A microemulsion oil recovery agent and its preparation method and application method

Abstract

The present invention provides a biodegradable microemulsion imbibition oil recovery agent, which comprises: (1) 15-35 parts of alkylamidopropyl hydroxysulfonic acid betaine; (2) 4-20 parts of modified sophorolipid sulfonate; (3) 5-18 parts of cosurfactant; (4) 3-25 parts of oil components; (5) 30-70 parts of brine. The microemulsion imbibition oil recovery agent of the present invention can improve the imbibition recovery rate of low-permeability or dense oil reservoirs, and its preparation process is simple, the reaction conditions are mild, the yield is high, it is particularly suitable for industrial production, and the economic benefits are remarkable. The chemical agent used is green and environmentally friendly, biodegradable, and can also bring good environmental benefits.

Description

Technical Field

[0001] The invention relates to an oil field oil recovery agent, in particular to a biodegradable oil recovery agent. Background Art

[0002] Oil and natural gas have become one of the three major strategic resources that affect my country's economic construction and sustainable development. Improving the mining technology of low-permeability reservoirs and tight oil and gas resources and breaking through the theoretical research and technical bottlenecks of oil and gas resource development are of great practical significance. Low-permeability reservoirs have low permeability and poor pore connectivity. During water injection development, the injection pressure is high, and the fluid mainly flows through the cracks. The fluid in the matrix rock is difficult to flow. A large amount of injected water flows directly into the production well through the cracks, which does not play an oil displacement role. It is an invalid cycle water injection and the development effect is poor.

[0003] Imbibition oil recovery is an important development method for low-permeability or tight oil reservoirs. It uses capillary force to absorb water and discharge oil, strengthens the oil-water replacement capacity between the matrix and fractures, and effectively improves crude oil recovery.

[0004] Microemulsion is an optically isotropic and thermodynamically stable solution system composed of oil, water and amphiphilic substances (molecules). It is transparent or translucent in appearance, has good solubilization effect and ultra-low interfacial tension. Studies have shown that in fresh water, salt water and microemulsion, the imbibition rate is the fastest and the recovery rate is the highest in microemulsion. In low-porosity and low-permeability reservoirs, microemulsions can greatly promote the penetration of water and transport it to the interface faster than surfactants to play a role. The diameter of microemulsion imbibition agents is mainly distributed in the range of 10nm-200nm. Due to its unique physical and chemical properties, it can enter the tiny pores of low-permeability reservoirs, reduce the oil-water interfacial tension, reduce the injection pressure, solubilize residual oil, and thus improve the recovery rate. The surfactant in the microemulsion is adsorbed on the surface of the rock wall, which changes the wettability of the rock and improves the imbibition efficiency. Microemulsions can form a miscible phase with formation oil to improve the recovery rate. In addition, water-in-oil microemulsions can solubilize a large amount of oil, and the solubilized oil moves forward with the microemulsion to the bottom of the well and is then produced. When the surfactant that makes up the microemulsion is anionic, it adsorbs on the surface of the oil droplets and the formation, which can increase the charge density on the rock surface and increase the electrostatic repulsion between the oil droplets and the formation surface. When the subsequent displacement fluid passes through the oil droplets, the oil droplets are easily carried away, improving the oil washing efficiency. During the underground flow of the microemulsion, it will automatically improve the microscopic heterogeneity of the reservoir, increase the viscosity of the displacement fluid, improve the oil-water mobility ratio, and prompt the solution to actively enter the low-permeability reservoir, playing a similar "profile adjustment" effect, thereby improving the sweep coefficient.

