A leakproof material, a leakproof cement slurry and a method for plugging leaks

Abstract

The application provides a leakproof material, a leakproof cement slurry and a leak stopping method. The leakproof material comprises the following components in percentage by mass: 30-60% of high-temperature-resistant fibers, 20-40% of high-temperature-resistant sealants and 10-30% of nano-scale additives. The leakproof material has excellent high-temperature stability, sealing performance and leakproof effect.

Description

Technical Field

[0001] This invention belongs to the field of oil drilling cementing technology, specifically relating to a leak-proof material, a leak-proof cement slurry, and a leak-sealing method thereof. Background Technology

[0002] As deep oil and gas resource development deepens, drilling depths increase, leading to higher bottom-hole temperatures. In environments exceeding 200°C, the long-term strength of existing cement slurries rapidly declines, compromising cementing quality and reducing well sealing quality and performance, posing a serious threat to the safe production and long-term operation of oilfields. Therefore, providing a leak-proof material that simultaneously possesses excellent leak-proof properties, sealing performance, and high-temperature stability is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0003] This invention provides a leak-proof material that simultaneously possesses excellent high-temperature stability, sealing performance, and leak-proof effect.

[0004] The present invention also provides a leak-proof cement grout, which has excellent leak-proof properties, sealing properties and high-temperature stability.

[0005] The present invention also provides a leak-sealing method, which can ensure that the leak-proof cement slurry forms an effective sealing layer, effectively filling and sealing the leak area.

[0006] In a first aspect, the present invention provides a leak-proof material, comprising, by weight percentage, the following components: 30%-60% high-temperature resistant fiber, 20%-40% high-temperature resistant sealant, and 10%-30% nano-grade additives.

[0007] The leak-proof material as described above, wherein the high-temperature resistant fiber includes at least one of carbon fiber, glass fiber, and asbestos fiber.

[0008] The leak-proof material as described above, wherein the nanoscale additives include nano-silica and / or nano-calcium sulfate whiskers.

[0009] The leak-proof material described above, wherein the high-temperature resistant sealant comprises at least one of sodium alginate gel, polyacrylamide gel, polyacrylonitrile gel, and polyvinyl alcohol gel; and / or,

[0010] The nanoscale additive has a particle size of 100nm-500nm; and / or,

[0011] The length of the high-temperature resistant fiber is 0.1mm-2mm.

[0012] The leak-proof material as described above, wherein the high-temperature resistant fiber includes carbon fiber, glass fiber and asbestos fiber;

[0013] The mass ratio of the carbon fiber, glass fiber and asbestos fiber is (3-6):(4-5):(1-3).

[0014] The leak-proof material as described above, wherein the nanoscale additives include nano-silica and nano-calcium sulfate whiskers;

[0015] The mass ratio of the nano-silica to the nano-calcium sulfate whiskers is (1-2):(3-4).

[0016] Secondly, the present invention provides a leak-proof cement slurry, the leak-proof cement slurry comprising high-temperature resistant cement, leak-proof material, expansion material, toughening material, water loss reducing agent, retarder, defoamer and water;

[0017] The leak-proof material includes the leak-proof material described in the first aspect.

[0018] The leak-proof cement grout described above, wherein the high-temperature resistant cement includes oil well grade G high-temperature resistant cement; and / or,

[0019] The expansion material includes at least one of calcium oxide whiskers, calcined magnesium oxide, and calcined aluminum oxide; and / or,

[0020] The toughening material includes calcium silicate whiskers.

[0021] The leak-proof cement grout as described above comprises the following components by weight: 100 parts high-temperature resistant cement, 5-20 parts leak-proof material, 2-10 parts reinforcing agent, 1-4 parts expanding material, 1-5 parts toughening material, 2-5 parts water loss reducing agent, 0-2 parts retarder, 0.1-0.5 parts defoamer, and 45-88 parts water.

[0022] Thirdly, the present invention provides a method for sealing leaks using the leak-proof cement grout described in the second aspect, the method comprising the following steps: leak layer survey, pre-filling liquid injection, leak-proof cement grout preparation, leak-proof cement grout injection, setting and testing.

[0023] This invention uses a specific amount of high-temperature resistant fiber, high-temperature resistant sealant, and nano-level additives to prepare a leak-proof material, which simultaneously possesses excellent high-temperature stability, sealing performance, and leak-proof effect. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] In a first aspect, the present invention provides a leak-proof material, comprising, by weight percentage, the following components: 30%-60% high-temperature resistant fiber, 20%-40% high-temperature resistant sealant, and 10%-30% nano-grade additives.

