CN115011319B - A three-phase foam system for temperature-resistant and salt-resistant oil displacement, its preparation method and application - Google Patents

Abstract

The invention provides a three-phase foam system for temperature-resistant and salt-resistant flooding, and a preparation method and application thereof. The three-phase foam system for oil displacement of the invention has the foam volume of 350mL, the half life period of 34min, and the foam volume of 350mL produced by a Blender-Waring method of 100mL foaming liquid under the conditions of 80 ℃, 100000mg/L NaCl and 500mg/L calcium and magnesium ion concentration, and is used for water displacement and CO ₂ After gas flooding, CO is injected into 0.5PV foam ₂ The gas flooding, the final crude oil recovery ratio is 70.78%, and is 39.15% higher than that of water flooding. The invention can still keep stable foam for a long time under the high temperature condition, has good tolerance to calcium and magnesium ions, effectively reduces gas channeling, starts water flooding and residual oil after gas flooding, obviously improves recovery ratio, and is suitable for secondary development of high-temperature high-salt conventional sandstone oil reservoirs.

Description

A three-phase foam system for temperature-resistant and salt-resistant oil displacement, its preparation method and application

technical field

The invention relates to the technical field of oil field exploration, in particular to a temperature-resistant and salt-resistant three-phase foam system for oil flooding, a preparation method and application thereof.

Background technique

As more and more oilfields in my country enter the middle and late stage of development, the recovery rate of water flooding development gradually decreases, and the water content of produced fluid increases gradually. Foam injection is an effective anti-channeling method. The anti-channeling mechanism is mainly through the selective plugging of the high permeability zone by the foam to realize the diversion of the liquid flow. At the same time, the foam has a high apparent viscosity and can effectively control the gas-oil mobility. ratio, thereby maximizing the gas sweep volume. But the foam itself faces the problem of poor stability under reservoir conditions, so most of the current research focuses on improving the stability of foam under harsh conditions.

In response to this problem, researchers at home and abroad have conducted a lot of research, and various foam systems such as nanoparticle-stabilized foam, organic amine-stabilized foam, polymer-stabilized foam, and carboxymethylcellulose-stabilized foam have been proven to be used to improve oil recovery. rate work. However, due to limitations such as price, intolerance to high temperature, and intolerance to salt, it is difficult for the existing system to play a role in the oil field.

In view of this, the present invention provides a temperature-resistant and salt-resistant three-phase foam system for oil flooding and a preparation method thereof. The raw materials are cheap and easy to obtain, and have good effects under complex reservoir conditions.

Contents of the invention

The object of the present invention is to provide a temperature-resistant and salt-resistant three-phase foam system for oil flooding, its preparation method and application, aiming at the above-mentioned shortcomings of the prior art.

To achieve the above object, the present invention adopts the following technical solutions:

The first object of the present invention is to provide a three-phase foam system for temperature-resistant and salt-resistant oil displacement, which is made of anionic surfactant, zwitterionic surfactant, solid phase particles, dispersant, gas and water, in parts by weight The mass fraction of the anionic surfactant is 0.3-0.7 parts, 0.3-0.5 parts of zwitterionic surfactant, 3-7 parts of solid phase particles, 2-5 parts of dispersant, 100 parts of water, the gas The volume ratio to the three-phase foam system for oil displacement is 1:1-4:1.

Further, the anionic surfactant is one or both of sodium α-olefin sulfonate (AOS) and sodium dodecylbenzenesulfonate (SDBS).

Further, the zwitterionic surfactant is cocamidopropyl hydroxysultaine (CHSB).

Further, the solid phase particles are fly ash.

Further, the dispersant is sodium earth.

Further, the gas is carbon dioxide.

The second object of the present invention is to provide a method for preparing the above-mentioned three-phase foam system for temperature-resistant and salt-resistant oil flooding, comprising the following steps:

Step S1, pouring a certain amount of deionized water into a beaker, adding inorganic salts into the beaker to prepare simulated formation water;

Step S2, placing the beaker on a magnetic stirrer, setting the first preset speed, adding a certain amount of anionic surfactant to the beaker in step S1, and stirring until completely dissolved;

Step S3, adding a certain amount of zwitterionic surfactant to step S2, stirring until completely dissolved;

Step S4, adding a certain amount of dispersant to step S3, stirring to make it fully suspended;

Step S5, adding a certain amount of solid phase particles to the step S4, stirring to make it fully suspended, to obtain a foaming liquid;

Step S6, sealing the stirred foaming solution with a plastic wrap, and placing it in an incubator for aging;

Step S7, transfer the aged foaming liquid to a high-speed agitator, set the second preset speed, pass carbon dioxide into it for 10 minutes, set the speed at 8000r/min, and stir for 2 minutes to obtain the three-phase oil displacement foam system.

