Preparation method of in-situ phase change gel profile control oil displacement agent
By preparing a self-assembled gel system using raw materials such as allyl urea, the problem of polymer molecule residue in polymer flooding was solved, achieving in-situ self-assembly for phase dehydration and profile control and water shut-off, thus improving oil displacement efficiency and environmental protection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO UNIV
- Filing Date
- 2022-05-11
- Publication Date
- 2026-05-05
AI Technical Summary
In existing polymer flooding technologies, undegraded polymer molecules exist in large quantities in the produced fluid, leading to difficulties in crude oil dehydration, increased environmental costs, and impact on oilfield production.
Using allyl urea, 4-vinylpyridine, acryloyloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid and 2-acrylamidotetradecylsulfonic acid as raw materials, an in-situ phase change active gel was prepared. Through multiple hydrogen bonding between carbonyl and amine groups and electrostatic interaction between anions and cations, a self-assembled gel system was formed, which can realize self-dehydration and profile control and water shut-off during the oil displacement process.
Polymer-free produced fluid was achieved within the oil reservoir, simplifying crude oil dehydration, reducing environmental costs, and improving oil displacement, profile control, and water shut-off capabilities.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of oilfield production aids, and in particular relates to a method for preparing an in-situ phase change gel profile control and displacement agent from allyl urea, vinylpyridine, acryloyloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamidotetradecylsulfonic acid and acrylamide as raw materials. Background Technology
[0002] Currently, polymer flooding has become one of the important technical means for stabilizing oil production in the mid-to-late stages of oilfields in eastern my country. Over the years, polymer flooding technology has made significant contributions to increasing oilfield production, but it has also gradually revealed many problems. One of the most serious problems is the presence of a large amount of undegraded polyacrylamide in the produced fluid due to the trenching of production wells and polymer injection wells. These polymer molecules severely interfere with crude oil dehydration, cause great difficulties in wastewater treatment, increase environmental protection costs, and restrict crude oil production. Therefore, developing an active polymer gel profile control and displacement agent that self-assembles in situ in the oil layer for indirect dehydration can solve the above-mentioned practical production problems in oilfields.
[0003] This invention relates to an in-situ phase change active gel prepared from allyl urea, 4-vinylpyridine, acryloyloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamidotetradecylsulfonic acid, and acrylamide. This gel can self-dehydrate and aggregate during oil displacement within the oil reservoir, resulting in the absence of polymer molecules in the produced fluid, facilitating crude oil dehydration, and reducing environmental costs. 2-acrylamidotetradecylsulfonic acid, as the active functional monomer, gives the gel system good oil displacement capability. Allyl urea, 4-vinylpyridine, and acrylamide monomers enable the gel system to undergo in-situ aggregation and assembly through multiple hydrogen bonds between carbonyl and amine groups, and through electrostatic interactions between 2-acrylamido-2-methylpropanesulfonic acid and acryloyloxyethyltrimethylammonium chloride. This allows the gel phase to transform into solid blocks in situ within the oil reservoir after completing its oil displacement task, producing profile control and water shut-off effects. Overall, the gel system exhibits good profile control, water shut-off, and oil displacement capabilities. Summary of the Invention
[0004] This invention first prepares a quaternary copolymer of allyl urea, 2-acrylamidotetradecyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and acrylamide as raw materials through free radical-initiated aqueous solution polymerization in a molar ratio of 1:1:5:25. Then, a terpolymer of 4-vinylpyridine, acryloyloxyethyltrimethylammonium chloride, and acrylamide is prepared through free radical-initiated aqueous solution polymerization in a molar ratio of 1:5:25. The prepared colloids are then cut, dried, and pulverized. The two polymer solid powders are then mixed in a 1:1 ratio and dissolved in water to generate a phase change gel profile control and oil displacement agent. This profile control and oil displacement agent exhibits strong profile control, water shut-off, and oil displacement capabilities, and the preparation process is reliable, providing a method for preparing an in-situ phase change gel profile control and oil displacement agent. Detailed Implementation
[0005] Example 1
[0006] (1) Weigh 0.02 mol allyl urea, 0.02 mol 2-acrylamidotetradecyl sulfonic acid, 0.1 mol 2-acrylamido-2-methylpropanesulfonic acid and 0.5 mol acrylamide and add them to a 200 mL reaction flask. Then add 100 mL of distilled water, stir to disperse and dissolve, adjust the pH value to 6.8 with 40% sodium hydroxide, purge with nitrogen for 15 minutes, add 2 mL of 0.5% potassium persulfate solution and 1 mL of 0.5% sodium bisulfite solution respectively, seal the reaction flask, then heat to 38℃ and keep the temperature for 3 hours to obtain a transparent gel block. Cool to room temperature, cut into small pieces, dry in a drying oven at 85℃ for 12 hours, take out, cool naturally to room temperature in a desiccator, pulverize, and store in a sealed bag for later use.
