Emulsion oil displacement composition and application thereof in low-permeability reservoir

Abstract

The invention provides an emulsion oil displacement composition and application thereof in a low-permeability reservoir. The emulsion oil displacement composition comprises an extension type surfactant, a betaine type surfactant, an additive and water, according to the emulsion oil displacement composition, an oil displacement system with controllable emulsion strength can be developed by utilizing interface mixed adsorption, interface vacancy size adjustment and enhancement of the synergistic effect with crude oil active components, ultralow interfacial tension and emulsifying performance are achieved at the same time, the cost is controlled within 1.050 thousand yuan / ton, and the emulsion oil displacement composition has wide application prospects in low-permeability oil reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of oil displacement, in particular to an emulsified oil displacement composition and application thereof in low-permeability oil reservoirs. Background Art

[0002] With the continuous improvement of tertiary oil recovery technology and the continuous expansion of its scale, the research object of improving oil recovery has gradually shifted from conventional oil reservoirs to low-permeability oil reservoirs with poor physical properties. Compared with ordinary oil reservoirs, the smaller pore size and larger specific surface area of ​​low-permeability oil reservoirs have led to serious challenges for traditional chemical flooding systems. The adsorption and retention of surfactant-polymer binary compound systems have prevented the original technical advantages of the flooding formula from being effectively utilized, and it faces the bottleneck of "no injection and no production". At this time, in addition to the basic temperature and salt resistance, surfactants also need to solve the problems of oil film stripping and pressure reduction and injection increase based on their own wetting control; by reducing the ability of oil-water interfacial tension, the purpose of increasing capillary bundles, improving emulsification strength, and strengthening the start-up migration can be achieved; with the help of a certain membrane strength, the mobility ratio can be controlled, and the viscosity of the bulk phase or front oil wall can be increased, and finally a substantial increase in oil recovery can be achieved.

[0003] In other words, the construction of the optimal chemical flooding system needs to consider factors such as pore structure, reservoir environment and oil phase properties. For pore structure, the permeability and heterogeneity of reservoir rock pores constrain the sweep and seepage capacity of the displacement fluid, which is a prerequisite for formula construction. The reservoir environment mainly places requirements on the stability of the displacement fluid. The high temperature and high salt reservoir environment will cause the salting out of ionic surfactants and make non-ionic surfactants turbid, which is a necessary condition for formula construction. The oil phase properties mainly affect the interfacial behavior of surfactant molecules. Different types of crude oil active components can produce synergistic or anti-synergistic effects with surfactant molecules at the interface, regulating the tightness of the adsorption film, which is an important condition for formula construction.

[0004] Laboratory characterization methods for chemical flooding to enhance oil recovery mainly include sand filling, CT scanning imaging, nuclear magnetic resonance imaging, 2 Spectra and core displacement, etc., all of which simulate the rock composition and pore structure characteristics well, establish a connection between laboratory characterization and actual application in the oil field, and increase the reliability of chemical flooding formula screening. However, this type of method generally focuses on the concept of "quantity", and there is relatively little feedback on the start-up and migration of crude oil and emulsions in the pores. The provision of information such as the occurrence form and distribution state of the remaining oil is also lacking, which is not conducive to the theoretical design of chemical flooding systems. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides an emulsified oil recovery composition and its use in low permeability oil reservoirs. The emulsified oil recovery composition has a high efficiency in oil recovery effect according to the reservoir environment, pore structure and crude oil properties, and the cost is controlled within RMB 10,500 per ton, and has broad application prospects in low permeability oil reservoirs.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an emulsified oil displacement composition, comprising an extended surfactant, a betaine surfactant, an additive and water.

[0008] The present invention reveals the molecular action mechanism of surfactant interface and bulk phase, deepens the synergistic effect law of oil displacement system, takes betaine-type surfactant with excellent ability to increase the strength of oil-water interface film as the main agent, and uses extended surfactant and additives as auxiliary agents, and develops a high-efficiency and low-cost oil displacement system according to the reservoir environment, pore structure and crude oil properties.