[0026] The leak-proof material of this invention comprises a specific amount of high-temperature resistant fibers, high-temperature resistant sealants, and nano-scale additives. This leak-proof material can effectively improve the high-temperature stability, sealing performance, and leak-proof effect of leak-proof cement grout. Specifically, the high-temperature resistant fibers can form a three-dimensional network structure within the leak-proof material. This structure effectively bridges cracks and voids, disperses stress, and improves the tensile strength and impact resistance of the leak-proof material. The high-temperature resistant sealant can fill tiny pores and cracks, forming a denser structure to prevent liquid leakage and improve the impermeability of the leak-proof material. The nano-scale additives have a large specific surface area, excellent high-temperature stability, and high reactivity, promoting cement hydration and thus improving the density, strength, and high-temperature stability of the leak-proof cement grout.

[0027] For example, in the leak-proof material, the mass percentage of high-temperature resistant fiber can be 30%, 40%, 50%, or 60%, etc.

[0028] For example, the mass percentage of high-temperature resistant sealant in the leak-proof material can be 20%, 25%, 30%, 35%, or 40%, etc.

[0029] For example, in the leak-proof material, the mass percentage of nanoscale additives can be 10%, 15%, 20%, 25%, or 30%, etc.

[0030] In this invention, the high-temperature resistant fiber includes at least one of carbon fiber, glass fiber, and asbestos fiber. Carbon fiber has excellent heat resistance, chemical stability, and mechanical strength; glass fiber has good insulation, strength, and corrosion resistance, and is inexpensive; asbestos fiber has excellent heat resistance and chemical corrosion resistance.

[0031] In some embodiments, the high-temperature resistant fibers include carbon fiber, glass fiber, and asbestos fiber, with a mass ratio of (3-6):(4-5):(1-3), which can further improve the tensile strength and impact resistance of the leak-proof material. Exemplarily, the mass ratio of carbon fiber, glass fiber, and asbestos fiber can be 3:4:1, 4:4:1, 5:4:1, 6:4:1, 3:5:1, 4:5:1, 5:5:1, 6:5:1, 3:4:2, 4:4:2, 5:4:2, 6:4:2, 3:4:3, 4:4:3, 5:4:3, or 6:4:3, etc.

[0032] In some embodiments, the high-temperature resistant sealant includes at least one of sodium alginate gel, polyacrylamide gel, polyacrylonitrile gel, and polyvinyl alcohol gel, which can give the leak-proof material better impermeability.

[0033] In some embodiments, the nanoscale additives include nano-silica and / or nano-calcium sulfate whiskers. That is, the nanoscale additives may contain only nano-silica, or only nano-calcium sulfate whiskers, or both nano-silica and nano-calcium sulfate whiskers, which can give the leak-proof cement grout better density, strength and high-temperature stability.

[0034] In some embodiments, the nanoscale additives include nano-silica and nano-calcium sulfate whiskers, with a mass ratio of nano-silica to nano-calcium sulfate whiskers of (1-2):(3-4), further improving the density, strength and high-temperature stability of the leak-proof cement grout.

[0035] For example, the mass ratio of nano-silica to nano-calcium sulfate whiskers can be 1:3, 1:3.3, 1:3.6, 1:4, 1.5:3, 1.5:3.3, 1.5:3.6, 1.5:4, 2:3, 2:3.3, 2:3.6, or 2:4, etc.

[0036] In some implementations, the nanoscale additives have a particle size of 100nm-500nm, which can further improve the density, strength and high-temperature stability of the leak-proof cement grout.

[0037] For example, the particle size of the nanoscale additive can be 100nm, 200nm, 300nm, 400nm or 500nm, etc.

[0038] In some implementations, the length of the high-temperature resistant fiber is 0.1mm-2mm, giving the leak-proof material better tensile strength and impact resistance.

[0039] For example, the length of the high-temperature resistant fiber can be 0.1mm, 0.4mm, 0.8mm, 1.2mm, 1.6mm or 2mm, etc.

[0040] In a second aspect, the present invention provides a leak-proof cement slurry, which includes: high-temperature resistant cement, leak-proof material, expansion material, toughening material, water loss reducing agent, retarder, defoamer and water, wherein the leak-proof material includes the leak-proof material obtained in the first aspect.

