Oil well cement preservative, high temperature cement slurry for oil and gas well cementing and preparation method thereof

Abstract

The application provides an oil well cement preservative, a high-temperature cement slurry for oil and gas well cementing and a preparation method. The preparation of the oil well cement preservative comprises the following steps: modifying epoxy resin with 2-acrylamido-2-methylpropanesulfonic acid aqueous modification, and recovering the solvent through reduced pressure distillation to obtain an aqueous epoxy resin; adding diisopropoxy di(ethoxyacetoacetyl) titanium to the aqueous epoxy resin to graft and synthesize, and thus the oil well cement preservative is obtained. The corrosion-resistant medium-temperature cement slurry for oil and gas well cementing comprises the oil well cement preservative, microsilica, cement, fly ash, a dispersing agent, a fluid loss additive, a retarder, a defoaming agent and water. The corrosion-resistant high-temperature cement slurry for oil and gas well cementing comprises the oil well cement preservative, silicon powder, microsilica, cement, fly ash, a dispersing agent, a fluid loss additive, a retarder, a defoaming agent and water. The oil well cement preservative of the application can be solidified into a film in cement without using a curing agent, and the compatibility problem of the epoxy resin curing agent and the cement slurry is solved.

Description

Technical Field

[0001] This invention belongs to the field of oil well cementing technology. Specifically, it relates to an oil well cement corrosion inhibitor and its preparation method, a corrosion-resistant medium-temperature cement slurry for oil and gas well cementing and its preparation method, and a corrosion-resistant high-temperature cement slurry for oil and gas well cementing and its preparation method. Background Technology

[0002] With the deepening of oil and gas resource exploration and development, corrosion from acidic gases containing high levels of H2S and CO2 has become a significant challenge in oil and gas field development both domestically and internationally. In the high-temperature, high-pressure (HTHP) environment downhole, H2S and CO2 can even be in a supercritical state, exhibiting even stronger corrosiveness and severely threatening the integrity of the cement sheath. As the first line of defense in oil and gas extraction, the cement sheath plays a crucial role in the lifespan of oil and gas wells and the safe extraction of oil and gas resources. The cement sheath refers to the cement stone formed between the casing and the formation by cement slurry. Its function is to support and suspend the casing, seal formation fluids, prevent inter-layer flow, and bond the casing and formation together through the cement sheath (i.e., cement stone) after cementing operations. If the cement sheath is severely corroded by H2S and CO2 and loses its mechanical properties, it will cause the cement sheath seal to fail. Corrosive gases will then directly act on the casing and tubing, ultimately leading to well abandonment. In more severe cases, harmful gases may leak to the surface, seriously threatening life and property safety.

[0003] Currently used anti-H2S and CO2 corrosion materials mainly include inorganic materials such as microsilica and volcanic ash, and organic materials such as resins and latexes. Adding inorganic anti-corrosion materials can increase the density of cement stone and effectively reduce its calcium hydroxide content, thus improving its resistance to H2S and CO2 corrosion. However, the dosage of these inorganic anti-corrosion materials is limited, and volcanic ash and other inorganic materials contain a large amount of aluminum oxide. In an H2S-rich environment, sulfates, aluminum oxides, and calcium hydroxide will transform into ettringite, causing the cement stone to expand and generate microcracks, damaging the integrity of the cement ring. Organic anti-corrosion materials such as latexes and resins can not only reduce the porosity of cement stone but also form a film on the surface of hydration products, blocking the contact between the cement stone and corrosive gases. However, field practice shows that latexes have poor stability, easily generate a large number of air bubbles in the cement slurry, increase the permeability of the cement stone, and reduce the anti-corrosion effect. Epoxy resins have poor compatibility in cement slurry and lack suitable curing agents for use in cement slurry, limiting the anti-corrosion performance of resin-cement slurries.

[0004] Chinese invention patent CN106947446A discloses a low-density cement slurry system for corrosion protection and its preparation method, comprising the following components by weight: 65-90 parts of G-grade cement, 10-35 parts of cementing weight-reducing material, 10-30 parts of non-permeable agent, 1.8-2.2 parts of oil well cement fluid loss reducer, 1-1.5 parts of cement corrosion inhibitor, and 55-90 parts of water. However, it cannot improve the cement stone's resistance to H2S and CO2 corrosion. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a method for preparing an oil well cement corrosion inhibitor. Another objective of this invention is to provide an oil well cement corrosion inhibitor. Yet another objective of this invention is to provide a corrosion-resistant medium-temperature and high-temperature oil and gas well cementing slurry. A further objective of this invention is to provide a method for preparing a corrosion-resistant medium-temperature and high-temperature oil and gas well cementing slurry.

