Method for tackifying viscosity of polymer displacement fluid

Abstract

The invention discloses a method for tackifying the viscosity of a polymer displacement fluid, and the method comprises the following steps: S1, stirring a mixture containing thiourea, polyethylene glycol and water I to obtain a tackifying solution; and S2, adding the tackifying solution into the polymer displacement fluid, and stirring II to obtain the tackified polymer displacement fluid. The tackifying method provided by the invention is convenient and simple, adopts traditional dissolution compounding, is low in raw material price and easy to operate, is stable in tackifier product, and can be used for preparing the polymer tackifying liquid with specified viscosity by adjusting the addition amount according to actual requirements.

Description

Technical Field

[0001] The present application relates to a method for increasing the viscosity of a polymer displacement fluid, and belongs to the technical field of petroleum extraction. Background Art

[0003] Polymers are the most common oil displacement agents in oil fields. However, as oil field exploration and development develops towards unconventional reservoir conditions such as high temperature, high salinity, and low permeability, conventional polymers cannot meet the needs of oil extraction. Therefore, researching and developing new temperature-resistant and salt-resistant polymers is an important task to promote the development of my country's petroleum industry technology.

[0004] Existing polyacrylamide thickening often adds complex crosslinking agents or thickeners, among which, the thickener needs to be synthesized on site, the preparation process is complicated, the material cost is high, and there are many factors affecting the polymerization of monomers; it requires a certain reaction time or high cost, and the process is not simple enough, so that the polymer oil displacement agent often enters the reservoir in a single form. Patent CN117510703A is a polymer thickener and its preparation method and application. The polymer thickener is prepared by a complex polymerization reaction. The polymer itself has a certain viscosity. Through a series of hydrophobic association effects, the displacement fluid added to the ground is thickened, and the polymer thickener is unstable. Summary of the invention

[0005] In view of the problem of unstable viscosity of polymer thickeners in the above-mentioned prior art, the present application provides a method for developing and optimizing polymer oil displacement agents based on the polymer itself, and synthesizing hydrophobically associating polyacrylamide. The hydrophobically associating polyacrylamide provided in the present application is an additive to the polymer solution, and different amounts can be added according to different viscosity requirements to adjust the viscosity at any time, wherein the base polymer can be conventional polyacrylamide.

[0006] According to one aspect of the present application, a method for increasing the viscosity of a polymer displacement fluid is provided, the method comprising the following steps:

[0007] S1: stirring a mixture containing thiourea, polyethylene glycol and water for 1 to obtain a viscosity-enhancing solution;

[0008] S2: adding the thickening solution to the polymer displacement fluid and stirring II to obtain a thickened polymer displacement fluid;

[0009] In the step S2, the amount of the viscosity increasing solution added is 0.5% to 4% of the mass of the polymer displacement fluid.

[0010] Optionally, in step S2, the amount of the thickening solution added is any value independently selected from 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% by mass of the polymer displacement fluid, or a range between any two of the above.

[0011] Optionally, in step S1, the mass ratio of thiourea to water is 1:4 to 1:8.

[0012] Optionally, in step S1, the amount of polyethylene glycol added is 1-3% of the mass of the viscosity-increasing solution.

[0013] Optionally, in step S1, the molecular weight of the polyethylene glycol is 200-3000.

[0014] Optionally, in step S2, the polymer displacement fluid is a polyacrylamide solution.

[0015] Optionally, in step S2, the viscosity of the polymer displacement fluid is 800-2000 cp.

[0016] Optionally, in step S2, the viscosity of the polymer displacement fluid after viscosity increase is 5000 to 20000 cp.

[0017] Optionally, in step S1, the rotation speed of the stirring I is 20 to 200 rpm, and the time of the stirring I is 10 to 30 min.

[0018] Optionally, in step S2, the rotation speed of the stirring I is 50 to 500 rpm, and the time of the stirring I is 3 to 15 min.

[0019] As an optional implementation method, the present application is implemented through the following technical solutions:

[0020] Preparation of tackifier:

[0021] Step A: dissolving thiourea powder and deionized water in a mass ratio of 1:4 to 1:8;

[0022] Step B: adding 1% to 3% polyethylene glycol powder with a molecular weight of 200 to 3000;

[0023] Step C: Add the prepared viscosity-enhancing solution to the polyacrylamide solution with a viscosity of 800-2000 cp at a ratio of 0.5-4%, and stir for 10 minutes.

[0024] In the present application, thiourea reacts with independent unreacted double bonds in the reactive side chains, thereby forming a cross-linked structure between multiple polyacrylamide chains, thereby increasing the viscosity and mechanical strength of the polyacrylamide. The viscosity of the polymer displacement fluid can be accurately and stably adjusted by adding thiourea.

[0025] The beneficial effects of this application include:

[0026] 1) The method for increasing the viscosity of the polymer displacement fluid provided in the present application is compared with the prior art which requires the addition of monomers, initiators, etc. for heating reaction, has complex preparation, and has many influencing factors. The preparation is convenient and simple, is a traditional dissolution compound, has low raw material prices, is easy to operate, and the thickening solution product is stable. The addition amount can be adjusted according to actual needs to prepare a polymer thickening fluid with a specified viscosity.

[0027] 2) The viscosity-enhancing solution provided in the present application is an additive for the polymer solution. Different amounts are added according to different viscosity requirements to adjust the viscosity at any time. The base polymer can be conventional polyacrylamide. DETAILED DESCRIPTION

[0028] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0029] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0030] This application uses a rotational rheometer for characterization and performance testing. The equipment model is German HAAKE MARS 40. The viscosity test conditions are:

[0031] Test element definition: ID2: set temperature; CS; τ0.000mPa; t<10.00min; T25.00℃±1.00℃; ID3: Rot rotation time scan; CR; γ7.340 1 / s; t 15.00min; #30; T prev℃.