[0009] The present invention is based on the quantitative characterization of the surface and interfacial properties of the emulsified oil displacement system at a macroscopic scale, clarifies the relationship between the system's emulsification regulation ability and physical and chemical parameters such as interfacial tension and membrane strength, and verifies the oil displacement effect of the above-mentioned emulsified oil displacement composition at a macroscopic scale.

[0010] Moreover, based on the quantitative characterization of the surface and interfacial properties of the emulsification-regulated oil recovery system at the microscopic scale, the connection between the characterization at normal temperature, pressure and macroscopic scale and the actual application effects at high temperature, high pressure and confined space is clarified, the key technical indicators of emulsification regulation are revealed, and the excellent oil recovery effect of the above-mentioned oil recovery composition is verified at the microscopic scale.

[0011] Preferably, the extended surfactant is a novel surfactant formed by inserting polyoxypropylene between the alkyl chain and the hydrophilic group of the initial surfactant.

[0012] The present invention uses an extended surfactant, which is temperature-resistant and salt-resistant and can reduce the oil-water interfacial tension to an ultra-low level. It is combined with a betaine-type surfactant and an additive to exert a synergistic effect and significantly improve the oil recovery efficiency.

[0013] Preferably, the initial surfactant in the extending surfactant comprises an anionic nonionic surfactant.

[0014] Preferably, the anionic nonionic surfactant comprises any one of alkyl alcohol ether carboxylates, alkyl alcohol sulfates or alkyl alcohol polyoxypropylene polyoxyethylene carboxylates or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of alkyl alcohol ether carboxylates and alkyl alcohol sulfates, a combination of alkyl alcohol ether carboxylates and alkyl alcohol polyoxypropylene polyoxyethylene carboxylates, and a combination of alkyl alcohol polyoxypropylene polyoxyethylene carboxylates and alkyl alcohol sulfates.

[0015] Preferably, the number of added PO groups in the embedded segment of the extended surfactant is 2 to 6, for example, 2, 3, 4, 5 or 6.

[0016] The present invention preferably controls the addition number of the embedded segments to be between 2 and 6, which can better balance the water-oil group ratio in the extended surfactant and has a better oil displacement effect.

[0017] Preferably, the betaine-type surfactant comprises arylalkyl long-chain sulfobetaine.

[0018] Preferably, the mass ratio of the extending surfactant to the betaine surfactant in the emulsified oil displacement composition is (3-10):1, for example, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] In the present invention, when the mass ratio of the extendable surfactant to the betaine surfactant is too high, there is a problem of poor emulsion stability. When the mass ratio of the extendable surfactant to the betaine surfactant is too low, there is a problem of blocking pore throats and affecting the migration of the emulsion.

[0020] Preferably, the mass fraction of the extending surfactant in the emulsified oil displacement composition is 0.2-0.28%, for example, it can be 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28% or 0.28%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In the present invention, when the amount of the extending surfactant is too much, there are problems of difficulty in dissolution and low cost performance; when the amount of the extending surfactant is too little, there are problems of poor surface and interface performance and low oil displacement efficiency.

[0022] Preferably, the mass fraction of the additive in the emulsified oil displacement composition is 0.01-0.3%, for example, it can be 0.01%, 0.05%, 0.08%, 0.11%, 0.14%, 0.18%, 0.21%, 0.24%, 0.27% or 0.3%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] In the present invention, when the amount of the additive is too much, there is a problem of affecting the effect of the surfactant or even causing the surfactant to fail; when the amount of the additive is too little, there is a problem of obvious adsorption loss during the oil displacement process and limited efficacy.

[0024] Preferably, the additive comprises any one or a combination of at least two of nanoparticles, alkaline substances or neutral salts, wherein typical but non-limiting combinations are a combination of nanoparticles and alkaline substances, a combination of nanoparticles and neutral salts, and a combination of neutral salts and alkaline substances.

[0025] The present invention preferably uses the above-mentioned additives. Compared with other additives such as acidic salts and metal substances, the above-mentioned substances have excellent temperature and salt resistance and good biodegradability. At the same time, they can promote the surfactant's ability to start stripping oil films and other functions. They can interact with betaine-type surfactants and extended surfactants to improve oil recovery efficiency.

