A microemulsion type oil displacement agent and its preparation method and application in oil recovery, oil displacement nanoemulsion

Abstract

The present invention belongs to the technical field of oilfield exploitation, and provides a microemulsion type oil displacement agent and a preparation method thereof, and an application thereof in oil production, and an oil displacement nanoemulsion. The present invention provides an application of a microemulsion type oil displacement agent in oilfield oil production, wherein the microemulsion type oil displacement agent comprises the following components in mass percentage: 15-35% surfactant, 55-70% water, and 3-15% oil; after the microemulsion type oil displacement agent of the present invention is injected into the oil layer, it can change the wettability of the rock, reduce the oil-water interfacial tension, and enable the oil to be efficiently stripped from the rock, thereby improving the oil recovery rate. In addition, the microemulsion type oil displacement agent of the present invention has excellent emulsification. After being injected into a wellbore, it can emulsify the heavy oil sediments deposited in the wellbore, realize the dissolution and removal of the heavy oil sediments, realize the dredging of the wellbore, and ultimately improve the oil recovery rate of the oil.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield exploitation, and in particular to a microemulsion oil displacement agent and a preparation method thereof, and application thereof in oil production, and an oil displacement nanoemulsion. Background Art

[0002] The preparation and application of nano-displacement systems have shown great potential in improving crude oil recovery and have received increasing attention. At present, nano-displacement agents have been successfully developed and applied in laboratories and oil fields at home and abroad, proving the feasibility of nano-displacement agents. The synthesis of nano-displacement agents mainly adopts chemical methods. The chemical method requires less energy in the reduction process of synthesizing nanoemulsions, and the particles formed are homogeneous and have high size and shape precision. However, chemical methods use various dangerous chemicals, which are carcinogenic, genotoxic and cytotoxic, and are therefore not environmentally friendly; and the oil recovery rate of petroleum needs to be further improved. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a microemulsion type oil displacement agent and its preparation method and application in oil recovery, and oil recovery nanoemulsion. The microemulsion type oil displacement agent of the present invention can reduce the ultra-low interfacial tension formed by oil-water, and can improve the oil recovery rate when used in oil field oil recovery; and the microemulsion type oil displacement agent is environmentally friendly and low in toxicity.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides an application of a microemulsion oil displacement agent in oil field production. The microemulsion oil displacement agent comprises the following components in percentage by mass:

[0006] Surfactant 15~35%, water 55~70%, oil 3~15%;

[0007] The surfactant includes a nonionic surfactant, an anionic biosurfactant and a cosurfactant;

[0008] The nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone type sophorolipid;

[0009] The anionic biosurfactant is rhamnolipid;

[0010] The co-surfactant is a small molecule alcohol;

[0011] The oil is vegetable oil.

[0012] Preferably, the microemulsion type oil-displacing agent is used in the form of an oil-displacing nanoemulsion, and the mass fraction of the microemulsion type oil-displacing agent in the oil-displacing nanoemulsion is 0.2%.

[0013] Preferably, the method comprises the following steps:

[0014] The microemulsion oil displacement agent is injected into the oil layer to perform huff and puff or displacement, thereby improving the oil recovery rate.

[0015] Preferably, the method comprises the following steps:

[0016] The microemulsion oil displacement agent is injected into the wellbore for cleaning or repairing to improve the oil recovery rate.

[0017] The present invention also provides a microemulsion oil-displacing agent, comprising the following components in percentage by mass:

[0018] Surfactant 15~35%, water 55~70%, oil 3~15%;

[0019] The surfactant includes a nonionic surfactant, an anionic biosurfactant and a cosurfactant;

[0020] The nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone type sophorolipid;

[0021] The anionic biosurfactant is rhamnolipid;

[0022] The co-surfactant is a small molecule alcohol;

[0023] The oil is vegetable oil.

[0024] Preferably, the general formula of the fatty alcohol polyoxyethylene ether is RO(CH2CH2O) n H, R is saturated or unsaturated C 12 ~C 18 The hydrocarbon group, n is the number of ethylene oxide additions;

[0025] The molecular formula of the polyoxyethylene sorbitan monooleate is C 46 H 52 N5O8P;

[0026] The molecular formula of the decyl glucoside is C 16 H 32 O6;

[0027] The lactone-type sophorolipid is composed of hydrophilic sophorose and a hydrophobic part; the hydrophobic part is a saturated or unsaturated long-chain ω-hydroxy fatty acid, or a saturated or unsaturated long-chain ω-1 hydroxy fatty acid; the lactone-type sophorolipid has a structure shown in Formula 1:

[0028] Formula 1.

