Emulsifying functional oil displacement polymer and preparation method thereof

Abstract

The invention discloses an emulsifying functional oil displacement polymer and a preparation method thereof, and the preparation method comprises the following steps: taking acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid as basic monomers, and introducing a functional monomer into the basic monomers as a reaction monomer; the molecular structure of the functional monomer has rigid groups for improving salt resistance and shear stability; a section of polyoxypropylene chain is inserted on the basis of a hydrophobic chain and a hydrophilic head with a conventional surfactant, and polyoxyethylene and polyoxypropylene can form a layer with weak lipophilicity and weak hydrophilicity on an oil-water interface as polyoxyethylene and polyoxypropylene have weak polarity; the surfactant can effectively solubilize polar components in crude oil which are usually difficult to solubilize by alkane chains, so that the solubilizing effect of the surfactant is remarkably improved, and microemulsion is easier to form at lower concentration.

Description

Technical Field

[0001] This disclosure relates to the field of oilfield polymer flooding technology, specifically an oil displacement polymer with heavy oil emulsification function and its preparation method. Background Technology

[0002] Currently, major oilfields in my country have entered the middle and late stages of water-bearing development, requiring tertiary oil recovery methods to enhance crude oil recovery. Polymer flooding is a primary technology in tertiary oil recovery, its mechanism being to increase the oil recovery rate by increasing the viscosity of the displacing fluid to expand sweep efficiency. Acrylamide has advantages such as high monomer activity, easy polymerization with simple polymerization conditions, low price, and convenient synthesis of high molecular weight polymers. Therefore, partially hydrolyzed polyacrylamide (HPAM) and polymers modified based on it have become the most common water-soluble polymers in tertiary oil recovery. However, HPAM suffers from poor salt resistance, poor temperature resistance, and poor shear stability, causing its viscosity to decrease sharply with increasing formation salinity and temperature. Furthermore, due to the excessively high viscosity of some heavy oils, polymer solutions alone are insufficient for extraction, requiring emulsification for effective oil displacement.

[0003] Therefore, it is extremely important and urgent to develop an oil displacement polymer with high temperature resistance, high salt resistance, high shear stability and heavy oil emulsification ability. Summary of the Invention

[0004] In view of this, the present disclosure provides an emulsifying functional oil displacement polymer and its preparation method, which solves the problems of current oil displacement polymers in terms of high temperature resistance, high salt resistance, high shear stability and heavy oil emulsification ability.

[0005] Firstly, the emulsifying functional oil-displacing polymer described in this disclosure has the following molecular structural formula:

[0006]

[0007] In the formula: p:q:r:s = (0.007~0.03):0.3:(0.007~0.12):(0.0015~0.003) in molar ratio, n is 2~10, m is 2~10, x:1~4, y:2x+1.

[0008] Secondly, the method for preparing the emulsifying functional oil displacement polymer described in the first aspect includes:

[0009] Acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid are used as basic monomers, and functional monomers are introduced into the basic monomers as reactive monomers to synthesize the emulsifying functional oil displacement polymer.

[0010] The molecular structural formula of the functional monomer is:

[0011]

[0012] In the formula: n is 2 to 10, m is 2 to 10, x is 1 to 4, and y is 2x+1.

[0013] In this disclosure and possible embodiments, the synthetic route of the functional monomer includes:

[0014] By reacting ethylene oxide, propylene oxide and alkyl alcohols, a basic molecular chain composed of alkoxy groups, polyoxyethylene segments and polyoxypropylene segments is obtained.

[0015] An acetic acid group is attached to the end of the basic molecular chain, and a dimethylethylenediamine group is attached to the acetic acid group.

[0016] The functional monomer is obtained by attaching a 4-chloromethylstyrene group to the dimethylethylenediamine group.

[0017] In this disclosure and possible embodiments, the method for preparing the basic molecular chain includes:

[0018] Weigh out 1% to 3% of methanol by total mass of ethylene oxide and propylene oxide, add 0.03% to 0.05% of potassium hydroxide catalyst by total mass, and in a N2 atmosphere, adjust the temperature to 130°C, alternately introduce ethylene oxide and propylene oxide, wherein the molar ratio of propylene oxide to ethylene oxide is 1:2 to 2:1, and after reacting at this temperature for 24 to 48 hours, the first intermediate product with the basic molecular chain structure is obtained.

[0019] In this disclosure and possible embodiments, the method of attaching an acetic acid group to the end of the basic molecular chain includes:

[0020] One part of the first intermediate product and two parts of triethylamine were dissolved in dichloromethane to obtain a first mixed solution with a mass concentration of 5% to 10%.

[0021] Dissolve 1.2 parts of chloroacetic acid in dichloromethane to obtain a chloroacetic acid solution with a mass concentration of 5% to 10%.

[0022] At 0℃~5℃, the chloroacetic acid solution is added dropwise to the first mixed solution, and the reaction is stirred for 12h~24h. Then, the mixture is rotary evaporated for 2h~4h to obtain the second intermediate product.

[0023] In this disclosure and possible embodiments, the method of attaching a dimethylethylenediamine group to the acetic acid group includes:

[0024] One part of the second intermediate product and 1.2 parts of dimethylethylenediamine were dissolved in dichloromethane to obtain a second mixed solution with a mass concentration of 5% to 10%.

[0025] Two parts of 1,3-dicyclohexylcarbodiimide and 0.2 parts of 4-dimethylaminopyridine were dissolved in dichloromethane to obtain a condensation catalytic solution with a mass concentration of 5% to 10%.

[0026] At 20℃~25℃, the condensation catalytic solution is added dropwise to the second mixed solution, and the reaction is stirred for 12h~24h. After filtration and rotary evaporation for 2h~4h, the third intermediate product is obtained.

