Oilfield oil-displacing agent suitable for high-salinity oil reservoir exploitation and preparation method of oilfield oil-displacing agent

Abstract

The invention provides an oil-field oil-displacing agent suitable for high-salinity oil reservoir exploitation and a preparation method thereof. The oil-field oil-displacing agent comprises the following components in parts by weight: 20-30 parts of a first anionic surfactant, 3-8 parts of a second anionic surfactant, 2-6 parts of a nonionic surfactant, 2-5 parts of a zwitterionic surfactant and 51-73 parts of a solvent. The oilfield oil displacement agent provided by the invention is higher in efficiency and lower in price, and the oil displacement cost can be reduced. Moreover, the oil displacement agent for the oil field provided by the invention has good long-term stability at different oil reservoir temperatures, and has the advantages that the oil-water interfacial tension can still reach ultralow (namely 10 <-3 > mN / m) in a hypersalinity environment, the biodegradability is good, and the like.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry and relates to an oil displacement agent, in particular to an oilfield oil displacement agent suitable for exploitation of high-mineralization oil reservoirs and a preparation method thereof. Background Art

[0002] Oil is a viscous, dark brown liquid, known as the "blood of industry". Oil is stored in some areas of the upper crust. The main components are a mixture of various alkanes, cycloalkanes, and aromatic hydrocarbons. It is also a non-renewable natural resource. It plays an irreplaceable role in energy, chemical raw materials, and national defense strategic materials. The process of oil extraction and oil field development can be divided into three different stages: primary oil recovery, secondary oil recovery, and tertiary oil recovery. Both primary oil recovery and secondary oil recovery are oil recovery technologies that use physical methods. Among them, primary oil recovery is a self-flowing development that relies entirely on the natural energy of the bottom layer, and the average recovery is generally less than 15%. Secondary oil recovery refers to the oil recovery technology that uses water or gas injection to supplement energy externally after the completion of primary oil recovery, that is, after the formation energy is released, and its recovery rate is about 30%-40%. As secondary oil recovery approaches the late stage, the water content of the oil field produced fluid gradually increases accordingly, and the economic benefits of crude oil extraction are greatly reduced. After secondary oil recovery, people use different methods to further improve crude oil recovery rate. The new technologies they use are collectively called tertiary oil recovery technology, also known as enhanced oil recovery technology.

[0003] Tertiary oil recovery refers to the method of injecting chemicals into the ground to drive out crude oil, also known as enhanced oil recovery (EOR) method. There are many methods to improve oil recovery, mainly the following: injection of surfactants; injection of polymer-thickened water; injection of alkaline water drive; injection of CO2 drive; injection of alkali plus polymer drive; injection of inert gas drive; injection of hydrocarbon miscible drive; burning of oil layer; injection of steam drive, etc. Among them, surfactant drive is a type of chemical oil recovery technology with good recovery effect, wide application range and development potential. It has been widely used in most domestic oil fields. The most commonly used surfactants in oil recovery formulas at home and abroad are anionic sulfonates and carboxylates, followed by non-ionic and zwitterionic types, and the least used are cationic surfactants. When anionic surfactants are used as oil displacement combinations, they need to be used in combination with alkalis. Among them, heavy alkylbenzene sulfonates must be used in combination with strong alkalis, while petroleum sulfonates can be used in combination with weak alkalis. Although the presence of alkalis does play a certain role in providing recovery, such as the heavy alkylbenzene strong alkali system used in Daqing, which can increase the recovery by about 20% from the current application, the use of alkalis in the system will have a negative effect on the injection process and the treatment process of the produced fluid, such as causing serious scaling, which has a serious impact on the injection of displacement fluids and the treatment of produced fluids. At the same time, some mine tests in recent years have shown that the use of alkalis may cause scaling of oil wells, blockage of capillary channels, and even the scrapping of oil wells, because the alkalis may react with minerals in rocks or formation water to generate insoluble substances. At the same time, the existing surfactants have poor high temperature and salt resistance and low oil displacement efficiency.

[0004] At present, large oil fields such as Daqing, Shengli, Zhongyuan, Huabei and Dagang are in the middle and late stages of exploitation, and the output of some oil fields has shown a downward trend. Some oil fields cannot be exploited on a large scale due to the high development costs caused by harsh reservoir conditions (such as high mineralization of the storage environment).

