Preparation method of temperature-resistant nanoemulsion and application of temperature-resistant nanoemulsion in imbibition oil displacement of shale oil reservoir

Abstract

The present application belongs to the technical field of oil and gas exploitation and oil field chemistry, and relates to a preparation method of a temperature-resistant nanoemulsion and application of the nanoemulsion in shale oil reservoir imbibition oil displacement. The present application prepares an oil-water mixture by taking D-limonene as an oil phase and a sodium chloride aqueous solution as an aqueous phase; mixes an amido propyl betaine zwitterionic surfactant, an alpha-olefin sulfonate anionic surfactant and an organic alcohol cosurfactant to serve as an emulsifier; adds the emulsifier drop by drop into the oil-water mixture, continuously stirs, until the mixture becomes a homogeneous transparent phase, namely a homogeneous microemulsion; and adds water into the microemulsion, fully stirs and dilutes to obtain the nanoemulsion. The nanoemulsion prepared by the present application has ultralow interfacial tension, strong wetting reversal capacity and high-temperature thermal stability, and is suitable for shale oil imbibition oil displacement for enhanced oil recovery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas exploitation and oil field chemistry, and relates to a preparation method of a temperature-resistant nanoemulsion and application of the temperature-resistant nanoemulsion in osmotic oil displacement of shale oil reservoirs. BACKGROUND

[0002] As an important unconventional oil and gas resource, shale oil occupies an important position in the global energy structure and has gradually become an important oil and gas resource replacement site. With the application and promotion of the "long horizontal section horizontal well + multi-stage segmented hydraulic fracturing" technology, the initial development of the domestic shale oil industry has been realized. However, shale oil reservoirs differ greatly from conventional reservoirs in terms of reservoir characteristics, fluid characteristics, etc.; the reservoir space is a coexistence of nanoscale pores and microfractures; at the same time, the rock surface is oil-wet, and shale oil is mostly in adsorbed state. After fracturing, the permeability of the reformed area can be greatly improved, but problems such as high production decline rate and low predicted recovery rate still exist, and how to supplement the formation energy and improve the displacement efficiency has become the key to improving the recovery of shale oil. Practice has shown that the conventional water injection and swallowing energy supply mode is prone to fracture water breakthrough, and it is difficult to establish an effective displacement system. However, the carbon dioxide energy supply and repeated fracturing energy storage technology has the advantages of high energy supply efficiency, but reservoir conditions and economic benefits are important constraints.

[0003] In recent years, osmotic oil displacement has attracted industry attention due to its simple injection technology, low operating cost and good oil increment effect. Osmosis includes spontaneous osmosis and forced osmosis, the former actively intervenes only through capillary force, and the latter completes osmosis under the action of external force. The dispersed phase size of nanoemulsion is small, the emulsion system is stable, the oil-water interfacial tension is low, the rock wettability can be changed, it is easy to enter the pore throat and reduce the injection pressure, and it also has a good solubilizing effect on crude oil, and has achieved wide application in osmotic oil displacement. However, shale reservoirs are buried deep, and the formation temperature is generally high, such as the formation temperature in Jiyang Sag and Daqing Gulong is above 100℃, 130-200℃ and 100-120℃, respectively, and the temperature in the middle part of Jimsar Lucaogou Formation is as high as 92℃. Existing research has shown that as the temperature increases, the nanoemulsion particle size becomes larger, causing the emulsion to coalesce, and the stability becomes poor. Therefore, the development of temperature-resistant nanoemulsion is of great significance to improve the recovery of shale oil. SUMMARY

[0004] In view of the problem of emulsion coalescence and poor stability of nanoemulsion under high temperature conditions, the present application constructs a microemulsion-nanoemulsion conversion system suitable for osmotic oil displacement of high-temperature shale oil reservoirs through the synergistic effect of multiple components. A mixture of D-limonene and an aqueous sodium chloride solution is used as the basis, and an amido propyl betaine zwitterionic surfactant, αThe synergism of olefin sulfonate anionic surfactant and organic alcohol co-surfactant forms a homogeneous microemulsion with interface regulation ability and high temperature thermal stability; after dilution by adding water, the nanoemulsion that can meet the needs of different concentrations can be obtained by dynamic interface reorganization. Through ultra-low interfacial tension driving, the emulsification and dispersion of crude oil are realized, the wettability is reversed to enhance the water phase imbibition capacity, and the strong thermal stability guarantees the long-term effect at high temperature. From the three dimensions of interface regulation, wettability modification and thermal stability, an efficient and reliable solution for high temperature shale oil reservoir imbibition flooding is provided.