[0005] Patent CN 113004882 A discloses a microemulsion-type imbibition agent, a preparation method thereof and an oil-displacing fracturing fluid system. The microemulsion-type imbibition agent is a "core-shell" structure with a diameter of 9nm-500nm. In terms of weight percentage, the microemulsion-type imbibition agent includes 20-35% of a solvent, 15-25% of an emulsifier, 1-2.5% of a complexing agent, and the rest is water; the emulsifier includes 35-60% of a fatty alcohol ether grafted comb polymer, 25-35% of a zwitterionic surfactant, 2-5% of a perfluoroalkyl polyoxyethylene ether, and the rest is water. The perfluoroalkyl polyoxyethylene ether interacts with the fatty alcohol ether grafted comb polymer active agent and the zwitterionic surfactant to form a whole, i.e., a "core-shell structure" shell, which effectively reduces the surface tension. The fracturing fluid system containing the "core-shell structure" microemulsion-type imbibition agent has a strong displacement ability and a higher oil displacement efficiency than conventional oil-displacing agents. However, the fatty alcohol ether grafted comb polymer used in the invention has a relatively large molecular weight and is difficult to enter the tiny pores of low-permeability reservoirs or tight reservoirs. It mainly functions in the mainstream channel formed by the fracturing fluid, limiting the microscopic swept volume of the system.

[0006] Patent CN113563861A discloses a microemulsion composition, a nanoemulsion, and a preparation method and application thereof. The provided nanoemulsion can reduce the oil-water interfacial tension, change the wettability of the rock, and reduce the adsorption amount of the surfactant at the same time. It can be used as a fracturing fluid additive to increase the imbibition oil production during well shut-in after fracturing of the dense / shale reservoir, thereby achieving the purpose of increasing production. The nonionic surfactant described in the invention is selected from at least one of OP-10, TX-4, Tween80, Span60, and AEO-9. These conventional nonionic surfactants have a cloud point and poor temperature resistance, and are not suitable for high-temperature formations. The anionic surfactant is selected from at least one of SAS60, LAS, AES, and SDS. These anionic surfactants have poor salt resistance and are not suitable for high-salt formations.

[0007] Microemulsion is a thermodynamically stable system that forms spontaneously. Its formation mechanism is very complex. The key to its preparation lies in the selection of various pharmaceutical components and their ratio.

[0008] Currently, there are very few reports on the preparation of microemulsions and their use in imbibition oil recovery. Many traditional oilfield chemicals cannot meet the green and environmental requirements of the oil recovery field due to their high toxicity and irritation. There is an urgent need to develop green, low-toxic, biodegradable oil recovery agents. Summary of the invention

[0009] The purpose of the present invention is to provide a microemulsion imbibition oil recovery agent. The oil recovery agent of the present invention can improve the recovery rate of low-permeability oil reservoirs or dense oil reservoirs through imbibition, and is biodegradable.

[0010] The present invention uses lactone-type sophorolipids obtained by microbial fermentation as raw materials, obtains sulfonated modified sophorolipids through sulfonation reaction, and compounded with alkylamide hydroxysulfobetaine to form a microemulsion imbibition oil recovery agent in the presence of oil, water and a co-surfactant, thereby improving the recovery rate of low-permeability or dense oil reservoirs and ensuring the efficient development of oil fields.

[0011] The invention also provides a method for preparing the microemulsion imbibition oil recovery agent.

[0012] The invention also provides an application method of the microemulsion oil recovery agent.

[0013] The first aspect of the present invention provides a biodegradable microemulsion imbibition oil recovery agent, which comprises, based on the mass of each component:

[0014] (1) 15-35 parts, preferably 18-30 parts, more preferably 20-26 parts, of alkylamidopropyl hydroxysulfonate betaine;

[0015] (2) 4-20 parts, preferably 6-16 parts, more preferably 8-14 parts, of modified sophorolipid sulfonate;

[0016] (3) 5-18 parts of a co-surfactant, preferably 6-15 parts, more preferably 7-12 parts;

[0017] (4) 3-25 parts of oil components, preferably 5-20 parts, more preferably 8-16 parts;

[0018] (5) Contains 30-70 parts of salt water, preferably 35-60 parts, more preferably 40-50 parts.

[0019] The alkylamidopropyl hydroxysulfonic acid betaine has the following structural formula ①:

[0020]

[0021] In formula ①, R is C6~C 24 Any of the alkyl and alkenyl groups, preferably C8 to C 20 Alkyl, most preferably C 10 ~C 16 of normal alkyl.

