Geopolymer cementing fluid system

Abstract

The invention relates to the technical field of oil and gas well cementing, in particular to a geopolymer cementing fluid system, and aims to solve the problem that a geopolymer prepared from sodium carbonate and calcium hydroxide is insufficient in compressive strength. The geopolymer cementing fluid system provided by the invention is prepared from the following components in parts by weight: 100 parts of a cementing material, 11 to 22 parts of sodium carbonate, 7 to 14 parts of calcium hydroxide, 10 to 18 parts of porous SiO2, 5 to 10 parts of porous Al2O3, 0.2 to 5 parts of a retarder and 50 to 70 parts of water. The geopolymer cementing fluid has the advantages of being adjustable in thickening time, high in early-stage compressive strength and the like, can be well suitable for operation construction of oil and gas well cementing, and ensures the safety of well cementing construction.

Description

Technical Field

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

[0003] The main hydration products of traditional silicate oil well cement are calcium hydroxide and hydrated calcium silicate gel, which have poor resistance to carbon dioxide corrosion and are difficult to meet the cementing requirements of CCUS / CCS wells. The phosphate aluminate cement currently recognized in the industry for its resistance to CO2 corrosion has problems such as uncontrollable properties such as thickening time and water loss, and easy flash setting when mixed with silicates. There are few reports on its application at home and abroad. Therefore, it is extremely necessary to develop a cement slurry system suitable for CCUS projects.

[0004] Geopolymer is a cementitious material prepared by mixing fly ash and activator alkali. It is named because its hydration product is a three-dimensional network structure of aluminosilicate polymers and its reaction process is similar to geochemical reactions. The hydration product of geopolymer is mainly sodium aluminosilicate gel, which has good stability in acidic environments such as hydrochloric acid, nitric acid, and carbonic acid, so it has good resistance to CO2 corrosion, and it has good low permeability. It is a very good cementitious material for CCUS / CCS well cementing. In addition, promoting the large-scale use of fly ash geopolymers can reduce the use of silicate cement and reduce carbon emissions, and can effectively improve the resource utilization of solid wastes such as fly ash. Therefore, it is of great significance to develop the application of geopolymers in CCUS / CCS well cementing.

[0005] Although geopolymers have good resistance to CO2 corrosion, their thickening time is difficult to control, which greatly limits their promotion and application on site. In recent years, the industry has formed a technical idea of ​​using reactive activators to replace sodium hydroxide to activate geopolymers and then control the thickening time. However, the geopolymers formed by this technology do not contain the activator sodium silicate (adding sodium silicate will make the thickening time of the geopolymer uncontrollable), resulting in insufficient SiO2 content in the geopolymer, resulting in low strength of the geopolymer. Summary of the invention

[0006] The object of the present invention is to provide a geopolymer cementing fluid system to solve the problem of insufficient compressive strength of geopolymers prepared by sodium carbonate and calcium hydroxide.

[0007] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0008] A geopolymer cementing fluid system, the components and weight ratios are as follows:

[0009] Cementitious material: 100 parts;

[0010] Sodium carbonate: 11-22 parts;

[0011] Calcium hydroxide: 7-14 parts;

[0012] Porous SiO2: 10-18 parts;

[0013] Porous Al2O3: 5-10 parts;

[0014] Retarder: 0.2-5 parts;

[0015] Water: 50-70 parts.

[0016] Preferably, the cementitious material is a mixture of fly ash, ultrafine fly ash and slag;

[0017] Calculated by weight ratio, fly ash: ultrafine fly ash: slag = 20-30: 40-60: 10-20.

[0018] Preferably, the fly ash has a silicon dioxide content greater than 40% and a specific surface area greater than 400m 2 / kg.

[0019] Preferably, the ultrafine fly ash has a silicon dioxide content greater than 40% and a specific surface area greater than 1500m 2 / kg.

[0020] Preferably, the porous SiO2 is a non-crystalline material;

[0021] The porous Al2O3 is a non-crystalline material.

[0022] Preferably, the porous SiO2 has a particle size of 0.01 microns to 5 microns.

[0023] Preferably, the porous SiO2 has a specific surface area of ​​≥400m 2 / g.

[0024] Preferably, the porous Al2O3 has a particle size of 0.01 microns to 5 microns.

[0025] Preferably, the porous Al2O3 has a specific surface area of ​​≥400m 2 / g.

