Non-ionic gemini type polymer surfactant and preparation method thereof

Abstract

The invention relates to a nonionic gemini type polymer surfactant and a preparation method thereof, and belongs to the technical field of oil exploitation. The nonionic gemini type polymer surfactant is prepared from the following components in percentage by mass: 9.27 percent to 18.53 percent of acrylamide, 3.97 percent to 7.94 percent of acrylic acid, 0.29 percent to 0.59 percent of sodium p-styrenesulfonate, 1.47 percent to 2.94 percent of Gemini type nonionic surfactant functional monomer, 0.4 percent to 0.6 percent of initiator and the balance of deionized water. The nonionic gemini type polymer surfactant is formed by carrying out random copolymerization on the acrylamide, the acrylic acid, the Gemini type nonionic gemini surfactant functional monomer and the sodium p-styrylsulfonate. The nonionic gemini type polymer surfactant has the functions of water phase viscosity increasing and oil phase viscosity reducing at the same time, and the limitation of a single oil displacement method is overcome.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil extraction, and particularly relates to a non-ionic gemini polymer surfactant and a preparation method thereof. Background Art

[0002] With the continuous exploitation of oil, the proportion of heavy oil is increasing, and the difficulty of heavy oil exploitation is gradually increasing. At present, the main means of heavy oil exploitation include chemical flooding, thermal flooding, gas flooding, and microbial flooding. Among them, water-soluble chemical flooding has the widest application range due to its advantages such as low cost and simple operation.

[0003] After the oil production enters the middle and late stages, the remaining oil has the characteristics of overall enrichment and partial dispersion. Water-flooded heavy oil is easily affected by the water-oil mobility ratio, and viscous fingering and water channeling are likely to occur, thus affecting the oil production efficiency. Through the water-oil mobility ratio formula, it can be seen that increasing the water phase viscosity and decreasing the oil phase viscosity can both increase the water-oil mobility ratio, increase the displacement efficiency, and improve the crude oil recovery rate. However, if a polymer flooding agent for increasing the viscosity of the water phase is used alone for heavy oil exploitation, the improvement of the recovery rate is limited, and there is also a risk of formation fracture when the formation crude oil is above 150 mPa·s. If a surfactant for reducing the viscosity of the oil phase is used alone for oil displacement, fingering and bypassing are likely to occur, resulting in uneven viscosity reduction displacement. The fundamental reason is that the viscosity of the conventional surfactant aqueous solution is low, and under the characteristics of porous media and crude oil dispersion in the reservoir, most of the viscosity reducers cannot effectively contact the crude oil and cannot form effective displacement. If the two oil displacement methods are combined, due to the influence of chemical agent components on flow rate, reservoir adsorption, etc., differential migration will occur, that is, chromatographic separation phenomenon.

[0004] Therefore, how to combine the advantages of polymer flooding agents and conventional surfactants to provide a functional polymer with the functions of increasing the viscosity of the water phase and reducing the viscosity of the oil phase at the same time, and realizing the balanced displacement of heavy oil, is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides a non-ionic gemini polymer surfactant and a preparation method thereof. The non-ionic gemini polymer surfactant can realize the integrated oil production of increasing the viscosity of the water phase and reducing the viscosity of the oil phase, and can greatly improve the oil production efficiency.

[0006] The present invention provides a non-ionic gemini polymer surfactant, which comprises the following components by mass percentage: acrylamide 9.27% - 18.53%, acrylic acid 3.97% - 7.94%, sodium p-styrenesulfonate 0.29% - 0.59%, Gemini non-ionic surfactant functional monomer 1.47% - 2.94%, initiator 0.4% - 0.6%, and the balance being deionized water; the non-ionic gemini polymer surfactant is formed by random copolymerization of the acrylamide, the acrylic acid, the Gemini non-ionic gemini surfactant functional monomer and the sodium p-styrenesulfonate;

[0007] The structural formula of the Gemini non-ionic gemini surfactant functional monomer is:

[0008]

[0009] wherein, m = 10 - 20, n = 8 - 12.

[0010] In some embodiments, the preparation method of the Gemini non-ionic surfactant functional monomer is: dissolving maleic anhydride and alkylphenol polyoxyethylene ether in toluene, adding p-toluenesulfonic acid, and carrying out an esterification reaction by a reflux method to obtain the Gemini non-ionic surfactant functional monomer.

