Device and method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2

Abstract

The present invention discloses a device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2; a transparent graduated tube is arranged in a visual container, and a five-way valve is respectively connected to the visual container, the CO2 high-pressure container, one end of the intermediate container, the pressure sensor and the atmosphere; a balance is arranged below the CO2 high-pressure container; a piston is arranged in the intermediate container; and a three-way valve is respectively connected to the other end of the intermediate container, the high-pressure pump and the atmosphere. The device of the present invention has a simple structure and is easy to build. Through the ingenious design of the experimental device and the simple experimental process, the expansion rate and the extraction rate can be obtained while considering the expansion and extraction effects at the same time, which is more instructive for the actual oil recovery process than the results obtained by a single expansion experiment and an extraction experiment. During the test process, various factors and conditions such as temperature, pressure, and the mass ratio of CO2 to oil can be controlled and changed, which can provide more comprehensive guidance for the design parameters of CO2 development on the oil field site.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development and gas injection to enhance recovery, and in particular to a device and method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2. Background Art

[0002] In addition to reducing carbon emissions, how to efficiently use CO2 has become a hot topic of concern. In the process of oil field development, injecting CO2 into the ground can not only be used to increase crude oil production, but also to store CO2 underground. Therefore, how to efficiently use CO2 to increase crude oil recovery has become an important way to reduce carbon emissions and increase oil production.

[0003] There are many mechanisms for CO2 to improve oil recovery, including dissolving in crude oil to expand the volume of crude oil, reducing crude oil viscosity, reducing interfacial tension, extracting light components from crude oil, dissolved gas drive and miscible effects, etc. Especially for the development of tight oil reservoirs and shale oil reservoirs, after horizontal wells and repeated fracturing, the recovery rate is only about 10%, but the fracture network has been formed. How to use CO2 to improve the recovery rate and give full play to the expansion and extraction effect of CO2 on crude oil will become an important method for subsequent production increase.

[0004] At present, most of the research reports on the expansion and extraction of crude oil by CO2 are about the expansion or extraction effect. In the actual process, expansion and extraction occur simultaneously in the process of equilibrium between CO2 and crude oil. The two will affect each other at the same time. The separate study of expansion and extraction cannot truly reflect the real effect between CO2 and crude oil. Some literature has reported the expansion and extraction experiment of liquid CO2 on crude oil. This method can only measure the volume of heavy and light phase components. Before mixing with crude oil, CO2 will form a heavy phase and a light phase. Both phases are a mixture of crude oil and CO2, but the heavy phase is mainly crude oil and the light phase is mainly CO2. This method cannot obtain the specific content of crude oil and CO2 in the heavy phase and light phase. At the same time, it is inaccurate to distinguish expansion and extraction by the volume change of heavy phase and light phase, because with the increase of pressure, the extraction effect is enhanced, the volume of light phase increases and the volume of heavy phase decreases. The reduction of the volume of heavy phase is not caused by the weakening of expansion effect, but more oil is extracted into the light phase. Therefore, the magnitude of the expansion and extraction effects cannot be accurately evaluated only by the volume changes of the heavy and light phases. Numerical simulation methods can calculate the phase state of the CO2 and crude oil system, but the selection of the interaction parameters between crude oil and CO2 is very critical and often needs to be obtained through experiments. Without reliable interaction parameters, the calculated extraction and expansion effects have little practical guidance significance. Summary of the invention

[0005] In view of this, the present invention provides a device and method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2. The device is easy and quick to assemble. The method can quickly and accurately measure and evaluate the expansion rate and extraction rate of crude oil by CO2 under different pressures, temperatures and CO2 and oil compositions through experiments. The measurement data is accurate and the test cost is low.

[0006] Specifically, the following technical solutions are included:

[0007] In a first aspect, the present invention discloses a device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2, comprising a visual container, a transparent graduated tube, a stirring device, a first valve, a second valve, a third valve, a fourth valve, a fifth valve, a sixth valve, an intermediate container, a CO2 high-pressure container, a piston, a high-pressure pump, a balance, a pressure sensor, a constant temperature control system, a five-way valve, a three-way valve, a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a fifth pipeline, a sixth pipeline, a seventh pipeline and an eighth pipeline;

[0008] A transparent graduated tube is arranged in the visual container, the upper end of the transparent graduated tube is open, and a stirring device is arranged in the transparent graduated tube;

[0009] The visible container is connected to the five-way valve through the first pipeline, and the first valve is provided on the first pipeline;

[0010] The five-way valve is connected to the CO2 high-pressure container through the second pipeline, and the second valve is provided on the second pipeline;

[0011] The balance is arranged below the CO2 high pressure container;

[0012] The intermediate container is provided with a piston, and the piston divides the intermediate container into a first chamber and a second chamber that are not connected; the five-way valve is connected to the first chamber of the intermediate container through the third pipeline, and the third pipeline is provided with the third valve;

[0013] The five-way valve is connected to the atmosphere through the fourth pipeline, and the fourth pipeline is provided with the fourth valve;

[0014] The five-way valve is connected to the pressure sensor through the fifth pipeline;

[0015] The second chamber of the intermediate container is connected to the three-way valve through the sixth pipeline;

[0016] The three-way valve is connected to the high-pressure pump through the seventh pipeline, and a fifth valve is provided on the seventh pipeline;

[0017] The three-way valve is connected to the atmosphere through the eighth pipeline, and a sixth valve is provided on the eighth pipeline.

