Temperature-resistant salt-resistant thickened oil viscosity-reducing oil-displacing agent and preparation method thereof

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a temperature-resistant salt-resistant thickened oil viscosity-reducing oil-displacing agent and a preparation method thereof. The preparation method comprises the following steps: under the condition of 80 to 90 DEG C, 4, 4 '-difluorobenzophenone and ammonium formate are subjected to a Leuckart-Wallach reaction in a first solvent; secondly, under the action of a catalyst, in a second solvent in an oxygen-isolated environment and under the conditions of high temperature and high pressure, a reaction product and ethylene oxide are subjected to an etherification reaction; the viscosity-reducing oil-displacing agent has the advantages of simple synthesis process, low dosage and good effect.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a temperature-resistant and salt-resistant heavy oil viscosity-reducing oil-displacing agent and a preparation method thereof. Background Art

[0002] Improving the recovery rate of old oil fields through new methods and technologies is an important means to increase oil and gas production and ensure national energy security. The recovery rate enhancement technology based on chemical flooding has made important contributions to the stable production and increase of oil fields in my country over the past 30 years. Among them, the chemical flooding of Daqing Oilfield has produced a total of 260 million tons of oil, and the chemical flooding of Shengli Oilfield has increased crude oil production by 34.58 million tons. At present, chemical flooding technology has achieved full coverage of Class I and Class II oil reservoirs, but there is still a lack of efficient oil displacement agents for Class III and Class IV high-temperature and high-salt heavy oil reservoirs. This is because the oil displacement agents used in Class I and Class II oil reservoirs will undergo structural changes in high-temperature and high-salt environments, and the oil displacement performance will be greatly reduced. For this reason, the development of temperature-resistant and salt-resistant heavy oil viscosity-reducing oil displacement agents is of great significance for improving the recovery rate of Class III and Class IV heavy oil reservoirs.

[0003] Crude oil in high-temperature and high-salinity heavy oil reservoirs has a high proportion of colloids and asphaltene, and has the characteristics of high viscosity and large oil-water mobility ratio, which makes water drive prone to sudden advance. In order to effectively inhibit the sudden advance of water drive, the most commonly used method is to reduce the mobility ratio by reducing the viscosity of crude oil through viscosity reducers. Viscosity reducers include water-soluble viscosity reducers and oil-soluble viscosity reducers. Among them, water-soluble viscosity reducers have the advantages of low cost and wide application range, and are the main research direction of heavy oil viscosity reducers.

[0004] CN20181104172.6 discloses a water-soluble heavy oil viscosity reducer composed of humic acid polycondensate and N-dialkyl N'N-dialkyl dimethyl pyridinium salt. This type of viscosity reducer has good interface participation ability and viscosity reduction effect. It enters between the colloid and asphaltene sheet molecules by strong penetration and dispersion, partially dismantles the aggregates formed by overlapping planes, and forms irregularly stacked and loosely structured aggregates formed by colloid, asphaltene molecules and viscosity reducer molecules, thereby reducing the viscosity of heavy oil. The heavy oil viscosity reducer of the invention is suitable for temperatures ranging from 40 to 80°C, but in fact the temperature of high-temperature and high-salinity reservoirs mostly exceeds 85°C, so the invention is limited in the scope of applicable reservoirs. In addition, the invention uses quaternary ammonium salt cationic surfactants, which are severely adsorbed in the reservoir, causing chromatographic separation and affecting oil displacement performance.

[0005] CN20111044108.8 discloses a fluorine-containing amphiphilic polymer crude oil viscosity reducer, which is prepared by dissolving a water-soluble monomer and a perfluoroalkyl acrylate monomer in water to obtain an aqueous phase solution, and then adding cyclohexane, an emulsifier and an initiator to obtain an oil-in-water emulsion by stirring. The oil-in-water emulsion is obtained by adjusting the pH value of the oil-in-water emulsion to alkaline and then performing inverse emulsion polymerization. The viscosity reduction test results show that the agent has a good emulsifying effect on heavy oil, and the viscosity reduction rate is ≥90%. The heavy oil viscosity reducer prepared by the invention is a type of composite product. When performing well group displacement, there is a chromatographic separation problem caused by adsorption, which affects the oil displacement effect. Summary of the invention

[0006] Aiming at the problem of poor adaptability of viscosity reducers to reservoir environments encountered in current heavy oil production, the present invention provides a temperature-resistant and salt-resistant heavy oil viscosity reducer and a preparation method thereof. The viscosity reducer has the advantages of simple synthesis process, low dosage and good effect.

