Micro-crosslinking structure interlocking type fluid loss additive, preparation method thereof and well cementing slurry system

Abstract

The application discloses a micro-crosslinking structure interlocking type fluid loss additive, a preparation method thereof and a cementing slurry system. The preparation method of the fluid loss additive comprises the following steps: mixing 2-acrylamido-2-methylpropanesulfonic acid, a carboxylic acid or derivative monomer containing a vinyl group and water, and adding a pH value regulator to adjust the pH value of the system; then adding a modified acrylamide monomer, a vinyl cyclic monomer and a crosslinking agent; then adding a molecular weight regulator, a chelating agent and an oxidizing agent to obtain a mixed system; and adding an aqueous solution of a reducing agent into the mixed system, and reacting for a period of time to obtain the fluid loss additive. The fluid loss additive has better temperature resistance, salt resistance and fluid loss reduction performance, can improve the sedimentation stability of the cementing slurry system, has no adverse effect on the comprehensive performance of the cementing slurry system, and is suitable for a wide temperature range.

Description

TECHNICAL FIELD

[0001] The application relates to a micro-crosslinking structure interlocking type fluid loss additive, a preparation method thereof and a cementing slurry system, and belongs to the technical field of oil and gas well cementing. BACKGROUND

[0002] Deep and ultra-deep oil and gas resources have great potential and have become an important field for increasing oil and gas reserves and production, and gradually change to ultra-deep layers. At present, the ultra-deep and ultra-deep oil and gas drilling technology has achieved leap-forward development, the well depth of 7000m has been mature, the breakthrough of 8000m has been gradually normalized, the step of 9000m has been taken, and the step of 10000m has been crossed. The cementing slurry technology is the key to guarantee the safety of cementing operation in deep and ultra-deep wells, realize long-term and efficient sealing of the cement sheath, and support the safety production of oil and gas. It runs through the whole life cycle of oil and gas well drilling, completion, production and abandonment. However, the cementing of ultra-deep and ultra-deep oil and gas wells faces complex geology and extreme working conditions such as ultra-deep (>9000m), ultra-high temperature (>200℃) and ultra-high pressure (>140MPa), which poses great challenges to key materials and systems of cementing slurry. The fluid loss additive is one of the core main agents of oil well cement slurry, which plays a crucial role in reducing the fluid loss of cement slurry, guaranteeing the stability of the system, preventing the liquid phase of cement slurry from filtering into the formation and polluting the reservoir, etc.

[0003] There are many types of fluid loss additives, among which 2-acrylamido-2-methylpropanesulfonic acid (AMPS) copolymer has become a research and application hotspot due to its excellent molecular structure designability, temperature resistance, salt resistance and strong adaptability. However, under harsh conditions such as ultra-high temperature and ultra-high pressure, the AMPS copolymer fluid loss additive still has some problems: ①Under the condition of ultra-high temperature and strong alkali, the molecular structure of the polymer is prone to conformational transition, partial hydrolysis chain scission and adsorption-desorption imbalance, etc., resulting in uncontrollable fluid loss of cement slurry and deterioration of comprehensive performance; ②The fluid loss additive is usually a linear polymer, and the high-temperature dilution characteristics are obvious, the cement slurry has poor stability at ultra-high temperature, which affects the safety of cementing construction and the sealing quality; ③It has poor adaptability in a wide temperature range, and it is difficult to meet the requirements of cement slurry rheological property, stability and mechanical strength development performance in ultra-deep and ultra-deep well cementing, such as long cementing injection stroke, small tail pipe gap friction in ultra-deep and ultra-deep well cementing, large temperature difference between top and bottom in the effective cementing section. Therefore, it is urgent to develop a high-performance fluid loss additive suitable for ultra-deep and ultra-deep well cementing to improve the comprehensive performance of the cement slurry system and meet the technical requirements of complex well cementing.

[0004] CN109503782A discloses an inorganic-organic polymer fluid loss additive, which is grafted and copolymerized by itaconic acid, acrylamide monomer, AMPS, silane coupling agent and inorganic material (one of silicon carbide, silicon dioxide and aluminum oxide) etc. The inorganic non-metallic particles and the micro-crosslinking structure of modified polymer are introduced into the existing polymer, which improves the temperature resistance of the fluid loss additive, and the cement slurry loss is controlled within 60 mL at 230℃. However, the fluid loss effect above 230℃ is not described, and the effect on other properties of the cement slurry is not investigated.

[0005] CN106188395A discloses a micro-crosslinking structure high-temperature and salt-resistant well cementing cement slurry fluid loss additive, which is prepared by free radical aqueous solution polymerization of AMPS, acrylamide (AM), unsaturated polycarboxylic acid, N-vinyl pyrrolidone (NVP) and N,N-methylene bisacrylamide (crosslinking agent) etc. The application temperature is 30-240℃, the saturated salt water resistance is good, and the cement slurry API fluid loss is less than 50 mL. However, the polymer molecular structure contains more than 15% of acrylamide by mass fraction, and the amide group is hydrolyzed into carboxyl group with strong retarding effect under high temperature and strong alkali conditions. Although the fluid loss capacity is improved, it is easy to cause the "inverted" of cement slurry thickening time and reduce the compressive strength of cement stone, thereby affecting the comprehensive performance of the cement slurry system.