[0011] In some embodiments, the molar ratio of the maleic anhydride to the octylphenol polyoxyethylene ether is 1:2, and the addition amount of the p-toluenesulfonic acid is 4 wt% of the mass of the maleic anhydride.

[0012] In some embodiments, the reaction temperature of the esterification reaction is 185 °C, and the reaction time is 4 - 8 h.

[0013] In some embodiments, the alkylphenol polyoxyethylene ether is selected from any one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether and dodecylphenol polyoxyethylene ether.

[0014] In some embodiments, the initiator is a mixture of an azo initiator, an oxidation initiator and a reduction initiator, and in the initiator, the molar ratio of the azo initiator, the oxidation initiator and the reduction initiator is 1:1:1.

[0015] In some embodiments, the azo initiator is selected from any one of azodiisobutylamidine hydrochloride, azodiisobimidazoline hydrochloride and azoisobutyronitrile carboxamide, the oxidation initiator is selected from any one of ammonium persulfate, potassium persulfate and sodium persulfate, and the reduction initiator is selected from any one of sodium bisulfite, sodium thiosulfate and triethanolamine.

[0016] In addition, the present invention also provides a preparation method of the non-ionic gemini polymer surfactant described in any one of the above technical solutions, comprising the following steps:

[0017] Dissolve acrylamide, acrylic acid, sodium styrene sulfonate and Gemini-type non-ionic surfactant functional monomer in deionized water, and adjust the pH to neutral to obtain a mixed reaction solution;

[0018] Pour the mixed reaction solution into a polymerization kettle, introduce nitrogen into the polymerization kettle to remove the oxygen in the polymerization kettle, and add an initiator to the polymerization kettle, and carry out a random copolymerization reaction under a nitrogen atmosphere to obtain a polymer colloid;

[0019] Cut, dry and pulverize the polymer colloid to obtain the non-ionic gemini polymer surfactant.

[0020] In some embodiments, the reaction temperature of the random copolymerization reaction is 60 °C and the reaction time is 6 h.

[0021] In some embodiments, the drying temperature is 80 °C and the drying time is 12 h.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0023] 1. The non-ionic gemini polymer surfactant provided by the present invention is randomly copolymerized from acrylamide, acrylic acid, sodium styrene sulfonate and Gemini-type non-ionic surfactant functional monomer in a specific ratio, has good solubility and viscosity increasing effect, can adjust plugging in the formation to increase the swept area, and at the same time has emulsifying viscosity reducing performance to improve the oil washing efficiency, thereby greatly improving the recovery rate of heavy oil and overcoming the limitations of a single oil displacement method;

[0024] 2. The non-ionic gemini polymer surfactant provided by the present invention has good viscosity stability, low viscosity loss rate in the preparation and transportation of the polymer, is beneficial to industrial production and application, and has good salt resistance, and can meet the exploitation requirements of offshore high-salt oil reservoirs;

[0025] 3. The preparation method of the non-ionic gemini polymer surfactant provided by the present invention has a simple and efficient preparation process, is easy to industrialize, can mass-produce a non-ionic gemini polymer surfactant with dual functions of increasing viscosity in the aqueous phase and reducing viscosity in the oil phase, provides an excellent oil displacement agent for heavy oil exploitation, and helps to improve the efficiency and economic benefits of heavy oil exploitation. Description of the Drawings

[0026] Figure 1 It is the IR spectrum of the Gemini-type non-ionic gemini surfactant functional monomer prepared in Example 2 of the present invention;

[0027] Figure 2 1H NMR spectrum of the Gemini-type nonionic gemini surfactant functional monomer prepared in Example 2 of the present invention 1 ;

[0028] Figure 3 IR spectrum of the nonionic gemini polymer surfactant prepared in Example 2 of the present invention

[0029] Figure 4 1H NMR spectrum of the nonionic gemini polymer surfactant prepared in Example 2 of the present invention 1 . Detailed implementation manners

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] The embodiments of the present invention provide a nonionic gemini polymer surfactant, which includes the following components by mass percentage: acrylamide 9.27% - 18.53%, acrylic acid 3.97% - 7.94%, sodium p-styrenesulfonate 0.29% - 0.59%, Gemini-type nonionic surfactant functional monomer 1.47% - 2.94%, initiator 0.4% - 0.6%, and the rest is deionized water; the nonionic gemini polymer surfactant is randomly copolymerized from the acrylamide, the acrylic acid, the Gemini-type nonionic gemini surfactant functional monomer, and the sodium p-styrenesulfonate;

[0032] The structural formula of the Gemini-type nonionic gemini surfactant functional monomer is:

[0033]

[0034] wherein, m = 10 - 20, n = 8 - 12.