[0007] Therefore, in order to achieve the above-mentioned purpose, on the one hand, the present invention discloses a temperature-resistant and salt-resistant heavy oil viscosity-reducing oil displacement agent, and the molecular structure of the oil displacement agent is as follows:

[0008]

[0009] Where: m = 2-50;

[0010] n=5-100.

[0011] On the other hand, the present invention provides a method for preparing the above-mentioned temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent, the preparation method comprising: at 80-90° C., 4,4'-difluorobenzophenone and ammonium formate undergo a Leuckart-Wallach reaction in a first solvent; secondly, under the action of a catalyst, in a second solvent, in an oxygen-isolated environment, and under high temperature and high pressure conditions, the reaction product undergoes an etherification reaction with ethylene oxide.

[0012] The third object of the present invention is to disclose the application of the above-mentioned temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent in the development of heavy oil reservoirs.

[0013] The heat-resistant and salt-resistant heavy oil viscosity-reducing and oil-displacing agent of the present invention belongs to a special composite surfactant containing fluorine, and two polyether groups belong to nonionic hydrophilic groups, and two fluorophenyl groups belong to lipophilic groups. The structure of the present invention does not contain anionic hydrophilic groups, so it has good salt resistance. In view of the problem of poor temperature resistance of the polyether group, a strong polar fluorophenyl group is introduced to weaken the problem of polyether precipitation caused by hydrogen bonding under high temperature environment, and greatly improve the temperature resistance of the molecule. The present invention has higher surface / interface activity than conventional heavy oil viscosity reducers, and lower critical micelle concentration, so the dosage when used is lower. Fluorophenyl has good lipophilic properties, can spontaneously insert into the stacking structure of colloid and asphaltene of crude oil, destroy the π-π conjugation effect of colloid asphaltene, weaken the aggregation force of colloid and asphaltene, and is easy to combine with large aromatic ring compounds in crude oil, and can more easily peel off the colloid and asphaltene adsorbed on the oil-water interface of W / O type heavy oil emulsion, and convert the W / O emulsion into O / W emulsion, thereby greatly reducing the viscosity of the emulsion. The polyether group has strong hydrophilicity and can easily form a continuous water film as the external phase. In addition, the polyether group has good flexibility and can easily entangle with crude oil, thereby enabling the entire oil-water system to form a stable O / W emulsion under low power, greatly improving the seepage capacity of crude oil and the efficiency of heavy oil water flooding.

[0014] Compared with the prior art, the present invention has the following beneficial effects and advantages:

[0015] (1) The heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent of the present invention has the characteristics of wide raw material sources, simple synthesis process, clean and pollution-free process;

[0016] (2) The heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent of the present invention has good heat-resistant and salt-resistant properties, with a temperature resistance of up to 210°C, a salt resistance concentration of up to 120,000 mg / L, and a calcium and magnesium ion resistance concentration of up to 2000 mg / L;

[0017] (3) The heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent of the present invention has good surface / interface properties, and the surface tension is reduced to below 27 mN / m, and the interfacial tension is reduced to 6.5×10 -2 Below mN / m;

[0018] (4) The heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent of the present invention has the characteristics of high activity and can reduce the viscosity of heavy oil by more than 96% at a concentration of 500 mg / L;

[0019] (5) The temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent of the present invention can significantly improve the wettability of the reservoir and reduce the contact angle of the core model from 89.6 degrees to 16.5 degrees. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The contact angle variation diagram of the viscosity reducing oil displacement agent B5 of the present invention and the rock model treated with petroleum sulfonate of Shengli Chemical Plant. DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] According to a first aspect of the present invention, the present invention discloses a temperature-resistant and salt-resistant heavy oil viscosity-reducing oil displacement agent, the molecular structure of the oil displacement agent is as follows:

[0023]

[0024] Wherein: m=2-50, more preferably m=5-10;

[0025] n=5-100, more preferably n=25-50.

