Lightening material based on high-strength low-density cement paste system

Abstract

The invention discloses a lightening material based on a high-strength low-density cement slurry system, and belongs to the technical field of oilfield chemistry. The preparation method of the lightweight material comprises the following steps: compounding waste glass and a reinforcing material to prepare reinforced foam glass particles; then carrying out double-layer coating modification on the surfaces of the enhanced foam glass particles to obtain modified foam glass particles; and respectively dissolving methyl alkenyl polyoxyethylene ether, alkyl glycoside, hydroxypropyl methyl cellulose and nano silicon dioxide in deionized water, adding the modified foam glass particles, and stirring to prepare a pre-slurry solution, thereby obtaining the lightweight material based on the high-strength low-density cement slurry system. The lightening material based on the high-strength low-density cement paste system has relatively low density and good compressive strength.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and in particular relates to a lightening material based on a high-strength and low-density cement slurry system. Background Art

[0002] In the process of oil field development, cementing operation is a crucial link. The main purpose of cementing is to isolate oil, gas and water layers, prevent fluids from crossing between layers, protect oil layers, and provide good wellbore conditions for subsequent mining operations. As a key material used in cementing operations, the performance of cement slurry directly affects the quality of cementing. Traditional cement slurry usually has a high density, however, it can cause serious problems under some special geological conditions. For example, when cementing in low-pressure and leaky formations, high-density cement slurry will generate a large liquid column pressure. When this pressure exceeds the fracture pressure of the formation, it will cause the formation to be compressed and leaked, and a large amount of cement slurry will be lost, which will not only cause a waste of cementing materials and increase operating costs, but also seriously affect the quality of cementing.

[0003] In order to avoid leaking formations, reducing the density of cement slurry is an effective method. However, simply reducing the density of cement slurry will bring new problems, namely insufficient strength and unstable strength development. Under low-density conditions, the solid content in cement slurry is relatively reduced, the distance between cement particles increases, and the degree and speed of hydration reaction are affected, making it difficult for cement stone to reach sufficient strength after solidification, and unable to effectively isolate the formation and support the casing. Moreover, due to the instability of the hydration reaction, the strength development of cement stone may fluctuate, and the strength growth is inconsistent in different time periods, which is very unfavorable for long-term cementing effects. During the production process of oil wells, with changes in downhole pressure and temperature, insufficient and unstable cement stone may crack and be damaged, leading to cementing failure.

[0004] At present, there are some lightening materials for reducing cement slurry density on the market, such as perlite, fly ash and other materials, which can reduce the density of cement slurry to a certain extent, but it is difficult to ensure that the cement slurry has sufficient strength at low density. Therefore, the present invention develops a lightening material based on a high-strength and low-density cement slurry system to solve the technical problems in the prior art that during cementing operations, the cement slurry density is too high and easy to leak out of the formation, while the strength is insufficient and the development is unstable at low density. Summary of the invention

[0005] The purpose of the present invention is to provide a lightening material based on a high-strength and low-density cement slurry system to solve the technical problems in the prior art of cementing operations, that is, the cement slurry density is too high and it is easy to leak out the formation, while the strength is insufficient and the development is unstable under low density.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A lightening material based on a high-strength and low-density cement slurry system, and its preparation method includes the following steps: (1) Prepare enhanced foam glass particles by compounding waste glass, special glass, slag, reinforcing fibers and nano-montmorillonite; (2) Modify the surface of the enhanced foam glass particles by double-layer coating to obtain modified foam glass particles; (3) Dissolve methallyl polyoxyethylene ether, alkyl glycoside, hydroxypropyl methylcellulose and nano-silica in deionized water respectively, add the modified foam glass particles, and stir to prepare a pre-slurry liquid to obtain a lightening material based on a high-strength and low-density cement slurry system.

