CN115197686B

CN115197686B - Application of surfactant in thick oil emulsification and viscosity reduction

Info

Publication number: CN115197686B
Application number: CN202210849176.9A
Authority: CN
Inventors: 杨敬一; 司英伟; 徐心茹; 刘涛
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2022-07-19
Filing date: 2022-07-19
Publication date: 2023-09-29
Anticipated expiration: 2042-07-19
Also published as: CN115197686A

Abstract

The invention relates to an application of a surfactant in thick oil emulsification and viscosity reduction, wherein the surfactant is a boron-containing surfactant, and the structural formula is shown as follows:wherein m is 17-21, n is 5-9. The boron-containing surfactant according to the invention has a good viscosity reduction rate. The boron-containing surfactant according to the present invention may also be formulated to form a built surfactant, the components acting synergistically to provide good viscosity reduction rates.

Description

Application of surfactant in thick oil emulsification and viscosity reduction

Technical Field

The invention relates to viscosity reduction of thick oil, in particular to application of a surfactant in thick oil emulsification viscosity reduction.

Background

With continuous consumption of traditional light crude oil and increasingly reduced reserves, the oil price rises, and the conventional crude oil production cannot meet the requirements of national economic development, so that the heavy oil (also called heavy crude oil) resource is more and more emphasized. The world has abundant thick oil resources, and the total amount of the world petroleum resources is estimated to be about 9 to 13 trillion barrels, wherein about 30 percent of the world petroleum resources are conventional crude oil, and the rest 70 percent of the world petroleum resources are thick oil. With the development of new technology, the yield of thickened oil is steadily increased, and oil sand, super thickened oil and other unconventional petroleum resources become main sources.

The vast majority of thickened oil resources are distributed in venezuela, canada, the united states and other countries. The largest heavy oil field is in the orinoco petroleum band in venezuela, accounting for 90% of the world's extra heavy oil and heavy oil reserves. The method has the advantages that the method also has quite abundant thick oil resources in China, the land thick oil resources are about 200 hundred million tons, and the thick oil resources are mainly distributed in 70 oil fields of 12 sedimentary basins. At present, the total yield of thickened oil in the whole country exceeds 2500 ten thousand tons, and the production base is mainly in oil fields such as Liaohe, kelamayi, victory, bohai sea, tarim and the like. The thick oil must be transported from the wellhead to the refinery or port via pipelines.

Because of the high viscosity, high density, poor fluidity of the thickened oil and the easy deposition of asphaltenes and waxes, which cause the blockage of reservoir pores and conveying pipelines, the exploitation and the gathering costs are huge. In order to facilitate the exploitation and the centralized transportation of the thick oil, researchers at home and abroad propose various methods, including the technology of heating the thick oil at an elevated temperature, diluting the light oil, using a viscosity reducing modifier and the like. The production and collection of thick oil by heating or dilution is costly and subject to field conditions. The viscosity reduction method using the viscosity reducer is more and more important, and can be divided into surfactant viscosity reduction, microorganism viscosity reduction and the like according to the difference of viscosity reduction principles. The addition of surfactants to the thick oil forms an O/W emulsion, which will significantly reduce the viscosity. Moreover, the surfactant is used for emulsification and viscosity reduction, the technology process is simple, the cost is low, the implementation is easy, the method has advantages in the aspects of improving the recovery ratio of thickened oil, reducing the transportation cost of pipelines and the like, and the method is more and more attractive for researchers. The thick oil emulsification and viscosity reduction means that a surfactant is added into the water-containing thick oil to promote the phase inversion of the water-in-oil thick oil emulsion into an oil-in-water emulsion, and the viscosity of the oil-in-water emulsion can be reduced by more than 2 orders of magnitude. In the emulsification and viscosity reduction technology, the performance of an emulsifier is most important, and particularly, a surfactant with excellent emulsification performance under high-salt and high-temperature conditions is particularly important. Therefore, research on the surfactant for emulsifying and viscosity-reducing the heavy oil is developed, and the surfactant has very important significance for efficient development and heavy oil gathering and transportation of heavy oil reservoirs in China.

The proportion of thick oil in the total crude oil production also increases year by year. However, high asphaltene and colloid contents in the thickened oil lead to high viscosity and poor fluidity, which brings great difficulty to exploitation and transportation. The emulsification and viscosity reduction of thick oil are attractive viscosity reduction methods. However, no surfactant is known to be well suited for viscosity reduction of heavy oil.

Disclosure of Invention

In order to solve the problem that no surfactant can be well used for viscosity reduction of thick oil in the prior art at present, the invention provides application of the surfactant in emulsification viscosity reduction of thick oil.

The surfactant is a boron-containing surfactant, and has the following structural formula:

wherein m is 17-21, n is 5-9.

The boron-containing surfactant (i.e., SYW surfactant) according to the present invention, which is an anionic-nonionic surfactant, has not only excellent temperature resistance and salt resistance but also excellent emulsifying viscosity reduction properties. Moreover, the boron-containing surfactant has the advantages of thermal stability, high boiling point, no toxicity and no corrosiveness, and good surface activity. The electron structure of the boron atom has a free P electron orbit and obvious electron deletion. When boric acid is attacked by hydroxide ions in solution, the structure of boric acid changes from hydrophobic to hydrophilic. The borate intermediate contains active hydroxyl groups and can further react with substances containing elements such as nitrogen, sulfur, chlorine, phosphorus and the like to generate different types of surfactants. The invention synthesizes SYW surfactant by taking 1, 3-Propanediol Polyether (PPG), boric acid, maleic anhydride and sodium metabisulfite as raw materials. Preferably, PPG: boric acid: maleic anhydride: the synthetic molar ratio of the sodium metabisulfite is 1:0.43:1.6:0.81.

Preferably, the boron-containing surfactant is dissolved in water to form an emulsion water phase, the thickened oil and the emulsion water phase are mixed to obtain a thickened oil emulsion, and the thickened oil emulsion is emulsified to form an oil-in-water emulsion to reduce the viscosity of the thickened oil.

Preferably, the concentration of the boron-containing surfactant in the thick oil emulsion is between 1000mg/L and 2500 mg/L.

Preferably, the concentration of the boron-containing surfactant in the thick oil emulsion is between 1000mg/L and 1500 mg/L.

Preferably, the boron-containing surfactant, oleic acid and ethanolamine are compounded to form a compound surfactant (namely SYG compound surfactant), the compound surfactant is dissolved in water to form an emulsion water phase, the thick oil and the emulsion water phase are mixed to obtain thick oil emulsion, and the thick oil emulsion is emulsified to form an oil-in-water emulsion so as to reduce the viscosity of thick oil.

Preferably, the ratio of the boron-containing surfactant to the ethanolamine to the oleic acid is 3:1:1. In this preferred embodiment, the surfactant has the formula:

preferably, the concentration of the built surfactant in the thickened oil emulsion is between 1000mg/L and 2500 mg/L.

Preferably, the emulsification temperature is between 40 ℃ and 80 ℃.

Preferably, the water content of the thickened oil emulsion is between 30% and 80%.

Preferably, the viscosity of the thickened oil is between 500 and 30000 mpa.s. In a preferred embodiment, the viscosity of the thickened oil is between 800 and 8000 mPa.s.

