Swelling lost circulation material for fractures or caverns

Abstract

The application discloses an expansion plugging material for fracture or cave leakage, which comprises elastic plugging spheres, wherein the elastic plugging spheres adopt elastic steel wire spheres as a framework, the diameters of the elastic steel wire spheres are compressed to 1 / 2-1 / 3 of the natural state, and the elastic steel wire spheres are sealed in paraffin. The application also discloses a hydrogel water plugging agent filled in the gaps of the steel wire spheres. The preparation process of the hydrogel water plugging agent is as follows: firstly, sodium alginate and polyvinyl alcohol are respectively dissolved and mixed, the pH value of the mixed solution is adjusted to weak acidity, then the mixed solution is reacted with polyethylene glycol diglycidyl ether to prepare a multi-block copolymer, methanol is added to make the two polymers simultaneously precipitate to form a mixture of the two polymers, and finally, the mixture is mixed with triethanolamine borate and calcium lactate microcrystals to prepare a high-strength interpenetrating network hydrogel water plugging agent which is sensitive to calcium ions and borate ions. The plugging material can be easily delivered to a leakage well section, can be highly expanded, can be easily stayed and accumulated in a leakage channel to form a bridge structure, and thus the plugging success rate is improved.

Description

Technical Field

[0001] This invention relates to a plugging material, and more particularly to an expansion plugging material for leakage from cracks or karst caves, belonging to the field of oil drilling plugging technology. Background Technology

[0002] Loss in wells is a common global problem in drilling engineering, especially severe loss that occurs when drilling encounters faults, large fractures, and karst caves. This often manifests as drilling fluid loss and inability to continue drilling. In such cases, plugging the loss requires significant resources and time, and can sometimes lead to wellbore collapse, stuck pipe, overflow, blowout, etc., sometimes necessitating abandoning the well and re-laying a new one. For example, the Hubei Eba Ye 1 well, drilled in recent years, encountered karst cavernous loss, resulting in a total well fluid loss of 27,850 m³. 3 The project consumed 1484 tons of plugging material, resulted in a loss of 61.2 days, and caused economic losses exceeding 7 million yuan. Well Jiaoye 197-6FH experienced leakage in the Hanjiadian and Xiaoheba Formations, requiring 38 plugging attempts and resulting in a loss of 4834 m³. 3 The well, Shengye 3-1 in the Nanchuan work area of ​​Chongqing, encountered fractures and karst caves before reaching a depth of 400-600 meters. Despite various measures such as plugging while drilling, gel plugging, and cement injection, no significant effect was observed. A total of 156,300 cubic meters of drilling fluid was lost. The well was abandoned after 185 days of operation, resulting in an economic loss of more than 15 million yuan.

[0003] Currently, there are relatively few technologies and materials available for sealing leaks caused by karst caves. Cement is commonly used for sealing, and while conventional cement sealing is effective for small karst caves, larger caves require increased effectiveness of the cable tray structure and a large amount of filling material to form a sealing layer. Commonly used materials include gravel, sawdust, and cottonseed hulls. While these materials are economical, they are difficult to apply to large karst caves, and the cement filling often fails to create a cohesive seal. Chemical sealing materials are sometimes used, but these are expensive, unsuitable for large-scale use, and their effectiveness is poor.

[0004] The main reasons for the low success rate of traditional leak sealing methods are summarized as follows:

[0005] 1. Due to the relatively small inner diameter of the drill string and the relatively small size of the drill bit's water holes, high-concentration, large-particle plugging materials cannot be pumped to the lost well section through the drill string;

[0006] 2. Large-particle plugging materials dropped from the wellhead are limited by their density and shape. For example, cottonseed hulls, walnut shells, cement ropes, etc. have low density and insufficient weight, resulting in slow sinking speed. Some materials may not even sink under their own weight. Other materials, such as gravel and bricks, have irregular shapes and can reach smaller well inclination sections smoothly. However, if the well inclination is large, such as greater than 30°, it will be difficult for them to sink under their own weight, or they may not be able to sink at all. They will accumulate above the leaking section, leading to plugging failure.

[0007] 3. The lack of efficient filling material between cottonseed hulls, walnut shells, and cement rope makes them easily washed away by fluid in the leakage channels, resulting in a low success rate of leak sealing. Summary of the Invention

[0008] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the invention.

[0009] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0010] The purpose of this invention is to overcome the problems existing in the prior art and provide an expandable plugging material for leakage in cracks or karst caves. This material is easy to deliver to the leakage section, can expand highly, and can easily stay and accumulate in the leakage channel to form a bridge structure, thereby improving the success rate of plugging.