[0027] In this disclosure and possible embodiments, the method for obtaining the functional monomer by attaching the dimethylethylenediamine group to a 4-chloromethylstyrene group includes:

[0028] One part of the third intermediate and 1.2 parts of 4-chloromethylstyrene were dissolved in acetone to prepare a reaction solution with a mass concentration of 20% to 50%. The reaction was carried out at 20°C to 30°C and in the dark for 48 to 72 hours. The reaction solution was then poured into n-hexane, which produced a white precipitate. The white precipitate was washed and vacuum dried to obtain the functional monomer.

[0029] In this disclosure and possible embodiments, the method for preparing the emulsifying functional oil displacement polymer further includes:

[0030] The reaction solution is subjected to solution polymerization;

[0031] The solution polymerization steps are as follows: a set amount of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and functional monomers are dissolved in a solution to obtain a solution system with a total monomer mass fraction of 25 wt%. After adjusting the pH of the solution system to 7.8-8.0, a redox initiator is added under N2 protection at 10°C. The solution system is subjected to low-temperature polymerization. When the solution system begins to become viscous, the N2 flow is stopped. The system is allowed to stand until the reaction system temperature reaches the peak temperature and is matured for 12 hours to obtain the emulsified functional oil displacement polymer.

[0032] In this disclosure and possible embodiments, the solution system further includes:

[0033] Emulsifiers, urea, surfactants, chain transfer agents, and cosolvents.

[0034] In this disclosure and possible embodiments, the emulsifier is Span-80, the surfactant is sodium dodecyl sulfate, the chain transfer agent is sodium hypophosphite, the cosolvent is sodium bicarbonate, and the redox initiator is potassium persulfate-sodium bisulfite in a molar ratio of 1:1.

[0035] This disclosure has the following beneficial effects:

[0036] The emulsifying functional oil displacement polymer of the present invention incorporates a functional monomer into its reactive monomer. The molecular structure of this functional monomer includes rigid groups and extended surfactant groups. The rigid groups function in two ways: firstly, because the polymer's molecular chain is highly rigid, it is less affected by various ions in the solution, thus maintaining a relatively extended state even in solutions with high mineralization, i.e., maintaining a relatively high solution viscosity and exhibiting good salt resistance; secondly, because the polymer's molecular chain is highly rigid, the polymer solution is not easily degraded under the high shear forces of pumping and pipeline flow, thus maintaining a relatively high solution viscosity. The extended surfactant, based on the hydrophobic chain and hydrophilic head of conventional surfactants, incorporates additional functional groups within the hydrophobic chain and hydrophilic head. By inserting a linker group, polyoxypropylene (PPO) chain, and considering the weak polarity of polyethylene oxide (EO) and polyoxypropylene (PO), they can form a layer with weak oleophilicity and weak hydrophilicity at the oil-water interface. This property allows them to effectively solubilize polar components in crude oil that are usually difficult to solubilize by alkane chains, thus significantly improving the solubilizing effect of surfactants. As the chain length of EO and PO increases, the thickness of these interfacial layers also increases, which not only enhances the solubilizing ability of surfactants but also makes them easier to form microemulsions at lower concentrations. This effectively solves the problems of current oil displacement polymers in terms of high temperature resistance, high salt resistance, high shear stability, and heavy oil emulsification ability. Attached Figure Description

[0037] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0038] Figure 1 This is the molecular structural formula of the emulsifying functional oil displacement polymer disclosed herein;

[0039] Figure 2 This is the infrared spectrum of the polymer of Example 1 of this disclosure;

[0040] Figure 3 These are the intrinsic viscosity curves of the polymer and HPAM in Example 1 of this disclosure;

[0041] Figure 4 This is a graph showing the change in apparent viscosity of the polymer in salt water as a function of dissolution time in Example 1 of this disclosure;

[0042] Figure 5 This is the viscosity-to-concentration curve of the polymer and HPAM in Example 1 of this disclosure;

[0043] Figure 6 These are the apparent viscosity change curves of the polymer and HPAM in Example 1 at different shear rates;

[0044] Figure 7The curves show the effect of different NaCl concentrations on the apparent viscosity of the polymer and HPAM in Example 1.

[0045] Figure 8 This is a curve showing the effect of different aging times on the apparent viscosity of the polymer and HPAM in Example 1 of this disclosure;

[0046] Figure 9-1 , 9-2 The figures for Example 1 of this disclosure are the relationship between the polymer and HPAM and the changes in oil recovery rate and injection pressure with injection volume. Detailed Implementation

[0047] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0048] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0049] To address the need for improved performance in polyacrylamide polymers in terms of temperature resistance, salt resistance, shear resistance, and emulsification, this disclosure introduces a functional monomer during the synthesis of polyacrylamide. The molecular structure of this functional monomer is designed as follows, and the functions of each group in this functional monomer are as follows:

[0050]

[0051] In the molecular structure of this functional monomer, the rigid group has two functions. First, because the polymer molecular chain is relatively rigid, it is less affected by various ions in the solution. Therefore, it can maintain a relatively extended state in solutions with high mineralization, that is, it can maintain a relatively high solution viscosity and has good salt resistance. Second, because the polymer molecular chain is relatively rigid, the polymer solution is not easily degraded under the high shear of pumping and pipe flow, thus maintaining a relatively high solution viscosity.

