrylamido-2-methylpropanesulfonic acid, 20 g of acryloyl morpholine, 10 g of acrylamide, 8 g of N-vinyl pyrrolidone, 3 g of acrylic acid, and 2 g of maleic anhydride to the obtained solution in sequence and completely dissolve;

[0074] Slowly add 22 g of sodium hydroxide to adjust the pH of the system to 7, then add 0.5 g of ethylenediaminetetraacetic acid and 0.1 g of hydroquinone, and slowly warm up to 70°C under the condition of 200 rpm stirring;

[0075] Add 5 g of 22% azobisdimethylamidinium hydrochloride solution to the system drop by drop, slowly warm up to 80°C and keep the reaction for 1.5 h, then naturally cool down to room temperature to obtain a milky white viscous liquid, which is an ultra-high temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystalline core modified polymer fluid loss additive.

[0076] Example 5

[0077] The embodiment provides a super-high-temperature cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0078] 5g of calcium silicate hydrate nanocrystal cores with an average particle size of 50nm are weighed, added into 250g of deionized water, and ultrasonically dispersed at 100Hz for 45min;

[0079] 70g of 2-acrylamido-2-methylpropanesulfonic acid, 10g of N,N-dimethylacrylamide, 15g of N-vinylpyrrolidone and 5g of itaconic acid are sequentially added into the obtained solution and completely dissolved;

[0080] 25g of sodium hydroxide is slowly added to adjust the pH of the system to 6, and then 0.3g of diethylenetriamine pentaacetic acid and 0.05g of mercaptopropionic acid are added, and the system is slowly heated to 60°C under the condition of 200rpm stirring;

[0081] 5g of ammonium persulfate solution with a mass concentration of 16% is added dropwise into the system, the system is slowly heated to 90°C and kept for 1h, and then naturally cooled to room temperature, to obtain a milky white viscous liquid, that is, the super-high-temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

[0082] Embodiment 6

[0083] The embodiment provides a super-high-temperature cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0084] 10g of calcium silicate hydrate nanocrystal cores with an average particle size of 500nm are weighed, added into 360g of deionized water, and ultrasonically dispersed at 100Hz for 30min;

[0085] 33.7g of 2-acrylamido-2-methylpropanesulfonic acid, 6g of acrylamide, 13g of N,N-dimethylacrylamide, 8g of dimethyl-dipropylammonium chloride and 6g of acrylic acid are sequentially added into the obtained solution and completely dissolved;

[0086] 15g of sodium hydroxide is slowly added to adjust the pH of the system to 7, and then 0.6g of hydroxyethyl ethylenediamine triacetic acid and 0.2g of dodecanethiol are added, and the system is slowly heated to 60°C under the condition of 200rpm stirring;

[0087] 8g of azobisimidozolin hydrochloride solution with a mass concentration of 5% is added dropwise into the system, the system is slowly heated to 80°C and kept for 2h, and then naturally cooled to room temperature, to obtain a milky white viscous liquid, that is, the super-high-temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

[0088] Embodiment 7

[0089] The present embodiment provides a super-high-temperature cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0090] 10 g of calcium silicate hydrate nanocrystal cores with an average particle size of 300 nm were weighed out, added to 300 g of deionized water, and subjected to ultrasonic dispersion treatment at 100 Hz for 30 min;

[0091] 75 g of 2-acrylamido-2-methylpropanesulfonic acid, 15 g of N,N-dimethylacrylamide, 5 g of sodium styrene sulfonate, and 5 g of itaconic acid were sequentially added to the obtained solution and completely dissolved;

[0092] 20 g of sodium hydroxide was slowly added to adjust the pH of the system to 7, and then 0.1 g of disodium ethylenediaminetetraacetate and 0.05 g of mercaptopropionic acid were added, and the system was slowly heated to 60°C under the condition of stirring at 200 rpm;

[0093] 6 g of ammonium persulfate solution with a mass concentration of 10% was added dropwise to the system, the system was slowly heated to 70°C and kept at this temperature for 2 h, and then naturally cooled to room temperature to obtain a milky white viscous liquid, i.e., a super-high-temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

