Environment-friendly fluid loss additive and preparation method thereof

Abstract

The application discloses an environment-friendly filtrate reducer and a preparation method thereof, and relates to the technical field of oil fields. In the preparation process of the filtrate reducer, an intermediate is prepared from chitosan and 4-nitrobenzoyl chloride, and then the intermediate is modified by using a modified monomer. The prepared filtrate reducer is based on chitosan with good environmental protection performance, and is modified by using 4-nitrobenzoyl chloride and a first monomer. The prepared filtrate reducer not only has good environmental protection performance, but also has the advantages of fast dissolving speed, easy dissolution in an alkaline aqueous solution, good temperature resistance and salt resistance, and good filtrate reduction performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oilfield chemical technology, and particularly relates to an environment-friendly filtrate reducer and a preparation method thereof. BACKGROUND

[0002] In the process of wall building, the drilling fluid can form a filter cake through filtration, thereby protecting the well wall and avoiding further filtration of the drilling fluid. However, when the filter cake filtration loss is too large in the process of forming the filter cake, not only the drilling cost is increased, but also the drilling fluid filtered into the reservoir is easy to cause shale hydration and swelling, thereby causing well wall instability. In addition, the increase in the filter cake thickness reduces the well diameter, causing a large torque to the rotating drilling tool, and causing pumping and pressure fluctuation when tripping, which is easy to cause differential pressure sticking.

[0003] Obviously, the filter cake is formed at the same time when the drilling fluid is filtered. When the drilling fluid is filtered again, it must pass through the formed filter cake. Therefore, the main factor determining the amount of filtration is the permeability of the filter cake. How to form a high-quality filter cake with low permeability to prevent further filtration of the drilling fluid is one of the main problems to be considered in the preparation of the drilling fluid. Therefore, in the drilling fluid, a filtrate reducer is usually added to control the filtration loss of the drilling fluid in the wall building process, so that the filtration loss of the drilling fluid is controlled within a reasonable range.

[0004] Chitosan is an excellent natural polysaccharide, which is abundant in nature and easy to obtain, and has good environmental performance. The original chitosan is not soluble in water, therefore, the chitosan applied to the drilling fluid is water-soluble chitosan with a high degree of deacetylation. However, the conventional water-soluble chitosan is not resistant to salt and alkali and not resistant to high temperature, therefore, the chitosan applied to the drilling fluid usually needs to be modified. The existing modification method is usually to quaternize the chitosan and graft acrylamide polymer, which on the one hand increases the adsorption performance of the modified chitosan, and on the other hand makes it have a certain shale inhibition effect, and at the same time enhances the water solubility of the chitosan. However, such modification on the one hand is difficult to improve the temperature resistance and salt resistance of the chitosan, and on the other hand, the grafted acrylamide polymer is difficult to degrade even after the degradation of the chitosan itself, and the environmental performance is greatly reduced. SUMMARY

[0005] In view of the above technical problems, the present application aims at the defects of the prior art, and provides an environment-friendly filtrate reducer and a preparation method thereof.

[0006] The present application adopts the following technical scheme: a preparation method of an environment-friendly filtrate reducer, comprising the following steps in terms of weight parts:

[0007] 10 parts of chitosan are added to tetrahydrofuran and ultrasonically dispersed, and then a catalyst and an acid-binding agent are added and dissolved to obtain a chitosan dispersion; 2-5 parts of 4-nitrobenzoyl chloride are dissolved in tetrahydrofuran to obtain a reaction solution, which is added dropwise to the chitosan dispersion at 0-4°C with continuous stirring. The reaction is continued for 1-4 hours. After the reaction is completed, the intermediate is separated and purified to obtain the intermediate;

[0008] 10 parts of the intermediate are dissolved in water and the pH of the solution is adjusted to alkaline to obtain an intermediate solution; 8 to 12 parts of the modified monomer are added to water and the pH of the solution is adjusted to alkaline to obtain a monomer solution; the monomer solution is dropwise added to the intermediate solution at 50 to 70° C., the reaction is carried out for 2 to 5 hours after the dropwise addition is completed, and the modified monomer is separated and purified after completion of the reaction; the modified monomer is at least one of sodium 2-acrylamido-2-methylpropanesulfonate, monoglyceride of methacrylate, and polyethylene glycol monomethyl ether acrylate.

