Self-repairing plugging material and preparation method thereof

Abstract

This invention relates to the field of cement-based engineering materials technology, and in particular to a self-healing plugging material and its preparation method. The material uses calcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride as raw materials to form a heat-resistant self-healing material. Hollow polyvinyl alcohol fiber is used as a carrier, and the outer layer is treated with a silane coupling agent to prepare the self-healing fiber. Combined with calcium carbonate whiskers, the plugging material is toughened, its crack resistance is improved, and microcracks are self-repaired. It can be used for high-temperature cementing and plugging in environments of 150-180℃.

Description

Technical Field

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

[0002] During oil well construction, there is a gap between the oil and gas well and the casing. Cement slurry, which has a sealing effect, is often used to fill and seal the gap. Cementing has become an important process in oil and gas well development. As a brittle material, cement-based materials are inevitably at risk of developing micro-cracks due to external loads and corrosive media. Long-term erosion can easily lead to the destruction of the cement sheath, resulting in the failure of the sealing.

[0003] To address the cracking problem of cement sheaths, current research is increasingly shifting from improving the toughness of cement-based plugging materials to developing self-healing oil well cement materials that can be used for secondary sealing and plugging. Based on the self-healing mechanism, commonly used self-healing technologies in the current field can be categorized into virgin self-healing materials, microcapsule self-healing materials, water-absorbing / oil-expanding self-healing materials, and microbial self-healing materials.

[0004] Prior art CN103468231A discloses a silane coupling agent-coated self-healing agent, composed of 100-130 parts by weight of active minerals and 0.2-7.0 parts by weight of silane coupling agent. CN111072328A discloses a self-healing material comprising the following components: cement, nano-silica, sodium silicate, magnesium oxide, fumaric acid, dispersant, fluid loss reducing agent, and water. CN114452907A discloses a microcapsule for temperature control and self-healing of cementing rings, comprising a capsule core and two layers of capsule walls surrounding the capsule core; the capsule core comprises: a temperature-controlling core material composed of a mixture of mixed alkanes and stearic acid, and a self-healing core material composed of a mixture of epoxy resin, fumed silica, graphene, and boron trichloride; the inner layer of the capsule wall is made of calcium carbonate, and the outer layer is made of stearic acid. CN117902849A discloses a self-healing material mainly prepared from the following raw materials: 2-acrylamide-2-methylpropanesulfonic acid, basic bentonite, sodium carboxymethyl cellulose, and a crystal nucleation material, wherein the crystal nucleation material is a sodium silicate crystal nucleation material. CN118290052A discloses a self-healing agent for oil well cement, wherein the self-healing agent includes at least surface-sulfonated thermoplastic elastomer particles, wherein the thermoplastic elastomer particles include rubber, polyolefin, and inorganic fillers. However, existing self-healing technologies still have drawbacks such as poor repair effect and incompatibility with cement-based plugging materials. Furthermore, research on the self-healing effect of plugging materials under high-temperature environments is insufficient, especially for inorganic self-healing materials, which mostly rely on secondary pozzolanic materials such as fly ash and slag for self-healing, resulting in a slow effect. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a self-healing plugging material. It uses calcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride as raw materials to form a heat-resistant self-healing material. Hollow polyvinyl alcohol fiber is used as a carrier, and the outer layer is treated with a silane coupling agent to prepare the self-healing fiber. Combined with calcium carbonate whiskers, this toughens the plugging material, improves its crack resistance, and enables self-repair of microcracks. It can be used for high-temperature cementing and plugging in environments of 150-180℃.

[0006] Specifically, the self-healing and leak-sealing material of the present invention is composed of the following raw materials in parts by weight: 100-120 parts cement, 10-12 parts weight-reducing agent, 5-7 parts dispersant, 5-6 parts water-loss reducing agent, 2-5 parts retarder, 1-2 parts suspending agent, 0.4-0.5 parts defoamer, 1-3 parts calcium carbonate whiskers, 4-6 parts self-healing fiber, and 50-55 parts water.

[0007] The self-healing plugging material of this invention still uses cement as a cementing material. To overcome its poor toughness, calcium carbonate whiskers and self-healing fibers are added, which play a reinforcing role in the formed cementing sheath and resist the propagation of microcracks.

