Filtrate reducer based on modified humic acid and preparation method thereof

Abstract

The invention discloses a fluid loss reducer based on modified humic acid and a preparation method thereof, and relates to the technical field of oilfield chemistry. The preparation method of the fluid loss reducer comprises the following steps: taking modified humic acid, N,N-dimethylacrylamide, N-vinyl imidazole, long-chain acrylate and hydroxyethyl acrylate and dissolving them in a solvent, then adding an initiator and reacting to obtain the fluid loss reducer; wherein, during the preparation, the modified humic acid is first activated by low-concentration potassium permanganate, and then reacted with methylchlorosilane. The fluid loss reducer prepared by the invention has good heat and salt resistance, and good fluid loss reduction performance. The preparation method of the invention is relatively simple, each raw material is simple and easy to obtain, the cost is low, and it is easy to promote.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, and in particular to a fluid loss reducer based on modified humic acid and a preparation method thereof. Background Art

[0002] Drilling fluid filtration and filter cake formation During the drilling process, drilling fluid filtration is inevitable, and filter cakes can be formed to protect the wellbore wall through filtration. However, excessive drilling fluid filtration can easily cause shale expansion and collapse, resulting in instability of the wellbore wall. In addition, as the filtration loss increases, the filter cake thickens, which reduces the wellbore diameter and causes a large torque to the rotating drill bit, causing pumping and pressure fluctuations during drilling, which can easily cause differential pressure sticking. Therefore, proper control of filtration loss is one of the important properties of drilling fluid. Obviously, the filtration loss of drilling fluid is closely related to the permeability of the formation. However, when the drilling fluid is lost, filter cake is formed. When the drilling fluid is lost again, it must pass through the already formed filter cake. Therefore, the main factor that determines the size of the filtration loss 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 issues to be considered in the preparation of drilling fluid. At present, an important means to reduce the filtration loss of drilling fluid is to add filtration reducers to the drilling fluid. The filtration reducers can reduce the permeability of the filter cake, making the filter cake denser, thereby reducing the filtration loss of drilling fluid as much as possible.

[0003] The development of deep wells and ultra-deep wells has become a research hotspot. Deep wells and ultra-deep wells have the characteristics of high temperature and high mineralization. Therefore, for these new reservoirs, it is currently hoped to increase the temperature and salt resistance of the fluid loss reducer so that it can be applied to high-temperature and high-salinity reservoirs.

[0004] Humic acid is a common component of fluid loss reducers. It has a relatively rich active functional group and can undergo a variety of reactions. Humic acid has a large number of rigid benzene rings, so it has a certain strength. However, in the prior art, humic acid is usually directly reacted with other monomers to prepare fluid loss reducers, resulting in relatively poor fluid loss reduction effects.

[0005] In the prior art, the method for improving the temperature and salt resistance of the fluid loss reducer is usually to add a temperature and salt resistant monomer containing a sulfonic acid group to the fluid loss reducer. However, there is sulfur in the sulfonic acid group. Due to environmental pressure, there is an urgent need for a fluid loss reducer that does not contain sulfur and has good temperature and salt resistance. Summary of the invention

[0006] In view of the above technical problems, the purpose of the present invention is to provide a fluid loss reducer based on modified humic acid and a preparation method thereof in view of the defects of the prior art.

[0007] The present invention adopts the following technical solutions:

[0008] A preparation method of a fluid loss reducer based on modified humic acid, which comprises the following steps, in parts by weight: taking 10 parts of modified humic acid, 10-20 parts of N,N-dimethylacrylamide, 2-5 parts of N-vinyl imidazole, 1-5 parts of long-chain acrylate and 1-3 parts of hydroxyethyl acrylate and dissolving them in a solvent, then adding an initiator and reacting to obtain the fluid loss reducer; the structural formula of the long-chain acrylate is: , wherein R1 is one of -H or -CH3, and R2 is a straight-chain alkyl group with a carbon chain length of 6 to 14;

[0009] The preparation method of the modified humic acid comprises the following steps: dispersing lignite in water, adding alkali to react, and after the reaction is completed, removing insoluble matter to obtain a humic acid solution; adding potassium permanganate to the humic acid solution and adjusting its concentration to 0.8-2%, reacting at 10-100° C. for 10-60 minutes, adding methylchlorosilane after the reaction is completed, reacting at 10-40° C. for 1-3 hours, and removing the liquid phase after the reaction is completed; the amount of potassium permanganate added is 5-10% of the total solid mass in the humic acid solution, and the amount of methylchlorosilane added is 15-25% of the total solid mass in the humic acid solution.