[0009] In the present invention, nitrobenzoyl groups are first grafted onto the surface of chitosan. Chitosan contains amino and hydroxyl reactive groups. Although the amino group is theoretically more reactive, it is too late to protonate at low temperatures. Therefore, 4-nitrobenzoyl chloride is more likely to react with the hydroxyl groups on the chitosan surface. Chitosan is relatively solvent-free. In the present invention, tetrahydrofuran (THF) is used as a dispersant, with reference to the properties of the various materials. This dispersant can disperse chitosan to a certain extent, thereby facilitating the reaction between chitosan and 4-nitrobenzoyl chloride. Because 4-nitrobenzoyl chloride contains a benzene ring, grafting it onto chitosan can effectively increase the water resistance of chitosan. Highly deacetylated chitosan, due to its rich amino and hydroxyl groups, theoretically possesses strong hydrophilicity. However, because these amino and hydroxyl groups readily form intramolecular hydrogen bonds, it is practically insoluble in water. To make it soluble in water, it is necessary to either protonate it with dilute acid or graft the chitosan with groups carrying positive charges (quaternary ammonium groups) or negative charges (carboxylic acid groups). In this invention, the 4-nitrobenzoyl chloride used contains a nitro group, which also carries a negative charge, and can improve the water solubility of chitosan.

[0010] In particular, for the modified monomer, the molecular weight of polyethylene glycol monomethyl ether acrylate can be 800~2000. These three modified monomers can be used alone or in combination. When used in combination, sodium 2-acrylamido-2-methylpropanesulfonate can further increase the temperature resistance of the fluid loss agent, and monoglyceride methacrylate and polyethylene glycol monomethyl ether acrylate can both increase the adsorption performance of the fluid loss agent, thereby increasing the fluid loss performance.

[0011] In the second step of the present application, the chitosan is further modified by the reaction of the residual amino groups in the chitosan and the modified monomer, which not only increases the water solubility, temperature resistance and salt resistance of the chitosan, but also enriches the branched chains of the chitosan, so that the fluid loss performance of the chitosan is improved.

[0012] In an embodiment of the present application, the chitosan refers to the chitosan with a deacetylation degree greater than 85%. For the chitosan, the higher the deacetylation degree is, the better the water solubility is, but the higher the cost is. Therefore, in the actual production process, the chitosan with a deacetylation degree of 85% to 90% can be used.

[0013] In an embodiment of the present application, the modified monomer is a mixture of monoglyceride methacrylic acid and polyethylene glycol monomethyl ether acrylate with a mass ratio of 1:1 to 2. The polyhydroxy structure of the monoglyceride methacrylic acid and the oxygen atoms in the polyethylene glycol monomethyl ether acrylate can make the chitosan main chain more easily adsorbed on the well wall, so as to enhance the fluid loss performance of the chitosan. The comb structure of long and short chains also makes the adsorption performance better and the fluid loss effect better. Of course, other combinations, such as the combination of 2-acrylamido-2-methylpropane sulfonic acid sodium and polyethylene glycol monomethyl ether acrylate, or even the combination of the three, can be applied to the present application. When the materials are combined in pairs or even in three, they can be set arbitrarily, such as the mass ratio of 2-acrylamido-2-methylpropane sulfonic acid sodium and polyethylene glycol monomethyl ether acrylate can be set to 1:9, 2:8 or 9:1, which all have good fluid loss effect.

[0014] In an embodiment of the present application, in the preparation process of the intermediate, the pH of the chitosan dispersion liquid and the monomer solution is between 9 and 11.

[0015] In an embodiment of the present application, the catalyst is 4-dimethylamino pyridine, and the addition amount is 0.07 to 0.2 parts. Although a catalyst is not needed in the reaction process of the acyl chloride and the alcohol hydroxyl group in some reactions, in the present application, the 4-nitrobenzoyl chloride has a benzene ring with large steric hindrance, and the benzene ring reduces the activity of the acyl chloride. Therefore, the addition of the catalyst can better accelerate the reaction. The acid binding agent is one of triethylamine and sodium ethoxide, and the molar ratio of the 4-nitrobenzoyl chloride to the acid binding agent is 1:1 to 1.2.

[0016] In an embodiment of the present application, the separation and purification step of the intermediate is as follows: the reaction product is taken, the solid phase is obtained by centrifugation, the solid phase is washed several times with diethyl ether, and then dried to obtain the product. In theory, in this step, the solid phase can also be obtained by filtration, suction filtration and other methods. However, in the actual operation process, the chitosan can block the filter paper, resulting in slow filtration and suction filtration, which is difficult to be applied on a large scale.