[0094] Comparative Example 1

[0095] The present comparative example provides a cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0096] 75 g of 2-acrylamido-2-methylpropanesulfonic acid, 15 g of N,N-dimethylacrylamide, 5 g of N-vinylpyrrolidone, and 5 g of itaconic acid were weighed out and sequentially added to 300 g of deionized water and completely dissolved in the water;

[0097] 20 g of sodium hydroxide was slowly added to adjust the pH of the system to 7, and then 0.1 g of disodium ethylenediaminetetraacetate and 0.05 g of mercaptopropionic acid were added, and the system was slowly heated to 60°C under the condition of stirring at 200 rpm;

[0098] 6 g of ammonium persulfate solution with a mass concentration of 10% was added dropwise to the system, the system was slowly heated to 70°C and kept at this temperature for 2 h, and then naturally cooled to room temperature to obtain a colorless liquid fluid loss additive.

[0099] Comparative Example 2

[0100] The present comparative example provides a cementing slurry fluid loss additive, which is prepared by a preparation method comprising the following specific steps:

[0101] In a 500ml four-necked flask equipped with a thermometer, a condenser and a stirrer, 4.5g of itaconic acid (IA) and 55g of water were added, and the temperature was raised to 50℃ and stirred for 15min to completely dissolve;

[0102] Then 34.5g of acrylamide (AM) and 36.0g of AMPS were dissolved in 150g of water, and transferred to the four-necked flask, and the pH of the solution was adjusted to 6 with NaOH;

[0103] Then 3.75g of SiO2 micro powder (particle size of 20-30μm) and 0.19g of KH-550 were weighed and placed in the four-necked flask, and the temperature was maintained at 40℃ and stirred for 30min, and then the temperature was raised to 60℃;

[0104] Finally, 10g of aqueous solution containing 0.525g of ammonium persulfate and 0.525g of sodium bisulfite was added to the four-necked flask, and the reaction was carried out at constant temperature for 8h, and then naturally cooled to room temperature to obtain a white viscous liquid fluid loss agent (i.e. the reaction product before drying in Example 2 of Chinese patent CN109503782A).

[0105] Test Example 1

[0106] In this test example, the G-class cement slurry doped with the ultra-high temperature cement slurry fluid loss agent provided in Example 1 was subjected to thickening experiment test, wherein the G-class cement slurry doped with the fluid loss agent provided in Example 1 (doping amount was 4%bwoc) had a thickening curve at 240℃×100MPa as shown in Figure 1 .

[0107] As can be seen from Figure 1 , the thickening curve of the cement slurry doped with the fluid loss agent provided in Example 1 was normal at 240℃, 100MPa, and there was no abnormal gelation phenomenon such as "bulging" during the thickening process, and the consistency curve was smooth, which indicated that the fluid loss agent provided in Example 1 of the present application had good high temperature resistance and little effect on the thickening performance of the ultra-high temperature cement slurry. Therefore, it is shown that the hydrated calcium silicate nanocrystal core modified polymer fluid loss agent prepared by the nanocrystal core surface grafting polymer technology has excellent comprehensive performance.

[0108] Test Example 2

[0109] This test example examines the cement stone strength development of both Grade G cement slurry incorporating the ultra-high temperature cement slurry fluid loss reducer (3% BWOC) provided in Example 1 and Grade G cement slurry incorporating the cement slurry fluid loss reducer (3% BWOC) provided in Comparative Example 1. The comparison of cement stone strength development curves for both Grade G cement slurry incorporating the ultra-high temperature cement slurry fluid loss reducer (3% BWOC) provided in Example 1 and Grade G cement slurry incorporating the cement slurry fluid loss reducer (3% BWOC) provided in Comparative Example 1 under conditions of 60℃ × 21MPa is shown in the figure below. Figure 2 As shown.

[0110] Depend on Figure 2 It can be seen that, compared with the cement slurry containing the water loss reducing agent provided in Comparative Example 1, the strength development time of the cement slurry containing the water loss reducing agent provided in Example 1 is significantly shortened, and under the same curing age, the cement stone formed by the cement slurry containing the water loss reducing agent provided in Example 1 has higher strength.

