Environment-friendly filtrate reducer and preparation method thereof

Abstract

The invention discloses an environment-friendly filtrate reducer and a preparation method thereof, and relates to the technical field of oilfield chemistry. In the preparation process of the filtrate reducer, firstly, chitosan and 4-nitrobenzoyl chloride are utilized to prepare an intermediate, and then the intermediate is modified by utilizing a modifying monomer. According to the filtrate reducer prepared by the preparation method disclosed by the invention, on the basis of the chitosan with relatively good environmental protection performance, the chitosan is modified by utilizing the 4-nitrobenzoyl chloride and the first monomer, so that the finally prepared filtrate reducer not only has relatively good environmental protection performance, but also is relatively high in dissolving speed and easy to dissolve in an alkaline aqueous solution; meanwhile, the high-temperature-resistant and salt-resistant fluid loss additive has good temperature resistance and salt resistance and good fluid loss reduction performance.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, and in particular to an environmentally friendly fluid loss reducer and a preparation method thereof. Background Art

[0002] During the wellbore construction process, drilling fluid forms a filter cake through filtration, which protects the wellbore and prevents further fluid loss. However, excessive filter cake loss during the formation process not only increases drilling costs, but also easily leads to shale hydration and expansion, which in turn can cause wellbore instability. Furthermore, increased filter loss and thickening of the filter cake reduce the wellbore diameter, creating greater torque on the rotating drill string. This can cause swabbing and pressure fluctuations during tripping, which can easily lead to differential pressure sticking.

[0003] Obviously, filter cake forms as drilling fluid is lost. Any further loss of drilling fluid must pass through the already formed filter cake. Therefore, the primary factor determining fluid loss is the permeability of the filter cake. Creating a high-quality, low-permeability filter cake to prevent further fluid loss is a key consideration in drilling fluid formulation. Therefore, fluid loss control agents are typically added to drilling fluids to control fluid loss during the wall-building process, keeping fluid loss within a reasonable range.

[0004] Chitosan is an excellent natural polysaccharide that is abundant in nature, easily accessible, and has good environmental performance. Original chitosan is insoluble in water, so the chitosan used in drilling fluids is water-soluble chitosan with a high degree of deacetylation. However, conventional water-soluble chitosan is not resistant to salt and alkali, nor to high temperatures, so chitosan used in drilling fluids usually needs to be modified. Existing modification methods usually involve quaternizing chitosan and then grafting acrylamide polymers onto it. On the one hand, this increases the adsorption properties of the modified chitosan, and on the other hand, it gives it a certain shale inhibition effect, while also enhancing the water solubility of the chitosan. However, such modifications, on the one hand, are difficult to improve the heat and salt resistance of chitosan. On the other hand, chitosan is usually used as a substrate for its environmental performance. However, even after the chitosan itself is degraded, the grafted acrylamide polymers are still difficult to degrade, greatly reducing the environmental performance. Summary of the Invention

[0005] In view of the above technical problems, the purpose of the present invention is to provide an environmentally friendly fluid loss reducer and a preparation method thereof to address the defects of the prior art.

[0006] The present invention adopts the following technical solution: a method for preparing an environmentally friendly fluid loss additive, which comprises the following steps, calculated by weight: 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; 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.

[0007] 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.

[0008] 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. In the second step of the present invention, the residual amino groups in the chitosan react with the modified monomer to further modify the chitosan, which not only increases the water solubility and temperature and salt resistance of the chitosan, but also enriches the branched chains of the chitosan, thereby improving its fluid loss reduction performance.

[0009] In one embodiment of the present invention, the chitosan is chitosan having a degree of deacetylation greater than 85%. A higher degree of deacetylation improves water solubility but also increases cost. Therefore, in actual production, chitosan having a degree of deacetylation of 85% to 90% can be used.

