CN117005853B - Mixed-phase pressure measurement device and method - Google Patents

Abstract

The invention provides a mixed phase pressure measuring device and a method, wherein the device comprises a container assembly, a pressure assembly, a conveying assembly and an acoustic wave measuring assembly; the core powder is placed in the container assembly, and the conveying assembly is configured to inject crude oil and liquid carbon dioxide into the cavity; the pressure assembly is configured to provide a driving pressure to the delivery assembly; the acoustic wave measurement assembly is configured to measure an acoustic signal within the cavity; the method comprises the steps of pressurizing and injecting crude oil into a cavity in which core powder is placed, injecting liquid carbon dioxide into the cavity after the crude oil is injected, and measuring a first acoustic signal; increasing the pressure of the liquid carbon dioxide in the cavity and measuring a second acoustic signal; and calculating the cross-correlation coefficient of the second acoustic signal and the first acoustic signal, wherein the corresponding pressure is the minimum miscible pressure when the inflection point appears on the cross-correlation coefficient curve. The invention provides a miscible pressure measuring device and a miscible pressure measuring method, which can fully consider the influence of pore size, core mineral components and wettability on a minimum miscible pressure value.

Description

Mixed-phase pressure measurement device and method

Technical Field

The invention belongs to the technical field of oil and gas field development, and particularly relates to a mixed phase pressure measurement device and method.

Background

The carbon dioxide displacement or huff and puff technology can effectively improve the comprehensive recovery ratio of oil reservoirs such as compact oil, shale oil and the like, and has better recovery effect under the condition that carbon dioxide and crude oil are miscible phase compared with the condition that the carbon dioxide and the crude oil are not miscible phase in the carbon dioxide displacement or huff and puff process. At present, the key parameter for judging whether crude oil and carbon dioxide can be mixed is minimum mixed phase pressure (Minimum Miscible Pressure, MMP), and is influenced by a plurality of factors such as crude oil components, temperature, pore size, mineral components and the like.

Currently, MMPs are mainly obtained by the following techniques: (1) phase theory and empirical formula theory calculation method. Theoretical calculations or empirical formulas rely on the precondition hypothesis conditions of the theoretical model and empirical data to predict MMP. (2) The experimental test method is specifically divided into a tubule method and an interfacial tension vanishing method. The tubule method judges the corresponding MMP according to the oil-gas phase state in the observation window at the rear end of the tubule and the oil-gas phase difference in different temperatures and pressures by displacing the oil phase in the sand-filled bent tubule with the length of 10m to 30m, and is a method for testing the minimum miscible phase pressure with high international acceptance.

However, none of the above methods embody the effects of specific reservoir rock composition, pore size and wettability on MMP.

Disclosure of Invention

Aiming at the defects of the existing crude oil and carbon dioxide miscible device, the invention provides a miscible pressure measuring device and a miscible pressure measuring method, which can fully consider the influences of pore size, core mineral components and wettability on MMP.

In a first aspect, the present invention provides a miscible pressure measurement apparatus comprising a container assembly, an acoustic measurement assembly, a pressure assembly, and a delivery assembly; the container assembly comprises an openable and closable container, the container is provided with a closed cavity, the cavity is provided with a liquid injection port and an oil injection port, and the cavity is configured to contain core powder; the conveying assembly comprises a crude oil injection unit and a carbon dioxide injection unit, the crude oil injection unit is communicated with the oil injection port and used for injecting crude oil into the cavity, and the carbon dioxide injection unit is communicated with the liquid injection port and used for injecting liquid carbon dioxide into the cavity; the pressure assembly is configured to provide driving pressures for the crude oil injection unit and the carbon dioxide injection unit and comprises a plunger pump and a processor, wherein the plunger pump is controlled by the processor and used for feeding back pressure points in real time; the acoustic wave measurement assembly comprises a plurality of ultrasonic array transducers, the ultrasonic array transducers are arranged in the container and are configured to measure acoustic signals in the cavity, the ultrasonic array transducers are electrically connected with the processor, the processor is configured to determine minimum miscible pressure corresponding to the core powder according to the driving pressure and the acoustic signals, and the acoustic signals are generated after ultrasonic waves of the ultrasonic array transducers are transmitted through the core powder.