[0007] Preferably, in step (3), the mass ratio of methallyl polyoxyethylene ether, alkyl glycoside, hydroxypropyl methylcellulose, nano-silica, modified foam glass particles and deionized water is 0.6-1:0.1-0.3:0.1-0.3:1-2:35-45:40-50, the stirring speed is 30-60 rpm, and the time is 10-15 min.

[0008] For the lightening material based on the high-strength and low-density cement slurry system, step (1) includes the following process: S1. After cleaning the waste glass and special glass, break them respectively, and then use ball milling to obtain waste glass powder and special glass powder; perform magnetic separation and grinding on the slag to obtain micro-slag; S2. Mix the waste glass powder, special glass powder and slag powder, stir, add a foaming agent and a first foam stabilizer, continue to stir and mix evenly, then add reinforcing fibers and nano-montmorillonite in sequence, and stir while adding to obtain an enhanced mixed powder; S3. Put the enhanced mixed powder into a mold, perform initial heating, decomposition of the foaming agent, addition of a second foam stabilizer in sequence, foaming, and annealing to obtain a foam glass block, break it, and screen it to obtain enhanced foam glass particles.

[0009] Preferably, in S1, the crushing particle size is less than 1 mm, the particle sizes of the waste glass powder, special glass powder and micro-slag are 50-200 μm, the slag is blast furnace slag, and the special glass is borate glass.

[0010] Preferably, in S2, the stirring speed is 300 - 500 r / min, the stirring time is 15 - 30 min, continue stirring for 10 - 20 min, the stirring speed when adding reinforcing fibers is 200 - 300 r / min, the stirring time is 20 - 30 min, the stirring speed when adding nano - montmorillonite is 300 - 500 r / min, the stirring time is 15 - 30 min, the reinforcing fibers are one or more of glass fibers, carbon fibers and basalt fibers, and the fiber length is 3 - 6 mm; the mass ratio of waste glass powder, special glass powder, micro - slag, reinforcing fibers, nano - montmorillonite, foaming agent and foam stabilizer 1 is 100:10 - 20:20 - 30:2 - 6:1 - 2.5:4 - 6:2; the waste glass is bottle jars or construction waste glass, the special glass is borate glass, the foaming agent is obtained by mixing calcium carbonate and silicon carbide in a mass ratio of 4 - 5:1 - 2, the foam stabilizer 1 is obtained by mixing boric acid and borax, the foam stabilizer 2 is sodium phosphate, and the mass ratio of boric acid, borax and sodium phosphate is 1.5:0.5:0.5.

[0011] Preferably, in S3, the loading height is 2 / 3 - 3 / 4 of the mold height, the heating rate in the initial heating stage of heat - induced foaming is 5 - 10 °C / min, heat up to 300 - 400 °C, and the heat - preservation time is 10 - 20 min; the heating rate in the foaming agent decomposition stage is 2 - 5 °C / min, heat up to 600 - 700 °C, and the heat - preservation time is 15 - 30 min; the heating rate in the foaming stage is 3 - 5 °C / min, heat up to 800 - 950 °C, and the heat - preservation time is 10 - 30 min; the cooling rate in the initial annealing stage is 1 - 5 °C / min, cool down to 400 - 500 °C, and the heat - preservation time is 2 - 4 h, the cooling rate in the post - annealing stage is 5 - 10 °C / h, cool down to room temperature, and the temperature should drop evenly throughout the annealing process to avoid cracking of the foam glass due to too rapid temperature changes; the particle size for screening is 1 - 3 mm.

[0012] The lightweight material based on the high - strength and low - density cement slurry system, step (2) includes the following process: Q1. Clean the enhanced foam glass particles, dry them to constant weight, soak them in an aluminum dihydrogen phosphate solution, take them out, drain, and dry and cure to obtain phosphate - coated foam glass particles; Q2. Add the phosphate - coated foam glass particles into deionized water containing a dispersant, stir evenly to obtain a suspension, and under stirring, add the hybrid emulsion into the foam glass particle suspension, stir and react, filter, and dry to obtain modified foam glass particles.