[0052] Traditional surfactant molecules consist of a single hydrophilic and a lipophilic group, forming a thin monolayer at the oil / water interface. This structure results in an overly abrupt and lacking gradual transition from hydrophilic to lipophilic at the oil / water interface, making it extremely challenging to achieve a precise balance between hydrophilicity and lipophilicity. Extended surfactants, however, incorporate a polyoxypropylene (PPO) chain as a linker between the hydrophobic chain and the hydrophilic head of conventional surfactants. The hydrophobic chain contains C12–C18 groups, i.e., x: 1–4, y: 2x+1. The degree of polymerization (n) of the PPO chain ranges from 2 to 10, and the degree of polymerization (m) of the PEO chain also ranges from 2 to 10. Because polyethylene oxide (EO) and polyoxypropylene (PO) have relatively weak polarity, they can form a layer with both weak lipophilicity and weak hydrophilicity at the oil-water interface. This property allows them to effectively solubilize polar components in crude oil that are typically difficult to solubilize with alkane chains, thus significantly improving the solubilizing effect of the surfactant. As the chain length of EO and PO increases, the thickness of these interfacial layers also increases, which not only enhances the solubilizing ability of surfactants, but also makes them more likely to form microemulsions at lower concentrations.

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and examples; the preparation method of the oil displacement polymer described in this disclosure includes the following specific steps:

[0054] 1. Preparation of functional monomers

[0055] In this embodiment of the disclosure, the synthetic route of the functional monomer is as follows:

[0056]

[0057] Following the above functional monomer design route, the specific fabrication steps are as follows:

[0058] ①Preparation of intermediate product 1

[0059] Weigh 1% to 3% of the total mass of ethylene oxide and propylene oxide into a pressure vessel, add 0.03% to 0.05% of the total mass of ethylene oxide and propylene oxide into potassium hydroxide as a catalyst, and then install the pressure vessel.

[0060] In a nitrogen atmosphere, the temperature was adjusted to 130°C, and ethylene oxide and propylene oxide were alternately introduced through a controlled valve at a molar ratio of 1:2 to 2:1. The reaction was maintained at this temperature for 24 to 48 hours. After the reaction was completed, the reactor was cooled to room temperature, and the reactor was opened to discharge the material, yielding intermediate product 1 (the first intermediate product).

[0061] ② Preparation of intermediate product 2

[0062] Weigh 1 part of intermediate product 1 and 2 parts of triethylamine into a flask, and dissolve them in dichloromethane to a concentration of 5%–10%. Then weigh 1.2 parts of chloroacetic acid and dissolve them in dichloromethane to a concentration of 5%–10%. At 0℃–5℃, add the chloroacetic acid solution dissolved in dichloromethane dropwise into the flask and stir the reaction for 12h–24h. After the reaction is complete, rotary evaporate for 2h–4h to obtain intermediate product 2 (second intermediate product).

[0063] ③ Preparation of intermediate product 3

[0064] Weigh 1 part of intermediate product 2 and 1.2 parts of dimethylethylenediamine into a flask, and then add dichloromethane to a total concentration of 5%–10%. Dissolve 2 parts of the condensing agent 1,3-dicyclohexylcarbodiimide and 0.2 parts of the catalyst 4-dimethylaminopyridine in dichloromethane to a total concentration of 5%–10%. At 20℃–25℃, add the dichloromethane solution containing the condensing agent and catalyst dropwise into the flask, and stir the reaction for 12h–24h. After the reaction is complete, filter and rotary evaporate for 2h–4h to obtain intermediate product 3 (third intermediate product).

[0065] ④ Preparation of functional monomer YZ

[0066] Weigh 1 part of intermediate product 3 and 1.2 parts of 4-chloromethylstyrene into a flask, and add acetone to a total concentration of 20%–50%. After complete dissolution, stir and react in the dark at 20℃–30℃ for 48h–72h. After the reaction is complete, pour the solution into n-hexane, and a large amount of white precipitate will appear. Wash with n-hexane 1–2 times. Dry the washed product under vacuum at 40℃ for 8h–16h to obtain the functional monomer YZ.

[0067] 2. Preparation of oil displacement polymers

[0068] The oil displacement polymers of this disclosure are prepared according to the following synthetic route:

[0069]

[0070] In the formula: p:q:r:s = (0.007~0.03):0.3:(0.007~0.12):(0.0015~0.003) in molar ratio; n is 2~10, m is 2~10, x:1~4, y:2x+1.

[0071] Following the above synthetic route, the specific preparation process of the emulsifying functional oil displacement polymer disclosed in this invention is as follows:

[0072] ① Polymer synthesis

[0073] A certain mass of AM, AA, AMPS, and functional monomer YZ were weighed and placed in a beaker containing ultrapure water. The mixture was stirred and dissolved to obtain a solution system with a total monomer mass fraction of 25 wt%. Emulsifier Span-80, surfactant SDS, urea, chain transfer agent sodium hypophosphite, and cosolvent sodium bicarbonate were added sequentially. The pH of the solution system was then adjusted to 7.8–8.0 using NaOH solution (30 wt%). The solution was then transferred to a reactor, and the reactor temperature was adjusted to 10°C. A redox initiator, potassium persulfate-sodium bisulfite (molar ratio 1:1), was added for low-temperature polymerization. When the solution began to become viscous, N2 flow was stopped, and the mixture was allowed to stand until the reaction system reached its peak temperature. After approximately 12 hours of curing, a polymer block was obtained. The molecular structure of the polymer is shown below. Figure 1 As shown.

[0074] ② Polymer post-processing

[0075] The obtained polymer blocks were crushed using a granulator to obtain polymer granules, which were then dried at 50-60°C for 2 hours to obtain dried polymer particles. Subsequently, the dried polymer was granulated using a pulverizer and screened to obtain the oil-displacing polymer product.

[0076] The influencing factors of the preparation method of the oil displacement polymer disclosed herein are as follows:

[0077] In the synthesis of oil displacement polymers, the factors that significantly affect the reaction include: degree of hydrolysis, AMPS content, functional monomer YZ content, co-solvent content, chain transfer agent content, pH value, reaction temperature, and reaction time. Among these:

[0078] ① The effect of degree of hydrolysis on polymer properties

[0079] The degree of polymer hydrolysis, dissolution time of the polymer, and viscosity of the aqueous solution are shown in Table 1.