[0029] Preferably, the rhamnolipid is a biological metabolite produced by Pseudomonas;

[0030] The rhamnolipids include 21 homologues of hydrophobic long-chain fatty acids linked by one or two glucose groups;

[0031] The rhamnolipid has a structure shown in Formula 2:

[0032] Formula 2.

[0033] Preferably, the mass ratio of the nonionic surfactant to the anionic biosurfactant is 1 to 4:1;

[0034] The small molecule alcohol includes one or more of propylene glycol, n-butanol and triethylene glycol; the vegetable oil includes at least one of palm oil, coconut oil and olive oil.

[0035] The present invention also provides a method for preparing the microemulsion oil-displacing agent described in the above technical solution, comprising the following steps:

[0036] The nonionic surfactant, the anionic biosurfactant, the co-surfactant and water are first mixed to obtain an aqueous phase;

[0037] The water phase and the oil are mixed for a second time to obtain the microemulsion type oil displacing agent.

[0038] The present invention also provides an oil-displacing nanoemulsion, which is prepared from the microemulsion oil-displacing agent described in the above technical solution or the microemulsion oil-displacing agent prepared by the preparation method described in the above technical solution and water; the mass fraction of the microemulsion oil-displacing agent in the oil-displacing nanoemulsion is 0.2%.

[0039] The present invention provides an application of a microemulsion type oil displacement agent in oil field production. After the microemulsion type oil displacement agent of the present invention is injected into the oil layer, it can change the wettability of the rock, reduce the oil-water interfacial tension, so that the oil can be efficiently peeled off from the rock, thereby improving the oil recovery rate of the oil. In addition, the microemulsion type oil displacement agent of the present invention has excellent emulsification. After being injected into the wellbore, it can emulsify the heavy oil sediments deposited in the wellbore, realize the dissolution and removal of the heavy oil sediments, realize the repair and cleaning of the wellbore, make the wellbore more unobstructed, and finally improve the oil recovery rate of the oil.

[0040] The present invention also provides a microemulsion oil-displacing agent, comprising the following components in mass percentage: 15-35% surfactant, 55-70% water and 3-15% oil; the surfactant comprises a non-ionic surfactant, an anionic biosurfactant and a co-surfactant; the non-ionic surfactant comprises one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone-type sophorolipid; the anionic biosurfactant is rhamnolipid; the co-surfactant is a small molecule alcohol; and the oil is a vegetable oil.

[0041] The present invention combines a nonionic surfactant (one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone-type sophorolipid) with an anionic biosurfactant (rhamnolipid), and with the assistance of a co-surfactant (small molecule alcohol), a mixed adsorption layer can be formed between the oil-water interface, thereby reducing the oil-water interfacial tension; at the same time, the microemulsion oil displacement agent of the present invention is low in toxicity and environmentally friendly. The data in the embodiment show that when the mass fraction of the microemulsion oil displacement agent is 0.2%, the interfacial tension of the resulting oil displacement nanoemulsion can be 10 -2 The oil washing rate is 98.16%. DETAILED DESCRIPTION

[0042] The present invention provides an application of a microemulsion oil displacement agent in oil field production. The microemulsion oil displacement agent comprises the following components in percentage by mass:

[0043] Surfactant 15~35%, water 55~70%, oil 3~15%;

[0044] The surfactant includes a nonionic surfactant, an anionic biosurfactant and a cosurfactant;

[0045] The nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone type sophorolipid;

[0046] The anionic biosurfactant is rhamnolipid;

[0047] The co-surfactant is a small molecule alcohol;

[0048] The oil is vegetable oil.

[0049] In the present invention, the components of the microemulsion oil displacing agent are preferably described in detail in the subsequent microemulsion oil displacing agent section and will not be described here.

[0050] In the present invention, the microemulsion type oil displacing agent is preferably used in the form of an oil displacing nanoemulsion, and the mass fraction of the microemulsion type oil displacing agent in the oil displacing nanoemulsion is preferably 0.2%.