[0011] To solve the above technical problems, the present invention provides an expansion sealing material for leakage in cracks or karst caves, comprising an elastic sealing sphere. The elastic sealing sphere uses an elastic steel wire ball as a skeleton, and after its diameter is compressed to 1 / 2 to 1 / 3 of its natural state, it is sealed in paraffin wax.

[0012] Furthermore, the preparation method of the elastic plugging sphere is as follows: Select a steel wire ball of appropriate size, heat and melt the paraffin wax, then immerse the steel wire ball in the melted paraffin wax liquid, and at the same time compress it into a spherical shape using a spherical mesh mold. After the paraffin wax cools to room temperature and solidifies, remove it together with the mold, and demold it after cooling.

[0013] Furthermore, an additive to adjust the softening temperature of the paraffin is added to the paraffin in proportion and stirred evenly.

[0014] Furthermore, it also includes a hydrogel plugging agent for filling the gaps in the steel wool. The preparation process of the hydrogel plugging agent is as follows: First, sodium alginate and polyvinyl alcohol are dissolved and mixed separately. The pH value of the mixed solution is adjusted to weak acidity, and then reacted with polyethylene glycol diglycidyl ether to prepare a multi-block copolymer. Methanol is added to cause the two polymers to precipitate simultaneously to form a mixture of the two particles. Then, it is mixed with triethanolamine borate ester and calcium lactate microcrystals to prepare a high-strength interpenetrating network hydrogel plugging agent that is sensitive to both calcium ions and borate ions.

[0015] Furthermore, the structural formula of the multiblock copolymer is as follows:

[0016]

[0017] Furthermore, the preparation of the hydrogel water-blocking agent includes the following steps:

[0018] S1. Add 15g of sodium alginate in portions to 500mL of distilled water, sonicate to dissolve, filter through a sintered glass funnel, and collect the filtrate for later use. Add 5g of polyvinyl alcohol in portions to 100g of distilled water, heat to 95℃ with stirring, continue stirring for 3 hours to dissolve, cool to room temperature, filter through a sintered glass funnel, and collect the filtrate for later use. Then mix the two filtrates, sonicate for 2 hours, heat to 60℃, and slowly add polyethylene glycol diglycidyl ether dropwise with rapid stirring over 5 hours. After the addition is complete, continue stirring for 3 hours, cool to room temperature, adjust the pH to 5.0, slowly add 200mL of methanol, and a white solid powder will precipitate. Filter, wash 3 times with methanol, dry, and set aside for later use.

[0019] S2. Heat 0.5g of triethanolamine borate to 50°C, then add 10g of calcium lactate microcrystals with a particle size of 0.03mm to 0.05mm, and ultrasonically mix for 1 hour to allow triethanolamine borate to be fully adsorbed onto the surface and pores of the calcium lactate particles. Cool to room temperature to obtain a light yellow solid powder for later use.

[0020] S3. Mix the white solid powder obtained in S1 and the light yellow solid powder obtained in S2 and stir for 1 hour to obtain solid powder.

[0021] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The steel wool is compressed into a smaller spherical shape, which is convenient for delivery; after the paraffin melts naturally in the well, the steel wool returns to its original shape and its volume can expand by 8 to 27 times, accumulating at the leakage channel to form a bridging structure that is not easily washed away.

[0022] 2. The filler material is a multi-block gel water shut-off agent that is sensitive to both calcium ions and borate ions, prepared mainly from alginate, polyvinyl alcohol, polyethylene glycol diglycidyl ether, triethanolamine borate ester and calcium lactate microcrystals. It has strong temperature resistance, high strength and can selectively seal the water-producing layer of oil wells.

[0023] 3. Based on the fact that the prepared multi-block polymer has two segments—the GG segment of alginic acid (guluronic acid) that simultaneously complexes with calcium ions and the 1,3-propanediol segment of polyvinyl alcohol that complexes with borate ions—it selectively complexes with calcium ions and borate ions, respectively. As calcium lactate hydrolyzes to release calcium ions, combined with the calcium ions already present in the formation water, and triethanolamine borate hydrolyzes to release borate ions, through the two complexing effects, the GG segment of the alginic acid block in the water-blocking agent complexes with calcium ions, and the 1,3-propanediol segment complexes with borate ions, forming a high-strength hydrogel. This gel has high strength and strong temperature resistance, exhibiting excellent water-blocking ability. Detailed Implementation

[0024] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0026] This invention relates to an expansion plugging material for leaks in cracks or karst caves, comprising an elastic plugging sphere. The sphere uses an elastic steel wire ball as a skeleton. After compression, the diameter is reduced to 1 / 2 to 1 / 3 of the original size. According to the volume formula V=(πD^3) / 6, the volume can expand 8 to 27 times after restoring the original shape.

