A plugging framework material, a preparation method and application thereof

Abstract

This invention discloses a plugging skeleton material, its preparation method, and its application, belonging to the field of oil drilling technology. The invention provides a plugging skeleton material prepared by coating an elastic material surface with polyvinyl alcohol and inorganic particles. The elastic material is selected from at least one of sponge, elastic graphite, and rubber. This plugging skeleton material, through modification of the elastic material, improves the hydrophobicity, temperature resistance, and oil resistance of the original material. It exhibits good dispersibility in oil-based drilling fluids, is less prone to swelling, and possesses good elasticity, resulting in good compatibility with fractures and facilitating deep fracture penetration. Furthermore, the plugging skeleton material can recover its shape after entering the fracture, facilitating bridging and mesh formation. It has good plugging effects on various types of leakage, significantly improving the success rate of plugging and preventing recurrence of leakage. It is particularly effective in plugging fracture-vuggy leakage.

Description

Technical Field

[0001] This invention relates to the field of oil drilling technology, specifically to a plugging skeleton material, its preparation method, and its application. Background Technology

[0002] Loss in wells occurs when various working fluids leak into the formation under differential pressure during downhole operations such as drilling, cementing, completion, testing, or workover. Once loss in wells occurs, it not only delays drilling time, wastes drilling fluid, damages oil and gas reservoirs, interferes with geological logging, and increases drilling costs, but also easily leads to a series of complex situations such as stuck pipe, blowouts, and well collapse, and may even result in wellbore abandonment, causing huge economic losses.

[0003] As our understanding of the various causes of well leakage deepens, the development of plugging skeleton materials is also continuously advancing. When well leakage occurs, the blending ratio of granular, flake, and fibrous plugging skeleton materials is generally adjusted according to the pore size and location of the lost circulation layer, and appropriate inert materials are added to complement it and enhance the plugging effect. Commonly used granular plugging skeleton materials include walnut shells, rubber granules, diatomaceous earth, and asphalt; fibrous materials include sawdust, cotton fibers, and flax fibers; and flake materials include mica flakes and rice husks. For man-made fractures caused by high drilling speeds or rapid drilling during the drilling process, the non-solidifying properties of soft and hard plugging skeleton materials can be utilized to form a non-flowing viscous substance for sealing. These materials mainly include diesel-bentonite slurry, shear-thickened fluid, barite plugs, and lime slurry. The above types of plugging skeleton materials can solve some leakage and backflow caused by pores and fractures, but they cannot effectively solve some complex leakage problems. Therefore, various new plugging agents, such as chemical plugging agents, high-water-loss plugging agents, and mixed plugging slurries, have emerged, providing effective means to deal with various types of well leakage and improve the success rate of well leakage treatment.

[0004] With continuous technological advancements, various targeted plugging materials have been developed, including high-loss plugging materials, chemical plugging materials, and mixed plugging slurries. High-loss plugging materials, after entering the lost circulation zone, rapidly lose water under the pressure difference generated by the drilling fluid column pressure and the bottom layer pressure, forming a filter cake that blocks the leakage channels. These materials mainly include permeable materials, fibrous materials, diatomaceous earth, and porous inert materials. Chemical plugging materials utilize the static forces, intermolecular forces, and chemical bonds of polymers at the interface to form a bond at the interface, thus achieving a plugging effect. These materials include gel plugging agents, resin plugging agents, and expansive plugging agents. Mixed plugging slurries are mainly composed of special cement and mixed cement slurries, with different additives added to improve the early strength and stability of the cement paste, resulting in higher pressure resistance. These types of plugging materials are effective in plugging both permeable and fractured leaks. However, with the increasing demands on drilling technology, serious leaks such as karst caverns frequently occur, and these conventional plugging skeleton materials cannot effectively plug the leaks.

[0005] Currently, the most commonly used leak-sealing framework materials in leak-sealing construction are bridging framework materials and chemical gel framework materials. Chemical leak sealing mainly achieves its sealing effect through the chemical reaction of polymers, including cross-linking reactions, curing reactions, and other methods. Chemical leak sealing has a good sealing effect against serious leaks, but the chemical sealing reaction is relatively violent, the construction is complex, and the risk is relatively high. Bridging framework materials have a simple construction process and low cost, and are the most commonly used in the field, but some materials have poor temperature resistance and are prone to decomposition and failure at high temperatures, causing repeated leakage of the leaking layer. At the same time, these materials have problems such as being unable to seal the leak and not being able to be soaked for a long time, and the sealing effect is sometimes not ideal.