[0005] The technical solution of the present application to solve the above technical problems is as follows: a preparation method of a temperature-resistant nanoemulsion and its application in shale oil reservoir imbibition flooding, comprising the following steps:

[0006] Step one: prepare an oil-water mixture with D-limonene as the oil phase and sodium chloride aqueous solution as the water phase;

[0007] Step two: mix amido propyl betaine zwitterionic surfactant, α -olefin sulfonate anionic surfactant and organic alcohol co-surfactant as emulsifiers;

[0008] Step three: add the emulsifiers in step two dropwise into the oil-water mixture and continuously stir until the mixture becomes a homogeneous transparent phase, which is a homogeneous microemulsion;

[0009] Step four: add water to the microemulsion in step three, and after sufficient stirring and dilution, a nanoemulsion is obtained;

[0010] Further, the mass ratio of the oil phase to the water phase in step one is 4:6~6:4, and the mass concentration of the sodium chloride aqueous solution is 6%~12%; the amido propyl betaine zwitterionic surfactant, α The mass ratio of the olefin sulfonate anionic surfactant to the organic alcohol co-surfactant is 0.25:0.75:1~0.75:0.25:2; the mass ratio of the dilution water to the microemulsion in step four can be adjusted according to the use requirements;

[0011] Further, the amido propyl betaine zwitterionic surfactant includes one or more than two combinations of lauryl amido propyl betaine, cocamide propyl betaine, palmitamide propyl betaine and oleamide propyl betaine; the α The olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium salts of C 12 ~C 18 olefin sulfonate; the organic alcohol co-surfactant includes one or more than two combinations of n-butanol, n-pentanol and iso-pentanol. α

[0012] ​The application further provides application of the nanoemulsion prepared by the preparation method to oil displacement of a shale oil reservoir, the mass concentration of the nanoemulsion is 0.2% to 0.5%, and the formation temperature of the shale oil reservoir is higher than 120 DEG C and the core permeability is less than 1.0 mD.

[0013] The application has the following beneficial effects:

[0014] The application constructs a stable microemulsion-nanoemulsion conversion system through synergistic effect of multiple components, the prepared nanoemulsion has ultralow interfacial tension, strong wetting reverse ability and high-temperature thermal stability, overcomes the problems of emulsion coalescence and poor stability of the nanoemulsion in a high-temperature shale oil reservoir, provides a more efficient and reliable solution for oil displacement of the high-temperature shale oil reservoir, conforms to social and economic benefits, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 a is interfacial tension between the nanoemulsion with different concentrations and kerosene at room temperature;

[0016] Figure 1 b is interfacial tension between the nanoemulsion with a mass concentration of 0.3% and kerosene at different temperatures;

[0017] Figure 2 is the contact angle of a core slice before and after soaking and aging in the nanoemulsion with a mass concentration of 0.3%;

[0018] Figure 3 is the state characteristics of the nanoemulsion with a mass concentration of 0.3% at different standing times;

[0019] Figure 4 is the oil displacement capacity of the nanoemulsion with a mass concentration of 0.3% in a shale core at different injection amounts. DETAILED DESCRIPTION

[0020] The principle and characteristics of the application are described below, and the examples are only used to explain the application and not used to limit the scope of the application.

[0021] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the application can be purchased from the market or can be prepared by existing methods.

[0022] The application provides a preparation method of a temperature-resistant nanoemulsion and application of the nanoemulsion to oil displacement of a shale oil reservoir, and the method comprises the following steps:

[0023] Step one: preparing an oil-water mixture by taking D-limonene as an oil phase and a sodium chloride aqueous solution as an aqueous phase; ​​

[0024] Step 2: Add amamidopropyl betaine-type amphoteric surfactants, α - An olefin sulfonate anionic surfactant and an organic alcohol co-surfactant are mixed and used as emulsifiers;

[0025] Step 3: Add the emulsifier from Step 2 dropwise to the oil-water mixture and stir continuously until the mixture becomes a homogeneous transparent phase, which is a homogeneous microemulsion.