[0051] In the present invention, when the microemulsion oil displacement agent is used in oil field production, it preferably includes the following steps:

[0052] The microemulsion oil displacement agent is injected into the oil layer to perform huff and puff or displacement, thereby improving the oil recovery rate.

[0053] The present invention does not specifically limit the position and injection amount of the microemulsion oil displacement agent, and techniques well known to those skilled in the art can be used. The present invention does not specifically limit the parameters of the throughput and displacement, and operations well known to those skilled in the art can be used.

[0054] The microemulsion oil-displacing agent of the present invention can change the wettability of the rock surface, reduce the oil-water interfacial tension, and thus enable the oil to be well stripped from the rock surface, thereby achieving efficient oil extraction.

[0055] In the present invention, when the microemulsion oil displacement agent is used in oil field production, it is preferred to further include the following steps:

[0056] The microemulsion oil displacement agent is injected into the wellbore for cleaning or repairing to improve the oil recovery rate.

[0057] The present invention does not specifically limit the position and injection amount of the microemulsion oil displacement agent, and techniques well known to those skilled in the art can be used. The present invention does not specifically limit the operations and parameters of the cleaning and repairing, and operations well known to those skilled in the art can be used.

[0058] The microemulsion oil displacement agent of the present invention has excellent emulsification, and can emulsify heavy oil sediments deposited in the wellbore, dissolve the heavy oil sediments from the wellbore wall, thereby achieving dredging of the wellbore and ultimately improving the oil recovery rate.

[0059] The present invention also provides a microemulsion oil-displacing agent, comprising the following components in percentage by mass:

[0060] Surfactant 15~35%, water 55~70% and oil 3~15%;

[0061] The surfactant includes a nonionic surfactant, an anionic biosurfactant and a cosurfactant;

[0062] The nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone type sophorolipid;

[0063] The anionic biosurfactant is rhamnolipid;

[0064] The co-surfactant is a small molecule alcohol;

[0065] The oil is vegetable oil.

[0066] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0067] The microemulsion oil displacement agent provided by the present invention comprises a surfactant having a mass percentage of 15 to 35%, preferably 20 to 35%, or preferably 15 to 30%. In the present invention, the surfactant comprises a nonionic surfactant, an anionic biosurfactant and a cosurfactant. In the present invention, the mass ratio of the nonionic surfactant to the anionic biosurfactant is preferably 1 to 4:1; the ratio of the total mass of the nonionic surfactant and the anionic biosurfactant to the mass of the cosurfactant is preferably 1:2 to 6.

[0068] In the present invention, the nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, polyoxyethylene sorbitan monooleate, decyl glucoside and lactone type sophorolipid, and is further preferably fatty alcohol polyoxyethylene ether or lactone type sophorolipid. In the present invention, the structural formula of the fatty alcohol polyoxyethylene ether is RO(CH2CH2O) n H, wherein R is preferably a saturated or unsaturated C 12 ~C 18 The hydrocarbon group is preferably a straight-chain hydrocarbon group or a branched hydrocarbon group. In the present invention, the RO (CH2CH2O) n The n in H is the addition number of ethylene oxide, that is, the number of ethylene oxide pairs in the surfactant molecule. In a specific embodiment of the present invention, n is preferably 9, that is, the fatty alcohol polyoxyethylene ether is preferably AEO-9.

[0069] In the present invention, the lactone type sophorolipid is preferably composed of hydrophilic sophorose and a hydrophobic part; the hydrophobic part is preferably a saturated or unsaturated long-chain ω-hydroxy fatty acid, or a saturated or unsaturated long-chain ω-1 hydroxy fatty acid. In the present invention, the lactone type sophorolipid preferably has a structure shown in Formula 1:

[0070] Formula 1.

[0071] In the present invention, the lactone-type sophorolipid is preferably a microbial secondary metabolite produced by fermentation of Candida albicans using sugar and vegetable oil as carbon sources.

[0072] In the present invention, the anionic biosurfactant is a rhamnolipid. In the present invention, the rhamnolipid is preferably a biological metabolite produced by Pseudomonas. In the present invention, the rhamnolipid preferably comprises 21 homologues of hydrophobic long-chain fatty acids connected by one or two glucose groups. In the present invention, the rhamnolipid preferably has a structure shown in Formula 2:

[0073] Formula 2.

