Geopolymer activator

Abstract

The invention relates to the technical field of oil and gas well cementation, in particular to a geopolymer activator, and aims to solve the problem of insufficient adjustability of thickening time of fly ash geopolymers excited by reactive excitants such as sodium carbonate and calcium hydroxide due to too high dissolution rate of calcium hydroxide. The geopolymer activator provided by the invention comprises the following components in parts by weight: 10-12 parts of high-temperature burnt calcium oxide; 10 to 12 parts of medium-temperature burnt calcium oxide; 9-11 parts of low-temperature burnt calcium oxide; 40 to 60 parts of sodium carbonate; and 5-31 parts of sodium sulfate. The geopolymer activator has the advantages that the release rate is low, and the thickening time of the geopolymer prepared from the geopolymer activator is easy to regulate and control, and can well meet the operation construction of oil and gas well cementing.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well cementing, and in particular to a geopolymer activator. Background Art

[0002] As international oil prices continue to hover at medium and low levels in recent years, the pressure to reduce costs and increase efficiency in oilfield development has gradually increased, and low-cost fly ash cement slurry has gradually gained a larger application space. Fly ash and slag are both industrial wastes. Their rational use belongs to the utilization of three wastes, turning waste into treasure, and is an important means to solve the contradiction between production environmental pollution and resource shortage in my country. Therefore, using the potential activity of fly ash to replace oil well cement for cementing projects is of great strategic significance for reducing development costs and environmental protection. The main component of fly ash is acidic oxides, and its structure and chemical properties are the same or similar to those of glass. Its activity is most easily stimulated in alkaline media, and it needs to be stimulated more quickly and fully under alkaline conditions. The activator used in traditional alkali-activated geopolymer materials is sodium hydroxide, etc. Sodium hydroxide dissolves and releases a large amount of heat, and there are certain risks during use. The curing mechanism of geopolymers is the activation mechanism of volcanic ash materials such as fly ash in NaOH solution. When fly ash comes into contact with alkaline solution, the soluble solid particles on the surface of the particles dissolve and release the corresponding ions; in OH - Under the action of OH, the Si-O-Si, Si-O-Al and Al-O-A1 bonds in the fly ash are broken, the aluminum-oxygen tetrahedron [AlO4] or silicon-oxygen tetrahedron [SiO4] network structure is destroyed, and the - The higher the concentration, the stronger the destructive effect on Si-O bonds and Al-O bonds, and depolymerization occurs to form Al(OH) 4- or Al(OH)6 3- 、Si(OH) 3- or SiO2(OH)2 2- Plasma monomers; then the free [SiO4] and [A1O4] tetrahedral units in an alkaline environment are repolymerized in the solution into Si-O-Al-O bonds to form a three-dimensional grid of silicon-aluminum oxide compounds. Under the high temperature and strong alkaline environment of sodium hydroxide in oil and gas wells, the fly ash dissolves too quickly, causing the geopolymer to solidify too quickly, resulting in a short thickening / setting time of the geopolymer, and it is difficult to effectively adjust it using traditional retarders. Therefore, the industry has adopted the technical idea of ​​using reactive activators such as sodium carbonate + calcium hydroxide that can produce sodium hydroxide through reaction to replace sodium hydroxide, and the reaction rate of sodium carbonate + calcium hydroxide can be controlled by retarders to achieve the control of the thickening time / setting time of the geopolymer. Although the reaction rate of sodium carbonate and calcium hydroxide can be controlled by retarders, due to the relatively fast dissolution rate of calcium hydroxide, the adjustable temperature of the thickening time of the geopolymer using this method is difficult to exceed 110°C.

[0003] Therefore, the traditional reactive activator made of calcium hydroxide and sodium carbonate or sodium sulfate has a relatively fast dissolution rate in water. It is difficult to control the reaction rate of calcium hydroxide and sodium carbonate or sodium sulfate by using a retarder at a high temperature above 100°C, and thus it is difficult to achieve the regulation of the thickening time of the geopolymer. Summary of the invention

[0004] The object of the present invention is to provide a geopolymer activator to solve the problem that the thickening time of fly ash geopolymer activated by reactive activators such as sodium carbonate and calcium hydroxide is insufficiently adjustable due to the excessively fast dissolution rate of calcium hydroxide.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] A geopolymer activator, the components and weight ratios of which are as follows:

[0007] High temperature burning calcium oxide: 10-12 parts;

[0008] Medium temperature burning calcium oxide: 10-12 parts;

[0009] Low temperature burning calcium oxide: 9-11 parts;

[0010] Sodium carbonate: 40-60 parts;

[0011] Sodium sulfate: 5-31 parts.

