CN115386358B - Natural surfactant compound system and preparation method thereof - Google Patents

Abstract

The invention discloses a natural surfactant compound system and a preparation method thereof, which comprises the following components: choline chloride, citric acid and camellia saponin. The compound system provided by the present invention can effectively improve the inhibition of clay mineral hydration expansion, and reduce the occurrence of various complex situations in oil reservoirs to a large extent; the compound system provided by the present invention has low interfacial tension, making The obtained composite system can effectively improve the oil displacement efficiency, and has a remarkable pressure-reducing effect; the source of raw materials is extensive, the preparation process is simple, and there is no pollution to the formation.

Description

A kind of natural surfactant complex system and preparation method thereof

technical field

The invention belongs to the technical field of oil displacement agent preparation, and in particular relates to a natural surfactant compound system and a preparation method thereof.

Background technique

Low-permeability reservoir resources occupy an important strategic position in my country. According to the results of the third survey of oil and gas resources in my country, the resources of low-permeability reservoirs account for 49% of the total resources in the country. Low-permeability sandstone reservoirs have the characteristics of poor fluidity and high water injection resistance due to their extremely poor oil layer physical properties and high interfacial resistance effect in the capillary. The natural energy in the reservoir is insufficient. Poor physical properties of the reservoir, thin pore throat, high interface resistance, etc. lead to increased injection resistance, and even no water can be injected into the reservoir, while high-pressure water injection will make the surface equipment and downhole casing under high pressure, damage the equipment and downhole casing, and cause The formation will be broken due to high pressure, reducing the injection efficiency. Therefore, long-term high-pressure water injection is not feasible. Reducing interfacial resistance and injection pressure, and exploring ways to reduce pressure and increase injection in low-permeability reservoirs are the key to improving the development effect of water injection. The principle of reducing pressure and increasing injection is mostly based on reducing interfacial tension. Less consideration is given to the resistance effect produced by the solid-liquid interface in the fine pore throat, which has a more significant impact on seepage.

Surfactant flooding belongs to tertiary oil recovery, which refers to the injection of surfactants into the formation to reduce the interfacial tension between oil and water, thereby achieving the effect of improving the recovery efficiency of the reservoir. The chemical flooding technology with extremely high development potential has been widely used at home and abroad. The most widely used is anionic surfactant, and the least used is cationic surfactant. At present, most surfactants in tertiary oil recovery use multiple Compound system, such as patent CN109207136A discloses a compound system of anionic and cationic surfactants applied in high salinity oil reservoirs, so that the compound system can achieve the effect of ultra-low interfacial tension (10 ^-3 mN/m) , Another example is patent CN103773346A which discloses a compound system of cationic and anionic non-ionic surfactants for high-efficiency oil displacement. The interfacial tension of this compound system can reach ultra-low interfacial tension, and the ultimate recovery rate is increased by 7.5%. However, there are still many problems with the current surfactants, such as poor surface activity and unsatisfactory effect of enhancing oil recovery. Most anionic surfactants are used together with inorganic alkalis, which will cause corrosion to formations and pipeline equipment, and various Surfactants for oil displacement also have problems such as high cost.

Deep eutectic solvents (DES) are a special class of solvents that are mixtures of hydrogen bond donors and hydrogen bond acceptors. The interaction of these two substances causes the properties of the liquid to be significantly different from those of the components (at a temperature of 23±2°C). The main feature of DES is that it has a lower melting point than any of its components. Therefore, DES is usually a viscous liquid at room temperature, while its components are all crystalline solids. Compared with other ionic liquids, DES is biodegradable and non-toxic, easy to prepare, cheap, and has a wide source of raw materials. Unlike conventional ionic liquids, DES is easily prepared in pure form. DES are also known as green solvents because of their negligible vapor pressure, non-flammability, non-explosive properties, low toxicity, and good electrochemical and thermal stability. DES is a molten salt, which mainly forms a large number of hydrogen bond networks or metal halide interactions through the anions of the salt, rather than relying on the electrostatic force between anions and cations like ionic liquids. DES has a large number of hydrogen bond networks. It has great potential in inhibiting the hydration expansion of clay.