[0013] Preferably, in Q1, the concentration of the aluminum dihydrogen phosphate solution is 10 - 20 wt%, the drying temperature is 105 - 110 °C, the soaking time is 1 - 2 h, the drying and curing temperature is 150 - 200 °C, and the drying and curing time is 2 - 4 h.

[0014] Preferably, the hybrid emulsion in Q2 is obtained by adding nano-montmorillonite modified by 0.8-1.5 wt% of KH-550 silane coupling agent to the composite emulsion and performing ultrasonic dispersion. The volume ratio of the composite emulsion to the nano-montmorillonite is 100:3-4; the composite emulsion is prepared from an acrylic emulsion, a vinyl acetate emulsion, a polyurethane emulsion, a styrene-acrylic emulsion, ZW-2 and silica fume according to the dosage ratio of 40-50 mL: 35-40 mL: 25-30 mL: 10-12 mL: 0.3-0.5 g: 0.35-0.6 g; the stirring reaction time is 1-2 h, and the drying temperature is 60-80 °C.

[0015] Through the mutual cooperation of the components of the hybrid emulsion, modified foam glass particles with better comprehensive performance are prepared. The acrylic emulsion has good weather resistance and water resistance, the vinyl acetate emulsion has good adhesiveness, the polyurethane emulsion has high elasticity and wear resistance, the styrene-acrylic emulsion has excellent chemical resistance, and the nano-montmorillonite can interact with the polymer molecules in the composite emulsion to enhance the stability and adhesiveness of the emulsion, thereby improving the interfacial bonding force between the modified foam glass particles and the cement slurry.

[0016] The present application provides a lightening material based on a high-strength and low-density cement slurry system, and adopts the following technical solution: the lightening material based on the high-strength and low-density cement slurry system is prepared according to the preparation method of the lightening material based on the high-strength and low-density cement slurry system described in any one of the above.

[0017] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows: 1. By fully utilizing waste glass for multi-stage material compounding and surface coating modification, the present invention prepares modified foam glass particles. As a component of the cement slurry system, it not only realizes the recycling of waste, reduces the environmental pollution caused by waste glass, and reduces the raw material cost, but also ensures the strength of the material while reducing the density, so as to meet the requirements of the high-strength and low-density cement slurry system.

[0018] 2. The present invention prepares foamed glass particles by compounding multi-level materials such as waste glass powder, borate glass powder, microslag, reinforcing fibers, and nano-montmorillonite, and through their synergistic effects. The fibers form a network structure inside the foam glass, which can effectively prevent crack propagation, enhance the compressive and impact resistance of the particles, and thus enhance the mechanical properties of the cement slurry system. The slag and nano-montmorillonite particles can fill the tiny pores in the material, further improving the density of the material. In addition, the optimized foaming and foam-stabilizing system can generate uniformly fine bubbles during the heating process and stabilize the morphology of the bubbles, preventing the bubbles from bursting and merging, so as to form a uniform porous structure inside the foam glass. This not only reduces the density of the material but also endows the material with good mechanical properties, making it more suitable for application in high-strength and low-density cement slurry systems.

[0019] 3. The present invention modifies the surface of the foamed glass particles by phosphate coating and hybrid emulsion modification respectively. The modified material can not only protect the internal structure but also better combine with the cement slurry matrix, thereby enhancing the mechanical properties of the cement slurry system. Among them, the phosphate coating layer can play an isolation role, reducing the direct contact between the foamed glass particles and the external environment, improving the chemical stability of the particles, and thus ensuring the long-term stability of the performance of the cement slurry system. The hybrid emulsion is composed of acrylic emulsion, vinyl acetate emulsion, polyurethane emulsion, styrene-acrylic emulsion, and nano-montmorillonite, and the components act synergistically to improve the overall performance of the cement slurry system. Detailed implementation manners

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Example 1:

[0022] This example provides a preparation method of a lightening material based on a high-strength and low-density cement slurry system, including the following steps: (1) Prepare enhanced foamed glass particles by compounding waste glass, special glass, slag, reinforcing fibers, and nano-montmorillonite; (2) Modify the surface of the enhanced foamed glass particles by double-layer coating to obtain modified foamed glass particles; (3) Dissolve 6 g of methyl vinyl polyoxyethylene ether, 1 g of alkyl glycoside, 1 g of hydroxypropyl methylcellulose, and 10 - 20 g of nano-silica in 400 g of deionized water respectively. Add 350 g of modified foam glass particles and stir at a speed of 30 rpm for 10 min to prepare a pre-slurry, obtaining a lightening material for a high-strength and low-density cement slurry system.

[0023] Among them, the preparation method of the lightening material for the high-strength and low-density cement slurry system, step (1) includes the following process: S1. After cleaning the waste glass and borate glass, crush them to a particle size less than 1 mm respectively, and then ball-mill them to obtain waste glass powder and borate glass powder; perform magnetic separation on blast furnace slag and grind it to obtain micro-slag. S2. Mix 100 g of waste glass powder, 10 g of borate glass powder, and 20 g of slag powder, stir at a speed of 300 r / min for 15 min, add 4 g of calcium carbonate, 1 g of silicon carbide, 1.5 g of boric acid, and 0.5 g of borax, continue to stir for 10 min to mix evenly, then add 2 g of reinforcing fiber and 1 g of nano-montmorillonite in sequence. The reinforcing fiber is glass fiber with a fiber length of 3 mm. Stir while adding. The stirring speed when adding the reinforcing fiber is 200 r / min and the stirring time is 20 min. The stirring speed when adding nano-montmorillonite is 300 r / min and the stirring time is 15 min to obtain an enhanced mixed powder.

[0024] S3. Load the enhanced mixed powder into a mold with a loading height of 2 / 3 of the mold height, and perform initial heating, blowing agent decomposition, add 0.5 g of sodium phosphate, foaming, and annealing in sequence to obtain a foam glass block, crush it, and screen it to a particle size of 1 mm. Among them, the heating rate in the initial heating stage is 10 °C / min, heat up to 300 °C, and the holding time is 10 min; the heating rate in the blowing agent decomposition stage is 5 °C / min, heat up to 600 °C, and the holding time is 15 min; the heating rate in the foaming stage is 5 °C / min, heat up to 800 °C, and the holding time is 10 min; the cooling rate in the initial stage of annealing is 5 °C / min, cool down to 400 °C, and the holding time is 2 h. The cooling rate in the later stage of annealing is 10 °C / h, cool down to room temperature to obtain enhanced foam glass particles.

[0025] Among them, the preparation method of the lightening material for the high-strength and low-density cement slurry system, step (2) includes the following process: Q1. Wash the enhanced foam glass particles, dry them to constant weight at a drying temperature of 105°C for 1 hour of soaking time. Immerse them in a 10wt% aluminum dihydrogen phosphate solution, take them out, drain, and then dry and cure at a temperature of 150°C for 2 hours to obtain phosphate-coated foam glass particles. Q2. Add the phosphate-coated foam glass particles to deionized water containing a dispersant and stir evenly to obtain a suspension. Under stirring, add the hybrid emulsion to the foam glass particle suspension. The hybrid emulsion is obtained by adding nano-montmorillonite modified with 0.8wt% KH-550 silane coupling agent to a composite emulsion and subjecting it to ultrasonic dispersion. The volume ratio of the composite emulsion to nano-montmorillonite is 100:3. The composite emulsion is prepared from an acrylic emulsion, a vinyl acetate emulsion, a polyurethane emulsion, a styrene-acrylic emulsion, ZW-2, and silica fume according to a dosage ratio of 40mL:35mL:25mL:10mL:0.3g:0.35g. Stir and react for 1 hour, filter, and dry at a temperature of 60°C to obtain modified foam glass particles.

