A modified starch degradable temporary plugging agent and preparation method thereof

Abstract

The present invention relates to a modified starch degradable temporary plugging agent and a preparation and application method thereof, and belongs to the field of petrochemical industry. The preparation method comprises: S1: adding starch and solvent into a container device with stirring and heating functions, heating up to gelatinize the starch, adding copper sulfate solution after cooling down, adding hydrogen peroxide after uniformity to react, precipitating the product after the reaction is completed, filtering, drying, preparing into powder, and obtaining oxidized starch; S2: dissolving phenylhydrazine in glacial acetic acid and distilled water to obtain phenylhydrazine reagent, dissolving oxidized starch in aqueous solution, mixing with phenylhydrazine reagent and adding into a container device, heating up, and performing hydrazine reaction, after the reaction is completed, drying the product to constant weight, and obtaining a modified starch degradable temporary plugging agent. The two benzene rings in the molecular structure of the modified starch provided by the present invention greatly reduce its solubility; when the steering operation is completed, the temporary plugging agent can be gradually decomposed by heating to restore the dispersibility and degradation ability of the starch.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and particularly relates to a modified starch degradable temporary plugging agent and a preparation method thereof. Background Art

[0002] Since the 21st century, with the rapid development of social economy and science and technology, the demand for oil has continued to increase. However, due to the uneven geology of the formation, it is easy for fracturing fluid to flow into the oil well through the pores during oil extraction, seriously affecting the quality and efficiency of oil extraction. Therefore, it is necessary to use plugging agents to plug the high permeability channels to increase the production of oil wells. The difference between temporary plugging agents and conventional plugging materials is that after the diversion operation is completed, it can be manually unblocked or self-degraded under formation conditions, with little damage to the formation.

[0003] At present, temporary plugging agents are mainly divided into acid-soluble temporary plugging agents, oil-soluble temporary plugging agents and water-soluble temporary plugging agents. When acid-soluble temporary plugging agents are discharged from the formation, they need to be acidified to unblock the plugging. They cannot be dissolved or degraded by themselves. The cost of unblocking is high and the process is complicated. Oil-soluble temporary plugging agents have poor plugging effect, are difficult to dissolve in water, and have high construction costs. Water-soluble temporary plugging agents have good applicability in the oil field production process. They have the advantages of good stability, good dispersibility, and high plugging strength. After the diversion operation is completed, they can be dissolved in water-based fluids and taken out of the formation. Starch-based temporary plugging agents have good biodegradability and environmental protection, a wide range of raw materials, and low prices, but they have good solubility and poor mechanical properties. Therefore, by modifying starch to improve its plugging performance and designing modified starch temporary plugging agents with excellent performance, it can provide certain technical support for increasing oil field production and efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a modified starch degradable temporary plugging agent and a preparation method thereof. In the present invention, the starch is oxidized by hydrogen peroxide, and then a phenylhydrazine reagent is used to react with the carbonyl group in the oxidized starch to form a hydrazine to obtain the degradable temporary plugging agent.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions to achieve

[0006] A modified starch degradable temporary plugging agent, the structural formula of the temporary plugging agent is:

[0007]

[0008] On the other hand, the present invention also discloses a method for preparing a modified starch degradable temporary plugging agent, comprising the following steps:

[0009] S1: adding starch and solvent into a container device with stirring and heating functions, heating up to gelatinize the starch, cooling down and adding copper sulfate solution, adding hydrogen peroxide to react after the mixture is uniform, and after the reaction is completed, precipitating the product, filtering, drying, and preparing it into powder to obtain oxidized starch;

[0010] S2: dissolving phenylhydrazine in glacial acetic acid and distilled water to obtain phenylhydrazine reagent, dissolving oxidized starch in the aqueous solution, mixing with the phenylhydrazine reagent and adding into a container device, heating to carry out hydrazine reaction, and after the reaction is completed, drying the product to constant weight to obtain a modified starch degradable temporary plugging agent.

[0011] Furthermore, in step S1, the mass ratio of starch to solvent is 1:(8-10).

[0012] Furthermore, in step S1, the temperature is raised to 80-90° C. to gelatinize the starch for 30-40 minutes.

[0013] Furthermore, in step S1, the copper sulfate solution is added after the temperature is lowered to 50-55°C.

[0014] Furthermore, the amount of copper sulfate solution added in step S1 is 0.2% to 0.5% of the mass of starch.

[0015] Furthermore, in step S1, hydrogen peroxide is added to react for 1 to 2 hours.

[0016] Furthermore, the amount of hydrogen peroxide added in step S1 is 2% to 4% of the mass of starch.

[0017] Furthermore, in step S2, the oxidized starch is dissolved in an aqueous solution, mixed with a phenylhydrazine reagent, and then added to a container device, and the temperature is raised to 70-80° C. to perform a hydrazine reaction for 30-60 minutes.