[0010] One embodiment of the present invention is that the modified monomer is a mixture of monoglyceride methacrylate and polyethylene glycol monomethyl ether acrylate in a mass ratio of 1:1 to 2. The polyhydroxy structure of monoglyceride methacrylate and the oxygen atoms in polyethylene glycol monomethyl ether acrylate can make the chitosan main chain more easily adsorbed on the well wall, thereby enhancing its fluid loss reduction performance. Its long and short chain comb-like structure also makes the adsorption performance better and the fluid loss reduction effect better. Of course, other combinations, such as the combination of sodium 2-acrylamido-2-methylpropanesulfonate and polyethylene glycol monomethyl ether acrylate, or even a combination of the three, can be applied to the present invention; when the materials are combined in pairs or even in a combination of the three, they can usually be set arbitrarily, such as the mass ratio of sodium 2-acrylamido-2-methylpropanesulfonate and polyethylene glycol monomethyl ether acrylate can be set to 1:9, 2:8 or 9:1, which all have good fluid loss reduction effects.

[0011] One embodiment of the present invention is that during the preparation of the intermediate, the pH of the chitosan dispersion and the monomer solution is between 9 and 11.

[0012] One embodiment of the present invention is that the catalyst is 4-dimethylaminopyridine, and the addition amount is 0.07-0.2 parts. Although the catalyst does not need to be added during the reaction process of the partial reaction of the acyl chloride and the alcoholic hydroxyl group, in the present invention, the 4-nitrobenzoyl chloride has a benzene ring, which has a large steric hindrance and reduces the activity of the acyl chloride. Therefore, adding a 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 1:1-1.2.

[0013] One embodiment of the present invention is that the intermediate is separated and purified by taking the reaction product, centrifuging the solid phase, washing the solid phase several times with ether, and then drying. Theoretically, in this step, the solid phase can also be obtained by filtration or suction filtration. However, in actual operation, chitosan will clog the filter paper, resulting in the slow speed of filtration and suction filtration, which is difficult to apply on a large scale.

[0014] In one embodiment of the present invention, the environmentally friendly fluid loss additive is separated and purified by the following steps: obtaining the product, removing low-boiling substances by vacuum distillation, obtaining the solid phase, washing the solid phase several times with methanol or ethanol, and drying the solid phase. The vacuum distillation referred to herein can be replaced by conventional rotary evaporation, or atmospheric distillation can also be used.

[0015] Another object of the present invention is to disclose an environmentally friendly fluid loss additive prepared by any of the above methods.

[0016] The beneficial effects of the present invention are as follows: the fluid loss reducer prepared by the present invention is based on chitosan with good environmental performance, and is modified by using 4-nitrobenzoyl chloride and a modified monomer. The finally prepared fluid loss reducer not only has good environmental performance, but also has a fast dissolution rate and is easy to dissolve in an alkaline aqueous solution; at the same time, it has good temperature and salt resistance and good fluid loss reduction performance. DETAILED DESCRIPTION

[0017] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is described in detail below in conjunction with the embodiments, but it should not be understood as limiting the scope of implementation of the present invention.

[0018] In the following examples, unless otherwise specified, the methods used are conventional methods in the art.

[0019] In the following examples, unless otherwise specified, the drugs used are conventional commercial products.

[0020] In the following examples, the deacetylation degree of the chitosan 1 used was 85%, and the deacetylation degree of the chitosan 2 used was 95%.

[0021] In the following examples, unless otherwise specified, all parts are by weight.

[0022] Example 1: 100 parts of chitosan were added to tetrahydrofuran and ultrasonically dispersed for 30 minutes. Under continuous stirring, 1.2 parts of 4-dimethylaminopyridine and 25 parts of triethylamine were added and dissolved to obtain a chitosan dispersion. 40 parts of 4-nitrobenzoyl chloride were dissolved in tetrahydrofuran to obtain a reaction solution. The chitosan dispersion and the reaction solution were precooled in an ice bath, and then the reaction solution was added dropwise to the chitosan dispersion under continuous reaction conditions. The reaction was continued for 2 hours. After the reaction was completed, the mixture was centrifuged at 2000 rpm for 10 minutes, and the solid phase was collected. The solid phase was washed several times with ether and dried at 60° C. to obtain an intermediate. 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 them, and add sodium hydroxide to adjust the pH to 9 to obtain a monomer solution, and add the monomer solution dropwise to the intermediate solution at 60°C. After the addition is completed, continue the reaction for 3.5 hours. After the reaction is completed, remove low-boiling substances by distillation under reduced pressure, and then take the solid phase, add methanol to wash the solid phase several times, and dry it at 60°C to obtain a filtrate reducer.