[0006] To achieve the above objectives, one aspect of the present invention provides an oil well cement corrosion inhibitor and its preparation method. The preparation method includes the following steps: modifying an epoxy resin with waterborne 2-acrylamido-2-methylpropanesulfonic acid, recovering the solvent by vacuum distillation to obtain a waterborne epoxy resin, wherein the mass ratio of epoxy resin to 2-acrylamido-2-methylpropanesulfonic acid is 1:(1-1.5); dissolving the waterborne epoxy resin in water, and then adding diisopropoxydi(ethoxyacetyl)titanium to graft and synthesize the oil well cement corrosion inhibitor, wherein the mass ratio of waterborne epoxy resin to water is 1:(4-6), and the mass ratio of waterborne epoxy resin to diisopropoxydi(ethoxyacetyl)titanium is 10:(1-3).

[0007] For example, the mass ratio of epoxy resin to 2-acrylamido-2-methylpropanesulfonic acid is 1:(1.2 to 1.4), the mass ratio of waterborne epoxy resin to water is 1:(4.5 to 5.5), and the mass ratio of waterborne epoxy resin to diisopropoxydi(ethoxyacetyl)titanium is 10:(1.5 to 2.5).

[0008] In an exemplary embodiment of the present invention, the water-based modification step may include: dissolving epoxy resin in n-butanol solvent, introducing nitrogen gas, heating to 80-110°C, adding acetone solution of benzoyl peroxide dropwise to obtain a reaction solution; slowly adding 2-acrylamido-2-methylpropanesulfonic acid dropwise to the reaction solution, and reacting at a constant temperature for 3-4 hours.

[0009] In an exemplary embodiment of the present invention, the temperature of the isothermal reaction can be 80–110°C.

[0010] In an exemplary embodiment of the present invention, the grafting synthesis can be achieved by stirring at room temperature and high speed for 2 to 4 hours to obtain an oil well cement corrosion inhibitor.

[0011] Another aspect of the present invention provides an oil well cement corrosion inhibitor, which is prepared by the method described above.

[0012] In an exemplary embodiment of the present invention, the oil well cement corrosion inhibitor may be a self-crosslinking waterborne epoxy resin.

[0013] Another aspect of the present invention provides a corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing, wherein the corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing comprises, by weight, 3-7 parts of oil well cement corrosion inhibitor as described in claim 5, 4-6 parts of microsilica, 90-110 parts of cement, 4-6 parts of fly ash, 0.5-2 parts of dispersant, 1-3 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, and 0.1-0.5 parts of defoamer, wherein the water-to-solid ratio of the corrosion-resistant oil and gas well cement slurry is 0.37-0.45.

[0014] For example, a corrosion-resistant high-temperature cement slurry for oil and gas well cementing is provided. The corrosion-resistant high-temperature cement slurry for oil and gas well cementing, by weight, includes 3-7 parts of oil well cement corrosion inhibitor, 25-35 parts of silica fume, 4-6 parts of microsilica, 90-110 parts of cement, 4-6 parts of fly ash, 0.5-2 parts of dispersant, 1-3 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, and 0.1-0.5 parts of defoamer, wherein the water-to-solid ratio of the corrosion-resistant oil and gas well cement slurry is 0.37-0.45.

[0015] Another aspect of the present invention provides a method for preparing a corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing. The preparation method includes the following steps: thoroughly mixing cement, silica, fly ash and dispersant to obtain a dry mixture; mixing oil well cement corrosion inhibitor, fluid loss reducer, retarder, defoamer and water to obtain a mixing water; and adding the dry mixture to the mixing water and stirring at high speed to obtain a corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing.

[0016] For example, a method for preparing a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells is provided. The preparation method includes the following steps: thoroughly mixing cement, silica fume, microsilica, fly ash and dispersant to obtain a dry mixture; mixing oil well cement corrosion inhibitor, fluid loss reducer, retarder, defoamer and water to obtain slurry water; and adding the dry mixture to the slurry water and stirring at high speed to obtain a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells.

[0017] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0018] 1) This oil well cement corrosion inhibitor does not require the use of emulsifiers and can be stored for a long time.

[0019] 2) Oil well cement corrosion inhibitors can cure into films in cement without the need for curing agents, solving the problem of compatibility between epoxy resin curing agents and cement slurry.

[0020] 3) The oil well cement corrosion inhibitor has good compatibility with other admixtures and has a beneficial effect on the basic properties of cement slurry.

[0021] 4) Oil well cement corrosion inhibitors improve the resistance of cement sheaths to CO2 and H2S corrosion. Attached Figure Description

[0022] Figure 1 A synthetic route diagram of exemplary embodiment 1 of the present invention is shown.

[0023] Figure 2 A micrograph of the hydration products of cement stone before modification, as shown in Example 1 of the present invention, is displayed.

[0024] Figure 3 A microscopic image of the modified cement stone hydration product of Example 1 of the present invention is shown. Detailed Implementation

[0025] In the following description, an oil well cement corrosion inhibitor, a high-temperature cement slurry for oil and gas well cementing, and a preparation method thereof will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0026] To address the technical problem of insufficient cross-linking and curing of resin-based corrosion inhibitors in oil well cement slurry, this invention provides an oil well cement corrosion inhibitor, a corrosion-resistant oil well cement slurry, and its preparation method. This oil well cement corrosion inhibitor does not require the use of an emulsifier, can be stored for approximately 6–12 months, and solves the problem of controlling the curing time of epoxy resin cement slurry and selecting a suitable resin curing agent under high-temperature and high-pressure conditions (80–200℃, 20–50 MPa) and high-alkali and high-salt environments in the cement slurry.