The boron-containing surfactant according to the invention has a good viscosity reduction rate. For example, aiming at the Xinjiang thick oil emulsion with the water content of 50 percent, the viscosity reduction rate can reach 97.3 percent when the addition amount is 1500mg/L at 70 ℃, and the water division rate is 79 percent after 1 hour, thus having good emulsification viscosity reduction effect and being capable of rapidly breaking and dehydrating. The boron-containing surfactant according to the present invention may also be formulated to form a built surfactant, the components acting synergistically to provide good viscosity reduction rates. For example SYW, oleic acid and ethanolamine are compounded according to the proportion of 3:1:1 to obtain a compound surfactant SYG, and the viscosity reduction rate of the compound surfactant SYG is up to 98.6% when the water content of the compound surfactant SYG is 50% for Xinjiang thick oil emulsion at 70 ℃ and the addition amount of the compound surfactant is 1500mg/L, which shows that SYW, ethanolamine and oleic acid have remarkable synergistic effect.

Drawings

FIG. 1 is a flow chart of the synthetic process of SYW surfactant;

FIG. 2 is X ₁ And X ₂ A response surface graph of interaction versus viscosity reduction rate;

FIG. 3 is X ₁ And X ₃ A response surface graph of interaction versus viscosity reduction rate;

FIG. 4 is X ₂ And X ₃ A response surface graph of interaction versus viscosity reduction rate;

FIG. 5 is a FT-IR spectrum of PPG, S-1, S-2 and SYW surfactants;

FIG. 6 is a plot of PPG, S-1, S-2 and SYW surfactants ¹ H NMR spectrum;

FIG. 7 is a plot of PPG, S-1, S-2 and SYW surfactants ¹³ C NMR spectrum;

FIG. 8 is a full spectrum scanning analysis map of SYW surfactant;

FIG. 9 is a C1s high resolution XPS spectrum of SYW surfactant;

FIG. 10 is an O1s high resolution XPS spectrum of SYW surfactant;

FIG. 11 is a S2 p high resolution XPS spectrum of SYW surfactant;

FIG. 12 is a B1s high resolution XPS spectrum of SYW surfactant;

FIG. 13 shows the effect of different surfactants on the emulsification viscosity reduction rate of heavy oil;

FIG. 14 shows the effect of SYW surfactant concentration on the viscosity reduction rate of a thick oil emulsion;

FIG. 15 shows a viscous oil viscosity-temperature curve;

FIG. 16 shows the effect of temperature of SYW surfactant on the viscosity reduction rate of a thick oil emulsion;

FIG. 17 shows the effect of SYW surfactant concentration on the water cut of a thick oil emulsion;

FIG. 18 shows the effect of SYG on viscosity reduction of a thick oil emulsion by the concentration of SYG-built surfactant;

FIG. 19 shows the effect of water cut before SYG complex surfactant addition on thick oil emulsification viscosity reduction;

FIG. 20 shows the effect of water cut on the emulsification and viscosity reduction of heavy oil after SYG-complex surfactant addition;

Fig. 21 shows the effect of temperature of SYG-formulated surfactant on viscosity reduction rate of thick oil emulsions.

Detailed Description

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The experimental reagents used in the examples below are shown in table 1 below.

TABLE 1 Experimental reagents

The experimental apparatus used in the examples below is shown in table 2 below.

Table 2 laboratory apparatus

The preparation method according to the present invention firstly comprises synthesizing an ester intermediate S-1 having a B-O structure by boric acid modification on the basis of polyethylene oxide propylene oxide monopropylene glycol polyether (PPG). The boric acid structural unit being a plane triangle, each boron atom passing through sp ² The hybridization is combined with oxygen atoms, boron is an atom with electron deficiency, and is easy to carry out coordination reaction with hydroxyl groups of PPG, and boric acid ester intermediates S-1 are generated after dehydration. Specifically, as shown in FIG. 1,3 propylene glycol polyether and Boric acid (Boric acid) undergo an esterification reaction to produce an intermediate propylene glycol polyether borate (S-1).

The intermediate S-1 contains both-OH connected with B and-OH connected with C, and the preparation method according to the invention comprises the following steps of further esterification reaction with Maleic Anhydride (MA) under the catalysis of p-toluenesulfonic acid to generate an intermediate S-2 with a structure of C=C. Specifically, as shown in FIG. 1, maleic Anhydride (MA) and S-1 are subjected to esterification reaction to generate an intermediate propylene glycol polyether borate maleate (S-2).

The preparation process according to the invention next comprises reacting S-2 with sodium metabisulfite under the action of cetyltrimethylammonium bromide to give a catalyst having the formula-SO ₃ ^- A SYW surfactant of the group. Thus, the synthesized surfactant molecule contains both anionic sulfonate groups and nonionic propylene oxide and ethylene oxide chain links. Specifically, as shown in FIG. 1, sodium metabisulfite (Na ₂ S ₂ O ₅ ) And S-2 to obtain the boron-containing anionic-nonionic surfactant (i.e. SYW surfactant).

The reaction equation of the preparation method according to the invention is as follows:

synthesis of SYW surfactant

1,3 propylene glycol polyether (PPG) produced by Nantong and Rake chemical industry Co., ltd is selected as a synthetic raw material, and the molar ratio of Ethylene Oxide (EO) to Propylene Oxide (PO) in the product is 6:4, HLB value 13.

And respectively weighing a proper amount of PPG and boric acid according to a certain molar ratio, placing the PPG and the boric acid into a toluene solution, pouring the solution into a four-neck flask, and adding a proper amount of toluene as a water carrying agent. Purging for 20min under nitrogen atmosphere, stirring, heating to 135 ℃, and carrying out boric acid esterification reaction under nitrogen protection until the interface between water and toluene in the water separator is not changed, wherein the toluene layer is clear and transparent, which indicates that the esterification reaction is completed, cooling to room temperature, and the reaction time is 1.5h. Toluene solvent was removed using a K-SY5000 rotary evaporator to give intermediate S-1 as a pale yellow viscous liquid with no pungent odor.

And (3) weighing maleic anhydride with a certain molar ratio, adding the maleic anhydride into a three-neck flask containing S-1, adding toluene as a water carrying agent, preparing NaOH solution with the concentration of about 10%, and regulating the pH value of the reactant to be neutral. Purging for 20min under nitrogen atmosphere, stirring, dropwise adding p-toluenesulfonic acid catalyst, and heating to a reaction temperature of 135 ℃. The interface between water and toluene in the water separator is not changed any more after the esterification reaction, the toluene layer is clear and transparent, and the temperature is reduced and cooled to room temperature. The K-SY5000 rotary evaporator is used for removing redundant toluene, and the S-2 product is golden yellow in appearance, is thick liquid at normal temperature and has no pungent smell.

Sodium metabisulfite and S-2 with certain molar ratio are weighed and dissolved in water, poured into a three-neck flask, and the pH value of a reaction system is regulated to be neutral. Purging for 20min under nitrogen atmosphere, stirring, dropwise adding catalyst cetyl trimethyl ammonium bromide, heating to the reaction temperature of 100 ℃, and reacting for 4h. After the completion of the reaction, water was distilled off from the solution by a K-SY5000 rotary evaporator to obtain a pale yellow viscous liquid SYW (boron-containing anionic-non-surfactant).

Preparation of thick oil emulsions

According to the analysis data (table 3 below) of the formation water in the oilfield, the simulated formation water is self-configured, and the mineralization degree of the simulated formation water reaches 12876 mg.L ^-1 Is calcium chloride type water with high mineralization degree.

TABLE 3 oilfield formation water analysis data

And (3) weighing a certain mass of SYW surfactant, dissolving the SYW surfactant in simulated formation water, fully stirring the mixture by using a glass rod, standing the mixture, and clarifying and transparentizing the solution to obtain an emulsion water phase.