[0080] Table 1. Effect of degree of hydrolysis on polymer solubility and viscosity.

[0081]

[0082] The amount of sodium bicarbonate added as a cosolvent was 1 mL, sodium hypophosphite added as a chain transfer agent was 1.5 mL, sodium dodecyl sulfate (SDS) added as a surfactant was 25 g, the pH was 8, and the reaction temperature was 10℃.

[0083] It can be observed that as the degree of polymer hydrolysis increases from 0 to 25 mol%, the dissolution rate of the polymer slows down, but the viscosity of the polymer increases. Therefore, the degree of polymer hydrolysis should not be too low, and the preferred degree of polymer hydrolysis should be controlled between 20% and 27%.

[0084] ②The effect of AMPS content on polymer properties

[0085] AMPS plays a role in temperature and salt resistance in polymers. The effects of AMPS on polymer dissolution time and aqueous solution viscosity are shown in Table 2.

[0086] Table 2. Effects of AMPS content on polymer solubility and viscosity.

[0087]

[0088] The amount of sodium bicarbonate added as a cosolvent was 1 mL, sodium hypophosphite added as a chain transfer agent was 1.5 mL, SDS added as a surfactant was 25 g, the pH was 8, and the reaction temperature was 10℃.

[0089] Table 2 shows that as the AMPS content increases, the polymer dissolution rate increases and the viscosity also increases slightly. However, when the AMPS content increases from 45g to 60g, the increase in viscosity is not very significant. In addition, in order to synthesize high molecular weight polymers, the AMPS content should not be increased further, and it is advisable to control the amount of AMPS added to about 60g.

[0090] ① The effect of surfactant content on polymer properties

[0091] Surfactants can form micelles in monomer aqueous solutions, promoting the solubility of functional monomers. The micelles formed between the two promote the polymerization of monomers. Therefore, the effect of varying the amount of surfactant added on polymer viscosity and dissolution time was investigated, as shown in Table 3.

[0092] Table 3. Effects of surfactant content on polymer solubility and viscosity.

[0093]

[0094]

[0095] The amount of sodium bicarbonate added as a cosolvent was 1 mL, sodium hypophosphite added as a chain transfer agent was 1.5 mL, SDS added as a surfactant was 25 g, the pH was 8, and the reaction temperature was 10℃.

[0096] Table 3 shows that as the surfactant content increases, the polymer dissolution rate increases, and the viscosity also increases. When the amount added is 25g, the polymer viscosity reaches its peak. Therefore, the amount of surfactant added should be 25g.

[0097] ② The effect of functional monomer YZ content on polymer properties

[0098] To further clarify the effect of functional monomer content on polymer properties, the amount of functional monomer YZ added was changed, and its effect on the polymer is shown in Table 4.

[0099] Table 4. Effects of functional monomer YZ content on polymer solubility and viscosity.

[0100]

[0101] The amount of sodium bicarbonate added as a cosolvent was 1 mL, sodium hypophosphite added as a chain transfer agent was 1.5 mL, SDS added as a surfactant was 25 g, the pH was 8, and the reaction temperature was 10℃.

[0102] Table 4 shows that as the amount of functional monomer YZ increases from 2g to 10g, the polymer dissolution time increases from 25min to 125min, while the viscosity increases from 9.8mPa·s to 99.1mPa·s. Therefore, increasing the amount of functional monomer YZ increases the viscosity of the polymer solution, but also makes the polymer more difficult to dissolve; thus, the amount of functional monomer YZ added should not be excessive. When the amount of functional monomer YZ added is 7g, the polymer viscosity is 55.2mPa·s, which is greater than 50mPa·s. Therefore, the amount of functional monomer YZ added should be around 7g.

[0103] ⑤ Effect of cosolvent content on polymer properties

[0104] To improve the dissolution rate of the polymer, the content of the co-solvent was increased, and its effect on the dissolution time and viscosity of the polymer was investigated, as shown in Table 5.

[0105] Table 5. Effect of cosolvent (sodium bicarbonate) content on polymer solubility and viscosity.

[0106]

[0107] The chain transfer agent sodium hypophosphite was added in an amount of 1.5 mL, the surfactant SDS was added in an amount of 25 g, the pH was 8, and the reaction temperature was 10 °C.

[0108] Table 5 shows that as the cosolvent content increases from 1 mL to 5 mL, the polymer dissolution time decreases from 60 min to 25 min, but the viscosity decreases from 55.2 mPa·s to 35.1 mPa·s. When the cosolvent content is below 3 mL, the viscosity of the polymer solution is above 50 mPa·s. Therefore, the cosolvent content should not exceed 3 mL.

[0109] ⑥ Effect of chain transfer agent content on polymer properties

[0110] To improve the dissolution rate of polymers, in addition to increasing the content of co-solvents, the content of chain transfer agents can also be increased to reduce the molecular weight of the polymer and shorten the dissolution time. The effect of chain transfer agent content on polymer dissolution time and viscosity is shown in Table 6.

[0111] Table 6. Effect of chain transfer agent (sodium hypophosphite) content on polymer solubility and viscosity.

[0112]

[0113] The amount of sodium bicarbonate added as a co-solvent was 1 mL, the amount of SDS added as a surfactant was 25 g, the pH was 8, and the reaction temperature was 10℃.

[0114] Table 6 shows that as the chain transfer agent content increases from 1.5 mL to 4 mL, the polymer dissolution time decreases from 60 min to 25 min, but the viscosity decreases from 55.2 mPa·s to 41.0 mPa·s. Therefore, excessively high chain transfer agent content leads to a decrease in polymer molecular weight and viscosity. When the chain transfer agent content is 2.5 mL, the viscosity of the polymer solution is 56.5 mPa·s.

