A cementitious composition, cementitious slurry, and methods of making and using the same

Abstract

The application belongs to the technical field of cementing cement, and particularly relates to a cementing material composition, cement slurry and a preparation method and application thereof. The cementing material composition provided by the application comprises cement, a phosphate, an early strength agent and a shrinkage reducing agent. The cement slurry prepared by using the cementing material composition has the advantages of early strength, crack resistance and CO2 corrosion resistance, especially has the ability of supercritical CO2 corrosion resistance, and can ensure long-term CO2 storage capacity.

Description

Technical Field

[0001] This invention belongs to the field of cementing technology, specifically relating to a cementitious material composition, cement slurry, its preparation method, and its application. Background Technology

[0002] Climate change is a severe challenge facing humanity in the 21st century, a major global issue profoundly impacting the economic development and ecological environment of all countries. Actively addressing climate change has become a global consensus and an inevitable trend. Carbon Capture, Utilization, and Storage (CCUS) technology holds promise for achieving near-zero emissions from fossil fuel utilization and has received widespread attention from the international community. CCUS involves capturing and purifying CO2 emitted during production processes or from the atmosphere, then utilizing it or injecting it into formations for storage, thereby reducing CO2 emissions. Currently, carbon sequestration wells specifically designed for CO2 geological storage have emerged both domestically and internationally and have garnered significant attention. The key to carbon sequestration is ensuring that the stored CO2 does not leak; therefore, high requirements are placed on the quality of cementing and the CO2 corrosion resistance of the cementing materials.

[0003] Currently, the cement used in oilfield cementing operations is mainly silicate cement. However, the hydration products of silicate cement are unstable in CO2-rich environments. When CO2-containing water diffuses into the cement matrix, the dissociated acid (H2CO3) reacts with free calcium hydroxide (CH) and hydrated calcium silicate (CSH) gel. The reaction products can dissolve and migrate out of the cement matrix. At this point, the compressive strength of the cement stone decreases, while its permeability and porosity increase, ultimately leading to a loss of protection for the wellbore and causing CO2 to escape to the surface and re-enter the atmosphere.

[0004] Furthermore, CO2 enters a supercritical state when the temperature exceeds 31.1℃ and the pressure exceeds 7.38MPa. In CO2 geological storage, most reservoirs reach temperatures and pressures above the critical point, and CO2 is often stored in the geological body in a supercritical state. Supercritical CO2 is characterized by high permeability and a high diffusion coefficient, making its corrosive effect on cementing cement far greater than in ordinary geological environments. Therefore, developing cementing cement resistant to supercritical CO2 corrosion is a crucial step in achieving CO2 geological storage. Phosphate-modified aluminate cement's main hydration product, light-based apatite (Ca), is also relevant. 10Phosphate-modified aluminate cement (PO4)6(OH)2 and boehmite (AlO(OH)) possess resistance to CO2 corrosion. Therefore, phosphate-modified aluminate cement is considered the most effective cementitious material against CO2 corrosion and has great potential for application in carbon sequestration. However, currently developed CO2-resistant phosphate-modified aluminate cements have low phosphate content, resulting in incomplete reaction to form hydroxyapatite and boehmite. Furthermore, the main hydration product of the incompletely consumed aluminate cement, calcium aluminate hydrate (C3AH6), is not resistant to CO2 corrosion. For example, CA50 cement with approximately 35% calcium oxide and 50% alumina content requires about 30% of the aluminate cement mass to completely generate hydroxyapatite. At higher phosphate contents, the early strength of modified aluminate cement is slower under medium- and low-temperature conditions, making it unsuitable for practical engineering applications. Moreover, high phosphate content leads to significant shrinkage of modified aluminate cement, making it prone to significant cracking under cement ring constraints, thus hindering the sealing of carbon sequestration wells. Therefore, the phosphate content of existing phosphate-modified aluminate cement is usually within 15% of the mass of aluminate cement. Although its resistance to CO2 corrosion is much higher than that of silicate cement, it still cannot guarantee the long-term storage of supercritical CO2. The development of modified phosphate cement with early strength, crack resistance and resistance to supercritical CO2 corrosion is urgently needed. Summary of the Invention

[0005] In order to solve one of the above-mentioned technical problems in the prior art, the present invention provides a cementitious material composition, a cement slurry prepared using the composition, and its application.