[0035] It should be noted that the structural formula of the nonionic gemini polymer surfactant obtained by randomly copolymerizing acrylamide, acrylic acid, Gemini-type nonionic gemini surfactant functional monomer, and sodium p-styrenesulfonate is as follows:

[0036]

[0037] wherein, a, b, c, and d are the degrees of polymerization.

[0038] The above non-ionic gemini polymer surfactant is formed by random copolymerization of acrylamide, acrylic acid, sodium styrene sulfonate and Gemini non-ionic surfactant functional monomer in a specific ratio. Among them, the introduction of acrylamide and acrylic acid endows the non-ionic gemini polymer surfactant with the property of increasing the viscosity of the aqueous phase, effectively improving the viscosity of the aqueous phase, thereby increasing the water-oil mobility ratio and improving the displacement efficiency. The addition of sodium styrene sulfonate is beneficial to enhancing the stability of the non-ionic gemini polymer surfactant, enabling it to maintain good performance in a complex reservoir environment. The introduction of the Gemini non-ionic surfactant functional monomer endows the non-ionic gemini polymer surfactant with the function of reducing the viscosity of the oil phase, capable of reducing the viscosity of the oil phase, promoting the flow of crude oil, and increasing the recovery rate of crude oil. Therefore, this non-ionic gemini polymer surfactant has good solubility and viscosity-increasing effect, can adjust plugging in the formation to increase the swept area, and at the same time has the performance of emulsifying and viscosity-reducing to improve the oil washing efficiency, thus greatly increasing the recovery rate of heavy oil and overcoming the limitations of a single oil displacement method. At the same time, the above non-ionic gemini polymer surfactant has good viscosity stability, low viscosity loss rate during the preparation and transportation of the polymer, which is beneficial to industrial production and application, and it has good salt resistance and can meet the exploitation requirements of offshore high-salt reservoirs.

[0039] In a preferred embodiment, the preparation method of the Gemini non-ionic surfactant functional monomer is as follows: maleic anhydride and alkylphenol polyoxyethylene ether are dissolved in toluene, and p-toluenesulfonic acid is added, and an esterification reaction is carried out by a reflux method to obtain the Gemini non-ionic surfactant functional monomer. This preferred embodiment specifically defines the preparation method of the Gemini non-ionic surfactant functional monomer. This preparation method is simple and feasible, and the synthesized Gemini non-ionic surfactant functional monomer has good surface activity and oil-phase viscosity-reducing performance. The reaction equation of the above preparation method of the Gemini non-ionic surfactant functional monomer is as follows:

[0040]

[0041] In a preferred embodiment, the molar ratio of maleic anhydride to octylphenol polyoxyethylene ether is 1:2, and the addition amount of p-toluenesulfonic acid is 4 wt% of the mass of maleic anhydride. This preferred embodiment specifically defines the ratio of maleic anhydride to octylphenol polyoxyethylene ether and the dosage of maleic anhydride when preparing the Gemini non-ionic surfactant functional monomer, which is beneficial to improving the conversion rate of the reaction and the purity of the Gemini non-ionic surfactant functional monomer.

[0042] In a preferred embodiment, the reaction temperature of the esterification reaction is 185 °C, and the reaction time is 4 to 8 h. This preferred embodiment further defines the reaction temperature and reaction time of the esterification reaction, which is beneficial to improving the reaction rate and conversion rate.

[0043] In a preferred embodiment, the alkylphenol polyoxyethylene ether is selected from any one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, and dodecylphenol polyoxyethylene ether. Among them, the octylphenol polyoxyethylene ether can specifically be OP-10, OP-15, OP-20, etc.; the nonylphenol polyoxyethylene ether can specifically be NP-10, NP-15, NP-20, etc.; the dodecylphenol polyoxyethylene ether can be 12D-10. It should be noted that when preparing the Gemini-type nonionic surfactant functional monomer using the above-listed alkylphenol polyoxyethylene ethers, in the structural formula of the obtained Gemini-type nonionic surfactant functional monomer, m = 10 or 15 or 20, and n = 8 or 9 or 12.