The oil sample was obtained from Xinjiang oil field, and the basic properties are shown in Table 4 below. The density of the oil sample at 20 ℃ is 953.4 kg.m ^-3 The viscosity at 50℃was 1500 mPa.s, so that it was found that the experimental oil was a thick oil with a high asphaltene gum content.

TABLE 4 Property data for Xinjiang thick oil 1

And respectively placing the thick oil and the water phase in a constant-temperature water bath at 70 ℃ (emulsification temperature) for preheating for 30min, then pouring the thick oil into the water phase according to different volume ratios, and stirring for 10min at a rotating speed of 5000r/min in a homogenizer to obtain thick oil emulsion.

Determination of the viscosity of a thickened oil emulsion

Pouring the prepared thick oil emulsion into a test measuring cup, and measuring the viscosity of the thick oil emulsion at a set temperature. The viscosity reduction rate formula is shown as formula 1:

wherein: f-viscosity reduction rate; mu 0-viscosity of thick oil mPa.s; mu-viscosity of the thickened oil emulsion mPa.s after addition of the surfactant.

Method for measuring stability of thick oil emulsion

The stability of the thick oil emulsion was determined by "bottle test", the prepared oil-water emulsion was poured into a graduated glass test tube at 70℃and allowed to stand at constant temperature, the volume of water removed was recorded every 30min, and the settling time was 1.5h. The stability is expressed in terms of cutwater, the greater the cutwater, the poorer the emulsion stability. The water division ratio is calculated as formula 2:

Wherein:-water cut rate; v (V) _t -a water splitting volume mL; v (V) ₀ Total water volume mL.

SYW surfactant synthesis ratio optimization

The inventors found that: the reaction temperature, the reaction time and the catalyst consumption have little influence on the molecular structure of esterification and sulfonation reaction products, but the reaction raw material ratio has great influence on the performance of the synthesized anionic-non-surfactant, so the molar ratio of reactants is focused on.

The invention uses the response surface curve method as an analysis tool, thereby improving the efficiency, saving the time and the cost and ensuring the accuracy and the effectiveness of the result. The response surface method is an effective method of revealing the influence of process parameters through a small number of experiments. Design-Expert.V8.0.6.1r software was used with the Box-Behnken experimental Design. The synthesis ratio of each reaction stage is an important parameter affecting the structure of the product. Selecting PPG/boric acid molar ratio (X ₁ ) PPG/maleic anhydride molar ratio (X ₂ ) And PPG/sodium metabisulfite molar ratio (X ₃ ) The viscosity reduction rate of the emulsified thick oil emulsion of the synthetic surfactant is selected as a response variable for the independent variable of the synthetic proportion of the SYW surfactant. In three factors X ₁ 、X ₂ 、X ₃ And 17 trials were performed at three levels. The conditions for applying the synthetic surfactant to the emulsification and viscosity reduction of the thick oil are as follows: the concentration of the surfactant is 1000mg/L, the emulsification temperature is 70 ℃, and the oil-water ratio is 1:1. for the determined independent variables, the ranges of each variable used in the experimental study are shown in table 5 below.

TABLE 5 SYW surfactant Synthesis ratio optimization Box-Behnken test factors and level

The experimental results and analysis are shown in table 6 below.

TABLE 6 SYW surfactant Synthesis conditions optimization Box-Behnken experimental results

In experimental studies, a second order polynomial model equation is derived from the process variables of the design matrix, and the response of each factor at a given level is predicted from the equation. The level of each factor is specified in the original unit. Based on Design-expert.v8.0.6.1r data analysis software, predicting the response of the viscosity reduction rate f according to experimental data to obtain a formula 3 of a quadratic polynomial equation:

Y＝117.10-63.24*X ₁ +29.83*X ₂ -67.65*X ₃ -11.07*X ₁ *X ₂ +80.37*X ₁ *X ₃ –18.55*X ₂ *X ₃ +6.20*X ₁ ² -2.51*X ₂ ² +33.69*X ₃ ² (3)

Wherein Y is the predicted response (viscosity reduction rate f), X ₁ At PPG/boric acid molar ratio, X ₂ At PPG/maleic anhydride molar ratio, X ₃ Is PPG/sodium metabisulfite molar ratio. From viscosity reduction rate model equationKnowing the linear term X ₁ 、X ₃ Interaction item X ₁ X ₂ 、X ₂ X ₃ And second order term X ₂ ² Has a negative impact on the response. Whereas the linear term X ₂ Interaction item X ₁ X ₃ Second order term X ₁ ² And X ₃ ² Has a positive effect on the response.

Analysis of variance was performed on the fitted regression equation, and the results are shown in Table 7 below. Analysis of variance results show that the model f value is 568.98, indicating that the model is significant. The p-value of each term helps determine the term used in the model equation and indicates which terms the dependent variable is affected by. The p-value is less than 0.05 (p <0.05 A) represents that the model term is significant. In the design of the model, X ₁ 、X ₂ 、X ₃ 、X ₁ X ₂ 、X ₁ X ₃ 、X ₂ X ₃ 、X ₁ ² 、X ₂ ² 、X ₃ ² Is a significant model term. Simultaneous model regression coefficient R ² =0.9969, demonstrating higher equation reliability; signal-to-noise ratio (S/N) = 84.83>4, the signal is sufficient, and from another aspect the model is reliable.

TABLE 7 response surface test results analysis of variance

Examining the shape of the three-dimensional curved surface graph of the response surface, and analyzing X ₁ 、X ₂ 、X ₃ The influence on the viscosity reduction rate is determined by observing the gradient steepness degree of the response surface diagram, and the diagram shows that one parameter is kept unchanged, and the other two parameters have no interaction with each other.

FIG. 2 shows the synthesis ratio X ₁ And the synthesis ratio X ₂ Influence on viscosity reduction Rate, X ₁ Has negative effect on the viscosity reduction rate, and the viscosity reduction rate f is along with X ₁ Is increased and decreased, and X ₂ Has positive effect, and the viscosity reduction rate f is along with X ₂ Is increased by an increase in (a). That is, when the molar amount of PPG is fixed, an increase in the molar amount of boric acid charged and a decrease in the molar amount of maleic anhydride charged have a positive effect on the improvement of the viscosity reduction rate.

FIG. 3 shows the synthesis ratio X ₁ And the synthesis ratio X ₃ The influence on the viscosity reduction rate, both of which have negative influence on the viscosity reduction rate f, the viscosity reduction rate follows X ₁ Is reduced by X ₃ Is increased by decreasing. That is, when the molar amount of PPG is fixed, an increase in the molar amount of boric acid and sodium metabisulfite has a positive effect on the improvement of the viscosity reduction rate.

FIG. 4 shows the synthesis ratio X ₂ And the synthesis ratio X ₃ Is effective in reducing viscosity with X ₂ Increase and increase, X ₃ Is decreased by an increase in (c). That is, when the molar amount of PPG is fixed, the decrease in the molar amount of maleic anhydride and the increase in the molar amount of sodium metabisulfite have a positive effect on the improvement of the viscosity reduction rate.

