Surface glaze-sealed hollow glass microspheres and preparation method thereof, high-temperature, high-strength, low-density cement slurry and application thereof

Abstract

The present invention discloses a surface-glazed hollow glass microsphere, a preparation method thereof, a high-temperature, high-strength, low-density cement slurry, and applications thereof. The preparation method comprises: adding the hollow glass microspheres to an anhydrous ethanol solution, dripping a silane coupling agent, separating, rinsing, and drying to obtain hollow glass microspheres with the surface grafted with the silane coupling agent; adding the hollow glass microspheres with the surface grafted with the silane coupling agent and an active monomer containing a chelating group to deionized water, mixing them, adding an initiator to react, adding a polymerization inhibitor, and washing and drying to obtain hollow glass microspheres with the surface grafted with the chelating group; adding a first suspension stabilizer, a nano-scale glaze sealing material, and an auxiliary agent to the deionized water, stirring uniformly to prepare a glaze sealing slurry; spraying the glaze sealing slurry on the hollow glass microspheres with the surface grafted with the chelating group, vacuum drying, and firing to obtain the surface-glazed hollow glass microspheres. The surface-glazed hollow glass microspheres have improved resistance to corrosion by highly alkaline substances in the cement slurry and the ability to maintain structural stability.

Description

Technical Field

[0001] The present invention relates to the technical field of well drilling, completion and cementing, and in particular to a surface-glazed hollow glass microsphere and a preparation method thereof, and a high-temperature, high-strength and low-density cement slurry and application thereof. Background Art

[0002] With the deepening exploration and development of deep formations and the continuous advancement of petroleum technology, the number of deep and ultra-deep wells drilled has increased rapidly, with drilling capacity exceeding 9,000 meters and reaching a new level of 10,000 meters. However, the drilling and completion of deep and ultra-deep wells often face complex challenges such as low formation pressure bearing capacity, high leakage, a narrow safe density window, and limited injection and displacement rates. This makes it difficult to ensure cement slurry return and sealing quality. Furthermore, high-temperature conditions cause rapid hydration rates, high pH values, and significant differences in hydration products compared to low-temperature conditions, significantly impacting cement slurry admixtures and additives. Traditional lightening agents—hollow glass microspheres—are susceptible to high temperatures (greater than 150°C) and the varying physical and chemical properties of Portland cement. They experience volume expansion and contraction in their macrostructure and erosion and dissolution of their skeletal structure in their microstructure. This results in slow high-temperature strength development, low values, and significant attenuation in low-density cement slurries. This hinders cement sheath integrity, hinders wellbore simplification, and restricts the implementation of subsequent operations such as fracturing and acidizing.

[0003] In summary, there are still certain deficiencies and room for improvement when using the existing conventional glass bead low-density cement slurry system to carry out cementing operations under complex conditions such as deep wells, ultra-deep wells, and low-pressure and leaky layers. It is urgent to improve the mechanical properties of the low-density cement slurry system while ensuring the construction performance such as slurry thickening, rheology, and stability, so as to provide technical support for the exploration and development of deep oil and gas resources. Summary of the Invention

[0004] To reduce surface defects in glass microsphere lighteners, improve their ability to resist corrosion from highly alkaline substances in cement slurries, and maintain structural stability, thereby reducing the risk of cracks and delamination between the glass microspheres and the cement matrix. This invention aims to improve lighteners used in cementing deep, low-pressure, leaky layers and high-temperature conditions, thereby imparting high-temperature resistance and high-strength mechanical properties to cementing slurries. A surface-glazed hollow glass microsphere, a preparation method thereof, a high-temperature, high-strength, low-density cement slurry, and their applications are provided.

[0005] In a first aspect, an embodiment of the present invention provides a method for preparing hollow glass microspheres for surface glaze sealing. The raw material composition of the hollow glass microspheres for surface glaze sealing comprises, in parts by mass: 36.5 to 40.5 parts of hollow glass microspheres, 2.9 to 3.3 parts of a silane coupling agent, 9.2 to 11 parts of an active monomer containing a chelating group, 44.8 to 50.3 parts of a nano-scale glaze sealing material, 0.9 to 1 part of an auxiliary agent, and 1.3 to 1.5 parts of a first suspension stabilizer.

[0006] The preparation method may include:

[0007] adding the hollow glass microspheres into an anhydrous ethanol solution, and dropwise adding a silane coupling agent, separating, rinsing, and drying to obtain hollow glass microspheres with the silane coupling agent grafted on the surface;

[0008] The hollow glass microspheres with the surface grafted silane coupling agent and the active monomer containing the chelate group are added into deionized water and mixed, an initiator is added to react, a polymerization inhibitor is added, and the hollow glass microspheres with the surface grafted chelate group are prepared after washing and drying;

[0009] Adding the first suspension stabilizer, the nano-scale glaze sealing material and the auxiliary agent into deionized water and stirring evenly to prepare a glaze sealing slurry;

[0010] The hollow glass microbeads with grafted chelating groups on the surface are sprayed with glaze slurry, vacuum dried and fired to obtain the hollow glass microbeads with surface glaze sealing.

[0011] In one embodiment, the hollow glass microspheres have a compressive strength of 12,000 psi.

[0012] In one embodiment, the silane coupling agent is γ-methacryloxypropyltrimethoxysilane.

[0013] In one embodiment, the active monomer containing a chelating group is itaconic acid and / or fumaric acid.