[0115] ⑦ Effect of pH value

[0116] To investigate the effect of pH on polymerization performance, the pH during polymerization was changed to 2, 4, 6, 8, 10, and 12, and the formulations are shown in Table 7 below:

[0117] Table 7. Effects of pH on polymer solubility and viscosity.

[0118]

[0119]

[0120] The amount of sodium bicarbonate added as a cosolvent was 1 mL, the amount of sodium hypophosphite added as a chain transfer agent was 1.5 mL, the amount of SDS added as a surfactant was 25 g, and the reaction temperature was 10℃.

[0121] Table 7 shows that as the pH increases from 2 to 12 during polymerization, the polymer dissolution rate increases, but the viscosity gradually decreases. The reason is that under acidic conditions, cross-linking reactions easily occur between polymer chains, leading to polymer insolubility; under strongly alkaline conditions, the amide portion of monomer M undergoes hydrolysis, reducing polymer viscosity. Therefore, the optimal pH for polymerization is around 8.

[0122] ⑧ Effect of reaction time

[0123] To investigate the effect of reaction time on polymerization performance, the reaction time was varied to 3 h, 6 h, 9 h, 12 h, and 15 h, and the formulations are shown in Table 8 below:

[0124] Table 8. Effect of reaction time on polymer solubility and viscosity.

[0125]

[0126] The amount of sodium bicarbonate added as a cosolvent was 1 mL, sodium hypophosphite added as a chain transfer agent was 1.5 mL, SDS added as a surfactant was 25 g, the pH was 8, and the reaction temperature was 10℃.

[0127] Table 8 shows that as the polymerization time increases from 3 h to 15 h, the polymer dissolution rate slows down, but the viscosity gradually increases. The reason is that a shorter reaction time results in a polymer that cannot form solids or is too soft, with a lower molecular weight, leading to a faster dissolution rate but lower viscosity. Extending the reaction time to over 12 h results in a more elastic polymer block with a higher molecular weight, thus slowing the dissolution rate but increasing the viscosity to over 50 mPa·s. Therefore, to ensure a more complete reaction and obtain a high molecular weight functional polymer, the polymerization time needs to be at least 12 h.

[0128] 9. The effect of temperature

[0129] To investigate the effect of temperature on polymer properties, the initiation temperature during polymerization was varied to 10, 20, 30, 40, and 50 °C, and the formulations are shown in Table 9 below:

[0130] Table 9. Effects of temperature on polymer solubility and viscosity.

[0131]

[0132] The amount of sodium bicarbonate added as a cosolvent is 1 mL, sodium hypophosphite added as a chain transfer agent is 1.5 mL, SDS added as a surfactant is 25 g, and the pH is 8.

[0133] As the polymerization temperature increases from 0 to 50°C, the polymer dissolves faster, but the viscosity gradually decreases. Analysis: At low temperatures (10°C), the gel effect during free radical polymerization of the monomers is weak. As initiation progresses and the temperature gradually increases, the molecular weight increases slowly, resulting in a higher polymer viscosity. However, as the initiation temperature gradually increases, the gel effect intensifies, causing the polymer molecular weight to be lower than at low temperatures, thus reducing viscosity but accelerating dissolution. Therefore, to obtain a high-viscosity polymer, an initial initiation temperature of around 10°C should be selected.

[0134] To make the objectives, technical solutions, and advantages of the present invention clearer, the polymer preparation method of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0135] Example 1:

[0136] 1. Preparation of functional monomers

[0137] ①Preparation of intermediate product 1

[0138] 0.205 g of methanol was weighed and placed in a pressure vessel, and 0.0004 g of potassium hydroxide was added as a catalyst. The pressure vessel was then assembled. Under a nitrogen atmosphere, the temperature was adjusted to 130 °C, and 4.4 g of ethylene oxide and 5.8 g of propylene oxide were alternately introduced through a control valve. The reaction was maintained at this temperature for 48 h. After the reaction was completed, the reaction vessel was cooled to room temperature, and the contents were discharged to obtain intermediate product 1.

[0139] ② Preparation of intermediate product 2

[0140] Weigh 0.61 g of intermediate product 1 and 2.02 g of triethylamine into a flask, and dissolve them in 50 mL of dichloromethane. Then weigh 1.13 g of chloroacetic acid and dissolve it in 20 mL of dichloromethane. At 0℃~5℃, add the chloroacetic acid solution dissolved in dichloromethane dropwise into the flask and stir the reaction for 24 h. After the reaction is complete, rotary evaporate for 4 h to obtain intermediate product 2.

[0141] ③ Preparation of intermediate product 3

[0142] Weigh 0.62 g of intermediate product 2 and 1.05 g of dimethylethylenediamine into a flask, add 30 mL of dichloromethane, and dissolve 4.12 g of condensing agent 1,3-dicyclohexylcarbodiimide and 0.24 g of catalyst 4-dimethylaminopyridine in 80 mL of dichloromethane. At 20℃~25℃, add the dichloromethane solution containing the condensing agent and catalyst dropwise into the flask, and stir the reaction for 24 h. After the reaction is complete, filter and rotary evaporate for 4 h to obtain intermediate product 3.

[0143] ④ Preparation of functional monomer YZ

[0144] 0.63 g of intermediate product 3 and 1.82 g of 4-chloromethylstyrene were weighed and added to a flask, followed by 40 ml of acetone. After complete dissolution, the mixture was stirred and reacted in the dark at 20–30 °C for 72 h. After the reaction was completed, the solution was poured into n-hexane, resulting in a large white precipitate. The precipitate was washed twice with n-hexane. The washed product was then dried under vacuum at 40 °C for 16 h to obtain the functional monomer YZ.