[0018] Furthermore, in step S2, the mass ratio of phenylhydrazine, glacial acetic acid and distilled water is 1:(1-1.2):(8-10).

[0019] Furthermore, in step S2, the mass ratio of the oxidized starch solution to the phenylhydrazine reagent is 1:(0.8-1).

[0020] On the other hand, the present invention also discloses an application method of the modified starch degradable temporary plugging agent, wherein the modified starch degradable temporary plugging agent is used as a chemical agent in the process of oil production or oil and water well reconstruction.

[0021] The present invention has the following advantages:

[0022] (1) The present invention provides a modified starch degradable temporary plugging agent and its preparation and application methods. During the preparation, the starch is first oxidized with hydrogen peroxide, and then the carbonyl group in the oxidized starch is reacted with a phenylhydrazine reagent to form a sulfonate to obtain the degradable temporary plugging agent. The present invention uses a phenylhydrazine reagent to react with the carbonyl group in the oxidized starch molecule, and the α-hydroxyhydrazone is catalyzed by acid until the sulfonate is finally generated. The reaction forms a relatively stable six-membered cyclic chelate through hydrogen bonds within the molecule. The stable transition state ensures the smooth progress of the reaction and prevents other carbon atoms of the oxidized starch from continuing to react with phenylhydrazine.

[0023] (2) The two benzene rings in the molecular structure of the modified starch prepared by the present invention greatly reduce its solubility, so that it can be used as a temporary plugging agent in the process of oil production and oil and water well reconstruction. After the diversion operation is completed, the temporary plugging agent can be gradually decomposed by heating to restore the dispersibility and degradation ability of the starch.

[0024] (3) In addition, the modified starch degradable temporary plugging agent provided by the present invention has a good temporary plugging effect, a wide source of raw materials, low price, and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 The diagram is a synthesis mechanism diagram of the modified starch degradable temporary plugging agent of the present invention;

[0027] Figure 2 is the structural formula of the modified starch degradable temporary plugging agent of the present invention;

[0028] Figure 3 This is a temporary plugging effect diagram of the modified starch degradable temporary plugging agent prepared in Example 3;

[0029] Figure 4 This is the appearance morphology of the modified starch degradable temporary plugging agent prepared in 6% Example 3. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0033] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0034] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0035] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0036] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0037] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0038] like Figure 1The invention discloses a modified starch degradable temporary plugging agent, and the structural formula of the modified starch degradable temporary plugging agent is as follows: Figure 2 shown.

[0039] The specific preparation steps are as follows:

[0040] S1: Add starch and distilled water to a three-necked flask with a mechanical stirrer and a heating device, and heat it to 80-90°C to gelatinize the starch for 30-40 minutes. Then lower the temperature to 50-55°C, add a copper sulfate solution with a mass concentration of 10%, stir evenly, and slowly add hydrogen peroxide to react for 1-2 hours; after the reaction is completed, precipitate the product in anhydrous ethanol, filter it, dry it in a vacuum oven to constant weight, and finally grind it into powder to obtain oxidized starch; wherein the mass ratio of starch to distilled water is 1:(8-10), the amount of copper sulfate solution added is 0.2%-0.5% of the mass of starch, and the amount of hydrogen peroxide added is 2%-4% of the mass of starch;

[0041] S2: dissolving phenylhydrazine in glacial acetic acid and distilled water to obtain a phenylhydrazine reagent; preparing a 5% to 6% aqueous solution of oxidized starch, mixing it with the phenylhydrazine reagent and adding it into a three-necked flask, heating it to 70 to 80° C., and carrying out a hydrazine reaction for 30 to 60 minutes; after the reaction is completed, drying the product in a vacuum oven to a constant weight, thereby obtaining the modified starch degradable temporary plugging agent; wherein the mass ratio of phenylhydrazine, glacial acetic acid and distilled water is 1:(1 to 1.2):(8 to 10), and the mass ratio of the oxidized starch solution to the phenylhydrazine reagent is 1:(0.8 to 1).

[0042] The present invention will be further described below in conjunction with specific embodiments:

[0043] Example 1

[0044] S1: 20 g of starch and 160 g of distilled water are added to a three-necked flask with a mechanical stirrer and a heating device, and the temperature is raised to 80°C to gelatinize the starch for 30 minutes; then the temperature is lowered to 50°C, 0.04 g of a 10% copper sulfate solution is added, and after stirring evenly, 0.4 g of hydrogen peroxide is slowly added, and the reaction is carried out for 1 hour; after the reaction is completed, the product is precipitated in anhydrous ethanol, filtered, and then dried in a vacuum oven to constant weight, and finally ground into powder to obtain oxidized starch;

[0045] S2: 5 g of phenylhydrazine is dissolved in 5 g of glacial acetic acid and 40 g of distilled water to prepare a phenylhydrazine reagent; 20 g of oxidized starch is prepared into a 5% aqueous solution, mixed with 16 g of phenylhydrazine reagent and added into a three-necked flask, the temperature is raised to 70° C., and a phenylhydrazine reaction is carried out for 30 minutes; after the reaction is completed, the product is dried in a vacuum oven to a constant weight, and the modified starch degradable temporary plugging agent is obtained.