[0014] In one embodiment, the nano-scale glaze sealing material includes, by mass, 16.7 to 33.3 parts of 300 to 500 nm nano-dolomite, 25 to 33.3 parts of 100 to 500 nm nano-zircon powder, 15.4 to 33.3 parts of 400 to 1000 nm nano-sodium potassium stone powder, and 16.7 to 23.1 parts of 50 to 300 nm nano-strontium carbonate powder.

[0015] In one embodiment, the auxiliary agent is at least one of the following: sodium tripolyphosphate, sodium tetraphosphate, and sodium tannate.

[0016] In one embodiment, the first suspension stabilizer is bentonite and / or china clay.

[0017] In one embodiment, the preparation method may specifically include:

[0018] The hollow glass microspheres are added to an anhydrous ethanol solution, and a silane coupling agent is added dropwise at 60-70° C. within 1 hour; the mixture is cooled to room temperature, separated using a high-speed centrifuge, and the separated product is washed with deionized water until neutral, and dried to obtain hollow glass microspheres with the silane coupling agent grafted on the surface;

[0019] The hollow glass microspheres with a surface grafted silane coupling agent and an active monomer containing a chelating group are added to deionized water, mixed, stirred evenly, adjusted to a neutral pH value, and supplemented with deionized water so that the solid content of the suspension reaches 15 wt %; a protective gas is introduced, the temperature is raised to 50° C., an initiator is added to react, and the temperature is kept and stirred for 6 to 8 hours; the protective gas is turned off, an inhibitor is added, stirred, and then cooled to room temperature, washed with clean water, and spray-dried to obtain hollow glass microspheres with a surface grafted chelating group;

[0020] Adding the first suspension stabilizer, the nano-scale glaze sealing material, and the auxiliary agent into deionized water, replenishing the deionized water so that the content of the nano-scale glaze sealing material in the suspension reaches 70 wt %, and stirring evenly to prepare a glaze sealing slurry;

[0021] The sealing slurry is evenly sprayed onto the hollow glass microspheres with chelating groups grafted onto the surface by a spraying method; dried in a vacuum oven at 60°C for 1 day and at 110°C for 2 days, and sieved; fired in a high-temperature electric furnace at 800-1200°C for 8-10 hours, cooled and sieved to obtain a powder material as the surface glaze sealing hollow glass microspheres.

[0022] In a second aspect, an embodiment of the present invention provides a surface-glazed hollow glass microsphere, which is prepared according to the preparation method of the surface-glazed hollow glass microsphere described in the first aspect.

[0023] In a third aspect, an embodiment of the present invention provides a high-temperature, high-strength, low-density cement slurry. The raw material composition of the high-strength, low-density cement slurry includes, in parts by mass: 100 parts of G-grade oil well cement, 29 to 60 parts of the surface glaze-sealed hollow glass microspheres described in the second aspect, 15 parts of high-temperature strength decay-reducing material, 4 parts of high-temperature anti-cracking material, 2 to 3 parts of a second suspension stabilizer, 1.2 to 2 parts of a dispersant, 4.3 to 5 parts of a high-temperature fluid loss additive, 2 to 2.5 parts of a high-temperature retarder, 1 part of a defoaming agent, and 67 to 80 parts of tap water.

[0024] In one embodiment, the high-temperature strength degradation material is formed by compounding 325-mesh composite silicon powder and 1500-mesh crystalline silicon powder in a mass ratio of 5:1.

[0025] In one embodiment, the high-temperature anti-cracking material includes, by mass, 10 parts of 1-3 mm calcium sulfate whiskers, 30 parts of 2-4 mm basalt fibers, 20 parts of 1-3 mm aluminum oxide whiskers, and 40 parts of styrene-butadiene rubber powder.

[0026] In a fourth aspect, an embodiment of the present invention provides an application of the high-temperature, high-strength, low-density cement slurry described in the third aspect in well completion and cementing.

[0027] The beneficial effects of the above technical solutions provided by the embodiments of the present invention include at least:

[0028] The embodiment of the present invention provides a surface glaze-sealed hollow glass microsphere and its preparation method, high-temperature, high-strength, low-density cement slurry and its application. The surface glaze-sealed hollow glass microsphere is used as a lightening agent, and its hollow and low-density characteristics are used to adjust the density of the cement slurry; a silane coupling agent is used to graft a molecular chain rich in adsorption groups (-COOH) on the surface of the hollow glass microsphere, and the adsorption and chelation between -COOH and heavy metal ions in nano-inorganic mineral powder are used to improve the adhesion effect of the glaze slurry on the surface of the hollow glass microsphere; a small molecule organic acid salt is used as an auxiliary agent to assist the uniform coating and deep penetration of the glaze material on the surface of the hollow glass microsphere. On this basis, through variable temperature continuous drying, the cracking of the glaze slurry on the surface of the hollow glass microsphere due to rapid escape of water or uneven escape rate is avoided; and then through low-temperature firing, a hollow glass microsphere with a layer of heat-resistant and corrosion-resistant enamel layer on the surface is finally obtained, thereby improving its macroscopic mechanical properties and the ability to resist corrosion from cement hydration products, formation fluids, etc., and improving the structural integrity and compressive strength of low-density cement stone under high-temperature working conditions at the bottom of the well.

[0029] High temperature, high strength and low density cement slurry density is adjustable (1.30~1.50g / cm 3 ), 180℃ high temperature 24h compressive strength greater than 18MPa, 48h compressive strength greater than 25MPa, low API water loss, good rheological properties, free liquid is 0, density difference less than 0.05g / cm 3 It provides strong technical support for reducing the risk of lost circulation during cementing construction and ensuring the exploration and development benefits of difficult-to-use reserves and unconventional oil and gas resources in complex deep wells and ultra-deep wells.