[0044] In a preferred embodiment, the initiator is a mixture of an azo initiator, an oxidation initiator, and a reduction initiator. In the initiator, the molar ratio of the azo initiator, the oxidation initiator, and the reduction initiator is 1:1:1. This preferred embodiment further defines the use of a composite initiator system mixed with an azo initiator, an oxidation initiator, and a reduction initiator. Through the synergistic effect of the three initiators, the initiation efficiency can be effectively improved, enabling the polymerization reaction to proceed under milder conditions while ensuring the stability and controllability of the reaction. Among them, the azo initiator has a high initiation activity and can initiate the polymerization reaction at a lower temperature; the addition of the oxidation initiator and the reduction initiator can adjust the redox potential of the initiator, further optimizing the initiation effect and making the polymerization reaction proceed more uniformly and stably.

[0045] In a preferred embodiment, the azo initiator is selected from any one of azodiisobutylamidine hydrochloride, azodiisobutimidazoline hydrochloride, and azoisobutyronitrile carboxamide; the oxidation initiator is selected from any one of ammonium persulfate, potassium persulfate, and sodium persulfate; the reduction initiator is selected from any one of sodium bisulfite, sodium thiosulfate, and triethanolamine.

[0046] The embodiment of the present invention also provides a preparation method of the above nonionic gemini polymer surfactant, including the following steps:

[0047] S1. Dissolve acrylamide, acrylic acid, sodium p-styrenesulfonate and Gemini non-ionic surfactant functional monomer in deionized water, and adjust the pH to neutral to obtain a mixed reaction solution. In this step, it should be noted that since the Gemini non-ionic surfactant functional monomer is a viscous liquid while acrylamide and acrylic acid are solids, to ensure the uniformity of the reactant mixture, part of the deionized water can be used to prepare aqueous solutions of acrylamide, acrylic acid and sodium p-styrenesulfonate, and the remaining deionized water can be used to prepare an aqueous solution of the Gemini non-ionic surfactant functional monomer, and then the two aqueous solutions are mixed into a mixed reaction solution; alternatively, acrylamide, acrylic acid and sodium p-styrenesulfonate can be first dissolved in deionized water, and finally the Gemini non-ionic surfactant functional monomer is added and dissolved. It should also be noted that when adjusting the pH, a 10wt% sodium hydroxide solution can be used for adjustment;

[0048] S2. Pour the mixed reaction solution into a polymerization kettle, introduce nitrogen into the polymerization kettle to remove the oxygen in the polymerization kettle, and add an initiator to the polymerization kettle, and carry out a random copolymerization reaction under a nitrogen atmosphere to obtain a polymer colloid. In this step, it should be noted that the nitrogen introduction time should ensure that all the oxygen in the polymerization kettle is discharged;

[0049] S3. Cut, dry and pulverize the polymer colloid to obtain the non-ionic Gemini polymer surfactant.

[0050] The preparation method of the above non-ionic Gemini polymer surfactant has a simple and efficient preparation process, is easy to industrialize, and can prepare a non-ionic Gemini polymer surfactant with dual functions of increasing viscosity in the aqueous phase and reducing viscosity in the oil phase on a large scale, providing an excellent oil displacement agent for heavy oil exploitation and helping to improve the efficiency and economic benefits of heavy oil exploitation.

[0051] In a preferred embodiment, the reaction temperature of the random copolymerization reaction is 60°C and the reaction time is 6h. This preferred embodiment further defines the reaction temperature and reaction time of the random copolymerization reaction, which is beneficial to controlling the reaction degree of the random copolymerization reaction, thereby ensuring the molecular weight and performance of the polymer.

[0052] In a preferred embodiment, the drying temperature is 80°C and the drying time is 12h.