[0026] Preferably, when the additive is nano black card, the content of nano black card in the emulsified oil displacement composition is 0.01-0.2%, for example, it can be 0.01%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18% or 0.2%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] Preferably, the nanoparticles include nano black card.

[0028] The present invention has no particular limitation on the size of the nanoparticles. For example, the particle size of the nanoparticles may be a flake of 5×300×300 nm.

[0029] Preferably, when the additive is an alkaline substance, the content of the alkaline substance in the emulsified oil displacement composition is 0.01-0.3%, for example, it can be 0.01%, 0.05%, 0.08%, 0.11%, 0.14%, 0.18%, 0.21%, 0.24%, 0.27% or 0.3%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] Preferably, the alkaline substance comprises sodium carbonate and / or sodium bicarbonate.

[0031] Preferably, when the additive is a neutral salt, the content of the neutral salt in the emulsified oil displacement composition is 0.1-0.5%, for example, it can be 0.1%, 0.15%, 0.19%, 0.24%, 0.28%, 0.33%, 0.37%, 0.42%, 0.46% or 0.5%, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0032] Preferably, the neutral salt comprises sodium chloride.

[0033] In a second aspect, the present invention provides a use of the emulsified oil displacement composition described in the first aspect for oil displacement in a low permeability oil reservoir.

[0034] Preferably, the total mineralization of water in the low permeability oil reservoir is 15000-30000 mg / L, for example, it can be 15000 mg / L, 16000 mg / L, 18000 mg / L, 20000 mg / L, 21000 mg / L, 23000 mg / L, 25000 mg / L, 26000 mg / L, 28000 mg / L or 30000 mg / L, but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0035] Preferably, the viscosity of the oil in the low permeability reservoir is 5 to 10 cp, for example, it may be 5 cp, 5.6 cp, 6.2 cp, 6.7 cp, 7.3 cp, 7.8 cp, 8.4 cp, 8.9 cp, 9.5 cp or 10 cp, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0036] Preferably, the permeability of the low permeability reservoir is 0.01-0.05 μm 2 , for example, it can be 0.01 μm 2 , 0.015μm 2 、0.019μm 2 , 0.024μm 2 , 0.028μm 2 , 0.033μm 2 , 0.037μm 2 、0.042μm 2 、0.046μm 2 or 0.05μm 2 The above values ​​are not limited to the above values, and other values ​​not listed in the above values ​​are also applicable.

[0037] The emulsified oil displacement composition provided by the present invention can be preferably used for oil recovery in low-permeability oil reservoirs.

[0038] Preferably, the reservoir temperature of the low permeability oil reservoir is 65-80°C, for example, it can be 65°C, 67°C, 69°C, 70°C, 72°C, 74°C, 75°C, 77°C, 79°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] (1) The emulsified flooding composition provided by the present invention adopts molecular design means, by changing the number of PO groups and molecular weight, using an extended surfactant with excellent emulsification performance, utilizing interfacial mixed adsorption, adjusting the size of interfacial vacancies, and enhancing the synergistic effect with the active components of crude oil, to develop an emulsified flooding combination with controllable emulsification strength, achieve both ultra-low interfacial tension and emulsification performance, and control the cost within RMB 10,500 / ton, which has broad application prospects;

[0041] (2) The emulsified oil recovery composition provided by the present invention has excellent oil recovery efficiency for low permeability oil reservoirs. The oil recovery rate of microscopic visualization oil recovery test can reach more than 89%, and the oil recovery rate of core displacement can reach more than 41%. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a test diagram of the droplet aggregation ability of the emulsified oil displacement composition provided in Example 1 of the present invention in a microscopic visualized oil displacement test.

[0043] Figure 2 This is a microscopic visualized oil displacement effect diagram of the emulsified oil displacement composition provided in Example 1 of the present invention.

[0044] Figure 3 This is a diagram of pressure data processing at multiple pressure measuring points of the emulsified oil displacement composition provided in Example 1 of the present invention during core displacement.