[0026] Example 2:

[0027] This example provides a preparation method of a lightening material based on a high-strength low-density cement slurry system, including the following steps: (1) Prepare enhanced foam glass particles by compounding waste glass, special glass, slag, reinforcing fibers, and nano-montmorillonite. (2) Obtain modified foam glass particles by performing double-layer coating modification on the surface of the enhanced foam glass particles. (3) Dissolve 8g of methallyl polyoxyethylene ether, 2g of alkyl glycoside, 2g of hydroxypropyl methylcellulose, and 15g of nano-silica in 450g of deionized water respectively, add 400g of modified foam glass particles, and stir at a speed of 50rpm for 13 minutes to prepare a pre-slurry liquid, thus obtaining a lightening material based on a high-strength low-density cement slurry system.

[0028] Among them, for the preparation method of the lightening material based on the high-strength low-density cement slurry system, step (1) includes the following process: S1. After cleaning the waste glass and borate glass, break them into particles with a particle size less than 1mm respectively, and then use ball milling to obtain waste glass powder and borate glass powder. Perform magnetic separation and grinding on blast furnace slag to obtain fine slag. S2. Mix 100 g of waste glass powder, 15 g of borate glass powder, and 25 g of slag powder, and stir at a speed of 400 r / min for 20 min. Then add 4 g of calcium carbonate, 1.5 g of silicon carbide, 1.5 g of boric acid, and 0.5 g of borax, and continue to stir for 14 min until evenly mixed. Then add 4 g of reinforcing fiber and 1.3 g of nano-montmorillonite in sequence. The reinforcing fiber is basalt fiber with a fiber length of 4 mm. Stir while adding. The stirring speed when adding the reinforcing fiber is 250 r / min, and the stirring time is 25 min. The stirring speed when adding nano-montmorillonite is 400 r / min, and the stirring time is 20 min to obtain the reinforced mixed powder.

[0029] S3. Load the reinforced mixed powder into a mold. The loading height is 3 / 4 of the mold height. Then conduct initial heating, foaming agent decomposition, add 0.5 g of sodium phosphate, foam, and anneal in sequence to obtain a foam glass block. Crush it and sieve with a particle size of 2 mm. Among them, the heating rate in the initial heating stage is 8 °C / min, heat up to 350 °C, and the holding time is 15 min; the heating rate in the foaming agent decomposition stage is 3 °C / min, heat up to 650 °C, and the holding time is 20 min; the heating rate in the foaming stage is 4 °C / min, heat up to 850 °C, and the holding time is 20 min; the cooling rate in the initial stage of annealing is 3 °C / min, cool down to 450 °C, and the holding time is 3 h. The cooling rate in the later stage of annealing is 7 °C / h, cool down to room temperature to obtain the reinforced foam glass particles.

[0030] Among them, the preparation method of the lightening material based on the high-strength and low-density cement slurry system, step (2) includes the following process: Q1. Wash the reinforced foam glass particles and dry them to constant weight at a drying temperature of 108 °C for 1.5 h. Then soak them in a 15 wt% solution of aluminum dihydrogen phosphate, take them out, drain, and dry and cure at a temperature of 170 °C for 3 h to obtain phosphate-coated foam glass particles. Q2. Add the phosphate-coated foam glass particles to deionized water containing a dispersant and stir evenly to obtain a suspension. Under stirring, add the hybrid emulsion to the foam glass particle suspension. The hybrid emulsion is obtained by adding nano-montmorillonite modified by 1.2 wt% of KH-550 silane coupling agent to a composite emulsion and ultrasonic dispersion. The volume ratio of the composite emulsion to nano-montmorillonite is 100:3.5. The composite emulsion is prepared from acrylic emulsion, vinyl acetate emulsion, polyurethane emulsion, styrene-acrylic emulsion, ZW-2, and silica fume according to the dosage ratio of 45 mL:38 mL:28 mL:11 mL:0.4 g:0.5 g. The stirring reaction time is 1.5 h. Filter and dry at a drying temperature of 70 °C to obtain the modified foam glass particles.