[0022] The modified sophorolipid sulfonate has the following structural formula ②:

[0023]

[0024] In formula ②, M + is a cation selected from Li + 、Na + , K + NH4 + One or more of .

[0025] The modified sophorolipid sulfonate can be prepared according to methods known to those skilled in the art, for example, a lactone sophorolipid solution is subjected to a sulfonation reaction with sulfur trioxide at 60-90° C. to obtain a sulfonated modified sophorolipid. A suitable amount of sodium hydroxide is added to the sulfonated modified sophorolipid, and the pH of the solution is adjusted to neutral or weakly alkaline (pH 7.0-9.0) to obtain the modified sophorolipid sulfonate.

[0026] The co-surfactant is an alcohol with a carbon number of 2 to 8, preferably one or more of n-propanol, n-butanol, isopropanol and isobutanol.

[0027] The oil component is a mixture of one or more of crude oil, solvent oil, alkanes with a carbon number of 5 to 20, kerosene, and gasoline, preferably solvent oil and crude oil.

[0028] The salt water is oil well produced water with a mineralization in the range of 12000mg / L to 40000mg / L, or tap water with one or more inorganic salts added in a mass fraction of 12000mg / L to 40000mg / L, wherein the inorganic salts are preferably NaCl, KCl, NaHCO3, Na2CO3, etc. The mass fraction of the inorganic salts is preferably 20000mg / L to 35000mg / L.

[0029] The second aspect of the present invention provides a method for preparing a microemulsion oil recovery agent, which comprises: dissolving a sulfonated modified sophorolipid in a saline solution, adding an appropriate amount of alkali to adjust the pH of the solution to neutral or weak alkaline (pH = 7 to 9) to obtain a modified sophorolipid sulfonate, adding alkylamidopropyl hydroxysulfonic acid betaine, stirring evenly, adding oils, and then adding a co-surfactant, and mixing evenly.

[0030] Preferably, the mixing conditions at least meet the following conditions: temperature is 10-40° C., and stirring time is 10-60 min.

[0031] The third aspect of the present invention provides an application method of a microemulsion imbibition oil recovery agent, the method comprising:

[0032] The microemulsion imbibition oil recovery agent provided by the present invention is configured into a solution by using oil field injection water, wherein the mass fraction of the oil recovery agent in the solution is 5%-50%, preferably 10%-30%, and the injection amount of the microemulsion imbibition oil recovery agent is calculated according to data such as reservoir thickness, formation permeability, and treatment radius, and the microemulsion imbibition oil recovery agent solution is injected into the formation from the oil well, the well is shut down for 5-60 days, preferably 15-30 days, and then the well is opened for production.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) The present application uses lactone-type sophorolipids obtained by microbial fermentation as raw materials, prepares sulfonated modified sophorolipids through sulfonation reaction, and compounding with alkylamide hydroxysulfobetaine, and forms a microemulsion imbibition oil recovery agent in the presence of oil, water, and a co-surfactant. The microemulsion imbibition oil recovery agent of the present invention can significantly improve the seepage capacity of the oil-water two-phase in the oil reservoir, and can significantly improve the imbibition recovery rate of low-permeability cores.

[0035] (2) The microemulsion oil recovery agent of the present invention has a simple preparation process, mild reaction conditions, high yield, is particularly suitable for industrial production, and has significant economic benefits.

[0036] (3) The modified sophorolipid sulfonate and alkylamidopropyl hydroxysulfonate betaine in the microemulsion oil recovery agent composition of the present invention are biodegradable, green and environmentally friendly, can reduce the pollution problems caused by chemical agents to the environment, and can also bring greater environmental benefits on the basis of generating greater economic benefits. DETAILED DESCRIPTION

[0037] 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.

[0038] The lactone-type sophorolipids in the examples were purchased from Shandong Qilu Biotechnology Group Co., Ltd.

[0039] The dodecylamidopropyl hydroxysulfobetaine in the examples was purchased from Huainan Huajun New Material Technology Co., Ltd.