[0045] Figure 4 It is a one-dimensional displacement wave degree diagram of the emulsified oil displacement composition provided in Example 1 of the present invention in core displacement. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0047] The present invention is further described in detail below. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0048] Examples 1 to 12 and Comparative Examples 1 to 6 provide different oil displacement compositions, and the compositions and proportions are shown in Table 1.

[0049] Table 1

[0050]

[0051] The structural formula of S126 in Table 1 is as follows:

[0052]

[0053] In Table 1, "Same as 1" means that the same scheme as Example 1 is adopted.

[0054] The octadecyl dimethyl mixed betaine in Table 1 is the octadecyl dimethyl mixed betaine prepared in Example 1 of CN108531157A.

[0055] In order to verify the advantages of the emulsified oil displacement composition of the present application, the various properties of the emulsified oil displacement composition were comprehensively tested by the following method. Before the experiment, the diluted crude oil was injected into different types of glass models at a rate of 20 μL / min until the crude oil filled the entire glass model and there were no bubbles in the pore throats. In the experiment, different types of surfactant solutions were injected into the glass model at a constant injection rate of 0.1 μL / min, and the whole process of crude oil displacement in the glass model (hydrophilic simulation, hydrophobic simulation and heterogeneity) was recorded by the video mode of the microscope, and the pressure changes during the displacement process were accurately recorded by the microfluidic uProcess software. The results are shown in Table 2.

[0056] Table 2

[0057]

[0058]

[0059] The droplet aggregation ability test of the emulsified oil displacement composition in Example 1 is shown in the figure Figure 1 As shown, from Figure 1 It can be seen that Example 1 has a suitable interfacial film strength and the droplets do not coalesce quickly.

[0060] The migration mode W in Table 2 is a qualitative representation of the ability of diluted crude oil to start and migrate in the glass model, including overall migration, wire-drawing migration, drop-like migration, emulsified migration, etc. Among them, the ultra-low oil-water interfacial tension system often migrates in the form of wire drawing and drop-like migration, while the system with relatively high tension generally migrates in the form of an overall migration.

[0061] The amount of film-like remaining oil M refers to the classification of the remaining oil in the glass model after the displacement is completed. The remaining oil with an oil film thickness less than 1 / 3 of the pore throat diameter is defined as film-like remaining oil. The amount of film-like remaining oil is a measure of the ability of the emulsification and flooding system to strip the oil film. The smaller the amount, the better the ability to strip the oil film.

[0062] The microscopic contact angle C is another representation of the system's ability to strip oil film. The contact angle distribution statistics of the residual oil in the glass model after the displacement are performed. The larger the contact angle, the stronger the ability to strip oil film. Here it refers to the oil phase contact angle.

[0063] Pressure P refers to the instantaneous pressure generated when the emulsified flooding system breaks through and enters the glass model of saturated oil. The magnitude of the pressure is closely related to the interfacial film strength and interfacial tension. For the emulsified flooding system with high film strength and high interfacial tension formed with the diluted crude oil, the breakthrough pressure value is relatively high, otherwise it is relatively low. The test results in Example 1 are as follows: Figure 2 As shown, from Figure 2 It can be seen that Example 1 has an excellent oil displacement effect.

[0064] The oil displacement efficiency K is the most intuitive quantitative description of the oil displacement effect of different types of emulsified displacement systems in microscopic visualization tests. It is the quotient of the change in oil phase pixels during the entire experiment and the initial pixels. The larger the ratio, the more pore crude oil is displaced and the better the oil displacement effect.

[0065] From Table 2, we can see the following points:

[0066] (1) It can be seen from Examples 1 to 12 that the emulsified oil displacement composition provided by the present invention has an excellent oil displacement effect, and its oil displacement efficiency in the microscopic visualization test is above 49%, preferably up to 92%, and its oil displacement efficiency in the core displacement is above 17%, preferably up to 45%;

[0067] (2) It can be seen from Example 1 and Comparative Examples 1 to 6 that the various combinations and contents of the emulsified oil displacement composition provided by the present invention are very critical, and the components cooperate with each other to significantly improve the oil displacement efficiency. Furthermore, it can be seen from Example 1 and Examples 6 to 12 that the present invention has a better oil displacement effect by selecting the contents of the various components and the substances within the preferred range.