[0053] In order to introduce the non-ionic Gemini polymer surfactant and its preparation method provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0054] Example 1

[0055] A non-ionic gemini polymer surfactant, comprising the following components by mass percentage: acrylamide 9.27%, acrylic acid 3.97%, sodium p-styrenesulfonate 0.29%, Gemini non-ionic surfactant functional monomer 1.47%, initiator 0.4%, and the rest is deionized water; wherein, the structural formula of the Gemini non-ionic gemini surfactant functional monomer is:

[0056]

[0057] The preparation method of the above-mentioned Gemini non-ionic gemini surfactant functional monomer is as follows: In a 250 mL three-necked flask, 0.02 mol of maleic anhydride and 0.04 mol of octylphenol polyoxyethylene ether OP-10 are added to 100 mL of toluene, and p-toluenesulfonic acid is added. The addition amount of p-toluenesulfonic acid is 4 wt% of the mass of maleic anhydride; the three-necked flask is placed in an oil bath, a rotor of a magnetic stirrer is placed in the three-necked flask, and a water separator, a reflux condenser and a thermometer are installed on the three-necked flask. The esterification reaction is carried out under reflux at 300 rpm and 185 °C for X h to obtain the above-mentioned Gemini non-ionic surfactant functional monomer.

[0058] The preparation method of the above-mentioned non-ionic gemini polymer surfactant includes the following steps:

[0059] (1) According to the above ratio, acrylamide, acrylic acid, and sodium p-styrenesulfonate are dissolved in deionized water, and then the Gemini non-ionic surfactant functional monomer is added and dissolved. The pH is adjusted to 7 with 10% sodium hydroxide solution to obtain a mixed reaction solution;

[0060] (2) Pour the mixed reaction solution obtained in step (1) into a polymerization kettle, pass nitrogen into the polymerization kettle for 30 min to remove the oxygen in the polymerization kettle, heat the mixed reaction solution to 60 °C, and add an initiator for random copolymerization reaction for 6 h to obtain a polymer colloid; wherein, the initiator is azodiisobutylamidine hydrochloride, potassium persulfate and sodium bisulfite mixed in a molar ratio of 1:1:1;

[0061] (3) Cut the polymer colloid obtained in step (1), dry it in a vacuum drying oven at 80 °C for 12 h, and pulverize it to obtain the non-ionic gemini polymer surfactant.

[0062] Example 2

[0063] The difference between this example and Example 1 is that the ratios of acrylamide, acrylic acid, sodium p-styrenesulfonate and Gemini non-ionic surfactant functional monomer are different, as shown in Table 1 for details.

[0064] Example 3

[0065] The difference between this example and Example 1 lies in that the ratios of acrylamide, acrylic acid, sodium p-styrenesulfonate and the Gemini-type nonionic surfactant functional monomer are different, as shown in Table 1 in detail.

[0066] Example 4

[0067] The difference between this example and Example 1 lies in that the ratios of acrylamide, acrylic acid, sodium p-styrenesulfonate and the Gemini-type nonionic surfactant functional monomer are different, as shown in Table 1 in detail.

[0068] Example 5

[0069] The difference between this example and Example 2 lies in that the dosage of the initiator is different, as shown in Table 1 in detail.

[0070] Example 6

[0071] The difference between this example and Example 2 lies in that the dosage of the initiator is different, as shown in Table 1 in detail.

[0072] Example 7

[0073] The difference between this example and Example 2 lies in that the alkylphenol polyoxyethylene ether added when preparing the Gemini-type nonionic gemini surfactant functional monomer is octylphenol polyoxyethylene ether OP-15, and the structural formula of the Gemini-type nonionic gemini surfactant functional monomer is:

[0074]

[0075] Example 8

[0076] The difference between this example and Example 2 lies in that the alkylphenol polyoxyethylene ether added when preparing the Gemini-type nonionic gemini surfactant functional monomer is octylphenol polyoxyethylene ether OP-20, and the structural formula of the Gemini-type nonionic gemini surfactant functional monomer is:

[0077]

[0078] Example 9

[0079] The difference between this example and Example 2 lies in that the alkylphenol polyoxyethylene ether added when preparing the Gemini-type nonionic gemini surfactant functional monomer is dodecylphenol polyoxyethylene ether 12D-10, and the structural formula of the Gemini-type nonionic gemini surfactant functional monomer is:

[0080]

[0081] Comparative Example 1

[0082] The difference between this example and Example 1 lies in that the ratio of acrylamide, acrylic acid, sodium styrene sulfonate and Gemini non-ionic surfactant functional monomer is different, as shown in Table 1 in detail.