[0017] One embodiment of the present application is that the separation and purification step of the environment-friendly fluid loss additive is: taking the product, removing low-boiling substances by vacuum distillation, taking the solid phase, adding methanol or ethanol to wash the solid phase several times, and then drying to obtain the product. The vacuum distillation referred to herein can be replaced by conventional rotary evaporation, or atmospheric distillation can be used.

[0018] Another object of the present application is to disclose an environment-friendly fluid loss additive prepared by any of the above methods.

[0019] The present application has the following beneficial effects: the fluid loss additive prepared by the present application is based on chitosan with good environmental performance, and is modified by 4-nitrobenzoyl chloride and modified monomers. The final prepared fluid loss additive not only has good environmental performance, but also has fast dissolution speed, is easy to dissolve in alkaline aqueous solution, has good temperature resistance and salt resistance, and has good fluid loss performance. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, objects and beneficial effects of the present application, the technical solutions of the present application will be described in detail below in conjunction with examples, but it should not be understood as limiting the scope of the present application.

[0021] In the following examples, the methods used are conventional operating methods in the art, unless otherwise specified.

[0022] In the following examples, the medicines used are conventional commercial products, unless otherwise specified.

[0023] In the following examples, the deacetylation degree of chitosan one is 85%, and the deacetylation degree of chitosan two is 95%.

[0024] In the following examples, the parts are weight parts, unless otherwise specified.

[0025] In Example 1, 100 parts of chitosan one were added to tetrahydrofuran, and ultrasonic was applied for 30 min to uniformly disperse them. Under the condition of continuous stirring, 1.2 parts of 4-dimethylaminopyridine and 25 parts of triethylamine were added, and after the chitosan was dissolved, a chitosan dispersion liquid was obtained. 40 parts of 4-nitrobenzoyl chloride were dissolved in tetrahydrofuran to obtain a reaction liquid. The chitosan dispersion liquid and the reaction liquid were pre-cooled under ice bath conditions, and then the reaction liquid was added dropwise into the chitosan dispersion liquid under continuous reaction conditions. The reaction was continued for 2 h, and after the reaction was completed, the solid phase was obtained by centrifugation at 2000 r / min for 10 min. The solid phase was washed with ether several times, and then dried at 60°C to obtain an intermediate.

[0026] Take 100 parts of the intermediate, add water to dissolve it and add sodium hydroxide to adjust the pH of the solution to 10 to obtain an intermediate solution, take 40 parts of monoglyceride methacrylate and 50 parts of polyethylene glycol monomethyl ether acrylate (molecular weight 1000), add water to dissolve it and add sodium hydroxide to adjust the pH to 9 to obtain a monomer solution, under the condition of 60℃, the monomer solution is added to the intermediate solution dropwise, after the dropwise addition is completed, continue to react for 3.5h, after the reaction is completed, remove the low boiling point substance by distillation under reduced pressure, then take the solid phase, wash the solid phase with methanol several times, and dry under the condition of 60℃ to obtain the filtrate loss reducer.

[0027] Example 2, compared with example 1, the difference is that chitosan one is replaced by chitosan two, and the rest is the same.

[0028] Example 3, compared with example 1, the difference is that in the preparation process of the intermediate, the amount of 4-nitrobenzoyl chloride is 25 parts, and in the preparation process of the filtrate loss reducer, monoglyceride methacrylate is replaced by 2-acrylamido-2-methylpropane sulfonic acid sodium, and the rest is the same.

[0029] Example 4, compared with example 1, the difference is that in the preparation process of the filtrate loss reducer, 40 parts of monoglyceride methacrylate and 50 parts of polyethylene glycol monomethyl ether acrylate (molecular weight 1000) are replaced by 80 parts of monoglyceride methacrylate, and the rest is the same.

[0030] Comparative example 1, compared with example 1, the difference is that in the preparation process of the intermediate, 4-nitrobenzoyl chloride is replaced by benzoyl chloride, and the rest is the same; in the preparation process of the filtrate loss reducer, the water solubility of the intermediate is poor, so 1% of acetic acid is added to help dissolution; but in the second step of the reaction, there is still a lot of precipitate generated in the reaction process.

[0031] In order to further illustrate the effect of the embodiment of the present application, the following specific method is used for testing.