Stepwise regression is carried out on the obtained regression equation, and the shape of the three-dimensional curved surface graph of the response surface is inspected, so that the optimization parameters of the synthesis ratio are obtained: x is X ₁ Is 0.43, X ₂ Is 1.60, X ₃ 0.81, PPG: boric acid: maleic anhydride: the molar ratio of sodium metabisulfite to synthesis is 1:0.43:1.6:0.81, and the predicted value of the emulsification viscosity reduction rate of the synthetic surfactant under the condition is 96.1%. According to the optimized condition, three batches of parallel experiments are carried out, SYW surfactant is synthesized, and is subjected to thick oil emulsification and viscosity reduction experiments (the result is shown in table 8 below), the average viscosity reduction rate is 95.6%, the average viscosity reduction rate is consistent with the model predicted value of 96.1%, and the reliability of a design model is verified.

Table 8 results of duplicate experiments

The following is the PPG: boric acid: maleic anhydride: the test was carried out with SYW surfactant having a synthetic molar ratio of sodium metabisulfite of 1:0.43:1.6:0.81.

Elemental analysis (for SYW surfactant)

The content of C, H, S, O element in SYW surfactant was measured using a UNICUBE element analyzer manufactured by Elementar, germany, and the O content was measured in O mode to obtain C, H, O, S basic element composition and percentage of each element of SYW surfactant, and the test results are shown in table 9 below.

TABLE 9 SYW surfactant element types and content

SYW the surfactant is prepared from four compounds of PPG, boric acid, maleic anhydride and sodium metabisulfite according to the molar ratio of 1:0.43:1.6:0.81, SYW surfactant elemental analysis showed 56.42 carbon (C%), 8.41 hydrogen (H%) and 1.50 sulfur (S%) and 33.08% oxygen (O%) measured in elemental analyzer O mode. The presence of the S element in the reaction product indicates that the PPG successfully introduces hydrophilic groups through the sulfonation reaction of sodium metabisulfite.

Gel chromatography GPC analysis of SYW surfactant

The molecular weight and the dispersion coefficient of the SYW surfactant were measured using a Waters GPC 1515 gel chromatograph manufactured by Waters company in the united states. The mobile phase solvent is an aqueous phase; the inlet volume was 100.0. Mu.L and the flow rate was 1.00mL/min. Calibration was performed according to polyisoprene standards. The number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (PDI) are recorded. SYW the surfactant was synthesized from 1,3 propanediol polyether, maleic anhydride and sodium metabisulfite, the mobile phase used for gel permeation chromatography relative molecular weight testing was water, and the gel permeation chromatography analysis of SYW surfactant is shown in Table 10 below, with SYW surfactant having a number average molecular weight (Mn) of 2800. The weight average molecular weight (Mw) was 4278 and the polydispersity index (PDI) was 1.52, exceeding 1, meaning that SYW surfactant consisted of heterogeneous molecular chain lengths over a broad molecular mass range, a property important to surfactants.

TABLE 10 SYW surfactant molecular weight and polydispersity index

Fourier infrared (FT-IR) analysis of SYW surfactant

To further investigate the structure of the synthesized SYW surfactant, FT-IR analysis was performed on SYW surfactant using a Nicolet iN10 infrared spectrometer manufactured by Thermo corporation of America. The experimental sample is processed by KBr tabletting method, and the testing wavelength range is 4000-500 cm ^-1 . FT-IR analysis of the synthesized starting material PPG, intermediates S-1, S-2 and SYW is shown in FIG. 5.

3436cm in PPG ^-1 Is characterized in that the peak of the stretching vibration of the hydroxyl O-H at two ends of polyether is 2873cm ^-1 Is methyl-CH in polyether structure ₃ Is 2977cm ^-1 Is methylene-CH ₂ And a stretching vibration characteristic peak of the methine-CH. At 1107cm ^-1 The strong absorption peak appears at the position of the vibration sensor and is characterized by the stretching vibration of ether bond C-O-C. This indicates the presence of methyl-CH in PPG ₃ methylene-CH ₂ And hydroxyl groups, ether bonds in ethylene oxide and propylene oxide chain segments, and the like.

S-1 is the product of esterification reaction of PPG and boric acid, 590cm ^-1 、1378cm ^-1 、1465cm ^-1 Is the stretching vibration peak of B-O bond. This indicates successful introduction of boron oxygen bond B-O in PPG.

S-2 is the product of esterification of S-1 with MA, 1652cm ^-1 There is a-C=C-absorption peak, 1735cm ^-1 ，1257cm ^-1 There is a strong characteristic peak indicating the presence of a c=o, -C-O-C-group in the structure. This suggests that the ester group structure was successfully introduced in S-1.

SYW is the product of sulfonation of S-2 with sodium metabisulfite, 1033cm in SYW ^-1 Absorption peak at the site and tensile vibration of sulfonateRelated to the following.

2873cm of intermediate S-1, S-2 and SYW surfactant ^-1 Is methyl-CH in polyether structure ₃ Is 2977cm ^-1 Is methylene-CH ₂ And the characteristic peak of stretching vibration of the methine-CH, which shows that the basic structure of the PPG is not destroyed in the reaction process while generating a new substance, and the peak of the boron-oxygen bond B-O in SYW still exists. The above results demonstrate the success of introducing various groups after modification on the PPG structure.

Nuclear magnetic resonance spectroscopy of SYW surfactant

To further determine the structure of the SYW surfactant, the raw material PPG, intermediates S-1, S-2 and SYW surfactants were subjected to a Bruker Assnd 600 superconducting Nuclear magnetic resonance apparatus, manufactured by Bruker Corp., germany ¹ H NMR ¹³ C NMR analysis, the sample solvent was DMSO.

¹ The H NMR results are shown in FIG. 6. In PPG, the absorption peak at δ=1.02 to 1.06 is a proton peak of a methyl group on a Propylene Oxide (PO) segment, the methyl group on the segment being linked to a methine group, the peak area defined herein being S _a ，S _a 3.01. The absorption peak at δ=3.32 to 3.66 is the absorption peak of the remaining protons in PPG, including the methylene group on the propylene oxide segment, the hydrogen core in the methine group, the hydrogen core of the methylene group on the ethylene oxide segment, the hydrogen core in the methylene group on the terminal 1,3 propanediol initiator segment and the hydrogen core in the terminal hydroxyl group, the peak area defined herein being S _b ，S _b 11.99. Then n (EO)/n (PO) can be calculated as shown in equation 4.

Thus, n (EO)/n (PO) in the PPG can be calculated to be 2.23:1. The n (EO)/n (PO) calculated by the method has a small error, n (EO)/n (PO) in PPG is 6:4, because the absorption peaks of the initiator and the active hydrogen (hydroxyl) also appear between delta=3.32 and 3.66, and the methylene, the methine and the ethylene oxide chains on the propylene oxide chain segment are formedThe area of the methylene absorption peak on the segment will be substantially larger than that of S _b The calculated n (EO)/n (PO) values are larger because of the small area. According to ¹ The H NMR spectrum calculates EO content in polyether using propylene glycol as initiator, and the calculation method is shown in formula 5.

The molecular weight M of the 1, 3-propanediol polyether PPG is 2700, the number of repeating segments M of EO and the number of repeating segments n of PO can be calculated to obtain that M is about 19 and n is about 7, and since the polyether is not a uniform compound, it is impossible to generate a compound with the same degree of polymerization in the synthesis process, and the calculation results of the values of M and n have a small error ^[100,101] . In S-1, S-2, syw, no new peak appears, but the absorption peak intensities at δ=3.34 and δ=1.04 increase, and it can be inferred that there is progress of the subsequent reaction.

