阅读说明：本技术 一种适用于油藏提高采收率的驱油剂及其制备方法和应用 (Oil displacement agent suitable for increasing recovery ratio of oil reservoir and preparation method and application thereof ) 是由 陈光进 孙长宇 张宇 伍锡道 范存帅 秦慧博 肖鹏 于 2020-09-02 设计创作，主要内容包括：本发明提供了一种适用于油藏提高采收率的驱油剂及其制备方法和应用。本发明的驱油剂以重量份计,包括70～85份的液态二氧化碳、15～30份的水和0.15～0.9份的表面活性剂。本发明的驱油剂在室温下能够形成稳定的微乳液体系,同时具有良好的耐温性、耐盐性和极低的界面张力,在含盐条件下,本发明驱油剂的微乳液体系依然具有良好的稳定性,且界面张力并无升高。采用本发明的驱油剂进行驱油,能够延缓气体突破的时间,注入性能良好,能够极大降低CO-2的气窜,提高波及系数；成本低廉,操作方法简便,适用于多种类型的油藏,对地层损害小,尤其针对原油为高黏度的稠油油藏,可显著提高采收率。(The invention provides an oil displacement agent suitable for increasing the recovery ratio of an oil reservoir and a preparation method and application thereof. The oil displacement agent comprises, by weight, 70-85 parts of liquid carbon dioxide, 15-30 parts of water and 0.15-0.9 part of surfactant. The oil displacement agent can form a stable microemulsion system at room temperature, has good temperature resistance, salt resistance and extremely low interfacial tension, and still has good stability and no increase of interfacial tension under the condition of salt. The oil displacement agent provided by the invention can be used for oil displacement, can delay the gas breakthrough time, has good injection performance, and can greatly reduce CO 2 By the gas channelingThe sweep coefficient is improved; the method has the advantages of low cost, simple and convenient operation method, suitability for various types of oil reservoirs, small damage to stratum, and capability of obviously improving the recovery ratio especially for heavy oil reservoirs with high viscosity of crude oil.)

1. An oil-displacing agent, which comprises the following components in parts by weight:

70-85 parts of liquid carbon dioxide;

15-30 parts of water;

0.15-0.9 parts of surfactant.

2. The oil-displacing agent of claim 1, wherein the surfactant comprises a nonionic alkyl glycoside surfactant.

3. The oil displacing agent of claim 2, wherein the non-ionic alkyl glycoside surfactant comprises a combination of one or more of alkyl glycoside-0810, alkyl glycoside-0814, alkyl glycoside-1214, and alkyl glycoside-1216.

4. A method for preparing an oil-displacing agent as claimed in any one of claims 1 to 3, comprising the steps of:

uniformly mixing water and a surfactant, and adding the mixture into a stirring kettle;

vacuumizing the stirring kettle, connecting a tank body loaded with liquid carbon dioxide, introducing the liquid carbon dioxide into the stirring kettle, and continuously stirring to form stable emulsion, namely the oil displacement agent.

5. The method of claim 4, wherein liquid carbon dioxide is pumped into the stirred tank using a constant speed and constant pressure pump; the temperature of the introduced liquid carbon dioxide is less than 30 ℃, and the introducing speed is 10-20 mL/min.

6. The method according to claim 4, wherein the rotation speed of the continuous stirring is 500-1000 r/min, and the stirring time is more than or equal to 2 h.

7. The process according to claim 6, wherein the stirring is continued at a speed of 1000r/min for a period of 2 h.

8. The method of claim 4, wherein the pressure in the stirred tank is greater than 10MPa and the temperature in the stirred tank is less than 30 ℃ during the continuous stirring.

9. Use of the oil displacement agent of any one of claims 1-3 for enhanced oil recovery in reservoir displacement oil recovery.

10. The use according to claim 9, wherein the temperature of the reservoir is above 50 ℃, the reservoir is a crude oil reservoir, and the viscosity of the crude oil is 10-10000 mPa-s.

Technical Field

The invention belongs to the technical field of oil field composite flooding, and particularly relates to an oil displacement agent suitable for increasing the recovery ratio of an oil reservoir, and a preparation method and application thereof.