[0010] In the present invention, in the preparation process of modified humic acid, humic acid is first prepared from lignite, and then the humic acid is activated by potassium permanganate at a low concentration and a small amount. The activated humic acid has a higher activity and is easier to react with the monomer. The activated humic acid is modified by methylchlorosilane. The viscosity of the humic acid obtained after the modification decreases, and it is easier to adsorb on the drilling fluid filter cake, which is manifested as being able to improve the filtration loss reduction performance of the filtrate reducer. The inventors found in the research and development process that in the present invention, potassium permanganate is preferred, considering that it has a relatively moderate oxidation performance under alkaline conditions; and the amount of potassium permanganate added should not be too large, and the concentration should not be too large: too large an amount and too large a concentration will cause a significant degradation of the humic acid. For other oxidants, such as hydrogen peroxide, they mainly show reducing properties under alkaline conditions and are difficult to be applied to the present invention; for sodium hypochlorite, chlorine and ozone, their oxidizing properties are too strong and they can easily oxidize humic acid into small molecular components, which are difficult to control. Moreover, ozone and chlorine are gases and their addition amounts are difficult to control.

[0011] At the same time, in the preparation process of modified humic acid, the reason why the total mass of solids in the humic acid solution is used as the benchmark to limit the remaining materials is that the humic acid content in different lignites is quite different: Generally speaking, the humic acid content in lignite varies from 10 to 80 wt% depending on its source. Therefore, if the weight of lignite is directly used as the benchmark, the performance of the products prepared in this way will be quite different, and many products are difficult to be applied to the present invention.

[0012] For the remaining monomers of the fluid loss agent, N,N-dimethylacrylamide is the basic component, and its salt resistance is better than that of acrylamide; N-vinyl imidazole is a rigid monomer, which further enhances the temperature resistance of the fluid loss agent; long-chain acrylate can increase the hydrophobicity of the fluid loss agent, thereby improving the fluid loss reduction effect; hydroxyethyl acrylate has a certain adsorption on the filter cake, which can improve the fluid loss reduction effect. At the same time, these four monomers form a "comb-shaped" structure after polymerization, and their performance is better than that of conventional linear monomers.

[0013] One embodiment of the present invention is that the solvent is a mixture of water and ethanol in a volume ratio of 1:0.5 to 1, or the solvent is a mixture of water and methanol in a volume ratio of 1:0.5 to 1. Considering the solubility of each material, the solvent is involved, and the solvent can dissolve all monomers well.

[0014] One embodiment of the present invention is that in the long-chain acrylate, R2 is a straight-chain alkyl group with a carbon chain length of 8 to 12, and the acrylate with this chain length has a better effect.

[0015] One embodiment of the present invention is that the initiator is a persulfate initiator, and the reaction temperature after adding the initiator is 40-70°C and the reaction time is 1-4h, which is a conventional water-soluble initiator in the art, and the initiation conditions are also conventional initiation conditions in the art. Of course, those skilled in the art can also choose other water-soluble initiators, such as redox initiators, etc. The initiation temperature of redox initiators is lower, but the reaction speed is relatively fast, and there may be trace amounts of permanganate and manganate (reduction products of permanganate ions under alkaline conditions) remaining in the modified humic acid. These ions have certain oxidizing properties, which will accelerate the initiation speed of redox initiators.

[0016] One embodiment of the present invention is that during the preparation of the modified humic acid, the pH of the humic acid solution is 8 to 10. This is because the alkali in the humic acid solution cannot be too much: if there is too much residual alkali, it will affect the subsequent reaction. If too much alkali is added under the initial conditions, resulting in the pH of the humic acid solution being greater than 10, the humic acid solution after the reaction can be adjusted by adding acid.

[0017] One embodiment of the present invention is that in the preparation process of the modified humic acid, the reaction temperature after adding potassium permanganate is 30-50°C and the reaction time is 35-45min. The activated humic acid prepared under this condition has relatively good performance.

[0018] One embodiment of the present invention is that in the preparation process of the fluid loss reducer, the amount of modified humic acid added is 10 parts, the amount of N,N-dimethylacrylamide added is 15-18 parts, the amount of N-vinyl imidazole added is 3-4 parts, the amount of long-chain acrylate added is 2-3 parts, and the amount of hydroxyethyl acrylate added is 1.5-2.5 parts. The fluid loss reducer prepared by using this formula has better temperature resistance and salt resistance and better fluid loss reduction performance.

[0019] A fluid loss reducer based on modified humic acid is prepared by any of the above methods. The fluid loss reducer has good temperature resistance and salt resistance and good fluid loss reduction performance.