[0005] Therefore, the development of surfactants suitable for exploitation of oil reservoirs with high mineralization and harsh environments is of great significance for increasing oil production and ensuring oil output. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an oilfield displacement agent suitable for exploitation of high-salinity oil reservoirs and a preparation method thereof. The oilfield displacement agent of the present invention has the ability to make the oil-water interfacial tension reach an ultra-low level (i.e., reaching 10 -3 mN / m), good biodegradability, etc.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The invention provides an oilfield displacing agent suitable for exploiting high-mineralization oil reservoirs. The oilfield displacing agent comprises, by weight, 20-30 parts of a first anionic surfactant, 3-8 parts of a second anionic surfactant, 2-6 parts of a nonionic surfactant, 2-5 parts of a zwitterionic surfactant and 51-73 parts of a solvent.

[0009] As a preferred embodiment of the present invention, the first anionic surfactant is sodium isooctyl polyether sulfate.

[0010] As a preferred embodiment of the present invention, the structural formula of the sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, wherein m is 3-6.

[0011] As a preferred embodiment of the present invention, the second anionic surfactant is sodium fatty alcohol ether sulfate.

[0012] As a preferred embodiment of the present invention, the structural formula of the sodium fatty alcohol ether sulfate is: 12 H 23 O(CH2CH2O)5SO3Na.

[0013] As a preferred embodiment of the present invention, the nonionic surfactant is isodecanol polyether.

[0014] As a preferred embodiment of the present invention, the structural formula of the isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 1-3.

[0015] As a preferred embodiment of the present invention, the zwitterionic surfactant is cocoamidopropyl betaine, and the solvent is water.

[0016] The present invention also provides a method for preparing the above-mentioned oilfield displacement agent suitable for exploitation of high-mineralization oil reservoirs. The preparation method comprises: under stirring conditions, adding a first anionic surfactant into a container, adding a second anionic surfactant, a nonionic surfactant, a zwitterionic surfactant and a solvent into the container, and stirring until they are colorless and transparent, so as to obtain the oilfield displacement agent suitable for exploitation of high-mineralization oil reservoirs.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1) The oil-displacing agent provided by the present invention is suitable for achieving ultra-low interfacial tension, and its interfacial tension can be maintained at an ultra-low state after a long time, and the oil production cost can also be reduced. The composite surfactant composition for oil-displacing agent for oil-field exploitation of high-mineralization oil reservoirs not only has good interfacial properties, but also has very good emulsifying properties.

[0019] 2) The oil field displacement agent provided by the present invention has higher efficiency and lower price, which can reduce the cost of oil displacement. In addition, the oil field displacement agent provided by the present invention has good long-term stability at different reservoir temperatures.

[0020] 3) The oil field displacement agent provided by the present invention can still make the oil-water interfacial tension reach ultra-low (i.e., reach 10 -3 mN / m), good biodegradability, etc. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] The invention provides an oilfield displacing agent suitable for exploiting high-mineralization oil reservoirs. The oilfield displacing agent comprises, by weight, 10-45 parts of a first anionic surfactant, 1-15 parts of a second anionic surfactant, 1-10 parts of a nonionic surfactant, 1-8 parts of a zwitterionic surfactant and 45-80 parts of a solvent.

[0023] In one embodiment of the present invention, the oilfield displacing agent comprises, by weight, 20-30 parts of a first anionic surfactant, 3-8 parts of a second anionic surfactant, 2-6 parts of a nonionic surfactant, 2-5 parts of a zwitterionic surfactant and 51-73 parts of a solvent.

[0024] In one embodiment of the present invention, the first anionic surfactant is sodium isooctyl polyether sulfate.

[0025] In one embodiment of the present invention, the structural formula of the sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, wherein m is 3-6.

[0026] In one embodiment of the present invention, the second anionic surfactant is sodium fatty alcohol ether sulfate.

[0027] In one embodiment of the present invention, the structural formula of the sodium fatty alcohol ether sulfate is: 12 H 23 O(CH2CH2O)5SO3Na.

[0028] In one embodiment of the present invention, the nonionic surfactant is isodecanol polyether.

[0029] In one embodiment of the present invention, the structural formula of the isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 1-3.

[0030] In one embodiment of the present invention, the zwitterionic surfactant is cocoamidopropyl betaine, and the solvent is water.