[0018] In one possible design, the visual container, the transparent graduated tube, the stirring device, the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, the intermediate container, the CO2 high-pressure container, the piston, the high-pressure pump, the balance, the pressure sensor, the five-way valve, the three-way valve, the first pipeline, the second pipeline, the third pipeline, the fourth pipeline, the fifth pipeline, the sixth pipeline, the seventh pipeline and the eighth pipeline are all arranged in the constant temperature control system.

[0019] In a possible design, a stopper is provided at the opening of the transparent graduated tube, and a vent hole is provided on the stopper.

[0020] In a second aspect, the present invention also discloses a method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2, comprising the following steps:

[0021] S1. Add a set volume V0 of oil phase into the transparent graduated tube under normal pressure. The mass of the oil phase is recorded as m1.

[0022] S2, add the transparent graduated tube into the visual container, ensure that the liquid level is visible, connect the pipelines, close all valves, turn on the constant temperature control system, set the temperature, and turn on the stirring device;

[0023] S3, opening the first valve, the second valve, the third valve, and the sixth valve, and passing the CO2 in the CO2 high-pressure container into the first chambers of the visual container and the intermediate container, so that the piston in the intermediate container is pushed to one end close to the three-way valve;

[0024] S4. Record the mass of CO2 introduced into the visual container, the first chamber and the corresponding pipeline by a balance as m g ;

[0025] S5, close all valves, open the first valve, the third valve and the fifth valve, start the high-pressure pump, push the piston of the intermediate container toward the end close to the five-way valve, dissolve CO2 in the oil phase, and when the pressure sensor reaches the set pressure P1, record the liquid level of the oil phase in the transparent graduated tube at this time and calculate the volume V of the oil phase at this time P1 ;

[0026] S6. Close all valves, open the first valve and the fourth valve, and quickly discharge the CO2 in the visual container. When the pressure in the visual container becomes normal pressure, record the liquid level of the oil phase in the transparent graduated tube at this time and calculate the volume V' of the oil phase at this time. P1 ;

[0027] S7, calculate the mass ratio of CO2 to oil phase under the condition of pressure P1, m g: The expansion rate α and extraction rate β of unit mass CO2 in the system composed of m1;

[0028] The extraction volume (V) of CO2 on the oil phase is obtained by equation (1) and equation (2): e,P1 ) and expansion volume (V s,P1 ):

[0029] V e,P1 =V0-V' P1 (1)

[0030] V s,P1 =V P1 -V' P1 (2)

[0031] Where V e,P1 V is the extraction volume of the oil phase by CO2 at P1 pressure, ml; s,P1 is the expansion volume of the oil phase by CO2 under P1 pressure, ml; V0 is the volume of the oil phase added to the transparent graduated tube under normal pressure, ml; V P1 is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; V' P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visual container changes from P1 to normal pressure, ml;

[0032] The expansion rate α and extraction rate β of unit mass CO2 under the pressure condition of P1 are obtained by equations (3) and (4):

[0033]

[0034]

[0035] Where α is the expansion rate of unit mass CO2 at P1 pressure, g -1 ; β is the extraction rate of unit mass CO2 at P1 pressure, g -1 ; V0 is the volume of the oil phase added to the transparent graduated tube at normal pressure, ml; V P1 is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; V' P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visible container changes from P1 to normal pressure, ml; m g is the mass of CO2 introduced into the visible container, the first chamber and the corresponding pipelines from the CO2 high-pressure container, g.

[0036] In a possible design, in the step S1, a small amount of dye is added to the oil phase, and the mass ratio of the oil phase to the dye is 200:1 to 400:1.

[0037] In a possible design, in step S5, the value of P1 is greater than the bubble point pressure of CO2 at the temperature.

[0038] In a possible design, in step S5, pushing the piston of the intermediate container toward one end close to the five-way valve includes the high-pressure pump pushing the piston of the intermediate container toward one end close to the five-way valve in a constant speed mode.

[0039] In one possible design, in step S5, when the pressure sensor reaches the set pressure P1, the volume V of the oil phase is recorded. P1 When the pressure sensor shows that the set pressure P1 is reached, the high-pressure pump is changed to a constant pressure mode, and the change value of the pumping volume of the high-pressure pump along with the pressure is recorded. When the pumping volume remains substantially unchanged within 2 hours, it is considered that the pressure in the visual container is balanced, and the volume V of the oil phase in the transparent graduated tube at this time is recorded. P1 .

[0040] In one possible design, the volume of the oil phase in S1 and the set pressure in S5 are changed, and by repeating steps S1-S7, the expansion rate α and extraction rate β of unit mass CO2 to crude oil at different mass ratios of oil phase and CO2 and different pressures can be obtained.

[0041] In a third aspect, the present invention also discloses a method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 and its application in improving crude oil recovery.

[0042] The beneficial effects of the technical solution provided by the present invention include at least:

[0043] The device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 provided in the embodiment of the present invention has a simple structure and is easy to build. Through the ingenious design of the experimental device and the simple experimental process, the expansion rate and extraction rate of CO2 on crude oil can be obtained while considering the expansion and extraction effects at the same time. The result is more accurate than that obtained by a single expansion experiment or extraction experiment, and is more instructive for the CO2 displacement or throughput process.

