Temperature-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent and preparation method thereof

Abstract

The invention belongs to the technical field of oilfield chemistry, and particularly discloses a temperature-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent and a preparation method thereof, and the temperature-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent comprises the following raw materials by weight: 4.88-14.63 wt% of acrylamide; 0 to 9.75 wt% of 2-acrylamido-2-methyl propane sulfonic acid; 0.18 wt% to 0.54 wt% of a surfactant; 0.18 wt% to 0.54 wt% of an initiator; 0.23 wt% of a cross-linking agent; 0.0735 wt% of a stabilizing agent; 73.54 wt% of water; and 22.06 wt% of styrene. The temperature-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent disclosed by the invention has relatively good emulsion stability and excellent calcium ion resistance, is relatively small in particle size, and can be suitable for some high-temperature and high-salt medium-low permeability oil reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, and in particular to a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier and its preparation method. Background Technology

[0002] As oilfield exploitation deepens and water injection continues for extended periods, severe heterogeneity arises, leading to problems such as high water production and low recovery rates. Numerous studies have found that using profile control agents to plug and modify the water injection profile is a crucial method for improving oil recovery. However, most oil reservoirs have harsh environments, and ordinary profile control agents are no longer sufficient to meet the requirements of high-temperature, high-salinity reservoirs, thus increasing the demand for temperature- and salt-resistant profile control agents.

[0003] Currently, acrylamide-based gel profile control agents are widely used. Due to their water-swelling properties, these gel-type particulate profile control agents can effectively seal large pores, achieving stable oil production and increased output. While these agents can remain stable at high temperatures for a certain period, they are prone to degradation at high temperatures. Because of their large particle size, they cannot effectively seal and control small pores, and the gelation time is long, with viscosity decreasing over time, affecting the profile control effect.

[0004] High-temperature and high-salinity reservoirs place higher demands on the performance of profile control agents. In order to address the issue that ordinary profile control agents have poor thermal stability and are prone to degradation in high-temperature and high-salinity reservoirs, thus failing to play their role in sealing and profile control, it is necessary to address these issues. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a temperature- and salt-resistant amphiphilic styrene nanosphere profile control agent and its preparation method. This agent exhibits good emulsion stability and excellent calcium ion resistance, and has a small particle size, making it suitable for some high-temperature, high-salt, medium- and low-permeability oil reservoirs.

[0006] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0007] One objective of this invention is to provide a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier, which is composed of the following raw materials in weight percentages:

[0008]

[0009] Furthermore, the surfactant is sodium fatty alcohol polyoxyethylene ether sulfate.

[0010] Furthermore, the initiator is ammonium persulfate.

[0011] Furthermore, the crosslinking agent is N,N'-methylenebisacrylamide.

[0012] Furthermore, the stabilizer is carboxymethyl cellulose.

[0013] The second objective of this invention is to provide a method for preparing a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier, comprising the following steps:

[0014] At room temperature, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, surfactant, crosslinking agent, and stabilizer are dissolved in 100g of water and poured into a three-necked flask. Styrene is added dropwise, and nitrogen is purged for 30 minutes to remove oxygen. After heating to 70℃, an initiator is added, and the reaction is carried out for 6 hours. A portion of the emulsion is taken out, and an appropriate amount of anhydrous ethanol is added to break the emulsion. The microspheres are centrifuged and dried at room temperature to obtain a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1) The preparation method of the temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention is simple, uses water as the dispersed phase, and has low cost.

[0017] 2) The temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention has a small size, with an average particle size of about 200 nm, and is suitable for medium- and low-permeability reservoirs.

[0018] 3) The temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention exhibits good emulsion stability: at a temperature of 100℃, Ca... 2+ At a concentration of 10000 mg / L, the microsphere emulsion maintained a stable state for up to 15 days when the emulsion concentration was 1%; when the emulsion concentration was less than 1%, it maintained a stable state for at least 20 days. At 100℃, when Ca... 2+ At a concentration of 100,000 mg / L, the emulsion can maintain stability for 8 days; Ca 2+ When the concentration is less than 100,000 mg / L, the emulsion can maintain stability for at least 21 days.