[0031] Example 3:

[0032] This example provides a method for preparing a lightening material based on a high-strength and low-density cement slurry system, including the following steps: (1) Prepare enhanced foam glass particles by compounding waste glass, special glass, slag, reinforcing fiber, and nano-montmorillonite. (2) Modify the surface of the enhanced foam glass particles by double-layer coating to obtain modified foam glass particles. (3) Dissolve 10 g of methyl vinyl polyoxyethylene ether, 3 g of alkyl glycoside, 3 g of hydroxypropyl methylcellulose, and 20 g of nano-silica in 500 g of deionized water respectively. Add 450 g of modified foam glass particles and stir at a speed of 60 rpm for 15 min to prepare a pre-slurry liquid, thus obtaining a lightening material based on a high-strength and low-density cement slurry system.

[0033] Among them, the method for preparing the lightening material based on the high-strength and low-density cement slurry system in step (1) includes the following process: S1. After cleaning the waste glass and borate glass, crush them to a particle size less than 1 mm respectively, and then use ball milling to obtain waste glass powder and borate glass powder. Perform magnetic separation and grinding on blast furnace slag to obtain micro-slag. S2. Mix 100 g of waste glass powder, 20 g of borate glass powder, and 30 g of slag powder, and stir at a speed of 500 r / min for 30 min. Add 4 g of calcium carbonate, 2 g of silicon carbide, 1.5 g of boric acid, and 0.5 g of borax, and continue to stir for 20 min to mix evenly. Then add 6 g of reinforcing fiber and 1.5 g of nano-montmorillonite in sequence. The reinforcing fiber is carbon fiber with a fiber length of 6 mm, and stir while adding. The stirring speed when adding the reinforcing fiber is 300 r / min, and the stirring time is 30 min. The stirring speed when adding nano-montmorillonite is 500 r / min, and the stirring time is 30 min to obtain enhanced mixed powder.

[0034] S3. Load the enhanced hybrid powder into a mold with a loading height of 3 / 4 of the mold height. Then, perform initial heating, blowing agent decomposition, add 0.5 g of sodium phosphate, foam, and anneal successively to obtain a foam glass block. Crush it and screen it to a particle size of 3 mm. Among them, the heating rate in the initial heating stage is 5 °C / min, heat up to 400 °C, and the holding time is 20 min; the heating rate in the blowing agent decomposition stage is 2 °C / min, heat up to 700 °C, and the holding time is 30 min; the heating rate in the foaming stage is 3 °C / min, heat up to 950 °C, and the holding time is 30 min; the cooling rate in the initial stage of annealing is 1 °C / min, cool down to 500 °C, and the holding time is 4 h. The cooling rate in the later stage of annealing is 5 °C / h, cool down to room temperature to obtain enhanced foam glass particles.

[0035] Among them, the preparation method of the lightening material based on the high-strength and low-density cement slurry system in step (2) includes the following process: Q1. Wash the enhanced foam glass particles and dry them to a constant weight at a drying temperature of 110 °C for 2 h. Then soak them in a 1.5 wt% aluminum dihydrogen phosphate solution, take them out, drain, and dry and cure at a temperature of 200 °C for 4 h to obtain phosphate-coated foam glass particles. Q2. Add the phosphate-coated foam glass particles to deionized water containing a dispersant and stir evenly to obtain a suspension. Under stirring, add the hybrid emulsion to the foam glass particle suspension. The hybrid emulsion is obtained by adding nano-montmorillonite modified by 20 wt% KH-550 silane coupling agent to a composite emulsion and ultrasonic dispersing. The volume ratio of the composite emulsion to nano-montmorillonite is 100:4. The composite emulsion is prepared from acrylic emulsion, vinyl acetate emulsion, polyurethane emulsion, styrene-acrylic emulsion, ZW-2, and silica fume according to the dosage ratio of 50 mL:40 mL:30 mL:12 mL:0.5 g:0.6 g. The stirring reaction time is 2 h. Filter and dry at a temperature of 60 - 80 °C to obtain modified foam glass particles.