Background

With the rapid development of industry, the social demand of petroleum is increasingly increased, and how to extract more crude oil from developed oil reservoirs becomes important research content. However, for some special oil reservoirs, the conventional exploitation method is difficult to achieve high recovery efficiency, and a large amount of residual oil still exists after exploitation. The viscosity of the flowable thick oil is usually as high as thousands of mPas or even tens of thousands of mPas, and the difference of the fluidity ratio of the thick oil and water is large under the condition, so that the water fingering occurs, and the effective displacement and the low crude oil recovery rate cannot be achieved.

In recent years, CO has been used₂The oil displacement agent is increasingly attracting attention as an oil displacement agent for injection into oil reservoirs. The method can greatly improve the recovery ratio of crude oil, and simultaneously can realize the sequestration of greenhouse gases. CO 2₂The dissolution of the oil can expand the crude oil, reduce the tension of an oil-water interface, reduce the saturation of residual oil and further improve the recovery ratio. But for CO under normal reservoir conditions₂Displacement, large injection slug amount and high investment; at the same time for CO under the condition of heavy oil reservoir₂Displacement, large injection slug amount, easy gas channeling and difficult realization of crude oil and CO₂The actual recovery ratio is lower.

Disclosure of Invention

Based on the currentThe invention has the defects of the prior art, and the first aim of the invention is to provide an oil displacement agent suitable for increasing the recovery ratio of an oil reservoir, which is a microemulsion system formed by liquid carbon dioxide, water and a surfactant, and has good stability, temperature resistance, salt resistance and extremely low interfacial tension. The second purpose of the invention is to provide a preparation method of the oil displacement agent; the third purpose of the invention is to provide the application of the oil displacement agent in oil displacement and recovery of oil in oil reservoirs, compared with the prior art, the CO can be greatly reduced₂Possibility of gas channeling, CO₂Provides more sufficient contact time with oil, delays the gas breakthrough time, further reduces the interfacial tension between oil and water, and effectively improves the crude oil recovery ratio.

The purpose of the invention is realized by the following technical means:

in one aspect, the invention provides an oil displacement agent, which comprises the following components in parts by weight:

70-85 parts of liquid carbon dioxide;

15-30 parts of water;

0.15-0.9 parts of surfactant.

The oil displacement agent can form a stable microemulsion system at room temperature (lower than 30 ℃) and under the pressure of more than 10MPa, can be stored well, and has good temperature resistance, salt resistance and extremely low interfacial tension. The oil displacement agent provided by the invention can be used for oil displacement, can delay the gas breakthrough time, has good injection performance, and can greatly reduce CO₂The gas channeling is realized, and the sweep coefficient is improved; the method has the advantages of low cost, simple and convenient operation method, suitability for various types of oil reservoirs, small damage to stratum, and capability of remarkably improving the recovery ratio especially for the oil reservoir with high temperature and high viscosity.

In the above oil-displacing agent, the surfactant preferably includes a nonionic alkyl glycoside surfactant or the like.

In the oil displacement agent, the nonionic alkyl glycoside surfactant preferably includes a combination of one or more of alkyl glycoside-0810, alkyl glycoside-0814, alkyl glycoside-1214, alkyl glycoside-1216, and the like, but is not limited thereto.

The adopted surfactant is the green and environment-friendly nonionic surfactant alkyl glycoside, can be biodegraded, and is beneficial to protecting the environment; furthermore, alkyl glycoside surfactants with liquid CO₂After the emulsion is compounded, the compatibility is excellent, the emulsion has longer stable time, furthermore, the stability of the emulsion can not be damaged even after salt is added into an emulsion system, and the interfacial tension between the emulsion system after the salt is added and an oil phase is not increased.

On the other hand, the invention also provides a preparation method of the oil displacement agent, which comprises the following steps:

uniformly mixing water and a surfactant, and adding the mixture into a stirring kettle;

vacuumizing the stirring kettle, connecting the tank body loaded with liquid carbon dioxide, introducing the liquid carbon dioxide into the stirring kettle, and continuously stirring to form stable emulsion, namely the oil displacement agent.

In the method, preferably, a constant-speed constant-pressure pump is adopted to introduce liquid carbon dioxide into the stirring kettle, the temperature of the introduced liquid carbon dioxide is less than 30 ℃ (for example, normal temperature condition), and the introduction speed is 10-20 mL/min. The pressure of the introduced gas is sufficient for carbon dioxide liquefaction, for example: 20 MPa.

In the method, the rotation speed of the continuous stirring is preferably 500-1000 r/min, and the stirring time is preferably more than or equal to 2 h.