[0006] The technical solution of the present invention is as follows:

[0007] The cementitious material composition provided by the present invention includes: cement, phosphate, early strength agent and shrinkage reducing agent.

[0008] The aforementioned cementitious material composition also includes active admixtures.

[0009] The above-mentioned cementitious material composition, by weight, includes: 0.8 to 1.2 parts of cement, 0.15 to 0.4 parts of phosphate, 0 to 0.2 parts of active admixture, 0.01 to 0.08 parts of early strength agent and 0.01 to 0.18 parts of shrinkage reducer.

[0010] The above-mentioned cementitious material composition, by weight, includes: 0.9 to 1.1 parts of cement, 0.2 to 0.35 parts of phosphate, 0.1 to 0.2 parts of active admixture, 0.02 to 0.06 parts of early strength agent, and 0.02 to 0.15 parts of shrinkage reducer.

[0011] The cementitious material composition described above, wherein the cement includes aluminate cement.

[0012] In the above-mentioned gelling material composition, the phosphate includes one or more of sodium phosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium polyphosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.

[0013] The aforementioned cementitious material composition, wherein the early strength agent includes hydroxyapatite.

[0014] In the above-mentioned cementitious material composition, the hydroxyapatite is nano-hydroxyapatite with an average particle size of 10-50 nm.

[0015] The shrinkage reducing agent in the above-mentioned cementitious material composition includes zeolite powder and / or water-absorbing resin.

[0016] In the above-mentioned cementitious material composition, the water absorption rate of the zeolite powder is not less than 10% of its own mass, and / or the average particle size of the zeolite powder is 0.05 to 1 mm.

[0017] In the above-mentioned gelling material composition, the water absorption rate of the water-absorbing resin is not less than 10,000% of its own mass, and the maximum particle size of the dry powder of the water-absorbing resin is not more than 0.5 mm.

[0018] The above-mentioned cementitious material composition, wherein the active admixture includes one or more of fly ash, silica fume, and diatomaceous earth.

[0019] On the other hand, the present invention also provides a cement slurry, the raw materials of which include the above-mentioned cementitious material composition.

[0020] In another aspect, the present invention also provides a method for preparing cement slurry, comprising:

[0021] (1) Mix cement, phosphate, early strength agent, active admixture and shrinkage reducer evenly according to the proportion to obtain a cementitious material composition;

[0022] (2) The cementitious material composition is mixed with water at a water-cement ratio of 0.4 to 0.55 to obtain the cement slurry.

[0023] In the above-mentioned method for preparing cement slurry, the water-cement ratio is 0.45 to 0.52.

[0024] In the above-mentioned method for preparing cement slurry, the water-cement ratio is 0.48 to 0.50.

[0025] Furthermore, the present invention also provides the application of the above-mentioned cementitious material composition, the above-mentioned cement slurry, or the cement slurry obtained by the above-mentioned preparation method in cementing.

[0026] The above applications include cementing of oil wells and cementing of carbon storage wells.

[0027] The technical solution of the present invention has the following beneficial effects:

[0028] (1) In the gelling material composition of the present invention, each component can undergo acid-base reaction during the hardening process, and the resulting gelling material will not be corroded by CO2.

[0029] (2) In this invention, hydroxyapatite contributes to the early strength development of the system at medium and low temperatures (40–80°C), and zeolite powder contributes to the shrinkage reduction and crack resistance of the system. Therefore, cement prepared using the composition of this invention has the advantages of early strength, crack resistance, and resistance to CO2 corrosion;

[0030] (3) The cement slurry prepared by the cementitious material composition of the present invention has the advantages of early strength, crack resistance and CO2 corrosion resistance, especially the ability to resist supercritical CO2 corrosion, which can ensure the long-term sealing ability of CO2. Attached Figure Description

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0032] Figure 1 The results of the crack resistance of the cement ring prepared in Example 1 are shown.