[0007] (2) Weigh 0.02 mol 4-vinylpyridine, 0.1 mol acryloyloxyethyltrimethylammonium chloride and 0.5 mol acrylamide and add them to a 200 mL reaction flask. Then add 100 mL distilled water, stir to disperse and dissolve, adjust the pH to 7.0 with 30% HCl, purge with nitrogen for 15 minutes, add 2 mL of 0.5% potassium persulfate solution and 1 mL of 0.5% sodium bisulfite solution respectively, seal the reaction flask, heat to 40℃, keep the temperature for 3 hours to obtain a light yellow transparent gel block, cool to room temperature, cut into small pieces, dry in a drying oven at 85℃ for 12 hours, take out, cool naturally to room temperature in a desiccator, pulverize, and store in a sealed bag for later use;
[0008] (3) Add the solid powder stored in the sealed bag obtained in Example 1 (1) and the solid powder stored in the sealed bag obtained in Example 1 (2) to the mixer, mix for 10 minutes, take it out and put it in the sealed bag for storage.
[0009] Example 2
[0010] 1.5g of the solid powder sample prepared in Example 1(3) was weighed and dispersed in tap water and seawater, respectively, and stirred at a speed of 100 rpm to dissolve. The viscosity of the solution at different dissolution times was measured using a BROOKFILD DV-III+ rheometer at 25°C. The viscosity of sample solutions of different concentrations was prepared and measured using tap water and seawater, respectively. The results are shown in Tables 1 and 2.
[0011] Table 1. Viscosities of the tap water solution from Example 1 at different dissolution times.
[0012]
[0013] Table 2 Viscosities of the sample solution from Example 1 at different concentrations (Temperature: 60℃, Shear rate: 170 s⁻¹)
[0014]
[0015] The experimental results show that, at the same concentration, the viscosity of the sample solution prepared with tap water in Example 1(3) is much higher than that of the solution prepared with seawater, and the dissolution rate of the sample in tap water is slightly greater than that in seawater.
[0016] Example 3
[0017] As time progressed, the gel in the sample of Example 1(3) transformed into a white sol, which is the initial coagulation; the sol particles aggregated and gradually separated from the water until they were completely separated, and the volume of the aggregates no longer increased, forming a stable gel block, which is the final coagulation. The time for the appearance of the sol and the completion of the gel block in tap water and seawater samples of different concentrations were observed and measured at three temperatures: 30℃, 60℃ and 90℃, respectively. The results are shown in Tables 3, 4 and 5.
[0018] Table 3 Initial and final setting times of samples at different concentrations (temperature: 30℃)
[0019]
[0020] Table 4. Initial and final setting times of samples at different concentrations (temperature: 60℃)
[0021]
[0022] Table 5. Initial and final setting times of samples at different concentrations (temperature: 90℃)
[0023]
[0024] The results showed that the initial and final setting times of the tap water solution were shorter than those of the seawater solution. In both tap water and seawater, the higher the temperature, the shorter the initial and final setting times. In addition, at all three temperatures, the lower the sample concentration in both tap water and seawater, the shorter the initial and final setting times.
[0025] Example 4
[0026] 50.0g of adhesive samples generated from tap water and seawater were weighed and made into adhesive strips with dimensions of 5cm x 1cm x 1cm, respectively, and left to stand for 24 hours. The tensile force and elongation at break of the two types of adhesive strips were measured using a tensile tester. The results are shown in Table 6.
