A kind of fluid loss reducer based on alkanone polymer and preparation method thereof

Abstract

The invention discloses a fluid loss reducer based on an alkane polymer and a preparation method thereof, and relates to the technical field of oilfield chemistry. In parts by weight, the preparation method comprises the following steps: 2 to 5 parts of trimethyl trivinyl cyclotrisiloxane are dissolved in a solvent to form a solution a, 10 to 20 parts of N, N-dimethyl acrylamide, 3 to 8 parts of N-vinyl pyrrolidone, 1 to 5 parts of long-chain acrylate and 1 to 3 parts of acrylonitrile are dissolved in a solvent to form a solution b, an oil-soluble initiator is dissolved in a solvent to form a solution c, the temperature is raised to the initiation temperature, and solution b and solution c are added dropwise to solution a for polymerization, and after the polymerization is completed, the solution is separated and purified to obtain the fluid loss reducer. The fluid loss reducer prepared by the present invention has good temperature resistance and salt resistance and good fluid loss reduction performance; and the fluid loss reducer of the present invention does not contain a sulfonic group and has good environmental performance.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, and in particular to an alkane polymer-based fluid loss reducer 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 drilling fluid loss is to add a fluid loss reducer to the drilling fluid. The fluid loss reducer can greatly reduce the permeability of the filter cake, making the filter cake denser, thereby reducing the drilling fluid loss 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] 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

[0005] In view of the above technical problems, the purpose of the present invention is to provide a fluid loss reducer based on an alkane polymer and a preparation method thereof in view of the defects of the prior art.

[0006] The present invention adopts the following technical solutions:

[0007] A preparation method of a fluid loss reducer based on an alkane polymer comprises the following steps, measured in parts by weight: 2 to 5 parts of trimethyl trivinyl cyclotrisiloxane are dissolved in a solvent to form a solution a, 10 to 20 parts of N, N-dimethyl acrylamide, 3 to 8 parts of N-vinyl pyrrolidone, 1 to 5 parts of long-chain acrylate and 1 to 3 parts of acrylonitrile are dissolved in a solvent to form a solution b, an oil-soluble initiator is dissolved in a solvent to form a solution c, the temperature is raised to an initiation temperature, and solution b and solution c are dripped into solution a for polymerization, and after the polymerization is completed, the solution is separated and purified 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 12.

[0008] Specifically, in the present invention, trimethyl trivinyl cyclotrisiloxane is used as the core, N, N-dimethyl acrylamide, N-vinyl pyrrolidone, long-chain acrylate and acrylonitrile are used as synthetic monomers, and finally a three-arm alkane ketone polymer is formed, which has a certain water solubility and good fluid loss reduction performance and heat resistance and salt resistance. At the same time, after a large number of experiments, the inventor found that for the fluid loss reducer, too many branches have a negative impact on its fluid loss reduction performance. For example, for the similar tetramethyl tetravinyl cyclotetrasiloxane, the fluid loss reducer obtained with it as the core has good heat resistance and salt resistance, but its fluid loss reduction performance is greatly reduced; at the same time, for the chain that does not contain siloxane, such as tetramethyl divinyl disiloxane, its temperature resistance is relatively low.

[0009] In one embodiment of the present invention, the solvent is one of dimethyl sulfoxide and dimethylformamide, which are common solvents in the art and can dissolve the above-mentioned monomers.

[0010] One embodiment of the present invention is that the oil-soluble initiator is an azo initiator, the addition amount is 0.3-1wt% of the mass of all monomers, the reaction time is 1-3h, the initiator is a commonly used oil-soluble initiator, and the addition amount and reaction time are the common addition amount and common reaction time of azo oil-soluble initiators. As for the reaction temperature, it can be determined according to the specific azo initiator, for example, for azobisisobutyronitrile, the temperature is 50-80°C.

[0011] One embodiment of the present invention is that in the long-chain acrylate, the carbon chain length of R2 is 8 to 10. This type of long-chain acrylate has better performance in the final fluid loss agent.

[0012] One embodiment of the present invention is that, in the process of dripping solution b and solution c into solution a, the dripping time of solution c is not less than the dripping time of solution b. Since solution c is an initiator solution, if its dripping speed is too fast, the amount of initiator in the reaction liquid will increase, and the reaction rate of the monomers in the reaction liquid will be accelerated; and since some monomers are still in solution b and have not entered the reaction liquid, the final reaction product and the target reaction product are too different, and the performance of the fluid loss reducer is reduced.

[0013] One embodiment of the present invention is that the separation and purification step includes the following sub-steps: adding at least 3 times of water and at least 2 times of chloroform based on the total volume of the reaction solution, shaking and letting it stand, removing the chloroform layer, and then rotary evaporating to obtain.

[0014] A fluid loss reducer based on an alkane polymer 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.

[0015] The beneficial effects of the present invention are as follows: the fluid loss reducer prepared by the present invention has good temperature resistance and salt resistance and good fluid loss reduction performance; and the fluid loss reducer of the present invention does not contain sulfonic groups and has good environmental performance. In the present invention, after each solution is prepared, the product is prepared by a one-pot method, the preparation method is relatively simple, and the time used is relatively short. DETAILED DESCRIPTION

[0016] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical scheme of the present invention is described in detail below in conjunction with embodiments, but it should not be construed as limiting the applicable scope of the present invention.

[0017] In the following examples, unless otherwise specified, the methods used are conventional methods in the art.

[0018] In the following examples, unless otherwise specified, the drugs used are conventional commercial products.