In the above method, the rotation speed of the continuous stirring is preferably 1000r/min, and the stirring time is preferably 2 h.

In the above method, preferably, the pressure in the stirred tank is more than 10MPa (the increase in pressure helps to increase the stability of the emulsion) and the temperature in the stirred tank is less than 30 deg.C (e.g., room temperature) during the continuous stirring.

In another aspect, the invention also provides application of the oil displacement agent in oil reservoir displacement oil recovery to improve the recovery ratio.

In the application, preferably, the temperature of the oil reservoir is higher than 50 ℃, the oil reservoir is a crude oil reservoir, and the viscosity of the crude oil is 10-10000 mPa · s.

The invention has the beneficial effects that:

(1) the oil displacement agent can form a stable microemulsion system at room temperature, has good temperature resistance, salt resistance and extremely low interfacial tension, and still has good stability and no increase of interfacial tension under the condition of high temperature and salt.

(2) The oil displacement agent provided by the invention can be used for oil displacement, can delay the gas breakthrough time, has good injection performance, and can greatly reduce CO₂The gas channeling is realized, and the sweep coefficient is improved; reduce CO₂The application amount of the oil is low, the cost is low, the operation method is simple and convenient, the oil is suitable for various types of oil reservoirs, the damage to the stratum is small, and particularly, the recovery ratio can be obviously improved for the heavy oil reservoir with high viscosity of crude oil.

Drawings

FIG. 1 is a macroscopic view of the oil-displacing agent prepared in example 1 of the present invention.

Fig. 2 is a comparison graph of interfacial tension between the oil-displacing agent 1, the oil-displacing agent 2, and the oil-displacing agent 3 in example 4 of the present invention and an oil phase under different conditions.

FIG. 3 is a comparison graph of the tubule displacement production degree curves of 2 different displacement agents in total, namely emulsion displacement and carbon dioxide displacement, adopting the oil displacement agent of example 3 in example 5 of the invention.

Fig. 4 is a comparison graph of the tubule displacement production degree curves of 4 different displacement agents including emulsion displacement, carbon dioxide displacement, water displacement and surfactant displacement using the oil displacement agent of example 1 in example 6 of the present invention.

Detailed Description

The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.

Example 1:

the embodiment provides an oil displacement agent and a preparation method thereof, and the oil displacement agent comprises the following specific preparation steps:

(1) weighing 30g of water by using a beaker, adding 3 wt% (namely 0.9g) of surfactant alkyl glycoside-0810, stirring to completely dissolve the water, and transferring the prepared water solution into a stirring kettle with a piston;

(2) after the stirred tank is installed and vacuumized for 10min, the pipeline is connected to the liquid CO₂The tank body adopts a constant-speed constant-pressure pump to introduce liquid CO into the stirring kettle₂Introduction of liquid CO₂The temperature of (2) is 20 ℃, the introducing speed is 15mL/min, the introducing pressure is 20MPa, and the liquid CO is₂The flow rate was 70g (74.70 mL in volume at 20 ℃ C. and 20 MPa).

(3) And (3) closing the valve, connecting the stirring kettle with a constant-speed and constant-pressure pump, starting stirring, and continuously stirring at the rotating speed of 1000r/min for 2 hours under the pressure of 10MPa to form stable microemulsion, namely obtaining the oil displacement agent of the embodiment.

The oil displacement agent prepared in this example was subjected to a stability test, specifically as follows:

and (3) transferring the prepared oil displacement agent into the high-pressure visible kettle under the constant pressure of 10MPa through a pipeline for stability test. After stirring, a milky white microemulsion was formed, and after standing for 1.5h, photographs were taken, and the results are shown in fig. 1. From FIG. 1 it can be seen that the microemulsion formed is more stable without sharp interfaces.

Example 2:

the embodiment provides an oil displacement agent and a preparation method thereof, and the oil displacement agent comprises the following specific preparation steps:

(1) weighing 30g of water by using a beaker, adding 1 wt% (namely 0.3g) of alkyl glucoside-0810 serving as a surfactant, stirring to completely dissolve the water, and transferring the prepared water solution to a stirring kettle with a piston;

(2) after the stirred tank is installed and vacuumized for 10min, the pipeline is connected to the liquid CO₂The tank body adopts a constant-speed constant-pressure pump to introduce liquid CO into the stirring kettle₂Introduction of liquid CO₂The temperature of (2) is 20 ℃, the introducing speed is 15mL/min, the introducing pressure is 20MPa, and the liquid CO is₂The flow rate was 70g (74.70 mL in volume at 20 ℃ C. and 20 MPa).