[0044] The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 provided in the embodiment of the present invention can obtain the expansion rate and extraction rate per unit mass of CO2. The evaluation result is more comparative and can more clearly compare and analyze the expansion effect and extraction effect at different pressures, which has a targeted guiding role in the pressure control of using CO2 to improve the recovery rate during oil field development.

[0045] The method of quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 of the present invention can control and change various factors such as temperature, pressure, mass ratio of CO2 and oil, and can provide more comprehensive guidance for the design parameters of CO2 development on site in oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the structure of a device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 provided in an embodiment of the present invention;

[0047] Figure 2 is a top view of a plug provided by an embodiment of the present invention;

[0048] Among them, 1. visual container, 2. transparent graduated tube, 3. electromagnetic stirrer, 4. magnet, 501. first valve, 502. second valve, 503. third valve, 504. fourth valve, 505. fifth valve, 506. sixth valve, 6. intermediate container, 7. CO2 high pressure container, 8. piston, 9. high pressure pump, 10. balance, 11. pressure sensor, 12. constant temperature box, 13. five-way valve, 14. three-way valve, 15. stopper, 16. vent, 17. first chamber, 18. second chamber, 101. first pipeline, 102. second pipeline, 103. third pipeline, 104. fourth pipeline, 105. fifth pipeline, 106. sixth pipeline, 107. seventh pipeline, 108. eighth pipeline. DETAILED DESCRIPTION

[0049] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0050] CO2 has good solubility and strong extraction ability in crude oil, which can significantly reduce the viscosity of crude oil, expand and increase the volume, and reduce the interfacial tension through multiple phase contacts with crude oil, thereby significantly improving the recovery rate of oil reservoirs. Therefore, giving full play to the expansion and extraction effect of CO2 on crude oil will become an important method for subsequent production increase.

[0051] However, in the actual process, expansion and extraction occur simultaneously in the phase equilibrium process between CO2 and crude oil. The two occur simultaneously and affect each other. The study of expansion and extraction alone cannot truly reflect the real interaction between CO2 and crude oil. The phase state between CO2 and crude oil can be calculated through numerical simulation, but the selection of interaction parameters between crude oil and CO2 is very critical and often needs to be obtained through experiments. Therefore, it is very important and necessary to establish an experimental method to evaluate and measure the expansion rate and extraction rate of crude oil under the action of CO2.

[0052] In the first aspect, the embodiment of the present invention discloses a device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2, comprising a visual container 1, a transparent graduated tube 2, a stirring device, a first valve 501, a second valve 502, a third valve 503, a fourth valve 504, a fifth valve 505, a sixth valve 506, an intermediate container 6, a CO2 high-pressure container 7, a piston 8, a high-pressure pump 9, a balance 10, a pressure sensor 11, a constant temperature control system 12, a five-way valve 13, a three-way valve 14, a first pipeline 101, a second pipeline 102, a third pipeline 103, a fourth pipeline 104, a fifth pipeline 105, a sixth pipeline 106, a seventh pipeline 107 and an eighth pipeline 108;

[0053] A transparent graduated tube 2 is arranged in the visual container 1, the upper end of the transparent graduated tube 2 is open, and a stirring device is arranged in the transparent graduated tube 2;

[0054] The visual container 1 is connected to the five-way valve 13 through a first pipeline 101, and a first valve 501 is provided on the first pipeline 101;

[0055] The five-way valve 13 is connected to the CO2 high-pressure container 7 through the second pipeline 102, and the second pipeline 102 is provided with a second valve 502;

[0056] The balance 10 is arranged below the CO2 high pressure container 7;

[0057] The intermediate container 6 is provided with a piston 8, which divides the intermediate container into a first chamber 17 and a second chamber 18 which are not connected; the five-way valve 13 is connected to the first chamber 17 of the intermediate container 6 through a third pipeline 103, and a third valve 503 is provided on the third pipeline 103;

[0058] The five-way valve 13 is connected to the atmosphere through a fourth pipeline 104, and a fourth valve 504 is provided on the fourth pipeline 104;

[0059] The five-way valve 13 is connected to the pressure sensor 11 through the fifth pipeline 105;

[0060] The second chamber 18 of the intermediate container 6 is connected to the three-way valve 14 through the sixth pipeline 106;

[0061] The three-way valve 14 is connected to the high-pressure pump 9 through the seventh pipeline 107, and the seventh pipeline 107 is provided with a fifth valve 505;

[0062] The three-way valve 14 is connected to the atmosphere through the eighth pipeline 108 , and a sixth valve 506 is provided on the eighth pipeline 108 .

[0063] The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 provided in the embodiment of the present invention has a simple structure and is easy to build. By pressurizing and dissolving CO2 once and releasing the pressure, the expansion rate and extraction rate can be calculated while considering the oil expansion and CO2 extraction effects at the same time. This can provide guidance for designing a reasonable pressure during the development of CO2 throughput or displacement in oil fields, so as to better exert the expansion and extraction effects and achieve the purpose of improving the recovery rate.