[0006] Although the polymer fluid loss additives disclosed in the above prior art have improved temperature resistance and salt resistance, there are still certain defects in the comprehensive performance, especially in the application of ultra-deep and super-deep well ultra-high temperature well cementing. SUMMARY

[0007] To solve the above technical problems, the purpose of the present application is to provide a micro-crosslinking structure interlocking type fluid loss additive, its preparation method and well cementing cement slurry system. The fluid loss additive has better temperature resistance and salt resistance, better fluid loss performance, and can improve the sedimentation stability of the cement slurry system, and has no adverse effect on the comprehensive performance of the cement slurry system.

[0008] To achieve the above purpose, the first aspect of the present application provides a preparation method of a micro-crosslinking structure interlocking type fluid loss additive, which comprises the following steps:

[0009] (1) mixing 30-90 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 3-20 parts by weight of a monomer of a carboxylic acid or a derivative thereof containing a vinyl group, and water, and adding a pH adjuster to adjust the pH of the system to 6-7; further adding 5-30 parts by weight of a modified acrylamide monomer, 2-30 parts by weight of a vinyl cyclic monomer, and 0.1-3 parts by weight of a crosslinking agent including a compound containing three alkenyl groups or four alkenyl groups; and then adding 0.02-3 parts by weight of a molecular weight adjuster, 0.05-2 parts by weight of a chelating agent, and 0.2-1 part by weight of an oxidizing agent to obtain a mixed system;

[0010] (2) dropping an aqueous solution containing 0.2-1 part by weight of a reducing agent into the mixed system, and allowing the system to react for a certain period of time to obtain the micro-crosslinked structure interlocked fluid loss additive.

[0011] According to the embodiment of the present application, preferably, the weight ratio of the 2-acrylamido-2-methylpropanesulfonic acid, the monomer of the carboxylic acid or the derivative thereof containing a vinyl group, the modified acrylamide monomer, the vinyl cyclic monomer, the crosslinking agent, the molecular weight adjuster, the chelating agent, the oxidizing agent, and the reducing agent is (37-74) : (5-15) : (15-28) : (5-20) : (0.5-2) : (0.05-3) : (0.05-1.5) : (0.3-1) : (0.23-0.56).

[0012] According to the embodiment of the present application, preferably, in the step (1), the monomer of the carboxylic acid or the derivative thereof containing a vinyl group includes one or more of acrylic acid, itaconic acid, maleic anhydride, maleic acid, and fumaric acid.

[0013] According to the embodiment of the present application, preferably, in the step (1), the amount of water is 230-850 parts by weight based on 30-90 parts by weight of the 2-acrylamido-2-methylpropanesulfonic acid.

[0014] According to the embodiment of the present application, preferably, in the step (1), the pH adjuster includes an alkaline compound such as sodium hydroxide and / or potassium hydroxide.

[0015] According to the embodiment of the present application, preferably, in the step (1), the modified acrylamide monomer includes one or more of N-n-butoxymethyl acrylamide, N,N-diethyl acrylamide, N-hydroxyethyl acrylamide, diacetone acrylamide, and N-isopropyl acrylamide.

[0016] According to the embodiment of the present application, preferably, in the step (1), the vinyl cyclic monomer includes one or more of N-vinyl pyrrolidone, N-vinyl caprolactam, and vinyl cyclopentane.

[0017] According to the embodiment of the present application, preferably, in step (1), the crosslinking agent comprises one or both of triallylamine and pentaerythritol tetraallyl ether.

[0018] According to the embodiment of the present application, preferably, in step (1), the molecular weight regulator comprises one or more than two of mercaptopropionic acid, mercaptoethanol, isopropyl alcohol, dodecanethiol, hydroquinone and 2-mercaptobenzoic acid.

[0019] According to the embodiment of the present application, preferably, in step (1), the chelating agent comprises one or more than two of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate and diethylenetriamine pentaacetic acid.

[0020] According to the embodiment of the present application, preferably, in step (1), the oxidizing agent comprises one or more than two of ammonium persulfate, potassium persulfate, azobisimidozyl hydrochloride, azobisimidoform hydrochloride, hydrogen peroxide, benzoyl peroxide and cumene hydroperoxide.

[0021] According to the embodiment of the present application, preferably, in step (2), before the aqueous solution containing 0.2-1 parts by weight of the reducing agent is added to the mixed system, the mixed system is further heated to 30-60℃ under stirring at 150±50 rpm.

[0022] According to the embodiment of the present application, preferably, in step (2), the reducing agent comprises one or more than two of sodium sulfite, sodium bisulfite, ferrous sulfate, ferrous chloride, N,N-dimethylaniline and sodium hydrosulfite.

[0023] According to the embodiment of the present application, preferably, in step (2), the mass concentration of the reducing agent in the aqueous solution containing 0.2-1 parts by weight of the reducing agent is 0.4-2%.

[0024] According to the embodiment of the present application, preferably, in step (2), the time for the dropping is 30-60 min, and the temperature of the mixed system during the dropping is 30-60℃.