[0068] Application of the emulsified flooding composition in Example 1 in tertiary oil recovery

[0069] The oil displacement experiment is based on the petroleum industry standard SY / T 6424-2014. According to the pressure data at the end of water flooding, the swept volume of one-dimensional core chemical flooding is calculated: first, the pressure at both ends of the core at the end of the subsequent water flooding of chemical flooding is virtually extended, and virtual pressure points with the same value as the core endpoints are assigned at positions with equal spacing between pressure measuring points outside the core, and Akima interpolation is performed on multiple pressure measuring points; secondly, the pressure after interpolation is derived to obtain the pressure gradient distribution of the core at the end of the subsequent water flooding of chemical flooding; finally, the pressure gradient is integrated, and 50% of the integrated area of ​​the pressure gradient is taken to represent the swept volume. This quantitative swept volume value effectively includes the system crossflow sweep, the system main body sweep position and the system retention degree. For example, in Example 1, the effect of core displacement is as follows: Figures 3-4 As shown, from Figures 3-4 It can be seen that the formula of Example 1 has good startup and stripping capabilities of the original pores, and at the same time has a certain sweep efficiency. The interfacial film strength is not too high, which can ensure the smooth injection and displacement of the oil displacement composition, and the core displacement effect is good. The oil displacement efficiency of the core displacement in other embodiments and comparative examples is shown in Table 2, represented by R.

[0070] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An emulsified oil displacement composition, characterized in that: The emulsified oil displacement composition comprises an extending surfactant, a betaine surfactant, an additive and water.

2. The emulsified oil displacement composition according to claim 1, characterized in that The extended surfactant is a new type of surfactant formed by inserting polyoxypropylene between the alkyl chain and the hydrophilic group of the initial surfactant; Preferably, the initial surfactant in the extending surfactant comprises an anionic-nonionic surfactant; Preferably, the anionic nonionic surfactant includes any one or a combination of at least two of alkyl alcohol ether carboxylates, alkyl alcohol sulfates or alkyl alcohol polyoxypropylene polyoxyethylene carboxylates; Preferably, the number of additions of the embedded segment in the extended surfactant is 2 to 6 PO groups.

3. The emulsified oil displacement composition according to claim 1 or 2, characterized in that The betaine-type surfactant includes arylalkyl long-chain sulfobetaine.

4. The emulsified oil displacement composition according to claim 1, characterized in that The mass ratio of the extending surfactant to the betaine surfactant in the emulsified oil displacement composition is (3-10):1; Preferably, the mass fraction of the extending surfactant in the emulsified oil displacement composition is 0.2-0.28%.

5. The emulsified oil displacement composition according to claim 1, characterized in that The mass fraction of the additive in the emulsified oil displacement composition is 0.01-0.3%.

6. The emulsified oil displacement composition according to claim 1, characterized in that: The additive includes any one of nanoparticles, alkaline substances or neutral salts, or a combination of at least two of them.

7. The emulsified oil displacement composition according to claim 6, characterized in that: When the additive is nano black card, the content of nano black card in the emulsified oil displacement composition is 0.01-0.2%; Preferably, the nanoparticles include nano black card.

8. The emulsified oil displacement composition according to claim 6, characterized in that: When the additive is an alkaline substance, the content of the alkaline substance in the emulsified oil displacement composition is 0.01 to 0.3%; Preferably, the alkaline substance comprises sodium carbonate and / or sodium bicarbonate; Preferably, when the additive is a neutral salt, the content of the neutral salt in the emulsified oil displacement composition is 0.1 to 0.5%; Preferably, the neutral salt comprises sodium chloride.

9. Use of the emulsified oil displacement composition according to any one of claims 1 to 8 for oil displacement in a low permeability oil reservoir.

10. The use according to claim 9, characterized in that The total mineralization of water in the low-permeability oil reservoir is 15,000 to 30,000 mg / L; Preferably, the viscosity of the oil in the low permeability reservoir is 5 to 10 cp; Preferably, the permeability of the low permeability reservoir is 0.01 to 0.05 μm. 2 ; Preferably, the reservoir temperature of the low permeability oil reservoir is 65-80°C.

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