[0040] In the following examples, unless otherwise specified, all reagents used are commercially available chemical reagents, and there is no particular limitation on the sources of the reagents.

[0041] Preparation Example 1

[0042] Preparation of modified sophorolipid sulfonate GSH-1:

[0043] 68.88 g (100.0 mmol) of lactone-type sophorolipid was dissolved in 500 ml of N,N-dimethylformamide and stirred continuously at 50°C until completely dissolved. Then, 0.2 mol of sulfur trioxide pyridine complex was added and reacted at 80°C for 4 hours. After the reaction was completed, the solvent was removed by a rotary evaporator to obtain sulfonated modified sophorolipid GSH-1.

[0044] "Per serving" in the following examples means 1 g.

[0045] Example 1

[0046] Preparation of microemulsion oil recovery agent composition JW-1:

[0047] First, prepare a saline solution with a mass fraction of 35000 mg / L with sodium chloride and tap water. Take 12 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 45 parts of saline solution, add an appropriate amount of sodium hydroxide to adjust the solution pH to 7, then add 25 parts of dodecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 10 parts of 200# solvent oil, then add 8 parts of n-propanol, mix evenly, and prepare microemulsion JW-1.

[0048] Example 2

[0049] Preparation of microemulsion oil recovery agent composition JW-2:

[0050] First, prepare a saline solution with a mass fraction of 30000 mg / L with sodium chloride and tap water. Take 10 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 47 parts of saline solution, add an appropriate amount of sodium hydroxide to adjust the solution pH to 7.5, then add 20 parts of tetradecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 13 parts of 200# solvent oil, and then add 10 parts of n-propanol, mix evenly, and prepare microemulsion JW-2.

[0051] Example 3

[0052] Preparation of microemulsion oil recovery agent composition JW-3:

[0053] First, prepare a saline solution with a mass fraction of 25000 mg / L with sodium bicarbonate and tap water. Take 6 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 48 parts of saline solution, add an appropriate amount of sodium hydroxide to adjust the solution pH to 7, then add 30 parts of dodecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 8 parts of 200# solvent oil, and then add 8 parts of n-propanol, mix evenly, and prepare microemulsion JW-3.

[0054] Example 4

[0055] Preparation of microemulsion oil recovery agent composition JW-4:

[0056] First, potassium chloride and tap water were used to prepare a saline solution with a mass fraction of 20000 mg / L. 5 parts of sulfonated modified sophorolipid GSH-1 were taken and dissolved in 47 parts of saline solution, and an appropriate amount of sodium hydroxide was added to adjust the solution pH to 7.5, and then 17 parts of dodecylamidopropyl hydroxysulfonic acid betaine were added, stirred evenly, 16 parts of 200# solvent oil were added, and then 15 parts of n-propanol were added, mixed evenly, and microemulsion JW-4 was prepared.

[0057] Example 5

[0058] Preparation of microemulsion oil recovery agent composition JW-5:

[0059] First, use calcium chloride and tap water to prepare a saline solution with a mass fraction of 12000 mg / L. Take 12 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 47 parts of saline solution, add an appropriate amount of sodium hydroxide to adjust the solution pH to 8, then add 22 parts of dodecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 12 parts of 200# solvent oil, then add 7 parts of n-propanol, mix evenly, and prepare microemulsion JW-5.

[0060] Example 6

[0061] Preparation of microemulsion oil extraction agent composition JW-6:

[0062] First, prepare a saline solution with a mass fraction of 35000 mg / L with sodium chloride and tap water. Take 12 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 45 parts of saline solution, add an appropriate amount of sodium hydroxide to adjust the solution pH to 7, then add 25 parts of dodecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 10 parts of crude oil from a block of Shengli Oilfield (the viscosity of crude oil is 2.23 mPa·s at 50°C), and then add 8 parts of n-propanol, mix evenly, and prepare microemulsion JW-6.