[0030] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 This is a thickening curve diagram provided in Example 1 of the present invention;

[0034] Figure 2 This is a thickening curve diagram provided in Example 2 of the present invention;

[0035] Figure 3 This is a thickening curve diagram provided in Example 3 of the present invention;

[0036] Figure 4 This is a thickening curve diagram provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0037] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0038] In view of the fact that the existing conventional glass bead low-density cement slurry system still has certain shortcomings and room for improvement when carrying out cementing operations under complex conditions such as deep wells, ultra-deep wells, low-pressure and leaky layers, and the technical problem of being unable to improve the mechanical properties of the low-density cement slurry system while ensuring the construction performance such as slurry thickening, rheology and stability, the present invention is proposed to provide a surface glaze-sealed hollow glass microsphere and its preparation method, high-temperature and high-strength low-density cement slurry and its application that overcome the above problems or at least partially solve the above problems.

[0039] Description of raw materials for the examples of the present invention and the comparative examples:

[0040] Hollow glass microspheres, commercially available, with a compressive strength of 12,000 psi.

[0041] The silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH-570), which is chemically pure and commercially available.

[0042] The active monomer containing a chelating group is one or both of itaconic acid (IA) and fumaric acid (FA), which are chemically pure and commercially available.

[0043] The nano-grade glaze sealing material comprises, by mass, 16.7 to 33.3 parts of 300-500nm nano-dolomite, 25 to 33.3 parts of 100-500nm nano-zircon powder, 15.4 to 33.3 parts of 400-1000nm nano-sodium potassium stone powder, and 16.7 to 23.1 parts of 50-300nm nano-strontium carbonate powder. It is industrial grade and commercially available.

[0044] The auxiliary agent is one or more of sodium tripolyphosphate, sodium tetraphosphate and sodium tannate, which are industrial grade and commercially available.

[0045] The suspension stabilizer is bentonite or china clay, industrial grade, commercially available.

[0046] Sodium hydroxide (NaOH) solution (concentration 30 wt%) and dilute hydrochloric acid solution (concentration 4 mol / L) were used as pH adjusters, both of chemically pure and commercially available. The protective gas during the polymerization reaction was high-purity argon (Ar), industrial grade, commercially available. The solvents used were deionized water and anhydrous ethanol, both of analytically pure and commercially available.

[0047] G-grade oil well cement, high sulfate resistance (HSR), Jiahua Special Cement Co., Ltd.; high-temperature strength anti-recession material, made from a mixture of 325-mesh composite silica powder and 1500-mesh crystalline silica powder in a mass ratio of 5:1, Hongrun Quartz Silica Powder Co., Ltd.

[0048] The dispersant is a commercially available ketone-aldehyde oil well cement dispersant.

[0049] The high-temperature anti-cracking material is composed of commercially available inorganic chopped fibers and polymer resins. The specific ratios are as follows by weight: calcium sulfate whiskers (1-3mm) are 10%, basalt fibers (2-4mm) are 30%, alumina whiskers (1-3mm) are 20%, and styrene-butadiene rubber powder (50-100um) is 40%. The above materials are weighed according to the proportion, stirred evenly, and packaged for later use.

[0050] The defoaming agent is one of commercially available tributyl phosphate, polyoxypropylene glycerin, and polydimethylsiloxane.

[0051] The fluid loss additive is homemade according to Example 5 in patent application number 202010137114.6.

[0052] The retarder is self-made according to the patent application number 201610539424.4.

[0053] The second suspension stabilizer is a weak gel polymer, which is self-made according to Example 2 in the patent application number 202110009555.2.

[0054] It should also be noted that the experimental methods in the following examples without specific conditions are based on conventional methods and conditions. The raw materials in the following examples without specific manufacturers and product numbers were all purchased from conventional commercial sources.

[0055] Example 1

[0056] (1) Pretreatment of hollow glass microspheres

[0057] 40.5 parts of hollow glass microspheres were added to 150 parts of anhydrous ethanol solution, stirred at 150 r / min for 30 minutes, and 3.3 parts of KH570 were added dropwise at 60°C within 1 hour. After cooling to room temperature, the mixture was separated using a high-speed centrifuge, and the separated material was rinsed with deionized water until neutral, and dried to obtain hollow glass microspheres with surface grafted silane coupling agent for use.

[0058] Hollow glass microspheres with a surface grafted silane coupling agent and 11 parts of IA are added to deionized water and mixed, and stirred at 120 r / min; the pH value of the suspension is adjusted to 7; deionized water is added to make the solid content of the suspension reach 15wt%; Ar is introduced, and the temperature is raised to 50°C; APS is added, and the temperature is kept and stirred for 6 hours; Ar is turned off, PBQ is added, and stirring is continued for 20 minutes; cooling, washing with clean water, and spray drying are carried out to prepare hollow glass microspheres with a surface grafted chelating group.

[0059] (2) Preparation of glaze slurry

[0060] Weigh a certain mass of deionized water and 1.3 parts of bentonite, and stir them at 300 r / min; weigh 44.8 parts of glaze sealing material, of which 33.3% is nano-dolomite powder, 25% is nano-zircon powder, 25% is nano-sodium potassium stone powder, and 16.7% is nano-strontium carbonate powder, and stir them at 1500 r / min; weigh 0.9 parts of sodium tripolyphosphate, and stir them at 1500 r / min; add deionized water so that the content of nano-scale glaze sealing material in the suspension reaches 70wt%, and stir them at 1500 r / min to obtain glaze sealing slurry.