[0027] Among them, the factors affecting curing time and curing effect mainly include the type of curing agent, curing temperature, pressure and pH. (1) Since oil well cement slurry contains a variety of additives, in order to ensure that the curing agent does not affect other properties of cement slurry (e.g., thickening properties) when the resin is cured, a large amount of curing agent screening work is required, which greatly increases the workload and cost. (2) Generally, the higher the temperature, the shorter the resin curing time. The curing time of resin is also different for wells with different temperatures, which makes it more difficult to control the resin curing time. (3) The existing curing process uses both resin and curing agent together, but the curing reaction of curing agent and resin in a highly alkaline cement slurry environment is difficult to control.

[0028] First exemplary embodiment

[0029] In a first exemplary embodiment of the present invention, a method for preparing an oil well cement corrosion inhibitor is provided, the method comprising the following steps:

[0030] Step 1: The epoxy resin is modified with waterborne 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The solvent is recovered by vacuum distillation to obtain waterborne epoxy resin, wherein the mass ratio of epoxy resin to 2-acrylamido-2-methylpropanesulfonic acid is 1:(1~1.5).

[0031] Optionally, the mass ratio of epoxy resin to 2-acrylamido-2-methylpropanesulfonic acid is 1:(1~1.5). Too little 2-acrylamido-2-methylpropanesulfonic acid will result in poor waterborne properties of the final waterborne epoxy resin, while too much 2-acrylamido-2-methylpropanesulfonic acid will result in a large amount of unreacted 2-acrylamido-2-methylpropanesulfonic acid remaining in the solution, affecting the efficiency of subsequent modification.

[0032] Optionally, the epoxy resin can be E44 type epoxy resin, and 2-acrylamido-2-methylpropanesulfonic acid can also be called AMPS. An acetone solution of benzoyl peroxide is used as the initiator; benzoyl peroxide can also be called BPO.

[0033] Among them, reduced pressure distillation can recover and reuse solvents, reducing the content of organic solvents in the product.

[0034] In this exemplary embodiment, the water-based modification time can be 3 to 6 hours.

[0035] Alternatively, a waterborne modification time of less than 3 hours will result in poor waterborneization of the final waterborne epoxy resin and low conversion rate. A waterborne modification time of more than 6 hours will increase costs.

[0036] In this exemplary embodiment, the water-based modification step may include: dissolving epoxy resin in n-butanol solvent, introducing nitrogen gas, heating to 80-110°C, adding acetone solution of benzoyl peroxide dropwise to obtain a reaction solution; slowly adding 2-acrylamido-2-methylpropanesulfonic acid dropwise to the reaction solution, and reacting at a constant temperature for 3-4 hours.

[0037] Optionally, the volume ratio of n-butanol solvent to epoxy resin can be (3-4):1, the volume ratio of benzoyl peroxide to acetone can be 1.5:10, and the amount of initiator benzoyl peroxide added is 2-3% of the epoxy resin.

[0038] The epoxy resin is fully dissolved in n-butanol solvent, with a dissolution time of 3-5 minutes. After the oxygen is exhausted, an acetone solution containing benzoyl peroxide is slowly added dropwise at a rate of approximately 5 mg / s (for example, based on 30 g of epoxy resin, this means it should be added within 20 minutes). Adding the initiator too quickly will cause explosive polymerization, while adding it too slowly will affect the reaction conversion rate.

[0039] Alternatively, since the acetone solution of benzoyl peroxide is used as an initiator to initiate the reaction in an anaerobic environment, nitrogen gas needs to be introduced throughout the entire reaction process.

[0040] Optionally, the epoxy resin is dissolved in n-butanol solvent, nitrogen gas is introduced, and the temperature is raised to 80-110°C. Temperatures below 80°C will result in poor water-based properties and low conversion rate of the final waterborne epoxy resin, while temperatures above 110°C will cause the solvent n-butanol to evaporate.

[0041] In this exemplary embodiment, the temperature of the isothermal reaction can be 80–110°C.

[0042] Step 2: After dissolving the waterborne epoxy resin in water, add diisopropoxydi(ethoxyacetyl)titanium to synthesize the oil well cement corrosion inhibitor. The mass ratio of waterborne epoxy resin to water is 1:(4-6), and the mass ratio of waterborne epoxy resin to diisopropoxydi(ethoxyacetyl)titanium is 10:(1-3).

[0043] Among them, waterborne epoxy resin is a viscous liquid. Waterborne epoxy resin dissolved in water has good dispersibility, which is beneficial for subsequent reaction with self-crosslinking monomers.