[0026] Preferably, the retarder is a mixture of sodium gluconate and sodium ethylenediaminetetramethylenephosphonate;

[0027] By weight ratio, sodium gluconate: sodium ethylenediaminetetramethylenephosphonate = 30-50: 50-70. The mixture of the two has better high temperature resistance.

[0028] Based on the above technical solutions, the technical effects that can be achieved by the present invention are:

[0029] 1. Adding appropriate SiO2 materials to geopolymers is a reliable way to improve the strength of geopolymers. In addition to introducing enough SiO2, the dissolution rate of SiO2 in geopolymers is also the key to affecting the strength of geopolymers. The factors affecting the dissolution rate of SiO2 mainly include state (crystal or amorphous), particle size, specific surface area, etc. Generally speaking, the dissolution rate of small amorphous particles of SiO2 is faster in an alkaline environment. In addition, the specific surface area of ​​porous SiO2 is much higher than that of ordinary SiO2, so the dissolution rate of porous SiO2 is much higher than that of ordinary porous SiO2. Therefore, it is of great significance to develop high-strength geopolymers by introducing porous amorphous SiO2 into geopolymers. In addition, the insufficient aluminum content in geopolymers will also lead to the low strength due to the insufficient aluminum content in the product sodium aluminosilicate gel. For this reason, porous Al2O3 and porous SiO2 are also added in the present invention to synergistically enhance the strength of geopolymers.

[0030] 2. In the present invention, in order to ensure that the formed geopolymer has a high strength, fly ash and slag with large particle size, ultrafine fly ash with medium particle size, porous SiO2 and porous Al2O3 with small particle size are selected to form a particle gradation, so as to ensure sufficient compactness of the cementitious material, thereby improving the strength of the geopolymer. In terms of the dissolution rate of the cementitious material, ultrafine fly ash with medium particle size and slag with high calcium oxide content are conducive to the rapid dissolution of the cementitious material, thereby improving the strength of the geopolymer. In terms of the mineral composition of the geopolymer, the addition of porous SiO2 and porous Al2O3 can ensure that there are enough silicate ions and aluminum ions participating in the formation of the geopolymer in the early stage of the curing of the geopolymer, thereby improving the strength of the geopolymer.

[0031] 3. Based on particle grading technology, porous SiO2 and porous Al2O3 materials with high specific surface area, the strength of geopolymers is improved by increasing the density of geopolymers and regulating the material composition of geopolymers, so that their compressive strength at 70℃-120℃ for 24h can exceed 25MPa. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Example 1

[0036] 20 parts of fly ash, 60 parts of ultrafine fly ash, 20 parts of slag, 7 parts of calcium hydroxide, 11 parts of sodium carbonate, 14 parts of porous SiO2, 5 parts of porous Al2O3, 0.3 parts of sodium ethylenediaminetetramethylenephosphate, 0.3 parts of sodium gluconate, and 50 parts of water.

[0037] Example 2

[0038] 30 parts of fly ash, 55 parts of ultrafine fly ash, 15 parts of slag, 10 parts of calcium hydroxide, 15 parts of sodium carbonate, 16 parts of porous SiO2, 8 parts of porous Al2O3, 0.4 parts of sodium ethylenediaminetetramethylenephosphate, 0.2 parts of sodium gluconate, and 56 parts of water.

[0039] Example 3

[0040] 25 parts of fly ash, 55 parts of ultrafine fly ash, 20 parts of slag, 12 parts of calcium hydroxide, 17 parts of sodium carbonate, 18 parts of porous SiO2, 10 parts of porous Al2O3, 0.6 parts of sodium ethylenediaminetetramethylenephosphate, 0.4 parts of sodium gluconate, and 60 parts of water.

[0041] Comparative Example 1

[0042] 20 parts of fly ash, 60 parts of ultrafine fly ash, 20 parts of slag, 7 parts of calcium hydroxide, 11 parts of sodium carbonate, 0.3 parts of sodium ethylenediaminetetramethylenephosphate, 0.3 parts of sodium gluconate, and 50 parts of water.

[0043] Comparative Example 2

[0044] 30 parts of fly ash, 55 parts of ultrafine fly ash, 15 parts of slag, 10 parts of calcium hydroxide, 15 parts of sodium carbonate, 0.4 parts of sodium ethylenediaminetetramethylenephosphate, 0.2 parts of sodium gluconate, and 56 parts of water.

[0045] Comparative Example 3

[0046] 25 parts of fly ash, 55 parts of ultrafine fly ash, 20 parts of slag, 12 parts of calcium hydroxide, 17 parts of sodium carbonate, 0.6 parts of sodium ethylenediaminetetramethylenephosphate, 0.4 parts of sodium gluconate, and 60 parts of water.