[0019] 4) The temperature- and salt-resistant amphiphilic styrene nanosphere profile control agent of the present invention has good thermal stability and only degrades at a high temperature of 400°C, thus exhibiting good thermal stability.

[0020] 5) The temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention has low viscosity and good flowability and injectability.

[0021] 6) The temperature- and salt-resistant amphiphilic styrene nanosphere profile control agent of the present invention has a long shelf life. At room temperature, it can maintain an emulsion state for up to one year; at 100°C, it can remain undegraded for up to 6 months.

[0022] 7) The temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention can be used in oil reservoirs with different mineralization levels, and the degree of temperature and salt resistance of the microspheres can be adjusted by adjusting the monomer ratio. Attached Figure Description

[0023] Figure 1 This is a graph showing the particle size data of the temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention.

[0024] Figure 2 This is a scanning electron microscope image of the temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention.

[0025] Figure 3 The image shows the emulsion stability of the temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier at different emulsion concentrations. From left to right, the emulsion concentrations are 0.05%, 0.1%, 0.2%, 0.5%, and 1%.

[0026] Figure 4 For the profile control agent of temperature- and salt-resistant amphiphilic styrene nanospheres, the Ca resistance 2+ Stability plot, from left to right Ca 2+ The concentrations were 0, 10000 mg / L, 30000 mg / L, 50000 mg / L, 70000 mg / L, and 100000 mg / L, respectively.

[0027] Figure 5 Thermogravimetric analysis (TGA) comparison of temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier and conventional acrylamide microspheres: (a) temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier; (b) conventional acrylamide microspheres.

[0028] Figure 6 It is a room-temperature emulsion of a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier.

[0029] Figure 7 It is a high-temperature emulsion state of a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier.

[0030] Figure 8 The temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier of the present invention has Na resistance. + Stability plot, from left to right Na + Emulsion stability graphs at different monomer ratios with concentrations of 100,000 mg / L. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0032] Unless otherwise specified, all raw materials and reagents used in the following examples were commercially available.

[0033] Specifically, this invention relates to a temperature- and salt-resistant amphiphilic styrene nanosphere profile control agent, which is composed of the following raw materials in weight percentage: acrylamide: 4.88wt%-14.63wt%, 2-acrylamido-2-methylpropanesulfonic acid (AMPS): 0-9.75wt%, surfactant (sodium fatty alcohol polyoxyethylene ether sulfate): 0.18wt%-0.54wt%, initiator (ammonium persulfate): 0.18wt%-0.54wt%, styrene 22.06wt%, crosslinking agent (N,N'-methylenebisacrylamide) 0.23wt%, stabilizer (carboxymethyl cellulose) 0.0735wt%, and deionized water 73.54wt%.

[0034] To obtain nanospheres with optimal emulsion stability, a three-factor, five-level orthogonal experiment was conducted using the monomer ratio of acrylamide to AMPS, surfactant concentration, and initiator concentration as variables. The optimal formulation from a series of orthogonal experiments was screened, with the number of days the emulsion remained stable at 100°C with an emulsion concentration of 0.2% as the indicator. Tables 1, 2, and 3 show the levels of each factor in the orthogonal experiment and related data.

[0035] Table 1. Levels of Various Factors

[0036]

[0037] Table 2. Emulsion stability data from orthogonal experiments.

[0038]

[0039] Table 2 shows that the formulation with optimal emulsion stability is AM:AMPS = 1:2, surfactant content 0.45%, initiator 0.27%, and Ca at 100℃. 2+ It can maintain stability for up to 30 days at a concentration of 10000 mg / L.

[0040] Table 3. Analysis of orthogonal experimental data

[0041]

[0042] As shown in Table 3, the monomer ratio has a significant impact on the emulsion stability of microspheres, followed by surfactants, while initiators have little effect on emulsion stability.