[0063] Example 7

[0064] Preparation of microemulsion oil recovery agent composition JW-7:

[0065] First, prepare a saline solution with a mass fraction of 35000 mg / L with sodium chloride and tap water. Take 12 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 45 parts of saline solution, add an appropriate amount of sodium hydroxide to adjust the solution pH to 7, then add 25 parts of dodecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 10 parts of 200# solvent oil, then add 8 parts of n-butanol, mix evenly, and prepare microemulsion JW-7.

[0066] Comparative Example 1

[0067] Compared with Example 1, sodium chloride and tap water are first used to prepare a saline solution with a mass fraction of 30000 mg / L. Take 37 parts of dodecylamidopropyl hydroxysulfonic acid betaine, dissolve it in 45 parts of water, add 10 parts of 200# solvent oil, and then add 8 parts of n-propanol, and mix well. After standing, it is in a stratified state, with the upper layer being about 8 parts of the oil phase and the lower layer being about 92 parts of the homogeneous system. Use a separatory funnel to separate the lower homogeneous system, numbered DB-1.

[0068] Comparative Example 2

[0069] Compared with Example 1, sodium chloride and tap water are first used to prepare a saline solution with a mass fraction of 30000 mg / L. Take 37 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 45 parts of water, add an appropriate amount of sodium hydroxide to adjust the pH of the solution to neutral or weak alkaline (pH = 7-9), add 10 parts of 200# solvent oil, and then add 8 parts of n-propanol and mix well. After standing, it is in a stratified state, with the upper layer being about 10 parts of the oil phase and the lower layer being about 90 parts of a uniform system, and it is believed that no microemulsion is formed. Use a separatory funnel to separate the lower homogeneous system, numbered DB-2.

[0070] Comparative Example 3

[0071] Compared with Example 1, sodium chloride and tap water are first used to prepare a saline solution with a mass fraction of 35000 mg / L. Take 25 parts of sulfonated modified sophorolipid GSH-1, dissolve it in 45 parts of saline, add an appropriate amount of sodium hydroxide to adjust the pH of the solution to neutral or weak alkaline (pH = 7-9), then add 12 parts of dodecylamidopropyl hydroxysulfonic acid betaine, stir evenly, add 10 parts of 200# solvent oil, and then add 8 parts of n-propanol and mix evenly. After standing, it is in a stratified state, with the upper layer being about 5 parts of the oil phase and the lower layer being about 95 parts of a uniform system. Use a separatory funnel to separate the lower homogeneous system, numbered DB-3.

[0072] Test Example 1

[0073] Experimental conditions: The experimental oil is crude oil from a block of Shengli Oilfield, with a viscosity of 4.6 mPa·s at 50°C. The mineralization of the formation water used in the test is 30000 mg / L. Using formation water, the microemulsion imbibition oil recovery agent composition is respectively prepared into a solution with a mass fraction of 10%.

[0074] Core processing: 7 cores with a diameter of 2.5 cm and a length of about 8 cm were cut and polished from a hydrophilic outcrop rock. The cores were dried and the core-related parameters were measured, including size, porosity, and gas permeability. The gas permeability of the core was about 15.3×10 -3 μm.

[0075] Test process: vacuum the core to saturate the formation water, then saturate it with oil, record the saturated oil system, and age it for 24 hours. Put the core saturated with oil into the water absorption instrument, and then fill the water absorption instrument with formation water or a microemulsion oil recovery agent composition solution with a mass fraction of 10%, respectively. Put the water absorption instrument into a constant temperature box, keep the temperature at 50°C, and conduct a self-absorption experiment. Under the action of absorption, some oil droplets will be discharged from the surface of the core, and the oil droplets will float to the water surface. The volume of water absorption and oil discharge at different times can be directly read using the scale of the water absorption instrument. The absorption recovery rate is calculated based on the volume of water absorption and oil discharge after 5 days (120 hours). The test results are shown in Table 1.