China has the world's largest planting area of camellia oleifera, with a total area of about 55 million mu, mainly distributed in Hunan, Jiangxi and other places in China. Camellia oleifera saponin, also known as camellia oleifera saponin, is a natural glycoside compound contained in camellia oleifera. A natural non-ionic surfactant extracted from waste after oil extraction, mainly composed of glycosides, saponins, and organic acids, with a hydrophilic-lipophilic balance (HLB) of 16, and has good foaming, foam stabilizing, and emulsifying properties , wetting and solubilizing effects, its raw materials have a wide range of sources, the cost is extremely low, it belongs to waste utilization, and camellia saponin is a natural surfactant, non-toxic and harmless, and can be applied to the field of crude oil exploitation, but the single camellia saponin The limited surface activity is not enough to achieve the effect of high oil recovery efficiency.

Contents of the invention

The purpose of this section is to outline some aspects of embodiments of the invention and briefly describe some preferred embodiments. Some simplifications or omissions may be made in this section, as well as in the abstract and titles of this application, to avoid obscuring the purpose of this section, abstract and titles, and such simplifications or omissions should not be used to limit the scope of the invention.

In view of the problems mentioned above and/or in the prior art, the present invention is proposed.

Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a kind of natural surfactant complex system.

In order to solve the above technical problems, the present invention provides the following technical proposal: a natural surfactant compound system, which includes the following components: choline chloride, citric acid, and camellia saponin.

Another object of the present invention is a method for preparing a compound system of natural surfactants.

In order to solve the above-mentioned technical problems, the present invention provides the following technical solutions: a preparation method of a compound system of natural surfactant, which comprises the steps of:

Preparation of deep eutectic solvent: mixing choline chloride and citric acid to obtain a deep eutectic solvent;

Preparation of the composite system: mixing the deep eutectic solvent and camellia oleifera saponin, adding water to prepare the composite system, which is the natural surfactant composite system.

As a preferred version of the preparation method of the compound system of the natural surfactant of the present invention, wherein: in the preparation of the natural deep eutectic solvent, according to the molar ratio, choline chloride:citric acid=0.5～2:1 .

As a preferred version of the preparation method of the compound system of natural surfactant of the present invention, wherein: in the preparation of natural deep eutectic solvent, according to the molar ratio, choline chloride:citric acid=1:1.

As a preferred scheme of the preparation method of the natural surfactant compound system of the present invention, wherein: in preparing the compound system, according to the molar ratio, deep eutectic solvent: camellia saponin = 0.5-2:1.

As a preferred scheme of the preparation method of the natural surfactant compound system of the present invention, wherein: in preparing the compound system, according to the molar ratio, the deep eutectic solvent: camellia saponin=1:1.

As a preferred solution of the preparation method of the natural surfactant complex system of the present invention, wherein: in the preparation of the deep eutectic solvent, choline chloride and citric acid are mixed under a heating environment.

As a preferred version of the preparation method of the compound system of natural surfactants according to the present invention, wherein: in the preparation of the deep eutectic solvent, choline chloride and citric acid are stirred, and heated at 60-100°C for 1- 3h.

As a preferred solution of the preparation method of the natural surfactant compound system of the present invention, wherein: in the preparation of the deep eutectic solvent, the choline chloride and citric acid are stirred and heated at 80° C. for 2 hours.

Beneficial effects of the present invention:

1. The compound system provided by the present invention can effectively improve the inhibition of hydration expansion of clay minerals, and reduce the occurrence of various complex situations in oil reservoirs to a large extent;

2. The compound system provided by the present invention has low interfacial tension, which is lowered again on the basis of natural surfactants, is very stable over time, and can still maintain low interfacial tension in a high salinity environment;

3. The compound system provided by the present invention can effectively improve the oil displacement efficiency, and the pressure-reducing effect is remarkable;

4. The compounding system provided by the present invention adopts natural surfactant compounding, belongs to waste material utilization, has wide sources of raw materials, simple preparation process, and no pollution to the formation.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort. in:

Fig. 1 is the experimental result of inhibiting the hydration expansion of montmorillonite by different systems in Fig. 1 during the implementation of the present invention.

Fig. 2 is the infrared spectrogram of DES, camellia saponin and compound system in the implementation of the present invention;

In the figure, picture a is the infrared spectrum spectrum of DES, camellia saponin and compound system, picture b is the infrared spectrum spectrum of DES, picture c is the infrared spectrum spectrum of camellia saponin, and picture d is the compound system of DES+ camellia saponin Infrared Spectrum;

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and comprehensible, the specific implementation manners of the present invention will be described in detail below in conjunction with the embodiments of the specification.