[0008] Preferably, the self-healing fiber has a three-layer structure: the outer layer is a silane coupling agent modified layer, the middle layer is a hollow polyvinyl alcohol fiber, and the inner layer is a heat-resistant self-healing material.

[0009] The self-healing fiber of this invention uses hollow polyvinyl alcohol fiber as a carrier. It first plays a synergistic toughening role with calcium carbonate whiskers. When microcracks are generated in the cement sheath, the hollow polyvinyl alcohol fiber fails first at high temperature. The heat-resistant self-healing material loaded in it undergoes rapid hydration upon contact with water to plug the microcracks and prevent them from continuing to develop. By treating the surface of the hollow polyvinyl alcohol fiber with a silane coupling agent, the bonding force between the fiber and the cement sheath is improved.

[0010] Preferably, the preparation process of the heat-resistant self-healing material is as follows:

[0011] a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume.

[0012] b. Mix the calcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of (1-1.2):(0.9-1.1):(0.2-0.3):(1-1.1) until homogeneous to obtain the final product.

[0013] This invention uses calcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride as heat-resistant self-healing materials. When exposed to water, these materials rapidly generate a large amount of heat-resistant 518 phase and some magnesium hydroxide, exhibiting good adhesion, a micro-expansion effect, and rapid repair of microcracks. Furthermore, under high-temperature conditions, the modified silica fume and magnesium hydroxide generate hydrated magnesium silicate, which replenishes the hydration products of the 518 phase, jointly improving its mechanical properties and resistance to high temperature and humidity, resulting in excellent self-healing performance.

[0014] Preferably, the cement is Grade G oil well cement.

[0015] Preferably, the weight-reducing agent is at least one of hollow glass microspheres and closed-cell expanded perlite.

[0016] Preferably, the dispersant is at least one of Weihui GD-1, formaldehyde-acetone condensate, and SXY.

[0017] Preferably, the water loss reducing agent is at least one of G33S, DRF-120L, and BXF-200L.

[0018] Preferably, the retarder is at least one of citric acid, borax, sodium hydroxyethylidene diphosphonate, potassium hydroxyethylidene diphosphonate, and sodium ethylenediaminetetramethylene phosphate.

[0019] Preferably, the suspending agent is at least one of hydroxyethyl cellulose, hydroxypropyl methylcellulose ether, and xanthan gum.

[0020] Preferably, the defoamer is an organosilicone defoamer.

[0021] Preferably, the calcium carbonate whiskers have a diameter of 0.5-2 μm and a length of 20-80 μm. Experimental studies have shown that the combination of calcium carbonate whiskers and self-healing fibers in this invention exhibits better results than combinations of other fibers.

[0022] Preferably, the calcined magnesium oxide is obtained by calcining magnesium carbonate at 1300-1400℃, and the lightly calcined magnesium oxide is obtained by calcining magnesium carbonate at 950-1100℃.

[0023] This invention also relates to a method for preparing the above-mentioned self-healing and leak-sealing 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.

[0024] Preferably, the preparation method of the above-mentioned self-healing and leak-sealing material includes the following steps:

[0025] 1) Weigh each ingredient according to its weight.

[0026] 2) Mix cement, lightweight agent, dispersant, water loss reducer, and calcium carbonate whiskers evenly to obtain the main material.

[0027] 3) Dissolve the retarder, suspending agent, and defoamer in water to obtain a liquid mixture.

[0028] 4) Add the liquid material to the main material and mix well to obtain a slurry.

[0029] 5) Add self-healing fibers to the slurry and mix well to obtain the final product.

[0030] This invention has the following technical advantages:

[0031] 1. This invention utilizes calcium carbonate whiskers and self-healing fibers to synergistically improve the toughness of cementing self-healing plugging materials.

[0032] 2. The self-healing fiber of this invention contains highly active heat-resistant self-healing materials. Under high temperature and high humidity conditions, it generates a large amount of 518 phase and hydrated magnesium silicate, and produces a small amount of magnesium hydroxide. It exhibits high adhesion, good heat and humidity resistance, and rapid self-healing effect.