[0026] In a second aspect, the present invention provides a method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent, the preparation method comprising: at 80-90° C., 4,4'-difluorobenzophenone and ammonium formate undergo a Leuckart-Wallach reaction in a first solvent; secondly, under the action of a catalyst, in a second solvent, in an oxygen-isolated environment, and under high temperature and high pressure conditions, the reaction product undergoes an etherification reaction with ethylene oxide.

[0027] In the present invention, preferably, based on 1 mole of 4,4'-difluorobenzophenone, the amounts of ammonium formate and ethylene oxide are 1-3 mole parts and 4-100 mole parts, respectively.

[0028] More preferably, based on 1 mole of 4,4'-difluorobenzophenone, the amounts of ammonium formate and ethylene oxide are 2-3 mole parts and 10-100 mole parts, respectively.

[0029] In the present invention, preferably, the first solvent is one of ethanol, propanol and isopropanol, and the mass ratio of the first solvent to 4,4'-difluorobenzophenone is 3-5:1.

[0030] In the present invention, preferably, the Leuckart-Wallach reaction time is 2-4 h.

[0031] More preferably, the Leuckart-Wallach reaction time is 2-3 h.

[0032] In the present invention, preferably, the catalyst is one of solid sodium hydroxide, solid potassium hydroxide, solid calcium hydroxide, and solid sodium ethoxide, and the mass ratio of the catalyst to 4,4'-difluorobenzophenone is 0.05-0.2:1.

[0033] In the present invention, preferably, the second solvent is one of benzene or toluene, and the mass ratio of the second solvent to 4,4'-difluorobenzophenone is 2-3:1.

[0034] In the present invention, preferably, the high temperature condition is a temperature of 110-180° C., and the high pressure condition is a pressure of 0.02-0.4 MPa.

[0035] More preferably, the high temperature condition is a temperature of 120-150° C., and the high pressure condition is a pressure of 0.05-0.2 MPa.

[0036] In the present invention, preferably, the etherification reaction time is 1-8h.

[0037] More preferably, the etherification reaction time is 2-5h.

[0038] According to a more specific preferred embodiment, the preparation method of the temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent specifically comprises the following steps:

[0039] (1) Add 4,4'-difluorobenzophenone, the first solvent, and ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and react at 80-90°C for 2-4 hours;

[0040] (2) distilling the mixed solution under reduced pressure until there is no fraction at 100° C. to obtain a viscous solid, which is dissolved in a second solvent and transferred to an autoclave;

[0041] (3) Add a catalyst to an autoclave, purge the autoclave and pipelines with nitrogen, seal the autoclave, evacuate, introduce ethylene oxide, raise the temperature to 110-180° C., raise the pressure to 0.02-0.4 MPa, keep the temperature for 1-8 hours, cool the circulating water to below 40° C., distill the mixed solution under reduced pressure to obtain a viscous solid, dissolve the viscous solid with methanol (30% by weight of the viscous solid), and adjust the pH to 8-9 with 10wt% hydrochloric acid to obtain a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent.

[0042] The reaction equation for synthesizing the heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent of the present invention is as follows:

[0043]

[0044] The third object of the present invention is to disclose the application of the above-mentioned temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent in the development of heavy oil reservoirs. There is no special requirement for the specific application, and it can be a conventional application in the field, which will not be discussed in detail here.

[0045] More preferably, the temperature of the applied heavy oil reservoir is less than 90° C., and the salinity is less than 120,000 mg / L.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0047] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0048] The present invention will be further described below with reference to specific embodiments.

[0049] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0050] In the following examples and comparative examples, unless otherwise specified, all reagents used were commercially available chemically pure reagents.