[0044] Optionally, the mass ratio of waterborne epoxy resin to water is 1:(4-6), and the waterborne epoxy resin needs to be completely dispersed in water to form an emulsion. Too little water will result in the final waterborne epoxy resin not being completely dispersed in water, while too much water will result in a low conversion rate and poor self-crosslinking ability in the subsequent self-crosslinking reaction.

[0045] Optionally, the mass ratio of waterborne epoxy resin to diisopropyloxydi(ethoxyacetyl)titanium is a suitable ratio of 10:(1-3) self-crosslinking monomers. Too low a concentration of diisopropyloxydi(ethoxyacetyl)titanium will result in weak or even non-crosslinking of the final oil well cement corrosion inhibitor. Too high a concentration of diisopropyloxydi(ethoxyacetyl)titanium will result in poor storage stability of the self-crosslinking underwater epoxy resin, making it unsuitable for long-term storage. In this exemplary embodiment, the graft synthesis can obtain the oil well cement corrosion inhibitor by stirring at high speed at room temperature for 2-4 hours.

[0046] Among them, stirring time of less than 2 hours will result in poor self-crosslinking ability and low conversion rate of the final oil well cement corrosion inhibitor, while stirring time of more than 4 hours will affect the storage stability of the oil well cement corrosion inhibitor.

[0047] Optionally, stirring at a speed of 500–900 RPM can help improve the conversion rate of graft synthesis.

[0048] Figure 1 A synthetic route diagram of exemplary embodiment 1 of the present invention is shown. For example... Figure 1 As shown, 2-acrylamido-2-methylpropanesulfonic acid undergoes a grafting reaction with the active sites of epoxy resin under the action of an initiator (BPO), grafting onto the epoxy resin and introducing waterborne groups, thus achieving self-emulsification of the epoxy resin and obtaining a waterborne epoxy resin. The obtained waterborne epoxy resin reacts with the isopropoxy groups in diisopropoxydi(ethoxyacetyl)titanium, causing the diisopropoxydi(ethoxyacetyl)titanium to be grafted onto the waterborne epoxy resin, resulting in the final oil well cement corrosion inhibitor. At a certain temperature (e.g., above 80°C), the ethoxyacetyl groups react with the epoxy groups, leading to resin crosslinking.

[0049] Second exemplary embodiment

[0050] In a second exemplary embodiment of the present invention, an oil well cement corrosion inhibitor is provided, which is prepared by the above-described method for preparing oil well cement corrosion inhibitor.

[0051] In this exemplary embodiment, the oil well cement corrosion inhibitor may be a self-crosslinking waterborne epoxy resin.

[0052] Third Exemplary Example

[0053] In a third exemplary embodiment of the present invention, a corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing is provided. The corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing, by weight, comprises 3 to 7 parts of oil well cement corrosion inhibitor, 4 to 6 parts of microsilica, 90 to 110 parts of cement, 4 to 6 parts of fly ash, 0.5 to 2 parts of dispersant, 1 to 3 parts of fluid loss reducing agent, 0.1 to 0.5 parts of retarder, and 0.1 to 0.5 parts of defoamer, wherein the water-to-solid ratio of the corrosion-resistant oil and gas well cement slurry is 0.37 to 0.45.

[0054] For example, the corrosion-resistant medium-temperature cement slurry for oil and gas well cementing can be formulated by weight as follows: 3.5–6 parts oil well cement corrosion inhibitor, 4.5–5.5 parts microsilica, 95–105 parts cement, 4.5–5.5 parts fly ash, 0.5–1 part dispersant, 1–2 parts fluid loss reducer, 0.2–0.4 parts retarder, and 0.2–0.4 parts defoamer. The water-to-solid ratio of the cement slurry is 0.39–0.43. The weight range of each component in the corrosion-resistant medium-temperature cement slurry for oil and gas well cementing can be adjusted flexibly according to the actual working conditions.

[0055] Alternatively, the cement slurry can be prepared at room temperature.

[0056] The water-to-solid ratio is the mass ratio of liquid materials (water, oil well cement corrosion inhibitors, etc.) to solid materials (cement, microsilica, etc.).

[0057] Optionally, both microsilica and fly ash may be supplied by Sichuan Qingnian Company. The dispersant may be SD35 dispersant, which is a sulfonated ketone aldehyde condensate. The fluid loss reducing agent may be SD130 fluid loss reducing agent, which is an AMPS polymer. The retarder may be SD21 retarder, which is also an AMPS polymer. The defoamer may be D50 defoamer, which is dimethyl silicone oil. The cement may be Grade G high sulfate-resistant oil well cement, which is supplied by Jiahua Cement.

[0058] Among them, oil well cement corrosion inhibitors cross-link and solidify in cement stone. Some form resin particles that fill the pores of cement stone, reducing its permeability; others form a resin film that covers the surface of cement stone hydration products, reducing direct contact between acidic media and these products. Both methods improve the corrosion resistance of cement stone.