[0061] (3) Preparation of surface glaze-sealed hollow glass microspheres

[0062] ①Use the spraying method to evenly spray the prepared glaze slurry onto the pre-treated hollow glass beads to ensure that the glaze slurry is fully infiltrated and wrapped on the surface of the hollow glass beads.

[0063] ② The hollow glass microspheres with the sealing slurry were moved into a vacuum oven, dried at 60°C for 1 day and 110°C for 2 days, and sieved; placed in a high-temperature electric furnace, and fired at 1200°C for 8 hours; cooled, sieved, and the obtained powder material was the surface glaze sealing hollow glass microspheres (A).

[0064] The second step is the preparation of high temperature, high strength and low density cement slurry

[0065] The cement slurry formula is as follows in parts by mass: 100 parts of G-grade oil well cement, 60 parts of surface glaze sealing hollow glass microspheres (A), 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 2 parts of dispersant, 3 parts of second suspension stabilizer, 5 parts of high-temperature fluid loss additive, 2 parts of high-temperature retarder, 1 part of defoaming agent, and 80 parts of tap water.

[0066] The oil well cement, surface glaze sealing hollow glass microspheres, high temperature strength anti-decay material, high temperature anti-cracking material and dispersant are weighed in proportion and mixed evenly to prepare a dry mix; the high temperature retarder, high temperature fluid loss additive, suspension stabilizer, defoamer and tap water are mixed evenly to prepare a wet mix; the dry mix is ​​evenly introduced into the wet mix at a speed of 4000±200r / min, and after the dry mix is ​​completely wetted, stirring is continued for 35s to obtain a high temperature, high strength and low density cement slurry.

[0067] The density of cement slurry is 1.30×10 3 kg / m 3 , the experimental results are shown in Appendix 1.

[0068] Example 2

[0069] The first step is the preparation of surface glaze-sealed hollow glass microspheres

[0070] (1) Pretreatment of hollow glass microspheres

[0071] 38.7 parts of hollow glass microspheres were added to 150 parts of anhydrous ethanol solution and stirred at 150 r / min for 30 minutes; 3.1 parts of KH570 were added dropwise at 60°C within 1 hour; then cooled to room temperature and separated using a high-speed centrifuge. The separated material was rinsed with deionized water until neutral and dried to obtain hollow glass microspheres with surface grafted silane coupling agent for use.

[0072] Hollow glass microspheres with a surface grafted silane coupling agent and 10.8 parts of FA are added to a certain amount of deionized water, mixed, and stirred evenly at 120 r / min; the pH value of the suspension is adjusted to 7; deionized water is added to make the solid content of the suspension reach 15wt%; Ar is introduced, and the temperature is raised to 50°C; APS is added, kept warm, stirred, and reacted for 6 hours; Ar is turned off, PBQ is added, and stirring is continued for 20 minutes; cooling, washing with clean water, and spray drying are carried out to obtain hollow glass microspheres with a surface grafted chelating group.

[0073] (2) Preparation of glaze slurry

[0074] Weigh a certain mass of deionized water and 1.3 parts of porcelain clay, and stir them at 300 r / min; weigh 46.5 parts of glaze sealing material, of which 30.8% is nano-dolomite powder, 30.8% is nano-zircon powder, 15.4% is nano-sodium potassium stone powder, and 23% is nano-strontium carbonate powder, and stir them at 1500 r / min; weigh 0.95 parts of sodium tannate, and stir them at 1500 r / min; add deionized water so that the content of nano-scale glaze sealing material in the suspension reaches 70wt%, and stir them at 1500 r / min to obtain glaze sealing slurry.

[0075] (3) Preparation of surface glaze-sealed hollow glass microspheres

[0076] ①Use the spraying method to evenly spray the prepared glaze slurry onto the pre-treated hollow glass beads to ensure that the glaze slurry is fully infiltrated and wrapped on the surface of the hollow glass beads.

[0077] ② Move the hollow glass microspheres with the sealing slurry into a vacuum oven, dry them at 60°C for 1 day and 110°C for 2 days, and sieve them; place them in a high-temperature electric furnace and fire them at 1000°C for 8 hours; cool them, sieve them, and the resulting powder material is the surface glaze-sealed hollow glass microspheres (B).

[0078] The second step is the preparation of high temperature resistant, high strength and low density cement slurry system

[0079] The cement slurry formula, in parts by mass, is as follows: 100 parts of Grade G oil well cement, 40 parts of hollow glass microspheres (B) for surface glaze sealing, 15 parts of high-temperature strength anti-fading material, 4 parts of high-temperature anti-cracking material, 1.5 parts of dispersant, 2 parts of secondary suspension stabilizer, 5 parts of high-temperature fluid loss additive, 2.2 parts of high-temperature retarder, 1 part of defoamer, and 73 parts of tap water. The preparation process of the high-temperature, high-strength, low-density cement slurry in Example 2 of the present invention is similar to that of Example 1.

[0080] The density of cement slurry is 1.40×10 3 kg / m 3 , the experimental results are shown in Appendix 1.