[0051] Example 1

[0052] (1) Add 0.5 mol 4,4'-difluorobenzophenone, 327 g ethanol, and 0.5 mol ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep the mixture at 80°C for 2 h;

[0053] (2) The mixed solution was distilled under reduced pressure until no fraction was found at 100°C to obtain a viscous solid, which was dissolved in 218 g of toluene and transferred to an autoclave;

[0054] (3) Add 5.5 g of sodium hydroxide to the autoclave, purge the autoclave and pipelines with nitrogen, seal the autoclave, evacuate, introduce 2 mol of ethylene oxide, raise the temperature to 110° C., raise the pressure to 0.02 MPa, keep the reaction warm for 1 hour, cool the circulating water to below 40° C., distill the mixed solution under reduced pressure to obtain a viscous solid, dissolve the viscous solid with methanol (30% by weight of the viscous solid), and adjust the pH to 8-9 with 10 wt % of hydrochloric acid to obtain the product, a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B1.

[0055] Example 2

[0056] (1) Add 0.5 mol 4,4'-difluorobenzophenone, 414 g propanol, and 0.7 mol ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep at 90°C for 2 h;

[0057] (2) The mixed solution was distilled under reduced pressure until no fraction was found at 100°C to obtain a viscous solid, which was dissolved in 249 g of toluene and transferred to an autoclave;

[0058] (3) 9.4 g of sodium hydroxide was added to the autoclave, the autoclave and pipelines were purged with nitrogen, the autoclave was sealed, evacuated, 5 mol of ethylene oxide was introduced, the temperature was raised to 122° C., the pressure was raised to 0.05 MPa, the reaction was kept warm for 2 h, the circulating water was cooled to below 40° C., the mixed solution was distilled under reduced pressure to obtain a viscous solid, and the viscous solid was dissolved with methanol (30% by weight of the viscous solid), and the pH was adjusted to 8-9 with 10 wt % of hydrochloric acid to obtain the product, a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B2.

[0059] Example 3

[0060] (1) Add 0.5 mol of 4,4'-difluorobenzophenone, 366 g of isopropanol, and 1 mol of ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep the mixture at 85°C for 3 h;

[0061] (2) distilling the mixed solution under reduced pressure until there is no fraction at 100°C to obtain a viscous solid, which is dissolved in 300 g of toluene and transferred to an autoclave;

[0062] (3) 10.3 g of potassium hydroxide was added to the autoclave, the autoclave and pipelines were purged with nitrogen, the autoclave was sealed, vacuumized, 10 mol of ethylene oxide was introduced, the temperature was raised to 132° C., the pressure was raised to 0.1 MPa, and the reaction was kept warm for 3 h. The circulating water was cooled to below 40° C., and the mixed solution was distilled under reduced pressure to obtain a viscous solid. The viscous solid was dissolved with methanol (30% by weight of the viscous solid), and the pH was adjusted to 8-9 with 10 wt % of hydrochloric acid to obtain the product, a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B3.

[0063] Example 4

[0064] (1) Add 0.5 mol 4,4'-difluorobenzophenone, 465 g propanol, and 1.2 mol ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep the mixture at 82°C for 3 h;

[0065] (2) The mixed solution was distilled under reduced pressure until no fraction was found at 100°C to obtain a viscous solid, which was dissolved in 327 g of toluene and transferred to an autoclave;

[0066] (3) 13.3 g of calcium hydroxide was added to the autoclave, the autoclave and pipelines were purged with nitrogen, the autoclave was sealed, evacuated, 20 mol of ethylene oxide was introduced, the temperature was raised to 144° C., the pressure was raised to 0.17 MPa, the reaction was kept warm for 4 h, the circulating water was cooled to below 40° C., the mixed solution was distilled under reduced pressure to obtain a viscous solid, 30% of the weight of the viscous solid was used to dissolve the viscous solid with methanol, and 10 wt% of hydrochloric acid was used to adjust the pH to 8-9 to obtain the product of heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B4.

[0067] Example 5

[0068] (1) Add 0.5 mol of 4,4'-difluorobenzophenone, 433 g of ethanol, and 1.2 mol of ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep the mixture at 86°C for 4 h;

[0069] (2) The mixed solution was distilled under reduced pressure until no fraction was found at 100°C to obtain a viscous solid, which was dissolved in 265 g of benzene and transferred to an autoclave;

[0070] (3) 17.6 g of sodium ethoxide was added to the autoclave, the autoclave and pipelines were purged with nitrogen, the autoclave was sealed, vacuumized, 30 mol of ethylene oxide was introduced, the temperature was raised to 158° C., the pressure was raised to 0.26 MPa, the reaction was kept warm for 6 h, the circulating water was cooled to below 40° C., the mixed solution was distilled under reduced pressure to obtain a viscous solid, and the viscous solid was dissolved with methanol (30% by weight of the viscous solid), and the pH was adjusted to 8-9 with 10 wt % of hydrochloric acid to obtain the product, a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B5.