Further, the first preset rotation speed is 350r/min-400r/min, and the second preset rotation speed is 6000r/min-8000r/min.

Further, the aging time in step S6 is 48h-60h.

The third object of the present invention is to provide the above-mentioned three-phase foam system solution for oil displacement to be used for preparing oilfield foam control and displacement agent.

Compared with the prior art, the beneficial effects brought by the technical solution provided by the present invention are:

(1) Under the conditions of 80°C, 100000mg/L NaCl, and 500mg/L of calcium and magnesium ion concentration in the three-phase foam system for oil displacement of the present invention, the volume of foam produced by 100ml of foaming liquid by the Blender-Waring method is 350mL, and the half-life is At 34 minutes, after water flooding and CO ₂ gas flooding, 0.5PV foam was injected and CO ₂ gas flooding was carried out. The final oil recovery rate was 70.78%, which was 39.15% higher than that of water flooding. Moreover, the present invention can still maintain long-term foam stability under high temperature conditions, and at the same time, has good tolerance to calcium and magnesium ions, effectively reduces gas channeling, and the residual oil after water flooding and gas flooding is started, and the sodium ion concentration is lower than 150,000mg/ L. When the concentration of calcium and magnesium ions is lower than 5000mg/L and the temperature is lower than 120°C, the foam can be kept stable, and the recovery rate can be significantly improved. It is suitable for the secondary development of high-temperature and high-salt conventional sandstone reservoirs.

(2) The three-phase foam system for oil displacement provided by the present invention forms a gas-liquid-solid three-phase foam system by introducing solid-phase particle fly ash, which can block high water content and high permeability areas, and make the displacement fluid It can be used for secondary development after water flooding and gas flooding of conventional sandstone reservoirs, which have been transferred to low-permeability and high-oil-bearing areas that have not been affected before. Anionic surfactants and positively charged fly ash particles in three-phase foam systems for oil displacement can have a synergistic effect. Part of the anionic surfactant is adsorbed on the surface of fly ash particles, which enhances the hydrophobicity of fly ash particles, arranges on the gas-liquid interface instead of entering the liquid phase, thereby enhancing the stability of the foam. Fly ash has poor suspensibility and is prone to sedimentation after being dispersed in the solution, so it is necessary to add sodium soil into the system as a dispersant. Sodium soil is negatively charged, and fly ash is positively charged, and the two are prone to attract. The sodium soil is attached to the fly ash particles, which reduces the density of the particles and enhances the suspension, which can maintain stability for a longer time and improve the three Phase foam properties.

(3) The preparation method provided by the invention has mild technical conditions, is simple and easy to implement, has environmental friendliness and broad market development potential.

Description of drawings

Fig. 1 is the principle schematic diagram that fly ash improves foam stability;

Figure 2 is a diagram showing the influence of sodium soil on the suspension of fly ash; it is obvious that after adding sodium soil, the settling time of fly ash suspension is delayed by 3 hours, and the particle size of fly ash is micron, and the suspension is poor, so sodium soil is selected as the suspending agent , attached to the fly ash particles, which can effectively delay the settling time of the suspension.

Fig. 3 is the data of the core displacement experiment; in the stage of foam flooding, the water cut decreases, the injection pressure increases, and the recovery factor increases, indicating that the invention can play the role of adjusting the injection profile, increasing the injection pressure, and increasing the recovery factor; at 80 Under the conditions of ℃, NaCl concentration of 100000mg/L, and calcium and magnesium ion concentration of 500mg/L, the oil recovery rate is 39.15% higher than that of water flooding;

Fig. 4 is the comparison chart of the foam properties of the three-phase foam system for oil displacement prepared in Examples 1-4; obviously, the temperature, salinity and formula content are different in different embodiments, and the obtained foam properties are different, and the liquid separation volume of 50mL corresponds to The time is the liquid analysis half-life, and the foam half-life corresponding to Embodiment 1-4 is respectively 34min, 31min, 25min, 19min;

Fig. 5 is a schematic diagram of the core displacement experimental device.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the specific implementation manners of the present invention will be further described in detail below in conjunction with specific examples and accompanying drawings.