[0027] Table 6. Strength of the adhesive block (25℃)
[0028]
[0029] The results showed that the gel-like lumps formed in tap water had relatively high tensile strength and maximum elongation at break. This is because seawater contains calcium... 2+ Mg 2+ The presence of plasma results in adhesive blocks formed in seawater that are less strong and less flexible than those formed in tap water.
[0030] Example 5
[0031] The rheological properties of the gel blocks generated in tap water and seawater of Example 1(3) were tested at 90°C using an RS150 rheometer. The results are shown in Tables 7 and 8.
[0032] Table 7 Rheology of tap water adhesive blocks
[0033]
[0034]
[0035] Table 8 Rheology of Seawater Gel Blocks
[0036] Shear rate, 1 / s Viscosity, Pa.s 1.0 3.66 1.3 3.54 1.6 3.43 2.0 3.31 2.5 3.22 3.2 3.15 3.9 3.01 5.0 2.91 6.3 2.82 7.9 2.73 10.0 2.65 12.6 2.58 15.8 2.51 20.0 2.44 25.0 2.38 31.6 2.33 39.8 2.29 50.0 2.25 63.0 2.21 79.0 2.18 100 2.16 126 2.13 158 2.11 200 2.10 251 2.08 316 2.07 398 2.06 501 2.05 631 2.04 794 2.04 1,000 2.03
[0037] The results showed that at 90℃, the shear viscosity of both types of adhesive blocks decreased with increasing shear strength, but the viscosity of both was greater than 2 Pa·s, and the viscosity of the tap water adhesive block was higher than that of the seawater adhesive block.
[0038] Example 6
[0039] The plugging rate of high-permeability cores is an important indicator for evaluating the profile control effect of profile control agents. It refers to the percentage decrease in water phase permeability of the core before and after plugging under the same conditions, denoted by η. The residual resistance coefficient is the ratio of water phase permeability before and after the injection of profile control agents, representing the ability of profile control agents to reduce core permeability, denoted by RRF.
[0040] The formulas for calculating the plugging rate and residual drag coefficient are as follows:
[0041]
[0042] In the formula:
[0043] η - Plugging rate (%);
[0044] K0 - Core permeability (DC) before plugging;
[0045] K - Core permeability (DC) after plugging.
[0046]
[0047] In the formula:
[0048] RRF - Residual Drag Coefficient;
[0049] K0 - Core permeability (DC) before plugging;
[0050] K - Core permeability (DC) after plugging.
[0051] A 30cm long sand-filled tube with an inner diameter of 2cm was used. The filling sand consisted of quartz sand of 40-60 mesh (simulating a high-permeability layer) and 100-200 mesh (simulating a low-permeability layer), which was then bonded and cured with epoxy resin. The basic parameters of the core were measured, such as length, cross-sectional diameter, pore volume, and porosity. The test flow was set up. Tap water was injected at a constant flow rate (1.0mL / min), and the water phase permeability K0 of the core before treatment was measured. Then, 0.5PV of sample gel of Example 1 (3) prepared with 0.5% tap water was injected in reverse, followed by 0.2PV of simulated formation water with a mineralization of 20000ppm. The alternating slug injection was repeated three times according to the above injection method. Then, the two ends of the core were sealed tightly and left to stand at 60℃ for 72h. The treated core was placed on a core flow tester, and the breakthrough pressure P and the water phase permeability K after sealing were measured. The sealing rate, residual resistance coefficient, and breakthrough pressure gradient P' were calculated. Following the same method described above, the samples were dissolved in seawater solution and their plugging ability was determined. The results are shown in Tables 9, 10, and 11.
[0052] Table 9. Gelatin plugging rate and residual resistance coefficient of tap water (60℃)
[0053]
[0054] Table 10 Seawater gel plugging rate and residual drag coefficient (60℃)
[0055]
[0056] Table 11 Core breakthrough pressures (60℃) for tap water and seawater gels
[0057]
[0058] The results showed that both gels had high plugging rates for highly permeable cores, but the tap water gel was significantly better than the seawater gel. This is because the gel blocks formed in tap water have good water retention and strong adhesion to hydrophilic surfaces. Under the same conditions, the presence of calcium and magnesium ions makes the gel blocks formed in seawater less tough, less adhesive, and smaller in size, resulting in a lower plugging rate and lower breakthrough pressure for the core.