[0074] In the present invention, the rhamnolipid is preferably obtained by fermentation using vegetable oil as a carbon source.

[0075] In the present invention, the co-surfactant is a small molecule alcohol, and the small molecule alcohol preferably includes one or more of propylene glycol, n-butanol and triethylene glycol, more preferably propylene glycol or triethylene glycol, and more preferably triethylene glycol.

[0076] In the present invention, the nonionic surfactant and the anionic biosurfactant both contain a hydrophilic group and a lipophilic group, so that both have certain hydrophilicity and lipophilicity, but due to the difference between their polar functional groups and nonpolar alkyl chains, the lipophilic and hydrophilic abilities of the two are different. The present invention compounds the two types of surfactants, and the mass ratio of the nonionic surfactant to the anionic biosurfactant is 1 to 4:1. The new surfactant compounded according to this ratio, under the auxiliary action of the co-surfactant, can form a mixed adsorption layer between the oil-water interface, so that the oil-water interfacial tension is reduced.

[0077] The microemulsion oil-displacing agent provided by the present invention comprises 55-70% by mass of water, and the water is preferably distilled water.

[0078] The microemulsion oil-displacing agent provided by the present invention comprises 3-15% by mass of oil, wherein the oil is preferably vegetable oil, and the vegetable oil preferably comprises at least one of palm oil, coconut oil and olive oil, and is further preferably coconut oil.

[0079] The present invention also provides a method for preparing the microemulsion oil-displacing agent described in the above technical solution, comprising the following steps:

[0080] The nonionic surfactant, the ionic surfactant, the co-surfactant and water are first mixed to obtain an aqueous phase;

[0081] The water phase and the oil are mixed for a second time to obtain the microemulsion type oil displacing agent.

[0082] The present invention first mixes a nonionic surfactant, an ionic surfactant, a co-surfactant and water to obtain a water phase.

[0083] In the present invention, the temperature of the first mixing is preferably 30-40°C, more preferably 35°C, the first mixing is preferably carried out under stirring, the stirring speed is preferably 500-800r / min, more preferably 700r / min, and the stirring time is preferably 30min.

[0084] After obtaining the water phase, the present invention secondly mixes the water phase and the oil to obtain the microemulsion oil displacement agent.

[0085] In the present invention, the second mixing method of the water phase and the oil preferably comprises: adding the oil dropwise into the water phase.

[0086] In the present invention, the temperature of the second mixing is preferably 30-40° C., the second mixing is preferably performed under stirring, the stirring speed is preferably 500-800 r / min, and the stirring time is preferably 10-30 min.

[0087] The present invention also provides an oil-displacing nanoemulsion, which is prepared from the microemulsion oil-displacing agent described in the above technical solution or the microemulsion oil-displacing agent prepared by the preparation method described in the above technical solution and water; the mass fraction of the microemulsion oil-displacing agent in the oil-displacing nanoemulsion is 0.2%.

[0088] The microemulsion oil displacement agent provided by the present invention, its preparation method and application in oil recovery, and the oil displacement nanoemulsion are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0089] Test Equipment

[0090] Digital display constant temperature and speed measurement magnetic stirrer: MHS4PRO, Aikemai Scientific Instrument Zhejiang Co., Ltd.; Nanoparticle size and Zeta potential instrument: NanoBrook ZetaPlus, Brookhaven Instrument Company, USA; Spinning drop interfacial tension meter: TX500D, Shanghai Solon Science and Technology Information Co., Ltd.

[0091] raw material

[0092] Non-ionic surfactant: fatty alcohol polyoxyethylene ether AEO-9, Yangzi Petrochemical-BASF Co., Ltd.; non-ionic surfactant: lactone sophorolipid, Feitian Agriculture Co., Ltd.; anionic biosurfactant: rhamnolipid, Feitian Agriculture Co., Ltd.; co-surfactant: n-butanol, Shanghai McLean Biochemical Technology Co., Ltd.; co-surfactant: propylene glycol, Shanghai McLean Biochemical Technology Co., Ltd.; co-surfactant: triethylene glycol, Shanghai McLean Biochemical Technology Co., Ltd.; vegetable oil: palm oil, Shanghai McLean Biochemical Technology Co., Ltd.; vegetable oil: coconut oil, Shanghai McLean Biochemical Technology Co., Ltd.; vegetable oil: olive oil, Shanghai McLean Biochemical Technology Co., Ltd.