[0145] 2. Polymer Preparation

[0146] 184g AM, 15g AMPS, 70g AA, and 7g functional monomers were weighed and placed in a beaker containing ultrapure water and stirred to dissolve (total monomer mass fraction: 25wt%). Then, 3g emulsifier Span-80, 25g surfactant SDS, 5g urea, 1.5mL chain transfer agent sodium hypophosphite, and 1mL co-solvent sodium bicarbonate were added sequentially. The pH of the solution was then adjusted to 7.8–8.0 using NaOH solution (30wt%). The solution was transferred to a reactor, and the temperature was adjusted to 10°C. High-purity N2 was then introduced for approximately 15 minutes, followed by the addition of 0.5g initiator (potassium persulfate-sodium bisulfite, molar ratio 1:1) for low-temperature polymerization. When the solution began to become viscous, the N2 flow was stopped, and the reaction was allowed to stand until the system temperature reached its peak. After approximately 12 hours of curing, an elastic polymer block was obtained. After granulation, drying, pulverization, and sieving, the oil-displacing polymer powder of Example 1 was obtained.

[0147] 3. The following performance tests were conducted using the polymer prepared in Example 1 and HPAM (commercially available), which has a similar number-average molecular weight:

[0148] ①Infrared characterization

[0149] Infrared spectroscopy analysis was performed using the polymer from Example 1, and the results are as follows: Figure 2 As shown in the figure, the wavenumber 3432 cm⁻¹ corresponds to the NH stretching vibration peak of the amide group, 1659 cm⁻¹ to the C=O stretching vibration peak, and 1562 cm⁻¹ to the C=O stretching vibration peak of COONa, indicating that the polymer contains acrylamide (AM) monomers. The characteristic absorption peak of CH is at 2933 cm⁻¹, while 1196 cm⁻¹ and 1042 cm⁻¹ are the antisymmetric and symmetric stretching vibration absorption peaks of S=O in the sulfonic acid group, respectively. The SO stretching vibration peak is at 627 cm⁻¹, confirming the presence of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) in the polymer structure. The absorption peaks at wavenumbers 2929 cm⁻¹ and 1323 cm⁻¹ represent the CH stretching vibration and in-plane bending vibration of the long-chain alkane in the side chain of the YZ functional monomer, respectively. The absorption peak at wavenumber 1043.23 cm⁻¹ is the CO stretching vibration peak of the long-chain ether, indicating the presence of YZ functional monomers in the polymer structure.

[0150] ② Intrinsic viscosity and viscosity-average molecular weight

[0151] According to the petroleum industry standard SYT5862-2020 "Technical Requirements for Polymers for Oil Displacement", the intrinsic viscosity of amphiphilic polymers was determined using the "five-point method". Figure 3The intrinsic viscosity curve of the polymer in Example 1 is a general data graph for molecular weight determination by viscosity method. Using the Huggins and Kraemer equations, the two fitted lines were extrapolated to a concentration of "0", and the intercept obtained is the intrinsic viscosity of the polymer sample. The molecular weight was then calculated from the intrinsic viscosity. The results show that the intrinsic viscosity curves of the polymer in Example 1 all exhibit good linearity, with correlation coefficients greater than 0.90. The viscosity-average molecular weight of this polymer, calculated using the Huggins equation, is 2.12 × 10⁻⁶. 7 .

[0152] ③ Emulsifying properties

[0153] At 45℃, the oil-water interfacial tension of a 0.5% functional monomer solution is 2.21 × 10⁻⁶. -2 The oil-water interfacial tension was only 46.75 mN / m, while HPAM's effect on reducing the oil-water interfacial tension was very limited. The polymer solution from Example 1 was emulsified and mixed with crude oil at a 1:1 ratio, and the separation of the aqueous phase was observed at 45°C. After 72 hours, only 8.7% of the aqueous phase was separated, while HPAM showed no significant emulsifying effect.

[0154] ④ Solubility

[0155] The polymer dissolution rate is crucial for oil displacement injection. Figure 4 The results show that, at 45°C, the apparent viscosity of the polymer in brine increases with the extension of dissolution time, with a faster increase in the initial stage and a stable value of 52.3 mPa·s after 15 minutes, indicating that it has excellent solubility and exhibits high apparent viscosity in brine.

[0156] The polymer solution preparation method described in ② and ③ is a process of clearing and diluting, specifically: the oil displacement polymer dry powder of Example 1 is prepared into a polymer mother liquor of 5000 mg / L using 950 mg / L NaCl saline solution, and then the polymer solution concentration is diluted to 1000 mg / L using 4000 mg / L NaCl saline solution.

[0157] ⑤ Thickening properties

[0158] Figure 5 The viscosity-concentration relationship curves of the polymer in Example 1 are shown. The apparent viscosity increases with increasing polymer solution concentration. At low concentrations, the apparent viscosity of the polymer in Example 1 increases slowly, but rises rapidly when the concentration reaches 500 mg / L, while the viscosity of the HPAM solution increases essentially linearly with concentration.

[0159] ⑥ Shear resistance

[0160] Figure 6The apparent viscosity changes of the polymer in Example 1 at different shear rates are shown in the curves. The results indicate that the apparent viscosity of the polymer solution decreases with increasing shear rate, exhibiting shear-thinning behavior. After shearing, the viscosity retention rate of the polymer in Example 1 is 29.2%.

[0161] ⑦ Salt resistance

[0162] Figure 7 The effect of different NaCl concentrations on the apparent viscosity of the polymer in Example 1 is shown. With increasing NaCl concentration, the apparent viscosity of both the polymer in Example 1 and HPAM showed a decreasing trend, but the salt resistance of the polymer in Example 1 was significantly better than that of HPAM.

[0163] ⑧ Long-term stability

[0164] Figure 8 The effect of different aging times on the apparent viscosity of the polymer was demonstrated. The results showed that the polymer in Example 1 still had a viscosity of over 50 mPa·s after aging at 45°C for 130 days, exhibiting excellent long-term thermal stability, while HPAM had a viscosity of only about 15 mPa·s after aging for 130 days.