[0006] Over the past two decades, researchers have made significant progress in the preparation of various ultrathin films through in-depth exploration. Particularly in the field of layer-by-layer self-assembly, significant advancements have been achieved due to its effectiveness in the innovative design and application of ultrathin films with special functional properties. For example, Chinese patent CN101085880A proposes a nanolayered calcium carbonate biomimetic composite material, which involves low-molecular-weight organic compounds participating in the reaction of calcium chloride and sodium carbonate, guiding calcite to form a nanolayered structure, and then directionally assembling the layered structure into a multilayered nanolayer structure. These studies have played a crucial role in promoting the biomimetic synthesis of biomineralized materials, but biomimetic materials with a natural calcium carbonate structure have not yet been grown, or the methods and material properties still need further improvement.

[0007] Some researchers have used sponges as a skeleton material with high compatibility with cracks. For example, Chinese patent CN103923627A discloses a pressure-bearing plugging agent for oil and gas well drilling, which is composed of elastic sponge fiber, oil well cement, finely ground slag, calcium clay, mica powder and water. It can be used for pressure-bearing plugging in oil and gas well drilling.

[0008] Currently, sponge materials are prone to swelling in oil-based drilling fluids, which leads to loss of elasticity and a significant reduction in the effectiveness of plugging leaks. Therefore, it is necessary to modify sponges to improve their hydrophobicity and resistance to temperature and oil. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies by providing a plugging skeleton material, its preparation method, and its application. This plugging skeleton material modifies an elastic sponge, improving the sponge's hydrophobicity, temperature resistance, and oil resistance. It exhibits good dispersibility in oil-based drilling fluids, is less prone to swelling, and possesses good elasticity, resulting in good compatibility with fractures and facilitating deep fracture penetration. Furthermore, the plugging skeleton material recovers its shape after entering the fracture, facilitating bridging and mesh formation. It demonstrates effective plugging of various types of leakage, significantly improving the success rate of plugging and preventing recurrence of leakage. It is particularly effective in plugging fracture-vulnerability leakage.

[0010] To address the aforementioned technical problems, the first aspect of this invention provides a leak-sealing skeleton material, the leak-sealing skeleton material comprising an elastic material and a deposited film coated on the surface of the elastic material; the raw materials for preparing the deposited film include polyvinyl alcohol, inorganic particles, and optionally a crosslinking agent; the elastic material is selected from at least one of sponge, elastic graphite, and rubber.

[0011] According to some embodiments of the present invention, taking the total mass of the leak-sealing skeleton material as 100%,

[0012] The mass percentage of elastic material is 89%–95.7%.

[0013] The mass percentage of polyvinyl alcohol is 2.2% to 5.6%;

[0014] The mass percentage of inorganic particles is 2.1% to 4.4%;

[0015] The crosslinking agent has a mass percentage of 0% to 1%.

[0016] According to some embodiments of the present invention, the crosslinking agent is selected from at least one of glutaraldehyde and boric acid.

[0017] According to some embodiments of the present invention, the average particle size of the elastic material is 1 mm to 5 mm.

[0018] According to some embodiments of the present invention, the sponge is a polyurethane sponge or a polyether polyol sponge, and the sponge has a mesh-like structure.

[0019] According to some embodiments of the present invention, the average particle size of the inorganic particles is 0.05 μm to 1 μm, for example 0.05 μm, 0.1 μm, 0.5 μm, 0.8 μm, 1 μm; preferably, the inorganic particles are selected from at least one of montmorillonite, nano-calcium carbonate, and sepiolite.

[0020] According to some embodiments of the present invention, the pore size of the sponge is 10 ppi to 40 ppi, preferably 30 ppi, the porosity is 95% to 96%, preferably 96%, and the density is 21 kg / cm³. 3 ~22kg / cm 3 Optimal weight 22kg / cm 3 .

[0021] According to some embodiments of the present invention, the mass retention rate of the plugging skeleton material is 91.8% to 96.9%, the tensile strength is 0.59 MPa to 5.56 MPa, and the tensile strength retention rate is 75.8% to 92.4%.

[0022] A second aspect of the present invention provides a method for preparing the above-mentioned leak-sealing skeleton material, comprising the following steps:

[0023] 1) Coat the surface of the elastic material sequentially with solution I containing polyvinyl alcohol and solution II containing inorganic particles, or coat the surface of the elastic material with a mixed solution containing inorganic particles and polyvinyl alcohol.

[0024] 2) After repeating step 1) 50 to 200 times, dry the coated elastic material to obtain the leak-sealing skeleton material.

[0025] According to some embodiments of the present invention, in step 1), the solvent I in the solution I containing polyvinyl alcohol is selected from water; preferably, the content of polyvinyl alcohol in the solution I containing polyvinyl alcohol is 0.5wt% to 1.0wt%, for example 0.5wt%, 0.8wt%, 0.9wt%, or 1wt%.