[0064] In one possible design, the visual container 1, the transparent graduated tube 2, the stirring device, the first valve 501, the second valve 502, the third valve 503, the fourth valve 504, the fifth valve 505, the sixth valve 506, the intermediate container 6, the CO2 high-pressure container 7, the piston 8, the high-pressure pump 9, the balance 10, the pressure sensor 11, the five-way valve 13, the three-way valve 14, the first pipeline 101, the second pipeline 102, the third pipeline 103, the fourth pipeline 104, the fifth pipeline 105, the sixth pipeline 106, the seventh pipeline 107 and the eighth pipeline 108 are all arranged in the constant temperature control system 12.

[0065] Optionally, the constant temperature control system 12 includes a constant temperature box.

[0066] In a possible design, a stopper 15 is provided at the opening of the transparent graduated tube 2 , and a vent hole 16 is provided on the stopper 15 .

[0067] Optionally, a plurality of vent holes 16 may be provided.

[0068] Optionally, the stirring device includes an electromagnetic stirrer 3 and a magnet 4 , the electromagnetic stirrer 3 is arranged below the visible container 1 , and the magnet 4 is arranged in the transparent graduated tube 2 .

[0069] In a second aspect, an embodiment of the present invention further discloses a method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2, comprising the following steps:

[0070] S1. Under normal pressure, put the oil phase with a set volume V0 and the magnet 4 into the transparent graduated tube 2, and the mass of the oil phase is recorded as m1;

[0071] S2, add the transparent graduated tube 2 into the visual container 1, ensure that the liquid level is visible, connect the pipelines, close all valves, turn on the constant temperature control system 12, set the temperature, and turn on the electromagnetic stirrer 3;

[0072] S3, opening the first valve 501, the second valve 502, the third valve 503, and the sixth valve 506, and passing the CO2 in the CO2 high-pressure container 7 into the first chamber 17 of the visual container 1 and the intermediate container 6, so that the piston in the intermediate container 6 is pushed to the end close to the three-way valve 14;

[0073] S4. The mass of CO2 entering the visual container 1, the first chamber 17 and the corresponding pipeline is recorded by the balance 10 as m g ;

[0074] S5. Close all valves, open the first valve 501, the third valve 503 and the fifth valve 505, start the high-pressure pump 9, push the piston 8 of the intermediate container 6 toward the end close to the five-way valve 13, dissolve CO2 in the oil phase, and when the pressure sensor 11 reaches the set pressure P1, record the liquid level of the oil phase in the transparent graduated tube 2 at this time and calculate the volume V of the oil phase at this time P1 ;

[0075] S6. Close all valves, open the first valve 501 and the fourth valve 504, and quickly discharge the CO2 in the visual container 1. When the pressure in the visual container 1 becomes normal pressure, record the liquid level of the oil phase in the transparent graduated tube 2 at this time and calculate the volume V' of the oil phase at this time. P1 ;

[0076] S7, calculate the mass ratio of CO2 to oil phase under the condition of pressure P1, m g : The expansion rate α and extraction rate β of unit mass CO2 in the system composed of m1;

[0077] The extraction volume (V) of CO2 on the oil phase is obtained by equation (1) and equation (2): e,P1 ) and expansion volume (V s,P1 ):

[0078] V e,P1 =V0-V' P1 (1)

[0079] V s,P1 =V P1 -V' P1 (2)

[0080] Where V e,P1 V is the extraction volume of the oil phase by CO2 at P1 pressure, ml; s,P1 is the expansion volume of the oil phase by CO2 under P1 pressure, ml; V0 is the volume of the oil phase added to the transparent graduated tube under normal pressure, ml; V P1 is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; V' P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visual container changes from P1 to normal pressure, ml;

[0081] The expansion rate α and extraction rate β of unit mass CO2 under the pressure condition of P1 are obtained by equations (3) and (4):

[0082]

[0083]

[0084] Where α is the expansion rate of unit mass CO2 at P1 pressure, g -1 ; β is the extraction rate of unit mass CO2 at P1 pressure, g -1 ; V0 is the volume of the oil phase added to the transparent graduated tube at normal pressure, ml; V P1 is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; V' P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visible container changes from P1 to normal pressure, ml; m g is the mass of CO2 introduced into the visible container, the first chamber and the corresponding pipelines from the CO2 high-pressure container, g.

[0085] It should be noted that under the pressure of P1, CO2 is in liquid state. On the one hand, part of the CO2 in the first chamber 17 of the visual container 1 and the intermediate container 6 dissolves into the oil phase in the transparent graduated tube 2, causing the oil phase to expand and increase in volume. On the other hand, part of the oil in the transparent graduated tube 2 diffuses and is extracted into the CO2, causing the volume of the oil phase to decrease. Under the combined effect of the two aspects, when the pressure in the visual container 1 reaches P1 and maintains pressure balance, the oil phase also reaches a balance between expansion and extraction. At this time, the volume of the oil phase in the transparent graduated tube 2 is the volume of the remaining oil phase after the CO2 dissolves and expands, excluding the extracted part.