[0020] The beneficial effects of the present invention are as follows: the fluid loss reducer prepared by the present invention has good temperature and salt resistance, and has good fluid loss reduction performance, and can be applied to a high temperature of 220°C; at the same time, the fluid loss reducer of the present invention does not contain a sulfonic acid group and has good environmental protection performance. The preparation method of the present invention is relatively simple, each raw material is simple and easy to obtain, the cost is low, and it is easy to promote. DETAILED DESCRIPTION

[0021] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solutions of the present invention are described in detail in the following embodiments, but they should not be construed as limiting the applicable scope of the present invention.

[0022] In the following examples, unless otherwise specified, the methods used are conventional methods in the art.

[0023] In the following examples, unless otherwise specified, the drugs used are conventional commercial products.

[0024] In the following examples, lignite 1 and lignite 2 were purchased from different manufacturers and contained different amounts of humic acid.

[0025] Example 1, preparation of modified humic acid: lignite was dispersed in water, and then a large amount of sodium hydroxide was added to make the pH of the aqueous solution greater than 10 at all times, and the mixture was stirred for reaction for 3 hours. After the reaction was completed, the insoluble matter was filtered out, and the pH of the solution was adjusted to 9.5 with hydrochloric acid to obtain a humic acid solution. The solid content of the humic acid solution was measured to be 48%; 1000 ml of the humic acid solution was taken, and then 38.4 g of potassium permanganate was taken and 1000 ml of water was added to dissolve it, and then the potassium permanganate solution and the humic acid solution were evenly mixed, and the mixture was reacted at 40° C. with continuous stirring for 40 minutes. After the reaction was completed, 96 g of methylchlorosilane was added, and the mixture was reacted at 30° C. for 1.5 hours. After the reaction was completed, the liquid phase was removed by rotary evaporation to obtain modified humic acid.

[0026] Preparation of filtrate reducer: 10g of modified humic acid, 16g of N,N-dimethylacrylamide, 4g of N-vinyl imidazole, 2.5g of lauryl acrylate and 2g of hydroxyethyl acrylate are added to a solvent, wherein the solvent is prepared from water and ethanol in a volume ratio of 1:0.7; after the above monomers are dissolved, potassium persulfate is added at 60°C and reacted for 3h. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the filtrate reducer.

[0027] Example 2, preparation of modified humic acid: lignite was dispersed in water, and then a large amount of sodium hydroxide was added to make the pH of the aqueous solution greater than 10 at all times, and the mixture was stirred for reaction for 2 hours. After the reaction was completed, the insoluble matter was filtered out, and the pH of the solution was adjusted to 9 with hydrochloric acid to obtain a humic acid solution. The solid content of the humic acid solution was measured to be 33%; 1000 ml of the humic acid solution was taken, and then 19.8 g of potassium permanganate was taken and 250 ml of water was added to dissolve it, and then the potassium permanganate solution and the humic acid solution were evenly mixed, and the mixture was reacted at 35° C. with continuous stirring for 45 minutes. After the reaction was completed, 72 g of methylchlorosilane was added, and the mixture was reacted at 20° C. for 2.5 hours. After the reaction was completed, the liquid phase was removed by rotary evaporation to obtain the modified humic acid.

[0028] Preparation of filtrate reducer: 10g of modified humic acid, 16g of N,N-dimethylacrylamide, 4g of N-vinyl imidazole, 2.5g of lauryl acrylate and 2g of hydroxyethyl acrylate are added to a solvent, wherein the solvent is prepared from water and ethanol in a volume ratio of 1:0.7; after the above monomers are dissolved, potassium persulfate is added at 60°C and reacted for 3h. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the filtrate reducer.

[0029] Example 3, preparation of modified humic acid: same as Example 1.

[0030] Preparation of filtrate reducer: 10g of modified humic acid, 12g of N,N-dimethylacrylamide, 2.5g of N-vinyl imidazole, 2.5g of n-octyl acrylate and 2g of hydroxyethyl acrylate are added to a solvent, wherein the solvent is prepared from water and methanol in a volume ratio of 1:0.5; after the above monomers are dissolved, potassium persulfate is added at 60°C and reacted for 3h. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the filtrate reducer.

[0031] Example 4, preparation of modified humic acid: same as Example 1.

[0032] Preparation of filtrate reducer: 10g of modified humic acid, 18g of N,N-dimethylacrylamide, 4.5g of N-vinyl imidazole, 2.5g of lauryl acrylate and 4g of hydroxyethyl acrylate are added to a solvent, wherein the solvent is prepared from water and methanol in a volume ratio of 1:0.5; after the above monomers are dissolved, potassium persulfate is added at 60°C and reacted for 3h. After the reaction is completed, the solvent is removed by rotary evaporation to obtain the filtrate reducer.