[0012] Preferably, the high temperature calcination of calcium oxide requires calcining the calcium oxide particles at 1400°C.

[0013] Preferably, the high-temperature calcination time of calcium oxide is more than 4 hours.

[0014] Preferably, the medium-temperature calcination of calcium oxide requires calcining the calcium oxide particles at 1100°C.

[0015] Preferably, the medium-temperature calcination of calcium oxide takes more than 4 hours.

[0016] Preferably, the low temperature calcination of calcium oxide requires calcining the calcium oxide particles at 800°C.

[0017] Preferably, the low-temperature calcination time of calcium oxide is more than 4 hours.

[0018] Preferably, the particle size of the high-temperature calcined calcium oxide is 100 mesh to 200 mesh.

[0019] Preferably, the particle size of the medium-temperature calcined calcium oxide is 100 mesh to 200 mesh.

[0020] Preferably, the particle size of the low-temperature calcined calcium oxide is 100 mesh to 200 mesh.

[0021] In the present invention, calcium oxide is used to replace calcium hydroxide, and calcium oxide is mixed and used after being burned at 800°C, 1100°C, and 1400°C for more than 4 hours, respectively, to achieve passivation of the surface of calcium oxide, which can greatly reduce the dissolution rate of calcium oxide, thereby reducing the difficulty of the retarder to regulate the reaction rate of calcium oxide with sodium carbonate or sodium sulfate. Moreover, calcium oxide can also react with sodium carbonate or sodium sulfate to generate sodium hydroxide, thereby stimulating fly ash to prepare geopolymer. The purpose of mixing calcium oxide after burning at 800°C, 1100°C, and 1400°C for more than 4 hours is to take into account the adjustability of the thickening time of the geopolymer and the early strength of the geopolymer. If the selected calcium oxide is burned at more than 1400°C for 4 hours, although the thickening time is easier to adjust, the early strength of the geopolymer is too low due to the slow dissolution rate of calcium oxide. If the selected calcium oxide is burned at 800℃ or 1100℃ for 4 hours, although the early strength is acceptable, the relatively fast dissolution rate of calcium oxide increases the difficulty of controlling the thickening time of geopolymer.

[0022] Based on the above technical solutions, the technical effects that can be achieved by the present invention are:

[0023] In the present invention, calcium oxide is used to replace calcium hydroxide, and calcium oxide is mixed and used after being burned at 800°C, 1100°C, and 1400°C for more than 4 hours, respectively, to achieve passivation of the surface of calcium oxide, which can greatly reduce the dissolution rate of calcium oxide, thereby reducing the difficulty of the retarder to regulate the reaction rate of calcium oxide with sodium carbonate or sodium sulfate. Moreover, calcium oxide can also react with sodium carbonate or sodium sulfate to generate sodium hydroxide, thereby stimulating fly ash to prepare geopolymer. The purpose of mixing calcium oxide after burning at 800°C, 1100°C, and 1400°C for more than 4 hours is to take into account the adjustability of the thickening time of the geopolymer and the early strength of the geopolymer. If the selected calcium oxide is burned at more than 1400°C for 4 hours, although the thickening time is easier to adjust, the early strength of the geopolymer is too low due to the slow dissolution rate of calcium oxide. If the selected calcium oxide is burned at 800℃ or above 1100℃ for 4 hours, although the early strength is acceptable, the dissolution rate of calcium oxide is relatively fast, which increases the difficulty of controlling the thickening time of geopolymer.

[0024] The reactive geopolymer activator is prepared by replacing calcium hydroxide or ordinary unburned calcium oxide with a mixture of calcium oxide burned at high temperatures of 800°C, 1100°C, and 1400°C, which can effectively reduce the difficulty of adjusting the thickening time of the geopolymer and ensure the early strength of the geopolymer. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments.