In the following description, a lot of specific details are set forth in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described here, and those skilled in the art can do it without departing from the meaning of the present invention. By analogy, the present invention is therefore not limited to the specific examples disclosed below.

Second, "one embodiment" or "an embodiment" referred to herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. "In one embodiment" appearing in different places in this specification does not all refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

Example 1

Take by weighing 0.381g choline chloride and 0.519g citric acid respectively, the molar ratio is 1:1, stir and heat 2h with 200r/min in constant temperature water bath, experiment temperature is 80 ℃, mix well, obtain deep eutectic solvent ( DES);

Compound the prepared DES and camellia saponin at a molar ratio of 1:1, add 100mL of water, and stir evenly and fully to obtain a compound system;

Weigh 10 g of sodium-based montmorillonite passed through a 200-mesh sieve, and press the sodium-based montmorillonite in a press (YLJ600 press) at 10 MPa for 10 minutes to prepare an artificial rock core.

Soak the artificial core in a petri dish of distilled water, 3wt% KCl and 3vol% compound system solution for 24 hours, so that the solution is completely submerged on the surface of the artificial core, and take pictures to record the hydration of the artificial core in three different solutions for different soaking times Inflated situation.

Record the captured pictures in Figure 1.

It can be seen from Figure 1 that the hydration swelling effect of sodium-based montmorillonite in different systems (distilled water, 3% KCl, 1% compound system) was compared. At different time points, the 1% compound system soaked The resulting core has a more obvious effect of inhibiting expansion, K ⁺ can be embedded in the hexagonal pores of the Na-based montmorillonite lattice, and it is difficult to exchange, thus effectively preventing water molecules from entering the pore structure of the montmorillonite , inhibiting the hydration swelling of montmorillonite. The surfactant molecules in the complex system will preferentially enter the hexagonal pores of the Na-based montmorillonite lattice and be adsorbed on the surface of the montmorillonite. DES also forms a large number of hydrogen bond networks through the anions of the salt. In addition, the complex system The hydrophobicity of montmorillonite is enhanced, and the hydration swelling of montmorillonite is more effectively inhibited.

Embodiment 2 (oil-water interfacial tension test)

Weigh 0.4g choline chloride and 0.6g citric acid respectively, the molar ratio is 1:1, stir and heat in a constant temperature water bath with 3000rpm for 2h, the experimental temperature is 80°C, mix well to obtain a deep eutectic solvent (DES ), add 100mL distilled water to make DES solution;

Weigh 1g of camellia saponin, add 100mL of water, stir evenly and fully to prepare surfactant solution;

Use the spin-drop type interfacial tensiometer (Shanghai Zhongchen Digital Technology Equipment Co., Ltd. JJ2000B2) to measure the oil-water interfacial tension of DES and the surfactant solution whose mass concentration is 1wt%, the rotating speed is 6000r/min, and the experimental temperature is 40°C. The oil used in the experiment was crude oil from a certain block of Shengli Oilfield;

Take by weighing 0.127g choline chloride and 0.173g citric acid respectively, the molar ratio is 1:1, according to choline chloride and citric acid and according to the DES that the molar ratio 1:1 makes, and camellia saponin respectively by molar ratio For 2:8, 4:6, 5:5, 6:4, 8:2, carry out compounding, add 100mL water to obtain the compound system, use the spin-drop type interfacial tensiometer to measure the oil-water interfacial tension of the compound system.

The oil-water interfacial tension of DES and camellia saponin prepared in different molar ratios is shown in Table 1.

It can be obtained from Table 1 that the experiment shows that DES and camellia saponin with a mass concentration of 1wt% alone have high oil-water interfacial tension, while the compound system prepared with a molar ratio of 5:5 between DES and camellia saponin has a great degree of The interfacial tension of oil and water is reduced, reaching the lowest low interfacial tension of 1.12×10 ^-2 mN/m, and it does not change much with time.