[0025] According to the embodiment of the present application, preferably, in step (2), the temperature of the reaction is 60-90℃, and the time of the reaction is 1-6 h.

[0026] The second aspect of the present application provides a micro-crosslinking structure interlocking type fluid loss additive prepared by the above-mentioned method for preparing a micro-crosslinking structure interlocking type fluid loss additive.

[0027] The third aspect of the present application provides a cementing slurry system, which at least comprises: cement, and the micro-crosslinking structure interlocking type fluid loss additive described above.

[0028] According to the specific embodiment of the present application, preferably, the cementing slurry system comprises: 100 parts by weight of cement, 3-5 parts by weight of the micro-crosslinking structure interlocking type fluid loss additive, 0-80 parts by weight of quartz sand, 0-6 parts by weight of stabilizer, 0-3 parts by weight of dispersant, 0-6 parts by weight of retarder, 0-0.5 parts by weight of defoamer, 0-15 parts by weight of high-temperature strength decay inhibitor, and 40-70 parts by weight of water. More preferably, the particle size of the quartz sand is 200-600 mesh.

[0029] According to the specific embodiment of the present application, preferably, the density of the cementing slurry system is 1.90±0.02 g / cm 3 .

[0030] According to the specific embodiment of the present application, the cement comprises G-grade oil well cement. The stabilizer, dispersant, retarder, and defoamer can all be products in the prior art. Specifically, the stabilizer can comprise a biopolymer high-temperature stabilizer, an acrylamide polymer ultrahigh-temperature suspension stabilizer, etc., such as one or both of high-temperature stabilizer DRK-3S and ultrahigh-temperature suspension stabilizer DRK-4L. The dispersant can comprise an aldehyde ketone polycondensate dispersant and / or a polystyrene sulfonate dispersant, etc., such as one or more of dispersant DRS-1S, dispersant SAF, dispersant SXY, dispersant USZ, and dispersant SDJZ-1. The high-temperature retarder can comprise an acrylamide polymer retarder and / or a 2-acrylamide-2-methylpropane sulfonic acid polymer retarder, etc., such as one or more of retarder DRH-2L, retarder DRH-3L, retarder JXH-2L, and retarder HX-36L. The defoamer can comprise one or more of organic ester, polyoxypropylene glycerol ether, and polydimethylsiloxane, etc., such as defoamer DRX-1L. The high-temperature strength decay inhibitor can comprise a mineral powder, etc., such as high-temperature strength decay inhibitor DRB-3S.

[0031] The present application has at least the following beneficial effects:

[0032] The micro-crosslinking polymerization technology is adopted in the present application, the reactive active points of "triple double bond" or "four double bond" are introduced into the polymer molecular structure, the structural interlocking rigid network polymer is formed through the chemical bond linkage, and through the synergistic effect among the monomers, crosslinking agents, molecular weight regulators and chelating agents, the temperature resistance, pressure resistance and salt resistance of the fluid loss agent of the present application are greatly improved, the fluid loss performance is excellent, and the settling stability of the cement slurry system under super high temperature condition and the mechanical properties of the cement stone can be significantly improved. At the same time, the fluid loss agent of the present application has no adverse effect on the thickening performance of the cement slurry system, and the thickening curve is normal. Moreover, the fluid loss agent of the present application has a wide applicable temperature range, and is applicable in the temperature range of 20-245 DEG C, and has no adverse effect on the comprehensive performance of the cement slurry system in the temperature range. In addition, the preparation method of the fluid loss agent of the present application is simple and mild, and can be mass-produced and widely applied. The fluid loss agent of the present application can be applied to various cement slurry systems of conventional density, low density and high density under medium temperature, high temperature and super high temperature, and can meet the cementing technical requirements under complex working conditions of deep well, super deep well, ultra deep well, high pressure gas well, unconventional oil and gas well, gas storage well and geothermal well, and has a wide application market. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Fig. 4 shows the effect of different curing time on the API fluid loss of the cement slurry system mixed with 5% of the fluid loss agent prepared in Example 1 and 5% of the fluid loss agent prepared in Comparative Example 1 under the condition of 245 DEG C and 130 MPa.

[0034] Figure 2 Fig. 5 shows the effect of different salt concentrations on the API fluid loss of the cement slurry system mixed with the fluid loss agent prepared in Example 1 under the condition of 245 DEG C and 130 MPa.

[0035] Figure 3 Fig. 6 shows the thickening curve of the cement slurry system mixed with 4% of the fluid loss agent prepared in Example 1 under the condition of 245 DEG C and 130 MPa. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, objects and beneficial effects of the present application, the present application will be described in detail below, but it should not be understood as limiting the scope of the present application.

[0037] It should be noted that, unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0038] Unless otherwise specified, all kinds of raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by the existing method.

[0039] It should be understood that the terms "comprise", "comprising", and / or "contain" when used herein specify the presence of stated features, integers, steps, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0040] The endpoints of the ranges and any values described herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. Each range endpoint is a separate point within that range, and each point within a range is incorporated into this disclosure as if it were individually listed. The endpoints of the ranges and any value are provided as a separate point for each end of the range and each intervening point. The same applies to any intervening point. The same applies to any intervening point.