[0071] Example 6

[0072] (1) Add 0.5 mol of 4,4'-difluorobenzophenone, 545 g of ethanol, and 1.4 mol of ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep the mixture at 83°C for 4 h;

[0073] (2) The mixed solution was distilled under reduced pressure until no fraction was found at 100°C to obtain a viscous solid, which was dissolved in 308 g of benzene and transferred to an autoclave;

[0074] (3) 18.9 g of sodium hydroxide was added to the autoclave, the autoclave and pipelines were purged with nitrogen, the autoclave was sealed, evacuated, 40 mol of ethylene oxide was introduced, the temperature was raised to 170° C., the pressure was raised to 0.34 MPa, the reaction was kept warm for 7 h, the circulating water was cooled to below 40° C., the mixed solution was distilled under reduced pressure to obtain a viscous solid, and the viscous solid was dissolved with methanol (30% by weight of the viscous solid), and the pH was adjusted to 8-9 with 10 wt % of hydrochloric acid to obtain the product, a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B6.

[0075] Example 7

[0076] (1) Add 0.5 mol 4,4'-difluorobenzophenone, 515 g ethanol, and 1.5 mol ammonium formate into a flask equipped with a stirrer, a condenser, and a thermometer, stir to dissolve, and keep the mixture at 87°C for 4 h;

[0077] (2) The mixed solution was distilled under reduced pressure until no fraction was found at 100°C to obtain a viscous solid, which was dissolved in 313 g of benzene and transferred to an autoclave;

[0078] (3) Add 21.8 g of potassium hydroxide to the autoclave, purge the autoclave and pipelines with nitrogen, seal the autoclave, evacuate, introduce 50 mol of ethylene oxide, raise the temperature to 180° C., raise the pressure to 0.4 MPa, and keep the reaction for 8 h. Cool the circulating water to below 40° C., distill the mixed solution under reduced pressure to obtain a viscous solid, dissolve the viscous solid with methanol (30% by weight of the viscous solid), and adjust the pH to 8-9 with 10 wt % of hydrochloric acid to obtain the product, a heat-resistant and salt-resistant heavy oil viscosity-reducing flooding agent B7.

[0079] Example 8 Testing of surface tension and interfacial tension

[0080] The oil-displacing agent of the present invention and the petroleum sulfonate of Shengli Chemical Plant are prepared into a 500 mg / L solution, and the surface tension is measured according to the ring-pulling method in SY / T 5370-2018 "Surface and interfacial tension determination method", and the interfacial tension is tested by the hanging drop method. The crude oil used to test the interfacial tension is the heavy oil of a block in Shengli Oilfield, and the viscosity of the crude oil is 23560 mPa·s at 50°C. The test results of the surface / interfacial tension are shown in Table 1.

[0081] It can be seen from Table 1 that the surface tension of the oil-displacing agents B1-B7 of the present invention is less than 26.5 mN / m, among which B5 is the lowest at 23.6 mN / m, while the surface tension of the comparative petroleum sulfonate is 29.4 mN / m, which is significantly higher than that of the present invention; the interfacial tension of the oil-displacing agents B1-B7 of the present invention is less than 6.5×10 -2 mN / m, among which B5 has the lowest value of 2.5×10 -2 mN / m, while the surface tension of the comparative petroleum sulfonate is 8.69×10 -2 mN / m, which is significantly higher than that of the present invention.

[0082] Example 9 Determination of Viscosity Reduction

[0083] The crude oil used in this experiment is the same as that in Example 8. The oil displacement agent of the present invention and the petroleum sulfonate of Shengli Chemical Plant are prepared into a 500 mg / L solution, and the evaluation method is based on Q / SH10201519-2016 "General Technical Requirements for Thick Oil Viscosity Reducers"

[0084]

[0085] Where:

[0086] f——viscosity reduction rate, %;

[0087] μ0——initial viscosity of crude oil at 50℃, mPa·s;

[0088] μ——Viscosity of crude oil after viscosity reduction, mPa·s.

