Cement-based well cementation self-repairing material and preparation method thereof

Abstract

The present application relates to the technical field of cement-based engineering materials, and particularly relates to a cement-based well cementing self-repairing material and a preparation method thereof, which adopts steel slag micro-powder, carbide slag and crystal silicon cutting waste to prepare an active self-repairing material through double-stage calcination, and then loads the active self-repairing material to hollow fibers, and then adopts a silane coupling agent to treat to prepare a self-repairing fiber, which is used for the cement-based well cementing self-repairing material, and realizes self-repairing of the well cementing material in a water-rich CO2-containing environment.

Description

Technical Field

[0001] This invention relates to the field of cement-based engineering materials technology, and in particular to a cement-based self-healing cementing material and its preparation method. Background Technology

[0002] Cement cementing is the process of injecting cement slurry into the annular space between the casing and the wellbore. The hardened cement ring can seal the formation, prevent fluid from flowing between layers, effectively support the formation and casing, and protect the casing from corrosion.

[0003] However, during the service of oil wells, cement sheaths are often damaged by the external environment, resulting in microcracks that compromise the integrity of the seal. Repairing damaged cement sheaths is very complex, and in recent years, self-healing materials have been initially developed and researched.

[0004] Existing technologies CN103074043A discloses a cementing slurry additive, mainly prepared by uniformly mixing modified resin, calcium carbonate, active silica, alkyl silane, etc. CN103952129A discloses a self-repairing fluid for oil and gas well cementing sheaths, composed of inorganic water-based cement sealing and waterproofing agent, triisopropanolamine, calcium acetate, penetrant JFC, and water. CN107522422A discloses a self-repairing agent for oil well cement, including: skeleton material, grafted functional monomer, multifunctional group radiation sensitizer, and release agent. CN109912792A discloses a self-repairing material for oil well cement stone that expands upon contact with water, composed of polyethylene glycol 400, DL... A self-repairing material for cementing oil and gas wells is prepared by tartaric acid and concentrated sulfuric acid. CN111039591A discloses a self-repairing material for cementing oil and gas wells, the raw materials of which include ethylene-isoprene-styrene block copolymer, precursor, coupling agent, water, and solvent. CN116462798A discloses a nanocomposite hydrogel for repairing microcracks in cement sheaths. The preparation method is as follows: a certain amount of nanomaterials are slowly added to deionized water and stirred to obtain a uniform mixture; at least two monomers are added to the mixture, including anionic monomers, functional monomers that generate anions after hydrolysis, and functional monomers that generate cationic groups after hydrolysis in the presence of acidic gas; then a crosslinking agent and an initiator are added, and the nanocomposite hydrogel is obtained after reaction.

[0005] Existing technologies for repair materials focus on developing organic self-healing materials. However, oil wells are often accompanied by aquatic environments, and some oil and gas wells also contain CO2. Once the cement sheath cracks, the acidic environment formed by CO2 dissolving in water will lead to further erosion of the cement sheath.

[0006] There is very little research on self-healing cementing materials in CO2 environments. CN118026608A discloses a low-to-medium temperature self-healing cement slurry in the presence of carbon dioxide, which includes silicate cement, fluid loss reducer, dispersant, corrosion inhibitor, and CO2 self-healing agent. However, the CO2 self-healing agent has low activity. CN118256207A discloses a CO2-compatible self-compensating chemical recrystallization plugging agent, which includes sodium silicate, barite, dispersant, corrosion inhibitor, and water. The corrosion inhibitor is a CO2-resistant corrosion inhibitor.

[0007] The reuse of industrial solid waste is also a research hotspot, but its application in well cementing repair has not yet been studied in depth. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a cement-based self-healing cementing material. The active self-healing material is prepared by two-stage calcination of steel slag powder, carbide slag, and crystalline silicon cutting waste. This material is then loaded onto hollow fibers and treated with a silane coupling agent to obtain self-healing fibers. These fibers are used in cement-based self-healing cementing materials to achieve self-healing of cementing materials in water-rich, CO2-containing environments.

[0009] Specifically, the cement-based self-healing cementing material of the present invention is composed of the following raw materials in parts by weight: 95-110 parts cement, 20-25 parts rice husk ash, 3-7 parts fluid loss reducer, 3-5 parts dispersant, 2-4 parts retarder, 0.3-0.6 parts defoamer, 50-55 parts water, 5-8 parts self-healing fiber, 0.3-0.5 parts micron-sized SAP particles, and 0.8-1 parts carboxymethyl cellulose.