[0026] According to some embodiments of the present invention, in step 1), in the solution II containing inorganic particles, solvent II is selected from at least one of water, white oil, and brine; preferably, the brine is selected from a 20% NaCl aqueous solution.

[0027] And / or, the content of inorganic particles in the solution II containing inorganic particles is 0.1wt% to 0.5wt%, for example 0.1wt%, 0.2wt%, or 0.5wt%.

[0028] According to some embodiments of the present invention, in step 2), the drying conditions include: a temperature of 60°C to 80°C, for example, 60°C, 70°C, or 80°C; and a time of 2h to 8h, for example, 2h, 3h, 4h, 5h, 6h, 7h, or 8h.

[0029] According to some embodiments of the present invention, in step 1), the mixed solution containing inorganic particles and polyvinyl alcohol is a mixed solution containing polyvinyl alcohol solution I and solution containing inorganic particles solution II; wherein, the total content of inorganic particles and polyvinyl alcohol is 10wt% to 15wt%, for example 10wt% or 15wt%; and / or, the mass ratio of inorganic particles to polyvinyl alcohol in the mixed solution containing inorganic particles and polyvinyl alcohol is (0.7 to 1):(1.5 to 2), for example 0.8:1.5, 1:2, 1:1.8, or 0.8:1.8.

[0030] According to some embodiments of the present invention, in step 1), the mixed solution containing inorganic particles and polyvinyl alcohol further includes a crosslinking agent; and / or, the content of the crosslinking agent in the mixed solution containing inorganic particles and polyvinyl alcohol is 0.1 wt% to 1 wt%, for example 0.8 wt%, 0.9 wt%, or 1 wt%.

[0031] In this invention, the crosslinking agent can effectively improve the quality and speed of film formation. Specifically, the crosslinking between glutaraldehyde and polyvinyl alcohol is an aldol condensation reaction between hydroxyl and aldehyde groups. The aldehyde group first reacts with the hydroxyl group to form a hemiacetal, which then undergoes dehydration condensation with the hydroxyl group to form an ether, thus ensuring that montmorillonite and polyvinyl alcohol form a network structure under glutaraldehyde crosslinking. The crosslinking mechanism of boric acid is that boric acid undergoes hydrolysis in water to produce B(OH)3 and B(OH)4. - B(OH)4 - It can be dehydrated and esterified with the hydroxyl groups on the polyvinyl alcohol (PVA) chain to form borate esters. Since each boron atom has four esterification functional groups, it can react on different molecular chains, causing PVA molecules to cross-link and form a network structure.

[0032] The third aspect of this invention provides an application of a plugging skeleton material or a plugging skeleton material prepared by the above preparation method in well drilling plugging, oil production water shut-off profile control, and well fracturing.

[0033] Beneficial effects:

[0034] The plugging skeleton material described in this invention has good hydrophobic properties and oil and temperature resistance. It will not fail in high temperature and oil-based drilling fluid. It can be effectively dispersed in oil-based drilling fluid, which is beneficial to the preparation of oil-based drilling fluid plugging agent. This improves the plugging effect of the plugging material at high temperature in oil-based drilling fluid and avoids repeated leakage.

[0035] The plugging skeleton material of this invention forms a composite film on the surface of polyurethane sponge (elastic material). This composite film is hydrophobic, oil-resistant, and has certain mechanical strength, making it easy to disperse in oil-based drilling fluids without affecting the rheological properties of the drilling fluid. This solves the problem of conventional plugging skeleton materials failing to disperse in oil-based drilling fluids, resulting in unsatisfactory plugging effects. The hydrophobicity of this composite film may be due to the addition of hydroxyl groups to aldehyde groups after the introduction of a crosslinking agent, which reduces the number of hydroxyl groups on the PVA chain and the possibility of hydroxyl groups forming hydrogen bonds with water. Secondly, the crosslinking forms a network structure, which restricts the activity space of PVA molecules.

[0036] The plugging skeleton material described in this invention is not prone to swelling, can maintain elasticity in oil-based drilling fluid, has good compatibility with fractures, which is beneficial for deep fracture penetration. At the same time, it can restore its shape after entering the fracture, which is beneficial for bridging and forming a network. It has a good plugging effect on various types of leakage. Attached Figure Description

[0037] Figure 1 Contact angle of the leak-sealing skeleton material. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to these embodiments.

[0039] In this invention, the contact angle measuring instrument was purchased from Beijing HARKE Test Instrument Factory, model HARKE-SPCA.

[0040] In this invention, the high-temperature roller heating furnace was purchased from Qingdao Haitong Yuanda Instrument Co., Ltd., model XGRL-4.

[0041] In this invention, the universal testing machine was purchased from Jiangsu Tianyuan Testing Equipment Co., Ltd., model number TY8000.

[0042] Unless otherwise specified, the spatula, drying oven, and oil bath can be commercially available in this invention.