[0041] Example 1

[0042] Take 74g 2-acrylamido-2-methylpropanesulfonic acid, 2g maleic anhydride and 4g acrylic acid, dissolve in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g N-n-butoxy methacrylamide, 5g N-vinyl pyrrolidone and 1g triallylamine and mix evenly; then add 0.05g mercaptopropionic acid, 0.05g ethylenediaminetetraacetic acid disodium and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45°C under stirring at 200 rpm, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45°C for 30 min. After the addition is completed, slowly warm up to 70°C and keep this temperature for 4h, then naturally cool to room temperature to obtain a micro-cross-linked interlocking type fluid loss additive.

[0043] It is speculated that the structure of the micro-cross-linked interlocking type fluid loss additive of the present embodiment is as shown below:

[0044]

[0045] It can be seen that the three C=C bonds in triallylamine copolymerize with other polymer monomers, and the length of the chain segment between each crosslinking point is controlled by the molecular weight regulator, generating a reticular copolymer type fluid loss additive with a micro-cross-linked interlocking structure.

[0046] Example 2

[0047] Take 58g 2-acrylamido-2-methylpropanesulfonic acid and 12g maleic anhydride, dissolve in 510g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; Then add 20g N,N-diethylacrylamide, 10g N-vinylcaprolactam and 1.5g triallylamine and mix evenly; Then add 0.2g mercaptoethanol, 0.1g ethylenediaminetetraacetic acid tetrasodium and 0.8g potassium persulfate to obtain a mixed system; The mixed system is heated to 50°C under stirring at 200rpm, and 0.37g sodium sulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 50°C for 40min, after the addition is completed, slowly heat to 75°C and keep this temperature for 3h, then naturally cool to room temperature to obtain a micro-crosslinked structure interlocking type fluid loss additive.

[0048] Example 3

[0049] Take 55g 2-acrylamido-2-methylpropanesulfonic acid and 5g itaconic acid, dissolve in 680g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; Then add 25g N-hydroxyethyl acrylamide, 15g N-vinylcaprolactam and 0.5g pentaerythritol tetraallyl ether and mix evenly; Then add 3g isopropyl alcohol, 0.5g ethylenediaminetetraacetic acid disodium and 1g azobisdimethylaminoformamide hydrochloride to obtain a mixed system; The mixed system is heated to 55°C under stirring at 150rpm, and 0.56g ferrous sulfate is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 55°C for 60min, after the addition is completed, slowly heat to 80°C and keep this temperature for 5h, then naturally cool to room temperature to obtain a micro-crosslinked structure interlocking type fluid loss additive.

[0050] Example 4

[0051] Take 37g 2-acrylamido-2-methylpropanesulfonic acid, 5g maleic acid and 10g fumaric acid, dissolve in 750g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; Then add 28g diacetone acrylamide, 20g vinylcyclopentane and 2g triallylamine and mix evenly; Then add 1.5g 2-mercaptobenzoic acid, 1.5g diethylenetriamine pentaacetic acid and 0.6g benzoyl peroxide to obtain a mixed system; The mixed system is heated to 60°C under stirring at 100rpm, and 0.3g N,N-dimethyl aniline is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 60°C for 30min, after the addition is completed, slowly heat to 65°C and keep this temperature for 6h, then naturally cool to room temperature to obtain a micro-crosslinked structure interlocking type fluid loss additive.

[0052] Example 5

[0053] Take 67 g 2-acrylamido-2-methylpropanesulfonic acid, 4 g itaconic acid and 4 g acrylic acid, dissolved in 250 g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15 g N-isopropyl acrylamide, 10 g N-vinyl caprolactam and 0.5 g pentaerythritol tetraallyl ether and mix evenly; then add 0.8 g mercaptopropionic acid, 1.2 g diethylenetriamine pentaacetic acid and 0.3 g cumene hydroperoxide to obtain a mixed system; the mixed system is heated to 50°C under stirring at 150 rpm, and 0.35 g sodium hydrosulfite is dissolved in 50 g water to prepare a reducing agent solution, which is slowly added to the mixed system at 50°C for 50 min. After the addition is completed, slowly heat to 75°C and keep the temperature for 2 h, then naturally cool to room temperature to obtain a micro-crosslinked structure interlocking type fluid loss additive.

[0054] Example 6

[0055] Take 64 g 2-acrylamido-2-methylpropanesulfonic acid, 2 g maleic anhydride and 4 g acrylic acid, dissolved in 350 g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15 g N-n-butoxymethyl acrylamide, 5 g vinyl cyclopentane and 1 g triallylamine and mix evenly; then add 0.05 g mercaptopropionic acid, 0.1 g ethylenediaminetetraacetic acid disodium and 0.5 g ammonium persulfate to obtain a mixed system; the mixed system is heated to 40°C under stirring at 200 rpm, and 0.23 g sodium bisulfite is dissolved in 50 g water to prepare a reducing agent solution, which is slowly added to the mixed system at 40°C for 60 min. After the addition is completed, slowly heat to 70°C and keep the temperature for 4 h, then naturally cool to room temperature to obtain a micro-crosslinked structure interlocking type fluid loss additive.