[0059] Among them, medium-temperature cement slurry for oil wells refers to cement slurry suitable for temperatures between 80 and 110℃.

[0060] When the temperature exceeds 80℃, the ethoxyacetyl groups in diisopropoxydi(ethoxyacetyl)titanium react with the epoxy resin, ultimately leading to resin cross-linking and achieving an anti-corrosion effect. Oil well cement corrosion inhibitors cross-link and solidify in cement stone; some form resin particles that fill the pores of the cement stone, reducing its permeability; others form a resin film that covers the surface of the cement stone hydration products, reducing direct contact between acidic media and these products.

[0061] In this exemplary embodiment, the corrosion-resistant oil and gas well cement slurry is resistant to CO2 and H2S corrosion.

[0062] Alternatively, carbon capture and storage (CCS) is a method of geologically sequestering CO2 to achieve emission reduction. Currently, considering technical and economic conditions, it is the only method that can achieve large-scale, low-cost CO2 emission reduction. However, geological sequestration requires cement stone with good corrosion resistance. The corrosion inhibitor of this invention can effectively reduce the rate of CO2 erosion of cement stone, thereby improving the corrosion resistance of cement stone and ensuring the safe and effective implementation of CO2 geological sequestration.

[0063] Fourth exemplary embodiment

[0064] In a fourth exemplary embodiment of the present invention, a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells is provided. The corrosion-resistant high-temperature cement slurry for cementing oil and gas wells comprises, by weight, 3-7 parts of oil well cement corrosion inhibitor, 25-35 parts of silica fume, 4-6 parts of microsilica, 90-110 parts of cement, 4-6 parts of fly ash, 0.5-2 parts of dispersant, 1-3 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, and 0.1-0.5 parts of defoamer, wherein the water-to-solid ratio of the corrosion-resistant cement slurry for cementing oil and gas wells is 0.37-0.45.

[0065] For example, the corrosion-resistant high-temperature cement slurry for oil and gas well cementing can be categorized by weight as follows: 3.5–6 parts oil well cement corrosion inhibitor, 28–32 parts silica fume, 4.5–5.5 parts microsilica, 95–105 parts cement, 4.5–5.5 parts fly ash, 0.5–1 part dispersant, 1–2 parts fluid loss reducer, 0.2–0.4 parts retarder, and 0.2–0.4 parts defoamer. The water-to-solid ratio of the cement slurry is 0.39–0.43. The weight range of each component in the corrosion-resistant high-temperature cement slurry for oil and gas well cementing can be adjusted flexibly according to the actual working conditions.

[0066] Alternatively, the cement slurry can be prepared at room temperature.

[0067] The water-to-solid ratio is the mass ratio of liquid materials (water, oil well cement corrosion inhibitors, etc.) to solid materials (cement, microsilica, etc.).

[0068] Optionally, microsilica, silica fume, and fly ash are all supplied by Sichuan Qingnian Company. The dispersant can be SD35, which is a sulfonated ketone aldehyde condensate. The fluid loss reducer can be SD130, an AMPS polymer. The retarder can be SD21, also an AMPS polymer. The defoamer can be D50, a dimethyl silicone oil. The cement can be Grade G high sulfate-resistant oil well cement, specifically from Jiahua Cement. The oil well cement corrosion inhibitor cross-links and solidifies in the cement stone; some form resin particles that fill the pores of the cement stone, reducing its permeability; others form a resin film that covers the surface of the cement stone hydration products, reducing direct contact between acidic media and these products. Both methods improve the corrosion resistance of the cement stone.

[0069] Optionally, silica fume can increase the silica-calcium ratio of cement and maintain cement strength at high temperatures.

[0070] Among them, high-temperature cement slurry for oil wells refers to cement slurry suitable for temperatures above 110℃.

[0071] When the temperature exceeds 80℃, the ethoxyacetyl groups in diisopropoxydi(ethoxyacetyl)titanium react with the epoxy resin, ultimately leading to resin cross-linking and achieving an anti-corrosion effect. Oil well cement corrosion inhibitors cross-link and solidify in cement stone; some form resin particles that fill the pores of the cement stone, reducing its permeability; others form a resin film that covers the surface of the cement stone hydration products, reducing direct contact between acidic media and these products.

[0072] In this exemplary embodiment, the corrosion-resistant high-temperature cement slurry for oil and gas well cementing is resistant to CO2 and H2S corrosion.

[0073] Alternatively, carbon capture and storage (CCS) is a method of geologically sequestering CO2 to achieve emission reduction. Currently, considering technical and economic conditions, it is the only method that can achieve large-scale, low-cost CO2 emission reduction. However, geological sequestration requires cement stone with good corrosion resistance. The corrosion inhibitor of this invention can effectively reduce the rate of CO2 erosion of cement stone, thereby improving the corrosion resistance of cement stone and ensuring the safe and effective implementation of CO2 geological sequestration.

