Preparation method of flexible liposome injection enhancer for low-permeability oil reservoir

Abstract

The present application relates to a kind of low permeability oil reservoir injection enhancer by phosphatidylserine, phosphatidylinositol, lecithin, sodium cholate, diethanolamine, 1-dodecylazacycloheptane-2-ketone and tetramethylammonium chloride as raw material preparation method.The present application first phosphatidylserine, phosphatidylinositol, lecithin, cholic acid, 1-dodecylazacycloheptane-2-ketone and diethanolamine are dissolved in anhydrous ethanol according to certain proportion, and the mixed solution of five kinds of substances is prepared;Tetramethylammonium chloride and ammonium chloride are dissolved in water according to certain proportion, and the mixed solution of two kinds of substances is prepared;Then slowly pour the first solution into the second solution under ultrasonic dispersion conditions, and prepare a kind of flexible liposome colloid solution.The injection water configured by the colloid solution has high efficient permeability, can greatly reduce the injection pressure of low permeability core, and the preparation process is reliable, provides a kind of low permeability oil reservoir flexible liposome injection enhancer preparation method.

Description

Technical Field

[0001] This invention belongs to the field of oilfield production aids, and specifically relates to a method for preparing a flexible liposome injection agent for low-permeability reservoirs using phosphatidylserine, phosphatidylinositol, lecithin, sodium cholate, diethanolamine, 1-n-dodecylazine-2-one and tetramethylammonium chloride as raw materials. Background Technology

[0002] Low-permeability oil reservoirs are characterized by dense rocks, narrow pore throats, and very poor permeability, resulting in very low primary recovery rates for oil wells. The average permeability of oil-bearing layers in typical low-permeability oilfields is (10.1–50) × 10⁻⁶. -3 um 2 Although oil wells can meet industrial oil flow standards, their production is too low, requiring various production enhancement measures to increase production capacity and achieve better development results and economic benefits. Statistics from 15 low-permeability oilfields nationwide show that the final recovery rate relying on natural energy extraction is only 17%, while water-driven development can achieve a final recovery rate of 26.9%. This demonstrates that maintaining reservoir pressure through water injection is the primary extraction method for low-permeability oilfields. Injection-production balance is the foundation for stable production in water-injected oilfields. However, as the injection time increases, the surface of the oil-bearing rock near the wellbore hydrates and expands, clogging the throat and causing the injection pressure to gradually rise, preventing water from entering the reservoir. Currently, most oilfields increase the injection pressure to increase the injection volume, leading to increasingly higher pressures. However, the injection pressure cannot exceed the capacity of the equipment and reservoir. Therefore, simply increasing the injection pressure to increase the injection volume cannot fundamentally solve the problem and poses a safety hazard. The currently common method for enhancing injection is acidizing the injection wells to remove contamination in the near-wellbore area and the expanded layer on the rock surface, achieving the effect of reducing pressure and enhancing injection. However, this method has a short effective period, requires frequent operations, and has poor results. Furthermore, while rigid nanoparticle injection enhancement technology and molecular membrane injection enhancement technology have achieved some success in some low-permeability and ultra-low-permeability oilfields both domestically and internationally, the injection pressure remains too high to achieve efficient water injection. Therefore, how to economically and effectively develop low-permeability oil and gas reservoirs is one of the main challenges facing oilfield production in my country.