[0023] Example 2 is different from Example 1 in that chitosan 1 is replaced by chitosan 2, and the rest are the same.

[0024] Example 3, compared with Example 1, differs in that, during the preparation of the intermediate, the amount of 4-nitrobenzoyl chloride added is 25 parts, and during the preparation of the fluid loss reducer, monomethacrylate is replaced by sodium 2-acrylamido-2-methylpropanesulfonate, and the rest are the same.

[0025] Example 4 is different from Example 1 in that, during the preparation of the fluid loss agent, 40 parts of monoglycerol methacrylate and 50 parts of polyethylene glycol monomethyl ether acrylate (molecular weight 1000) are replaced by 80 parts of monoglycerol methacrylate, and the rest are the same.

[0026] Comparative Example 1, compared with Example 1, differs in that, in the preparation process of the intermediate, 4-nitrobenzoyl chloride is replaced with benzoyl chloride, and the rest are the same; in the preparation process of the fluid loss reducer, the intermediate has poor water solubility, so 1% acetic acid is added to aid dissolution; however, in the second step reaction, a large amount of precipitate is still generated during the reaction.

[0027] In order to further illustrate the effects of the embodiments of the present invention, a specific method is used to test them below.

[0028] 1. Dissolution rate test The fluid loss additives prepared in Examples 1 to 4 were added to water with a pH of 9 (pH adjusted with sodium carbonate) at a mass ratio of 4 wt %. The mixture was rapidly stirred at 100 r / min and its dissolution time was observed. The time interval was recorded for 30 s. The final results are shown in Table 1, where the blank is the dissolution time of 4 wt % chitosan in an aqueous solution with an acetic acid content of 3 wt %.

[0029] Table 1 Dissolution rate test table

[0030] As can be seen from Table 1, the fluid loss additive prepared in the embodiment of the present invention can be quickly dissolved in an alkaline aqueous solution; similar to the conventional phenomenon, the blank has a slow dissolution rate and a small amount of insoluble matter after dissolution.

[0031] 2. Fluid loss reduction performance Freshwater drilling fluid and brine drilling fluid were prepared according to the method described in "Q / SH 0047-2007 General Technical Requirements for Salt-Resistant and High-Temperature-Resistant Fluid Loss Reducers for Drilling Fluids." 8g of the fluid loss reducers prepared in Examples 1-4 and Comparative Example 1 were added to the freshwater drilling fluid, while 11g of the fluid loss reducers prepared in Examples 1-4 and Comparative Example 1 were added to the brine drilling fluid. The fluid loss reduction performance was evaluated using a hot rolling temperature of 180°C and a hot rolling time of 16 hours. The results are shown in Table 2.

[0032] Table 2 Fluid loss reduction performance test table

[0033] As can be seen from Table 2, the fluid loss additive prepared in the embodiment of the present invention has good temperature and salt resistance, and at the same time, has good fluid loss reduction performance; however, in Comparative Example 1, the problem is that, during the preparation of the fluid loss additive, alkaline conditions are usually used, but in order to better dissolve chitosan, acid is added, resulting in a higher difficulty in the subsequent reaction and a relatively small amount of reaction product.

[0034] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing an environmentally friendly fluid loss additive, characterized in that: Calculated by weight, comprising the following steps: 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; 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.

2. The method according to claim 1, characterized in that The chitosan refers to chitosan with a deacetylation degree greater than 85%.

3. The method according to claim 1, characterized in that The modified monomer is a mixture of glycerol monomethacrylate and polyethylene glycol monomethyl ether acrylate in a mass ratio of 1:1-2.

4. The method according to claim 1, wherein During the preparation of the intermediate, the pH of the chitosan dispersion and the monomer solution is between 9 and 11.

5. The method according to 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.

6. The method according to claim 1, wherein The separation and purification steps of the intermediate are as follows: taking the reaction product, centrifuging to obtain a solid phase, adding ether to wash the solid phase several times, and then drying to obtain the intermediate.

7. The method according to claim 1, characterized in that The separation and purification steps of the environmentally friendly fluid loss reducer are: taking the product, removing low-boiling substances by vacuum distillation, adding methanol or ethanol to wash the solid phase several times, and then drying to obtain the product.

8. An environmentally friendly fluid loss additive prepared by the method according to any one of claims 1 to 7.

Images