[0083] Comparative Example 2

[0084] The difference between this example and Example 2 lies in that the dosage of the initiator is different, as shown in Table 1 in detail.

[0085] Polymerization state and viscosity test

[0086] Observe the polymerization states of Examples 1-9 and Comparative Examples 1-2, and prepare the samples obtained in Examples 1-9 and Comparative Examples 1-2 into 0.2 wt% sample solutions, and measure the viscosities of the sample solutions. The results are shown in Table 1.

[0087] Table 1 Formulation and viscosity test results of Examples 1-9 and Comparative Examples 1-2

[0088]

[0089] Structure characterization

[0090] Perform structure characterization on the Gemini non-ionic gemini surfactant functional monomer obtained in Example 2, and its IR spectrum is as Figure 1 shown, and its 1 HNMR spectrum is as Figure 2 shown.

[0091] It can be seen from the IR spectrum (i.e., Figure 1 ) that: the broad peak at 3489 cm -1 is the stretching vibration peak of O-H; the absorption peaks at 2957 cm -1 and 2880 cm-1 are the absorption peaks of long-chain alkyl groups; the stretching vibration of C=O appears at 1734 cm -1 ; the stretching vibration absorption peak of C=C is at 1644 cm -1 ; the stretching vibration peak of the benzene ring skeleton is at 1610 cm -1 ; the antisymmetric stretching vibration absorption peak of the characteristic absorption peak C-O-C of polyoxyethylene ether is at 1118 cm -1 ; the symmetric stretching vibration absorption peak of C-O-C is at 953 cm -1 .

[0092] From the 1 HNMR spectrum (i.e., Figure 2)It can be seen that the peaks at chemical shifts δ = 7.10 ppm and δ = 7.01 ppm are the proton peaks on the benzene ring; the peak at chemical shift δ = 6.73 ppm is the proton peak on the double bond; the peak at chemical shift δ = 3.5 ppm is the proton peak on the oxyethylene group of polyoxyethylene ether; the peaks at chemical shifts δ = 2.17 ppm, δ = 1.59 ppm, δ = 1.06 ppm, and δ = 0.62 ppm are the proton peaks of the alkyl chain connecting to the benzene ring.

[0093] The nonionic gemini polymer surfactant prepared in Example 2 was subjected to structural characterization, and its IR spectrum is as Figure 3 shown, and its 1 HNMR spectrum is as Figure 4 shown.

[0094] It can be seen from the IR spectrum (i.e., Figure 3 ) that the broad absorption peak at 3443 cm -1 corresponds to the primary amide group; the absorption peaks at 2975 cm -1 and 2935 cm -1 belong to the asymmetric and symmetric stretching vibrations of -CH2- on the polymer main chain respectively; the absorption peak at 1672 cm -1 is related to the C-O stretching vibration; the peak at 1189 cm -1 represents the asymmetric stretching vibration of the sulfonic acid group -SO3; the peak at 1010 cm -1 represents the symmetric stretching vibration of the sulfonic acid group -SO3; the absorption peak at 1121 cm -1 represents the antisymmetric stretching vibration absorption peak of the ether bond C-O-C; the absorption peak at 953 cm -1 represents the symmetric stretching vibration absorption peak of C-O-C.

[0095] From the 1 HNMR spectrum (i.e., Figure 4 ) it can be seen that the peak at chemical shift δ = 7.6 ppm is the proton peak on the benzene ring of sodium p-styrenesulfonate; the peaks at chemical shifts δ = 7.2 ppm and δ = 6.75 ppm are the proton peaks on the benzene ring of the gemini functional monomer; the peak at chemical shift δ = 3.5 ppm is the proton peak on the oxyethylene group of polyoxyethylene ether; the peaks at chemical shifts δ = 2.10 ppm, δ = 1.55 ppm, δ = 1.03 ppm, and δ = 0.61 ppm are the proton peaks of the alkyl chain connecting to the benzene ring.