[0046] Example 2

[0047] S1: 20 g of starch and 200 g of distilled water are added to a three-necked flask with a mechanical stirrer and a heater, and the temperature is raised to 90°C to gelatinize the starch for 40 minutes; then the temperature is lowered to 55°C, 0.1 g of a 10% copper sulfate solution is added, and after stirring evenly, 0.8 g of hydrogen peroxide is slowly added to react for 2 hours; after the reaction is completed, the product is precipitated in anhydrous ethanol, filtered, and then dried in a vacuum oven to constant weight, and finally ground into powder to obtain oxidized starch;

[0048] S2: 5g of phenylhydrazine is dissolved in 6g of glacial acetic acid and 50g of distilled water to prepare a phenylhydrazine reagent; 20g of oxidized starch is taken to prepare a 6% aqueous solution, mixed with 20g of phenylhydrazine reagent and added into a three-necked flask, the temperature is raised to 80°C, and a phenylhydrazine reaction is carried out for 60min; after the reaction is completed, the product is dried in a vacuum oven to a constant weight, and the modified starch degradable temporary plugging agent is obtained.

[0049] Example 3

[0050] S1: Add 20g of starch and 180g of distilled water into a three-necked flask with a mechanical stirrer and a heating device, heat it to 80°C to gelatinize the starch for 40 minutes; then lower the temperature to 50°C, add 0.08g of 10% copper sulfate solution, stir evenly, then slowly add 0.6g of hydrogen peroxide, and react for 1 hour. After the reaction is completed, the product is precipitated in anhydrous ethanol, filtered, and then dried in a vacuum oven to constant weight, and finally ground into powder to obtain oxidized starch;

[0051] S2: 6 g of phenylhydrazine is dissolved in 7 g of glacial acetic acid and 50 g of distilled water to prepare a phenylhydrazine reagent; 20 g of oxidized starch is taken to prepare a 5% aqueous solution, mixed with 18 g of phenylhydrazine reagent and added into a three-necked flask, the temperature is raised to 80° C., and a phenylhydrazine reaction is carried out for 40 minutes; after the reaction is completed, the product is dried in a vacuum oven to a constant weight, and the modified starch degradable temporary plugging agent is obtained.

[0052] Example 4

[0053] S1: 20 g of starch and 190 g of distilled water are added to a three-necked flask with a mechanical stirrer and a heater, and the temperature is raised to 90°C to gelatinize the starch for 30 minutes; then the temperature is lowered to 50°C, 0.06 g of a 10% copper sulfate solution is added, and after stirring evenly, 0.6 g of hydrogen peroxide is slowly added, and the reaction is carried out for 2 hours; after the reaction is completed, the product is precipitated in anhydrous ethanol, filtered, and then dried in a vacuum oven to constant weight, and finally ground into powder to obtain oxidized starch;

[0054] S2: 6 g of phenylhydrazine is dissolved in 6 g of glacial acetic acid and 60 g of distilled water to prepare a phenylhydrazine reagent; 20 g of oxidized starch is taken to prepare a 6% aqueous solution, mixed with 20 g of phenylhydrazine reagent and added into a three-necked flask, the temperature is raised to 70° C., and a phenylhydrazine reaction is carried out for 60 minutes; after the reaction is completed, the product is dried in a vacuum oven to a constant weight, and the modified starch degradable temporary plugging agent is obtained.

[0055] Example 5

[0056] S1: Add 20g of starch and 180g of distilled water into a three-necked flask with a mechanical stirrer and a heating device, heat it to 90°C to gelatinize the starch for 30 minutes; then lower the temperature to 55°C, add 0.07g of 10% copper sulfate solution, stir evenly, then slowly add 0.7g of hydrogen peroxide, and react for 2 hours. After the reaction is completed, the product is precipitated in anhydrous ethanol, filtered, and then dried in a vacuum oven to constant weight, and finally ground into powder to obtain oxidized starch;

[0057] S2: 8g of phenylhydrazine is dissolved in 9g of glacial acetic acid and 70g of distilled water to prepare phenylhydrazine reagent. 20g of oxidized starch is prepared into a 5% aqueous solution, mixed with 19g of phenylhydrazine reagent and added into a three-necked flask, heated to 80°C, and reacted for 30min; after the reaction, the product is dried in a vacuum oven to constant weight, and the modified starch degradable temporary plugging agent is obtained.