¹³ The C NMR results are shown in FIG. 7. In the case of the PPG of a fiber, ¹³ the C NMR spectrum can be divided into six regions. 1. δ=17.54 is the absorption peak of the methyl carbon of the propylene oxide segment of the polyether molecule; 2.δ= 60.66 is the absorption peak of the terminal methine carbon; 3.δ= 68.34 is the absorption peak of methylene carbon in the polyether where the ethylene oxide segment is linked to the propylene oxide segment; 4.δ=70.2 to 70.6 is the absorption peak of methylene carbon on the ethylene oxide segment; 5. δ=72.7 to 73.0 is the absorption peak of methylene carbon on the propylene oxide segment; 6. δ= 74.91 is the absorption peak of propylene oxide methylene and methine carbon.

Because the molecular weight of the new groups introduced by the reaction is small and the type of the introduced C-containing groups is hardly changed, the position shift of the C absorption peak during the reaction is not seen in FIG. 7, and the peaks of the six regions are normalized by integration in order to clarify the addition of the new C groups, and the change of the C absorption peak during the reaction is analyzed as shown in Table 11 below. In the S-1, S-2, SYW surfactant, the absorption peak of methylene carbon on the epoxy group was reduced, which suggests that a new carbon-containing group was generated by the reaction, resulting in a reduced area ratio of the absorption peak of C on the epoxy group, indicating that maleic anhydride, pyrosulfurous acid, was successfully involved in the reaction.

TABLE 11 raw material PPG, synthetic stage products S-1, S-2 and SYW surfactant C absorption peak area ratio

The value of n (EO)/n (PO) in PPG can also be calculated from the absorption peak areas of the different carbon types. The area of the absorption peak of delta=16.68 to 17.93 is denoted as S _c The absorption peak area of delta=64.54 to 75.38 is denoted as S _c The calculation method is shown in formula 6.

Thus, it can be calculated that n (EO)/n (PO) in the PPG is 2.07:1, and ¹ the results of the H NMR calculations do not differ much.

X-ray photoelectron spectroscopy (XPS) analysis of SYW surfactant

To further determine the structure of the SYW surfactant, the SYW surfactant was subjected to spectroscopic analysis using Kalpha X-ray photoelectron spectroscopy, manufactured by Thermo corporation, usa.

As shown in fig. 8, the surface of the SYW surfactant mainly contains C, O elements and a small amount of B, S elements. Semi-quantitative analysis of the surface elements of SYW surfactant is shown in table 12 below. From the scan results, the surface of the final product SYW surfactant had a plurality of elements, and the relative content of carbon elements was up to 69.18%, indicating that the carbon structure in the SYW surfactant was the main part of the product. The relative content of oxygen element is also higher, which indicates that more oxygen-containing functional groups may exist in the product, and the existence of sulfur element is caused by the sulfonation reaction of sodium metabisulfite added in the process of synthesizing the product. Similarly, boric acid and raw material PPG are added to generate esterification reaction in the process of synthesizing the product, so that a small amount of B element exists on the surface of the product.

TABLE 12 semi-quantitative analysis of surface elements of SYW surfactants

From table 12, it was found that the atom percentage of B atoms in the semi-quantitative analysis was 0.61%, and the atom content was normalized based on the atom percentage of S, B atoms in the semi-quantitative analysis and the atom percentage of S atoms in the elemental analysis, to calculate that the atom content of B atoms in the SYW surfactant was 0.8%. Thus we obtained the content of each atom in SYW surfactant, and combined with GPC analysis, calculated that SYW surfactant molecule has a formula of C ₁₃₁ H ₂₃₅ S ₁ O ₅₈ B ₂ 。

The peak and data fitting treatments were performed on the C, O, S and B four elements of the SYW surfactant surface using Avantage peak splitting software. Narrow scanning is performed on C1s to obtain a C1s high-resolution XPS spectrum, as shown in FIG. 9. As can be seen from the figure, the carbon element in the SYW surfactant has four different chemical environments, namely C-C/C-H and-CH respectively ₂ -/C-S、C-O/C-SO ₃ ^- And o=c-O, with binding energies 284.1eV, 284.5eV, 286.9eV, and 288.2eV, respectively. C-C and C-H species in the hydrocarbon backbone of the polymer chain having a binding energy of 284.1 eV; peak assignment at 285.8eV to-CH of backbone ₂ -and C-S species; the two peaks at 286.9eV and 288.2eV are respectively attributed to C-O/C-SO in the product ₃ ^- And o=c-O species.

The narrow sweep of O1s is carried out to obtain an O1s high-resolution XPS spectrogram, and peak separation and data fitting treatment are carried out on the O1s high-resolution XPS spectrogram, as shown in fig. 10, the peak separation fitting result shows that oxygen elements in the SYW surfactant can be subjected to peak separation fitting into three peaks, and the binding energy of the oxygen elements is 530.8eV, 531.6eV and 532.6eV respectively, namely three chemical environments exist for the oxygen elements. Binding energy centered at 530.8eV is attributed to c=o/S-O; binding energy centered around 531.6eV is attributed to o=c-O; binding energy centered on 532.6eV is ascribed to-CH ₂ -O-CH ₂ In (C-O-C) and B-O species. XPS analysis result of C and O elements and precursor FourierAnalysis of the leaf infrared spectrum and nuclear magnetic resonance spectrum are consistent.

The S2 p is subjected to narrow scanning to obtain an S2 p high-resolution XPS spectrogram, and peak separation and data fitting treatment are carried out on the S2 p high-resolution XPS spectrogram, as shown in fig. 11, it can be seen from the figure that the sulfur element in the SYW surfactant can be fitted into two peaks, and two binding energies taking 166.8eV and 168.0eV as the center can be respectively attributed to C-S and C-SO ₃ ^- S species, which is due to sulfonation reaction with sodium metabisulfite during the synthesis of SYW surfactant, shows that the sulfur element in the treated end product is mainly SO ₃ ^- In the form of a salt. Consistent with the analysis of fourier infrared spectra previously described.

B1s is subjected to narrow scanning to obtain a B1s high-resolution XPS spectrum, peak separation and data fitting treatment are carried out on the B1s high-resolution XPS spectrum, and as shown in FIG. 12, the boron element in the SYW surfactant can be subjected to peak separation and fitting into three peaks, and the binding energy of the boron element is 189.7eV, 191.4eV and 192.8eV respectively ^[106] . Wherein, two binding energies centered around 191.4eV and 192.8eV can be respectively attributed to B-O bond in boric acid and B-O bond in borate, and binding energy centered around 189.7eV can be attributed to trace amount of B dissolved in the final product.

TABLE 13 XPS peak positions for SYW surfactant surface elements

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In conclusion, the molecular formula of the obtained target product SYW surfactant is C ₁₃₁ H ₂₃₅ S ₁ O ₅₈ B ₂ The structural formula is shown in the following formula 7.

Example 1 Effect of different surfactants on the emulsion viscosity reduction Rate of thickened oil

Emulsification viscosity reduction refers to the formation of an oil-in-water emulsion in which the crude oil becomes the dispersed phase and the water becomes the continuous phase under the action of a suitable surfactant. The formation of the O/W type oil-water emulsion significantly reduces the viscosity. Therefore, determining a proper emulsifier is a technical key of the emulsification and viscosity reduction of the thick oil.

The viscosity of the Xinjiang thick oil is 520 mPa.s at 70 ℃, the oil-water volume ratio is 1:1, the concentration of the surfactant is 1500mg/L, and the emulsification temperature is 70 ℃ for experiments. The anionic-nonionic surfactant SYW synthesized above and the nonionic surfactants PPG, intermediates S-1 and S-2 synthesized as raw materials were used as emulsifying viscosity reducer for research, and sodium dodecyl benzene sulfonate SDBS, a typical anionic surfactant, was introduced as a control, and the emulsifying viscosity reduction phenomenon is shown in the following table 14.