[0165] ⑨ Oil displacement performance

[0166] Figure 9-1 , 9-2 The effects of the polymer of Example 1 and HPAM on oil recovery and injection pressure as a function of injection volume are shown separately. The results indicate that the polymer of Example 1 increased oil recovery by 19.3%, demonstrating a better oil displacement effect, while HPAM only increased oil recovery by 10.9%.

[0167] In summary, the experimental process and data presented above demonstrate that the amphiphilic functional polymer prepared in Example 1 possesses excellent intrinsic viscosity, solubility, thickening properties, shear resistance, salt resistance, heavy oil emulsification properties, long-term stability, and oil displacement properties.

[0168] Example 2:

[0169] 1. The functional unit is the same as in Example 1.

[0170] 2. Polymer Preparation

[0171] Weigh 184g AM, 30g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier Span-80, 25g surfactant SDS, 5g urea, 1.5mL chain transfer agent sodium hypophosphite, and 1mL co-solvent sodium bicarbonate. Adjust the pH of the solution to 7.8–8.0 with NaOH solution (30wt%), transfer to a reactor, adjust the temperature to 10℃, and then purge with high-purity N2 for approximately 15 minutes. Add 0.5g initiator (potassium persulfate-sodium bisulfite, molar ratio 1:1) for low-temperature polymerization. Stop the N2 flow when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic polymer block is obtained. Granulation, drying, pulverization, and sieving yield the polymer powder.

[0172] 3. Performance Testing

[0173] ① At 45℃, the oil-water interfacial tension of a 0.5% functional monomer solution is 2.21 × 10⁻⁶. -2 mN / m.

[0174] ②The polymer dissolves in salt water at 45°C in 15 minutes.

[0175] ③ At 45℃, the viscosity of the polymer solution is 54.3 mPa·s.

[0176] ④ The polymer salt solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed at 45°C. After 72 hours, only 8.8% of the aqueous phase was separated.

[0177] Example 3:

[0178] 1. The functional unit is the same as in Example 1.

[0179] 2. Polymer Preparation

[0180] Weigh 184g AM, 60g AMPS, 70g AA, and 7g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier Span-80, 25g surfactant SDS, 5g urea, 1.5mL chain transfer agent sodium hypophosphite, and 1mL co-solvent sodium bicarbonate sequentially. Adjust the pH of the solution to 7.8–8.0 with NaOH solution (30wt%), transfer to a reactor, adjust the temperature to 10℃, and then purge with high-purity N2 for approximately 15 minutes. Add 0.5g initiator (potassium persulfate-sodium bisulfite, molar ratio 1:1) for low-temperature polymerization. Stop the N2 flow when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic polymer block is obtained. Granulation, drying, pulverization, and sieving yield the polymer powder.

[0181] 3. Performance Testing

[0182] ① At 45℃, the oil-water interfacial tension of a 0.5% functional monomer solution is 2.21 × 10⁻⁶. -2 mN / m.

[0183] ②The polymer dissolves in salt water at 45°C in 20 minutes.

[0184] ③ At 45℃, the viscosity of the polymer solution is 57.5 mPa·s.

[0185] ④ The polymer salt solution was emulsified and mixed with crude oil at a ratio of 1:1. The separation of the aqueous phase after emulsification was observed at 45°C. After 72 hours, only 9.0% of the aqueous phase was separated.

[0186] Example 4:

[0187] 1. The functional unit is the same as in Example 1.

[0188] 2. Polymer Preparation

[0189] Weigh 184g AM, 60g AMPS, 70g AA, and 10g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier Span-80, 25g surfactant SDS, 5g urea, 1.5mL chain transfer agent sodium hypophosphite, and 1mL co-solvent sodium bicarbonate sequentially. Adjust the pH of the solution to 7.8–8.0 with NaOH solution (30wt%), transfer to a reactor, adjust the temperature to 10℃, and then purge with high-purity N2 for approximately 15 minutes. Add 0.5g initiator (potassium persulfate-sodium bisulfite, molar ratio 1:1) for low-temperature polymerization. Stop the N2 flow when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic polymer block is obtained. Granulation, drying, pulverization, and sieving yield the polymer powder.

[0190] 3. Performance Testing

[0191] ① At 45℃, the oil-water interfacial tension of a 0.5% functional monomer solution is 2.21 × 10⁻⁶. -2 mN / m.

[0192] ②The polymer dissolves in salt water at 45°C in 25 minutes.

[0193] ③ At 45℃, the viscosity of the polymer solution is 89.7 mPa·s.

[0194] ④ The polymer salt solution was emulsified and mixed with crude oil at a ratio of 1:1. The separation of the aqueous phase after emulsification was observed at 45°C. After 72 hours, only 5.7% of the aqueous phase was separated.

[0195] Example 5:

[0196] 1. The functional unit is the same as in Example 1.

[0197] 2. Polymer Preparation

[0198] Weigh 184g AM, 60g AMPS, 70g AA, and 2g functional monomers into a beaker containing ultrapure water and stir to dissolve (total monomer mass fraction: 25wt%). Then, add 3g emulsifier Span-80, 25g surfactant SDS, 5g urea, 1.5mL chain transfer agent sodium hypophosphite, and 1mL co-solvent sodium bicarbonate. Adjust the pH of the solution to 7.8–8.0 with NaOH solution (30wt%), transfer to a reactor, adjust the temperature to 10℃, and then purge with high-purity N2 for approximately 15 minutes. Add 0.5g initiator (potassium persulfate-sodium bisulfite, molar ratio 1:1) for low-temperature polymerization. Stop the N2 flow when the solution begins to become viscous, and allow the reaction to stand until the system temperature reaches its peak. After aging for approximately 12 hours, an elastic polymer block is obtained. Granulation, drying, pulverization, and sieving yield the polymer powder.

