Method for preparing millimeter-sized granular gel particles by one-step molding

Abstract

The present invention discloses a method for preparing millimeter-sized granular gel particles by one-time molding. The steps are as follows: (1) Add a polymeric surfactant into water, heat it to 60°C - 100°C and stir at a constant temperature for 1 h to obtain solution A; (2) Keep stirring. After solution A cools down, add an acid to adjust the pH value to pH ≤ 1, add a modifier, and stir and react for 1 h to obtain solution B; (3) Keep stirring, heat solution B to 35°C - 45°C, add a crosslinking agent thereto, and stir and react for 1 h to obtain a mixed solution containing gel particles, and separate the gel particles with a sieve. The preparation method of the present invention can directly produce gel particles without subsequent crushing, and the obtained particles are uniform, can withstand high temperatures of 90 - 130°C and water with a salinity of 21×10<supgt;4< / supgt>, can be secondarily adhered at high temperatures, and can be used for plugging large cracks.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemical gel water plugging and profile control, in particular to a method for preparing millimeter-level granular gel particles by one-time molding. Background Art

[0002] Long-term water injection development has led to the increasing heterogeneity of my country's oil fields, which has greatly affected the improvement of oil field production yield. Therefore, it is necessary to plug the high permeability channel to change the direction of water flow and improve the water injection sweep coefficient, which is of great value to increase the oil water drive recovery rate. Before plugging, the water flows directly through the cracks and holes. After the profile control and water plugging agent is injected, the water flow direction is changed, which can more effectively drive oil and improve the recovery rate.

[0003] Millimeter-scale gel is currently the most widely used type of compound for water plugging and profile control. The earliest discovered was the in-situ gel system, but this type of gel has some disadvantages. First, it is difficult to accurately control the gelation time, and it is easily affected by shear degradation and chromatographic separation, resulting in uncertainty in the gel structure composition. In addition, the in-situ gel is easily diluted by formation water. In order to overcome these defects, prefabricated particle gel was introduced. Prefabricated particle gel forms particle gel in surface facilities before being injected into the bottom layer, so it is less sensitive to the physical and chemical conditions in the reservoir, such as pH, salinity, multivalent ions, hydrogen sulfide and temperature. Therefore, it has good application prospects in profile control and water plugging.

[0004] However, the gel prepared by the conventional gel preparation method is usually in block form and needs to be cut into particles. Moreover, the gel prepared by the conventional method is difficult to stably maintain its morphology and mechanical properties under high temperature and high pressure. In order to overcome these problems, the present invention provides a method for preparing millimeter-sized gel particles by one-time molding. Summary of the invention

[0005] In view of the problem that the current gel preparation method needs to be cut into particles and cannot form and prepare millimeter-sized gel particles in one go, the present invention provides a method for forming and preparing millimeter-sized gel particles in one go.

[0006] The method for preparing millimeter-sized granular gel particles by one-step molding provided by the present invention comprises the following steps:

[0007] (1) Add a polymer surfactant into water, heat to 60°C-100°C, stir for 1 hour at a constant temperature of 250 r / min-400 r / min, and obtain solution A. The polymer surfactant is selected from hydroxymethyl cellulose, chitosan, polyvinyl alcohol, polyacrylamide, and water-soluble phenolic resin.

[0008] (2) stirring continuously, after solution A is cooled, adding acid thereto to adjust the pH value to pH ≤ 1, then adding a modifier, stirring and reacting for 1 hour, to obtain solution B; the modifier is selected from one of benzaldehyde, n-butyraldehyde, cinnamaldehyde, phenylacetaldehyde, salicylaldehyde, γ-butyrolactone, β-valerolactone, carboxylic acid ester, carboxylic acid halide, and alkyl sulfonate;

[0009] (3) stirring continuously, raising the temperature of solution B to 35°C-45°C, adding a crosslinking agent thereto, stirring and reacting for 1 hour, obtaining a mixed solution containing gel particles, and separating the gel particles with a sieve. The crosslinking agent is selected from one of terephthalaldehyde, o-phthalaldehyde, terephthalic acid, p-toluenesulfonamide, styrene-maleic anhydride copolymer, pyromellitic anhydride, 1,2,4-trimellitic anhydride, phthalic anhydride, benzophenone tetracarboxylic anhydride, 4,4-methylene diphenyl diisocyanate, 2,4-toluene diisocyanate, diisocyanate oligomers, naphthalene diisocyanate, and p-phenylene diisocyanate.

[0010] Preferably, in step (1), the mass percentage concentration of the high molecular surfactant in solution A is 7%-15%.