[0089] The test results are shown in Table 1.

[0090] It can be seen from Table 1 that the viscosity reduction rates of the oil displacing agents B1-B7 of the present invention are all greater than 96% when used at a concentration of 500 mg / L, with B5 reaching a maximum of 99.2%, while the viscosity reduction rate of the comparative petroleum sulfonate is 69.8%, which is significantly lower than that of the present invention.

[0091] Table 1 Surface tension, interfacial tension, and viscosity reduction test results

[0092]

[0093] Example 10 Contact Angle Test

[0094] The viscosity reducing oil displacement agent B5 of the present invention and the petroleum sulfonate of Shengli Chemical Plant were prepared into a 500 mg / L solution. The hydrophobic core model was placed in the above solution, placed in a closed container, and placed in a 90°C oven for 12 hours. The core model was taken out and dried in a 100°C oven for 4 hours. After cooling, the contact angle was tested with distilled water. The results are shown in FIG. Figure 1 .

[0095] from Figure 1 It can be seen that the contact angle of the hydrophobic core model before treatment was 89.6°, and after treatment with the viscosity reducing oil displacement agent B5 of the present invention, the contact angle was reduced to 16.5°, while the contact angle after treatment with petroleum sulfonate was reduced to 51.0°, and the reduction range of the contact angle was significantly lower than that of the present invention.

[0096] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent, characterized in that: The preparation method comprises: at 80-90° C., 4,4'-difluorobenzophenone and ammonium formate undergo Leuckart-Wallach reaction in a first solvent; secondly, under the action of a catalyst, in a second solvent, in an oxygen-free environment, and under high temperature and high pressure conditions, the reaction product undergoes etherification reaction with ethylene oxide.

2. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent as claimed in claim 1, characterized in that: Based on 1 mole of 4,4'-difluorobenzophenone, the amounts of ammonium formate and ethylene oxide are 1-3 mole parts and 4-100 mole parts respectively.

3. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent as claimed in claim 2, characterized in that: Based on 1 mole of 4,4'-difluorobenzophenone, the amounts of ammonium formate and ethylene oxide are 2-3 mole parts and 10-100 mole parts respectively.

4. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1, characterized in that: The Leuckart-Wallach reaction time is 2-4h.

5. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent as claimed in claim 4, characterized in that: The Leuckart-Wallach reaction time is 2-3h.

6. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1, characterized in that: The first solvent is one of ethanol, propanol and isopropanol, and the mass ratio of the first solvent to 4,4'-difluorobenzophenone is 3-5:

1.

7. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1, characterized in that: The catalyst is one of solid sodium hydroxide, solid potassium hydroxide, solid calcium hydroxide and solid sodium ethoxide.

8. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1 or 7, characterized in that: The mass ratio of the catalyst to 4,4'-difluorobenzophenone is 0.05-0.2:

1.

9. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1, characterized in that: The second solvent is one of benzene or toluene, and the mass ratio of the second solvent to 4,4'-difluorobenzophenone is 2-3:

1.

10. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1, characterized in that: The high temperature condition is 110-180° C., and the high pressure condition is 0.02-0.4 MPa.

11. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 10, characterized in that: The high temperature condition is 120-150° C., and the high pressure condition is 0.05-0.2 MPa.

12. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 1, characterized in that: The etherification reaction time is 1-8h.

13. The method for preparing a temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to claim 12, characterized in that: The etherification reaction time is 2-5h.

14. A temperature-resistant and salt-resistant heavy oil viscosity-reducing oil displacement agent, characterized in that: The molecular structural formula of the oil displacing agent is as follows: Where: m = 2-50; n＝5-100。 15. A temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent as claimed in claim 14, characterized in that: The molecular structural formula of the oil displacing agent is as follows: Where: m = 5-10; n＝25-50。 16. Use of the temperature-resistant and salt-resistant heavy oil viscosity-reducing flooding agent according to any one of claims 14 to 15 in the development of heavy oil reservoirs.

17. The use according to claim 16, characterized in that The temperature of the applied heavy oil reservoir is less than 90° C., and the salinity is less than 120,000 mg / L.

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