[0041] This leak-proof cement grout possesses excellent leak-proof properties, sealing performance, and high-temperature stability. Specifically, the high-temperature resistant cement maintains chemical stability under high-temperature conditions; the expansive material expands during the grout's solidification process, compensating for volume changes caused by hydration shrinkage, thus improving the grout's sealing and adhesion; the toughening material enhances the grout's toughness and crack resistance, preventing cracks during curing or use; the water-loss reducing agent minimizes moisture loss at high temperatures, maintaining good fluidity; the retarder slows the setting time, providing a longer working time and facilitating construction and operation; and the defoamer eliminates air bubbles, improving the grout's density and uniformity.

[0042] In some implementations, the high-temperature resistant cement includes Grade G high-temperature resistant cement for oil wells, which can maintain its strength and stability under high-temperature conditions and is suitable for deep and ultra-deep well environments.

[0043] In some embodiments, the expanding material includes at least one of calcium oxide whiskers, calcined magnesium oxide, and calcined aluminum oxide. These materials have low elastic modulus and can react with cement hydration products such as ettringite (AFt) and calcium silicate hydrate (CSH) to generate fibrous lattice materials, thereby improving the toughness of cement stone.

[0044] In some embodiments, the toughening material includes calcium silicate whiskers, which can absorb some of the stress in the cement stone. The calcium silicate whiskers and cement hydration products form a mixture of interpenetrating matrices, which relieves internal stress and reduces the generation of microcracks.

[0045] In this invention, the leak-proof cement grout comprises the following components in parts by weight: 100 parts high-temperature resistant cement, 5-20 parts (e.g., 5, 8, 11, 14, 17, or 20 parts) of leak-proof material, 2-10 parts (e.g., 2, 4, 6, 8, or 10 parts) of reinforcing agent, 1-4 parts (e.g., 1, 2, 3, or 4 parts) of expanding material, and 1-5 parts (e.g., 1, 2, 3, or 4 parts) of toughening agent. Materials: 2-5 parts (e.g., 2, 3, 4 or 5 parts) of water loss reducer, 0-2 parts (e.g., 0, 0.5, 1 or 2 parts) of retarder, 0.1-0.5 parts (e.g., 0.1, 0.2, 0.3, 0.4 or 0.5 parts) of defoamer, and 45-88 parts (e.g., 45, 50, 55, 60, 65, 70, 75, 80 or 88 parts) of water.

[0046] Thirdly, the present invention provides a method for sealing leaks with leak-proof cement grout, the method comprising the following steps: leak layer survey, pre-filling liquid injection, leak-proof cement grout preparation, leak-proof cement grout injection, waiting for setting and testing.

[0047] In some implementations, the leak sealing method includes the following steps:

[0048] S1 Leakage Detection: Before cementing, we comprehensively utilize logging data, downhole pressure monitoring, and other methods to accurately locate the leakage layer and determine the degree of leakage, such as micro-cracks, pore-type leakage, or large fault zone leakage. We record parameters such as the depth and thickness of the leakage layer to provide a basis for subsequent plugging schemes.

[0049] S2 Pre-flush Injection: High-viscosity pre-flush is prepared according to the characteristics of the lost circulation zone and slowly pumped into the well at a low flow rate. Its function is to form a low-permeability sealing film at the entrance of the lost circulation channel, reduce the cement slurry loss rate, and isolate the drilling fluid from the cement slurry to prevent contamination. The injection volume is usually controlled according to the well diameter and the size of the lost circulation zone.

[0050] S3 leak-proof cement grout preparation: Add water and mix according to the precise ratio. Optimize the performance of the cement grout through experiments to ensure that the consistency, water loss rate, initial setting time and other indicators are suitable for leak-proof working conditions.

[0051] S4 Leak-proof Cement Grout Injection: A second layer of leak-proof cement grout is injected into the leaking layer to seal it. A staged injection method is used, starting with a low discharge rate to allow the leak-proof cement grout to enter the initial section of the leaking layer smoothly. After the pressure stabilizes, the discharge rate is gradually increased to the designed discharge rate. During the process, the pump pressure and grout return are monitored in real time. If there is a sudden increase in pressure or loss of return, the discharge rate is adjusted in time and the leak-proof cement grout is replenished to ensure that the leak-proof cement grout fills the leaking layer evenly and continuously. The injection volume is based on the volume of the leaking layer and the well diameter.