[0059] Example 7
[0060] Weigh 1800g of quartz sand (particle size: 0.3-0.6mm) and 200g of crude oil and keep them in an 80℃ drying oven for 24h. Then, thoroughly stir and mix the crude oil and quartz sand evenly and set aside. Fill the core tube (diameter × length: 2.5cm × 10cm) with the above 2000g of oil sand, compacting it with an plexiglass rod as you fill. The simulated core was then sealed and fixed, and placed in a constant temperature chamber at 60°C overnight. Sample solutions with a concentration of 0.5% as described in Example 1(3) were prepared using tap water and seawater, respectively. The simulated core was then inserted into the displacement device. First, it was displaced in a 60°C constant temperature water bath with 60°C hot water (displacement rate: 3 mL / min) until no crude oil flowed out. The displaced crude oil was collected, dehydrated, and weighed. Then, 50 mL of the 0.5% sample solution was injected into the core, and the mixture was allowed to stand at 60°C for 72 hours. Then, tap water or seawater was used for displacement, and the displaced fluid was dehydrated and weighed. The recovery rate after 60°C hot water displacement of the sample from Example 1 was calculated. The results are shown in Tables 12 and 13.
[0061] Table 12. Increase in oil recovery after treatment with 0.5% Example 1(3) sample solution (tap water preparation)
[0062] Crude oil viscosity (60℃), mPa·s hydrothermal recovery rate, % Recovery improvement after treatment, % 4503 63.7 19.5 9774 52.3 18.0 13608 45.5 16.3 18905 41.8 14.7
[0063] Table 13. Increase in oil recovery after treatment with 0.5% Example 1(3) sample solution (seawater preparation)
[0064] Crude oil viscosity (60℃), mPa·s hydrothermal recovery rate, % Recovery improvement after treatment, % 4503 62.9 15.9 9774 52.2 13.4 13608 46.0 12.0 18905 42.5 11.5
Claims
1. A method for preparing an in-situ phase change gel profile control and oil displacement agent, characterized in that, Includes the following steps: (1) Weigh 0.02 mol allyl urea, 0.02 mol 2-acrylamidotetradecyl sulfonic acid, 0.1 mol 2-acrylamido-2-methylpropanesulfonic acid and 0.5 mol acrylamide and add them to a 200 mL reaction flask. Then add 100 mL of distilled water, stir to disperse and dissolve, adjust the pH value to 6.8 with 40% sodium hydroxide, purge with nitrogen for 15 minutes, add 2 mL of 0.5% potassium persulfate solution and 1 mL of 0.5% sodium bisulfite solution respectively, seal the reaction flask, then heat to 38℃ and keep the temperature for 3 hours to obtain a transparent gel block. Cool to room temperature, cut into small pieces, dry in a drying oven at 85℃ for 12 hours, take out, cool naturally to room temperature in a desiccator, pulverize, and store in a sealed bag for later use. (2) Weigh 0.02 mol 4-vinylpyridine, 0.1 mol acryloyloxyethyltrimethylammonium chloride and 0.5 mol acrylamide and add them to a 200 mL reaction flask. Then add 100 mL distilled water, stir to disperse and dissolve, adjust the pH to 7.0 with 30% HCl, purge with nitrogen for 15 minutes, add 2 mL of 0.5% potassium persulfate solution and 1 mL of 0.5% sodium bisulfite solution respectively, seal the reaction flask, heat to 40℃, keep the temperature for 3 hours to obtain a light yellow transparent gel block, cool to room temperature, cut into small pieces, dry in a drying oven at 85℃ for 12 hours, take out, cool naturally to room temperature in a desiccator, pulverize, and store in a sealed bag for later use; (3) Add the solid powder obtained in (1) and the solid powder obtained in (2) to the mixer, mix for 10 minutes, take it out and put it in a sealed bag for storage.