[0033] 3. The self-healing plugging material of the present invention has good high-temperature resistance and self-healing effect, and can be used for high-temperature cementing and plugging in environments of 150-180℃. Detailed Implementation

[0034] To characterize the technical effect of the present invention, a leak-sealing material was prepared and its self-healing effect was tested. The test method was as follows: after the specimen was formed, it was cured at 180°C for 48 hours. Six specimens were taken to test the compressive strength after 48 hours. Another six specimens were kept under a pressure of 20MPa for 5 minutes and then cured at 180°C for 7 days to test the compressive strength. The specimens were kept moist during the curing process.

[0035] During the experiment, G-grade oil well cement was used as the cement, hollow glass microspheres were used as the weight-reducing agent, Weihui GD-1 was used as the dispersant, G33S was used as the fluid loss reducing agent, sodium ethylenediaminetetramethylene phosphate was used as the retarder, hydroxypropyl methylcellulose ether was used as the suspending agent, and organosilicon defoamer was used as the defoamer. The calcined magnesium oxide was obtained by calcining magnesium carbonate at 1350℃, and the lightly calcined magnesium oxide was obtained by calcining magnesium carbonate at 1000℃. Example

[0036] The leak-sealing material is composed of the following raw materials in parts by weight: 120 parts cement, 12 parts lightweight agent, 6 parts dispersant, 6 parts water loss reducer, 4 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 2 parts calcium carbonate whiskers, 6 parts self-healing fiber, and 54 parts water.

[0037] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material.

[0038] The preparation process of the heat-resistant self-healing material is as follows:

[0039] a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume.

[0040] b. Mix the calcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of 1.1:1:0.3:1 until homogeneous to obtain the final product.

[0041] The test results showed that the compressive strength of the specimen was 27.3 MPa after 48 hours and 24.6 MPa after 7 days of pressure curing. Example

[0042] The leak-sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts lightweight agent, 5 parts dispersant, 5.5 parts water loss reducer, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 3 parts calcium carbonate whiskers, 5 parts self-healing fiber, and 54 parts water.

[0043] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material.

[0044] The preparation process of the heat-resistant self-healing material is as follows:

[0045] a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume.

[0046] b. Mix the recalcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of 1:1:0.3:1.1 until homogeneous to obtain the final product.

[0047] The test results showed that the compressive strength of the specimen was 26.6 MPa after 48 hours and 23.5 MPa after 7 days of pressure curing.

[0048] Comparative Example 1

[0049] The sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts lightening agent, 5 parts dispersant, 5.5 parts water loss reducer, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 3 parts calcium carbonate whiskers, 5 parts polyvinyl alcohol fiber, and 54 parts water.

[0050] The test results showed that the compressive strength of the specimen was 25.7 MPa after 48 hours and 10.4 MPa after 7 days of pressure curing.

[0051] Comparative Example 2

[0052] The leak-sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts weight-reducing agent, 5 parts dispersant, 5.5 parts water-loss reducing agent, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 5 parts self-healing fiber, and 54 parts water.

[0053] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material.

[0054] The preparation process of the heat-resistant self-healing material is as follows:

[0055] a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume.

[0056] b. Mix the recalcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of 1:1:0.3:1.1 until homogeneous to obtain the final product.

[0057] The test results showed that the compressive strength of the specimen was 21.4 MPa after 48 hours and 15.8 MPa after 7 days of pressure curing.

[0058] Comparative Example 3

[0059] The leak-sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts lightweight agent, 5 parts dispersant, 5.5 parts water loss reducer, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 3 parts calcium sulfate whiskers, 5 parts self-healing fiber, and 54 parts water.

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

[0061] The preparation process of the heat-resistant self-healing material is as follows:

[0062] a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume.

[0063] b. Mix the recalcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of 1:1:0.3:1.1 until homogeneous to obtain the final product.

[0064] The test results showed that the compressive strength of the specimen was 23.2 MPa after 48 hours and 17.1 MPa after 7 days of pressure curing.

[0065] Comparative Example 4

[0066] The leak-sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts lightweight agent, 5 parts dispersant, 5.5 parts water loss reducer, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 3 parts calcium carbonate whiskers, 5 parts self-healing fiber, and 54 parts water.

[0067] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material.

[0068] The preparation process of the heat-resistant self-healing material is as follows:

[0069] The calcined magnesium oxide, lightly calcined magnesium oxide, and magnesium chloride are mixed evenly in a mass ratio of 1:1:1.1 to obtain the final product.