[0033] Comparative Example 1 is different from Example 1 in that, during the preparation of the modified humic acid, the amount of potassium permanganate added is 55 g, and no water is added to dissolve and dilute the potassium permanganate, and the rest are the same.

[0034] Comparative Example 2 is different from Example 1 in that potassium permanganate is not added during the preparation of the modified humic acid, and the rest are the same.

[0035] Comparative Example 3 is different from Example 1 in that no methylchlorosilane is added during the preparation of the modified humic acid, and the rest are the same.

[0036] Comparative Example 4 is compared with Example 1, except that, in the preparation process of the fluid loss reducer, lauryl acrylate is replaced by butyl acrylate, and the rest are the same.

[0037] Comparative Example 5 is different from Example 1 in that after the humic acid solution is obtained, the humic acid solution is not modified, and the rest are the same.

[0038] In order to further illustrate the effect of the embodiment of the present invention, a specific method is used to test it below.

[0039] 1. Fluid loss reduction performance

[0040] Preparation of drilling fluid base slurry: Take 1000ml water, add 50g sodium bentonite, 0.2g hydrolyzed polyacrylamide, and 2g sodium carbonate in sequence, stir at high speed during the addition process to make them evenly mixed, and then get base slurry 1. Take another 1000ml water, add 50g sodium bentonite, 0.2g hydrolyzed polyacrylamide, 10g sodium carbonate, 200g sodium chloride, and 5g calcium chloride in sequence, stir at high speed during the addition process to make them evenly mixed, and then get base slurry 2.

[0041] 20g of the fluid loss reducers prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were added to the aforementioned base slurry, and after hot rolling, the fluid loss reduction performance was evaluated according to the method shown in GB / T16783.1-2014 "Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids", wherein the hot rolling temperature was 230°C and the hot rolling time was 16h. The final results are shown in Table 1.

[0042] Table 1 Filtration reduction performance test results

[0043]

[0044] It can be seen from Table 1 that the fluid loss reducer 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.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a fluid loss reducer based on modified humic acid, characterized in that: The method comprises the following steps, in parts by weight: taking 10 parts of modified humic acid, 10-20 parts of N,N-dimethylacrylamide, 2-5 parts of N-vinyl imidazole, 1-5 parts of long-chain acrylate and 1-3 parts of hydroxyethyl acrylate and dissolving them in a solvent, then adding an initiator and reacting to obtain the product; the structural formula of the long-chain acrylate is: , wherein R1 is one of -H or -CH3, and R2 is a straight-chain alkyl group with a carbon chain length of 6 to 14; The preparation method of the modified humic acid comprises the following steps: dispersing lignite in water, adding alkali to react, and after the reaction is completed, removing insoluble matter to obtain a humic acid solution; adding potassium permanganate to the humic acid solution and adjusting its concentration to 0.8-2%, reacting at 10-100° C. for 10-60 minutes, adding methylchlorosilane after the reaction is completed, reacting at 10-40° C. for 1-3 hours, and removing the liquid phase after the reaction is completed; the amount of potassium permanganate added is 5-10% of the total solid mass in the humic acid solution, and the amount of methylchlorosilane added is 15-25% of the total solid mass in the humic acid solution.

2. The method according to claim 1, characterized in that The solvent is a mixture of water and ethanol in a volume ratio of 1:0.5-1, or the solvent is a mixture of water and methanol in a volume ratio of 1:0.5-1.

3. The method according to claim 1, characterized in that In the long-chain acrylate, R2 is a straight-chain alkyl group with a carbon chain length of 8 to 12.

4. The method according to claim 1, characterized in that: The initiator is a persulfate initiator, and the reaction temperature after adding the initiator is 40-70° C. and the reaction time is 1-4 hours.

5. The method according to claim 1, characterized in that During the preparation of the modified humic acid, the pH of the humic acid solution is 8-10.

6. The method according to claim 1, characterized in that In the preparation process of the modified humic acid, the reaction temperature after adding potassium permanganate is 30-50° C., and the reaction time is 35-45 min.

7. The method according to claim 1, characterized in that During the preparation of the fluid loss reducer, the amount of modified humic acid added is 10 parts, the amount of N,N-dimethylacrylamide added is 15-18 parts, the amount of N-vinyl imidazole added is 3-4 parts, the amount of long-chain acrylate added is 2-3 parts, and the amount of hydroxyethyl acrylate added is 1.5-2.5 parts.

8. A fluid loss reducer based on modified humic acid, prepared by the method according to any one of claims 1 to 7.

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