[0086] When the pressure in the visual container 1 becomes normal pressure, CO2 becomes gaseous and is released from the oil phase. At this time, the oil phase extracted into the CO2 phase will fall back into the visual container 1, the first chamber 17 and the pipeline. Considering that the volume of the transparent graduated tube 2 is much smaller than that of the visual container 1, and a plug with a vent hole is provided above the transparent graduated tube 2, as shown in FIG. Figure 2 As shown, the volume of the oil phase falling back into the transparent graduated tube 2 is negligible. Therefore, it can be considered that the oil phase in the transparent graduated tube 2 at this time is the oil phase that is not extracted under the pressure of P1, that is, the oil phase that only expands under the pressure of P1, and the volume of the oil phase at this time is the volume of the oil phase that expands under the pressure of P1.

[0087] In a possible design, in step S1, a small amount of dye is added to the oil phase, and the mass ratio of the oil phase to the dye is 200:1 to 400:1.

[0088] Optionally, in step S1, the staining agent includes but is not limited to Sudan red.

[0089] It should be noted that Sudan red is added to the oil phase as a dye to facilitate observation of the liquid level value of the oil phase through the transparent graduated tube 2 .

[0090] In one possible design, in step S5, the value of P1 is greater than the bubble point pressure of CO2 at the temperature to ensure that CO2 is in a supercritical or liquid state.

[0091] It should be noted that when CO2 is in a supercritical or liquid state, the expansion and extraction effects of CO2 on oil are more obvious; when the pressure is lower, CO2 is in a gaseous state, the distance between CO2 gas molecules is large, the compressibility is strong, and the solubility in oil and the ability to extract oil molecules are weak.

[0092] In a possible design, in step S5, pushing the piston 8 of the intermediate container 6 toward one end close to the five-way valve 13 includes the high-pressure pump 9 pushing the piston 8 of the intermediate container 6 toward one end close to the five-way valve 13 at a constant speed.

[0093] It can be understood that by pushing the piston 8 of the intermediate container 6 toward one end close to the five-way valve 13, the volume of CO2 in the first chamber 17 and the visible container 1 can be compressed, so that the pressure increases, and the pressure is increased to a set value, so that the expansion and extraction effect of CO2 on oil under a certain pressure can be obtained, which is more conducive to guiding the selection of pressure during field development.

[0094] In one possible design, in step S5, when the pressure sensor 11 reaches the set pressure P1, the volume V of the oil phase is recorded. P1 Including, when the pressure sensor 11 shows that the set pressure P1 is reached, the high-pressure pump 9 is changed to the constant pressure mode, and the change value of the pumping amount of the high-pressure pump 9 with the pressure is recorded. When the pumping amount remains basically unchanged within 2 hours, it is considered that the pressure in the visual container 1 has reached a balance, and the volume V of the oil phase in the transparent graduated tube 2 at this time is recorded. P1 .

[0095] It can be understood that when the pressure balance is reached in the visible container 1, it means that the dissolution of CO2 into the oil phase and the diffusion of the oil phase into the CO2 phase have reached a balance, that is, the expansion effect and extraction effect of CO2 on the oil phase have reached a balance. At this time, the volume of the oil phase is the volume of the remaining oil phase after the oil phase extracted into the CO2 phase is removed and the CO2 is expanded.

[0096] In a possible design, the volume of the oil phase in S1 and the set pressure in S5 are changed, and by repeating steps S1-S7, the expansion rate α and extraction rate β of unit mass CO2 to crude oil at different mass ratios of oil phase and CO2 and different pressures can be obtained.

[0097] It is understandable that during the development process, it is necessary to design the injection volume and injection pressure of CO2. By obtaining the expansion and extraction rates under different mass ratios and pressures, a more reasonable injection volume and injection pressure can be designed during the development process to ensure that the expansion and extraction effect of CO2 on crude oil reaches a better degree, which is conducive to improving the recovery rate.

[0098] Optionally, the temperature setting range of the constant control system 12 is 20-100°C.

[0099] In a third aspect, the present invention also discloses a method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 and its application in improving crude oil recovery.

[0100] Expansion and extraction are important mechanisms for CO2 to enhance crude oil recovery. The quantitative evaluation method of the present invention can screen out the pressure values ​​at which CO2 has a high extraction rate and expansion rate for crude oil and the mass ratio of oil to CO2. That is, under this condition, CO2 interacts with crude oil and can give full play to the expansion and extraction effects, so that more crude oil can be produced. The basic data of expansion rate and extraction rate under different compositions and pressures can be used to guide the injection amount and injection pressure of CO2 during the development process, as well as the selection of parameters such as the pressure reduction amplitude and pressure reduction rate during the subsequent pressure reduction development process.

[0101] All the above optional technical solutions can be arbitrarily combined to form optional embodiments disclosed in the present invention, and will not be described one by one here.

[0102] The present invention will be further described below through specific examples.

[0103] Unless otherwise specified, the experimental methods used in the following specific examples are all conventional methods.

[0104] In the following specific examples, the operations involved in the operation without specifying the conditions were all carried out under conventional conditions or the conditions recommended by the manufacturer. The raw materials used without specifying the manufacturer and specifications were all conventional products that can be obtained through commercial purchase.

[0105] In the following specific examples: the oil phase is n-hexadecane, chemically pure, from Sinopharm Chemical Reagent Co., Ltd.; the dye is Sudan III, BS (Shanghai test), from Sinopharm Chemical Reagent Co., Ltd.; CO2 gas, 99.9%, from Qingdao Tianyuan Gas Manufacturing Co., Ltd.