(3) And (3) closing the valve, connecting the stirring kettle with a constant-speed and constant-pressure pump, starting stirring, and continuously stirring at the rotating speed of 500r/min for 4 hours under the pressure of 10MPa to form stable microemulsion, namely obtaining the oil displacement agent of the embodiment.

The oil displacement agent prepared in this example was subjected to a stability test, specifically as follows:

and (3) transferring the prepared oil displacement agent into the high-pressure visible kettle under the constant pressure of 10MPa through a pipeline for stability test. After stirring, milky microemulsion is formed, and after standing for 1.5h, the formed microemulsion is relatively stable.

Example 3:

the embodiment provides an oil displacement agent prepared under a salt-containing condition, and the oil displacement agent is prepared by the following specific steps:

(1) weighing 15g of water by using a beaker, adding 2 wt% (namely 0.3g) of alkyl glycoside-0810 surfactant and 3 wt% (namely 0.45g) of sodium chloride, stirring to completely dissolve the water, and transferring the prepared water solution to a stirring kettle with a piston;

(2) after the stirred tank is installed and vacuumized for 10min, the pipeline is connected to the liquid CO₂The tank body adopts a constant-speed constant-pressure pump to introduce liquid CO into the stirring kettle₂Introduction of liquid CO₂The temperature of (2) is 20 ℃, the feeding speed is 15ml/min, the feeding pressure is 20MPa, and liquid CO is₂The flow rate was 85g (90.71 mL in volume at 20 ℃ C. and 20 MPa).

(3) And (3) closing the valve, connecting the stirring kettle with a constant-speed and constant-pressure pump, starting stirring, and continuously stirring at the rotating speed of 800r/min for 3 hours under the pressure of 15MPa to form stable microemulsion, namely obtaining the oil displacement agent of the embodiment.

The oil displacement agent prepared in this example was subjected to a stability test, specifically as follows:

and (3) transferring the prepared oil displacement agent into the high-pressure visible kettle under the constant pressure of 15MPa through a pipeline for stability test. After stirring, the stable milky microemulsion is still formed under the condition of 3 wt% of salt content, and after standing for 1h, no obvious interface exists, and the formed microemulsion is relatively stable.

Therefore, the oil displacement agent can still form a better microemulsion system after the salt component is added, and has better salt resistance.

Example 4: interfacial tension test

This example uses the preparation methods of example 1, example 2 and example 3 to prepare different emulsions for interfacial tension testing with oil phase.

The oil-displacing agent prepared in example 1 was designated as oil-displacing agent 1; the oil-displacing agent prepared in example 2 was named oil-displacing agent 2; the oil-displacing agent formulated in example 3 was designated oil-displacing agent 3.

Before experimental test, the high-pressure chamber and the sample injection pipeline are cleaned. The prepared oil displacement agent is used as a titration phase, diesel oil is used as a surrounding phase and is injected into a high-pressure cabin, and the interfacial tension test of the oil displacement agent and the oil phase at different pressures is carried out at 2 experimental temperatures (70 ℃ and 90 ℃). The experimental result is shown in fig. 2, and it can be seen that the interfacial tension between the oil-displacing agent and the oil phase is reduced to about 2mN/m at high temperature and high pressure, and the interfacial tension between the two phases is stable under different system pressures, and the interfacial tension is not increased along with the temperature rise, which indicates that the oil-displacing agent is suitable for displacement under high temperature conditions, and the oil-displacing agent added with the salt component in example 3 does not have a great influence on the interfacial tension, indicating that the oil-displacing agent of the present invention has a good salt tolerance effect.

Example 5: contrast experiment for injecting different oil displacement agents into thin pipe for displacement

The oil displacement agent prepared in example 3 was used for a thin-tube displacement experiment, and the crude oil used was a conventional crude oil having a density of 0.8673g/cm in a standard state (20 ℃ C., 0.101325MPa)³The viscosity was 12.94 mPas.