[0093] Example 1

[0094] Weigh 1 g of rhamnolipid and mix it with fatty alcohol polyoxyethylene ether AEO-9 in a mass ratio of 1:1 to obtain a rhamnolipid AEO-9 mixed system; then take 1 g of the rhamnolipid AEO-9 mixed system, and weigh 5 g of triethylene glycol in a mass ratio of 1:5 between the rhamnolipid AEO-9 mixed system and triethylene glycol, and dissolve the three in 10 g of distilled water, use a magnetic stirrer to mix at 700 r / min and 35°C for 30 minutes, and then add 2 g of coconut oil dropwise to obtain a microemulsion oil-displacing agent.

[0095] Weigh 0.2 g of the obtained microemulsion oil-displacing agent and mix it with 100 g of distilled water to obtain a clear-looking microemulsion oil-displacing agent with a mass fraction of 0.2% oil-displacing nanoemulsion.

[0096] Example 2

[0097] Weigh 1 g of rhamnolipid and fatty alcohol polyoxyethylene ether AEO-9 at a mass ratio of 1:1.5 to obtain a rhamnolipid AEO-9 mixed system; then take 1 g of the rhamnolipid AEO-9 mixed system, and weigh 4 g of triethylene glycol according to a mass ratio of the rhamnolipid AEO-9 mixed system to triethylene glycol of 1:4, and dissolve the three in 10 g of distilled water, use a magnetic stirrer to mix at 700 r / min and 35°C for 30 min, and then add 2 g of coconut oil dropwise to obtain a microemulsion oil-displacing agent;

[0098] Weigh 0.2 g of microemulsion oil-displacing agent and mix it with 100 g of distilled water to obtain a clear-looking microemulsion oil-displacing agent with a mass fraction of 0.2%.

[0099] Example 3

[0100] The difference from Example 2 is that the mass ratio of rhamnolipid to fatty alcohol polyoxyethylene ether AEO-9 is 1:2.

[0101] Example 4

[0102] The difference from Example 2 is that the mass ratio of rhamnolipid to fatty alcohol polyoxyethylene ether AEO-9 is 1:3.

[0103] Example 5

[0104] The difference from Example 2 is that the mass ratio of rhamnolipid to fatty alcohol polyoxyethylene ether AEO-9 is 1:4.

[0105] Comparative Example 1

[0106] The difference from Example 2 is that the mass ratio of rhamnolipid to fatty alcohol polyoxyethylene ether AEO-9 is 1:5.

[0107] Comparative Example 2

[0108] The difference from Example 2 is that the mass ratio of rhamnolipid to fatty alcohol polyoxyethylene ether AEO-9 is 1:0.5.

[0109] Example 6

[0110] Weigh 1 g of rhamnolipid and fatty alcohol polyoxyethylene ether AEO-9 at a mass ratio of 1:2 to obtain a rhamnolipid AEO-9 mixed system; then take 1 g of the rhamnolipid AEO-9 mixed system and weigh triethylene glycol at a mass ratio of 1:3 between the rhamnolipid AEO-9 mixed system and triethylene glycol, and dissolve the three in 10 g of distilled water, use a magnetic stirrer to mix at 700 r / min and 35° C. for 30 min, then add 2 g of coconut oil dropwise to obtain a microemulsion oil-displacing agent;

[0111] Weigh 0.2 g of microemulsion oil-displacing agent and mix it with 100 g of distilled water to obtain a clear-looking microemulsion oil-displacing agent with a mass fraction of 0.2%.

[0112] Example 7

[0113] The difference from Example 6 is that triethylene glycol is replaced by n-butanol.

[0114] Example 8

[0115] The difference from Example 6 is that triethylene glycol is replaced by propylene glycol.

[0116] Comparative Example 3

[0117] The difference from Example 6 is that triethylene glycol is replaced by ethanol.