Table 1 Test results of oil-water interfacial tension of different systems

Embodiment 3 (salt tolerance test)

Weigh 0.127g of choline chloride and 0.173g of citric acid respectively, the molar ratio is 1:1, stir and heat in a constant temperature water bath at 3000rpm for 2h, the experimental temperature is 80°C, and mix well to obtain a deep eutectic solvent (DES) ;

Compound the prepared DES and camellia saponin at a molar ratio of 1:1, add 100mL of water, and stir evenly and fully to obtain a compound system;

Add 500mg, 1000mg, 1500mg, 2500mg, and 4000mg of CaCl ₂ to the compound system to test the salt tolerance of the compound system, so that the Ca ²⁺ concentration in each compound system is 50mg/L, 100mg/L, 150mg /L, 250mg/L, 400mg/L,;

The interfacial tension of oil and water after adding different amounts of CaCl ₂ was measured using a spin-drop interfacial tensiometer. The rotational speed was 6000r/min, and the experimental temperature was 40°C. The oil used in the experiment was crude oil from a block in Shengli Oilfield.

It can be seen from Table 2 that the minimum interfacial tension of the compound system is still 2.70×10 ^-2 mN/m under high concentration of Ca ²⁺ , and the interfacial tension of the compound system does not change much with the increase of Ca ²⁺ concentration, and Very stable over time and exhibits excellent salt tolerance.

Salt tolerance test result of compound system of table 2

Embodiment 4 (wettability test)

Weigh 0.127g of choline chloride and 0.173g of citric acid respectively, the molar ratio is 1:1, stir and heat in a constant temperature water bath at 3000rpm for 2h, the experimental temperature is 80°C, and mix well to obtain a deep eutectic solvent (DES) ;

Compound the prepared DES and camellia saponin at a molar ratio of 1:1, add 100mL of water, and stir evenly and fully to obtain a compound system;

The top of the core taken in the experiment was polished to a smooth surface by a core planer. After the core was soaked in distilled water for 48 hours, the contact angle of the top of the core was measured and recorded by using a metal syringe to measure the contact angle of the core with distilled water and oil through the fixed drop technique;

The core was placed in the prepared compound system and soaked for 48 hours, and the contact angle between water and oil was measured at this time, and the change of the wettability of the core by the compound system was judged by the change of wetting angle.

Experimental results: The experimental results are shown in Table 3. The experiment shows that after the core is treated with the compound system, the contact angle between the water phase and the oil phase becomes larger, the water phase contact angle changes from 7.7° to 64.4°, the hydrophobicity is enhanced, and the oil phase contacts The antennae changed from 27.7° to 64.4°, and the lipophilicity weakened, indicating that the surfactant in the compound system was adsorbed on the surface of the core, which effectively changed the interfacial properties of the core surface and reduced the adsorption of oil droplets on the rock surface, and the lipophilicity of the core was significant. decrease, wettability reversal occurs on the core surface.

Table 3 wettability test results of compound system

water phase contact angle oil phase contact angle before testing 47.8° 27.7° after test 53.4° 64.4°

Embodiment 5 (infrared spectrum test)

Weigh 0.127g choline chloride and 0.173g citric acid respectively, the molar ratio is 1:1, stir and heat in a constant temperature water bath for 2h, the experimental temperature is 80°C, mix well to obtain a deep eutectic solvent (DES), and then Add 0.717g camellia saponin, dissolve it in DES, stir evenly and fully, and the molar ratio of DES to camellia saponin is 1:1 to obtain a compound system.

Use the deep eutectic solvent, camellia oleifera saponin and the compound system prepared according to the above ratio to prepare sample compression tablets, place the prepared potassium bromide blank on the sample holder in the sample chamber of the infrared spectrometer, and determine the collection reference After the background spectrum is collected, take out the potassium bromide blank sheet, put the sample sheet to be tested into the spectrometer, close the cover, and obtain the infrared spectrum of the sample. The infrared spectrum of the system is marked in Figure 2.