[0047] Comparative Example 4

[0048] 25 parts of fly ash, 55 parts of ultrafine fly ash, 20 parts of slag, 12 parts of calcium hydroxide, 17 parts of sodium carbonate, 14 parts of porous SiO2, 0.6 parts of sodium ethylenediaminetetramethylenephosphate, 0.4 parts of sodium gluconate, and 60 parts of water.

[0049] Comparative Example 5

[0050] 25 parts of fly ash, 55 parts of ultrafine fly ash, 20 parts of slag, 12 parts of calcium hydroxide, 17 parts of sodium carbonate, 10 parts of porous Al2O3, 0.6 parts of sodium ethylenediaminetetramethylenephosphate, 0.4 parts of sodium gluconate, and 60 parts of water.

[0051] Test Case

[0052] The test method was carried out in accordance with the national standard GBT19139-2003 "Test methods for oil well cement" to prepare, thicken and test the geopolymer. The results are shown in Table 1.

[0053] Table 1 Experimental results Geopolymers 70℃ thickening time / min 70℃24h compressive strength / MPa Example 1 196 26 Example 2 231 28 Example 3 283 29 Comparative Example 1 207 16 Comparative Example 2 243 15 Comparative Example 3 294 18 Comparative Example 4 288 21 Comparative Example 5 289 23

[0054] According to the results in Table 1, at 70°C, the thickening time of Example 1, Example 2, and Example 3 is more than 3 hours, and the compressive strength at 70°C for 24 hours is also more than 25MPa, showing excellent performance. The thickening time of Comparative Example 1, Comparative Example 2, and Comparative Example 3 is also more than 3 hours, but the compressive strength at 70°C for 24 hours does not exceed 20MPa, indicating that the simultaneous addition of porous SiO2 and porous Al2O3 is very beneficial to improving the early strength of geopolymers. In Comparative Examples 4 and 5, the strength of porous SiO2 and porous Al2O3 added separately is not as good as the geopolymer system with porous SiO2 and porous Al2O3 added together, indicating that the two have obvious synergistic effects.

[0055] The geopolymer cementing fluid system provided in this embodiment has the advantages of adjustable thickening time and high early compressive strength, and can be well applied to the cementing operation of oil and gas wells to ensure the safety of cementing construction.

[0056] 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 cementing fluid system, characterized in that: The components and weight ratios are as follows: gelling material: 100 parts; Sodium carbonate: 11-22 parts; Calcium hydroxide: 7-14 parts; Porous SiO2: 10-18 parts; Porous Al2O3: 5-10 parts; Retarder: 0.2-5 parts; Water: 50-70 parts.

2. The geopolymer cementing fluid system according to claim 1, characterized in that: The cementitious material is a mixture of fly ash, ultrafine fly ash and slag; Calculated by weight ratio, fly ash: ultrafine fly ash: slag = 20-30: 40-60: 10-20.

3. The geopolymer cementing fluid system according to claim 2, characterized in that: The fly ash has a silicon dioxide content greater than 40% and a specific surface area greater than 400m 2 / kg.

4. The geopolymer cementing fluid system according to claim 2, characterized in that: The ultra-fine fly ash has a silicon dioxide content greater than 40% and a specific surface area greater than 1500m 2 / kg.

5. The geopolymer cementing fluid system according to claim 1, characterized in that: The porous SiO2 is a non-crystalline material; The porous Al2O3 is a non-crystalline material.

6. The geopolymer cementing fluid system according to claim 1, characterized in that: The porous SiO2 has a particle size of 0.01 micron to 5 microns.

7. The geopolymer cementing fluid system according to claim 1, characterized in that: The porous SiO2 has a specific surface area of ​​≥400m 2 / g.

8. The geopolymer cementing fluid system according to claim 1, characterized in that: The porous Al2O3 has a particle size of 0.01 micron to 5 microns.

9. The geopolymer cementing fluid system according to claim 1, characterized in that: The porous Al2O3 has a specific surface area of ​​≥400m 2 / g.

10. The geopolymer cementing fluid system according to claim 1, characterized in that: The retarder is a mixture of sodium gluconate and sodium ethylenediaminetetramethylenephosphonate; In terms of weight ratio, sodium gluconate: sodium ethylenediaminetetramethylenephosphonate = 30-50: 50-70.