The above-mentioned miscible pressure measuring device, optionally, the container includes a container body and a cavity cover, the container body has an opening, the cavity cover is covered on the opening to enclose a cavity together with the container body, and the cavity cover is configured to be abutted to the outside of the core powder to compact the core powder.

According to the miscible pressure measuring device, optionally, the cavity cover is connected to the container body through a threaded fastener, and the fastening degree of the threaded fastener is adjustable, so that the cavity cover compresses the core powder.

The apparatus for measuring a mixed phase pressure as described above, optionally, the container assembly further comprises a bracket, and the container body is connected to the bracket and is rotatable about a horizontal axis relative to the bracket.

In the above miscible pressure measurement apparatus, optionally, a plurality of ultrasonic array transducers are disposed at intervals on a peripheral side of the cavity, and each ultrasonic array transducer is an ultrasonic array; at least one of the plurality of ultrasonic array transducers acts as an ultrasonic transmitter, and the remaining ultrasonic array transducers of the plurality of ultrasonic array transducers act as ultrasonic receivers.

As in the above-described miscible pressure measurement apparatus, optionally, the plunger pump is connected to the crude oil injection unit and the carbon dioxide injection unit, respectively, and is configured to inject the displacement medium into the crude oil injection unit and the carbon dioxide injection unit by driving pressure.

The above-mentioned mixed phase pressure measuring device, optionally, the conveying assembly further comprises an incubator, and the crude oil injection unit, the carbon dioxide injection unit and the container are all located in the incubator.

In a second aspect, the present invention provides a method for measuring a mixed phase pressure, specifically including:

according to the temperature condition of the mixed phase pressure test, referring to a phase diagram under the temperature condition corresponding to carbon dioxide, and liquefying the carbon dioxide;

Pressurizing and injecting crude oil into a closed cavity in which core powder is placed, injecting liquid carbon dioxide into the closed cavity in which the crude oil is injected, and detecting a first acoustic signal in the cavity after the liquid carbon dioxide is injected, wherein the core powder has a preset particle size, and the first acoustic signal is generated after ultrasonic waves of an ultrasonic array transducer in a pressure measuring device are transmitted by the core powder;

Increasing the pressure of liquid carbon dioxide in the cavity, measuring a second acoustic signal in the pressurized cavity, and generating the second acoustic signal after ultrasonic wave is transmitted by the core powder;

and determining the cross-correlation coefficient of the second acoustic signal and the first acoustic signal, drawing the cross-correlation coefficient into a curve, and determining the pressure of the corresponding liquid carbon dioxide as the minimum miscible pressure corresponding to the core powder when the inflection point of the cross-correlation coefficient curve appears.

The method for measuring the mixed phase pressure as described above, optionally, further comprises, before injecting the crude oil under pressure into the closed cavity in which the core powder is placed: and screening out core powder with preset particle size, and compacting the core powder in the closed cavity.

The method for measuring the mixed phase pressure as described above, optionally, further comprises, before injecting the crude oil under pressure into the closed cavity in which the core powder is placed: and wetting the core powder.

The invention provides a mixed phase pressure measuring device and a method, wherein the device comprises a container assembly, a pressure assembly, a conveying assembly and an acoustic wave measuring assembly; the core powder is placed in the container assembly, and the conveying assembly is configured to inject crude oil and liquid carbon dioxide into the cavity; the pressure assembly is configured to provide a driving pressure to the delivery assembly; the acoustic wave measurement assembly is configured to measure an acoustic signal within the cavity; the method comprises the steps of pressurizing and injecting crude oil into a cavity in which core powder is placed, injecting liquid carbon dioxide into the cavity after the crude oil is injected, and measuring a first acoustic signal; increasing the pressure of the liquid carbon dioxide in the cavity and measuring a second acoustic signal; and calculating the cross-correlation coefficient of the second acoustic signal and the first acoustic signal, wherein the corresponding pressure is the minimum miscible pressure when the inflection point appears on the cross-correlation coefficient curve. The invention provides a miscible pressure measuring device and a miscible pressure measuring method, which can fully consider the influence of pore size, core mineral components and wettability on a minimum miscible pressure value.