[0111] Test Example 3

[0112] This test example examines the static gel strength development of Grade G cement slurry incorporating the ultra-high temperature cement slurry fluid loss reducer (3% BWOC) provided in Example 1 and Grade G cement slurry incorporating the cement slurry fluid loss reducer (3% BWOC) provided in Comparative Example 1. The static gel strength development curves of the Grade G cement slurry incorporating the ultra-high temperature cement slurry fluid loss reducer (3% BWOC) provided in Example 1 and the Grade G cement slurry incorporating the cement slurry fluid loss reducer (3% BWOC) provided in Comparative Example 1 under the conditions of 60℃ × 21MPa are compared as shown in the figure below. Figure 3 As shown.

[0113] Depend on Figure 3 It can be seen that the transition times for the static cementitious strength values ​​of Grade G cement slurry, which are mixed with the ultra-high temperature cement slurry fluid loss control agent (3% bwoc) provided in Example 1 and Grade G cement slurry mixed with the cement slurry fluid loss control agent (3% bwoc) provided in Comparative Example 1, from 48 Pa to 240 Pa are 39 min and 49.5 min, respectively. This indicates that the polymer fluid loss control agent modified with hydrated calcium silicate nanocrystal nuclei provided by the present invention is more conducive to the low-temperature strength development of cement stone and improves the anti-channeling ability of the system, and it can also reduce the influence of conventional AMPS-type polymer fluid loss control agents on the strength development of cement stone.

[0114] It should be noted that: cement slurry static gel strength transition time is an important parameter for evaluating the cement slurry anti-channeling performance. The shorter the static gel strength transition (48Pa to 240Pa) time is, the shorter the gas migration distance in the cement slurry matrix is, the smaller the gas channeling risk and damage are, indicating that the cement slurry anti-channeling ability is stronger. According to the research, the relationship between static gel transition time and anti-channeling ability is: static gel transition time ≤40min, anti-channeling ability is strong; static gel transition time is between 40min and 80min, anti-channeling ability is good; static gel transition time >80min, anti-channeling ability is poor; static gel transition time ≥110min, anti-channeling ability is very poor.

[0115] In summary, the comprehensive performance of the hydration calcium silicate nanocrystal core modified polymer fluid loss agent provided in embodiment 1 of the present application is obviously better than that of the cement slurry fluid loss agent provided in comparative example 1.

[0116] Test example 4

[0117] The comprehensive performance of the fluid loss agents provided in examples 1-7 and comparative examples 1-2 was respectively evaluated according to the relevant provisions in the oil and gas industry standard SY / T5504.2-2013 "Oil well cement additive evaluation method part 2: fluid loss agent" and the national standard GB / T19139-2012 "Oil well cement test method", and the obtained evaluation results are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] Note: The cement used in the test examples of the present application is all Jiahua G-grade oil well cement (high sulfur resistance). The "*" in Table 1 represents the mass concentration in water, the "#" represents the mass percentage in cement, and the "--" represents not measured. In Table 1, the cement slurry formula with a temperature lower than 95℃: 600g G-grade oil well cement + x% fluid loss agent + (44-x)% water; in Table 1, the cement slurry formula with a temperature higher than 95℃: 600g G-grade oil well cement + 30% quartz sand + 5% microsilica + x% fluid loss agent + 3% retarder DRH-2L + 0.5% stabilizer DRK-3S + 0.6% dispersant DRS-1S + (55-x)% water (density is 1.89g / cm 3 ), wherein x is 3, 4 or 5; the percentage content of quartz sand, microsilica, retarder DRH-2L, stabilizer DRK-3S and dispersant DRS-1S is also calculated based on the total weight of cement.