Embodiment 1-4 uses core displacement experiment to complete the determination of oil recovery

The schematic diagram of the core displacement experiment device is shown in Figure 5, and the specific test steps are as follows:

(1) Vacuumize the used core (heterogeneous core with a permeability of 200mD/1600mD), and then saturate it with formation water.

(2) The temperature of the incubator is raised to the experimental temperature, and the back pressure at the end is atmospheric pressure, and the ring pressure is set at 5 MPa.

(3) The core is saturated with oil, and aged in a constant temperature box for 12 hours.

(4) Water flooding 1PV, CO ₂ flooding 0.5PV, foam flooding 0.5PV, and subsequent CO ₂ flooding 0.5PV.

(5) Foam flooding adopts a foam generator to foam, and injects the core after generating foam.

(6) Water flooding, CO ₂ flooding, foam flooding, and subsequent CO ₂ flooding in sequence. Record the pressure, oil production and water production at each moment until the end of the test.

Example 1

Step S1, pour a certain amount of deionized water into a beaker, add inorganic salt into the beaker, and prepare an inorganic salt solution with 100000 mg/L NaCl and 500 mg/L calcium and magnesium ion concentration;

Step S2, place the beaker on a magnetic stirrer, set the speed at 350r/min, add 0.5 parts by mass of anionic surfactant AOS to the beaker, and stir for 30 minutes until completely dissolved;

Step S3, adding 0.3 parts by mass of zwitterionic surfactant CHSB to the beaker, stirring for 30 minutes until completely dissolved;

Step S4, adding 2.5 parts by mass of dispersant sodium soil into the beaker, stirring for 30 minutes to make it fully suspended;

Step S5, adding 5 parts by mass of solid-phase particle fly ash to the beaker, stirring for 30 minutes to make it fully suspended;

Step S6, sealing the stirred foaming solution with a plastic wrap, placing it in an incubator, and aging at 80°C for 48 hours;

Step S7, transferring the aged foaming liquid to a high-speed stirrer, passing CO ₂ gas into it for 10 min, setting the rotation speed at 8000 r/min, and stirring for 2 min.

100ml of foaming fluid produced by the Blender-Waring method has a foam volume of 350mL and a half-life of 34min. After water flooding and CO ₂ gas flooding, 0.5PV foam is injected and then CO ₂ gas flooding. The final oil recovery rate is 70.78%. Water flooding increased by 39.15%.

Example 2

Step S1, pouring a certain amount of deionized water into a beaker, adding inorganic salts to the beaker according to actual requirements, and preparing an inorganic salt solution of 150000 mg/L NaCl;

Step S2, place the beaker on a magnetic stirrer, set the speed at 350r/min, add 0.5 parts by mass of anionic surfactant SDBS into the beaker, and stir for 30 minutes until completely dissolved;

Step S3, adding 0.3 parts by mass of zwitterionic surfactant CHSB to the beaker, stirring for 30 minutes until completely dissolved;

Step S4, adding 2.5 parts by mass of dispersant sodium soil into the beaker, stirring for 30 minutes to make it fully suspended;

Step S5, adding 5 parts by mass of solid-phase particle fly ash to the beaker, stirring for 30 minutes to make it fully suspended;

Step S6, sealing the stirred foaming solution with a plastic wrap, placing it in an incubator, and aging at 80°C for 48 hours;

Step S7, transferring the aged foaming liquid to a high-speed stirrer, passing CO ₂ gas into it for 10 min, setting the rotation speed at 8000 r/min, and stirring for 2 min.

100ml of foaming fluid produced by the Blender-Waring method has a foam volume of 330mL and a half-life of 31min. After water flooding and CO ₂ gas flooding, 0.5PV foam is injected and then CO ₂ gas flooding, the final oil recovery rate is 36.67%, compared with Water flooding increased by 36.67%.