[0036] Comparative Example 1: Compared with Example 3, in Comparative Example 1, during the preparation of the modified foam glass particles, phosphate coating modification is not carried out, and other conditions remain unchanged.

[0037] Comparative Example 2: Compared with Example 3, in Comparative Example 2, during the preparation of the modified foam glass particles, the hybrid emulsion is not added for modification, and other conditions remain unchanged.

[0038] Comparative Example 3: Comparative Example 3 is compared with Example 3. In the preparation process of the lightening material based on the high-strength and low-density cement slurry system, no reinforcing fiber is added, and other conditions remain unchanged.

[0039] Experimental Example: Slowly add portland cement into the pre-slurry liquids prepared in Examples 1-3 and Comparative Examples 1-3, and stir at a stirring speed of 500 rpm for 12 minutes to evenly disperse the cement particles, and prepare cements of lightening materials based on high-strength and low-density cement slurry systems with three different densities of 1.6 g / cm 3 , 1.5 g / cm 3 and 1.4 g / cm 3 According to the national standard GB / T19139-2012, conduct sedimentation stability and thickening time performance measurements on the cements of lightening materials based on high-strength and low-density cement slurry systems prepared in Examples 1-3 and Comparative Examples 1-3. The measurement results are shown in Table 1: Table 1

[0040] According to the test results in Table 1, it can be seen that the cements of lightening materials based on high-strength and low-density cement slurry systems prepared in Examples 1-3 of the present invention have good sedimentation stability and short thickening time. By comparing Comparative Examples 1-3 and Examples 1-3, it can be seen that adding phosphate coating modification, hybrid emulsion modification, and reinforcing fiber can enhance the sedimentation stability of oil well cement and shorten its thickening time.

[0041] According to the ISO679:2009 standard, conduct 48-hour compressive strength measurements on the cement samples of the new lightening materials for oil well cement prepared in Examples 1-3 and Comparative Examples 1-3 with a density of 1.4 g / cm 3 . The measurement results are shown in Table 2: Table 2

[0042] According to the test results in Table 2, it can be seen that the cements of lightening materials based on high-strength and low-density cement slurry systems prepared in Examples 1-3 of the present invention have good compressive strength. By comparing Comparative Examples 1-3 and Examples 1-3, it can be seen that adding phosphate coating modification, hybrid emulsion modification, and reinforcing fiber can enhance the compressive strength of oil well cement.

[0043] As described above, only the preferred specific embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

[0044] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments only. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A lightening material based on a high-strength and low-density cement slurry system, characterized in that, The preparation method comprises the following steps: (1) An enhanced foam glass granule is prepared by compounding waste glass, special glass, slag, reinforcing fiber, and nano-montmorillonite; (2) The surface of the enhanced foam glass granule is modified by double-layer coating to obtain a modified foam glass granule; (3) Methyl vinyl polyoxyethylene ether, alkyl glycoside, hydroxypropyl methyl cellulose, and nano-silica are respectively dissolved in deionized water, and the modified foam glass granule is added, followed by stirring to prepare a pre-slurry liquid, thereby obtaining a lightening material for a high-strength and low-density cement slurry system.

2. The lightening material based on the high-strength and low-density cement slurry system according to claim 1, wherein, In step (3), the mass ratio of methyl vinyl polyoxyethylene ether, alkyl glycoside, hydroxypropyl methyl cellulose, nano-silica, modified foam glass granule, and deionized water is 0.6-1: 0.1-0.3: 0.1-0.3: 1-2: 35-45: 40-50.