[0076] Table 1 Imbibition recovery of cores by different compositions

[0077] serial number Saturated oil volume / mL Water absorption and oil discharge volume / mL Imbibition recovery rate / % Formation water 6.65 0.68 10.23 JW-1 6.70 2.11 31.49 JW-2 6.60 1.95 29.55 JW-3 6.65 1.64 24.66 JW-4 6.65 1.43 21.50 JW-5 6.60 1.74 26.36 JW-6 6.72 2.09 31.10 JW-7 6.61 2.01 30.41 DB-1 6.68 1.15 17.22 DB-2 6.62 1.08 16.31 DB-3 6.73 1.28 19.02

[0078] It can be seen from Table 1 that the microemulsion imbibition oil recovery agent of the present invention can significantly improve the imbibition recovery rate of low permeability cores.

Claims

1. A microemulsion imbibition oil recovery agent, comprising, by weight of each component: (1) 15-35 parts of alkylamidopropyl hydroxysulfonate betaine; (2) 4-20 parts of modified sophorolipid sulfonate; (3) 5-18 parts of co-surfactant; (4) 3-25 parts of oil components; (5) containing 30-70 parts of salt water; The modified sophorolipid sulfonate has the following structural formula: Where M + is a cation selected from Li + 、Na + , K + NH4 + One or more of; The co-surfactant is an alcohol having 2 to 8 carbon atoms; The oil component is one or more of crude oil, solvent oil, alkanes with a carbon number of 5 to 20, kerosene, and gasoline; The salt water is oil well produced water with a mineralization within the range of 12000mg / L to 40000mg / L, or tap water with one or more inorganic salts added at a mass fraction of 12000mg / L to 40000mg / L.

2. The oil recovery agent according to claim 1, comprising, by weight of each component: (1) 18-30 parts of alkylamidopropyl hydroxysulfonate betaine; (2) 6-16 parts of modified sophorolipid sulfonate; (3) 6-15 parts of co-surfactant; (4) 5-20 parts of oil components; (5) Contains 35-60 parts of salt water.

3. The oil recovery agent according to claim 1, comprising, by weight of each component: (1) 20-26 parts of alkylamidopropyl hydroxysulfonate betaine; (2) 8-14 parts of modified sophorolipid sulfonate; (3) 7-12 parts of co-surfactant; (4) 8-16 parts of oil components; (5) Contains 40-50 parts of salt water.

4. The oil recovery agent according to any one of claims 1 or 3, wherein The alkylamidopropyl hydroxysulfonate betaine has the following structural formula: In the formula, R is selected from C6~C 24 Any one of the alkyl groups.

5. The oil recovery agent according to claim 4, wherein R is selected from C8~C 20 of alkyl.

6. The oil recovery agent according to claim 1, wherein The auxiliary surfactant is selected from one or more of n-propanol, n-butanol, isopropanol and isobutanol.

7. The oil recovery agent according to claim 1, wherein The oil component is selected from solvent oil and crude oil.

8. The oil recovery agent according to claim 1, wherein The salt water is tap water with one or more inorganic salts added in a mass fraction of 12000mg / L to 40000mg / L, and the inorganic salts are selected from NaCl, KCl, NaHCO3, and Na2CO3.

9. A method for preparing the microemulsion imbibition oil recovery agent according to any one of claims 1 to 8, comprising: The sulfonated modified sophorolipid is dissolved in saline water, an appropriate amount of alkali is added to adjust the pH of the solution to neutral or weak alkalinity to obtain a modified sophorolipid sulfonate, alkylamidopropyl hydroxysulfonic acid betaine is added, stirred evenly, oils are added, and then a co-surfactant is added and mixed evenly.

10. The method according to claim 9, wherein: The mixing conditions at least meet the following requirements: temperature of 10-40° C. and stirring time of 10-60 min.

11. An application method of a microemulsion oil recovery agent, comprising: The microemulsion imbibition oil recovery agent according to any one of claims 1 to 8 is prepared into a solution using oilfield injection water, wherein the mass fraction of the oil recovery agent in the solution is 5% to 50%, and the microemulsion imbibition oil recovery agent solution is injected into the formation from the oil well, the well is shut down for 5 to 60 days, and then the well is opened for production.

Images