[0074] Fifth exemplary embodiment

[0075] In a fifth exemplary embodiment of the present invention, a method for preparing a corrosion-resistant intermediate-temperature cement slurry for cementing oil and gas wells is provided. The preparation method includes the following steps: thoroughly mixing cement, silica, fly ash and dispersant to obtain a dry mixture; mixing oil well cement corrosion inhibitor, fluid loss reducer, retarder, defoamer and water to obtain a mixing water; and adding the dry mixture to the mixing water and stirring at high speed to obtain a corrosion-resistant intermediate-temperature cement slurry for cementing oil and gas wells.

[0076] Sixth Exemplary Embodiment

[0077] In a sixth exemplary embodiment of the present invention, a method for preparing a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells is provided. The preparation method includes the following steps: thoroughly mixing cement, silica fume, microsilica, fly ash and dispersant to obtain a dry mixture; mixing oil well cement corrosion inhibitor, fluid loss reducer, retarder, defoamer and water to obtain a mixing water; and adding the dry mixture to the mixing water and stirring at high speed to obtain a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells.

[0078] To better understand the exemplary embodiments of the present invention described above, specific examples are provided below to illustrate an oil well cement corrosion inhibitor, a high-temperature cement slurry for oil and gas well cementing, and a preparation method thereof.

[0079] Example 1

[0080] The preparation method of this example oil well cement corrosion inhibitor includes the following steps:

[0081] (1) First, dissolve the epoxy resin (E44) in n-butanol solvent, then transfer it to a three-necked flask, introduce nitrogen gas as a protective gas, heat to 90°C, slowly add acetone solution of initiator benzoyl peroxide, maintain the reaction temperature at 90°C, and continue to slowly add 2-acrylamido-2-methylpropanesulfonic acid. Under these reaction conditions, react for 4 hours, and obtain waterborne epoxy resin by recovering the solvent by vacuum distillation.

[0082] The volume ratio of n-butanol solvent to epoxy resin is 3.5:1, the amount of benzoyl peroxide in acetone solution added is 20% of the epoxy resin, and the mass ratio of epoxy resin to 2-acrylamido-2-methylpropanesulfonic acid is 1:1.25.

[0083] (2) Dissolve the prepared waterborne epoxy resin in tap water, then transfer it to a three-necked flask, slowly add diisopropoxydi(ethoxyacetyl)titanium, and stir at high speed at room temperature for 3 hours to obtain an oil well cement corrosion inhibitor.

[0084] The mass ratio of waterborne epoxy resin to water is 1:4, and the mass ratio of waterborne epoxy resin to diisopropyloxybis(ethoxyacetyl)titanium is 10:2.

[0085] Figure 2 The following is a micrograph of the hydration products of cement stone before modification, as shown in Example 1 of the present invention. Figure 3 A microscopic image of the modified cement stone hydration products of Example 1 of the present invention is shown. For example... Figure 2 and Figure 3 As shown, the surface of the hydration products of cement stone with added oil well cement corrosion inhibitor is covered with a resin film, which is the main reason why the corrosion inhibitor improves the corrosion resistance of cement stone.

[0086] Application Example 1

[0087] This example illustrates the preparation of a corrosion-resistant, medium-temperature cement slurry for cementing oil and gas wells. The preparation method includes the following steps:

[0088] (1) First, mix G-grade high sulfate-resistant oil well cement, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0089] (2) Then mix the oil well cement corrosion inhibitor, water loss reducer, retarder, defoamer and water to obtain slurry water.

[0090] (3) Finally, the dry mixture is added to the slurry water and stirred at high speed until uniform, thus obtaining corrosion-resistant oil well cement slurry.

[0091] The components are weighed according to the following mass ratio: 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 3 parts of the oil well cement corrosion inhibitor from Example 1; and a water-to-solid ratio of 0.42.

[0092] Application Example 2

[0093] This example illustrates the preparation of a corrosion-resistant, medium-temperature cement slurry for cementing oil and gas wells. The preparation method includes the following steps:

[0094] (1) First, mix G-grade high sulfate-resistant oil well cement, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0095] (2) Then mix the oil well cement corrosion inhibitor, water loss reducer, retarder, defoamer and water to obtain slurry water.

[0096] (3) Finally, the dry mixture is added to the slurry water and stirred at high speed until uniform, thus obtaining corrosion-resistant oil well cement slurry.

[0097] The components are weighed according to the following mass ratio: 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 5 parts of the oil well cement corrosion inhibitor from Example 1; water-to-solid ratio 0.42.

[0098] Application Example 3

[0099] This example illustrates the preparation of a corrosion-resistant, medium-temperature cement slurry for cementing oil and gas wells. The preparation method includes the following steps:

[0100] (1) First, mix G-grade high sulfate-resistant oil well cement, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0101] (2) Then mix the oil well cement corrosion inhibitor, water loss reducer, retarder, defoamer and water to obtain slurry water.

[0102] (3) Finally, the dry mixture is added to the slurry water and stirred at high speed until uniform, thus obtaining corrosion-resistant oil well cement slurry.