[0043] In this invention, the wedge-shaped long crack sealing experimental device is a conventional experimental device in the field and was developed by China University of Petroleum (East China).

[0044] In this invention, the diesel fuel was purchased from Shengli Oilfield and is of type 0.

[0045] In this invention, the montmorillonite is nanomontmorillonite with a purity greater than 98%, purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd.

[0046] The degree of polymerization of polyvinyl alcohol in this invention is 1500, and it was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] The polyurethane foam in this invention has a pore size of 30 ppi, an open porosity of 96%, and a density of 22 kg / cm³. 3 The polyurethane sponge has an average particle size of 5mm and was purchased from Shenzhen Lvchuang Environmental Protection Filter Material Co., Ltd.

[0048] In this invention, the solvent in solutions such as polyvinyl alcohol solution, montmorillonite solution, sepiolite solution, nano-calcium carbonate solution, mixed solution of montmorillonite and polyvinyl alcohol, and polyethyleneimine is water.

[0049] Example 1

[0050] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0051] The raw materials for preparing the plugging skeleton material are: 95% polyurethane foam, 2.8% polyvinyl alcohol, and 2.2% montmorillonite.

[0052] Prepare 1 wt% polyvinyl alcohol solution and 0.5 wt% montmorillonite solution respectively. Then, use a spatula to apply the polyvinyl alcohol solution and montmorillonite solution (montmorillonite particle size 1 μm) sequentially to the surface of polyurethane sponge. Repeat the application operation 120 times. Place the coated polyurethane sponge in a drying oven at 80°C and dry for 2 hours to obtain the leak-sealing skeleton material.

[0053] Example 2

[0054] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0055] The raw materials for preparing the plugging skeleton material are: 90% polyurethane foam, 5.6% polyvinyl alcohol, and 4.4% montmorillonite.

[0056] Prepare 0.5 wt% polyvinyl alcohol solution and 0.1 wt% montmorillonite solution respectively. Then, use a spatula to apply the polyvinyl alcohol solution and montmorillonite solution (montmorillonite particle size 0.05 μm) to the surface of polyurethane sponge in sequence. Repeat the application operation 50 times. Then, place the coated polyurethane sponge in a drying oven at 60°C and dry for 5 hours to obtain the leak-sealing skeleton material.

[0057] Example 3

[0058] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0059] The raw materials for preparing the plugging skeleton material are: polyurethane foam with a mass fraction of 92.2%, polyvinyl alcohol with a mass fraction of 5.2%, and montmorillonite with a mass fraction of 2.6%.

[0060] Prepare 0.8 wt% polyvinyl alcohol solution and 0.2 wt% montmorillonite solution respectively. Then, use a spatula to apply the polyvinyl alcohol solution and montmorillonite solution (montmorillonite particle size 0.8 μm) to the surface of polyurethane sponge in sequence. Repeat the application operation 200 times. Place the coated polyurethane sponge in a drying oven at 70°C and dry for 3 hours to obtain the leak-sealing skeleton material.

[0061] Example 4

[0062] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0063] The raw materials for preparing the leak-sealing skeleton material are: polyurethane foam with a mass fraction of 92.2%, polyvinyl alcohol with a mass fraction of 5.2%, and sepiolite with a mass fraction of 2.6%.

[0064] Prepare 0.9 wt% polyvinyl alcohol solution and 0.5 wt% sepiolite solution respectively. Then, use a spatula to apply the polyvinyl alcohol solution and sepiolite solution (sepiolite particle size 0.8 μm) to the surface of polyurethane sponge in sequence. Repeat the application operation 200 times. Place the coated polyurethane sponge in a drying oven at 80°C and dry for 4 hours to obtain the leak-sealing skeleton material.

[0065] Example 5

[0066] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0067] The raw materials for preparing the leak-sealing skeleton material are: polyurethane foam with a mass fraction of 91.9%, polyvinyl alcohol with a mass fraction of 5.4%, and nano-calcium carbonate with a mass fraction of 2.7%.

[0068] Prepare 1 wt% polyvinyl alcohol solution and 0.5 wt% nano-calcium carbonate solution respectively. Then, use a spatula to apply the polyvinyl alcohol solution and nano-calcium carbonate solution (nano-calcium carbonate particle size 0.5 μm) to the surface of polyurethane sponge in sequence. Repeat the application operation 200 times. Place the coated polyurethane sponge in a drying oven at 80°C and dry for 5 hours to obtain the leak-sealing skeleton material.

[0069] Example 6

[0070] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0071] The raw materials for preparing the plugging skeleton material are: polyurethane foam with a mass fraction of 92.2%, polyvinyl alcohol with a mass fraction of 5.2%, and montmorillonite with a mass fraction of 2.7%.