[0056] Comparative Example 1

[0057] Take 74 g 2-acrylamido-2-methylpropanesulfonic acid, 2 g maleic anhydride and 4 g acrylic acid, dissolved in 350 g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15 g N-n-butoxymethyl acrylamide and 5 g N-vinyl pyrrolidone and mix evenly; then add 0.05 g mercaptopropionic acid, 0.05 g ethylenediaminetetraacetic acid disodium and 0.5 g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45°C under stirring at 200 rpm, and 0.23 g sodium bisulfite is dissolved in 50 g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45°C for 30 min. After the addition is completed, slowly heat to 70°C and keep the temperature for 4 h, then naturally cool to room temperature to obtain a fluid loss additive.

[0058] Comparative Example 2

[0059] Take 79g 2-acrylamido-2-methylpropanesulfonic acid, 2g maleic anhydride and 4g acrylic acid, dissolved in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g N, N-dimethyl acrylamide and mix well; then add 0.05g ethylenediaminetetraacetic acid disodium and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45℃ under stirring at 200r / min, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45℃ for 30min, after the addition is completed, slowly heat to 70℃ and keep this temperature for 4h, then naturally cool to room temperature to obtain a water loss reducing agent.

[0060] Comparative Example 3

[0061] Take 74g 2-acrylamido-2-methylpropanesulfonic acid, dissolved in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g N-n-butoxymethyl acrylamide, 5g N-vinyl pyrrolidone and 1g triallylamine and mix well; then add 0.05g mercaptopropionic acid, 0.05g ethylenediaminetetraacetic acid disodium and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45℃ under stirring at 200r / min, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45℃ for 30min, after the addition is completed, slowly heat to 70℃ and keep this temperature for 4h, then naturally cool to room temperature to obtain a water loss reducing agent.

[0062] Comparative Example 4

[0063] Take 74g 2-acrylamido-2-methylpropanesulfonic acid, 2g maleic anhydride and 4g acrylic acid, dissolved in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g N-n-butoxymethyl acrylamide and 1g triallylamine and mix well; then add 0.05g mercaptopropionic acid, 0.05g ethylenediaminetetraacetic acid disodium and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45℃ under stirring at 200r / min, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45℃ for 30min, after the addition is completed, slowly heat to 70℃ and keep this temperature for 4h, then naturally cool to room temperature to obtain a water loss reducing agent.

[0064] Comparative Example 5

[0065] Take 74g 2-acrylamido-2-methylpropanesulfonic acid, 2g maleic anhydride and 4g acrylic acid, dissolved in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g acrylamide, 5g N-vinylpyrrolidone and 1g N, N-methylene bisacrylamide and mix evenly; then add 0.05g mercaptopropionic acid, 0.05g disodium ethylenediaminetetraacetate and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45℃ under stirring at 200rpm, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45℃ for 30min, after the addition is completed, slowly heat to 70℃ and keep this temperature for 4h, then naturally cool to room temperature to obtain a water loss reducing agent.

[0066] Comparative Example 6

[0067] Take 74g 2-acrylamido-2-methylpropanesulfonic acid, 2g maleic anhydride and 4g acrylic acid, dissolved in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g acrylamide, 5g N-vinylpyrrolidone and 1g N, N-methylene bisacrylamide and mix evenly; then add 0.05g mercaptopropionic acid, 0.05g disodium ethylenediaminetetraacetate and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45℃ under stirring at 200rpm, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45℃ for 30min, after the addition is completed, slowly heat to 70℃ and keep this temperature for 4h, then naturally cool to room temperature to obtain a water loss reducing agent.

[0068] Comparative Example 7

[0069] Take 74g 2-acrylamido-2-methylpropanesulfonic acid, 2g maleic anhydride and 4g acrylic acid, dissolved in 350g water, slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g acrylamide, 5g N-vinylpyrrolidone and 1g N, N-methylene bisacrylamide and mix evenly; then add 0.05g mercaptopropionic acid, 0.05g disodium ethylenediaminetetraacetate and 0.5g ammonium persulfate to obtain a mixed system; the mixed system is heated to 45℃ under stirring at 200rpm, and 0.23g sodium bisulfite is dissolved in 50g water to prepare a reducing agent solution, which is slowly added to the mixed system at 45℃ for 30min, after the addition is completed, slowly heat to 70℃ and keep this temperature for 4h, then naturally cool to room temperature to obtain a water loss reducing agent.

[0070] Comparative Example 8

[0071] Weigh 20g of 2-acrylamido-2-methylpropanesulfonic acid, 2g of maleic anhydride, and 4g of acrylic acid, dissolve them in 350g of water, and slowly add sodium hydroxide to adjust the pH of the system to 6-7; then add 15g of N-butoxymethacrylamide, 40g of N-vinylpyrrolidone, and 8g of triallylamine and mix well; then add 0.05g of mercaptopropionic acid, 0.05g of disodium ethylenediaminetetraacetate, and 0.5g of ammonium persulfate to obtain a mixed system; heat the mixed system to 45℃ under stirring at 200 rpm, and dissolve 0.23g of sodium bisulfite in 50g of water to prepare a reducing agent solution. Slowly add the reducing agent solution dropwise to the mixed system at 45℃ over 30min. After the addition is complete, slowly heat to 70℃ and maintain this temperature for 4h. Then, allow it to cool naturally to room temperature to obtain a dehydration reducer.