[0106] This embodiment adopts Figure 1 The device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 comprises a visual container 1, a transparent graduated tube 2, an electromagnetic stirrer 3, a magnet 4, a first valve 501, a second valve 502, a third valve 503, a fourth valve 504, a fifth valve 505, a sixth valve 506, an intermediate container 6, a CO2 high-pressure container 7, a piston 8, a high-pressure pump 9, a balance 10, a pressure sensor 11, a constant temperature control system 12, a five-way valve 13, a three-way valve 14, a first pipeline 101, a second pipeline 102, a third pipeline 103, a fourth pipeline 104, a fifth pipeline 105, a sixth pipeline 106, a seventh pipeline 107 and an eighth pipeline 108;

[0107] A transparent graduated tube 2 is arranged in the visual container 1, the upper end of the transparent graduated tube 2 is open, a plug 15 is arranged at the opening of the transparent graduated tube 2, and a vent hole 16 is arranged on the plug 15, and a plurality of vent holes 16 can be arranged;

[0108] The electromagnetic stirrer 3 is arranged below the visible container 1, and the magnet 4 is arranged in the transparent graduated tube 2;

[0109] The visual container 1 is connected to the five-way valve 13 through a first pipeline 101, and a first valve 501 is provided on the first pipeline 101;

[0110] The five-way valve 13 is connected to the CO2 high-pressure container 7 through the second pipeline 102, and the second pipeline 102 is provided with a second valve 502;

[0111] The balance 10 is arranged below the CO2 high pressure container 7;

[0112] The intermediate container 6 is provided with a piston 8, which divides the intermediate container into a first chamber 17 and a second chamber 18 which are not connected; the five-way valve 13 is connected to the first chamber 17 of the intermediate container 6 through a third pipeline 103, and a third valve 503 is provided on the third pipeline 103;

[0113] The five-way valve 13 is connected to the atmosphere through a fourth pipeline 104, and a fourth valve 504 is provided on the fourth pipeline 104;

[0114] The five-way valve 13 is connected to the pressure sensor 11 through the fifth pipeline 105;

[0115] The second chamber 18 of the intermediate container 6 is connected to the three-way valve 14 through the sixth pipeline 106;

[0116] The three-way valve 14 is connected to the high-pressure pump 9 through the seventh pipeline 107, and the seventh pipeline 107 is provided with a fifth valve 505;

[0117] The three-way valve 14 is connected to the atmosphere through the eighth pipeline 108, and the eighth pipeline 108 is provided with a sixth valve 506;

[0118] A visual container 1, a transparent graduated tube 2, an electromagnetic stirrer 3, a stirring magnet 4, a first valve 501, a second valve 502, a third valve 503, a fourth valve 504, a fifth valve 505, a sixth valve 506, an intermediate container 6, a CO2 high-pressure container 7, a piston 8, a high-pressure pump 9, a balance 10, a pressure sensor 11, a five-way valve 13, a three-way valve 14, a first pipeline 101, a second pipeline 102, a third pipeline 103, a fourth pipeline 104, a fifth pipeline 105, a sixth pipeline 106, a seventh pipeline 107 and an eighth pipeline 108 are all arranged in a constant temperature box.

[0119] A method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 comprises the following steps:

[0120] S1, under normal pressure, a set volume V0 of hexadecane and a set mass of Sudan red are mixed to form a first mixed solution, the mass ratio of hexadecane to Sudan red is 200:1 to 400:1, the first mixed solution and the magnet 4 are placed in a transparent graduated tube 2, and the mass of the first mixed solution is recorded as m1;

[0121] S2, put the transparent graduated tube 2 into the visual container 1, ensure that the liquid level is visible, connect the pipelines, close all valves, open the thermostat, set the temperature to 50°C, and turn on the electromagnetic stirrer 3;

[0122] S3, opening the first valve 501, the second valve 502, the third valve 503, and the sixth valve 506, and passing the CO2 in the CO2 high-pressure container 7 into the first cavity 17 of the visual container 1 and the intermediate container 6, so that the piston in the intermediate container 6 is pushed to the end close to the three-way valve 14;

[0123] S4. Record the mass of CO2 entering the visual container 1, the first cavity 17 and the corresponding pipelines by a balance as m g ;

[0124] S5, close all valves, open the first valve 501, the third valve 503, and the fifth valve 505, start the high-pressure pump 9, and the high-pressure pump 9 pushes the piston of the intermediate container 6 toward the end close to the five-way valve 13 in a constant speed mode to dissolve CO2 in the first mixed solution. When the pressure sensor 11 shows that the set pressure P1 is reached, the high-pressure pump 9 is changed to a constant pressure mode, and the change value of the pump flow of the high-pressure pump 9 with the pressure is recorded. When the pump flow remains basically unchanged within 2 hours, it is considered that the pressure in the visual container 1 has reached pressure equilibrium, and the liquid level of the first mixed solution in the transparent graduated tube 2 at this time is recorded and the volume V of the first mixed solution at this time is calculated P1 ;

[0125] S6. Close all valves, open the first valve 501 and the fourth valve 504, and quickly discharge the CO2 in the visual container 1. When the pressure in the visual container 1 becomes normal pressure, record the liquid level of the first mixed solution in the transparent graduated tube 2 at this time and calculate the volume V' of the first mixed solution at this time. P1 ;