[0027] Meanwhile, the elastic steel wire ball is wrapped in paraffin wax to form a spherical shape, which is convenient for delivery. Since paraffin wax has the characteristics of solidifying at low temperature and melting at high temperature, after being delivered to the bottom of the well, the paraffin wax can melt at a certain wellbore temperature. After melting, the elastic steel wire ball wrapped inside is exposed and its volume expands to 8 to 27 times its original size. It accumulates at the leakage channel and forms a bridging structure that is not easily washed away.

[0028] The manufacturing process of elastic plugging spheres: Select steel wool of appropriate size; heat and melt paraffin wax, and add external admixtures in proportion, and stir evenly; then immerse the steel wool in the melted paraffin wax liquid, and at the same time use a spherical mesh mold to compress it into a spherical shape. After the paraffin wax cools to room temperature and solidifies, take it out together with the mold. After cooling, demold it to obtain the elastic plugging sphere.

[0029] The deeper the well, the higher the temperature. The approximate average geothermal gradient of the Earth's crust is 25°C per kilometer, but this gradient varies from region to region. Paraffin wax has a softening point of around 54°C. To address the varying formation temperatures at different well depths and leakage points, various product series with softening points ranging from 54°C to 150°C are obtained by adding admixtures to paraffin wax, depending on the type and proportion of these admixtures. This allows for plugging operations in different regions and at different well depths.

[0030] Meanwhile, by adding different types and proportions of weighting materials to paraffin wax, spherical plugging products of varying densities can be obtained for use in drilling fluids of different densities. For example, if the drilling fluid density is high, the density of the selected spherical plugging material should also be higher, which is more conducive to its sinking into the target well section.

[0031] After being inserted into the wellbore, the elastic plugging ball can roll freely down into the leakage channel under its own weight, and can be used in well inclination sections between 0 and 60 degrees.

[0032] The spherical sealing material reaches the leakage channel and accumulates. After standing for 0.5 to 1.5 hours, as the paraffin gradually softens, the steel wool gradually releases its compressive force, recovers its volume, and squeezes against each other, effectively sealing the leakage channel.

[0033] Since most leakage channels are irregular and have rough surfaces, steel wool can easily stick to the walls of the leakage channels, further increasing adhesion and improving the strength and stability of the cable tray.

[0034] It can be made into spheres of different sizes to be used for wells with different levels of leakage and different diameters.

[0035] After the spherical sealing material reaches the leakage channel, the paraffin melts as the temperature rises, exposing the elastic steel wool inside. The volume expands to 8 to 27 times its original size, accumulating at the leakage channel and forming a bridging structure that is not easily washed away. Then, a hydrogel sealing agent is injected as a filler material to fill the gaps between the steel wool, improving the success rate of sealing the leak.

[0036] Example 1 of preparation of hydrogel water-blocking agent

[0037] S1. Add 15g of sodium alginate (Mn=15000-17000) in portions to 500mL of distilled water, sonicate to dissolve, filter through a sintered glass funnel, and collect the filtrate for later use. Add 5g of polyvinyl alcohol (model: 1792) in portions to 100g of distilled water, heat to 95℃ with stirring, continue stirring for 3 hours to dissolve, cool to room temperature, filter through a sintered glass funnel, and collect the filtrate for later use. Then mix the two filtrates, sonicate for 2 hours, heat to 60℃, and slowly add polyethylene glycol diglycidyl ether (MN=500) dropwise with rapid stirring over 5 hours. After the addition is complete, continue stirring for 3 hours, cool to room temperature, adjust the pH to 5.0, slowly add 200mL of methanol, and a white solid powder will precipitate. Filter, wash 3 times with methanol, dry, and set aside for later use.

[0038] S2. Heat 0.5g of triethanolamine borate to 50°C, then add 10g of calcium lactate microcrystals with a particle size of 0.03mm to 0.05mm, and ultrasonically mix for 1 hour to allow triethanolamine borate to be fully adsorbed onto the surface and pores of the calcium lactate particles. Cool to room temperature to obtain a light yellow solid powder for later use.

[0039] S3. Mix the white solid powder obtained in S1 and the light yellow solid powder obtained in S2 and stir for 1 hour to obtain solid powder.

[0040] Example 2 of preparation of hydrogel water-blocking agent

[0041] Accurately weigh the solid powder sample prepared in S3 of Example 1, stir and dissolve it in water to prepare suspensions with drug concentrations of 0.5%, 1.0%, 1.5% and 2.0%, respectively. Then place the above suspensions in sealed containers and react at 60°C for 1 day, 3 days and 5 days, respectively. After cooling, take them out and measure the elongation at break and tensile strength of the gels generated at different reaction times, as shown in Table 1.