3. The lightening material based on the high-strength and low-density cement slurry system according to claim 1, wherein Step (1) includes the following process: S1. After the waste glass and special glass are cleaned, they are respectively crushed and then ball-milled to obtain waste glass powder and special glass powder; the slag is subjected to magnetic separation and grinding to obtain fine slag; S2. The waste glass powder, special glass powder, and slag powder are mixed and stirred, a foaming agent and a first foam stabilizer are added, and stirring is continued until evenly mixed. Then, the reinforcing fiber and nano-montmorillonite are successively added while stirring to obtain an enhanced mixed powder; S3. The enhanced mixed powder is loaded into a mold, and initial heating, decomposition of the foaming agent, addition of a second foam stabilizer, foaming, and annealing are successively carried out to obtain a foam glass block, which is crushed and screened to obtain enhanced foam glass granules.

4. The lightening material based on the high-strength and low-density cement slurry system according to claim 3, characterized in that, In S1, the crushing particle size is less than 1 mm, the particle sizes of the waste glass powder, special glass powder, and fine slag are 50-200 μm, the waste glass is bottle jars or construction waste glass, the slag is blast furnace slag, and the special glass is borate glass.

5. The lightening material based on the high-strength and low-density cement slurry system according to claim 3, wherein In S2, the reinforcing fiber is one or more of glass fiber, carbon fiber, and basalt fiber, and the fiber length is 3-6 mm; the mass ratio of the waste glass powder, special glass powder, fine slag, reinforcing fiber, nano-montmorillonite, foaming agent, and first foam stabilizer is 100: 10-20: 20-30: 2-6: 1-2.5: 4-6: 2; the foaming agent is obtained by mixing calcium carbonate and silicon carbide in a mass ratio of 4-5: 1-2, the first foam stabilizer is obtained by mixing boric acid and borax, the second foam stabilizer is sodium phosphate, and the mass ratio of boric acid, borax, and sodium phosphate is 1.5: 0.5: 0.

5.

6. The weighting material based on the high-strength and low-density cement slurry system according to claim 1, characterized in that, In S3, the heating rate in the initial heating stage is 5-10 °C / min, and the temperature is raised to 300-400 °C with a holding time of 10-20 min; the heating rate in the foaming agent decomposition stage is 2-5 °C / min, and the temperature is raised to 600-700 °C with a holding time of 15-30 min; the heating rate in the foaming stage is 3-5 °C / min, and the temperature is raised to 800-950 °C with a holding time of 10-30 min; the cooling rate in the initial annealing stage is 1-5 °C / min, and the temperature is lowered to 400-500 °C with a holding time of 2-4 h, and the cooling rate in the post-annealing stage is 5-10 °C / h.

7. The lightening material based on the high-strength and low-density cement slurry system according to claim 1, characterized in that, Step (2) includes the following process: Q1. Wash the enhanced foam glass particles, dry them to constant weight, soak them in an aluminum dihydrogen phosphate solution, take them out, drain, and dry and cure to obtain phosphate-coated foam glass particles; Q2. Add the phosphate-coated foam glass particles to deionized water containing a dispersant, stir evenly to obtain a suspension. Under stirring, add the hybrid emulsion to the foam glass particle suspension, stir and react, filter, and dry to obtain modified foam glass particles.

8. The lightening material based on the high-strength and low-density cement slurry system according to claim 7, wherein, In Q1, the concentration of the aluminum dihydrogen phosphate solution is 10-20 wt%.

9. The lightening material based on the high-strength and low-density cement slurry system according to claim 7, wherein In Q2, the hybrid emulsion is obtained by adding nano-montmorillonite modified with 0.8-1.5 wt% of KH-550 silane coupling agent to a composite emulsion and ultrasonically dispersing it. The volume ratio of the composite emulsion to the nano-montmorillonite is 100:3-4; the composite emulsion is prepared from an acrylic emulsion, a vinyl acetate emulsion, a polyurethane emulsion, a styrene-acrylic emulsion, ZW-2, and silica fume according to the dosage ratio of 40-50 mL:35-40 mL:25-30 mL:10-12 mL:0.3-0.5 g:0.35-0.6 g.

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