The invention has the beneficial technical effects that:

(1) The invention does not depend on visible light observation of the miscible phase, can detect the miscible phase through the reflection and refraction effects of ultrasonic waves, and the ultrasonic waves can propagate in a porous medium, so that the miscible phase process inside the pore of a real core can be effectively detected, and the influence of the pore size and the physical properties of the pore surface of the core on the miscible phase pressure can be fully reflected.

(2) According to the method, the mixed phase zone is monitored without depending on the amplitude information of the sound wave, the information carried by the amplitude of the ultrasonic signal is very limited, and the amplitude of the direct wave signal in the pore is less influenced by the mixed phase zone on a very small core scale. The invention adopts the acoustic wave form of the adjacent pressure points and the cross correlation coefficient of the frequency spectrum to judge the phase mixing belt, and has higher accuracy.

(3) The invention adopts the acoustic wave phased array transducer, can adjust the focal length and the azimuth of the acoustic wave, is matched with three ultrasonic array transducers for receiving ultrasonic signals, can improve the capturing efficiency of reflection and transmission waves of a phase interface, and improves the signal-to-noise ratio of the received signals.

In addition to the technical problems, features constituting the technical solutions, and advantageous effects caused by the technical features of the technical solutions described above, other technical problems that can be solved by the apparatus and method for measuring a mixed phase pressure, other technical features included in the technical solutions, and advantageous effects caused by the technical features of the technical solutions of the present invention will be described in further detail in the specific embodiments.

Drawings

FIG. 1 is a schematic diagram of an overall structure of a miscible pressure measurement device according to an embodiment of the present application;

FIG. 2 is a schematic view of a structure of a container assembly in a mixed phase pressure measuring device according to an embodiment of the present application;

Fig. 3 is a flowchart of a method for measuring a mixed phase pressure according to an embodiment of the present application.

Reference numerals:

1-a pressure measuring device;

10-a container assembly;

A 20-sonic measurement assembly;

21-an ultrasound array transducer;

22-an ultrasonic transmitting-receiving instrument;

30-a pressure assembly;

31-a plunger pump;

a 32-six way valve;

33-pressure vent;

34-a pressure relief valve;

A 35-processor;

40-a transport assembly;

41-a crude oil injection unit;

42-carbon dioxide injection unit;

43-a constant temperature box;

100-cavity;

101-a liquid injection port;

102-an oil filling port;

103-core powder;

110-a container;

111-a container body;

112-a cavity cover;

120-threaded fasteners;

130-a bracket;

140-rotating shaft;

150-a base;

160-cavity cover sealing rings;

311-plunger pump inlet valve;

312-plunger pump outlet valve;

411-crude injection unit inlet valve;

412-a crude injection unit outlet valve;

421-carbon dioxide injection unit inlet valve;

422-carbon dioxide injection unit outlet valve.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

The carbon dioxide displacement or huff and puff technology can effectively improve the comprehensive recovery ratio of oil reservoirs such as compact oil, shale oil and the like, and has better recovery effect under the condition that carbon dioxide and crude oil are miscible phase compared with the condition that the carbon dioxide and the crude oil are not miscible phase in the carbon dioxide displacement or huff and puff process. At present, the key parameter for judging whether crude oil and carbon dioxide can be mixed is minimum mixed phase pressure (Minimum Miscible Pressure, MMP), and is influenced by a plurality of factors such as crude oil components, temperature, pore size, mineral components and the like.