[0042] Table 1. Elongation at break and tensile strength of gels formed from sample solutions of different concentrations at 60℃

[0043]

[0044] Example 3 of preparation of hydrogel water-blocking agent

[0045] Accurately weigh the solid powder sample prepared in S3 of Example 1, stir and dissolve it in water to prepare a suspension with a drug concentration of 1.5%, place it in a sealed container, and gelatinize and age it at 250°C for 3 days, 5 days and 7 days respectively. After cooling, take it out and measure the gel strength at different aging times, as shown in Table 2.

[0046] Table 2. Anti-aging ability of gels formed from samples at 250℃

[0047]

[0048] Example 4 of preparation of hydrogel water-blocking agent

[0049] Accurately weigh the solid powder sample S3 from Example 1, add it to water, stir and disperse to prepare a 1.5% suspension. Artificial simulated rock cores with similar porosities were placed in an incubator at 60°C for 12 hours; the permeability of the cores before treatment was measured. Then, the above suspensions with different PVs were injected into the cores in reverse order, and then kept at 60°C for 3 days; the permeability of the cores after treatment with different reagent dosages was measured, as shown in Table 3.

[0050] Table 3 Core plugging rate after treatment with different reagent dosages

[0051] Cumulative displacement volume Core pressure difference Initial penetration rate Blocking rate PV MPa mDc ％ 0.1 1.55 2603 80.3 0.3 2.03 2615 88.2 0.5 3.85 2588 94.6 0.7 4.09 2606 95.8 1 7.35 2608 99.5

[0052] The above description is merely a preferred embodiment of the present invention, showing and describing the basic principles, main features, and advantages of the present invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. An expansion sealant for leaks caused by cracks or karst caves, characterized in that, Using an elastic steel wool ball as a skeleton, its diameter is compressed to 1 / 2 to 1 / 3 of its natural state and then sealed in paraffin wax to obtain an elastic plugging ball. After the elastic plugging ball reaches the leakage channel, as the temperature rises, the paraffin melts, exposing the elastic steel wool ball inside. The ball expands to 8 to 27 times its original size and accumulates at the leakage channel. Then, a hydrogel plugging agent is injected as a filling material to fill the gaps between the steel wool balls. The preparation process of the hydrogel water-blocking agent is as follows: First, sodium alginate and polyvinyl alcohol are dissolved and mixed separately, and then reacted with polyethylene glycol diglycidyl ether to prepare a multi-block copolymer. By adjusting the pH value to weak acidity, methanol is added to precipitate a white solid powder. Then, it is mixed with triethanolamine borate ester and calcium lactate microcrystals to prepare a high-strength interpenetrating network hydrogel water-blocking agent that is sensitive to both calcium ions and borate ions.

2. The expansion plugging material for leakage from cracks or karst caves according to claim 1, characterized in that, Add an additive to the paraffin wax to adjust its softening temperature, and stir until homogeneous.

3. The expansion plugging material for leakage from cracks or karst caves according to claim 1, characterized in that, The structural formula of the multiblock copolymer is as follows: 。 4. The expansion plugging material for leakage from cracks or karst caves according to claim 1, characterized in that, The preparation of the hydrogel water-blocking agent includes the following steps: S1. Add 15g of sodium alginate in portions to 500mL of distilled water, sonicate to dissolve, filter through a sintered glass funnel, and collect the filtrate for later use. Add 5g of polyvinyl alcohol in portions to 100g of distilled water, heat to 95℃ with stirring, continue stirring for 3 hours to dissolve, cool to room temperature, filter through a sintered glass funnel, and collect the filtrate for later use. Then mix the two filtrates, sonicate for 2 hours, heat to 60℃, and slowly add polyethylene glycol diglycidyl ether dropwise with rapid stirring over 5 hours. After the addition is complete, continue stirring for 3 hours, cool to room temperature, adjust the pH to 5.0, slowly add 200mL of methanol, and a white solid powder will precipitate. Filter, wash 3 times with methanol, dry, and set aside for later use. S2. Heat 0.5g of triethanolamine borate to 50°C, then add 10g of calcium lactate microcrystals with a particle size of 0.03mm to 0.05mm, and ultrasonically mix for 1 hour to allow triethanolamine borate to be fully adsorbed onto the surface and pores of the calcium lactate particles. Cool to room temperature to obtain a light yellow solid powder for later use. S3. Mix the white solid powder obtained in S1 and the light yellow solid powder obtained in S2 and stir for 1 hour to obtain solid powder.

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