[0010] This invention uses cement as the main cementitious material and adds water loss reducers, dispersants, retarders, and defoamers as additives in existing technologies. To enable the self-healing fibers to exert their self-healing effect in a water-rich and CO2-containing environment, micron-sized SAP particles are added as water storage additives. However, since SAP particles easily release water under high pressure after absorbing water in cement slurry, this invention has adjusted the formula through extensive experiments, adding rice husk ash and carboxymethyl cellulose to adjust the rheological properties of the slurry, thereby meeting the construction requirements.

[0011] Preferably, the self-healing fiber has a three-layer structure: an outer layer is a silane coupling agent modified layer, a middle layer is a hollow fiber body layer, and an inner layer is an active self-healing material.

[0012] This invention uses hollow fiber as the loading material for active self-healing material. The fiber material can improve the crack resistance of cement ring. When microcracks occur in cement ring, the fiber material breaks and breaks down. External water and CO2, as corrosive agents, penetrate into cement ring and come into contact with the active self-healing material, causing it to quickly hydrate and fill the microcracks, preventing further erosion of cement ring. By setting a silane coupling agent modification layer, the interfacial bonding force between fiber and cement-based material can be improved.

[0013] Preferably, the preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of (2-3):(4-6):(0.5-0.8), pre-calcined at 600-800℃ for 2-3 hours, then calcined at 1350-1400℃ for 2-4 hours, rapidly cooled, ground, and sieved to obtain the final product.

[0014] Steel slag powder is a waste product of the steelmaking industry. Its composition is similar to that of cement clinker, but it has lower activity and is rich in free calcium oxide. Calcium carbide slag is an industrial byproduct of calcium carbide-to-acetylene production, and its main component is calcium hydroxide. Wafer dicing generates a large amount of waste, which is rich in high-purity silicon powder. This invention uses steel slag powder, calcium carbide slag, and crystalline silicon dicing waste to prepare a highly active self-healing material through a two-stage calcination process. This material has high activity and fast hydration. It can generate a large amount of calcium silicate and calcium silicate in the oil well environment. Furthermore, the humid CO2 environment promotes the formation of nano-calcium carbonate in the active self-healing material, which together block microcracks and prevent further expansion of microcracks. Moreover, the active self-healing material of this invention has high activity and fast hydration response, and can perform self-repair in the early stage of microcrack expansion, avoiding damage to the cement ring.

[0015] Preferably, the crystalline silicon cutting waste comes from at least one of silicon carbide cutting process waste and diamond wire cutting process waste.

[0016] Preferably, the particle size of the active self-healing material is ≤5μm.

[0017] Preferably, the hollow fiber is at least one of hollow polypropylene fiber, hollow polyethylene fiber, and hollow carbon fiber.

[0018] Preferably, the rapid cooling is achieved by air cooling.

[0019] Preferably, the cement is Grade G oil well cement.

[0020] Preferably, the water loss reducing agent is at least one of G33S, DRF-120L, and BXF-200L.

[0021] Preferably, the dispersant is at least one of Weihui GD-1 and SXY.

[0022] Preferably, the retarder is at least one of tartaric acid, borax, citric acid, potassium hydroxyethylidene diphosphonate, and sodium ethylenediaminetetramethylene phosphate.

[0023] Preferably, the defoamer is an organosilicone defoamer.

[0024] This invention also relates to a method for preparing the above-mentioned cement-based self-healing cementing material, specifically including the following steps: weighing each raw material according to the weight parts, mixing them evenly in steps, and thus obtaining the material.

[0025] Preferably, the preparation method of the above-mentioned cement-based self-healing cementing material includes the following steps:

[0026] 1) Weigh each ingredient according to its weight.

[0027] 2) Mix cement, rice husk ash, water loss reducer, dispersant, micron-sized SAP particles, and carboxymethyl cellulose evenly to obtain the main material.

[0028] 3) Mix the retarder, defoamer, and water thoroughly to obtain a liquid mixture.

[0029] 4) Add the liquid material to the main material and mix well to obtain a slurry.

[0030] 5) Add self-healing fibers to the slurry and mix well to obtain the final product.

[0031] This invention also relates to the application of the above-mentioned cement-based self-healing cementing material in cementing engineering.

[0032] This invention has the following technical advantages:

[0033] 1. The self-healing fibers prepared in this invention not only improve the toughness of cementing materials but also achieve a self-healing effect.

[0034] 2. This invention incorporates micron-sized SAP particles, which store water in a humid environment, providing a hydration environment for the self-healing process.

[0035] 3. This invention adds rice husk ash and carboxymethyl cellulose to adjust the rheological properties of the cementing slurry, reduce water loss, and ensure smooth construction.