TABLE 14 surfactant emulsification phenomena

The emulsification and viscosity reduction effects are shown in FIG. 13, and the corresponding data are shown in Table 15 below.

Table 15 emulsion viscosity reducing Effect of surfactants

As is clear from tables 14 to 15 and fig. 13, the emulsifying effect of the different kinds of surfactants on the thick oil was different. The viscosity reduction rate of SDBS is 76.7%, the viscosity reduction rate of PPG is 87.3%, the viscosity reduction rates of S-1 and S-2 are 94.0%, 95.0% and the viscosity reduction rate of SYW is 97.3%. SDBS mainly plays a role in emulsification, but has poor dispersibility and stability in thick oil emulsification, rapid layering and low emulsification and viscosity reduction rate. The emulsification effects of PPG, S-1 and S-2 on the thick oil are different, and the emulsification effects of S-1 and S-2 on the thick oil are relatively good. SYW surfactant has relatively high emulsifying and viscosity reducing rate and good emulsifying property and dispersing property for thick oil.

Example 2 Effect of SYW surfactant concentration on viscosity reduction Rate of thickened oil emulsions

The concentration of the emulsifying viscosity reducer is an important factor influencing the emulsifying viscosity reducing effect, and the viscosity of the thick oil is 520 mPa.s at 70 ℃. Preparing SYW surfactant water solutions (200 mg/L-2500 mg/L) with different concentrations, and performing emulsification viscosity reduction experiments under the conditions that the oil-water volume ratio is 1:1 and the emulsification temperature is 70 ℃, wherein the results are shown in figure 14, and the corresponding data are shown in the following table 16.

Surface 16 emulsion viscosity reducing effect of surfactant

As can be seen from fig. 14 and table 16, the viscosity of the emulsion formed by the thickened oil is greater when the surfactant concentration is small. As the concentration of the SYW surfactant increases, the viscosity is reduced, the viscosity reduction rate is increased, and when the concentration reaches 1000mg/L, the viscosity reduction rate can reach 95.7%. When the concentration of the SYW surfactant reaches 1500mg/L, the viscosity reduction rate can reach 97.3 percent. As the concentration of SYW surfactant increases, the viscosity of the emulsion decreases. This is because the thickened oil contains asphaltenes, colloid, petroleum acid and other natural surfactants, which can form a W/O emulsion between crude oil and water. After the anionic-nonionic surfactant SYW is added, the SYW has strong surface activity, can be adsorbed to an oil-water interface to replace part of asphaltene and colloid in crude oil, so that an oil-water emulsion interfacial film formed by the SYW surfactant and the crude oil natural surfactant is formed, and the thickened oil emulsion is converted from water-in-oil type to oil-in-water type, so that the viscosity of the oil-water emulsion is reduced. As SYW concentration increases, displaced asphaltenes and gums increase, and the number of SYW adsorbed to the oil-water interface increases, thereby increasing the viscosity reduction rate. When the SYW concentration was increased to some extent, the viscosity of the emulsion was not substantially changed, probably because SYW adsorbed balance at the oil-water interface, and no more asphaltenes and gum were displaced, so the viscosity was not substantially changed.

Example 3 Effect of SYW surfactant temperature on viscosity reduction Rate of thickened oil emulsions

Viscosity is an important parameter for characterizing the physical properties of oil, and is particularly important for thick oil, the viscosity of Xinjiang thick oil at different temperatures is measured by using a viscometer (see table 17 below), and a thick oil viscosity-temperature curve is drawn as shown in fig. 15.

Table 17 viscosity of thickened oil at different temperatures

As can be seen from fig. 15, the viscosity of the thick oil decreases with the increase of temperature, and the viscosity-temperature curve equation of the Xinjiang crude oil is obtained by fitting the data according to the experimental parameters, as shown in formula 8:

lnμ=19.35-2.83 lnt (formula 8)

Wherein: viscosity of eta-oil mPa.s; t-temperature of oil product.

By the formula, the viscosity of the thick oil at different temperatures can be calculated. From the results, the fitting effect is good, R ² The viscosity-temperature performance of the Xinjiang thick oil is 0.989, and can be well reflected.

The influence of SYW surfactant on the viscosity reduction effect of the thick oil emulsion at different emulsification temperatures is examined, and the temperature is examined to be 40-80 ℃ under the limitation of experimental conditions. The emulsification and viscosity reduction experiment is carried out under the conditions that the volume ratio of oil to water is 1:1 and the concentration of SYW surfactant is 1500mg/L, the experimental result is shown in FIG. 16, and the corresponding data are shown in the following table 18.

TABLE 18 influence of emulsification temperature on viscosity reduction of thickened emulsions

As can be seen from FIG. 16 and Table 18, after addition of SYW, the emulsion viscosity was between 23 mPas and 13 mPas at a temperature ranging from 40℃to 80 ℃. This shows that SYW thick oil has a relatively stable viscosity reducing effect in the temperature range under investigation. The thick oil emulsion is an O/W type emulsion, the water is a continuous phase, the viscosity of the emulsion is mainly determined by the water, the viscosity of the water is low, and the viscosity of the water is not affected by the temperature basically, so the viscosity of the emulsion is low, and the viscosity change is not obvious.

Example 4 Effect of SYW surfactant concentration on the Water cut of thickened emulsions

The emulsifying viscosity reducer applied to the thick oil not only requires the stable emulsion formed in the flowing process, but also requires the quick layering of the viscosity reducer in a standing state, so that the subsequent demulsification and dehydration processes of the crude oil are facilitated. The effect of the surfactant concentration on the water splitting effect of the thickened oil emulsion was thus examined. And (3) standing the prepared thick oil emulsion in a constant-temperature water bath kettle under the condition that the oil-water volume ratio is 1:1 and the emulsification temperature is 70 ℃, recording the water distribution amount once every 30 minutes, wherein the experimental result is shown in figure 17, and the corresponding data are shown in the following table 19.

Table 19 thickened oil emulsion water splitting effect of surfactants

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As can be seen from FIGS. 17 and Table 19, at SYW surfactant concentrations less than 500mg/L, a water cut of 90% was achieved for 0.5h, indicating that adequate emulsification of the thickened oil was not possible. Under the condition of 1500mg/L concentration, the water division rate of the emulsion of SYW surfactant for 0.5h is 67%, after standing for 1h, the water division rate is 79%, and after standing for 1.5h, the water division rate reaches 88%. Under the condition of 2500mg/L concentration, the water division rate of the emulsion of the SYW surfactant is 35% in 0.5h, and the water division rate is only 52% after the emulsion is left for 1.5 h. Experimental results show that when the dosage of the SYW surfactant is too small, the thickened oil cannot be fully emulsified, and is consistent with the experimental results of the viscosity reduction effect in 3.2.2, as the concentration of SYW is increased, the adsorption quantity of SYW on an oil-water interface is increased, the stability is enhanced, and when the dosage of the SYW surfactant is too large, the thickened oil emulsion is too stable, so that demulsification and dehydration in the later period of thickened oil exploitation are not facilitated. When the dosage is 1500mg/L, the SYW surfactant has strong emulsifying capacity, so that the water-containing thickened oil can form stable O/W emulsion, and the emulsion can be quickly broken and dehydrated, thereby meeting the field requirement.