It can be seen from Figure 2 that compared with Camellia oleifera saponin alone, the compound system has a wide and long -OH stretching vibration peak in the wavelength range of 2500cm ^-1 -3500cm ^-1 , indicating that a large number of hydrogen bonds in DES have been added to the compound system, making The ability of the system to reduce interfacial tension is greatly improved, and the addition of DES also makes the compound system have a stretching vibration peak of C≡C at a wavelength of 2010cm ^-1 , and a stretching vibration peak of C=O at a wavelength of 1732cm ^-1 , and a wavelength of 1478cm ^-1 , 1409cm ^-1 corresponds to the CH in-plane bending vibration peak, the wavelength 1196cm ^-1 corresponds to the CC stretching vibration peak, the wavelengths 1082cm ^-1 , 955cm ^-1 correspond to the CH in-plane bending vibration peak, and the wavelength 1006cm ^-1 , 866cm ^-1 and 783cm ^-1 correspond to the CH out-of-plane bending vibration peaks. Compared with camellia saponin alone, the hydrophobicity of the compound system is enhanced, and the inhibition of the water-sensitive expansion of sodium montmorillonite is also enhanced.

Embodiment 6 (displacement experiment)

Weigh 0.127g of choline chloride and 0.173g of citric acid respectively, the molar ratio is 1:1, stir and heat in a constant temperature water bath at 3000rpm for 2h, the experimental temperature is 80°C, and mix well to obtain a deep eutectic solvent (DES) , then add 0.717g camellia saponin, dissolve it in DES, stir evenly and fully, and the molar ratio of DES to camellia saponin is 1:1, and a compound system is obtained.

The core sample is saturated with distilled water at room temperature, the pressure at the injection port and the outlet port is monitored in real time, and the core is weighed before and after water saturation, and the permeability and porosity of the core are calculated, and then the core is saturated with oil. The basic parameters of the experimental core are shown in Table 4;

Put the configured compound system in a high-pressure container, fill the core holder with oil saturated and connect it to the core displacement device, first inject water until the outlet end no longer produces oil and the pressure at the inlet end is stable, then inject the complex Prepare the system solution until the pressure is stable, then reinject water until the pressure is stable, record the inlet pressure and oil/water output of each displacement stage, and analyze the effect of depressurization and enhanced injection and the improvement of recovery factor.

Permeability and porosity experiments were performed on cores. The experimental settings were that the confining pressure was 20MPa, the back pressure was 3MPa, the experimental temperature was 25°C, and the injection rate was 0.05mL/min.

Experimental results: The experimental results are shown in Table 5. The experiment shows that after the injection of the compound system, the injection pressure of the second water injection is stabilized, compared with the injection pressure after the first water injection. The effect of reducing the injection pressure is very significant. 17.42%, in the core sample 1-2, the depressurization rate reached 19.66%; in the core sample 1-1, the recovery rate increased by 5.7% after injecting the compound system, and the recovery rate was increased by 0.5% after the second water injection, and finally The recovery rate was 42.6%. In the core sample 1-2, the recovery rate increased by 6.5% after injecting the compound system, and the recovery rate was increased by 0.7% after the second water injection, and the final recovery rate was 45.4%. The oil displacement efficiency of the sample.

Table 4 Basic parameters of experimental cores

Table 5 Test results of stable injection pressure and recovery factor at each stage of displacement

It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation, although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (4)

1. a preparation method of natural surfactant compound system, is characterized in that: described natural surfactant compound system comprises following component: choline chloride, citric acid, camellia saponin; The method also includes the following steps: preparing a deep eutectic solvent: mixing choline chloride and citric acid to obtain a deep eutectic solvent; Preparation of composite system: mixing deep eutectic solvent and camellia oleifera saponin, adding water to prepare a composite system, which is a natural surfactant composite system; In the preparation of the natural deep eutectic solvent, according to the molar ratio, choline chloride:citric acid=0.5～2:1; In the preparation composite system, according to the molar ratio, deep eutectic solvent: camellia saponin=0.5～2:1; In the preparation of the deep eutectic solvent, the choline chloride and citric acid are stirred and heated at 60-100° C. for 1-3 hours. 2. the preparation method of the composite system of natural surfactant according to claim 1, is characterized in that: in described preparation natural deep eutectic solvent, according to mol ratio, choline chloride: citric acid=1:1 . 3. the preparation method of the compound system of natural surfactant according to claim 1, is characterized in that: in described preparation compound system, according to molar ratio, deep eutectic solvent: camellia saponin=1:1. 4. The preparation method of the compound system of natural surfactant according to claim 1, characterized in that: in the preparation of the deep eutectic solvent, choline chloride and citric acid are stirred and heated at 80° C. for 2 hours.