[0033] Figure 2 The results of the crack resistance of the cement ring prepared by Comparative Example 2 are shown. Detailed Implementation

[0034] To fully understand the purpose, features, and effects of this invention, the following detailed embodiments are provided. Except as described below, the process methods of this invention employ conventional methods or apparatus in the art. Unless otherwise specified, the terms and expressions used below have the meanings commonly understood by those skilled in the art.

[0035] According to a first aspect of the present invention, the present invention provides a cementitious material composition comprising: cement, phosphate, early strength agent and shrinkage reducing agent, preferably further comprising active admixture.

[0036] In the cementitious material composition of this invention, phosphates hydrolyze to produce phosphate ions, and aluminate cement reacts with phosphate ions to generate hydroxyapatite and bauxite. An early-strength agent promotes and accelerates the reaction between cement and phosphates. A shrinkage-reducing agent reduces the shrinkage of the composition by replenishing moisture, thereby reducing cracking. Active admixtures fill pores and provide subsequent strength growth. Through the interaction of these components, the cement prepared from the composition exhibits advantages such as early strength, crack resistance, and resistance to CO2 corrosion.

[0037] The components of the gelling material composition of the present invention will be described in detail below.

[0038] cement

[0039] Cement is a building material composed of highly reactive calcium aluminum silicon minerals, which hardens into a solid material. In this invention, cement, as the main reactant, reacts with phosphates to generate hydroxyapatite and boehmite, thereby binding the composition into a cohesive whole.

[0040] In some preferred embodiments, the cement comprises aluminate cement.

[0041] In some preferred embodiments, the cement in the cementitious material composition is 0.8 to 1.2 parts by weight. For example, 0.8 parts, 0.9 parts, 1.0 parts, 1.1 parts, 1.2 parts, or any value between them.

[0042] In the composition of the present invention, when the weight of cement is less than 0.8 parts, the strength of the composition is low; when the weight of cement is greater than 1.2 parts, the resistance of the composition to supercritical CO2 corrosion is poor.

[0043] More preferably, the cement in the cementitious material composition is 0.9 to 1.1 parts by weight.

[0044] phosphate

[0045] Phosphate is the main reactant in the composition of this invention. It can react with cement to generate hydroxyapatite and boehmite, thereby binding the composition into a whole.

[0046] In some preferred embodiments, the phosphate includes one or more of sodium phosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium polyphosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate. Sodium hexametaphosphate is more preferred.

[0047] In some preferred embodiments, the phosphate in the gelling material composition is 0.15 to 0.4 parts by weight, for example 0.15, 0.18, 0.2, 0.25, 0.3, 0.35, 0.38, 0.4 or any value between them.

[0048] In the composition of the present invention, when the weight part of phosphate is less than 0.15 parts, the composition has poor resistance to supercritical CO2 corrosion; when the weight part of phosphate is greater than 0.4 parts, the composition has low strength.

[0049] More preferably, the phosphate in the gelling material composition is 0.2 to 0.35 parts by weight.

[0050] Early strength agent

[0051] Concrete accelerators are admixtures that improve the early strength of concrete without significantly affecting its later strength. Their main function is to accelerate cement hydration and promote the development of early concrete strength; they possess both early strength and some water-reducing and strength-enhancing properties.

[0052] In some preferred embodiments, the early strength agent includes hydroxyapatite.

[0053] In some preferred embodiments, the hydroxyapatite is nano-hydroxyapatite with an average particle size of 10-50 nm, preferably 10-30 nm.

[0054] In some preferred embodiments, the early-strength agent in the cementitious material composition is 0.01 to 0.08 parts by weight, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08 parts or any value between them.

[0055] In the composition of the present invention, when the weight part of the early strength agent is less than 0.01 parts, the effect of promoting early strength development is not obvious; when the weight part of the early strength agent is greater than 0.08 parts, the composition reacts too quickly in the early stage, resulting in excessive heat release and cracking.

[0056] More preferably, the early-strength agent in the cementitious material composition is 0.02 to 0.06 parts by weight.