[0031] In the present invention, sodium isooctyl polyether sulfate reduces the interfacial tension between oil and water. Through its special molecular structure, sodium isooctyl polyether sulfate can significantly reduce the interfacial tension between oil and water, making it easier for oil droplets to be peeled off from the rock surface and dispersed into the water phase, thereby improving the recovery rate of crude oil; improving the wettability of oil layer rocks, making the oil layer change from oil-wet to hydrophilic, which is beneficial to the flow and recovery of crude oil; and being able to disperse crude oil into fine emulsion droplets to form a stable emulsion, which is convenient for subsequent treatment and transportation.

[0032] The molecular structure of sodium fatty alcohol ether sulfate can interact with the oil phase and the water phase at the same time, effectively removing dirt and impurities in the oil layer and keeping the oil layer clean. It can mix insoluble substances such as crude oil with water to form a stable emulsion and improve the fluidity of crude oil. The generated foam can wrap the oil droplets, increase the friction and flushing force of the washing process, and further improve the oil recovery effect.

[0033] Isodecyl alcohol polyether can penetrate into the tiny pores of oil layer rocks and strip crude oil from the rock surface; it helps the crude oil disperse into the water phase to form an emulsion that is easy to flow, maintains chemical stability during the oil recovery process, and is not easy to decompose or fail.

[0034] Cocamidopropyl betaine has low irritation to the skin and eyes and is suitable for oil field exploitation and other occasions where environmental protection is required. It can be well compatible with other surfactants to form a stable oil displacement system, can produce abundant foam and increase the viscosity of the system, which helps to improve the oil displacement effect. It can still maintain good performance in water containing hardness ions and is not easily affected by water quality.

[0035] The present invention uses a combination of multiple surfactants, and as the injected water enters the oil layer, it can quickly gather on the oil-water interface. Since the oilfield oil displacement agent of the present invention has super strong interfacial activity, it forms a layer of dispersion with oil and water under formation conditions. The dispersion is distributed between the oil phase and the water phase, and has the properties of both oil and water phases. The oil, water and oil displacement agent inside the dispersion are all nano-scale droplets. The dispersion itself can be miscible with oil or water in any proportion, and at the same time, it is only distributed on the oil-water interface under the condition of the coexistence of oil and water. Therefore, this property between oil and water can reduce the interfacial tension between the dispersion and oil or water to near zero, thereby greatly reducing the difference in capillary force, reducing the non-uniformity in the displacement process, increasing the swept surface of the displacement water, and improving the displacement efficiency.

[0036] Example 1

[0037] This embodiment provides an oilfield oil displacement agent suitable for exploitation of high-mineralization oil reservoirs, which includes, by weight: 25 parts of sodium isooctyl polyether sulfate, 5 parts of sodium fatty alcohol ether sulfate, 4 parts of isodecanol polyether, 3 parts of cocoamidopropyl betaine, and 63 parts of water.

[0038] Among them, the structural formula of sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na,m is 3.

[0039] The structural formula of sodium fatty alcohol ether sulfate is: 12 H 23 O(CH2CH2O)5SO3Na.

[0040] The structural formula of isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, n is 2.

[0041] Example 2

[0042] This embodiment provides an oilfield oil displacement agent suitable for exploitation of high-mineralization oil reservoirs, which includes, by weight: 20 parts of sodium isooctyl polyether sulfate, 5 parts of sodium fatty alcohol ether sulfate, 4 parts of isodecanol polyether, 3 parts of cocoamidopropyl betaine, and 68 parts of water.

[0043] Among them, the structural formula of sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, where m is 6.

[0044] The structural formula of sodium fatty alcohol ether sulfate is: 12 H23 O(CH2CH2O)5SO3Na.

[0045] The structural formula of isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 3.

[0046] Example 3

[0047] This embodiment provides an oilfield oil displacement agent suitable for exploitation of high-mineralization oil reservoirs, which includes, by weight: 22 parts of sodium isooctyl polyether sulfate, 5 parts of sodium fatty alcohol ether sulfate, 4 parts of isodecanol polyether, 3 parts of cocoamidopropyl betaine, and 73 parts of water.

[0048] Among them, the structural formula of sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, where m is 3.

[0049] The structural formula of sodium fatty alcohol ether sulfate is: 12 H 23 O(CH2CH2O)5SO3Na.

[0050] The structural formula of isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 1.