[0072] Prepare a 10wt% mixed solution of montmorillonite and polyvinyl alcohol (montmorillonite to polyvinyl alcohol mass ratio of 0.8:1.5, montmorillonite particle size 0.1μm); then use a spatula to apply the montmorillonite solution and polyvinyl alcohol mixture to the surface of polyurethane sponge. Repeat the application operation 200 times, and then place the coated polyurethane sponge in a drying oven at 80℃ for 8 hours to obtain the leak-sealing skeleton material.

[0073] Example 7

[0074] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0075] The raw materials for preparing the plugging skeleton material are: 93% polyurethane foam, 4.4% polyvinyl alcohol, and 2.2% montmorillonite.

[0076] Prepare a 15wt% mixture of montmorillonite and polyvinyl alcohol (montmorillonite and polyvinyl alcohol in a mass ratio of 1:2, with montmorillonite particle size of 0.1μm); then apply the mixture of montmorillonite and polyvinyl alcohol to the surface of a polyurethane sponge using a spatula. Repeat the application 120 times, and then place the coated polyurethane sponge in a drying oven at 60℃ for 6 hours to obtain the leak-sealing skeleton material.

[0077] Example 8

[0078] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0079] The raw materials for preparing the plugging skeleton material are: polyurethane foam with a mass fraction of 92.3%, polyvinyl alcohol with a mass fraction of 4.6%, and montmorillonite with a mass fraction of 3.1%.

[0080] Prepare a 15wt% mixture of montmorillonite and polyvinyl alcohol (montmorillonite and polyvinyl alcohol in a mass ratio of 1:1.5, with montmorillonite particle size of 0.5μm); then apply the mixture of montmorillonite and polyvinyl alcohol to the surface of polyurethane foam using a spatula. Repeat the application 50 times, and then place the coated polyurethane foam in a drying oven at 80℃ for 2 hours to obtain the leak-sealing skeleton material.

[0081] Example 9

[0082] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0083] The raw materials for preparing the leak-sealing skeleton material are: 92% polyurethane foam, 5.2% polyvinyl alcohol, 2.6% montmorillonite, and 0.2% glutaraldehyde.

[0084] Prepare a mixed solution of 15 wt% montmorillonite and polyvinyl alcohol (mass ratio of montmorillonite to polyvinyl alcohol is 1:2, particle size of montmorillonite is 0.5 μm); add 0.8 wt% glutaraldehyde to the mixed solution, and then use a spatula to apply the montmorillonite solution and polyvinyl alcohol mixture to the surface of polyurethane foam. Repeat the application operation 200 times, and then place the coated polyurethane foam in a drying oven at 80℃ for 8 hours to obtain the leak-sealing skeleton material.

[0085] Example 10

[0086] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0087] The raw materials for preparing the leak-sealing skeleton material are: polyurethane foam with a mass fraction of 91.8%, polyvinyl alcohol with a mass fraction of 5.4%, montmorillonite with a mass fraction of 2.4%, and glutaraldehyde with a mass fraction of 0.4%.

[0088] Prepare a 10wt% mixed solution of montmorillonite and polyvinyl alcohol (mass ratio of montmorillonite to polyvinyl alcohol is 0.8:1.8, and the particle size of montmorillonite is 0.5μm). Add 1wt% glutaraldehyde to the mixed solution, and then use a spatula to apply the montmorillonite and polyvinyl alcohol mixture to the surface of a polyurethane sponge. Repeat the application 50 times, and then place the coated polyurethane sponge in a drying oven at 60℃ for 2 hours to obtain the leak-sealing skeleton material.

[0089] Example 11

[0090] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0091] The raw materials for preparing the plugging skeleton material are: polyurethane foam with a mass fraction of 91.8%, polyvinyl alcohol with a mass fraction of 5.4%, montmorillonite with a mass fraction of 2.7%, and boric acid with a mass fraction of 0.1%.

[0092] Prepare a mixed solution of 15 wt% montmorillonite and polyvinyl alcohol (mass ratio of montmorillonite to polyvinyl alcohol is 1:2, particle size of montmorillonite is 0.5 μm); add 0.9 wt% boric acid to the mixed solution, and then use a spatula to apply the montmorillonite solution and polyvinyl alcohol mixture to the surface of polyurethane foam. Repeat the application operation 180 times, and then place the coated polyurethane foam in a drying oven at 80℃ for 6 hours to obtain the leak-sealing skeleton material.

[0093] Example 12

[0094] This embodiment provides a leak-sealing skeleton material and its preparation method.

[0095] The difference between this embodiment and Example 1 is that a 0.5 wt% montmorillonite solution (montmorillonite particle size 1 μm) and a 1 wt% polyvinyl alcohol solution were sequentially applied to the surface of the polyurethane foam using a spatula, while other conditions remained unchanged.