[0057] Shrinkage agent

[0058] Shrinkage reducing agent is an organic compound that reduces the surface tension of the liquid phase in the pores of concrete. Its main mechanism of action is to reduce the surface tension of the liquid phase in the capillary of concrete, thereby reducing the negative pressure in the capillary and reducing shrinkage stress.

[0059] In some preferred embodiments, the shrinkage reducing agent includes zeolite powder and / or water-absorbing resin.

[0060] Wherein, the water absorption rate of the zeolite powder is not less than 10% of its own mass, and / or, the average particle size of the zeolite powder is 0.05 to 1 mm.

[0061] The water absorption rate of the water-absorbing resin is not less than 10,000% of its own mass, and the maximum particle size of the dry powder of the water-absorbing resin is not more than 0.5 mm.

[0062] In some preferred embodiments, the shrinkage reducing agent in the gelling material composition is 0.01 to 0.18 parts by weight, for example 0.01, 0.03, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18 or any value between them.

[0063] In the composition of the present invention, when the weight part of the shrinkage reducing agent is less than 0.01 parts, the shrinkage reduction effect is not obvious; when the weight part of the shrinkage reducing agent is greater than 0.08 parts, the strength of the composition is low.

[0064] More preferably, the shrinkage-reducing agent in the gelling material composition is 0.02 to 0.15 parts by weight.

[0065] Active admixtures

[0066] Admixtures are powdered minerals, whether natural or artificial, that are added during concrete mixing to improve concrete performance, save water, and adjust concrete strength grade.

[0067] In some preferred embodiments, the active admixture includes one or more of fly ash, silica fume, and diatomaceous earth, with fly ash being more preferred.

[0068] In some preferred embodiments, the active admixture in the cementitious material composition is 0 to 0.2 parts by weight, for example, 0 parts, 0.0 parts, 0.05 parts, 0.08 parts, 0.1 parts, 0.15 parts, 0.2 parts or any value between them.

[0069] In the compositions of the present invention, when the weight fraction of the active admixture is greater than 0.2, the early strength of the composition is low.

[0070] More preferably, the active admixture in the cementitious material composition is 0.1 to 0.2 parts by weight.

[0071] In some embodiments, the composition comprises, by weight, 0.8 to 1.2 parts of aluminate cement, 0.15 to 0.4 parts of phosphate, 0 to 0.2 parts of active admixture, 0.01 to 0.08 parts of early strength agent and 0.01 to 0.18 parts of shrinkage reducer.

[0072] In some preferred embodiments, the composition comprises, by weight, 0.9 to 1.1 parts of aluminate cement, 0.2 to 0.35 parts of phosphate, 0.1 to 0.2 parts of active admixture, 0.02 to 0.06 parts of early strength agent and 0.02 to 0.15 parts of shrinkage reducer.

[0073] In some preferred embodiments, the composition comprises, by weight, 1 part aluminate cement, 0.2 to 0.35 parts sodium hexametaphosphate, 0.1 to 0.2 parts fly ash, 0.02 to 0.06 parts hydroxyapatite, and 0.02 to 0.15 parts zeolite powder.

[0074] According to a second aspect of the present invention, the present invention also provides a cement slurry, the raw materials for which are composed of the above-described cementitious material composition.

[0075] According to a third aspect of the present invention, the present invention also provides a method for preparing cement slurry, comprising:

[0076] (1) Mix cement, phosphate, early strength agent, active admixture and shrinkage reducer evenly according to the proportion to obtain a cementitious material composition;

[0077] (2) The cementitious material composition is mixed with water at a water-cement ratio of 0.4 to 0.55 to obtain the cement slurry.

[0078] In some preferred embodiments, the water-cement ratio is 0.45 to 0.52, and more preferably 0.48 to 0.50.

[0079] According to a fourth aspect of the invention, the invention also provides the application of the above-described cementitious material composition and the above-described cement slurry in cementing.

[0080] The cementitious material composition and cement slurry of the present invention have the advantages of early strength, crack resistance and CO2 corrosion resistance, and can be used for cementing oil wells and carbon storage wells.

[0081] Example

[0082] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments, unless otherwise specified, were performed according to conventional methods and conditions. The raw materials used in the following embodiments were all commercially available.