[0043] To investigate the effect of monomer ratio on emulsion stability, a conditional experiment was conducted with monomer ratio as the variable. The experimental results show that microsphere profile control agents suitable for different oil reservoirs can be prepared by adjusting the ratio of acrylamide to AMPS.

[0044] Example 1

[0045] This embodiment provides a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier, which is composed of the following raw materials in weight percentage: 4.88% acrylamide monomer, 9.74% 2-acrylamide-2-methylpropanesulfonic acid monomer, 83.6% styrene, 0.45% surfactant (sodium fatty alcohol polyoxyethylene ether sulfate), 0.27% initiator (ammonium persulfate), 0.87% crosslinking agent (N,N'-methylenebisacrylamide), 0.28% stabilizer (carboxymethyl cellulose), and 100g deionized water.

[0046] The preparation method is as follows: At room temperature, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, sodium fatty alcohol polyoxyethylene ether sulfate (surfactant), N,N'-methylenebisacrylamide (crosslinking agent), and carboxymethyl cellulose (stabilizer) are dissolved in 100g of water and poured into a three-necked flask. Styrene is added dropwise, followed by nitrogen purging for 30 minutes to remove oxygen. After heating to 70℃, ammonium persulfate (initiator) is added. After reacting for 6 hours, a portion of the emulsion is taken out and an appropriate amount of anhydrous ethanol is added to break the emulsion. The microspheres are centrifuged and dried at room temperature to obtain the temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier.

[0047] The microsphere emulsion was prepared into a 0.2% emulsion, and then prepared into different Ca... 2+ The stability of the solution of a certain concentration was observed by placing it in a 100℃ oven. The initial state was taken as the time of placing it in the oven, and the final state was taken as the emulsion coagulation. The emulsion stability was recorded.

[0048] 1. Particle size data and morphology images were obtained using conventional methods, as shown below. Figure 1 As shown, the scanning electron microscope image is as follows: Figure 2 As shown, the particle size data and the state of the microspheres under scanning electron microscopy indicate that the particle size range of the microspheres is relatively concentrated, and their shape is regular and spherical.

[0049] 2. Emulsion stability:

[0050] (1) At 100℃, Ca 2+ The effect of different emulsion concentrations (0.05%, 0.1%, 0.2%, 0.5%, 1%) on the stability of the microsphere emulsion at a concentration of 10000 mg / L is as follows: Figure 3 As shown.

[0051] Figure 3As can be seen, when the emulsion concentration is 1%, the microsphere emulsion can remain stable for up to 15 days; when the emulsion concentration is 0.5%, the microsphere can remain stable for 22 days; when the emulsion concentration is 0.2%, the microsphere can remain stable for 30 days; when the emulsion concentration is 0.1%, the microsphere can remain stable for 36 days; and when the emulsion concentration is 0.05%, the microsphere can remain stable for 60 days.

[0052] (2) At 100℃, when the emulsion concentration is 0.2%, different Ca 2+ The effect of concentrations (0, 10000 mg / L, 30000 mg / L, 50000 mg / L, 70000 mg / L, 100000 mg / L) on the stability of microsphere emulsions is as follows: Figure 4 As shown. Figure 4 It can be seen from this that when Ca 2+ At a concentration of 100,000 mg / L, the microspheres can maintain emulsion stability for 8 days. 2+ At a concentration of 10000 mg / L, the emulsion can maintain stability for 30 days.

[0053] 3. Thermal stability: Using conventional styrene microspheres as a control, the test results are as follows: Figure 5 As shown.

[0054] Figure 5 (a) in the figure is the thermogravimetric curve of the temperature- and salt-resistant amphiphilic nanosphere profile control agent. Figure 5 (b) in the figure shows the thermogravimetric curve of the acrylamide microspheres. Figure 5 The thermogravimetric curves show that the temperature- and salt-resistant amphiphilic nanosphere profile control agent only exhibits significant weight loss after 426.8℃, while the acrylamide microspheres show the fastest weight loss at 390.08℃. Therefore, the temperature- and salt-resistant amphiphilic nanosphere profile control agent of this invention has better thermal stability than acrylamide microspheres.