[0103] The components are weighed according to the following mass ratio: 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 7 parts of the oil well cement corrosion inhibitor from Example 1; and a water-to-solid ratio of 0.42.

[0104] Comparative Example 1

[0105] The preparation method in this example includes the following steps:

[0106] (1) First, mix G-grade high sulfate-resistant oil well cement, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0107] (2) Then mix the epoxy resin emulsion (conventional epoxy resin), water loss reducer, retarder, defoamer and water to obtain a wet mixture.

[0108] (3) Finally, the dry mixture is added to the wet mixture and stirred at high speed until uniform, thus obtaining the comparative cement slurry.

[0109] The components are weighed according to the following mass ratio: 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 7 parts epoxy resin emulsion; water-to-solid ratio 0.42.

[0110] Application Example 4

[0111] This example illustrates the preparation of a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells. The preparation method includes the following steps:

[0112] (1) First, mix G-grade high sulfate-resistant oil well cement, silica fume, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0113] (2) Then mix the oil well cement corrosion inhibitor, water loss reducer, retarder, defoamer and water to obtain slurry water.

[0114] (3) Finally, the dry mixture is added to the slurry water and stirred at high speed until uniform, thus obtaining corrosion-resistant oil well cement slurry.

[0115] The components are weighed according to the following mass ratios: 30 parts silica fume; 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 3 parts of the oil well cement corrosion inhibitor from Example 1; and a water-to-solid ratio of 0.42.

[0116] Application Example 5

[0117] This example illustrates the preparation of a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells. The preparation method includes the following steps:

[0118] (1) First, mix G-grade high sulfate-resistant oil well cement, silica fume, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0119] (2) Then mix the oil well cement corrosion inhibitor, water loss reducer, retarder, defoamer and water to obtain slurry water.

[0120] (3) Finally, the dry mixture is added to the slurry water and stirred at high speed until uniform, thus obtaining corrosion-resistant oil well cement slurry.

[0121] The components are weighed according to the following mass ratios: 30 parts silica fume; 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 5 parts of the oil well cement corrosion inhibitor from Example 1; and a water-to-solid ratio of 0.42.

[0122] Application Example 6

[0123] This example illustrates the preparation of a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells. The preparation method includes the following steps:

[0124] (1) First, mix G-grade high sulfate-resistant oil well cement, silica fume, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0125] (2) Then mix the oil well cement corrosion inhibitor, water loss reducer, retarder, defoamer and water to obtain slurry water.

[0126] (3) Finally, the dry mixture is added to the slurry water and stirred at high speed until uniform, thus obtaining corrosion-resistant oil well cement slurry.

[0127] The components are weighed according to the following mass ratios: 30 parts silica fume; 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 7 parts of the oil well cement corrosion inhibitor from Example 1; and a water-to-solid ratio of 0.42.

[0128] Comparative Example 2

[0129] The preparation method in this example includes the following steps:

[0130] (1) First, mix G-grade high sulfate-resistant oil well cement, silica fume, microsilica, fly ash and dispersant to the maximum extent to obtain dry mix.

[0131] (2) Then mix the epoxy resin emulsion (conventional epoxy resin), water loss reducer, retarder, defoamer and water to obtain a wet mixture.

[0132] (3) Finally, the dry mixture is added to the wet mixture and stirred at high speed until uniform, thus obtaining the comparative cement slurry.

[0133] The components are weighed according to the following mass ratio: 30 parts silica fume; 5 parts microsilica; 100 parts G-grade high sulfate-resistant oil well cement; 5 parts fly ash; 1 part SD35 dispersant; 2 parts SD130 water loss reducer; 0.3 parts SD21 retarder; 0.3 parts D50 defoamer; 7 parts epoxy resin emulsion; water-to-solid ratio 0.42.

[0134] The relevant properties of cement slurry were tested according to the requirements of GB / T19139-2012 "Test Methods for Cement in Oil Wells" and GB10238-2015 "Cement in Oil Wells". The permeability test of cement stone was conducted according to the requirements of GB / T29172-2012 "Core Analysis Methods". The results are shown in Tables 1, 2, 3 and 4.

[0135] Table 1 Comprehensive Performance of Cement Grout

[0136]

[0137] Table 1 shows the properties of cement slurry and cement stone under curing conditions of 85℃. This corrosion inhibitor has no adverse effect on the density of the cement slurry, but it slightly increases the fluidity and initial consistency, all within the range ensuring construction safety. This corrosion inhibitor can reduce the free liquid and water loss of the cement slurry, improve its stability, and also increase the compressive strength of the cement stone formed after curing.

[0138] Table 2 Corrosion resistance of cement stone under conditions of 20% H2S content and 15% CO2 content.

[0139]

[0140]

[0141] Table 3 Comprehensive Performance of Cement Grout

[0142]

[0143] Table 3 shows the properties of cement slurry and cement stone under curing conditions of 200℃. This corrosion inhibitor has no adverse effect on the density of the cement slurry, but it slightly increases the fluidity and initial consistency, all within safe construction ranges. This corrosion inhibitor can reduce the free liquid and water loss of the cement slurry, improve its stability, and also increase the compressive strength of the cement stone formed after curing.