[0052] S5 Curing and Testing: After injection, shut in the well and wait for curing. Determine the curing time based on the characteristics of the anti-leakage cement slurry and the well temperature. After the curing period, use sonic logging, pressure testing and other testing methods to check the plugging effect.

[0053] The present invention will be further described in detail below through specific embodiments.

[0054] Preparation Examples 1-6 and Comparative Preparation Examples 1-3

[0055] The methods for preparing the leak-proof materials in this preparation example and the comparative preparation example include the following steps:

[0056] High-temperature resistant fibers, high-temperature resistant sealants, and nano-scale additives were mixed in a sealed space at 20°C for 20 minutes to obtain a leak-proof material. The specific types and mass percentages of each component in this leak-proof material are shown in Table 1. Specifically, the carbon fiber has a length of 0.2mm-1.0mm, the glass fiber has a length of 0.5mm-1.2mm, the asbestos fiber has a length of 0.8mm-1.5mm, the nano-silica has a particle size of 100nm-500nm, the nano-calcium sulfate whiskers have a particle size of 100nm-500nm, and the sodium alginate gel (Zhejiang Fenghong New Material Co., Ltd., SMF-SAG) is also present.

[0057] Table 1

[0058]

[0059] Comparative preparation example 4

[0060] The preparation method of the leak-proof material in this comparative preparation example is basically the same as that in preparation example 1. The difference is that 20 wt% carbon fiber, 20 wt% glass fiber and 12 wt% asbestos fiber are replaced with 52 wt% rice husk fiber.

[0061] Examples 1-6 and Comparative Examples 1-4

[0062] The provided method for preparing leak-proof cement grout includes the following steps:

[0063] High-temperature resistant cement, the leak-proof materials prepared in Preparation Examples 1-6 and Comparative Preparation Examples 1-4, reinforcing agent, expanding material, toughening material, water loss reducing agent, retarder, defoamer and water were mixed for 3 minutes to obtain leak-proof cement slurry. The weight parts of each component in the leak-proof cement slurry are shown in Table 2.

[0064] Table 2

[0065]

[0066] The expansion materials include calcium oxide whiskers, calcined magnesium oxide, and calcined alumina (manufacturer: China National Petroleum Corporation Great Wall Drilling Engineering Co., Ltd. Cementing Company, GWP-100S expansion agent); the toughening materials include calcium silicate whiskers (China National Petroleum Corporation Great Wall Drilling Engineering Co., Ltd. Cementing Company, GWI-100S toughening agent); the fluid loss reducing agent includes AM-AMPS-NVP-DMAA quaternary copolymer (China National Petroleum Corporation Great Wall Drilling Engineering Co., Ltd. Cementing Company, GWF-200L fluid loss reducing agent); the retarder includes AM-AA-MA-NVP quaternary copolymer (China National Petroleum Corporation Great Wall Drilling Engineering Co., Ltd. Cementing Company, GWR-300L retarder); and the defoamer includes organosilicon defoamer (China National Petroleum Corporation Great Wall Drilling Engineering Co., Ltd. Cementing Company, GWX-1L defoamer). In the dehydration reducer and retarder, AM is acrylamide, AMPS is 2-acrylamido-2-methylpropanesulfonic acid, NVP is N-vinylpyrrolidone, DMAA is N,N-dimethylacrylamide, AA is acrylic acid, and MA is methacrylic acid.

[0067] Performance testing

[0068] Leak-stopping tests, compressive strength loss, water loss, thickening time, and 200℃ compressive strength tests were conducted on the anti-leakage cement slurries in the examples and comparative examples, respectively. The results are shown in Table 3.

[0069] (1) Leakage prevention performance: The leakage prevention performance of the cement grout was evaluated by simulating seepage-type and crack-type formations using a perforated plate with a diameter of 1 mm and a slotted plate with a slot width of 1 mm, respectively.

[0070] Pour 500ml of the prepared leak-proof cement slurry into the test chamber. Increase the pressure from 0 to 0.7MPa within 50 seconds to simulate the initial formation pressure. Then, increase the pressure at a rate of 0.2MPa / 30s (the leakage rate in the Ordos Basin is generally less than 30L / s). The average leakage is calculated as 200m~300m, and the total leakage is 5m. 3 ~8m 3 The formation pressure differential was 2 MPa to 5 MPa, the displacement velocity was 5 L / s to 40 L / s, the cement slurry rise rate was 0.2 to 2.0 m / s, and the pressure differential increase rate was 0.01 MPa / s to 0.10 MPa / s. The maximum pressure differential was set to 5 MPa, and the pressurization rate was 0.20 MPa / 30 s. The leakage was recorded. The leakage of the orifice plate with a diameter of 1 mm was recorded as V1, and the leakage of the slot plate with a slot width of 1 mm was recorded as V2. The results are shown in Table 3.