[0072] Test case

[0073] When the experimental temperature is less than 180℃, the performance of the fluid loss reducer shall be evaluated in accordance with the methods described in GB / T 19139-2012 "Test Methods for Oil Well Cement" and SY / T 5504.2-2013 "Evaluation Methods for Oil Well Cement Admixtures Part 2: Fluid Loss Reducers". When the experimental temperature is greater than or equal to 180℃, the evaluation method for the water loss reduction performance of the water loss reducing agent is as follows: Place the cement slurry system containing the water loss reducing agent in the slurry cup of the high-temperature and high-pressure thickener. After completing the thickening test steps in the above standard, raise the temperature to the corresponding experimental temperature and pressure within the set time, and maintain constant temperature and pressure for 30 minutes. Then, cool down to about 90℃, remove the cement slurry system, and clean the oil on the top of the cement slurry system. Then, use a constant speed stirrer to stir the cement slurry system evenly, and place it in the preheated high-temperature and high-pressure water loss tester cylinder. After completing the operation in the above standard, slowly raise the temperature to the corresponding experimental temperature, and ensure that the pressure difference between the top of the cylinder and the bottom condenser is 6.9MPa. After raising the temperature to the experimental temperature, conduct the water loss test and record the water loss in 30 minutes. The API water loss of the cement slurry system is twice the water loss in 30 minutes.

[0074] The formula for cement slurry system with an experimental temperature of 20-90℃ is: 600g Grade G oil well cement (HSR) + x% fluid loss reducer + (44-x)% water.

[0075] The cement slurry system formula for an experimental temperature of 120-150℃ is as follows: 600g Grade G oil well cement (HSR) + x% fluid loss reducer + 35% quartz sand (200 mesh) + 0.6% high-temperature stabilizer DRK-3S + 1% dispersant DRS-1S + 2% ultra-high temperature retarder DRH-3L + 0.5% defoamer DRX-1L + (55-x)% water. The density of the cement slurry system is 1.90 g / cm³. 3 .

[0076] Cement slurry system formulation at 180-200°C experimental temperature: 500 g of G-class oil well cement (HSR) + x% of fluid loss additive + 50% of quartz sand (200 mesh) + 1% of high-temperature stabilizer DRK-3S + 3% of ultra-high-temperature suspending stabilizer DRK-4L + 2% of dispersant DRS-1S + 3% of ultra-high-temperature retarder DRH-3L + 0.5% of defoaming agent DRX-1L + (60-x)% of water. The density of the cement slurry system is 1.90 g / cm 3 .

[0077] Cement slurry system formulation at 220-245°C experimental temperature: 500 g of G-class oil well cement (HSR) + x% of fluid loss additive + 70% of quartz sand (200 mesh) + 1% of high-temperature stabilizer DRK-3S + 3% of ultra-high-temperature suspending stabilizer DRK-4L + 2% of dispersant DRS-1S + 5% of ultra-high-temperature retarder DRH-3L + 0.5% of defoaming agent DRX-1L + 10% of high-temperature strength decay inhibitor DRB-3S + (70-x)% of water. The density of the cement slurry system is 1.90 g / cm 3 .

[0078] It should be noted that the percentages (%) in the above cement slurry system formulations represent the mass percentages of each material with respect to the mass of the G-class oil well cement, i.e., the mass of each material accounts for 100% of the mass of the G-class oil well cement. The amount of fluid loss additive in the above cement slurry system is shown in Table 1. In addition, the water in the above cement slurry system formulation is fresh water or saturated brine (i.e., 36% NaCl aqueous solution), as shown in Table 1.

[0079] The results of the evaluation of the comprehensive performance of the fluid loss additives prepared in the above examples and comparative examples are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] In Table 1, “*” represents the mass concentration, and “—” represents not measured.

[0084] As shown in Table 1, with the increase of experimental temperature, the API fluid loss of the cement slurry system with the same formulation containing the fluid loss additive of the embodiment of the application changes little, the temperature resistance of the fluid loss additive of the embodiment of the application reaches 245℃, and the salt water saturation resistance is good. When the experimental temperature is 20-150℃, the API fluid loss of the cement slurry system containing 3% of the fluid loss additive prepared by the embodiment 1 of the application can be controlled below 50 mL, the sedimentation stability is good, there is no free liquid, and the 24h cement stone compressive strength is high. When the experimental temperature is 180-245℃, by properly increasing the amount of the fluid loss additive, the API fluid loss of the cement slurry system can also be reduced to below 50 mL, the cement slurry setting time is not more than 30s, and the field mixing requirements can be met. In addition, with the increase of experimental temperature, the density difference of the cement slurry system slightly increases, but the sedimentation stability (i.e. the density difference) can be controlled below 0.03 / cm 3 In addition, the API fluid loss of the cement slurry system containing 5% of the fluid loss additive prepared by the embodiment 1 of the application is also below 50 mL under the condition of 245℃ and saturated salt water. Meanwhile, under the condition of 245℃, the API fluid loss, setting time, sedimentation stability and mechanical strength of the cement stone of the cement slurry system containing the fluid loss additive prepared by the embodiments 1-6 of the application are all high.