[0058] Example 6

[0059] S1: 20 g of starch and 200 g of distilled water are added to a three-necked flask with a mechanical stirrer and a heating device, and the temperature is raised to 80°C to gelatinize the starch for 40 minutes; then the temperature is lowered to 50°C, 0.06 g of a 10% copper sulfate solution is added, and after stirring evenly, 0.8 g of hydrogen peroxide is slowly added, and the reaction is carried out for 1 hour; after the reaction is completed, the product is precipitated in anhydrous ethanol, filtered, and then dried in a vacuum oven to constant weight, and finally ground into powder to obtain oxidized starch;

[0060] S2: 8 g of phenylhydrazine is dissolved in 8 g of glacial acetic acid and 70 g of distilled water to prepare a phenylhydrazine reagent; 20 g of oxidized starch is taken to prepare a 6% aqueous solution, mixed with 20 g of phenylhydrazine reagent and added into a three-necked flask, the temperature is raised to 80° C., and a phenylhydrazine reaction is carried out for 50 minutes; after the reaction is completed, the product is dried in a vacuum oven to a constant weight, and the modified starch degradable temporary plugging agent is obtained.

[0061] Performance Characterization

[0062] In order to evaluate the temporary plugging effect of the modified starch degradable temporary plugging agent, the temporary plugging agent prepared in Example 3 was used to plug the artificial fracture core and the plugging rate was tested. After the test, the ambient temperature was raised to 150°C, and the formation water was used to flush it and the unblocking rate was tested. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that with the increase of temporary plugging agent concentration, the temporary plugging rate and unblocking rate first increase rapidly and then tend to stabilize. When the temporary plugging agent concentration is 6%, the plugging rate and unblocking rate of fracture cores reach more than 90%, indicating that it has a good temporary plugging effect.

[0063] Figure 4 The appearance morphology of the temporary plugging agent prepared in Example 3 is 6%. Figure 4 It can be seen that the temporary plugging agent prepared in Example 3 has a relatively large viscosity and can be used as a temporary plugging agent in the process of oil production and oil and water well reconstruction.

[0064] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a modified starch degradable temporary plugging agent, characterized in that: The following steps are involved: S1: adding starch and solvent into a container device with stirring and heating functions, heating up to gelatinize the starch, cooling down and adding copper sulfate solution, adding hydrogen peroxide to react after the mixture is uniform, and after the reaction is completed, precipitating the product, filtering, drying, and preparing it into powder to obtain oxidized starch; S2: dissolving phenylhydrazine in glacial acetic acid and distilled water to obtain phenylhydrazine reagent, dissolving oxidized starch in the aqueous solution, mixing with the phenylhydrazine reagent and adding into a container device, heating to carry out hydrazine reaction, and after the reaction is completed, drying the product to constant weight to obtain a modified starch degradable temporary plugging agent.

2. The method for preparing a modified starch degradable temporary plugging agent according to claim 1, wherein the mass ratio of starch to solvent in step S1 is 1:(8-10).

3. The method for preparing a modified starch degradable temporary plugging agent according to claim 1, wherein the temperature in step S1 is raised to 80-90°C to allow the starch to gelatinize for 30-40 minutes.

4. The method for preparing a modified starch degradable temporary plugging agent according to claim 1, wherein the copper sulfate solution is added after the temperature is lowered to 50-55°C in step S1.

5. The method for preparing a modified starch degradable temporary plugging agent according to claim 4, wherein the amount of copper sulfate solution added in step S1 is 0.2% to 0.5% of the mass of starch.

6. The method for preparing a modified starch degradable temporary plugging agent according to claim 1, wherein the amount of hydrogen peroxide added in step S1 is 2% to 4% of the mass of the starch.

7. The method for preparing a modified starch degradable temporary plugging agent according to claim 1, wherein in step S2, the oxidized starch is dissolved in an aqueous solution, mixed with a phenylhydrazine reagent, and then added to a container device, the temperature is raised to 70-80° C., and a hydrazine reaction is carried out for 30-60 minutes.

8. The method for preparing a modified starch degradable temporary plugging agent according to claim 1, wherein the mass ratio of the oxidized starch solution to the phenylhydrazine reagent in step S2 is 1:(0.8-1).

9. An application of a modified starch degradable temporary plugging agent, wherein the temporary plugging agent is prepared by the preparation method of the modified starch degradable temporary plugging agent according to any one of claims 1 to 8, wherein the modified starch degradable temporary plugging agent is used as a chemical agent in the process of oil extraction or oil and water well reconstruction.

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