In a word, the novel boron-containing anionic-nonionic surfactant is prepared by taking 1, 3-propanediol polyether as a raw material through esterification with boric acid, maleic anhydride and sulfonation reaction of sodium metabisulfite, and the raw material molar ratio in the reaction process is determined by using a response surface curve method. The results show that the optimal synthesis ratio of the SYW surfactant is as follows: PPG: boric acid: maleic anhydride: sodium metabisulfite is 1:0.43:1.6:0.81. The optimized synthesized SYW surfactant is subjected to element analysis, GPC analysis, FT-IR analysis, ¹ H NMR analysis, ¹³ The results of the C NMR analysis and XPS analysis show that the experiment successfully introduces boron-oxygen bond B-O and sulfonate group C-SO into the raw material PPG ₃ ^- The target product SYW surfactant is obtained by waiting for hydrophilic groups. The SYW surfactant is used for examining the emulsification and viscosity reduction effects of the Xinjiang thick oil, and the results show that: at the emulsification temperature of 70 ℃, aiming at the thick oil emulsion with the water content of 50 percent, when the input amount of SYW is 1500mg/L, the viscosity reduction rate can reach 97.3 percent, and the water division rate after 1 hour is 79 percent, so that the O/W type emulsion with higher stability can be formed, and the emulsion can be quickly broken, and the subsequent treatment is not influenced.

In order to further improve the emulsification and viscosity reduction effects of the surfactant on the thick oil, the SYW surfactant and other reagents are compounded. Oleic acid is used as a surfactant and is easy to degrade, one end of the structure of the oleic acid is provided with a polar hydrophilic group, one end of the structure is provided with a nonpolar hydrophobic group, the polar head enables the surfactant formed by the oleic acid to be soluble in water and polar solvents, the hydrophobic tail enables the surfactant formed by the oleic acid to be soluble in nonpolar solvents, the oleic acid can change the physicochemical property of an oil-water interface, the viscosity of crude oil is reduced, the viscosity of water is increased, and the flow of the crude oil in a porous medium is facilitated. Meanwhile, research proves that the addition of alkali can improve the recovery ratio of crude oil, but the technology has some problems, and inorganic alkali such as NaOH and Na ₂ CO ₃ It is easy to cause pipeline scaling. BergeStudies of r and Lee show that the organic base does not react with Ca ²⁺ 、Mg ²⁺ And react to form a precipitate. In addition, the organic base also has the effect of reducing the interfacial tension between oil and water. Therefore, the invention selects organic alkali Ethanolamine (ETA) as medium alkali, and has emulsification and dispersion effects. Therefore, the synthesized SYW surfactant, oleic acid and ethanolamine are compounded to form SYG compound surfactant, and the compound proportion is obtained by optimizing a response surface curve method.

SYG compound surfactant formulation optimization

The Design of Box-Behnken experiment is adopted, and the Design-expert.V8.0.6.1r software is used for optimizing the formula proportion by a response surface method. SYW surfactant, oleic acid and ethanolamine concentration ratio are important parameters affecting the emulsification and viscosity reduction rate of the thick oil. The SYW surfactant concentration (A), the ethanolamine concentration (B) and the oleic acid concentration (C) are selected as independent variables of the formula of the compound surfactant, and the viscosity reduction rate (f) of the compound surfactant to the thick oil emulsion is selected as a response variable. Response surface analysis experiments were performed at 17 test points under three factors A, B, C and three levels. The evaluation conditions of the SYG compound surfactant applied to the viscosity reduction effect of the thickened oil are as follows: the emulsification temperature is 70 ℃, and the oil-water ratio is 1:1. For the determined independent variables, the ranges for each variable used in the experimental study are shown in table 20 below.

Table 20 Complex surfactant formulation optimization Box-Behnken test factors and level

The experimental results and analysis are shown in table 21 below.

Table 21 results of Box-Behnken experiment for optimizing formulation of surfactant

In experimental study, a second order polynomial model equation is derived from the process variables of the design matrix. Based on Design Expert8.0.6 data analysis software, predicting the response of the viscosity reduction rate f according to experimental data to obtain a quadratic polynomial equation in the formula 9

Y＝99.21+0.58*A+1.20*B+0.61*C-1.43A*B+0.37A*C+0.54B*C-1.32*A ² -2.37*B ² -1.82*C ² (9)

Wherein Y is predicted response (viscosity reduction rate f), A is SYW surfactant concentration, B is ethanolamine concentration, and C is oleic acid concentration, and the linear term A, B, C and the interaction terms AC and BC have positive influence on response as known by a viscosity reduction rate model equation. And interaction term AB, second order term A ² 、B ² And C ² Has a negative effect on the response.

Regression analysis is further performed on the model and the regression coefficient, and analysis results of the viscosity reduction rate model and the regression coefficient are shown in Table 22. Analysis of variance results show that the model f value is 58.29, indicating that the model is significant. Regression model P<0.0001 (extremely remarkable), A, B, C, AB, BC, A in the present model design ² 、B ² And C ² Is a significant model term. As can be seen by analyzing the relevant data, the primary term A, B, C has a significant effect on the viscosity reduction rate (P <0.01). The main effect relation of each factor is analyzed as follows: a is that>B>C, SYW surfactant concentration>Concentration of ethanolamine>Oleic acid concentration. Its quadratic interaction BC has a significant effect on viscosity reduction rate (P<0.01 The quadratic interaction AB has a significant effect on the viscosity reduction rate (P<0.05 The effect of AC on viscosity reduction rate was insignificant (P>0.05). The mismatch term p= 0.6634>0.05 (not significant), the model fitting degree is good, and the corresponding regression value of the regression equation can be predicted. Model regression coefficient R ² = 0.9699, the equation reliability is higher. Signal-to-noise ratio (S/N) =20.45>4, the signal is sufficient, and from another aspect the model is reliable.

Table 22 viscosity reduction rate effect model and regression analysis results of regression coefficients

Stepwise regression is carried out on the obtained regression equation, and the shape of the three-dimensional curved surface graph of the response surface is inspected, so that the ratio of the SYG compound surfactant after optimization is obtained: SYW the surfactant concentration is 1.568, the ethanolamine concentration is 0.370, the oleic acid concentration is 0.600, and the viscosity reduction rate of the oil-water emulsion under the condition is 99.4 percent. Considering that the Xinjiang thick oil used in the invention is a high-acid crude oil, the input amount of ethanolamine is increased in the formula, the conditions are modified to SYW surfactant concentration of 1500mg/L, ethanolamine concentration of 500mg/L and oleic acid concentration of 500mg/L, 3 parallel experiments are carried out under the optimized conditions, the parallel experiment results are shown in the following table 23, the average viscosity reduction rate is 99.3 percent, and the average viscosity reduction rate is not much different from the predicted viscosity reduction rate of 99.4 percent, so that good correlation between the predicted value and the experimental value is confirmed. Therefore, the optimized proportion SYW of the SYG compound surfactant is 3:1:1 of ethanolamine to oleic acid.

Table 23 results of duplicate experiments

The test was performed with SYG compound surfactant having an optimized ratio of SYW:ethanolamine to oleic acid of 3:1:1. However, it should be understood that the SYG compound surfactants in the proportions listed in Table 21 above all demonstrate good emulsifying and viscosity reducing effects on heavy oil.

Example 5 Effect of SYG surfactant concentration on viscosity reduction Rate of heavy oil emulsions

SYG compound surfactant aqueous solutions (500 mg/L-2500 mg/L) with different concentrations are prepared, and an emulsification viscosity reduction experiment is carried out under the condition that the oil-water volume ratio is 1:1 and the emulsification temperature is 70 ℃, the result is shown in figure 18, and corresponding data are shown in the following table 24.