[0011] Preferably, in step (2), solution A is cooled to a temperature of 15° C. to 21° C. and then acid is added to adjust the pH value.

[0012] Preferably, in step (2), the mass ratio of the modifier to the high molecular surfactant is 0.15 to 0.3.

[0013] Preferably, in step (3), the content of the cross-linking agent in solution B is 0.1%-0.3%.

[0014] The particle size of the millimeter-scale granular gel particles prepared by the above method ranges from 0.1 to 5 mm.

[0015] The working principle of the preparation method of the present invention is as follows:

[0016] First, a substance containing one carbonyl group (modifier) ​​is reacted with the hydroxyl group in the polymer surfactant to allow the hydrophilic polymer to interact with the hydrophobic group. In this way, the hydrophilic group will face the inside of the polymer chain, while the hydrophobic group will be exposed on the surface. When the polymer concentration is higher than a certain critical concentration (CAC), the macromolecular chains will aggregate through hydrophobic interaction to form a physical cross-linking and chemical cross-linking network dominated by intermolecular association. This cross-linking network is formed by weak cross-linking between molecules and the continuous action of internal groups. Through the action of stirring, the gel particles are separated from the water to form metastable gel particles with a granular structure. Secondly, a substance containing two carbonyl functional groups (cross-linking agent) is used for secondary cross-linking to further strengthen the structure of the particles and make them more stable.

[0017] Compared with the prior art, the present invention is beneficial in that:

[0018] (1) The preparation method of the present invention is based on a nucleophilic reaction in an aqueous phase, where a polymer surfactant having a hydrophilic group reacts with a hydrophobic modifier (modifier) ​​containing a carbonyl group, thereby forming a series of metastable structured millimeter-sized granular materials. In order to further improve the temperature and salt resistance, a crosslinking agent is used to further improve the crosslinking, thereby obtaining stable millimeter-sized gel particles in an aqueous phase.

[0019] (2) The preparation method of the present invention is simple in process and low in cost, and can directly prepare gel particles without subsequent crushing, and the obtained particles have uniform particle size.

[0020] (3) The millimeter-sized gel particles of the present invention can withstand high temperatures of 90-130°C, 21×10 4 Mineralized water can be re-adhesive at high temperature to form a block with good mechanical properties, making it more suitable for water plugging treatment in fractured and cavernous oil reservoirs with larger fractures.

[0021] (4) The particle size can be controlled by adjusting the stirring speed; the temperature of secondary adhesion can be regulated by adjusting the amount of modifier.

[0022] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 , a diagram showing the block formed by secondary adhesion of the gel particles of Example 1-4 after being placed for 60 days.

[0024] Figure 2 , particle size distribution of gel particles prepared under different rotation speed conditions. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0026] Example 1

[0027] A method for preparing millimeter-sized granular gel particles by one-step molding, comprising the following steps:

[0028] (1) Add 8 g of polyvinyl alcohol and 90 g of water to a 250 ml round-bottom flask equipped with a stirrer, heat and stir in a water bath at 270 r / min and 100° C. for 1 h to obtain solution A;

[0029] (2) Continue stirring until solution A is cooled to 16° C., add 1.5 m 2 mol / L hydrochloric acid, and then add n-butyraldehyde, the mass ratio of n-butyraldehyde to the mass of polyvinyl alcohol is 16%, and stir for 1 hour to obtain solution B;

[0030] (3) While continuing to stir, raise the temperature of solution B to 35° C., add 0.02 g of terephthalaldehyde, and continue the reaction for 1 h to obtain a mixed solution containing gel particles, which is separated using a sieve to obtain gel particles.

[0031] Example 2

[0032] A method for preparing millimeter-sized granular gel particles by one-step molding, comprising the following steps:

[0033] (1) Add 10 g of polyacrylamide and 88 g of water to a 250 ml round-bottom flask equipped with a stirrer, heat and stir in a water bath at 300 r / min and 60° C. for 1 h to obtain solution A;

[0034] (2) Continue stirring until solution A is cooled to 18° C., add 1 mL of 2 mol / L sulfuric acid, and then add benzaldehyde, the mass ratio of benzaldehyde to the mass of polyacrylamide being 20%, and stir for 1 h to obtain solution B;

[0035] (3) While continuing to stir, raise the temperature of solution B to 40° C., add 0.015 g of p-toluenesulfonamide, and continue the reaction for 1 h to obtain a mixed solution containing gel particles, which is separated using a sieve to obtain gel particles.