[0081] Example 3

[0082] The first step is the preparation of surface glaze-sealed hollow glass microspheres

[0083] (1) Pretreatment of hollow glass microspheres

[0084] 36.5 parts of hollow glass microspheres were added to 145 parts of anhydrous ethanol solution, stirred at 150 r / min for 30 minutes, and 2.9 parts of KH570 were added dropwise at 60°C within 1 hour. After cooling to room temperature, the mixture was separated using a high-speed centrifuge, and the separated material was rinsed with deionized water until neutral, and dried to obtain hollow glass microspheres with surface grafted silane coupling agent for use.

[0085] Hollow glass microspheres with a surface grafted silane coupling agent, 5 parts of IA and 4.2 parts of FA are added to a certain amount of deionized water, mixed, and stirred evenly at 120 r / min; the pH value of the suspension is adjusted to 7; deionized water is added to make the solid content of the suspension reach 15wt%; Ar is introduced, and the temperature is raised to 50°C; APS is added, and the temperature is kept and stirred for 6 hours; Ar is turned off, PBQ is added, and stirring is continued for 20 minutes; cooling, washing with clean water, and spray drying are prepared to obtain hollow glass microspheres with a surface grafted chelating group.

[0086] (2) Preparation of glaze slurry

[0087] Weigh a certain mass of deionized water and 1.5 parts of porcelain clay, and stir them at 300 r / min; weigh 50.3 parts of glaze sealing material, of which 16.7% is nano-dolomite powder, 33.3% is nano-zircon powder, 33.3% is nano-sodium potassium stone powder, and 16.7% is nano-strontium carbonate powder, and stir them at 1500 r / min; weigh 1 part of sodium tetraphosphate, and stir them at 1500 r / min; add deionized water so that the content of nano-scale glaze sealing material in the suspension reaches 70wt%, and stir them at 1500 r / min to obtain glaze sealing slurry.

[0088] (3) Preparation of surface glaze-sealed hollow glass microspheres

[0089] ①Use the spraying method to evenly spray the prepared glaze slurry onto the pre-treated hollow glass beads to ensure that the glaze slurry is fully infiltrated and wrapped on the surface of the hollow glass beads.

[0090] ② Move the hollow glass microspheres with the sealing slurry into a vacuum oven, dry them at 60°C for 1 day and 110°C for 2 days, and sieve them; place them in a high-temperature electric furnace and fire them at 1000°C for 10 hours; cool them, sieve them, and the powder material obtained is the surface glaze sealing hollow glass microspheres (C).

[0091] The second step is the preparation of high temperature, high strength and low density cement slurry

[0092] The cement slurry formula, by weight percentage, is as follows: 100 parts G-grade oil well cement, 29 parts surface glaze hollow glass microspheres (C), 15 parts high-temperature strength anti-fade material, 4 parts high-temperature anti-cracking material, 1.2 parts dispersant, 2 parts suspension stabilizer, 4.3 parts high-temperature fluid loss additive, 2.5 parts high-temperature retarder, 1 part defoamer, and 67 parts tap water. The preparation process for the high-temperature, high-strength, low-density cement slurry in Example 3 of the present invention is similar to that of Example 1.

[0093] The density of cement slurry is 1.50×10 3 kg / m 3 , the experimental results are shown in Appendix 1.

[0094] Comparative Example 1

[0095] Commercially available hollow glass microspheres (D).

[0096] The cement slurry formula is as follows in parts by mass: 100 parts of G-grade oil well cement, 40 parts of hollow glass microspheres, 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 2 parts of dispersant, 3 parts of second suspension stabilizer, 5 parts of high-temperature fluid loss additive, 2 parts of high-temperature retarder, 1 part of defoaming agent, and 72 parts of tap water.

[0097] The density of cement slurry is 1.30×10 3 kg / m 3, the experimental results are shown in Appendix 1.

[0098] Comparative Example 2

[0099] Commercially available hollow glass microspheres (D).

[0100] The cement slurry formula is as follows in percentage by weight: 100 parts of oil well cement, 28 parts of hollow glass microspheres, 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 1.5 parts of dispersant, 2 parts of second suspension stabilizer, 5 parts of high-temperature fluid loss additive, 2 parts of high-temperature retarder, 1 part of defoaming agent, and 66 parts of tap water.

[0101] The density of cement slurry is 1.40×10 3 kg / m 3 , the experimental results are shown in Appendix 1.

[0102] Comparative Example 3

[0103] Commercially available hollow glass microspheres (D).

[0104] The cement slurry formula is as follows in percentage by weight: 100 parts of oil well cement, 19 parts of hollow glass microspheres, 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 1.5 parts of dispersant, 2 parts of second suspension stabilizer, 4.3 parts of high-temperature fluid loss additive, 2 parts of high-temperature retarder, 1 part of defoaming agent, and 61 parts of tap water.

[0105] The density of cement slurry is 1.50×10 3 kg / m 3 , the experimental results are shown in Appendix 1.

[0106] Experiments were conducted in accordance with the national standard GB / T 19139-2012 "Test Methods for Oil Well Cement" to evaluate the compressive strength, thickening, water loss, free liquid, density difference, and rheological properties of the high-strength, low-density cement slurry system of the present invention.

[0107] The main experimental instruments include: 30-60 type wall-edge agitator, 8240 type high-temperature and high-pressure thickener, 7357 type high-temperature and high-pressure curing kettle, all products of CHANDLER Company of the United States; 35SA type rotational viscometer, Fann Company of the United States; HH-420 type constant temperature digital display water tank, Changzhou Yineng Experimental Instrument Factory.