[0096] Comparative Example 1

[0097] This comparative example provides a leak-sealing skeleton material.

[0098] This comparative example directly uses polyurethane foam as the leak-sealing skeleton material.

[0099] Comparative Example 2

[0100] This comparative example provides a leak-sealing skeleton material and its preparation method.

[0101] The raw materials for preparing the plugging skeleton material are: polyurethane foam with a mass fraction of 97.2%, montmorillonite with a mass fraction of 2.7%, and boric acid with a mass fraction of 0.1%.

[0102] The difference between this comparative example and Example 11 is that a 15 wt% montmorillonite solution was used instead of a 15 wt% mixed solution of montmorillonite and polyvinyl alcohol, while other conditions remained the same.

[0103] Comparative Example 3

[0104] This comparative example provides a leak-sealing skeleton material and its preparation method.

[0105] The raw materials for preparing the leak-sealing skeleton material are: polyurethane foam with a mass fraction of 94.5%, polyvinyl alcohol with a mass fraction of 5.4%, and boric acid with a mass fraction of 0.1%.

[0106] The difference between this comparative example and Example 11 is that a 15 wt% polyvinyl alcohol solution was used instead of a 15 wt% mixed solution of montmorillonite and polyvinyl alcohol, while other conditions remained the same.

[0107] Performance Evaluation and Testing

[0108] 1. Temperature resistance test:

[0109] The test material was heated by rolling in a high-temperature roller furnace and then subjected to a high-temperature resistance evaluation test. The rolling heating temperature was 120℃ and the rolling heating time was 16h.

[0110]

[0111] In the above formula, α is the mass retention rate, %; M1 is the mass of the material before hot rolling, g; and M2 is the mass of the material after hot rolling, g.

[0112] Table 1

[0113] Serial Number Leak-sealing skeleton materials prepared in different embodiments Quality retention rate (%) 1 Example 1 94.1 2 Example 4 92.6 3 Example 5 91.8 4 Example 7 95.6 5 Example 9 96.2 6 Example 11 96.9 7 Example 12 93.5 8 Comparative Example 1 90.5 9 Comparative Example 2 90.5 10 Comparative Example 3 91.2

[0114] As shown in Table 1, the leak-sealing skeleton materials prepared in the embodiments of the present invention have a higher mass retention rate after high-temperature hot rolling than the leak-sealing skeleton materials prepared by the methods of Comparative Examples 1-3, indicating that the leak-sealing skeleton materials prepared in the embodiments of the present invention have better temperature resistance. Furthermore, the mass retention rate of Example 1 is greater than that of Examples 4 and 5, indicating that the method of modifying polyurethane sponge with montmorillonite has a better temperature resistance effect than that of nano-calcium carbonate and sepiolite. The mass retention rate of Example 7 is greater than that of Example 1, indicating that the preparation method of Example 7 is more effective in improving temperature resistance. The mass retention rates of Examples 9 and 11 are greater than that of Example 7, indicating that the addition of a crosslinking agent to the mixed solution results in a better film-forming effect, further improving the temperature resistance of the leak-sealing skeleton material. Compared with Example 1, Example 12 changed the order of application of montmorillonite solution and polyvinyl alcohol solution, and the temperature resistance of the leak-sealing skeleton material prepared was worse than that of Example 1.

[0115] 2. Oil resistance test:

[0116] The diesel fuel was heated to 100°C using an oil bath. The test material was then immersed in the diesel fuel for 16 hours. After immersion, the test material was removed, dried, and its tensile strength was determined using a universal testing machine. The tensile strength retention rate was then obtained using the following formula.

[0117]

[0118] In the above formula, β is the tensile strength retention rate, %; P1 is the tensile strength of the material before immersion, kPa; and P2 is the tensile strength of the material after immersion, kPa.

[0119] Table 2

[0120] Serial Number Leak-sealing skeleton materials prepared in different embodiments Tensile strength retention rate (%) 1 Example 1 81.1 2 Example 4 78.9 3 Example 5 75.8 4 Example 7 86.6 5 Example 9 89.5 6 Example 11 92.4 7 Example 12 80.2 8 Comparative Example 1 38.7 9 Comparative Example 2 38.9 10 Comparative Example 3 40.3

[0121] The results in Table 2 show that the tensile strength retention rate of the plugging skeleton materials prepared in the embodiments of the present invention after immersion in diesel oil is greater than that of the plugging skeleton materials prepared by the methods of Comparative Examples 1-3, indicating that the plugging skeleton materials prepared in the embodiments of the present invention have excellent oil resistance. The tensile strength retention rate of Example 1 is greater than that of Examples 4 and 5, indicating that the method of modifying polyurethane sponge with montmorillonite has a better oil resistance effect than that of nano-calcium carbonate and sepiolite. The tensile strength retention rate of Example 7 is greater than that of Example 1, indicating that the preparation method of Example 7 is more effective in improving oil resistance. The tensile strength retention rates of Examples 9 and 11 are greater than that of Example 7, indicating that the addition of a crosslinking agent to the mixed solution results in a better film-forming effect, further improving the oil resistance of the plugging skeleton material. Compared with Example 1, Example 12 changed the order of application of montmorillonite solution and polyvinyl alcohol solution, and the oil resistance of the plugging skeleton material prepared was slightly worse than that of Example 1.