[0036] Example 3

[0037] A method for preparing millimeter-sized granular gel particles by one-step molding, comprising the following steps:

[0038] (1) Add 12 g of hydroxymethyl cellulose and 86 g of water to a 250 ml round-bottom flask equipped with a stirrer, heat and stir in a water bath at a speed of 330 r / min and 60° C. for 1 h to obtain solution A;

[0039] (2) Continue stirring until solution A is cooled to 16° C., add 1.5 m 2 mol / L hydrochloric acid, and then add n-butyraldehyde, the mass ratio of n-butyraldehyde to the mass of hydroxymethyl cellulose is 24%, stir and react for 1 hour to obtain solution B;

[0040] (3) While continuing to stir, raise the temperature of solution B to 35° C., add 0.03 g of pyromellitic dianhydride, and continue the reaction for 1 h to obtain a mixed solution containing gel particles, which is separated using a sieve to obtain gel particles.

[0041] Example 4

[0042] A method for preparing millimeter-sized granular gel particles by one-step molding, comprising the following steps:

[0043] (1) Add 14 g of chitosan and 84 g of water to a 250 ml round-bottom flask equipped with a stirrer, heat and stir in a water bath at 360 r / min and 60° C. for 1 h to obtain solution A;

[0044] (2) Continue stirring until solution A is cooled to 16°C, add 1m 2mol / L sulfuric acid, then add salicylaldehyde, the mass ratio of salicylaldehyde to chitosan is 28%, stir and react for 1 hour to obtain solution B;

[0045] (3) While continuing to stir, raise the temperature of solution B to 40° C., add 0.03 g of 2,4-toluene diisocyanate, and continue the reaction for 1 hour to obtain a mixed solution containing gel particles, which is separated using a sieve to obtain gel particles.

[0046] Comparative Example 1

[0047] Add 8g of polyvinyl alcohol and 90g of water to a 250ml round-bottom flask equipped with a stirrer, heat and stir in a water bath at a speed of 270r / min and 100°C for 1h, cool the solution to 35°C, add 1.5m 2mol / L hydrochloric acid, add 0.02g of terephthalaldehyde, and continue the reaction for 1h to obtain the product.

[0048] Comparative Example 2

[0049] Add 8g of polyvinyl alcohol and 90g of water to a 250ml round-bottom flask equipped with a stirrer, heat and stir in a water bath at a speed of 270r / min and 100°C for 1h, cool the solution to 16°C, add 1.5m2mol / L hydrochloric acid, and then add n-butyraldehyde, the mass percentage of n-butyraldehyde to the mass of polyvinyl alcohol is 16%, react for 1h to obtain the product.

[0050] The particle size distribution of the gel particles obtained in the above-mentioned embodiments and comparative examples was determined by sieving method. All sieves of different mesh sizes were stacked from large to small according to the aperture, and equipped with a cover and a bottom plate. All gel particles were placed in the upper sieve, fixed on the shaker, and vibrated for 5 minutes before stopping. The particle size with the largest proportion was taken as the dominant particle size, and the analysis results are shown in Table 1.

[0051] The temperature and salt resistance and secondary adhesion of the gel particles were tested in a constant temperature aging chamber. The aging experiment was conducted at a constant temperature of 130°C and a high salt condition of 21×10 4 Mineralized water. Place the gel particles in 21×10 4In mineralized water, the gel particles were placed in an aging box at different temperatures for 2 days, then taken out and shaken several times to observe the secondary adhesion. The final results showed that the temperatures at which the gel particles of Examples 1-4 formed blocks by secondary adhesion were 90°C, 100°C, 110°C, and 130°C, respectively. The products prepared in Comparative Examples 1 and 2 did not produce secondary adhesion and were completely dissolved under high temperature and high salt conditions. The results are shown in Table 1.

[0052] Table 1. Particle size, heat and salt resistance and secondary adhesion performance of the gels obtained in Examples 1-4 and Comparative Examples 1 and 2

[0053]

[0054]

[0055] The blocks formed by the secondary adhesion of the gel particles of Examples 1-4 were placed in a 21×10 4 The mineralized water and the condition after being placed in an aging box at 130℃ for 60 days is shown in Figure 1 This indicates that the block formed by the secondary adhesion of the gel particles of the present invention still maintains good morphology after being in high temperature and high salt conditions for 60 days.