[0019] Example 1. In this example, the monomers for preparing the fluid loss reducer include 4 g of trimethyltrivinylcyclotrisiloxane, 15 g of N,N-dimethylacrylamide, 6 g of N-vinylpyrrolidone, 3 g of long-chain acrylate and 2 g of acrylonitrile, and 0.2 g of azobisisobutyronitrile, wherein the long-chain acrylate is n-octyl acrylate.

[0020] The preparation method of the filtrate reducer is as follows: trimethyl trivinyl cyclotrisiloxane is added to dimethyl sulfoxide to prepare solution a, N, N-dimethyl acrylamide, N-vinyl pyrrolidone, long-chain acrylate and acrylonitrile are added to dimethyl sulfoxide to prepare solution b, azobisisobutyronitrile is added to dimethyl sulfoxide to prepare solution c, solution a is heated to 60°C, solution b and solution c are added dropwise to solution a under continuous stirring, the dropping speed of solution c is controlled so that the dropping time and the dropping time of solution b are both 20min, and the temperature is controlled not to exceed 80°C during the reaction process. After the dropping is completed, the reaction is continued for 2h. After the reaction is completed, 2 times of water and 3 times of chloroform are added to the reaction solution, the mixture is shaken and allowed to stand for a period of time, the chloroform layer is removed after stratification, and a mixed solution of water and dimethyl sulfoxide is taken and rotary evaporated to obtain the obtained solution.

[0021] Example 2. In this example, the monomers for preparing the fluid loss reducer include 2.5 g of trimethyltrivinylcyclotrisiloxane, 18 g of N,N-dimethylacrylamide, 6 g of N-vinylpyrrolidone, 3 g of long-chain acrylate and 2 g of acrylonitrile, and 0.2 g of azobisisobutyronitrile, wherein the long-chain acrylate is decyl methacrylate.

[0022] The preparation method of the fluid loss reducer is as follows: trimethyl trivinyl cyclotrisiloxane is added to dimethylformamide to prepare solution a, N, N-dimethylacrylamide, N-vinyl pyrrolidone, long-chain acrylate and acrylonitrile are added to dimethyl sulfoxide to prepare solution b, azobisisobutyronitrile is added to dimethyl sulfoxide to prepare solution c, solution a is heated to 60°C, solution b and solution c are added dropwise to solution a under continuous stirring, the dropping speed of solution c is controlled so that the dropping time and the dropping time of solution b are both 20min, and the temperature is controlled not to exceed 80°C during the reaction process. After the dropping is completed, the reaction is continued for 2h. After the reaction is completed, 2 times of water and 3 times of chloroform are added to the reaction solution, the mixture is shaken and allowed to stand for a period of time, the chloroform layer is removed after stratification, and a mixed solution of water and dimethyl sulfoxide is taken and rotary evaporated to obtain the obtained solution.

[0023] Example 3 is different from Example 1 in that the long-chain acrylate is replaced by lauryl acrylate, and the rest are the same.

[0024] Example 4 is different from Example 1 in that the dropping time of solution c is 10 min, and the rest are the same.

[0025] Comparative Example 1 is compared with Example 1, except that trimethyltrivinylcyclotrisiloxane is replaced by tetramethyltetravinylcyclotetrasiloxane, and the rest are the same.

[0026] Comparative Example 2 is compared with Example 1, except that trimethyltrivinylcyclotrisiloxane is replaced by tetramethyldivinyldisiloxane, and the rest are the same.

[0027] Comparative Example 3 is compared with Example 1, except that no long-chain acrylate is added, and the rest is the same.

[0028] Comparative Example 4 is compared with Example 1, except that acrylonitrile is not added, and the rest are the same.

[0029] In order to further illustrate the effect of the embodiment of the present invention, a specific method is used to test it below.

[0030] 1. Fluid loss reduction performance

[0031] 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.

[0032] 20g of the fluid loss reducers prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were added to the aforementioned base slurry, respectively. 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 hot rolling was required before the HTHP fluid loss test, the hot rolling temperature was 240°C, and the hot rolling time was 16h. The final results are shown in Table 1.

[0033] Table 1 Filtration reduction performance test results

[0034]

[0035] 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.

[0036] 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 an alkane polymer, characterized in that: The method comprises the following steps, in parts by weight: dissolving 2 to 5 parts of trimethyl trivinyl cyclotrisiloxane in a solvent to prepare solution a, dissolving 10 to 20 parts of N,N-dimethyl acrylamide, 3 to 8 parts of N-vinyl pyrrolidone, 1 to 5 parts of long-chain acrylate and 1 to 3 parts of acrylonitrile in a solvent to prepare solution b, dissolving an oil-soluble initiator in a solvent to prepare solution c, heating to an initiation temperature, and dropping solution b and solution c into solution a for polymerization, and separating and purifying the solution after the polymerization is completed to obtain the long-chain acrylate; 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 4 to 12.

2. The method according to claim 1, characterized in that The solvent is one of dimethyl sulfoxide and dimethylformamide.

3. The method according to claim 1, characterized in that The oil-soluble initiator is an azo initiator, the amount added is 0.3-1wt% of the mass of all monomers, and the reaction time is 1-3h.

4. The method according to claim 1, characterized in that In the long-chain acrylate, the carbon chain length of R2 is 8 to 10.

5. The method according to claim 1, characterized in that In the process of adding solution b and solution c dropwise to solution a, the dropping time of solution c is not less than the dropping time of solution b.

6. The method according to claim 1, characterized in that The separation and purification step comprises the following sub-steps: based on the total volume of the reaction solution, adding at least 2 times of water and at least 3 times of chloroform, shaking and standing, removing the chloroform layer, and then rotary evaporating to obtain the product.

7. A fluid loss reducer based on an alkane polymer, prepared by the method according to any one of claims 1 to 6.

Images