[0108] Table 1 Various properties test table of cement slurry system of embodiment and comparative example

[0109]

[0110]

[0111] From the data in Table 1, we can see that the high-temperature, high-strength, low-density cement slurry system prepared based on glaze-sealed hollow glass microspheres has a density of 1.30-1.50 g / cm 3 The range is adjusted according to the construction needs, and the fluidity is greater than 20cm; when the circulation temperature is 160℃, the initial viscosity of Example 1 is 15Bc, and the thickening time is 309min ( Figure 1 ), Example 2 initial thickening 17Bc, thickening time 300min ( Figure 2 ), Example 3 initial thickening 13Bc, thickening time 317min ( Figure 3 ), the thickening curves of all examples are normal, without abnormal gelation such as "core"; under the experimental conditions of 93℃×6.9MPa, the water loss of Example 1 Q 30 92mL, the water loss Q of Example 2 30 56mL, Example 3 water loss Q 30 The volume of the liquid was 44 mL, and no gas penetration occurred during the experiment. At the same time, the rheological parameters of each embodiment were n>0.80, k≤0.76 Pa.s n .

[0112] The sedimentation stability evaluation showed that the difference in density between the upper and lower cement slurries after standing at 93°C for 2 hours with a 3% addition of the suspension stabilizer in Example 1 was 0.02 g / cm 3 After standing at 180℃ for 24 hours, the density difference between the upper and lower parts of the cement stone was 0.038g / cm 3 Example 2 Suspension stabilizer was added at 2%, and the upper and lower density difference of the cement slurry was 0 after standing at 93 ° C for 2h, and the upper and lower density difference of the cement stone was 0.024g / cm after standing at 180 ° C for 24h. 3 Example 3 Suspension stabilizer was added in an amount of 2%, and the upper and lower density difference of the cement slurry was 0 after standing at 93 ° C for 2h, and the upper and lower density difference of the cement stone was measured after standing at 180 ° C for 24h. It was 0.014g / cm 3 ; The free liquid in each embodiment is 0.

[0113] On the basis that all properties meet the requirements of cementing and well cementing construction, the mechanical properties of the high-temperature resistant, high-strength, low-density cement slurry in the present invention are evaluated. As can be seen from Table 1, the compressive strength of the high-temperature, high-strength, low-density cement slurry prepared based on glaze-sealed hollow glass microspheres under high-temperature working conditions increases with the extension of curing time; under the same curing conditions, the compressive strength increases with the increase of cement slurry density. The glaze-sealed hollow glass microspheres (A) used in Example 1 contain 40.5 parts of hollow glass microspheres, 3.3 parts of silane coupling agent, 10.8 parts of active monomers containing chelating groups, and 44.8 parts of glaze sealing materials. After mixing them according to 100 parts of oil well cement, 60 parts of glaze sealing hollow glass microspheres (A), 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 2 parts of dispersant, 3 parts of second suspension stabilizer, 5 parts of high-temperature water loss reducer, 2 parts of high-temperature retarder, 1 part of defoaming agent, and 80 parts of tap water, the obtained cement slurry has a density of 1.30g / cm 3 , the compressive strength at 180℃ for 24h is 17.3MPa, and that for 48h is 20.1MPa, which is an increase of 16.2%. The glaze sealing hollow glass microspheres (B) used in Example 2 contain 38.5 parts of hollow glass microspheres, 3.1 parts of silane coupling agent, 10.8 parts of active monomer containing chelating group, and 46.5 parts of glaze sealing material. After mixing them according to 100 parts of oil well cement, 40 parts of surface-modified hollow glass microspheres (B), 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 1.5 parts of dispersant, 2 parts of second suspension stabilizer, 5 parts of high-temperature fluid loss agent, 2.2 parts of high-temperature retarder, 1 part of defoaming agent, and 73 parts of tap water, the obtained cement slurry density is 1.40g / cm 3 The compressive strength is 19.6MPa after curing at 180℃ for 24h and reaches 23.3MPa after 48h.

[0114] In the above-mentioned embodiments, the glazed hollow glass microspheres have a high operating temperature range and are less susceptible to the high pH environment generated by cement hydration under high-temperature conditions. They also exhibit strong bonding with silicate oil-well cement during the high-temperature curing process of the cement slurry, reducing the risk of cracks and defects between the microspheres and the cement matrix. When mixed with oil-well cement, admixtures, and additives to form a high-temperature, high-strength, low-density cement slurry, the high-temperature strength-reduction-resistant material composed of composite silica powder and crystalline silica powder can optimize the silicon-calcium ratio (Si / Ca) of the cement slurry system, adjust cement hydration products, and prevent the decline of cement matrix strength. Furthermore, it achieves a dense packing of the cement slurry's solid-phase particles, ensuring the high-temperature compressive strength of the cement paste. In the high-temperature anti-cracking material composed of inorganic short-cut fibers and styrene-butadiene rubber powder, the inorganic short-cut fibers have strong temperature resistance and can be inserted into cement particles and hydration products, playing a "tensioning" role to inhibit the high-temperature deformation of the cement matrix; the polymer styrene-butadiene rubber powder has strong deformation ability under high-temperature conditions and has certain adhesion. It can fill a layer of flexible polymer film between cement particles or between cement particles and glaze-sealed hollow glass beads to reduce the damage of cement stone caused by external mechanical shock or thermal shock.

