Dual-ion sensitive hydrogel water plugging agent and preparation method thereof

Abstract

The invention discloses a dual-ion sensitive hydrogel water plugging agent and a preparation method thereof. Sodium alginate and polyvinyl alcohol are first dissolved and then mixed, the pH value of the mixed solution is adjusted to weak acidity, and then a multi-block copolymer is prepared by reaction with polyethylene glycol diglycidyl ether, methanol is added, and two polymers are precipitated at the same time to generate a mixture of the two particles, and then the mixture is mixed with triethanolamine borate and calcium lactate microcrystals to prepare a high-strength interpenetrating network hydrogel water plugging agent that is sensitive to calcium ions and borate ions at the same time. The multi-block polymer in the composite system has a G-G segment of alginate and a 1,3-propylene glycol segment of polyvinyl alcohol, and the two segments respectively produce selective complexation to calcium ions and borate ions, and the weak acid calcium and triethanolamine borate in the system can release calcium ions and borate ions, and the system generates a high-strength hydrogel through two complexation reactions. The gel has high strength, strong temperature resistance, and reliable preparation process.

Description

Technical Field

[0001] The invention relates to a hydrogel water plugging agent, in particular to a dual-ion sensitive hydrogel water plugging agent. The invention also relates to a preparation method of the dual-ion sensitive hydrogel water plugging agent, and belongs to the technical field of oilfield production additives. Background Art

[0002] The problems encountered in horizontal well water plugging technology are complex, and the performance requirements of the plugging agent are high. At present, the domestic horizontal well water plugging still continues the traditional water plugging technology. The water plugging agents used for horizontal well water plugging are mainly cement, gel, resin, etc. In general, the success rate of water plugging is not high, and some successful experiences cannot be replicated and promoted. Especially for bottom water reservoirs mined by horizontal wells, the bottom water cone advances rapidly during the mining process. After the horizontal well sees water, the water content increases rapidly, and the oil production decreases rapidly. At the same time, horizontal wells in bottom water reservoirs have the possibility of multiple water outlets or potential multiple water outlets, making water plugging operations more difficult. Therefore, the development of a high-strength water plugging agent is an actual need for the current development and production of horizontal wells.

[0003] Alginate is a natural polysaccharide formed by the linear copolymer of β-D-mannuronic acid (M) and α-L-guluronic acid (G) through 1,4-bonding. The content of G and M in alginate has a significant effect on its gelling properties. Since the GG segment has a chelating structure between the two monosaccharides, it exhibits a strong complexing ability with calcium ions; polyvinyl alcohol is a polyhydroxy linear polymer, and its closely arranged hydroxyl groups have a strong complexing effect on borate ions. The alginate-polyvinyl alcohol complex is sensitive to both calcium ions and borate ions. The hydrogel generated after the complexation of the two ions is strong and has strong temperature resistance. It can produce good plugging ability for strong water-producing formations, especially horizontal well bottom water that is currently difficult to plug. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract of the specification of this application and the title of the invention, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] The primary purpose of the present invention is to overcome the problems existing in the prior art and provide a method for preparing a dual-ion sensitive hydrogel water plugging agent. The prepared hydrogel water plugging agent is sensitive to calcium ions and borate ions at the same time and has a high-strength interpenetrating network. The preparation process is reliable, and the prepared gel has high strength and strong temperature resistance.

[0007] In order to solve the above technical problems, the preparation method of the dual ion sensitive hydrogel water plugging agent of the present invention comprises the following steps: firstly, sodium alginate and polyvinyl alcohol are dissolved separately and then mixed, 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 precipitate the two polymers at the same time to generate mixture particles of the two polymers, and then the mixture is mixed with triethanolamine borate and calcium lactate microcrystals to prepare a high-strength interpenetrating network hydrogel water plugging agent that is sensitive to both calcium ions and borate ions.