[0199] 3. Performance Testing

[0200] ① At 45℃, the oil-water interfacial tension of a 0.5% functional monomer solution is 2.21 × 10⁻⁶. -2 mN / m.

[0201] ②The polymer dissolves in salt water at 45°C in 25 minutes.

[0202] ③ At 45℃, the viscosity of the polymer solution is 12.1 mPa·s.

[0203] ④ The polymer salt solution was emulsified and mixed with crude oil at a 1:1 ratio. The separation of the aqueous phase after emulsification was observed at 45°C. After 72 hours, only 12.5% ​​of the aqueous phase was separated.

[0204] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. An emulsifying oil displacement polymer, characterized in that, Its molecular structural formula is: In the formula: p:q:r:s = (0.007~0.03):0.3:(0.007~0.12):(0.0015~0.003) in molar ratio; n is 2~10, m is 2~10, x:1~4, y:2x+1.

2. The method for preparing the emulsifying functional oil displacement polymer according to claim 1, characterized in that, include: Acrylamide, acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid are used as basic monomers, and functional monomers are introduced into the basic monomers as reactive monomers to synthesize the emulsifying functional oil displacement polymer. The molecular structural formula of the functional monomer is: In the formula: n is 2 to 10, m is 2 to 10, x is 1 to 4, and y is 2x+1.

3. The method for preparing the emulsifying functional oil displacement polymer according to claim 2, characterized in that, The synthetic route for the functional monomer includes: By reacting ethylene oxide, propylene oxide and alkyl alcohols, a basic molecular chain composed of alkoxy groups, polyoxyethylene segments and polyoxypropylene segments is obtained. An acetic acid group is attached to the end of the basic molecular chain, and a dimethylethylenediamine group is attached to the acetic acid group. The functional monomer is obtained by attaching a 4-chloromethylstyrene group to the dimethylethylenediamine group.

4. The method for preparing the emulsifying functional oil displacement polymer according to claim 3, characterized in that, The method for preparing the basic molecular chain includes: Weigh out 1% to 3% of methanol by total mass of ethylene oxide and propylene oxide, add 0.03% to 0.05% of potassium hydroxide catalyst by total mass, and in a N2 atmosphere, adjust the temperature to 130°C, alternately introduce ethylene oxide and propylene oxide, wherein the molar ratio of propylene oxide to ethylene oxide is 1:2 to 2:1, and after reacting at this temperature for 24 to 48 hours, the first intermediate product with the basic molecular chain structure is obtained.

5. The method for preparing the emulsifying functional oil displacement polymer according to claim 4, characterized in that, The method of attaching an acetic acid group to the end of the basic molecular chain includes: One part of the first intermediate product and two parts of triethylamine were dissolved in dichloromethane to obtain a first mixed solution with a mass concentration of 5% to 10%. Dissolve 1.2 parts of chloroacetic acid in dichloromethane to obtain a chloroacetic acid solution with a mass concentration of 5% to 10%. At 0℃~5℃, the chloroacetic acid solution is added dropwise to the first mixed solution, and the reaction is stirred for 12h~24h. Then, the mixture is rotary evaporated for 2h~4h to obtain the second intermediate product.

6. The method for preparing the emulsifying functional oil displacement polymer according to claim 5, characterized in that, The method of attaching a dimethylethylenediamine group to the acetic acid group includes: One part of the second intermediate product and 1.2 parts of dimethylethylenediamine were dissolved in dichloromethane to obtain a second mixed solution with a mass concentration of 5% to 10%. Two parts of 1,3-dicyclohexylcarbodiimide and 0.2 parts of 4-dimethylaminopyridine were dissolved in dichloromethane to obtain a condensation catalytic solution with a mass concentration of 5% to 10%. At 20℃~25℃, the condensation catalytic solution is added dropwise to the second mixed solution, and the reaction is stirred for 12h~24h. After filtration and rotary evaporation for 2h~4h, the third intermediate product is obtained.

7. The method for preparing the emulsifying functional oil displacement polymer according to claim 6, characterized in that, The method for obtaining the functional monomer by attaching the dimethylethylenediamine group to a 4-chloromethylstyrene group includes: One part of the third intermediate and 1.2 parts of 4-chloromethylstyrene were dissolved in acetone to prepare a reaction solution with a mass concentration of 20% to 50%. The reaction was carried out at 20°C to 30°C and in the dark for 48 to 72 hours. The reaction solution was then poured into n-hexane, which produced a white precipitate. The white precipitate was washed and vacuum dried to obtain the functional monomer.

8. The method for preparing the emulsifying functional oil displacement polymer according to any one of claims 2-7, characterized in that, Also includes: The reaction solution is subjected to solution polymerization; The solution polymerization steps are as follows: a set amount of acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid and functional monomers are dissolved in a solution to obtain a solution system with a total monomer mass fraction of 25 wt%. After adjusting the pH of the solution system to 7.8-8.0, a redox initiator is added under N2 protection at 10°C. The solution system is subjected to low-temperature polymerization. When the solution system begins to become viscous, the N2 flow is stopped. The system is allowed to stand until the reaction system temperature reaches the peak temperature and is matured for 12 hours to obtain the emulsified functional oil displacement polymer.

9. The method for preparing the emulsifying functional oil displacement polymer according to claim 8, characterized in that, The solution system also includes: Emulsifiers, surfactants, chain transfer agents, and cosolvents.

10. The method for preparing the emulsifying functional oil displacement polymer according to claim 9, characterized in that: The emulsifier is Span-80, the surfactant is sodium dodecyl sulfate, the chain transfer agent is sodium hypophosphite, the cosolvent is sodium bicarbonate, and the redox initiator is potassium persulfate-sodium bisulfite in a molar ratio of 1:1.

Images