[0096] Salt resistance performance test

[0097] A series of sodium chloride solutions with different concentrations were prepared. The non-ionic gemini polymer surfactants and polyacrylamide obtained in Examples 2, 7, and 8 were respectively added to the series of sodium chloride solutions. Among them, the sample concentration was 1 wt%. The Anton Paar MCR302 rheometer was used to detect the solution viscosity of each sample under different concentrations of sodium chloride. The detection temperature was 50 °C, and the detection results are shown in Table 2.

[0098] Table 2 Viscosity of sample solutions (mPa·s) under different concentrations of sodium chloride

[0099] NaCl concentration (mg / L) 0 10000 20000 30000 40000 50000 Example 2 436 457 407 378 345 322 Example 7 385 402 345 303 281 256 Example 8 356 384 308 284 244 205 Polyacrylamide 72.6 55 28 8.5 0 0

[0100] As can be seen from Table 2, the non-ionic gemini polymer surfactants obtained in Examples 2, 7, and 8 of the present invention maintain a relatively high viscosity under different high concentrations of sodium chloride, and have a certain salt thickening ability in a sodium chloride solution of 10,000 mg / L, while the viscosity of ordinary polyacrylamide drops significantly. This shows that the non-ionic gemini polymer surfactants obtained in Examples 2, 7, and 8 of the present invention have good salt resistance.

[0101] Emulsification performance test

[0102] The non-ionic gemini polymer surfactants and polyacrylamide obtained in Examples 2, 7, and 8 were respectively prepared and diluted with deionized water into sample solutions with a concentration of 2000 mg / L. 12.5 mL of each sample solution and 12.5 mL of Bohai dehydrated crude oil were loaded into a 25 mL stoppered colorimetric tube. After being placed in a constant temperature water bath at 50 °C for 30 min, it was shaken and emulsified 300 times. The Anton Paar MCR302 rheometer was used to measure the viscosity of the emulsified emulsion, and the water separation rate was observed and calculated. The results are shown in Table 3.

[0103] Table 3 Results of emulsification viscosity reduction rate and water separation rate

[0104]

[0105] As can be seen from Table 3, the emulsification viscosity reduction effect of the non-ionic gemini polymer surfactants obtained in Examples 2, 7, and 8 of the present invention reaches a viscosity reduction rate of more than 99%, and the water separation rate within 5 h can reach about 80%, which can greatly improve the oil recovery efficiency, while ordinary polyacrylamide has no property of emulsification viscosity reduction.

[0106] Viscosity stability test

[0107] The nonionic gemini polymer surfactants prepared in Examples 2, 7, and 8 and polyacrylamide were respectively formulated and diluted with deionized water into sample solutions with a concentration of 2000 mg / L. The viscosities of the sample solutions after being placed at 50 °C under anaerobic conditions for 0 d, 3 d, 15 d, 30 d, 60 d, and 90 d were detected using an Anton Paar MCR302 rheometer. The detection results are shown in Table 4.

[0108] Table 4 Viscosities of sample solutions after being placed for different times (mPa·s)

[0109] Number of days of placement Example 2 Example 7 Example 8 Polyacrylamide 0d 19 16 14.5 8.5 3d 19.2 15.8 14.7 5.1 7d 18.9 16.1 14.1 3.8 15d 18.9 15.5 13.8 -- 30d 17.8 15.2 13.9 -- 60d 17.1 14.8 13.5 -- 90d 17.9 14.9 13.0 -- Viscosity retention rate / % 94.21 93.13 89.66 --

[0110] As can be seen from Table 4, after the nonionic gemini polymer surfactants prepared in Examples 2, 7, and 8 of the present invention were placed at 50 °C under anaerobic conditions for 90 days, the average viscosity retention rates were all about 90%. This shows that the nonionic gemini polymer surfactants prepared in Examples 2, 7, and 8 of the present invention have excellent viscosity stability.

[0111] Interfacial tension test

[0112] The nonionic gemini polymer surfactants prepared in Examples 2, 7, and 8 and polyacrylamide were respectively formulated and diluted with deionized water into sample solutions with a concentration of 2000 mg / L. Each sample solution and Bohai oil droplets were placed in a capillary, and the prepared capillary was placed in a TX500 type rotating drop interfacial tension meter. The temperature was adjusted to 50 °C and the rotation speed was adjusted to 5000 r / min. The diameter of the oil droplets was recorded at regular intervals, and the interfacial tension was calculated by computer software. The interfacial tension at equilibrium is shown in Table 5.