[0003] This invention relates to a flexible liposome-based water injection enhancement agent for ultra-low permeability reservoirs, prepared from phosphatidylserine, phosphatidylinositol, lecithin, cholic acid, diethanolamine, 1-n-dodecylazine-2-one, and tetramethylammonium chloride. The flexible liposomes possess high deformability, high permeability, and high hydrophilicity, allowing them to efficiently penetrate rock pores several times smaller than themselves along the hydration gradient. Simultaneously, they self-assemble a hydrophobic monolayer on the inner surface of the rock pores, changing the pore surface from hydrophilic to hydrophobic, reducing the viscosity of water passing through the pores, thereby lowering the injection pressure and increasing the injection volume. This flexible liposome-based enhancement agent exhibits good stability, strong penetration ability, and can significantly reduce the injection pressure of low-permeability cores, thereby improving oil recovery. Summary of the Invention

[0004] This invention first prepares an ethanolic solution by dissolving phosphatidylserine, phosphatidylinositol, lecithin, cholic acid, 1-dodecylazine-2-one, and diethanolamine in anhydrous ethanol in a specific ratio. Then, tetramethylammonium chloride and ammonium chloride are dissolved in water in a specific ratio to prepare an aqueous solution containing the two substances. Finally, the first solution is slowly poured into the second solution under ultrasonic dispersion conditions to prepare a colloidal solution of flexible liposomes. The injection water prepared from this colloidal solution exhibits high penetration efficiency, significantly reducing the injection pressure in ultra-low permeability cores. The preparation process is reliable, providing a method for preparing a flexible liposome injection enhancer for low-permeability reservoirs. Detailed Implementation

[0005] Example 1

[0006] (1) Weigh 0.5 g of phosphatidylserine, 0.3 g of phosphatidylinositol, 2.5 g of lecithin, 0.5 g of cholic acid, 1.0 g of 1-n-dodecylazine-2-one and 1.5 g of diethanolamine, and add them sequentially to a mixed solvent of 40 mL of ethanol and 10 mL of N,N-dimethylformamide. Heat to 45 °C and stir until the solid is completely dissolved. Cool to room temperature and let stand for 24 hours. Filter and collect the filtrate to obtain a light yellow uniform liquid for later use.

[0007] (2) Weigh 15.0 g of tetramethylammonium chloride and 25.0 g of ammonium chloride and add them to 500 ml of distilled water. Stir to dissolve, filter, collect the filtrate, and obtain a yellow uniform liquid.

[0008] (3) Add the light yellow uniform liquid obtained in (1) of Example 1 to the yellow uniform liquid obtained in (2) of Example 1, and sonicate for 1 hour to obtain a milky white sol. Seal and set aside for later use.

[0009] Example 2

[0010] Take 0.5g of sample (3) from Example 1 and place it in a 250ml beaker. Dilute it with 100ml of tap water, mix it evenly by sonication, and place the beaker in a 40℃ water bath for 10 minutes. Take the diluted sol into a colorimetric tube. Measure the turbidity of the solution using an STZ-A26C benchtop turbidimeter. Place the colorimetric tube into the turbidimeter, turn it on, and after it stabilizes, read the turbidity of the three sols at 30, 40, 50, 60, 70, 80, and 90 minutes after sample dilution. Following the same method, adjust the water bath temperature to 60℃ and 90℃ respectively, and measure the turbidity of the solution (3) from Example 1 diluted with tap water at different times under the two temperatures. The results are shown in Table 1.

[0011] Table 1. Changes in solution turbidity at different temperatures

[0012]

[0013] The results showed that the solution (3) in Example 1 had good stability at all three temperatures.

[0014] Example 3

[0015] A clean glass slide was placed in a 0.05% aqueous solution of (3) in Example 1 at 25°C. After standing for 72 hours, the slide was removed, allowed to dry naturally, and the contact angles of tap water, kerosene, -10 diesel oil, and toluene on the slide surface were measured. The results are shown in Table 2.

[0016] Table 2 Contact angles of various liquids on the membrane surface

[0017] Types of liquids tap water kerosene -10 diesel Toluene Contact angle, degrees 102 25 21 34

[0018] The results showed that the film formed by adsorbing (3) from Example 1 onto the glass slide had good hydrophobicity, and the wettability of kerosene, diesel oil (-10) and toluene on the film was much greater than that of water.