[0118] Example 9

[0119] The difference from Example 6 is that the fatty alcohol polyoxyethylene ether AEO-9 is replaced by a lactone type sophorolipid, specifically:

[0120] Weigh 1 g of rhamnolipid and lactone sophorolipid and mix them in a mass ratio of 1:2 to obtain a rhamnolipid-lactone sophorolipid mixed system; then take 1 g of the rhamnolipid-lactone sophorolipid mixed system, and weigh triethylene glycol in a mass ratio of 1:3 between the rhamnolipid-lactone sophorolipid mixed system and triethylene glycol, dissolve the three in 10 g of distilled water, and use a magnetic stirrer to mix at 700 r / min and 35°C for 30 min, then add 2 g of coconut oil dropwise to obtain a microemulsion oil-displacing agent.

[0121] Weigh 0.2 g of the obtained microemulsion oil-displacing agent and mix it with 100 g of distilled water to obtain a clear-looking microemulsion oil-displacing agent with a mass fraction of 0.2% oil-displacing nanoemulsion.

[0122] Example 10

[0123] The difference from Example 6 is that the fatty alcohol polyoxyethylene ether AEO-9 is replaced by polyoxyethylene sorbitan monooleate.

[0124] Embodiment 11

[0125] The difference from Example 6 is that triethylene glycol is weighed according to a mass ratio of rhamnolipid AEO-9 mixed system to triethylene glycol of 1:5.

[0126] Example 12

[0127] The difference from Example 6 is that triethylene glycol is weighed according to the mass ratio of the rhamnolipid AEO-9 mixed system to triethylene glycol of 1:2.

[0128] Comparative Example 4

[0129] The difference from Example 6 is that triethylene glycol is weighed in a mass ratio of 1:1 between the rhamnolipid AEO-9 mixed system and triethylene glycol.

[0130] Comparative Example 5

[0131] The difference from Example 6 is that triethylene glycol is weighed according to a mass ratio of rhamnolipid AEO-9 mixed system to triethylene glycol of 1:6.

[0132] The average particle size, interfacial tension and stability of the obtained microemulsion-type oil-displacing agent with a mass fraction of 0.2% were measured, and the results are shown in Table 1.

[0133] Table 1 Physicochemical properties of the oil displacement nanoemulsions obtained in the examples and comparative examples

[0134]

[0135] It can be seen from Table 1 that the average particle size of the oil-displacing nanoemulsion with a mass fraction of 0.2% in the microemulsion type oil-displacing agent in the embodiment is about 50nm, and the interfacial tension is 10 -2mN / M order of magnitude and can be stored stably.

[0136] Application Example 1

[0137] The oil-displacing nanoemulsions obtained in Examples 6, 7 and 9 were used to carry out oil-displacing tests on oil sands.

[0138] Experimental samples

[0139] The oil-displacing nanoemulsions obtained in Example 6, Example 7 and Example 9; the crude oil from the formation of the oil field, obtained by high-temperature dehydration and separation; 40-70 mesh quartz sand (Lianyungang Haosen Mineral Products Co., Ltd.).

[0140] The quartz sand was rinsed with water and the water therein was dried, and the oil and sand were mixed in a mass ratio of 1:5 and placed in an oven at 60°C for aging for 24 hours, and then taken out as experimental oil sand samples for use.

[0141] Determination of oil content of oil sand sample: accurately weigh 50g oil sand sample (wrapped with filter paper), add 200mL petroleum ether into 500mL round bottom flask, heat and reflux at 90℃ to extract until the solution flowing out of the sample sleeve is colorless, bake the extracted oil sand sample at 150℃ for 5h and weigh it. Repeat the above steps twice, calculate the average of the oil content of 3 times, and this data is the oil content of the oil sand sample.

[0142] The oil displacement nanoemulsion obtained in Example 6, Example 7, and Example 9 was mixed with the oil sand sample at a mass ratio of 1:1; stirred in a constant temperature water bath stirrer at 38°C for 25 minutes, allowed to stand for 15 minutes, the oil sand asphalt on the liquid surface was scraped off, the solution was poured out, the separated oil sand was placed in a drying oven at 105°C for 65 minutes, weighed, and the oil content of the remaining oil sand was calculated using the oil content determination method of the oil sand sample. The oil washing rate of each implementation case was calculated as follows:

[0143]

[0144] Where: W y : Oil washing rate, (wt)%, W oil : Original oil sand oil content, (wt)%, W’ oil : Oil content of case oil sands, (wt)%.