[0071] (2) Loss of compressive strength: Eight portions of the same mass of leak-proof cement slurry (eight portions of leak-proof cement slurry were taken for each example or comparative example in Examples 1-6 and Comparative Examples 1-4) were cured at 60℃ for 3 days to form eight cement stones. The initial compressive strength of four cement stones was tested using a pressure testing machine, and the average initial compressive strength of the four cement stones was calculated as P0. The other four cement stones were placed in a pressure curing kettle and cured at 200℃ for 60 days according to the equipment operation procedures and test conditions. The cured cement stones were then taken out and the compressive strength was tested using a pressure testing machine, and the average compressive strength of the four cement stones after 60 days of curing was calculated as P1. The strength attenuation rate η was calculated according to the following formula, and the results are shown in Table 3.

[0072] η = (P0 - P1) / P0 × 100%

[0073] (3) The thickening time was determined according to the method specified in GB / T 19139-2012, and the results are shown in Table 3;

[0074] (4) The water loss was determined according to the method specified in GB / T 19139-2012, and the results are shown in Table 3;

[0075] (5) The compressive strength at 200℃ was determined according to the method specified in GB / T 19139-2012, and the results are shown in Table 3.

[0076] Table 3

[0077]

[0078] As shown in Table 3, compared with Comparative Examples 1-4, the leak-proof cement slurry prepared in Examples 1-6 has excellent leak-proof properties, sealing properties and high-temperature stability.

[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; and these 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 leak-proof material, characterized in that, By weight percentage, it includes the following components: 30%-60% high-temperature resistant fiber, 20%-40% high-temperature resistant sealant, and 10%-30% nano-grade additives.

2. The leak-proof material according to claim 1, characterized in that, The high-temperature resistant fiber includes at least one of carbon fiber, glass fiber, and asbestos fiber.

3. The leak-proof material according to claim 1 or 2, characterized in that, The nanoscale additives include nano-silica and / or nano-calcium sulfate whiskers.

4. The leak-proof material according to claim 1, characterized in that, The high-temperature resistant sealant includes at least one of sodium alginate gel, polyacrylamide gel, polyacrylonitrile gel, and polyvinyl alcohol gel; and / or, The nanoscale additive has a particle size of 100nm-500nm; and / or, The length of the high-temperature resistant fiber is 0.1mm-2mm.

5. The leak-proof material according to claim 2, characterized in that, The high-temperature resistant fibers include carbon fiber, glass fiber, and asbestos fiber; The mass ratio of the carbon fiber, glass fiber and asbestos fiber is (3-6):(4-5):(1-3).

6. The leak-proof material according to claim 3, characterized in that, The nanoscale additives include nano-silica and nano-calcium sulfate whiskers; The mass ratio of the nano-silica to the nano-calcium sulfate whiskers is (1-2):(3-4).

7. A leak-proof cement grout, characterized in that, The leak-proof cement slurry includes: high-temperature resistant cement, leak-proof material, expansion material, toughening material, water loss reducing agent, retarder, defoamer, and water; The leak-proof material includes the leak-proof material according to any one of claims 1-6.

8. The leak-proof cement grout according to claim 7, characterized in that, The high-temperature resistant cement includes Grade G high-temperature resistant cement for oil wells; and / or, The expansion material includes at least one of calcium oxide whiskers, calcined magnesium oxide, and calcined aluminum oxide; and / or, The toughening material includes calcium silicate whiskers.

9. The leak-proof cement grout according to claim 7 or 8, characterized in that, The leak-proof cement grout comprises the following components by weight: 100 parts high-temperature resistant cement, 5-20 parts leak-proof material, 2-10 parts reinforcing agent, 1-4 parts expanding material, 1-5 parts toughening material, 2-5 parts water loss reducing agent, 0-2 parts retarder, 0.1-0.5 parts defoamer, and 45-88 parts water.

10. A method for sealing leaks with leak-proof cement grout, characterized in that, The leak sealing method includes the following steps: leak layer detection, pre-filling liquid injection, leak-proof cement grout preparation, leak-proof cement grout injection, setting and testing; The leak-proof cement grout includes the leak-proof cement grout according to any one of claims 7-9.

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