[0122] As shown in Table 1, with the increase of the test temperature, the API fluid loss of the cement slurry containing the fluid loss additive provided by the embodiments of the present application has a gradually increasing trend, but the increase range is small. When the dosage of the fluid loss additive provided by Example 1 is 3% bwoc, the API fluid loss of the cement slurry can be controlled within 50 mL at a test temperature of 150℃ or lower; when the test temperature is higher than 150℃, the API fluid loss of the cement slurry can also be controlled within 50 mL by appropriately increasing the dosage of the fluid loss additive; and the fluid loss performance of the fluid loss additives prepared by Examples 1-7 is basically the same at the same temperature.

[0123] As shown in Table 1, when the dosage of the fluid loss additive provided by the embodiments of the present application is 5% bwoc, the API fluid loss of the saturated brine cement slurry can be controlled within 50 mL, which is better than the fluid loss additive products provided by Comparative Examples 1-2.

[0124] As shown in Table 1, compared with the fluid loss additive products provided by Comparative Examples 1-2, the cement slurry containing the fluid loss additive provided by Examples 1-7 has better high-temperature stability, and the free liquid content is less than 0.5%, which greatly improves the problem that the conventional polymer fluid loss additive is seriously affected by the strong high-temperature dilution of the cement slurry. At the same curing condition, the 24h compressive strength of the cement stone formed by the cement slurry containing the fluid loss additive provided by Examples 1-7 is higher than that of the fluid loss additive products provided by Comparative Examples 1-2, and the transition time of the static gel strength of the cement slurry containing the fluid loss additive provided by Examples 1-7 is short, and the anti-gas channeling performance at low temperature is better, which shows that the presence of the calcium silicate hydrate nanocrystal core in the fluid loss additive provided by the embodiments of the present application is beneficial to improve the mechanical strength of the cement stone.

[0125] Therefore, the fluid loss additive provided by the embodiments of the present application has excellent temperature resistance, a wide application temperature range (20-240℃), and is resistant to saturation of salt, and is beneficial to the high-temperature stability and mechanical strength development of the cement slurry.

[0126] In summary, the calcium silicate hydrate nanocrystal core modified polymer fluid loss additive provided by the embodiments of the present application can achieve the following beneficial technical effects:

[0127] 1) The embodiments of the present application use surface grafting modification technology to combine the calcium silicate hydrate nanocrystal core with the polymer, and obtain a nanocrystal core modified polymer fluid loss additive with good comprehensive performance, which significantly improves the temperature resistance and fluid loss capacity of the polymer fluid loss additive; at the same time, the use of the fluid loss additive is also beneficial to the development of the low-temperature strength of the cement stone.

[0128] 2) The performance of the fluid loss additive provided by the embodiment of the present application is stable, the temperature range is wide (20-240 DEG C), the anti-saturation brine ability, that is, the salt resistance is strong, the fluid loss performance is excellent, the channeling prevention effect is obvious, the adaptability is strong, the early strength development of the cement stone is beneficial, the transition time of the static gel strength of the cement slurry from 48Pa to 240Pa can be obviously shortened, and the late mechanical property development of the cement stone has no adverse effect, the comprehensive performance is better than that of the conventional AMPS polymer fluid loss additive.

[0129] 3) The preparation method of the fluid loss additive provided by the embodiment of the present application is simple, green, safe and environmentally friendly, the conditions are mild, the raw material cost and the processing cost are low, and large-scale production and popularization can be carried out.

[0130] 4) The fluid loss additive provided by the embodiment of the present application can be applied to various cementing cement slurry systems, can meet the cementing technical requirements under the complex working conditions of deep wells, ultra-deep wells, complex natural gas wells, unconventional oil and gas wells and the like, and has a wide application market.

[0131] The above is only a specific embodiment of the present application, and cannot limit the scope of the present application, so the replacement of equivalent components or equivalent changes and modifications made in the scope of the present application should still belong to the scope of the present application. In addition, the technical features in the present application can be freely combined with each other, and the technical features can be freely combined with each other.