[0122] 3. Mechanical performance testing

[0123] The tensile strength of the elastic perforated mesh sealing skeleton material was tested in accordance with the national industry standard GB / T6344-2008 "Determination of tensile strength and elongation at break of flexible foam polymer materials".

[0124] Table 3

[0125] Serial Number Leak-sealing skeleton materials prepared in different embodiments Tensile strength (MPa) 1 Example 1 1.23 2 Example 4 0.81 3 Example 5 0.59 4 Example 7 2.92 5 Example 9 3.31 6 Example 11 5.56 7 Example 12 1.14 8 Comparative Example 1 0.17 9 Comparative Example 2 0.17 10 Comparative Example 3 0.19

[0126] The results in Table 3 show that the tensile strength of the plugging skeleton materials prepared in the embodiments of the present invention is greater than that of the plugging skeleton materials prepared by the methods of Comparative Examples 1-3, indicating that the plugging skeleton materials prepared in the embodiments of the present invention have better mechanical properties. The tensile strength of Example 1 is greater than that of Examples 4 and 5, indicating that the method of modifying polyurethane sponge with montmorillonite has a better film-forming effect than that of nano-calcium carbonate and sepiolite, thus giving the plugging skeleton material better mechanical properties. The tensile strength of Example 7 is greater than that of Example 1, indicating that the preparation method of Example 7 is more effective in improving mechanical properties. The tensile strength of Examples 9 and 11 is greater than that of Example 7, indicating that the film-forming effect is better and the mechanical properties are more excellent after adding a crosslinking agent to the mixed solution. Compared with Example 12, the order of application of montmorillonite solution and polyvinyl alcohol solution was changed, and the tensile strength of the prepared plugging skeleton material did not change significantly, indicating that the choice of raw material for coating the first layer has little impact on the overall performance of the composite film.

[0127] 4. Leak-stopping performance test

[0128] The plugging performance of the plugging skeleton materials prepared in the embodiments and comparative examples of the present invention was evaluated, and the effects of improved dispersibility and mechanical strength of the plugging skeleton materials on the plugging performance were tested.

[0129] An evaluation experiment was conducted using a wedge-shaped long crack sealing experimental device. The results of the leakage evaluation experiment are shown in the table below.

[0130] The basic formulation of the sealing fluid consists of white oil, sawdust, and ultrafine calcium carbonate. Based on the weight of the white oil, the amount of sawdust added is 3 wt%, and the amount of ultrafine calcium carbonate added is 3 wt%. The sealing skeleton material prepared in different embodiments is added to the basic formulation of the sealing fluid, and the amount added is 5 wt% of the white oil.

[0131] Table 4

[0132]

[0133] The results in Table 4 show that adding the plugging skeleton material prepared in the examples of this invention to the basic formulation of the plugging fluid significantly improves the plugging effect compared to adding the plugging skeleton material prepared in Comparative Examples 1-3. This results in the crack sealing area moving forward, significantly increasing the pressure-bearing capacity of the sealing layer, and reducing crack leakage. Compared to Examples 4 and 5, Example 1 shows that the crack sealing area moving forward and crack leakage decreasing, indicating that the method of using montmorillonite to modify polyurethane sponge has a better film-forming effect than nano-calcium carbonate and sepiolite, thus giving the plugging skeleton material better dispersibility and plugging performance. Compared to Examples 7, Example 7 shows a better plugging effect compared to Examples 4 and 5. Example 1 shows that the crack sealing area moves forward and the crack leakage decreases, indicating that the film-forming performance of the preparation method in Example 7 is better. Compared with Example 7, Examples 9 and 11 show that the crack sealing area moves forward, the pressure-bearing capacity of the sealing layer increases significantly, and the crack leakage decreases, indicating that the film-forming effect is better and the leakage-sealing performance is improved after adding a crosslinking agent to the mixed solution. Compared with Example 12, Example 1 changed the order of applying montmorillonite solution and polyvinyl alcohol solution, and the leakage-sealing performance of the prepared leakage-sealing skeleton material did not change significantly, indicating that the choice of raw material for the first coating layer has little impact on the overall performance of the composite film.

[0134] 5. Contact angle determination of composite films formed by the self-assembly of polyvinyl alcohol and montmorillonite layers on the surface of polyurethane foam.