[0036] 4. This invention utilizes industrial solid waste through a two-stage calcination process to prepare active self-healing materials. These materials exhibit high activity, rapid hydration response, cost reduction, waste utilization, and increased added value from industrial solid waste.

[0037] 5. The cement-based self-healing cementing material of the present invention can realize the self-healing of cementing materials in water-rich and CO2-containing environments. Detailed Implementation

[0038] To characterize the technical effect of this invention, cement-based cementing materials were prepared and their performance was tested. The water loss test temperature was 120℃ and the pressure was 6.9MPa. The self-healing effect was tested by compressive strength test. The specific process was as follows: after the specimen was formed, it was cured at 150℃ for 48 hours. Six specimens were taken to test the compressive strength after 48 hours. Another six specimens were kept under a pressure of 30MPa for 5 minutes and then placed at 150℃. CO2 gas was introduced for curing for 7 days, and the compressive strength was tested. The specimens were kept moist during the curing process.

[0039] During the experiment, G-grade oil well cement was selected as the cement, G33S was selected as the fluid loss reducing agent, Weihui GD-1 was selected as the dispersant, sodium ethylenediaminetetramethylidene phosphate was selected as the retarder, organosilicon defoamer was selected as the defoamer, and diamond wire cutting process waste was selected as the crystalline silicon cutting waste.

[0040] Example 1

[0041] The cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts rice husk ash, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, 53 parts water, 6 parts self-healing fiber, 0.4 parts micron-sized SAP particles, and 1 part carboxymethyl cellulose, wherein SAP is a superabsorbent polymer, the same below.

[0042] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0043] The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of 2:6:0.6, heated to 750℃ for pre-calcination for 2 hours, then heated to 1400℃ for high-temperature calcination for 3 hours, rapidly cooled, ground, and sieved to obtain particles ≤5μm.

[0044] Tests showed a water loss of 42 mL, a compressive strength of 40.3 MPa after 48 hours, and a compressive strength of 34.6 MPa after 7 days of pressure curing.

[0045] Example 2

[0046] The cement-based cementing material is composed of the following raw materials in parts by weight: 105 parts cement, 20 parts rice husk ash, 6 parts fluid loss reducer, 5 parts dispersant, 3 parts retarder, 0.3 parts defoamer, 53 parts water, 7 parts self-healing fiber, 0.3 parts micron-sized SAP particles, and 0.9 parts carboxymethyl cellulose.

[0047] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0048] The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of 3:5:0.7, heated to 750℃ for pre-calcination for 2.5 hours, and then heated to 1400℃ for high-temperature calcination for 3 hours. After rapid cooling, the mixture is ground and sieved to obtain particles ≤5μm.

[0049] The test results showed a water loss of 41 mL, a compressive strength of 41.1 MPa after 48 hours, and a compressive strength of 35.3 MPa after 7 days of pressure curing.

[0050] Comparative Example 1

[0051] Cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts fly ash, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, and 53 parts water.

[0052] Tests showed a water loss of 49 mL, a compressive strength of 38.4 MPa after 48 hours, and a compressive strength of 17.2 MPa after 7 days of pressure curing.

[0053] Comparative Example 2

[0054] The cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts silica fume, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, 53 parts water, 6 parts self-healing fiber, 0.4 parts micron-sized SAP particles, and 1 part carboxymethyl cellulose.

[0055] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0056] The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of 2:6:0.6, heated to 750℃ for pre-calcination for 2 hours, then heated to 1400℃ for high-temperature calcination for 3 hours, rapidly cooled, ground, and sieved to obtain particles ≤5μm.

[0057] Tests showed a water loss of 56 mL, a compressive strength of 34.2 MPa after 48 hours, and a compressive strength of 28.5 MPa after 7 days of pressure curing.

[0058] Comparative Example 3

[0059] Cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts fly ash, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, 53 parts water, and 6 parts self-healing fiber.

[0060] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0061] The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of 2:6:0.6, heated to 750℃ for pre-calcination for 2 hours, then heated to 1400℃ for high-temperature calcination for 3 hours, rapidly cooled, ground, and sieved to obtain particles ≤5μm.

[0062] The test results showed a water loss of 47 mL, a compressive strength of 38.9 MPa after 48 hours, and a compressive strength of 28.8 MPa after 7 days of pressure curing.

[0063] Comparative Example 4

[0064] Cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts rice husk ash, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, 53 parts water, 6 parts self-healing fiber, 0.4 parts micron-sized SAP particles, and 1 part carboxymethyl cellulose.