[0032] Example 1 Preparation of tackifier

[0033] Step A: Weigh 20 g of thiourea powder and 78 g of deionized water and dissolve them in a mass ratio of 1:5;

[0034] Step B: Add 2 g (2%) polyethylene glycol powder with a molecular weight of 600 to step A, stir at 100 rpm for 15 min to obtain a viscosity-enhanced solution;

[0035] Step C: Add 2 g of polyacrylamide solution with a viscosity of 600 to the prepared thickening solution at a ratio of 1.5%, stir at 100 rpm for 3 minutes, and test the viscosity of the thickened polyacrylamide solution at room temperature and when heated to 60°C. The specific results are shown in Table 1.

[0036] Example 2 Preparation of tackifier

[0037] The polyacrylamide solution with a viscosity of 600 cp in step C was replaced with a polyacrylamide solution with a viscosity of 800 cp, and the remaining steps were consistent with those in Example 1.

[0038] Example 3 Preparation of tackifier

[0039] The polyacrylamide solution with a viscosity of 600 cp in step C was replaced with a polyacrylamide solution with a viscosity of 1000 cp, and the remaining steps were consistent with those in Example 1.

[0040] Example 4 Preparation of tackifier

[0041] The polyacrylamide solution with a viscosity of 600 cp in step C was replaced with a polyacrylamide solution with a viscosity of 1500 cp, and the remaining steps were consistent with those in Example 1.

[0042] Example 5 Preparation of tackifier

[0043] The polyacrylamide solution with a viscosity of 600 cp in step C was replaced with a polyacrylamide solution with a viscosity of 2000 cp, and the remaining steps were consistent with those in Example 1.

[0044] Example 6 Preparation of tackifier

[0045] The polyacrylamide solution with a viscosity of 600 cp in step C was replaced with a polyacrylamide solution with a viscosity of 2500 cp, and the remaining steps were consistent with those in Example 1.

[0046] Table 1

[0047]

[0048]

[0049] As can be seen from Table 1, adding the same thiourea solution and increasing the temperature have no effect on the viscosity increase of the polyacrylamide solution. Since the stirring time is only 3 minutes, it is determined that the viscosity increase is physical viscosity increase rather than chemical cross-linking. When the viscosity of the polyacrylamide stock solution is 600cp or 2500cp, the viscosity of the final product after viscosity increase is too low or too high, so it is preliminarily confirmed that the applicable viscosity range of the polymer displacement fluid (stock solution) is 800-2000cp.

[0050] Examples 7-12

[0051] The amount of thickening solution added in step C was replaced by 0.5% and 4% thickening solution respectively, and the viscosity of the thickened polyacrylamide solution was tested at room temperature. The rest of the experimental conditions were consistent with those in Example 1. The specific experimental results are shown in Table 2.

[0052] Table 2

[0053]

[0054] It can be seen from Table 2 combined with Table 1 that the more thiourea solution is added, the higher the viscosity. The higher the viscosity of the original solution, the higher the viscosity after thickening. The common viscosity of polyacrylamide solution products in the oil field is about 5000-20000cp (a minimum of 2000cp is also acceptable), so the addition of 0.5% to 4% thickening solution is more appropriate.

[0055] Comparative Examples 1-6

[0056] The amount of thickening solution added in step C was replaced by 0.3% and 6% thickening solution at a ratio of 1.5%, and the viscosity of the thickened polyacrylamide solution was tested at room temperature. The rest of the experimental conditions were consistent with those in Example 1. The specific experimental results are shown in Table 3.

[0057] Table 3

[0058]

[0059] It can be seen from Table 3 that when 0.3% thiourea is added, the viscosity of the polyacrylamide solution changes little and it is difficult to reach the 5000cp required by the oil field; when the thiourea addition amount is 6%, the viscosity increases greatly, and only when the original solution viscosity is 1000cp does it meet the 5000-20000cp required by the oil field.

[0060] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for increasing the viscosity of a polymer displacement fluid, characterized in that: The method comprises the following steps: S1: stirring a mixture containing thiourea, polyethylene glycol and water for 1 to obtain a viscosity-enhancing solution; S2: adding the thickening solution to the polymer displacement fluid and stirring II to obtain a thickened polymer displacement fluid; In the step S2, the amount of the viscosity increasing solution added is 0.5% to 4% of the mass of the polymer displacement fluid.

2. The method according to claim 1, characterized in that In the step S1, the mass ratio of thiourea to water is 1:4 to 1:

8.

3. The method according to claim 1, characterized in that: In the step S1, the amount of polyethylene glycol added is 1% to 3% of the mass of the viscosity-increasing solution.

4. The method according to claim 1, characterized in that: In the step S1, the molecular weight of the polyethylene glycol is 200-3000.

5. The method according to claim 1, characterized in that In the step S2, the polymer displacement fluid is a polyacrylamide solution.

6. The method according to claim 1, characterized in that In the step S2, the viscosity of the polymer displacement fluid is 800-2000 cp.

7. The method according to claim 1, characterized in that In the step S2, the viscosity of the polymer displacement fluid after viscosity increase is 5000-20000 cp.

8. The method according to claim 1, characterized in that In the step S1, the rotation speed of the stirring I is 20 to 200 rpm, and the time of the stirring I is 10 to 30 min.

9. The method according to claim 1, characterized in that: In the step S2, the rotation speed of the stirring I is 50 to 500 rpm, and the time of the stirring I is 3 to 15 minutes.

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