[0008] Furthermore, the structural formula of the multi-block copolymer is as follows:

[0009]

[0010] Furthermore, the preparation method of the dual-ion sensitive hydrogel water plugging agent comprises the following steps in sequence:

[0011] S1. Add 15g of sodium alginate to 500mL of distilled water in batches, dissolve it by ultrasonic oscillation, filter it through a sand core funnel, collect the filtrate and set it aside; add 5g of polyvinyl alcohol to 100g of distilled water in batches, heat it to 95°C under stirring, continue stirring for 3 hours, dissolve it, cool it to room temperature, filter it through a sand core funnel, collect the filtrate and set it aside; then mix the two filtrates, ultrasonically oscillate for 2 hours, heat it to 60°C, and slowly drop polyethylene glycol diglycidyl ether under rapid stirring for 5 hours. After the drop is complete, continue stirring and reacting for 3 hours, cool it to room temperature, adjust the pH value to 5.0, slowly add 200ml of methanol, precipitate a white solid powder, filter it, wash it with methanol 3 times, dry it and set it aside;

[0012] 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, mix with ultrasonic oscillation for 1 hour to allow triethanolamine borate to be fully adsorbed on the surface and pores of calcium lactate particles, cool to room temperature, and obtain a light yellow solid powder for use;

[0013] S3. The white solid powder obtained in S1 and the light yellow solid powder obtained in S2 were mixed and stirred for 1 hour to obtain a solid powder.

[0014] Another object of the present invention is to overcome the problems existing in the prior art and provide a dual ion-sensitive hydrogel water plugging agent that is sensitive to calcium ions and borate ions at the same time and has a high-strength interpenetrating network, high gel strength and strong temperature resistance.

[0015] In order to solve the above technical problems, the dual-ion sensitive hydrogel water plugging agent of the present invention is prepared by the above preparation method.

[0016] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The present invention uses alginate, polyvinyl alcohol, polyethylene glycol diglycidyl ether, triethanolamine borate and calcium lactate microcrystals as main raw materials to prepare a multi-block gel water plugging agent that is sensitive to both calcium ions and borate. It has strong temperature resistance and high strength, and can selectively plug the water-producing layer of the oil well to achieve the purpose of plugging water and increasing production.

[0017] 2. Based on the prepared multi-block polymer, the GG segment (guluronic acid) of alginate that simultaneously complexes calcium ions and the 1,3-propylene glycol segment of polyvinyl alcohol that complexes borate ions selectively complex calcium ions and borate ions respectively; as calcium lactate hydrolyzes calcium ions and the original calcium ions in the formation water, triethanolamine borate hydrolyzes borate ions. Through the two complexing effects, the GG segment in the alginate block in the water plugging agent is complexed with calcium ions, and the 1,3-propylene glycol segment is complexed with borate ions to form a high-strength hydrogel. The gel has high strength, strong temperature resistance, and exhibits excellent water plugging ability. DETAILED DESCRIPTION

[0018] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below in combination with the specifics. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0020] Example 1

[0021] S1. Add 15g sodium alginate (Mn=15000-17000) in batches to 500mL distilled water, dissolve under ultrasonic oscillation, filter through a sand core funnel, collect the filtrate and set aside; add 5g polyvinyl alcohol (model: 1792) in batches to 100g distilled water, heat to 95°C under stirring, continue stirring for 3 hours, dissolve, cool to room temperature, filter through a sand core funnel, collect the filtrate and set aside; then mix the two filtrates, oscillate ultrasonically for 2 hours, heat to 60°C, and slowly drop polyethylene glycol diglycidyl ether (MN=500) under rapid stirring for 5 hours. After the drop is complete, continue stirring and react for 3 hours, cool to room temperature, adjust the pH value to 5.0, slowly add 200ml methanol, precipitate a white solid powder, filter, wash with methanol 3 times, dry and set aside;

[0022] 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, mix with ultrasonic oscillation for 1 hour to allow triethanolamine borate to be fully adsorbed on the surface and pores of calcium lactate particles, cool to room temperature, and obtain a light yellow solid powder for use;

[0023] S3. The white solid powder obtained in S1 and the light yellow solid powder obtained in S2 were mixed and stirred for 1 hour to obtain a solid powder.