[0065] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0066] The preparation process of the active self-healing material is as follows: slag powder, alkali slag, and silica fume are mixed evenly in a mass ratio of 2:6:0.6, heated to 750℃ for pre-calcination for 2 hours, then heated to 1400℃ for high-temperature calcination for 3 hours, rapidly cooled, ground, and sieved to obtain particles ≤5μm.

[0067] Tests showed a water loss of 43 mL, a compressive strength of 40.6 MPa after 48 hours, and a compressive strength of 25.7 MPa after 7 days of pressure curing.

[0068] Comparative Example 5

[0069] Cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts rice husk ash, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, 53 parts water, 6 parts self-healing fiber, 0.4 parts micron-sized SAP particles, and 1 part carboxymethyl cellulose.

[0070] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0071] The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of 2:6:0.6, heated to 1400℃ and calcined for 3.5 hours, then rapidly cooled, ground, and sieved to obtain particles ≤5μm.

[0072] The test results showed a water loss of 41 mL, a compressive strength of 39.5 MPa after 48 hours, and a compressive strength of 27.6 MPa after 7 days of pressure curing.

[0073] Comparative Example 6

[0074] Cement-based cementing material is composed of the following raw materials in parts by weight: 100 parts cement, 22 parts rice husk ash, 5 parts fluid loss reducer, 4 parts dispersant, 2 parts retarder, 0.4 parts defoamer, 53 parts water, 6 parts self-healing fiber, 0.4 parts micron-sized SAP particles, and 1 part carboxymethyl cellulose.

[0075] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow carbon fiber matrix, and an inner layer of active self-healing material.

[0076] The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and silica fume are mixed evenly in a mass ratio of 2:6:0.6, heated to 1100℃ and calcined for 3 hours, then rapidly cooled, ground, and sieved to obtain particles ≤5μm.

[0077] The test results showed a water loss of 43 mL, a compressive strength of 40.2 MPa after 48 hours, and a compressive strength of 24.4 MPa after 7 days of pressure curing.

[0078] Based on the results of the embodiments and comparative examples, the present invention uses a pressure of 30 MPa, which causes microcracks to begin to form inside the specimen, but does not lead to complete destruction of the specimen. After curing, the self-healing material can actively repair the microcracks.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions 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 cement-based self-healing cementing material, characterized in that, It is composed of the following raw materials in parts by weight: 95-110 parts cement, 20-25 parts rice husk ash, 3-7 parts water loss reducer, 3-5 parts dispersant, 2-4 parts retarder, 0.3-0.6 parts defoamer, 50-55 parts water, 5-8 parts self-healing fiber, 0.3-0.5 parts micron-sized SAP particles, and 0.8-1 parts carboxymethyl cellulose. The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow fiber matrix, and an inner layer of active self-healing material. The preparation process of the active self-healing material is as follows: steel slag powder, carbide slag, and crystalline silicon cutting waste are mixed evenly in a mass ratio of (2-3):(4-6):(0.5-0.8), pre-calcined at 600-800℃ for 2-3 hours, then calcined at 1350-1400℃ for 2-4 hours, rapidly cooled, ground, and sieved to obtain the final product.

2. The cement-based self-healing cementing material according to claim 1, characterized in that, The cement is Grade G oil well cement.

3. The cement-based self-healing cementing material according to claim 1, characterized in that, The water loss reducing agent is at least one of G33S, DRF-120L, and BXF-200L.

4. The cement-based self-healing cementing material according to claim 1, characterized in that, The dispersant is at least one of Weihui GD-1 and SXY.

5. The cement-based self-healing cementing material according to claim 1, characterized in that, The retarder is at least one of tartaric acid, borax, citric acid, potassium hydroxyethylidene diphosphonate, and sodium ethylenediaminetetramethylene phosphate.

6. The cement-based self-healing cementing material according to claim 1, characterized in that, The defoamer is an organosilicone defoamer.

7. The cement-based self-healing cementing material according to claim 1, characterized in that, The hollow fiber is at least one of hollow polypropylene fiber, hollow polyethylene fiber, and hollow carbon fiber.

8. The cement-based self-healing cementing material according to claim 1, characterized in that, The active self-healing material has a particle size ≤5μm.

9. The method for preparing the cement-based self-healing cementing material according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Weigh each raw material according to the weight parts; (2) Mix cement, rice husk ash, water loss reducer, dispersant, micron-sized SAP particles, and carboxymethyl cellulose evenly to obtain the main material; (3) Mix the retarder, defoamer and water evenly to obtain a liquid; (4) Add the liquid material to the main material and mix well to obtain a slurry; (5) Add self-healing fibers to the slurry and mix evenly to obtain the final product.

10. The application of the cement-based self-healing cementing material according to any one of claims 1-8 in cementing engineering.