Example 3

Step S1, pour a certain amount of deionized water into the beaker, add inorganic salts into the beaker according to actual requirements, and prepare a solution with a calcium and magnesium ion concentration of 5000 mg/L;

Step S2, place the beaker on a magnetic stirrer, set the speed at 350r/min, add 0.5 parts by mass of anionic surfactant AOS to the beaker, and stir for 30 minutes until completely dissolved;

Step S3, adding 0.3 parts by mass of zwitterionic surfactant CHSB to the beaker, stirring for 30 minutes until completely dissolved;

Step S4, adding 2.5 parts by mass of dispersant sodium soil into the beaker, stirring for 30 minutes to make it fully suspended;

Step S5, adding 5 parts by mass of solid-phase particle fly ash to the beaker, stirring for 30 minutes to make it fully suspended;

Step S6, sealing the stirred foaming solution with a plastic wrap, and placing it in an incubator for aging at 80°C for 48 hours;

Step S7, transferring the aged foaming liquid to a high-speed stirrer, passing CO ₂ gas into it for 10 min, setting the rotation speed at 8000 r/min, and stirring for 2 min.

100ml of foaming fluid produced by the Blender-Waring method has a foam volume of 310mL and a half-life of 25min. After water flooding and CO ₂ gas flooding, 0.5PV foam is injected and then CO ₂ gas flooding. The final oil recovery rate is 63.66%, compared with Water flooding increased by 32.52%.

Example 4:

Step S1, pouring a certain amount of deionized water into a beaker, adding inorganic salts to the beaker according to actual requirements, and preparing an inorganic salt solution with 100000 mg/L NaCl and 500 mg/L calcium and magnesium ion concentration;

Step S2, place the beaker on a magnetic stirrer, set the speed at 350r/min, add 0.5 parts by mass of anionic surfactant AOS to the beaker, and stir for 30 minutes until completely dissolved;

Step S3, adding 0.3 parts by mass of zwitterionic surfactant CHSB to the beaker, stirring for 30 minutes until completely dissolved;

Step S4, adding 2.5 parts by mass of dispersant sodium soil into the beaker, stirring for 30 minutes to make it fully suspended;

Step S5, adding 5 parts by mass of solid-phase particle fly ash to the beaker, stirring for 30 minutes to make it fully suspended;

Step S6, sealing the stirred foaming solution with a plastic wrap, placing it in an incubator, and aging it at 120°C for 48 hours;

Step S7, transferring the aged foaming liquid to a high-speed stirrer, passing CO ₂ gas into it for 10 min, setting the rotation speed at 8000 r/min, and stirring for 2 min.

100ml of foaming fluid produced by the Blender-Waring method has a volume of 320mL of foam and a half-life of 19 minutes. After water flooding and CO ₂ gas flooding, 0.5PV foam is injected and then CO ₂ gas flooding. The final oil recovery rate is 60.82%. Water flooding increased by 28.37%.

In the case of no conflict, the above-mentioned embodiments and features in the embodiments herein may be combined with each other.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (6)

1. A method for preparing a three-phase foam system for temperature-resistant and salt-resistant flooding, characterized in that, comprising the following steps: S1. Pour 100 parts by mass of deionized water into a container, add inorganic salts into the container, and prepare simulated formation water; S2. Place the container on a magnetic stirrer, set the first preset speed, add 0.5 parts by mass of sodium α-olefin sulfonate to the container, and stir until completely dissolved; S3. Add 0.3 parts by mass of cocamidopropyl sulfobetaine to the container, and stir until completely dissolved; S4, add 2.5 parts by mass of sodium soil to the container, stir to make it fully suspended; S5. Add 5 parts by mass of fly ash to the container, stir to make it fully suspended, and obtain a foaming liquid; S6, seal the stirred foaming solution with a plastic wrap, and place it in an incubator for aging; S7. Transfer the aged foaming liquid to a high-speed stirrer, set the second preset rotation speed, pass carbon dioxide into it for 10 minutes, and stir for 2 minutes to obtain the product. 2. The preparation method according to claim 1, wherein the first preset rotation speed is 350r/min~400r/min, and the second preset rotation speed is 6000r/min~8000r/min. 3. The preparation method according to claim 1, characterized in that, the aging time in step S6 is 48h~60h. 4. A temperature-resistant and salt-resistant three-phase foam system for oil flooding, characterized in that it is prepared by the preparation method according to any one of claims 1-3. 5. The application of the temperature-resistant and salt-resistant three-phase foam system for oil flooding as claimed in claim 4, characterized in that, the temperature-resistant and salt-resistant three-phase foam system for oil flooding is used to prepare oilfield foam control and displacement agents. 6. The application according to claim 5, wherein the three-phase foam system is applied at a temperature not higher than 80° C., a sodium ion concentration not higher than 100,000 mg/L, and a calcium and magnesium ion concentration not higher than 500 mg/L. Secondary development of sandstone reservoirs in L.

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