[0026] Step 4: Add water to the microemulsion from Step 3, and after thorough stirring and dilution, it becomes a nanoemulsion;

[0027] Furthermore, in step one, the mass ratio of the oil phase to the aqueous phase is 4:6 to 6:4, and the mass concentration of the sodium chloride aqueous solution is 6% to 12%; amphoteric surfactants such as amamidopropyl betaine are used. α - The mass ratio of olefin sulfonate anionic surfactant to organic alcohol co-surfactant is 0.25:0.75:1 to 0.75:0.25:2; the mass ratio of dilution water to microemulsion in step four can be adjusted according to usage requirements;

[0028] Further, the amamidopropyl betaine amphoteric surfactant includes one or more of lauramidopropyl betaine, cocamidopropyl betaine, palmitopropyl betaine, and oleamidopropyl betaine; α -Olefin sulfonate anionic surfactants include those with a carbon chain length of C0. 12 ~C 18 of α -One or more of sodium olefin sulfonate, magnesium, and potassium salts; the organic alcohol co-surfactant includes one or more of n-butanol, n-pentanol, and isopentanol.

[0029] The present invention also provides an application of the nanoemulsion prepared by the above preparation method in the percolation displacement of shale oil reservoirs, wherein the mass concentration of the nanoemulsion is 0.2%~0.5%, the formation temperature of the shale oil reservoir is higher than 120℃, and the core permeability is less than 1.0 mD.

[0030] Example 1: Based on a mixture of D-limonene and sodium chloride aqueous solution, the mixture was prepared using the amphoteric surfactant cocamidopropyl betaine and the anionic surfactant... α - Sodium olefin sulfonate (carbon chain length is C) 12 ~C 14 The synergistic effect of n-butanol, an organic alcohol co-surfactant, and other components forms a homogeneous microemulsion with interfacial control capabilities and high-temperature thermal stability. After dilution, nanoemulsions meeting different concentration requirements can be obtained through dynamic interfacial recombination. The specific implementation steps are as follows:

[0031] Step 1: Prepare an oil-water mixture using D-limonene as the oil phase and sodium chloride aqueous solution as the aqueous phase, wherein the mass ratio of the oil phase to the aqueous phase is 5:5, and the mass concentration of the sodium chloride aqueous solution is 10%.

[0032] Step 2: Add the amphoteric surfactant cocamidopropyl betaine and the anionic surfactant... α - Sodium olefin sulfonate (carbon chain length is C) 12 ~C 14 The organic alcohol co-surfactant n-butanol is mixed in a mass ratio of 1:1:2 and used as an emulsifier.

[0033] Step 3: Add the emulsifier from Step 2 dropwise to the oil-water mixture and stir continuously until the mixture becomes a homogeneous transparent phase, which is a homogeneous microemulsion.

[0034] Step 4: Add water to the microemulsion from Step 3, and after thorough stirring, dilute it to a nanoemulsion with a mass concentration of 0.3%.

[0035] The nanoemulsions prepared in the above embodiments were tested for their interface regulation capabilities and high-temperature thermal stability. Furthermore, their ability to enhance the recovery rate of high-temperature shale oil reservoirs through percolation displacement experiments was evaluated using core displacement experiments. The relevant test results are as follows:

[0036] 1. Nanoemulsion interface regulation capability

[0037] The interfacial tension between the nanoemulsion and kerosene was tested using a rotating drop interfacial tensiometer to optimize the emulsion concentration. This concentration of nanoemulsion was then aged at different temperatures for 12 hours to investigate the effect of temperature on the interfacial tension. The effect of the nanoemulsion on the rock wettability was tested using an optical contact angle meter. Core slices were polished and aged in crude oil for 48 hours to achieve oil wettability, and the contact angle between the core slices and water was measured. The aged core slices were then immersed in the nanoemulsion for 48 hours, and the changes in contact angle before and after the nanoemulsion treatment were compared. The relevant experimental results are as follows: Figure 1 , Figure 2 As shown.

[0038] Figure 1 ( a The interfacial tension between nanoemulsions of different concentrations and kerosene at room temperature is denoted as ( ). As the mass concentration of the nanoemulsion increases, the interfacial tension decreases. The surfactant increases the stability of the emulsion, and the film formation prevents oil droplet aggregation, thus reducing the interfacial tension. When the mass concentration exceeds 0.3%, the interfacial tension remains relatively stable. Therefore, the optimal mass concentration for preparing the nanoemulsion is 0.3%. After aging a 0.3% nanoemulsion at different temperatures for 12 hours, its interfacial tension with kerosene was tested. Figure 1 ( bThe interfacial tension of the nanoemulsion increases from 0.012 mN / m to 0.015 mN / m as the aging temperature increases. The increase in temperature leads to intensified Brownian motion and increased collision between oil droplets, resulting in aggregation of the droplets and thus an increase in the interfacial tension. However, the increase is not large and the interfacial tension remains at a low level.