[0113] Table 5 Interfacial tension test results (mN / m)

[0114] Example 2 Example 7 Example 8 Polyacrylamide Interfacial tension 0.075 0.65 0.89 --

[0115] As can be seen from Table 5, the oil-water interfacial tensions between the nonionic gemini polymer surfactants prepared in Examples 2, 7, and 8 of the present invention and Bohai oil droplets are all lower than the interfacial tension of ordinary polyacrylamide. A lower interfacial tension is beneficial for driving the remaining oil in water flooding of oil reservoirs, thereby improving the oil recovery rate. This shows that the nonionic gemini polymer surfactants prepared in Examples 2, 7, and 8 of the present invention have good surface activity.

Claims

1. A nonionic gemini polymer surfactant, characterized in that, It comprises the following components by mass percentage: acrylamide 9.27% - 18.53%, acrylic acid 3.97% - 7.94%, sodium p-styrenesulfonate 0.29% - 0.59%, Gemini nonionic surfactant functional monomer 1.47% - 2.94%, initiator 0.4% - 0.6%, and the balance is deionized water; the nonionic Gemini polymer surfactant is formed by random copolymerization of the acrylamide, the acrylic acid, the Gemini nonionic Gemini surfactant functional monomer and the sodium p-styrenesulfonate; The structural formula of the Gemini nonionic Gemini surfactant functional monomer is: wherein, m = 10 - 20, n = 8 - 12.

2. The nonionic gemini polymer surfactant according to claim 1, characterized in that, The preparation method of the Gemini nonionic surfactant functional monomer is: dissolving maleic anhydride and alkylphenol polyoxyethylene ether in toluene, adding p-toluenesulfonic acid, and carrying out an esterification reaction by a reflux method to obtain the Gemini nonionic surfactant functional monomer.

3. The preparation method of the nonionic gemini polymer surfactant according to claim 2, characterized in that, The molar ratio of the maleic anhydride to the octylphenol polyoxyethylene ether is 1:2, and the addition amount of the p-toluenesulfonic acid is 4wt% of the mass of the maleic anhydride.

4. The preparation method of the nonionic gemini polymer surfactant according to claim 2, characterized in that, The reaction temperature of the esterification reaction is 185°C, and the reaction time is 4 - 8h.

5. The preparation method of the nonionic gemini polymer surfactant according to claim 2, characterized in that, The alkylphenol polyoxyethylene ether is selected from any one of octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether and dodecylphenol polyoxyethylene ether.

6. The nonionic gemini polymer surfactant according to claim 1, characterized in that, The initiator is a mixture of an azo initiator, an oxidation initiator and a reduction initiator. In the initiator, the molar ratio of the azo initiator, the oxidation initiator and the reduction initiator is 1:1:

1.

7. The nonionic gemini polymer surfactant according to claim 6, wherein The azo initiator is selected from any one of azodiisobutylamidine hydrochloride, azodiisobutimidazoline hydrochloride and azoisobutyronitrile carboxamide, the oxidation initiator is selected from any one of ammonium persulfate, potassium persulfate and sodium persulfate, and the reduction initiator is selected from any one of sodium bisulfite, sodium thiosulfate and triethanolamine.

8. The preparation method of the nonionic gemini polymer surfactant according to any one of claims 1-7, characterized in that, It comprises the following steps: Dissolve acrylamide, acrylic acid, sodium p-styrenesulfonate and Gemini nonionic surfactant functional monomer in deionized water, and adjust the pH to neutral to obtain a mixed reaction solution; Pour the mixed reaction solution into a polymerization kettle, introduce nitrogen into the polymerization kettle to remove the oxygen in the polymerization kettle, add an initiator to the polymerization kettle, and carry out a random copolymerization reaction under a nitrogen atmosphere to obtain a polymer colloid; Cut, dry and pulverize the polymer colloid to obtain the nonionic Gemini polymer surfactant.

9. The preparation method of the non-ionic gemini polymer surfactant according to claim 8, characterized in that, The reaction temperature of the random copolymerization reaction is 60°C, and the reaction time is 6h.

10. The preparation method of the nonionic gemini polymer surfactant according to claim 8, characterized in that, The drying temperature is 80°C, and the drying time is 12h.

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