[0032] 1. Dissolution rate test

[0033] Take the filtrate loss reducer prepared in examples 1~4, add it to water with a pH of 9 (adjust the pH with sodium carbonate) according to a mass ratio of 4wt%, under the condition of 100r / min, fast stirring, observe the dissolution time, record the interval time of 30s, and finally as shown in table 1, wherein the blank is the dissolution time of 4wt% chitosan one in an aqueous solution with an acetic acid content of 3wt%.

[0034] Table 1 dissolution rate test table

[0035]

[0036] From table 1, the filtrate reducer prepared by the embodiment of the application can be quickly dissolved in alkaline aqueous solution; and the conventional phenomenon is similar, for the blank, the dissolution speed is slower, and a small amount of insoluble substance is left after dissolution.

[0037] 2, filtrate reduction performance

[0038] According to the method shown in the Q / SH 0047-2007 general technical requirements for salt-resistant and high-temperature-resistant filtrate reducer for drilling fluid, fresh water drilling fluid and salt water drilling fluid are configured, 8g of the filtrate reducer prepared in examples 1-4 and comparative example 1 is added into the fresh water drilling fluid, 11g of the filtrate reducer prepared in examples 1-4 and comparative example 1 is added into the salt water drilling fluid, and rapid stirring is performed until it is fully dispersed, and the filtrate reduction performance is evaluated, wherein the hot rolling temperature is 180℃, and the hot rolling time is 16h. The final result is shown in table 2.

[0039] Table 2, filtrate reduction performance test table

[0040]

[0041] From table 2, the filtrate reducer prepared by the embodiment of the application has good temperature resistance and salt resistance, and has good filtrate reduction performance; and in comparative example 1, the problem is that the preparation process of the filtrate reducer is usually alkaline, but in order to make the chitosan better dissolved, we realize it by adding acid, which leads to higher difficulty in subsequent reaction and relatively less reaction products.

[0042] The above is only the preferred specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the embodiment of the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method for preparing an environmentally friendly fluid loss additive, characterized in that, The following steps are included by weight parts: Take 10 parts of chitosan and add it into tetrahydrofuran, and then ultrasonic dispersion is performed, and then a catalyst and an acid binding agent are added and dissolved to obtain a chitosan dispersion liquid; take 2-5 parts of 4-nitrobenzoyl chloride and dissolve it in tetrahydrofuran to obtain a reaction liquid, and then the reaction liquid is added dropwise into the chitosan dispersion liquid under the condition of 0-4 ℃ and continuous stirring, and the reaction is continuously performed for 1-4 h, and then after the reaction is completed, separation and purification are performed to obtain an intermediate; Take 10 parts of the intermediate and add water to dissolve it and adjust the pH of the solution to be alkaline to obtain an intermediate solution, take 8-12 parts of a modified monomer and add it into water and adjust the pH of the solution to be alkaline to obtain a monomer solution, and then the monomer solution is added dropwise into the intermediate solution under the condition of 50-70 ℃, and after the dropwise addition is completed, the reaction is performed for 2-5 h, and then after the reaction is completed, separation and purification are performed to obtain the product; the modified monomer is at least one of 2-acrylamido-2-methylpropanesulfonic acid sodium, monoglyceride methacrylate and polyethylene glycol monomethyl ether acrylate. The chitosan refers to chitosan with a degree of deacetylation greater than 85%.

2. The method of claim 1, wherein, The modified monomer is a mixture of monoglyceride methacrylate and polyethylene glycol monomethyl ether acrylate with a mass ratio of 1:1-2.

3. The method of claim 1, wherein, The pH of the chitosan dispersion liquid and the monomer solution is between 9 and 11.

4. The method of claim 1, wherein, The catalyst is 4-dimethylaminopyridine, and the addition amount is 0.07-0.2 parts; the acid binding agent is one of triethylamine and sodium ethoxide, and the molar ratio of the 4-nitrobenzoyl chloride to the acid binding agent is 1:1-1.

2.

5. The method of claim 1, wherein, The separation and purification step of the intermediate is as follows: take the reaction product, centrifuge to obtain a solid phase, add ether to wash the solid phase several times, and then dry to obtain the product.

6. The method of claim 1, wherein, The separation and purification step of the environmentally friendly fluid loss additive is as follows: take the product, remove low-boiling substances by distillation under reduced pressure, add methanol or ethanol to wash the solid phase several times, and then dry to obtain the product.

7. An environmentally friendly fluid loss additive prepared by the method of any one of claims 1-6.

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