[0115] Commercially available hollow glass microspheres were used as a comparative example. Under the same experimental conditions, the thickening time of comparative example 1 was 325 min ( Figure 4 ), water loss Q 30 The density difference of cement slurry is 0.06 g / cm after standing at 93℃ for 2 hours. 3 , free liquid 0.36%; compared with Example 1, the water loss Q 30 The increase was 14mL, and the rheological properties were not much different. The compressive strength after curing at 180℃ for 24h decreased by 56.6%, and the compressive strength after 48h decreased by 71.1%, respectively, showing obvious attenuation. Compared with Example 2, the thickening time of Comparative Example 2 was extended by 23min, and the water loss Q 30 The increase of 12mL, the compressive strength of 24h and 48h under 180℃ curing conditions decreased by 48.5% and 63.1% respectively, and the strength was attenuated; at the same time, free liquid appeared during the static process of cement slurry. Compared with Example 3, the thickening time of Comparative Example 3 was extended by 5min, and the water loss Q 30 An increase of 6 mL reduced the compressive strength by 35.5% and 57.9% after 24 and 48 hours of curing at 180°C, respectively. The above experimental data indicate that low-density cement slurry prepared with unmodified commercially available hollow glass microspheres exhibits low compressive strength at 180°C, with significant attenuation.

[0116] The experimental results show that under the same density conditions, surface glaze treatment is beneficial to improving the micro-beads' resistance to high-alkalinity corrosion under high-temperature conditions, enhancing the physical filling between the micro-beads and the cement matrix, and inhibiting the generation of micro-cracks, thereby improving the compressive strength of low-density cement slurry. At the same time, it also has a positive effect on controlling water loss and improving sedimentation stability.

[0117] Therefore, the surface glaze-sealed glass microspheres provided by the present invention and the high-temperature, high-strength, low-density cement slurry prepared based on the surface glaze-sealed glass microspheres can obtain an adjustable density (1.30-1.50 g / cm 3 ) is a high-performance, low-density cementing fluid with low water loss, excellent sedimentation and fluidity, and can meet the needs of cementing and cementing operations. It also exhibits high compressive strength with no attenuation even at high temperatures of 180°C. This cement slurry provides strong technical support for cementing operations in complex deep and ultra-deep wells with low formation pressure bearing capacity, narrow safe density windows, and strict requirements for pay zone protection.

[0118] In embodiments 1 to 3 of the present invention, hollow glass microspheres with surface glaze are used as lightening agents, and the density of the cement slurry is adjusted by utilizing the hollow and low-density characteristics thereof; a molecular chain rich in adsorption groups (-COOH) is grafted onto the surface of the hollow glass microspheres by utilizing a silane coupling agent, and the adhesion effect of the glaze slurry on the surface of the hollow glass microspheres is improved through the adsorption and chelation between -COOH and heavy metal ions in the nano-inorganic mineral powder; a small molecule organic acid salt is used as an auxiliary agent to assist the uniform coating and deep penetration of the glaze material on the surface of the hollow glass microspheres. On this basis, continuous drying at variable temperatures is performed to avoid cracking of the glaze slurry on the surface of the hollow glass microspheres due to rapid escape of water or uneven escape rate; and finally, hollow glass microspheres with a layer of heat-resistant and corrosion-resistant glaze layer on the surface are obtained by low-temperature firing, thereby improving their macroscopic mechanical properties and the ability to resist corrosion from cement hydration products, formation fluids, etc., and improving the structural integrity and compressive strength of low-density cement stone under high-temperature working conditions at the bottom of the well.

[0119] High-temperature strength anti-decay materials are composed of different types of silica fume. On the one hand, the small particle size and good workability are used to improve the particle grading of the system, physically fill the capillary channels and microcracks in the cement slurry system, and achieve denser stacking; on the other hand, by adjusting the silicon-calcium ratio (Si / Ca) of the cement slurry system and optimizing the hydration products, the development defects of cement stone under high-temperature working conditions are compensated, the microstructure and submicrostructure of cement stone are improved, and the mechanical properties are enhanced.

[0120] The whiskers and chopped fibers in high-temperature anti-cracking materials can be inserted into cement particles and hydration products, or aggregate and overlap on the interstices between these materials to form a skeleton structure, acting as a "reinforcement" and toughening agent, thereby inhibiting high-temperature deformation of the cement matrix. The styrene-butadiene rubber powder has good thermal stability, a certain degree of flexibility, and adhesion. It can be filled between cement particles or between cement particles and the hollow glass microspheres sealed on the surface, forming a polymer network that reduces damage to the cement stone caused by external mechanical or thermal shock. Furthermore, the presence of whiskers can provide condensation centers for the formation of early hydration products of cement, promoting the nucleation and growth of hydration product crystals, accelerating the cement hydration process and the development of early strength.

[0121] Other admixtures used in high-temperature, high-strength, low-density cement slurry, such as high-temperature retarders, high-temperature fluid loss additives, suspension stabilizers, dispersants and defoamers, are all mature products. The relevant mechanisms and properties are well known to those skilled in the art and will not be described in detail.

[0122] The density of the high temperature, high strength and low density cement slurry prepared in Examples 1 to 3 of the present invention is adjustable (1.30 to 1.50 g / cm 3 ), 180℃ high temperature 24h compressive strength greater than 18MPa, 48h compressive strength greater than 25MPa, low API water loss, good rheological properties, free liquid is 0, density difference less than 0.05g / cm 3 It provides strong technical support for reducing the risk of lost circulation during cementing construction and ensuring the exploration and development benefits of difficult-to-use reserves and unconventional oil and gas resources in complex deep wells and ultra-deep wells.