[0051] Comparative Example 1

[0052] This comparative example provides an oilfield oil displacement agent, which comprises, by weight: 25 parts of sodium isooctyl polyether sulfate, 5 parts of sodium fatty alcohol ether sulfate, 4 parts of isodecanol polyether, and 66 parts of water.

[0053] Among them, the structural formula of sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, where m is 6.

[0054] The structural formula of sodium fatty alcohol ether sulfate is: 12 H 23 O(CH2CH2O)5SO3Na.

[0055] The structural formula of isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 3.

[0056] Comparative Example 2

[0057] This comparative example provides an oilfield oil displacement agent, which comprises, by weight: 25 parts of sodium isooctyl polyether sulfate, 4 parts of isodecanol polyether, 3 parts of cocoamidopropyl betaine, and 68 parts of water.

[0058] Among them, the structural formula of sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, where m is 6.

[0059] The structural formula of isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 3.

[0060] The oil-water interfacial tension test was performed on the oilfield displacement agent suitable for exploitation of high-mineralization oil reservoirs obtained in Examples 1-3 and the oilfield displacement agent obtained in Comparative Examples 1-2. The results are shown in Table 1.

[0061] Test method for oil-water interfacial tension: Use high-mineralization water with a mineralization of 20,000 mg / kg to prepare a sample solution with an active ingredient content of 1%, and use a TX-500C rotating drop interfacial tension meter to test the interfacial tension between the sample solution and n-decane.

[0062] Table 1. Oil-water interfacial tension test results

[0063]

[0064] As can be seen from Table 1, as the content of sodium isooctyl polyether sulfate increases, the oil-water interfacial tension is lower. Comparative Example 1 does not add cocamidopropyl betaine, and Comparative Example 2 does not add sodium fatty alcohol ether sulfate, so its oil-water interfacial tension is higher than that of Examples 1-3.

[0065] It can be seen that the oil field displacement agent provided by the present invention can still make the oil-water interfacial tension reach an ultra-low level (i.e., reaching 10 -3 mN / m), good biodegradability, etc.

[0066] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An oil field oil displacement agent suitable for exploitation of high mineralization oil reservoirs, characterized in that: The oilfield oil displacement agent comprises, by weight, 20-30 parts of a first anionic surfactant, 3-8 parts of a second anionic surfactant, 2-6 parts of a nonionic surfactant, 2-5 parts of a zwitterionic surfactant and 51-73 parts of a solvent.

2. The oil field oil displacement agent suitable for exploitation of high-mineralization oil reservoirs according to claim 1, characterized in that: The first anionic surfactant is sodium isooctyl polyether sulfate.

3. The oil field oil displacement agent suitable for exploitation of high-mineralization oil reservoirs according to claim 2, characterized in that: The structural formula of the sodium isooctyl polyether sulfate is: C8H 17 O(CH2(CH3)CHO)2(CH2CH2O) m SO3Na, wherein m is 3-6.

4. The oil field oil displacement agent suitable for exploitation of high-mineralization oil reservoirs according to claim 1, characterized in that: The second anionic surfactant is sodium fatty alcohol ether sulfate.

5. The oil field oil displacement agent suitable for exploitation of high-mineralization oil reservoirs according to claim 4, characterized in that: The structural formula of the sodium fatty alcohol ether sulfate is: 12 H 23 O(CH2CH2O)5SO3Na.

6. The oil field oil displacement agent suitable for exploitation of high-mineralization oil reservoirs according to claim 1, characterized in that: The nonionic surfactant is isodecanol polyether.

7. The oil-displacing agent suitable for exploitation of high-mineralization oil reservoirs according to claim 6, characterized in that: The structural formula of the isodecanol polyether is C 10 H 21 O(CH2(CH3)CHO) n (CH2CH2O)9H, wherein n is 1-3.

8. The oil field oil displacement agent suitable for exploitation of high-mineralization oil reservoirs according to claim 1, characterized in that: The zwitterionic surfactant is cocoamidopropyl betaine, and the solvent is water.

9. A method for preparing an oilfield oil displacement agent suitable for exploitation of high-mineralization oil reservoirs as claimed in any one of claims 1 to 8, characterized in that: The preparation method comprises: adding a first anionic surfactant into a container under stirring conditions, adding a second anionic surfactant, a nonionic surfactant, a zwitterionic surfactant and a solvent into the container, stirring until a light yellow transparent uniform liquid is obtained, and obtaining an oilfield oil displacement agent suitable for exploitation of high-mineralization oil reservoirs.

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