[0026] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0028] Embodiment 1:

[0029] 9 parts of low-temperature burned calcium oxide, 10 parts of medium-temperature burned calcium oxide, 10 parts of high-temperature burned calcium oxide, 40 parts of sodium carbonate, and 31 parts of sodium sulfate.

[0030] Embodiment 2:

[0031] Low temperature burning calcium oxide: 10 parts, medium temperature burning calcium oxide: 11 parts, high temperature burning calcium oxide: 11 parts, sodium carbonate: 50 parts, sodium sulfate: 18 parts.

[0032] Embodiment 3:

[0033] Low temperature burning calcium oxide: 11 parts, medium temperature burning calcium oxide: 12 parts, high temperature burning calcium oxide: 12 parts, sodium carbonate: 60 parts, sodium sulfate: 5 parts.

[0034] Comparative Example 1

[0035] Calcium hydroxide: 42 parts, sodium carbonate: 58 parts.

[0036] Test Example 1:

[0037] To complete the testing of the embodiments and comparative examples, the selected geopolymer formula includes the following components in parts by weight: 100 parts of fly ash, 24 parts of activator, several parts of sodium ethylenediaminetetramethylenephosphonate, and 54 parts of water.

[0038] The test method was carried out in accordance with the national standard GBT19139-2003 "Test methods for oil well cement" to conduct preparation, thickening and strength tests of geopolymers. The results are shown in Table 1.

[0039] Table 1 Experimental results

[0040] According to the results in Table 1, for the geopolymer added with Comparative Example 1, when the amount of retarder added was 0.5% and 0.9%, respectively, the thickening time of the geopolymer was only 93min and 103min, and even when the amount of retarder added was 2.0%, the thickening time of the geopolymer was only 128min, indicating that the thickening time of the geopolymer was difficult to control when calcium hydroxide and sodium carbonate were used as activators. The geopolymers added with Example 1, Example 2, and Example 3, respectively, all had good thickening time when the amount of retarder added was 0.5%, and the thickening time was about 240min, and had good compressive strength. It shows that when high-temperature burning calcium oxide, sodium carbonate and sodium sulfate are used as activators, the difficulty of regulating the release rate of the geopolymer activator can be reduced, and the thickening time of the geopolymer is easier to control to meet the cementing operation requirements at the oil field site.

[0041] The geopolymer activator provided in this embodiment has the advantages of slow release rate and easy control of thickening time, and can better meet the requirements of oil and gas well cementing operation.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A geopolymer activator, characterized in that: The components and weight ratios are as follows: High temperature burning calcium oxide: 10-12 parts; Medium temperature burning calcium oxide: 10-12 parts; Low temperature burning calcium oxide: 9-11 parts; Sodium carbonate: 40-60 parts; Sodium sulfate: 5-31 parts.

2. The geopolymer activator according to claim 1, characterized in that The high temperature burning of calcium oxide requires burning calcium oxide particles at 1400°C.

3. The geopolymer activator according to claim 2, characterized in that The high-temperature burning time of calcium oxide is more than 4 hours.

4. The geopolymer activator according to claim 1, characterized in that The medium-temperature calcination of calcium oxide requires calcining the calcium oxide particles at 1100°C.

5. The geopolymer activator according to claim 4, characterized in that The medium-temperature calcination of calcium oxide takes more than 4 hours.

6. The geopolymer activator according to claim 1, characterized in that The low temperature calcination of calcium oxide requires calcining calcium oxide particles at 800°C.

7. The geopolymer activator according to claim 6, characterized in that The low-temperature calcination time of calcium oxide is more than 4 hours.

8. The geopolymer activator according to claim 1, characterized in that The particle size of the high-temperature calcined calcium oxide is 100-200 meshes.

9. The geopolymer activator according to claim 1, characterized in that The particle size of the medium-temperature calcined calcium oxide is 100 mesh to 200 mesh.

10. The geopolymer activator according to claim 1, characterized in that The particle size of the low-temperature calcined calcium oxide is 100-200 meshes.

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