[0024] Example 2

[0025] The solid powder sample prepared by S3 in Example 1 was accurately weighed, dissolved in clean water with stirring, and suspensions with drug concentrations of 0.5%, 1.0%, 1.5% and 2.0% were prepared. The above suspensions were then placed in sealed cans, reacted at 60°C for 1 day, 3 days and 5 days, respectively, cooled, and taken out to measure the elongation at break and tensile strength of the gels generated at different reaction times, as shown in Table 1.

[0026] Table 1 Elongation at break and tensile strength of gels generated from sample solutions of different concentrations at 60°C

[0027]

[0028] Example 3

[0029] The solid powder sample prepared by S3 in Example 1 was accurately weighed, dissolved in clean water by stirring to prepare a suspension with a drug concentration of 1.5%, placed in a sealed jar, and gelled and aged at 250°C for 3 days, 5 days and 7 days, respectively, cooled, taken out, and the gel strength after different aging times was measured, as shown in Table 2.

[0030] Table 2 Anti-aging ability of gel generated by samples at 250℃

[0031]

[0032] Example 4

[0033] The solid powder sample of S3 in Example 1 was accurately weighed, added to clean water, stirred and dispersed, and prepared into a 1.5% suspension. Artificial simulated cores with similar porosity 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 reversely injected into the cores, and then kept at 60°C for 3 days; the permeability of the cores after treatment with different dosages of agents was measured, as shown in Table 3.

[0034] Table 3 Core plugging rate after treatment with different dosages of reagents

[0035] Cumulative displacement volume Core pressure difference Initial permeability Blockage rate PV MPa mxDV ％ 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

[0036] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A method for preparing a dual-ion sensitive hydrogel water plugging agent, characterized in that: First, sodium alginate and polyvinyl alcohol are dissolved separately and then mixed. 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 precipitate the two polymers at the same time to form a mixture of the two polymers. The mixture is then mixed with triethanolamine borate and calcium lactate microcrystals to prepare a high-strength interpenetrating network hydrogel water plugging agent that is sensitive to both calcium ions and borate ions.

2. The method for preparing the dual ion sensitive hydrogel water plugging agent according to claim 1, characterized in that: The structural formula of the multi-block copolymer is as follows:

3. A method for preparing a dual-ion sensitive hydrogel water plugging agent, characterized in that: The steps are as follows: S1. Add 15g of sodium alginate to 500mL of distilled water in batches, dissolve it by ultrasonic oscillation, filter it through a sand core funnel, collect the filtrate and set it aside; add 5g of polyvinyl alcohol to 100g of distilled water in batches, heat it to 95°C under stirring, continue stirring for 3 hours, dissolve it, cool it to room temperature, filter it through a sand core funnel, collect the filtrate and set it aside; then mix the two filtrates, ultrasonically oscillate for 2 hours, heat it to 60°C, and slowly drop polyethylene glycol diglycidyl ether under rapid stirring for 5 hours. After the drop is complete, continue stirring and reacting for 3 hours, cool it to room temperature, adjust the pH value to 5.0, slowly add 200ml of methanol, precipitate a white solid powder, filter it, wash it with methanol 3 times, dry it and set it aside; 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, mix with ultrasonic oscillation for 1 hour to allow triethanolamine borate to be fully adsorbed on the surface and pores of calcium lactate particles, cool to room temperature, and obtain a light yellow solid powder for use; S3. The white solid powder obtained in S1 and the light yellow solid powder obtained in S2 were mixed and stirred for 1 hour to obtain a solid powder.

4. A dual ion sensitive hydrogel water plugging agent, characterized in that: Prepared by the preparation method of claim 1, 2 or 3.

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