Claims

1. A method for preparing a ultra-high temperature cement slurry fluid loss additive, characterized in that, The preparation method comprises: (1) adding 2-20 parts by weight of calcium silicate hydrate nanocrystal cores with a certain particle size range into 300-500 parts by weight of deionized water and fully dispersing; wherein the calcium silicate hydrate nanocrystal core is an amorphous structure, and the average particle size is 50-1000 nm; (2) adding 30-80 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-40 parts by weight of an unsaturated amide, 2-20 parts by weight of a cyclic olefin monomer and 2-20 parts by weight of an unsaturated carboxylic acid into the obtained dispersion liquid in sequence and fully dissolving; wherein the cyclic olefin monomer comprises one or more of N-vinylpyrrolidone, N-vinylcaprolactam and sodium styrene sulfonate; (3) slowly adding a pH regulator to the mixed liquid obtained in step (2) to adjust the pH value of the system to 6-7, and then adding 0.05-1 parts by weight of a chelating agent and 0.02-0.5 parts by weight of a chain transfer agent, and slowly heating to 50-70°C under stirring; (4) adding an initiator solution drop by drop to the system after heating in step (3), slowly heating to 70-90°C and keeping the temperature for 0.5-3 h, and after the reaction is completed, the polymer obtained by polymerization of 2-acrylamido-2-methylpropanesulfonic acid, an unsaturated amide, a cyclic olefin monomer and an unsaturated carboxylic acid is grafted on the surface of the calcium silicate hydrate nanocrystal core through hydrogen bonding or ionic bonding to obtain the ultra-high temperature cementing slurry fluid loss additive, which is a calcium silicate hydrate nanocrystal core modified polymer fluid loss additive.

2. The production method according to claim 1, characterized by, The full dispersion is achieved by ultrasonic dispersion treatment at 100 Hz±20 Hz for 20-60 min.

3. The preparation method according to claim 1, characterized in that, The unsaturated amide comprises one or more of N,N-dimethyl acrylamide, acrylamide and acryloyl morpholine.

4. The method of claim 1, wherein, The unsaturated carboxylic acid comprises one or more of acrylic acid, itaconic acid, maleic anhydride, maleic acid, fumaric acid and propylene tricarboxylic acid.

5. The preparation method according to claim 1, characterized in that, The pH regulator comprises sodium hydroxide.

6. The method of claim 1, wherein, The stirring speed is 200 rpm±50 rpm.

7. The preparation method according to claim 1, characterized in that, The chelating agent comprises one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, iminodisuccinic acid, diethylenetriamine pentaacetic acid, hydroxyethyl ethylenediamine triacetic acid and hydroxyethyl diaminetetraacetic acid trisodium salt.

8. The method of claim 1, wherein, The chain transfer agent comprises one or more of mercaptopropionic acid, mercaptoethanol, isopropyl alcohol, dodecanethiol, hydroquinone and dihydroquinoline.

9. The method of claim 1, wherein, The mass concentration of the initiator solution is 3%-30%.

10. The production method according to claim 1 or 9, characterized by, The amount of the initiator is 0.2-1.5% based on the total weight of 2-acrylamido-2-methylpropanesulfonic acid, an unsaturated amide, a cyclic olefin monomer and an unsaturated carboxylic acid being 100%.

11. The production method according to claim 1 or 9, characterized by, The initiator comprises one or more of potassium persulfate, ammonium persulfate, hydrogen peroxide, azobis isobutylimidazoline hydrochloride and azobis isobutylamidine hydrochloride.

12. The method of claim 1, wherein, In steps (3) and (4), the heating rate of slow heating is 0.5-2°C / min.

13. The method of claim 1, wherein, The preparation method further comprises: after the reaction is completed, naturally cooling the reaction system to room temperature to obtain the ultra-high temperature cementing slurry fluid loss additive.

14. The method of claim 1-13, wherein the ultra-high temperature cementing fluid loss additive is a hydrated calcium silicate nanocrystal core modified polymer fluid loss additive.

15. An ultra-high temperature cementing fluid comprising the ultra-high temperature cementing fluid loss additive of claim 14.

16. The use of the ultra-high temperature cementing fluid loss additive of claim 14 or the ultra-high temperature cementing fluid of claim 15 in cementing under complex conditions.

17. Use according to claim 16, characterized in that, The complex conditions include deep or ultra-deep wells, complex natural gas wells, and unconventional oil and gas wells.

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