[0126] S7, calculate the mass ratio of CO2 to oil phase under the condition of pressure P1, m g : The expansion rate α and extraction rate β of unit mass CO2 in the system composed of m1;

[0127] The extraction volume (V) of CO2 on the oil phase is obtained by equation (1) and equation (2): e,P1 ) and expansion volume (Vs,P1 ):

[0128] V e,P1 =V0-V' P1 (1)

[0129] V s,P1 =V P1 -V' P1 (2)

[0130] Where V e,P1 V is the extraction volume of the oil phase by CO2 at P1 pressure, ml; s,P1 is the expansion volume of the oil phase by CO2 under P1 pressure, ml; V0 is the volume of the oil phase added to the transparent graduated tube under normal pressure, ml; V P1 is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; V' P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visual container changes from P1 to normal pressure, ml;

[0131] The expansion rate α and extraction rate β of unit mass CO2 under the pressure condition of P1 are obtained by equations (3) and (4):

[0132]

[0133]

[0134] Where α is the expansion rate of unit mass CO2 at P1 pressure, g -1 ; β is the extraction rate of unit mass CO2 at P1 pressure, g -1 ; V0 is the volume of the oil phase added to the transparent graduated tube at normal pressure, ml; V P1 is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; V' P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visible container changes from P1 to normal pressure, ml; m g is the mass of CO2 introduced into the visible container, the first chamber and the corresponding pipelines from the CO2 high-pressure container, g.

[0135] S8. Changing the volume of hexadecane and the mass of Sudan red in S1 and the set pressure in S5, by repeating steps S1-S7, the expansion rate α and extraction rate β of unit mass of CO2 on crude oil can be obtained at different mass ratios of oil and CO2 and different pressures.

[0136] The expansion ratio α and extraction ratio β of unit mass CO2 on crude oil under different pressures measured by the above-mentioned device and method are shown in Table 1.

[0137] Table 1 Expansion rate α and extraction rate β of unit mass CO2 on crude oil under different pressures

[0138]

[0139] The device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 provided in the embodiment of the present invention has a simple structure and is easy to build. Through the ingenious design of the experimental device and the simple experimental process, the expansion rate and extraction rate of CO2 on crude oil can be obtained while considering the expansion and extraction effects at the same time. The result is more accurate than that obtained by a single expansion experiment or extraction experiment, and is more instructive for the CO2 displacement or throughput process.

[0140] The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 provided in the embodiment of the present invention can obtain the expansion rate and extraction rate per unit mass of CO2. The evaluation result is more comparative and can more clearly compare and analyze the expansion effect and extraction effect at different pressures, which has a targeted guiding role in the pressure control of using CO2 to improve the recovery rate during oil field development.

[0141] The method of quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 of the present invention can control and change various factors such as temperature, pressure, mass ratio of CO2 and oil, and can provide more comprehensive guidance for the design parameters of CO2 development on site in oil fields.

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2, characterized in that: The invention comprises a visual container (1), a transparent graduated tube (2), a stirring device, a first valve (501), a second valve (502), a third valve (503), a fourth valve (504), a fifth valve (505), a sixth valve (506), an intermediate container (6), a CO2 high-pressure container (7), a piston (8), a high-pressure pump (9), a balance (10), a pressure sensor (11), a constant temperature control system (12), a five-way valve (13), a three-way valve (14), a first pipeline (101), a second pipeline (102), a third pipeline (103), a fourth pipeline (104), a fifth pipeline (105), a sixth pipeline (106), a seventh pipeline (107) and an eighth pipeline (108); A transparent graduated tube (2) is arranged in the visible container (1), the upper end of the transparent graduated tube (2) is open, and a stirring device is arranged in the transparent graduated tube (2); The visible container (1) is connected to the five-way valve (13) via the first pipeline (101), and the first pipeline (101) is provided with the first valve (501); The five-way valve (13) is connected to the CO2 high-pressure container (7) via the second pipeline (102), and the second pipeline (102) is provided with the second valve (502); The balance (10) is arranged below the CO2 high pressure container (7); The intermediate container (6) is provided with a piston (8), and the piston (8) divides the intermediate container into a first chamber (17) and a second chamber (18) which are not connected; the five-way valve (13) is connected to the first chamber (17) of the intermediate container (6) through the third pipeline (103), and the third valve (503) is provided on the third pipeline (103); The five-way valve (13) is connected to the atmosphere through the fourth pipeline (104), and the fourth pipeline (104) is provided with the fourth valve (504); The five-way valve (13) is connected to the pressure sensor (11) via the fifth pipeline (105); The second chamber (18) of the intermediate container (6) is connected to the three-way valve (14) via the sixth pipeline (106); The three-way valve (14) is connected to the high-pressure pump (9) via the seventh pipeline (107), and a fifth valve (505) is provided on the seventh pipeline (107); The three-way valve (14) is connected to the atmosphere through the eighth pipeline (108), and a sixth valve (506) is provided on the eighth pipeline (108).