[0123] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing surface glaze-sealed hollow glass microspheres, characterized in that: The raw material composition of the surface glaze sealing hollow glass microspheres includes, by weight: 36.5 to 40.5 parts of hollow glass microspheres, 2.9 to 3.3 parts of silane coupling agent, 9.2 to 11 parts of active monomer containing chelating group, 44.8 to 50.3 parts of nano-scale glaze sealing material, 0.9 to 1 part of auxiliary agent, and 1.3 to 1.5 parts of first suspension stabilizer; The preparation method comprises: adding the hollow glass microspheres into an anhydrous ethanol solution, and dropwise adding a silane coupling agent, separating, rinsing, and drying to obtain hollow glass microspheres with the silane coupling agent grafted on the surface; The hollow glass microspheres with the surface grafted silane coupling agent and the active monomer containing the chelate group are added into deionized water and mixed, an initiator is added to react, a polymerization inhibitor is added, and the hollow glass microspheres with the surface grafted chelate group are prepared after washing and drying; Adding the first suspension stabilizer, the nano-scale glaze sealing material and the auxiliary agent into deionized water and stirring evenly to prepare a glaze sealing slurry; The hollow glass microbeads with grafted chelating groups on the surface are sprayed with glaze slurry, vacuum dried and fired to obtain the hollow glass microbeads with surface glaze sealing.

2. The method according to claim 1, characterized in that The compressive strength of the hollow glass microspheres is 12,000 psi.

3. The method according to claim 1, characterized in that The silane coupling agent is γ-methacryloxypropyltrimethoxysilane.

4. The method according to claim 1, wherein The active monomer containing a chelating group is itaconic acid and / or fumaric acid.

5. The method according to claim 1, wherein The nano-grade glaze sealing material comprises, by mass, 16.7 to 33.3 parts of 300 to 500 nm nano-dolomite, 25 to 33.3 parts of 100 to 500 nm nano-zircon powder, 15.4 to 33.3 parts of 400 to 1000 nm nano-sodium potassium stone powder, and 16.7 to 23.1 parts of 50 to 300 nm nano-strontium carbonate powder.

6. The method according to claim 1, characterized in that The auxiliary agent is at least one of the following: sodium tripolyphosphate, sodium tetraphosphate, and sodium tannate.

7. The method according to claim 1, characterized in that The first suspension stabilizer is bentonite and / or china clay.

8. The method according to any one of claims 1 to 7, characterized in that The preparation method specifically comprises: The hollow glass microspheres are added to an anhydrous ethanol solution, and a silane coupling agent is added dropwise at 60-70° C. within 1 hour; the mixture is cooled to room temperature, separated using a high-speed centrifuge, and the separated product is washed with deionized water until neutral, and dried to obtain hollow glass microspheres with the silane coupling agent grafted on the surface; The hollow glass microspheres with a surface grafted silane coupling agent and an active monomer containing a chelating group are added to deionized water, mixed, stirred evenly, adjusted to a neutral pH value, and supplemented with deionized water so that the solid content of the suspension reaches 15 wt %; a protective gas is introduced, the temperature is raised to 50° C., an initiator is added to react, and the temperature is kept and stirred for 6 to 8 hours; the protective gas is turned off, an inhibitor is added, stirred, and then cooled to room temperature, washed with clean water, and spray-dried to obtain hollow glass microspheres with a surface grafted chelating group; Adding the first suspension stabilizer, the nano-scale glaze sealing material, and the auxiliary agent into deionized water, replenishing the deionized water so that the content of the nano-scale glaze sealing material in the suspension reaches 70 wt %, and stirring evenly to prepare a glaze sealing slurry; The sealing slurry is evenly sprayed onto the hollow glass microspheres with chelating groups grafted onto the surface by a spraying method; dried in a vacuum oven at 60°C for 1 day and at 110°C for 2 days, and sieved; fired in a high-temperature electric furnace at 800-1200°C for 8-10 hours, cooled and sieved to obtain a powder material as the surface glaze sealing hollow glass microspheres.

9. A hollow glass microsphere with surface glaze, characterized in that: The hollow glass microspheres are prepared according to the method for preparing surface glaze-sealed hollow glass microspheres according to any one of claims 1 to 8.

10. A high-temperature, high-strength, low-density cement slurry, characterized in that: The raw material composition of the high-strength, low-density cement slurry includes, in parts by mass: 100 parts of G-grade oil well cement, 29 to 60 parts of the surface glaze-sealed hollow glass microspheres described in claim 9, 15 parts of high-temperature strength anti-decay material, 4 parts of high-temperature anti-cracking material, 2 to 3 parts of a second suspension stabilizer, 1.2 to 2 parts of a dispersant, 4.3 to 5 parts of a high-temperature fluid loss additive, 2 to 2.5 parts of a high-temperature retarder, 1 part of a defoaming agent, and 67 to 80 parts of tap water.

11. The high-temperature, high-strength, low-density cement slurry according to claim 10, characterized in that: The high-temperature strength anti-fading material is prepared by compounding 325-mesh composite silicon micropowder and 1500-mesh crystalline silicon micropowder in a mass ratio of 5:

1.

12. The high-temperature, high-strength, low-density cement slurry according to claim 10 or 11, characterized in that: The high-temperature anti-cracking material comprises, by mass, 10 parts of 1-3 mm calcium sulfate whiskers, 30 parts of 2-4 mm basalt fibers, 20 parts of 1-3 mm aluminum oxide whiskers, and 40 parts of styrene-butadiene rubber powder.

13. Use of the high-temperature, high-strength, low-density cement slurry according to any one of claims 10 to 12 in well completion and cementing.

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