[0070] The test results showed that the compressive strength of the specimen was 25.5 MPa after 48 hours and 18.3 MPa after 7 days of pressure curing.

[0071] Comparative Example 5

[0072] The leak-sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts lightweight agent, 5 parts dispersant, 5.5 parts water loss reducer, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 3 parts calcium carbonate whiskers, 5 parts self-healing fiber, and 54 parts water.

[0073] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material.

[0074] The preparation process of the heat-resistant self-healing material is as follows:

[0075] The calcined magnesium oxide, lightly calcined magnesium oxide, silica fume, and magnesium chloride are mixed evenly in a mass ratio of 1:1:0.3:1.1 to obtain the final product.

[0076] The test results showed that the compressive strength of the specimen was 24.9 MPa after 48 hours and 17.8 MPa after 7 days of pressure curing.

[0077] Comparative Example 6

[0078] The leak-sealing material is composed of the following raw materials in parts by weight: 110 parts cement, 11 parts lightweight agent, 5 parts dispersant, 5.5 parts water loss reducer, 3 parts retarder, 1.5 parts suspending agent, 0.4 parts defoamer, 3 parts calcium carbonate whiskers, 5 parts self-healing fiber, and 54 parts water.

[0079] The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material.

[0080] The preparation process of the heat-resistant self-healing material is as follows:

[0081] a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume.

[0082] b. Mix the recalcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of 2:0.3:1.1 until homogeneous to obtain the final product.

[0083] The test results showed that the compressive strength of the specimen was 25.0 MPa after 48 hours and 15.6 MPa after 7 days of pressure curing.

[0084] 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 self-healing leak-sealing material, characterized in that, It is composed of the following raw materials in parts by weight: 100-120 parts cement, 10-12 parts lightweight agent, 5-7 parts dispersant, 5-6 parts water loss reducer, 2-5 parts retarder, 1-2 parts suspending agent, 0.4-0.5 parts defoamer, 1-3 parts calcium carbonate whiskers, 4-6 parts self-healing fiber, and 50-55 parts water. The self-healing fiber has a three-layer structure: an outer layer modified with a silane coupling agent, a middle layer of hollow polyvinyl alcohol fiber, and an inner layer of heat-resistant self-healing material. The preparation process of the heat-resistant self-healing material is as follows: a. Place the densified silica fume in a calcium nitrate-triethanolamine solution, sonicate, filter, and dry to obtain modified silica fume. b. Mix the calcined magnesium oxide, lightly calcined magnesium oxide, modified silica fume, and magnesium chloride in a mass ratio of (1-1.2):(0.9-1.1):(0.2-0.3):(1-1.1) until homogeneous to obtain the final product.

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

3. The self-healing leak-sealing material according to claim 1, characterized in that, The weight-reducing agent is at least one of hollow glass microspheres and closed-cell expanded perlite.

4. The self-healing leak-sealing material according to claim 1, characterized in that, The dispersant is one of formaldehyde-acetone condensate and SXY.

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

6. The self-healing leak-sealing material according to claim 1, characterized in that, The retarder is at least one of citric acid, borax, sodium hydroxyethylidene diphosphonate, potassium hydroxyethylidene diphosphonate, and sodium ethylenediaminetetramethylene phosphate.

7. The self-healing leak-sealing material according to claim 1, characterized in that, The suspending agent is at least one of hydroxyethyl cellulose, hydroxypropyl methylcellulose ether, and xanthan gum.

8. The self-healing leak-sealing material according to claim 1, characterized in that, The defoamer is an organosilicone defoamer.

9. The self-healing leak-sealing material according to claim 1, characterized in that, The recalcined magnesium oxide is obtained by calcining magnesium carbonate at 1300-1400℃, and the lightly calcined magnesium oxide is obtained by calcining magnesium carbonate at 950-1100℃.

10. The method for preparing the self-healing leak-sealing material according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Weigh each raw material according to its weight proportions. (2) Mix cement, lightweight agent, dispersant, water loss reducer, and calcium carbonate whiskers evenly to obtain the main material. (3) Dissolve the retarder, suspending agent, and defoamer in water 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.