[0144] Table 4. Corrosion resistance of cement stone under conditions of 20% H2S content and 15% CO2 content.

[0145]

[0146] In summary, the present invention exhibits excellent overall performance and meets construction requirements. Compared with the comparative example, the application example demonstrates good resistance to CO2 and H2S corrosion in both medium-temperature and high-temperature environments, with minimal increase in permeability and a corrosion depth of less than 4 mm.

[0147] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art will understand that various modifications can be made to the above examples without departing from the spirit and scope of the claims.

Claims

1. A method for preparing an oil well cement corrosion inhibitor, characterized in that, The preparation method includes the following steps: Epoxy resin was modified with waterborne 2-acrylamido-2-methylpropanesulfonic acid, and the solvent was recovered by vacuum distillation to obtain a waterborne epoxy resin, wherein the mass ratio of epoxy resin to 2-acrylamido-2-methylpropanesulfonic acid is 1:(1~1.5); and A water-based epoxy resin was dissolved in water, and then diisopropyloxydi(ethoxyacetyl)titanium was added dropwise for grafting synthesis to obtain an oil well cement corrosion inhibitor. The mass ratio of water-based epoxy resin to water was 1:(4~6), and the mass ratio of water-based epoxy resin to diisopropyloxydi(ethoxyacetyl)titanium was 10:(1~3). The grafting synthesis was carried out by stirring at high speed at room temperature for 2~4 hours to obtain the oil well cement corrosion inhibitor.

2. The method for preparing the oil well cement corrosion inhibitor according to claim 1, characterized in that, The water-based modification steps include: Epoxy resin was dissolved in n-butanol solvent, nitrogen gas was introduced, the temperature was raised to 80-110℃, and an acetone solution of benzoyl peroxide was added dropwise to obtain the reaction solution; and Slowly add 2-acrylamido-2-methylpropanesulfonic acid to the reaction solution and react at a constant temperature for 3-4 hours.

3. The method for preparing the oil well cement corrosion inhibitor according to claim 2, characterized in that, The temperature of the isothermal reaction is 80~110℃.

4. An oil well cement corrosion inhibitor, characterized in that, The oil well cement corrosion inhibitor is prepared by the preparation method of the oil well cement corrosion inhibitor according to any one of claims 1 to 3.

5. The oil well cement corrosion inhibitor according to claim 4, characterized in that, The oil well cement corrosion inhibitor is a self-crosslinking waterborne epoxy resin.

6. A corrosion-resistant intermediate-temperature cement slurry for cementing oil and gas wells, characterized in that, The corrosion-resistant medium-temperature cement slurry for oil and gas well cementing, by weight, comprises 3-7 parts of oil well cement corrosion inhibitor, 4-6 parts of microsilica, 90-110 parts of cement, 4-6 parts of fly ash, 0.5-2 parts of dispersant, 1-3 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, and 0.1-0.5 parts of defoamer, as described in claim 4, wherein the water-to-solid ratio of the corrosion-resistant oil and gas well cement slurry is 0.37-0.

45.

7. A corrosion-resistant high-temperature cement slurry for cementing oil and gas wells, characterized in that, The corrosion-resistant medium-temperature cement slurry for oil and gas well cementing comprises, by weight, 3-7 parts of the oil well cement corrosion inhibitor as described in claim 4, 25-35 parts of silica fume, 4-6 parts of microsilica, 90-110 parts of cement, 4-6 parts of fly ash, 0.5-2 parts of dispersant, 1-3 parts of fluid loss reducing agent, 0.1-0.5 parts of retarder, and 0.1-0.5 parts of defoamer, wherein the water-to-solid ratio of the corrosion-resistant oil and gas well cement slurry is 0.37-0.

45.

8. A method for preparing corrosion-resistant intermediate-temperature cement slurry for oil and gas well cementing as described in claim 6, characterized in that, The preparation method includes the following steps: The cement, silica fume, fly ash, and dispersant are thoroughly mixed to obtain a dry mix. Oil well cement corrosion inhibitor, fluid loss reducer, retarder, defoamer, and water are mixed to obtain slurry mixing water; and The dry mixture is added to the slurry mixing water and stirred at high speed until uniform, thus obtaining a corrosion-resistant medium-temperature cement slurry for cementing oil and gas wells.

9. A method for preparing the corrosion-resistant high-temperature cement slurry for oil and gas well cementing as described in claim 7, characterized in that, The preparation method includes the following steps: The cement, silica fume, microsilica, fly ash and dispersant are thoroughly mixed to obtain a dry mix; Oil well cement corrosion inhibitor, fluid loss reducer, retarder, defoamer, and water are mixed to obtain slurry mixing water; and The dry mixture is added to the slurry mixing water and stirred at high speed until uniform, thus obtaining a corrosion-resistant high-temperature cement slurry for cementing oil and gas wells.

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