[0135] The hydrophobicity of the leak-stopping skeleton material (polyurethane sponge with a composite film on the surface) prepared in Example 11 of the present invention was tested and evaluated by measuring the contact angle.

[0136] According to the preparation method of the leak-sealing skeleton material of the present invention, a composite film is formed on the relatively flat surface of the skeleton material polyurethane sponge, and the contact angle of water droplets on the surface of the leak-sealing skeleton material is measured using a contact angle measuring instrument; the specific results are shown in the appendix. Figure 1 .

[0137] from Figure 1 As can be seen, the contact angle is 131°, and the surface of the plugging skeleton material is obviously hydrophobic.

[0138] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A leak-sealing skeleton material, characterized in that, The leak-sealing skeleton material includes an elastic material and a deposited film coated on the surface of the elastic material; the raw materials for preparing the deposited film include polyvinyl alcohol, inorganic particles, and optionally a crosslinking agent; the elastic material is selected from sponge; Based on the total mass of the leak-sealing skeleton material, The mass percentage of elastic material is 89%–95.7%. The mass percentage of polyvinyl alcohol is 2.2% to 5.6%; The mass percentage of inorganic particles is 2.1% to 4.4%; The mass percentage of the crosslinking agent is 0% to 1%; The average particle size of the inorganic particles is 0.05 μm to 1 μm; The average particle size of the elastic material is 1 mm to 5 mm. The sponge is selected from polyurethane sponge or polyether polyol sponge; The sponge has a pore size of 10ppi to 40ppi, an open porosity of 95% to 96%, and a density of 21kg / cm³. 3 ~22kg / cm 3 ; The inorganic particles are selected from at least one of montmorillonite, nano-calcium carbonate, and sepiolite. The method for preparing the plugging skeleton material includes the following steps: 1) Apply solution I containing polyvinyl alcohol and solution II containing inorganic particles sequentially to the surface of the elastic material, or apply a mixed solution containing inorganic particles and polyvinyl alcohol to the surface of the elastic material. 2) Repeat step 1) 50 to 200 times, then dry the coated elastic material to obtain the leak-sealing skeleton material.

2. The leak-sealing skeleton material according to claim 1, characterized in that, The crosslinking agent is selected from at least one of glutaraldehyde and boric acid.

3. The leak-sealing skeleton material according to claim 1 or 2, characterized in that, The mass retention rate of the plugging skeleton material is 91.8% to 96.9%, the tensile strength is 0.59 MPa to 5.56 MPa, and the tensile strength retention rate is 75.8% to 92.4%.

4. The method for preparing the plugging skeleton material according to any one of claims 1-3, characterized in that, Includes the following steps: 1) Apply solution I containing polyvinyl alcohol and solution II containing inorganic particles sequentially to the surface of the elastic material, or apply a mixed solution containing inorganic particles and polyvinyl alcohol to the surface of the elastic material. 2) Repeat step 1) 50 to 200 times, then dry the coated elastic material to obtain the leak-sealing skeleton material.

5. The preparation method according to claim 4, characterized in that, In step 1), in solution I containing polyvinyl alcohol, solvent I is selected from water; And / or, in step 1), in solution II containing inorganic particles, solvent II is selected from at least one of water, white oil, and brine; And / or, the content of inorganic particles in solution II containing inorganic particles is 0.1 wt% to 0.5 wt%; And / or, in step 2), the drying conditions include: a temperature of 60°C to 80°C and a time of 2 hours to 8 hours.

6. The preparation method according to claim 5, characterized in that, In step 1), the polyvinyl alcohol content in solution I is 0.5 wt% to 1.0 wt%. And / or, in step 1), the salt water is selected from a 20% NaCl aqueous solution.

7. The preparation method according to any one of claims 4-6, characterized in that, In step 1), the mixed solution containing inorganic particles and polyvinyl alcohol is a mixed solution of solution I containing polyvinyl alcohol and solution II containing inorganic particles, wherein the total content of inorganic particles and polyvinyl alcohol is 10wt% to 15wt%. And / or, the mass ratio of inorganic particles to polyvinyl alcohol in the mixed solution containing inorganic particles and polyvinyl alcohol is (0.7-1):(1.5-2).

8. The preparation method according to any one of claims 4-6, characterized in that, In step 1), the mixed solution containing inorganic particles and polyvinyl alcohol also includes a crosslinking agent; And / or, the crosslinking agent content in the mixed solution containing inorganic particles and polyvinyl alcohol is 0.1wt% to 1wt%.

9. The application of a plugging skeleton material according to any one of claims 1-3 or a plugging skeleton material prepared by any one of claims 4-8 in well drilling plugging, oil production water shut-off and profile control, and well fracturing.

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