[0085] In addition, compared with the comparative example 1, the fluid loss performance, sedimentation stability and cement stone compressive strength of the cement slurry system containing the fluid loss additive prepared by the embodiment 1 of the application under the condition of 90℃ are not much different from those of the comparative example 1; however, the performances of the fresh water and saturated salt water cement slurry systems containing the fluid loss additive prepared by the embodiment 1 of the application under the condition of 245℃ are much better than those of the comparative example 1; which shows that the molecular structure of the micro-crosslinking structure interlocking type fluid loss additive of the application is superior, and has excellent fluid loss performance, sedimentation stability and ultra-high temperature and salt resistance.

[0086] The fluid loss additive prepared by the comparative example 2 is a typical linear anionic polymer, and its performances under the condition of 90℃ are not much different from those of the fluid loss additive prepared by the embodiment 1 of the application, but the API fluid loss of the fresh water cement slurry system containing the fluid loss additive prepared by the comparative example 2 under the condition of 245℃ is large, the sedimentation stability is poor, and the cement stone compressive strength is greatly affected, the fluid loss of the salt water cement slurry system is uncontrollable, and other performances are further reduced.

[0087] The difference between Comparative Example 3 and Example 1 is that the vinyl-containing carboxylic acid or its derivative monomers are omitted; the difference between Comparative Example 4 and Example 1 is that the vinyl cyclic monomer is omitted; the difference between Comparative Example 5 and Example 1 is that N-n-butoxymethacrylamide is replaced with acrylamide, and the crosslinking agent is replaced with N,N-methylenebisacrylamide; the difference between Comparative Example 6 and Example 1 is that the molecular weight regulator and chelating agent are omitted; Comparative Examples 7 and 8 are examples where the proportions of certain monomers or crosslinking agents used in Example 1 are adjusted to be outside the scope of this invention. It can be seen that the water loss reducing agents of Comparative Examples 3-8 all exhibit problems such as high API water loss, poor sedimentation stability, and significant impact on the compressive strength of cement stone at 245°C, and their thickening curves show bulging.

[0088] Figure 1 The effect of different curing times at 245℃ and 130MPa on the API water loss of cement slurry systems (fresh water) containing 5% of the water-reducing agent prepared in Example 1 and Comparative Example 1, respectively, is shown. Figure 1 It can be seen that the water loss of the cement slurry system with the addition of Example 1 changes little with curing time, and the API water loss of the cement slurry system within the curing time range of 10 hours at 245℃ is less than 50mL, indicating that its molecular structure and performance are stable under ultra-high temperature conditions, and can meet the technical requirements of ultra-deep and ultra-thick well cementing for ultra-high temperature and ultra-long cementing operations. In contrast, the water loss of the cement slurry system with the addition of Comparative Example 1 gradually increases with the extension of curing time. The API water loss of the cement slurry system cured at 245℃ for 2 hours is greater than 100mL, and the water loss is even greater in the later stages, which seriously affects the comprehensive performance and construction safety of the ultra-deep and ultra-thick well ultra-high temperature cement slurry system.

[0089] Figure 2 The effect of different salt concentrations on the API water loss of a cement slurry system incorporating the water-reducing agent prepared in Example 1 was shown at 245℃ and 130MPa. Figure 2 It can be seen that the water loss of the cement slurry system with 4% of Example 1 gradually increases with the increase of salt concentration, but the API water loss of the saturated brine system is still less than 100 mL; the water loss of the cement slurry system with 5% of Example 1 is less affected by salt concentration, and the API water loss of the saturated brine cement slurry system can be controlled below 50 mL, indicating that the water loss reducing agent prepared in Example 1 of this invention has strong resistance to ultra-high temperature and salt.

[0090] Figure 3 The thickening curve of the cement slurry system containing 4% of the water loss reducing agent prepared in Example 1 is shown at 245°C and 130 MPa. Figure 3It can be seen that the thickening curve of the cement slurry system under the condition of ultra-high temperature and high pressure is normal, temperature and pressure have no abnormal fluctuation, the initial consistency of the system is 15Bc, the consistency changes little with the increase of temperature, and finally maintains at about 11Bc, and the thickening time of the cement slurry system is 450min. It shows that the fluid loss additive has no adverse effect on the initial flow state, high-temperature sedimentation stability and thickening performance of the cement slurry system.