2. The device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 1, characterized in that: The visual container (1), the transparent graduated tube (2), the stirring device, the first valve (501), the second valve (502), the third valve (503), the fourth valve (504), the fifth valve (505), the sixth valve (506), the intermediate container (6), the CO2 high-pressure container (7), the piston (8), the high-pressure pump (9), the balance (10), the pressure sensor (11), the five-way valve (13), the three-way valve (14), the first pipeline (101), the second pipeline (102), the third pipeline (103), the fourth pipeline (104), the fifth pipeline (105), the sixth pipeline (106), the seventh pipeline (107) and the eighth pipeline (108) are all arranged in the constant temperature control system (12).

3. The device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 1, characterized in that: A plug (15) is provided at the opening of the transparent graduated tube (2), and a vent hole (16) is provided on the plug (15).

4. A method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2, using the device for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 2, characterized in that: The steps include: S1, under normal pressure, add a set volume V0 of oil phase into the transparent graduated tube (2), and the mass of the oil phase is recorded as m1; S2, placing the transparent graduated tube (2) into the visual container (1), ensuring that the liquid level is visible, connecting the pipelines, closing all valves, turning on the constant temperature control system (12), setting the temperature, and turning on the stirring device; S3, opening the first valve (501), the second valve (502), the third valve (503), and the sixth valve (506), and passing the CO2 in the CO2 high-pressure container (7) into the first chamber (17) of the visible container (1) and the intermediate container (6), so that the piston in the intermediate container (6) is pushed to one end close to the three-way valve (14); S4. Record the mass of CO2 in the visible container (1), the first chamber (17) and the corresponding pipelines from the CO2 high pressure container (7) by a balance (10). g ; S5, close all valves, open the first valve (501), the third valve (503) and the fifth valve (505), start the high-pressure pump (9), push the piston of the intermediate container (6) toward the end close to the five-way valve (13), dissolve CO2 in the oil phase, and when the pressure sensor (11) reaches the set pressure P1, record the liquid level of the oil phase in the transparent graduated tube (2) at this time and calculate the volume V of the oil phase at this time P1 ; S6. Close all valves, open the first valve (501) and the fourth valve (504), and quickly discharge the CO2 in the visual container (1). When the pressure in the visual container (1) becomes normal pressure, record the liquid level of the oil phase in the transparent graduated tube (2) at this time and calculate the volume V′ of the oil phase at this time. P1 ; S7, calculate the mass ratio of CO2 to oil phase under the condition of pressure P1, m g : The expansion rate α and extraction rate β of unit mass CO2 in the system composed of m1; The extraction volume (V) of CO2 on the oil phase is obtained by equation (1) and equation (2): e,P1 ) and expansion volume (V s,P1 ): V e,P1 =V0-V′ P1 (1) V s,P1 =V P1 -V′ P1 (2) Where V e,P1 V is the extraction volume of the oil phase by CO2 at P1 pressure, ml; s,P1 is the expansion volume of the oil phase by CO2 under P1 pressure, ml; V0 is the volume of the oil phase added to the transparent graduated tube under normal pressure, ml; V P1 V' is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visual container changes from P1 to normal pressure, ml; The expansion rate α and extraction rate β of unit mass CO2 under the pressure condition of P1 are obtained by equations (3) and (4): Where α is the expansion rate of unit mass CO2 at P1 pressure, g -1 ; β is the extraction rate of unit mass CO2 at P1 pressure, g -1 ; V0 is the volume of the oil phase added to the transparent graduated tube at normal pressure, ml; V P1 V' is the volume of the oil phase in the transparent graduated tube at P1 pressure, ml; P1 is the volume of the oil phase in the transparent graduated tube after the pressure in the visible container changes from P1 to normal pressure, ml; m g is the mass of CO2 introduced into the visible container, the first chamber and the corresponding pipelines from the CO2 high-pressure container, g.

5. The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 4, characterized in that: In the step S1, a small amount of dye is added to the oil phase, and the mass ratio of the oil phase to the dye is 200:1 to 400:

1.

6. The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 4, characterized in that: In step S5, the value of P1 is greater than the bubble point pressure of CO2 at the temperature.

7. The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 4, characterized in that: In the step S5, pushing the piston of the intermediate container (6) toward one end close to the five-way valve (13) includes the high-pressure pump (9) pushing the piston of the intermediate container (6) toward one end close to the five-way valve (13) in a constant speed mode.

8. The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 4, characterized in that: In step S5, when the pressure sensor (11) reaches the set pressure P1, the volume V of the oil phase is recorded. P1 The method comprises: when the pressure sensor (11) indicates that the set pressure P1 has been reached, changing the high-pressure pump (9) to a constant pressure mode, recording the change in the pumping volume of the high-pressure pump (9) along with the pressure, and when the pumping volume remains substantially unchanged within 2 hours, it is considered that the pressure in the visual container (1) has reached a balance, and recording the volume V of the oil phase in the transparent graduated tube (2) at this time. P1 .

9. The method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as claimed in claim 4, characterized in that: By changing the volume of the oil phase in S1 and the set pressure in S5 and repeating steps S1-S7, the expansion rate α and extraction rate β of unit mass CO2 to crude oil at different mass ratios of oil phase and CO2 and different pressures can be obtained.

10. Application of the method for quantitatively evaluating the expansion rate and extraction rate of crude oil under the action of CO2 as described in any one of claims 4 to 9 in improving crude oil recovery.

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