[0039] Figure 2 The contact angle of the core slice before and after aging in the nanoemulsion with a mass concentration of 0.3% is measured. The core slice contact angle test shows that the contact angle of the core slice with water is 104°, indicating that the core slice is hydrophobic. After aging in the nanoemulsion for 12 hours, the contact angle decreases to 43°, indicating that after the nanoemulsion is injected into the formation, the oil-wet rock surface can be converted to a water-wet surface. The rock composition is mainly dolomite, which is hydrophilic. After aging treatment with crude oil, the surface is attached with a layer of crude oil molecules, becoming oil-wet. After soaking treatment with the nanoemulsion, the crude oil on the rock surface is removed, the rock surface is covered with the nanoemulsion, a new wetting film is formed, and the rock surface is hydrophilic, which is beneficial to the subsequent injection of water, so that the water phase pressure is greater than the oil phase pressure, and the water phase can enter the rock pore under the action of capillary force to displace the crude oil and prevent the reattachment of the crude oil.

[0040] 2. High-temperature thermal stability of the nanoemulsion

[0041] The nanoemulsion is injected into an aging tank and aged at different temperatures for a long time. After cooling, whether the nanoemulsion is turbid or layered is observed to evaluate the long-term stability of the nanoemulsion. The related experimental results are shown in FIGS. 2(a) to 2(c). Figure 3 The nanoemulsion with a mass concentration of 0.3% is semitransparent, as shown in FIG. 2(a). Figure 3 a At 100°C, 120°C, and 140°C, the nanoemulsion does not appear to be layered after being left standing for 12 hours and 5 days, and the stability is good, as shown in FIGS. 2(b) and 2(c). Figure 3 b c

[0042] 3. Oil displacement ability of the nanoemulsion

[0043] The core is fractured and dried for 24 hours after vacuumizing. The dry weight of the core is measured. Then, the core is soaked in crude oil and aged at 140°C for one month to restore the original state of the reservoir. The wet weight of the saturated core is measured, and the oil saturation of the core is calculated accordingly. Then, the core is injected with formation water for a primary water flooding. When the water cut reaches 98%, the nanoemulsion (with a mass concentration of 0.3%) is injected, and the inlet and outlet are closed. After “soaking” for 20 hours, a secondary water flooding is performed to obtain the oil displacement ability of the nanoemulsion in the shale core at different injection amounts.

[0044] Figure 4 ​​​​The oil displacement ability of the nano-emulsion in the shale core under different injection amounts. After the injection of 0.2 PV, 0.5 PV, 0.8 PV and 1 PV, the soaking time is 20 h, the temperature is 140 DEG C, and the confining pressure is 12 MPa. Under different injection amounts, the final oil recovery rate of the nano-emulsion is obviously improved compared with the conventional water flooding, and the increase range is 5.96%~9.23%; when the injection amount is 0.5 PV, the final oil recovery rate is improved by 3.05% compared with the injection of 0.2 PV; when the injection amount is more than 0.5 PV, the effect of improving the oil recovery rate is not obvious.

[0045] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a temperature-resistant nanoemulsion, characterized by, The method comprises the following steps: Step 1: preparing an oil-water mixture by using D-limonene as an oil phase and a sodium chloride aqueous solution as an aqueous phase; Step two: amido propyl betaine zwitterionic surfactant, α - olefin sulfonate anionic surfactant and organic alcohol co-surfactant mixture as emulsifier; Step 3: adding the emulsifier in step 2 into the oil-water mixture drop by drop, and continuously stirring until the mixture becomes a homogeneous transparent phase, namely a homogeneous microemulsion; Step 4: adding water into the microemulsion in step 3, and after sufficient stirring and dilution, a nanoemulsion is obtained; The mass ratio of the oil phase to the water phase in step one is 4:6-6:4, and the mass concentration of the sodium chloride aqueous solution is 6%-12%; the amido propyl betaine zwitterionic surfactant in step two includes one or more than two combinations of lauryl amido propyl betaine, cocamide propyl betaine, palmitoyl amido propyl betaine and oleamide propyl betaine; the α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C 12 ~C 18 α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C 12 ~C 18 -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C 12 ~C 18 -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C 12 ~C 18 -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C α -olefin sulfonate anionic surfactant includes one or more than two combinations of sodium, magnesium and potassium olefin sulfonate with a carbon chain length of C 12 ~C 2. Use of the nanoemulsion prepared by the method according to claim 1 for imbibition oil displacement in shale oil reservoirs, characterized in that, The mass concentration of the nanoemulsion is 0.2%-0.5%, the formation temperature of the shale oil reservoir is higher than 120 DEG C, and the core permeability is less than 1.0 mD.

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