[0055] 4. Shelf life:

[0056] (1) The emulsion state at room temperature is as follows Figure 6 As shown in Figure 6, one year after the synthesis of the microsphere emulsion, it remains a uniform milky white liquid with low viscosity, exhibiting good flowability and injectability.

[0057] (2) State in 100℃ oven Figure 7 As shown, by Figure 7 It can be seen that the microspheres were placed in a 100℃ oven for up to 6 months without degradation, which shows that the microspheres have the characteristic of long-term effectiveness and can be used for long-term sealing in the formation.

[0058] Example 2

[0059] This embodiment provides a temperature- and salt-resistant amphiphilic styrene nanosphere profile modifier, which is composed of the following raw materials in weight percentage: 8.77% acrylamide monomer, 5.85% 2-acrylamide-2-methylpropanesulfonic acid monomer, 83.6% styrene, 0.45% sodium fatty alcohol polyoxyethylene ether sulfate (surfactant), 0.27% ammonium persulfate (initiator), 0.87% N,N'-methylenebisacrylamide (crosslinking agent), 0.28% carboxymethyl cellulose (stabilizer), and 100g deionized water.

[0060] The preparation method is as follows: At room temperature, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, sodium fatty alcohol polyoxyethylene ether sulfate (surfactant), N,N'-methylenebisacrylamide (crosslinking agent), and carboxymethyl cellulose (stabilizer) are dissolved in 100g of water and poured into a three-necked flask. Styrene is added dropwise, followed by nitrogen purging for 30 minutes to remove oxygen. After heating to 70℃, ammonium persulfate (initiator) is added. After reacting for 6 hours, a portion of the emulsion is taken out and an appropriate amount of anhydrous ethanol is added to break the emulsion. The microspheres are centrifuged and dried at room temperature to obtain styrene microspheres.

[0061] The microsphere emulsion was prepared into a 0.2% emulsion, and then prepared into a Na... + A 10000 mg / L solution was placed in a 100℃ oven to observe its stability. The initial state was defined as the time the solution was placed in the oven, and the final state was defined as emulsion coagulation. The emulsion stability was recorded. (Na...) + Emulsion stability results are as follows Figure 8 As shown.

[0062] Depend on Figure 8 It can be seen that when the monomer ratio is 3:2, the microsphere emulsion is resistant to Na+ at 100℃. + It can last up to 50 days and has good emulsion stability.

[0063] Therefore, by changing the monomer ratio of acrylamide to 2-acrylamido-2-methylpropanesulfonic acid, a product with better Ca2+ resistance can be synthesized. 2+ Or Na + Performance-enhancing emulsions.

[0064] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent, characterized in that: The heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent is composed of the following raw materials in percentage by weight:

2. The heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent according to claim 1, characterized in that: The surfactant is sodium fatty alcohol polyoxyethylene ether sulfate.

3. The heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent according to claim 1, characterized in that: The initiator is ammonium persulfate.

4. The heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent according to claim 1, characterized in that: The cross-linking agent is N,N'-methylenebisacrylamide.

5. The heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent according to claim 1, characterized in that: The stabilizer is carboxymethyl cellulose.

6. A method for preparing the heat-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent according to any one of claims 1 to 5, characterized in that: The following steps are involved: At room temperature, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, a surfactant, a crosslinking agent and a stabilizer are added to 100 g of water to fully dissolve, poured into a three-necked flask, styrene is added dropwise, and then nitrogen is passed to deoxygenate for 30 minutes. After the temperature is raised to 70°C, an initiator is added, and after reacting for 6 hours, part of the emulsion is taken out and an appropriate amount of anhydrous ethanol is added to break the emulsion. The microspheres are centrifuged with a centrifuge and dried at room temperature to obtain a temperature-resistant and salt-resistant amphiphilic styrene nano-microsphere profile control agent.

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