[0091] In conclusion, the micro-crosslinking structure interlocking type fluid loss additive has excellent temperature resistance, pressure resistance and salt resistance, the temperature resistance and pressure resistance can reach 245 DEG C and 130MPa, and the salt resistance can reach saturation; the fluid loss performance is excellent; the sedimentation stability of the cement slurry system under the condition of ultra-high temperature and the mechanical properties of the cement stone can be significantly improved; the thickening curve of the cement slurry system is normal, and the thickening performance has no adverse effect; and the application temperature range is wide, which is applicable to the temperature range of 20-245 DEG C. Therefore, the micro-crosslinking structure interlocking type fluid loss additive has excellent comprehensive performance, and can overcome the defects of the polymer type fluid loss additive in the prior art, such as poor temperature resistance and salt resistance, strong high-temperature dilution, poor sedimentation stability of the cement slurry system, inverted thickening time, great influence on the mechanical strength of the cement stone, etc., and has a good application prospect in the cementing field of deep well, ultra-deep well, super-deep well, high-pressure gas well, unconventional oil and gas well, gas storage well and geothermal well.

[0092] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application, and it should be understood that the above description is only for specific embodiments of the present application and is not used to limit the protection scope of the present application, and any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a micro-crosslinked interlocking type water loss reducing agent, comprising the following steps: (1) Mix 30-90 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 3-20 parts by weight of vinyl carboxylic acid or its derivative monomer and water, and add a pH adjuster to adjust the pH of the system to 6-7; then add 5-30 parts by weight of modified acrylamide monomer, 2-30 parts by weight of vinyl cyclic monomer and 0.1-3 parts by weight of crosslinking agent, wherein the crosslinking agent includes compounds containing three alkenyl or four alkenyl groups; then add 0.02-3 parts by weight of molecular weight adjuster, 0.05-2 parts by weight of chelating agent and 0.2-1 parts by weight of oxidant to obtain a mixed system; (2) Add an aqueous solution containing 0.2-1 parts by weight of reducing agent dropwise to the mixed system. After the addition is complete, react for a period of time to obtain the micro-crosslinked interlocking type water loss reducing agent. The vinyl-containing carboxylic acid or its derivative monomer includes one or more of acrylic acid, itaconic acid, maleic anhydride, maleic acid, and fumaric acid; the modified acrylamide monomer includes one or more of N-butoxymethylacrylamide, N,N-diethylacrylamide, N-hydroxyethylacrylamide, diacetone acrylamide, and N-isopropylacrylamide.

2. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, The weight ratio of the 2-acrylamido-2-methylpropanesulfonic acid, the vinyl-containing carboxylic acid or its derivative monomer, the modified acrylamide monomer, the vinyl cyclic monomer, the crosslinking agent, the molecular weight regulator, the chelating agent, the oxidizing agent and the reducing agent is (37-74):(5-15):(15-28):(5-20):(0.5-2):(0.05-3):(0.05-1.5):(0.3-1):(0.23-0.56).

3. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (1), the amount of water used is 230-850 parts by weight, based on 30-90 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid.

4. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (1), the vinyl cyclic monomer includes one or more of N-vinylpyrrolidone, N-vinylcaprolactam, and vinylcyclopentane.

5. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (1), the crosslinking agent includes one or both of triallylamine and pentaerythritol tetraallyl ether.

6. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (1), the molecular weight regulator includes one or more of mercaptopropionic acid, mercaptoethanol, isopropanol, dodecyl mercaptoethanol, hydroquinone, and 2-mercaptobenzoic acid.

7. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (1), the chelating agent includes one or more of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, and diethylenetriaminepentaacetic acid.

8. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (1), the oxidant includes one or more of ammonium persulfate, potassium persulfate, azobisisobutyrazoline hydrochloride, azobisisobutyramidine hydrochloride, hydrogen peroxide, benzoyl peroxide and cumene hydrogen peroxide.

9. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (2), before adding the aqueous solution containing 0.2-1 parts by weight of reducing agent to the mixed system, the process further includes heating the mixed system to 30-60°C under stirring at 150±50 rpm.

10. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (2), the reducing agent includes one or more of sodium sulfite, sodium bisulfite, ferrous sulfate, ferrous chloride, N,N-dimethylaniline and sodium dithionite.

11. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (2), the dripping time is 30-60 min, and the temperature of the mixing system during the dripping process is 30-60℃.

12. The preparation method of the micro-crosslinked interlocking type water loss reducing agent according to claim 1, wherein, In step (2), the reaction temperature is 60-90℃ and the reaction time is 1-6h.

13. A micro-crosslinked interlocking type water loss reducing agent, prepared by the method of any one of claims 1-12.

14. A cementing slurry system, said cementing slurry system comprising at least: Cement, and the micro-crosslinked interlocking water loss reducing agent as described in claim 13.

15. The cementing slurry system according to claim 14, wherein, The cementing slurry system comprises: 100 parts by weight of cement, 3-5 parts by weight of the micro-crosslinked interlocking fluid loss reducing agent, 0-80 parts by weight of quartz sand, 0-6 parts by weight of stabilizer, 0-3 parts by weight of dispersant, 0-6 parts by weight of retarder, 0-0.5 parts by weight of defoamer, 0-15 parts by weight of high-temperature strength degradation inhibitor, and 40-70 parts by weight of water.

16. The cementing slurry system according to claim 14, wherein, The density of the cement slurry system is 1.90 ± 0.02 g / cm³. 3 .

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