Currently, MMPs are mainly obtained by the following techniques: (1) phase theory and empirical formula theory calculation method. The empirical formula method needs to establish a set of unique formulas according to the characteristics of each oil field through unique actual conditions. The empirical formula method has the defect of unstable errors, and the application range is very narrow, generally only works for specific oil fields in specific areas, and is not completely reliable. (2) The experimental test method is specifically classified into a tubule method, an interfacial tension vanishing method, and the like. The tubule experiment is a one-dimensional thermodynamic model experiment, the tubule model is a very effective experimental model in simulating a one-dimensional flow displacement experiment, the porous medium structure of the model can simulate the displacement process of oil gas to a certain extent, and the tubule experiment can give repeated and relatively accurate results. However, the method is suspected to have the problems of large difference between the porous medium structure and the actual reservoir, unstable pore structure, inability of saturating stratum water, lack of unified experimental standards and the like, so that the experimental result is uncertain. The method utilizes a droplet shape analysis technology to accurately measure the interfacial tension between oil gas at each pressure point under the constant temperature condition, then draws the measured interfacial tension and pressure into a curve, and linearly extrapolates the curve to the minimum miscible pressure of zero to determine the minimum miscible pressure. However, it is severely affected by human factors, and the porous medium factor is not considered at all.

However, none of the above methods can embody the effects of specific reservoir rock composition, wettability, on MMP, and it is difficult to simulate the pore size of tight reservoirs.

Therefore, the application provides a miscible pressure measuring device and method, which comprises the steps of accommodating rock core powder by adopting a container assembly, compacting the rock core powder by adopting a cavity cover, capturing acoustic signals of liquid carbon dioxide and crude oil under different pressures by adopting an ultrasonic array transducer, and performing cross-correlation calculation on the acquired acoustic signals.

A miscible pressure measuring apparatus according to this embodiment will be further described below.

FIG. 1 is a schematic diagram of an overall structure of a miscible pressure measurement device according to an embodiment of the present application;

FIG. 2 is a schematic view of a structure of a container assembly in a mixed phase pressure measuring device according to an embodiment of the present application;

Fig. 3 is a flowchart of a method for measuring a mixed phase pressure according to an embodiment of the present application.

As shown in fig. 1, an embodiment of the present application provides a miscible pressure measuring apparatus. Specifically comprises a container assembly 10, an acoustic wave measuring assembly 20, a pressure assembly 30 and a conveying assembly 40; the container assembly 10 includes an openable and closable container 110, the container 110 having a closed cavity 100, the cavity 100 having a fill port 101 and a fill port 102, the cavity 100 being configured to hold a core powder 103; the conveying assembly 40 comprises a crude oil injection unit 41 and a carbon dioxide injection unit 42, wherein the crude oil injection unit 41 is communicated with an oil injection port 102 and used for injecting crude oil into the cavity 100, and the carbon dioxide injection unit 42 is communicated with a liquid injection port 101 and used for injecting liquid carbon dioxide into the cavity 100; the pressure assembly 30 is configured to provide driving pressures for the crude oil injection unit 41 and the carbon dioxide injection unit 42, and includes a plunger pump 31 and a processor 35, the plunger pump 31 being controlled by the processor 35 for feeding back pressure points in real time; the acoustic wave measurement assembly 20 includes a plurality of ultrasonic array transducers 21, the ultrasonic array transducers 21 being disposed in the vessel 110 and configured to measure acoustic signals within the cavity 100, the ultrasonic array transducers 21 being electrically connected to the processor 35, the processor 35 being configured to determine a minimum miscible pressure corresponding to the core powder 103 based on the driving pressure and the acoustic signals, wherein the acoustic signals are generated by ultrasonic waves of the ultrasonic array transducers 21 transmitted through the core powder 103.

Specifically, the liquid injection port 101 is located at the top of the cavity 100 and connected to the carbon dioxide injection unit outlet valve 422, the liquid injection port 102 is located at the bottom of the cavity 100 and connected to the crude oil injection unit outlet valve 412, and crude oil and liquid carbon dioxide enter the cavity 100 through the liquid injection port 102 and the liquid injection port 101.

Wherein the carbon dioxide injection unit inlet valve 421 and the crude oil injection unit inlet valve 411 are respectively connected with the six-way valve 32, and the flow direction, pressure and flow rate of the fluid entering the carbon dioxide injection unit 42 and the crude oil injection unit 41 are controlled by the six-way valve 32.

In this way, the container assembly 10 is adopted to contain the core powder 103, the cavity cover 112 is adopted to compact the core powder 103, the ultrasonic array transducer 21 is adopted to capture the acoustic signals of liquid carbon dioxide and crude oil under different pressures, and the cross correlation calculation is carried out on the collected acoustic signals.