[0056] Example 5

[0057] On the basis of Example 1, the stirring speed in the preparation method is changed from 280 r / min to 300 r / min, 310 r / min, 340 r / min, and 370 r / min respectively; the other preparation processes remain unchanged, and finally gel particles at different rotation speeds are obtained. The particle size distribution of the above-mentioned various gel particles is determined by screening method. All sieves of different mesh sizes are stacked from large to small according to the aperture, and are equipped with a lid and a bottom plate. All gel particles are placed in the upper sieve, fixed on the shaker, and vibrated for 5 minutes before stopping. Calculate the percentage of the mass of particles in different particle size ranges screened out to the total mass of the particles. The calculation results are shown in Tables 2 and Figure 2 It can be concluded that the preparation method of the present invention can prepare gel particles of different particle sizes by adjusting the stirring speed during the preparation process, so as to be suitable for water plugging and profile control of different fractures.

[0058] Table 2. Particle size distribution of gel particles prepared under different rotation speed conditions

[0059]

[0060] Example 6

[0061] On the basis of Example 2, the amount of benzaldehyde was changed in step (2) of the preparation method so that the mass percentages of benzaldehyde to polyacrylamide were 21.5%, 23% and 24.5%, respectively, while the other preparation processes remained unchanged. Finally, gel particles with different degrees of modification (the degree of modification refers to the mass percentage of the modifier to the high molecular surfactant) were obtained.

[0062] The four gel particles with different modification degrees were placed in 21×10 4 In mineralized water, place it in a constant temperature box at 80°C for 2 days, take it out and shake it several times to observe the secondary adhesion. Raise the temperature to 90, 100, 110, 120, and 130°C respectively, repeat the above experiment, and observe the secondary adhesion. The experimental results show that the temperature at which the gel particles with a modification degree of 20% form a block by secondary adhesion is 90°C, the temperature at which the gel particles with a modification degree of 21.5% form a block by secondary adhesion is 100°C, the temperature at which the gel particles with a modification degree of 23% form a block by secondary adhesion is 110°C, and the temperature at which the gel particles with a modification degree of 24.5% form a block by secondary adhesion is 130°C. It can be concluded that in the preparation method of the present invention, the secondary adhesion temperature of the gel particles can be adjusted by changing the amount of the modifier (modification degree) to obtain gel particles suitable for different temperature environments.

[0063] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing millimeter-sized granular gel particles by one-step molding, characterized in that: Here are the steps: (1) adding a polymer surfactant to water, heating to 60° C.-100° C. and stirring for 1 h at a speed of 250 r / min-400 r / min to obtain a solution A; the polymer surfactant is selected from one of hydroxymethyl cellulose, chitosan, polyvinyl alcohol, polyacrylamide, and water-soluble phenolic resin; the mass percentage concentration of the polymer surfactant in solution A is 7%-15%; (2) stirring continuously, after solution A is cooled, adding acid thereto to adjust the pH value to pH ≤ 1, then adding a modifier, stirring and reacting for 1 hour, to obtain solution B; the modifier is selected from one of benzaldehyde, n-butyraldehyde, cinnamaldehyde, phenylacetaldehyde, salicylaldehyde, γ-butyrolactone, β-valerolactone, carboxylic acid ester, carboxylic acid halide, and alkyl sulfonate; the mass ratio of the modifier to the polymer surfactant is 0.15 to 0.3; (3) stirring continuously, raising the temperature of solution B to 35°C-45°C, adding a crosslinking agent thereto, stirring and reacting for 1 hour to obtain a mixed solution containing gel particles, and separating the gel particles with a sieve; the crosslinking agent is selected from one of terephthalaldehyde, o-phthalaldehyde, terephthalic acid, p-toluenesulfonamide, styrene-maleic anhydride copolymer, pyromellitic anhydride, 1,2,4-tricrimidine anhydride, phthalic anhydride, benzophenone tetracarboxylic anhydride, 4,4-methylenediphenyl diisocyanate, 2,4-toluene diisocyanate, diisocyanate oligomer, naphthalene diisocyanate, and p-phenylene diisocyanate; the content of the crosslinking agent in solution B is 0.1%-0.3%.

2. The method for preparing millimeter-sized granular gel particles by one-step molding as claimed in claim 1, characterized in that: In step (2), solution A is cooled to a temperature of 15°C-21°C and then an acid is added to adjust the pH value.

3. A millimeter-sized granular gel particle, characterized in that: The particles are prepared by the one-time molding method for preparing millimeter-sized granular gel particles as described in claim 1 or 2.

4. The millimeter-sized granular gel particles according to claim 3, characterized in that: The particle size range is 0.1-5mm.

5. The millimeter-sized granular gel particles according to claim 3, characterized in that: Used for water plugging and profile control in oil and gas fields.

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