Table 24 viscosity reduction Rate of SYG Complex surfactant for thickened oil emulsion

When the dosage of SYG is less than 500mg/L, the thick oil cannot be well emulsified, and the oil-water delamination is faster after the stirring is finished. As the dosage increases, the thickened oil emulsion contains filament-like oil droplets. When the dosage of SYG is more than 1500mg/L, a thick oil emulsion with even dispersion can be obtained. As can be seen from FIG. 18 and Table 24, when the dosage of SYG is less than 500mg/L, the viscosity of the oil-water emulsion is large; along with the increase of the dosage, SYW and oleic acid surfactants are adsorbed to an oil-water interface to replace the increase of the quantity of colloid asphaltenes in crude oil, acidic substances in the crude oil react with ethanolamine rapidly, surface active substances are generated in situ on the interface, and a compact adsorption film of petroleum acid and petroleum acid soap is formed on the interface, so that the thickened oil emulsion is converted from water-in-oil type into oil-in-water type, and the viscosity of the oil-water emulsion is reduced. Comparing with the graph 3.12, it is obvious that the content of the surfactant required by the emulsified thick oil after the compounding is reduced, when the SYG dosage is 1500mg/L, the viscosity reduction rate reaches 98.6%, and the adding amount of the SYW surfactant is only 900mg/L. This demonstrates that SYW surfactant, ethanolamine and oleic acid produce synergistic effect and raise the emulsifying capacity of the viscosity reducer.

Example 6 Effect of Water content of SYG Complex surfactant on the emulsification and viscosity reduction of heavy oil

The water content of the thickened oil is also one of the key factors affecting the viscosity of the thickened oil. The experiment is carried out at 70 ℃ and 1500mg/L SYG dosage, the influence of 20% -80% of water content of the thick oil on viscosity reduction effect is examined, the results are shown in FIG. 19 and FIG. 20, and the corresponding data are shown in the following Table 25.

Table 25 influence of water content before and after addition of the additive on emulsification and viscosity reduction of heavy oil

19-20 and Table 25 show that when SYG is not added with the increase of the water content, the viscosity of the Xinjiang thick oil emulsion is highest between 40% and 50% of the water content, and when the water content is lower than the highest point, the viscosity of the water-containing thick oil is increased with the increase of the water content, and the crude oil contains a natural water-in-oil type emulsifier, so that the emulsion is promoted to form water-in-oil type, and the viscosity of the crude oil is increased; above this water content, the viscosity of the aqueous thickened oil decreases as the water content increases. When SYG is added, the viscosity is hardly changed at 20%, because according to the close packing theory, only a stable water-in-oil emulsion is formed at a water content of less than 25.98%, the oil is a continuous phase, the water is a dispersed phase, and the water drops of the dispersed phase are spaced apart and have weak interaction. When the water content is more than 30%, the viscosity of the thick oil emulsion to which SYG is added is significantly reduced, which means that SYG is added to convert the water-in-oil emulsion into an oil-in-water emulsion at a lower water content. When the water content is more than 74.02%, the emulsion can form stable oil-in-water emulsion, the liquid drops are deformed, the viscosity is reduced, and the viscosity before and after adding the additive is not greatly changed, and the viscosity of the oil-in-water emulsion mainly depends on the viscosity of the water phase. Meanwhile, the SYG has good effects on the emulsification and viscosity reduction of the thick oil in a very wide oil-water ratio range, the SYG can reduce the viscosity of the thick oil emulsion from 526 mPa.s to below 1.35 mPa.s, and the viscosity reduction rate can reach more than 90% by forming O/W type thick oil emulsion.

Example 7 Effect of temperature of SYG formulation surfactant on viscosity reduction Rate of heavy oil emulsions

Under the conditions that the volume ratio of oil to water is 1:1 and the concentration of SYG surfactant is 1500mg/L, the influence of temperature (40-80 ℃) on the emulsification viscosity reduction effect is examined, the experimental result is shown in figure 21, and the data are shown in the following table 26.

Table 26SYG compound surfactant for emulsifying and viscosity reducing of thick oil at different emulsifying temperatures

As can be seen from FIGS. 21 and 26, SYG can reduce the viscosity of the thick oil emulsion to a low level in the temperature range of 40-80. The viscosity of the thick oil emulsion does not change much in this temperature range, because the thick oil emulsion is an oil-in-water emulsion after SYG is added, water is a continuous phase, the viscosity is mainly dependent on the viscosity of water, the viscosity of water is relatively small, and the viscosity of water changes little due to temperature, so that the overall viscosity changes little during the experiment.

EXAMPLE 8 investigation of the viscosity reducing Effect of SYG on different types of heavy oil emulsions

The oil samples included, in addition to the Xinjiang thick oil 1 mentioned in Table 4 above, the oil samples whose property data are shown in tables 27 to 31 below.

Table 27 heavy oil 2

Table 28 thickened oil 3

Table 29 thickened oil 4

Table 30 thickened oil 5

Table 31 thickened oil 6

SYW surfactant concentration is 1500mg/L, ethanolamine concentration is 500mg/L, oleic acid concentration is 500mg/L, emulsification temperature is 70 ℃, oil-water ratio is 1:1, and corresponding data results are shown in Table 32 below.

Table 32 viscosity reducing effect on different types of heavy oil emulsions

The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications can be made to the above-described embodiment of the present invention. All simple, equivalent changes and modifications made in accordance with the claims and the specification of this application fall within the scope of the patent claims. The present invention is not described in detail in the conventional art.

Claims

1. The application of the surfactant in the emulsification and viscosity reduction of the thick oil is characterized in that the surfactant is a boron-containing surfactant, and the structural formula of the surfactant is shown as follows:

wherein m is 17-21, n is 5-9.

2. Use according to claim 1, wherein the boron-containing surfactant is dissolved in water to form an emulsion water phase, the thickened oil and the emulsion water phase are mixed to obtain a thickened oil emulsion, and the thickened oil emulsion is emulsified to form an oil-in-water emulsion to reduce the viscosity of the thickened oil.

3. Use according to claim 2, characterized in that the concentration of the boron-containing surfactant in the thick oil emulsion is between 1000mg/L and 2500 mg/L.

4. Use according to claim 3, characterized in that the concentration of the boron-containing surfactant in the thick oil emulsion is between 1000mg/L and 1500 mg/L.

5. The use according to claim 1, wherein the boron-containing surfactant is formulated with oleic acid and ethanolamine to form a formulated surfactant, the formulated surfactant is dissolved in water to form an emulsion water phase, the thickened oil and the emulsion water phase are mixed to form a thickened oil emulsion, and the thickened oil emulsion is emulsified to form an oil-in-water emulsion to reduce the viscosity of the thickened oil.

6. The method according to claim 5, wherein the ratio of the boron-containing surfactant to the ethanolamine to the oleic acid is 3:1:1.

7. Use according to claim 5, characterized in that the concentration of the built surfactant in the thickened oil emulsion is between 1000mg/L and 2500 mg/L.

8. Use according to claim 2 or 5, characterized in that the emulsification temperature is between 40 ℃ and 80 ℃.

9. Use according to claim 2 or 5, characterized in that the water content of the thickened oil emulsion is between 30% and 80%.

10. Use according to claim 2 or 5, characterized in that the viscosity of the thickened oil is between 500-30000 mPa-s.