[0083] The hydroxyapatite powder used in the following embodiments and comparative examples of the present invention has an average particle size of 20 nm, the zeolite powder has an average particle size of 0.7 mm, and the water absorption rate is approximately 17% of its own mass.

[0084] Example 1

[0085] This embodiment provides a modified aluminate cement, which, by weight, comprises the following components: 1 part aluminate cement; 0.3 parts food-grade sodium hexametaphosphate; 0.1 parts fly ash; 0.02 parts hydroxyapatite powder; 0.05 parts zeolite powder; and 0.5 parts water.

[0086] Examples 2-7

[0087] The modified aluminate cement provided in Examples 2-7 differs from that in Example 1 in that the weight proportions of each component are different, as detailed in Table 1.

[0088] Table 1

[0089]

[0090] Note: The symbol " / " in the table represents 0 copies.

[0091] Example 8

[0092] 1 part aluminate cement, 0.3 parts sodium hexametaphosphate, 0.1 parts fly ash, 0.02 parts hydroxyapatite powder, 0.01 parts water-absorbing resin, and 0.5 parts water.

[0093] Example 9

[0094] 1 part aluminate cement, 0.3 parts sodium hexametaphosphate, 0.1 parts fly ash, 0.02 parts hydroxyapatite powder, 0.1 parts diatomite, and 0.5 parts water.

[0095] Comparative Examples 1-2 and 4-5

[0096] The modified aluminate cements provided in Comparative Examples 1-2 and 4-5 differ from those in Example 1 in that they do not contain hydroxyapatite powder or zeolite powder, and the weight proportions of other components are slightly different, as shown in Table 1 above.

[0097] Comparative Example 3

[0098] This comparative example provides an API G-grade oil well cement, which, by weight, comprises the following components: 1 part oil well cement and 0.44 parts tap water.

[0099] Strength test blocks were prepared using the cements from Examples 1-7 and Comparative Examples 1-5, and were cured and tested at 60°C according to the test methods for oil well cement.

[0100] 1. Compressive strength test

[0101] The compressive strength of the test blocks was tested in accordance with GB / T 19139-2012 "Test Methods for Cement in Oil Wells", and the test results are shown in Table 2.

[0102] Table 2

[0103]

[0104] As can be seen from Table 2, under curing at 60℃, the 1-day compressive strength of cement specimens in Examples 1-9 can all reach more than 10MPa, while the 1-day strength of Comparative Examples 1 and 4, which did not use the early-strength agent hydroxyapatite powder, is less than 2.0MPa, and the 3-day strength is only about 2.0MPa. It can be seen that under high phosphate content, the early strength development of modified aluminate cement is slow, while the incorporation of nano hydroxyapatite has the effect of early strength.

[0105] As can be seen from Examples 6 and 7, excessive amounts of the early-strength agent hydroxyapatite powder and the shrinkage-reducing agent zeolite powder lead to lower strength in the modified aluminate cement, which is caused by the introduction of too many interfaces. Furthermore, the initial consistency of the freshly mixed slurry in Example 7 is relatively high, indicating that excessive addition of the shrinkage-reducing agent zeolite powder is detrimental to the cementing process of the modified cement.

[0106] 2. Crack resistance test

[0107] The crack resistance of the modified aluminate cement in Examples 1, 2, and 5 was studied using steel pipes with outer diameters of 50 mm and 22 mm, respectively, and wall thicknesses of 2 mm, respectively, to simulate the pipe wall of an oil well. The results are as follows: Figure 1 and Figure 2 As shown.

[0108] from Figure 1 It can be seen that the cement ring in Example 1 itself showed no cracking, nor were there any gaps between it and the inner and outer pipe walls. And from... Figure 2 As can be seen, the cement ring in Comparative Example 2 exhibited significant cracks, clearly rendering it unsuitable for CO2 sequestration. Furthermore, the cement ring in Comparative Example 5 also showed similar prominent cracks to those in Comparative Example 2. This demonstrates the necessity of using a shrinkage-reducing agent (zeolite powder) in modified aluminate cement.