[0019] Example 4

[0020] Weigh out the sample (3) from Example 1 and prepare 0.01%, 0.03%, and 0.05% sample solutions respectively with tap water for later use. Select a test column, open the opening valve, and close all valves of other test columns; add the required amount of tap water to the storage tank, turn on the gear pump to supply liquid, set the supply speed, fill the entire test pipeline with test liquid, and adjust the discharge rate to the set flow rate. Read the pressure difference. When the pressure difference changes by less than 1% within 1 minute, calculate the average pressure difference as the frictional pressure difference of the clean water (ΔP1); measure the frictional pressure difference (ΔP2) of the sample solution (3) from Example 1 with different concentrations flowing through the pipeline according to the same method. And calculate the drag reduction rate DR. The results are shown in Table 3.

[0021]

[0022] In the formula:

[0023] DR – drag reduction rate of polymer solution on water (%);

[0024] ΔP1—Pressure difference (Pa) when clean water flows through the pipeline;

[0025] ΔP2 — Pressure difference (Pa) as the polymer solution flows through the pipeline.

[0026] Table 3. Pressure difference and drag reduction rate of solutions with different concentrations at different flow rates (25℃)

[0027]

[0028]

[0029] The results showed that, under the same flow rate, the pressure drop of sample solutions of different concentrations flowing through the pipe was less than that of tap water, and the pressure difference increased with the increase of flow rate. The pressure difference of sample solutions of different concentrations flowing through the pipe gradually increased with the increase of flow rate, and the increase was smaller with the higher the concentration. Under high flow rate, the drag reduction rate of sample solutions of various concentrations flowing through the pipe was greater than 50%, indicating that sample (3) in Example 1 has good drag reduction performance.

[0030] Example 5

[0031] An artificial core with a major diameter of 2.5 cm × 2.5 cm was placed in a core holder for later use. Simulated formation water with a salinity of 20000 mg / L was pumped forward at a pump rate of 3 ml / min. After the pressure difference across the core tube stabilized, the permeability K0 and pressure difference ΔP0 of the core were measured. Then, 0.1 PV of 0.01% of the solution (3) in Example 1 was injected in reverse, replacing 1 PV of simulated formation water with a salinity of 20000 mg / L. After standing for 3 hours, simulated formation water with a salinity of 20000 mg / L was pumped forward at a pump rate of 3 ml / min. After the pressure difference across the core tube stabilized, the permeability K and pressure difference ΔP of the core after treatment were measured. The permeability of the core before and after treatment was measured at three temperatures: 30℃, 60℃, and 90℃, respectively, according to the above method. The results are shown in Table 4.

[0032] Table 4. Permeability Improvement Rate and Injection Pressure Difference Reduction Rate after Core Processing

[0033]

[0034] The results showed that after the core was treated with sample (3) in Example 1, the permeability was significantly increased and the injection pressure was significantly reduced. Moreover, the effect was more obvious as the permeability of the core decreased.

Claims

1. A method for preparing a flexible liposome injection enhancer for low-permeability reservoirs, characterized in that, Includes the following steps: (1) Weigh 0.5 g of phosphatidylserine, 0.3 g of phosphatidylinositol, 2.5 g of lecithin, 0.5 g of cholic acid, 1.0 g of 1-n-dodecylazine-2-one and 1.5 g of diethanolamine, and add them sequentially to a mixed solvent of 40 mL of ethanol and 10 mL of N,N-dimethylformamide. Heat to 45 °C and stir until the solid is completely dissolved. Cool to room temperature and let stand for 24 hours. Filter and collect the filtrate to obtain a light yellow uniform liquid for later use. (2) Weigh 15.0 g of tetramethylammonium chloride and 25.0 g of ammonium chloride and add them to 500 mL of distilled water. Stir to dissolve, filter, collect the filtrate, and obtain a yellow uniform liquid. (3) Add the light yellow uniform liquid obtained in (1) to the yellow uniform liquid obtained in (2) above, and sonicate for 1 hour to obtain a milky white sol. Seal and set aside for later use.

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