[0145] The results are shown in Table 2.

[0146] Table 2 Oil content results

[0147]

[0148] It can be seen from Table 2 that the oil washing rate of the oil-displacing nanoemulsion obtained in Example 6 is 98.16%, the oil washing rate of the oil-displacing nanoemulsion obtained in Example 7 is 94.79%, and the oil washing rate of the oil-displacing nanoemulsion obtained in Example 9 is 95.71%. The configured oil-displacing nanoemulsion can wash out the oil in the oil sand very well, among which Example 6 has the best effect.

[0149] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Application of a microemulsion oil displacement agent in oil field production, characterized in that: The microemulsion oil displacing agent is composed of the following components in percentage by mass: Surfactant 15~35%, water 55~70%, oil 3~15%; The surfactant includes a nonionic surfactant, an anionic biosurfactant and a co-surfactant; The nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-9, polyoxyethylene sorbitan monooleate or lactone type sophorolipid; The anionic biosurfactant is rhamnolipid; The co-surfactant is a small molecule alcohol, and the small molecule alcohol is triethylene glycol, n-butanol or propylene glycol; The oil is vegetable oil, and the vegetable oil is coconut oil; The mass ratio of the nonionic surfactant to the anionic biosurfactant is 1-4:1; The ratio of the total mass of the nonionic surfactant and the anionic biosurfactant to the mass of the co-surfactant is 1:2-5.

2. The use according to claim 1, characterized in that: The microemulsion oil-displacing agent is used in the form of an oil-displacing nanoemulsion, and the mass fraction of the microemulsion oil-displacing agent in the oil-displacing nanoemulsion is 0.2%.

3. The use according to claim 1 or 2, characterized in that: The following steps are involved: The microemulsion oil displacement agent is injected into the oil layer to perform huff and puff or displacement, thereby improving the oil recovery rate.

4. The use according to claim 1 or 2, characterized in that: The following steps are involved: The microemulsion oil displacement agent is injected into the wellbore for cleaning or repairing to improve the oil recovery rate.

5. A microemulsion oil displacing agent, characterized in that: It is composed of the following components in percentage by mass: Surfactant 15~35%, water 55~70%, oil 3~15%; The surfactant includes a nonionic surfactant, an anionic biosurfactant and a cosurfactant; The nonionic surfactant is fatty alcohol polyoxyethylene ether AEO-9, polyoxyethylene sorbitan monooleate or lactone type sophorolipid; The anionic biosurfactant is rhamnolipid; The co-surfactant is a small molecule alcohol, and the small molecule alcohol is triethylene glycol, n-butanol or propylene glycol; The oil is vegetable oil, and the vegetable oil is coconut oil; The mass ratio of the nonionic surfactant to the anionic biosurfactant is 1-4:1; The ratio of the total mass of the nonionic surfactant and the anionic biosurfactant to the mass of the co-surfactant is 1:2-5.

6. The microemulsion oil-displacing agent according to claim 5, characterized in that: The molecular formula of the polyoxyethylene sorbitan monooleate is C 46 H 52 N5O8P; The lactone-type sophorolipid is composed of hydrophilic sophorose and a hydrophobic part; the hydrophobic part is a saturated or unsaturated long-chain ω-hydroxy fatty acid.

7. The microemulsion oil-displacing agent according to claim 6, characterized in that: The hydrophobic portion is a saturated or unsaturated long chain omega-1 hydroxy fatty acid.

8. The microemulsion oil-displacing agent according to claim 5, characterized in that: The rhamnolipid is a biological metabolite produced by Pseudomonas.

9. The method for preparing the microemulsion oil-displacing agent according to any one of claims 5 to 8, characterized in that: The following steps are involved: The nonionic surfactant, the anionic biosurfactant, the co-surfactant and water are first mixed to obtain an aqueous phase; The water phase and the oil are mixed for a second time to obtain the microemulsion type oil displacing agent.

10. An oil-displacing nanoemulsion, characterized in that: It is prepared from the microemulsion oil-displacing agent according to any one of claims 5 to 8 or the microemulsion oil-displacing agent prepared by the preparation method according to claim 9 and water; the mass fraction of the microemulsion oil-displacing agent in the oil-displacing nanoemulsion is 0.2%.

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