[0109] 3. Test on resistance to supercritical CO2 corrosion

[0110] The cement from Example 1 and Comparative Example 3 were prepared into cylindrical specimens with a diameter of 25 mm and a height of 35 mm. After curing at 60°C for 1 day, they were demolded and immersed in water, and then placed in a supercritical CO2 environment at 60°C and 12 MPa for 30 days and 90 days, respectively, for corrosion. After removal, quality and strength tests were performed, and the results are shown in Table 3.

[0111]

[0112] As shown in Table 3, after 90 days of corrosion, the quality and strength of the modified aluminate cement in Example 1 were improved, while the quality and strength of the oil well cement decreased significantly. This indicates that the modified aluminate cement provided by this invention has excellent resistance to supercritical CO2 corrosion.

[0113] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art should understand that these embodiments are merely illustrative of the invention and should not be construed as limiting its scope. It should be noted that any variations and substitutions equivalent to these embodiments should be considered to be covered within the scope of the claims. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A cementitious material composition, characterized in that, By weight, it includes: 0.8-1.2 parts cement, 0.15-0.4 parts phosphate, 0-0.2 parts active admixture, 0.01-0.08 parts early strength agent, and 0.01-0.18 parts shrinkage reducer; Wherein, the shrinkage reducing agent includes zeolite powder and / or water-absorbing resin; the water absorption rate of the zeolite powder is not less than 10% of its own mass, and / or the average particle size of the zeolite powder is 0.05~1mm; the water absorption rate of the water-absorbing resin is not less than 10000% of its own mass, and the maximum particle size of the dry powder of the water-absorbing resin does not exceed 0.5mm. The cement is aluminate cement; the early strength agent is hydroxyapatite.

2. The cementitious material composition according to claim 1, characterized in that, By weight, it includes: 0.9-1.1 parts cement, 0.2-0.35 parts phosphate, 0.1-0.2 parts active admixture, 0.02-0.06 parts early strength agent, and 0.02-0.15 parts shrinkage reducer.

3. The cementitious material composition according to any one of claims 1-2, characterized in that, The phosphate includes one or more of sodium phosphate, sodium tripolyphosphate, sodium hexametaphosphate, sodium polyphosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.

4. The cementitious material composition according to claim 1, characterized in that, The hydroxyapatite is nano-hydroxyapatite with an average particle size of 10~50nm.

5. The cementitious material composition according to any one of claims 1-2, characterized in that, The active admixture includes one or more of fly ash, silica fume, and diatomaceous earth.

6. A cement slurry, characterized in that, The raw materials for preparation include the gelling material composition according to any one of claims 1-5.

7. A method for preparing a cement slurry, characterized in that, include: (1) Mix 0.8~1.2 parts of cement, 0.15~0.4 parts of phosphate, 0.01~0.08 parts of early strength agent, 0~0.2 parts of active admixture and 0.01~0.18 parts of shrinkage reducer evenly according to the weight ratio to obtain a cementitious material composition; Wherein, the shrinkage reducing agent includes zeolite powder and / or water-absorbing resin; the water absorption rate of the zeolite powder is not less than 10% of its own mass, and / or the average particle size of the zeolite powder is 0.05~1mm; the water absorption rate of the water-absorbing resin is not less than 10000% of its own mass, and the maximum particle size of the dry powder of the water-absorbing resin does not exceed 0.5mm. Wherein, the cement is aluminate cement; the early strength agent is hydroxyapatite; (2) The cementitious material composition is mixed with water at a water-cement ratio of 0.4 to 0.55 to obtain the cement slurry.

8. The method for preparing cement slurry according to claim 7, characterized in that, The water-cement ratio is 0.45~0.

52.

9. The method for preparing cement slurry according to claim 8, characterized in that, The water-cement ratio is 0.48~0.

50.

10. The application of the cementitious material composition according to any one of claims 1-5, the cement slurry according to claim 6, or the cement slurry obtained by the preparation method according to any one of claims 7-9 in cementing.

11. The application according to claim 10, wherein the cementing includes oil well cementing and carbon storage well cementing.

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