At an experimental temperature of 90 ℃ and a predetermined displacement pressure of 15MPa, at 6.00cm³The oil displacement agent of example 3 displaced the crude oil in the tubule model at a constant velocity/h. And when a certain amount of oil displacement agent is injected, collecting the oil and gas product produced by metering, recording the reading, injection pressure and back pressure of the pump, and observing the phase state and color change of the fluid through a high-pressure observation window. When the oil is injected into the reservoir in an accumulated way, the pore volume is 1.2 times that of the reservoirAfter the preparation, the displacement is stopped, and the extraction degree is calculated.

Under the same displacement conditions, the oil displacement agent is replaced by carbon dioxide gas to carry out a thin-tube displacement experiment. The results of the production level experiments for 2 different displacement agents are shown in figure 3.

As can be seen from the recovery data in fig. 3, the recovery ratio of the displacement agent provided in example 3 for conventional crude oil displacement is 83.56%, which is better than that of carbon dioxide gas displacement alone (the recovery ratio is 72.26%), indicating that the displacement agent provided by the present invention can also better enhance the recovery ratio of crude oil for crude oil with conventional viscosity.

Example 6: contrast experiment for injecting different oil displacement agents into thin pipe for displacement

The oil displacement agent prepared in example 1 was used for a thin-tube displacement experiment, and the crude oil used was a high-viscosity thick oil having a density of 0.9508g/cm under a standard condition (20 ℃ C., 0.101325MPa)³The viscosity was 8119.40 mPas.

At an experimental temperature of 70 ℃ and a predetermined displacement pressure of 13MPa, at 6.00cm³The oil displacing agent of example 1 displaced the crude oil in the tubule model at a constant velocity/h. And when a certain amount of oil displacement agent is injected, collecting the oil and gas product produced by metering, recording the reading, injection pressure and back pressure of the pump, and observing the phase state and color change of the fluid through a high-pressure observation window. And after the oil displacement agent with the pore volume of 1.2 times is injected in an accumulated manner, stopping displacement and calculating the extraction degree.

Under the same displacement conditions as described above, the oil-displacing agent of the present invention was replaced with water, carbon dioxide gas, and water containing 3 wt% of a surfactant (alkylglycoside-0810), and a thin-tube displacement experiment was performed. The results of the extent of production experiments for the 4 different displacement agents are shown in figure 4.

As can be seen from the recovery ratio data in fig. 4, when the oil displacement agent provided in example 1 is used for displacing high-viscosity heavy oil, the recovery ratio is as high as 73.96%, which is far better than that of carbon dioxide gas flooding (recovery ratio 57.04%), water flooding (recovery ratio 47.92%) or surfactant flooding (recovery ratio 52.12%) alone, and it can be known that the recovery ratio of the heavy oil can be significantly improved by using the oil displacement agent provided by the present invention.

Example 7: core displacement experiment

Selecting and drying a compact sandstone core, filling the core into a high-temperature-resistant and corrosion-resistant plastic sleeve, then putting the core into a core holder, applying confining pressure of 5-6 MPa, and vacuumizing for 10 hours. And (3) saturating the formation water, setting the formation temperature to be 90 ℃, sealing, heating to a constant temperature by using a constant temperature box, and measuring the permeability by using water. The crude oil samples in example 5 were selected as the formation pressure, saturated oil and oil samples produced by increasing confining pressure step by step.

And (3) calculating the original oil saturation, setting back pressure through a back pressure valve, injecting the oil displacement agent in the embodiment 1 at a constant speed, recording the injection pressure and the volume of liquid and gas at the outlet end, and calculating the displacement recovery ratio of the oil displacement agent.

And replacing the oil displacement agent with carbon dioxide gas to perform a core displacement experiment under the same conditions.

Comparing the results of the core displacement experiment of injecting the oil displacement agent and the carbon dioxide gas in example 1 under the same conditions, the ultimate recovery rate of the core displacement by using the oil displacement agent in example 1 is 41.25%, and the ultimate recovery rate of the core displacement by using the carbon dioxide gas is 22.05%, which can increase the crude oil recovery rate by about 20%.

From the above experimental data, it can be known that the recovery ratio can be increased by about 10% for the conventional crude oil selected in example 5; the oil displacement is carried out on the crude oil with the viscosity as high as 8119.40 mPa.s selected in the examples 6 and 7, and the recovery ratio can be improved by more than 20 percent, so that the oil displacement agent disclosed by the invention has the effect of improving the recovery ratio on various oil reservoirs, and the recovery ratio is greatly improved particularly on the heavy oil reservoir with the high viscosity of the crude oil.