In some embodiments, the container 110 includes a container body 111 and a cavity cover 112, the container body 111 has an opening, the cavity cover 112 covers the opening to enclose the cavity 100 with the container body 111, and the cavity cover 112 is configured to abut against the outside of the core powder 103 to compact the core powder 103, as shown in fig. 2.

Specifically, the cavity cover 112 has a certain thickness, so that the cavity cover 112 has higher compressive strength and hardness, can bear the pressure from the core powder 103, and prevent the cavity cover 112 from cracking and damaging, and a cavity cover sealing ring 160 is arranged on one circumference of the cavity cover 112 to seal the inlet of the cavity 100.

Wherein, 8 through holes are formed around the cavity cover 112, and internal threads are formed inside the through holes and are used for being matched with external threads of the threaded fastener 120, as an alternative implementation manner, the cavity cover 112 is connected to the container body 111 through the threaded fastener 120, and the fastening degree of the threaded fastener 120 is adjustable, so that the cavity cover 112 compresses the core powder 103.

In some embodiments, the container assembly 10 further includes a support 130, where the container body 111 is connected to the support 130 and can rotate around a horizontal axis relative to the support 130, and two ends of the support are respectively provided with a rotating shaft 140, so that the container assembly 10 can rotate around the rotating shaft 140 to uniformly mix the core powder 103 in the cavity 100, so that the core powder and the support can be tightly combined together.

The bracket 130 is used for supporting the container assembly 10, the bracket 130 is fixedly mounted on the base 150, so that vibration of the container assembly 10 caused by pressurization during testing can be avoided, a stabilizing effect is achieved, and the bracket 130 and the base 150 can be integrally formed or connected in a welding manner.

In some embodiments, a plurality of ultrasonic array transducers 21 are disposed at intervals on the peripheral side of the cavity 100, each ultrasonic array transducer 21 being an ultrasonic array; at least one of the plurality of ultrasonic array transducers 21 serves as an ultrasonic transmitter, and the remaining ultrasonic array transducers 21 among the plurality of ultrasonic array transducers 21 serve as ultrasonic receivers.

The ultrasonic array transducer 21 can adjust focal length and phase, improve signal to noise ratio of signal measurement, and accurately find an interface. In the measurement process, the interface position is not fixed, when liquid carbon dioxide is injected into the cavity 100, the liquid carbon dioxide diffuses to cause the volume expansion of crude oil, so that the oil phase interface moves upwards, the ultrasonic array transducer 21 is used for phase modulation and focusing again while synchronizing the sound wave scanning signals, the signal of the receiving end is kept stable, and the ultrasonic array transducer 21 receiving the ultrasonic wave signals can be ensured to receive the sound wave signals with maximum intensity.

Specifically, the use of a plurality of ultrasonic array transducers 21 to receive ultrasonic signals can improve the accuracy of ultrasonic reception signals, thereby avoiding the phenomenon that when only a single ultrasonic array transducer 21 receives reflected signals, the reflected signals cannot be captured after the reflective interface is changed.

The ultrasonic array transducers 21 are connected to the ultrasonic transmitting and receiving instrument 22 through ultrasonic signal cables, and are used for capturing characteristic parameter information such as waveforms, frequency spectrums and the like of crude oil and liquid carbon dioxide in a mixed phase state under different temperature and pressure conditions, the ultrasonic transmitting and receiving instrument 22 is connected with the processor 35, data processing software is arranged in the processor 35, and the data processing software in the processor 35 is utilized to perform cross-correlation calculation on waveform signals under adjacent pressure, so that MMP of liquid carbon dioxide displacement crude oil can be obtained.

After the whole cavity 100 is at constant temperature, any one of the ultrasonic array transducers 21 outside the cavity 100 can transmit acoustic signals, and the other three ultrasonic array transducers 21 receive the acoustic signals, so that an interface can be found at the beginning, the four ultrasonic array transducers 21 are linked to the same processor 35, the phase of the acoustic array of the transmitting source is adjusted by the processor 35, the angle and the focal distance are changed, the oil phase interface is swept, the reflection or transmission signals of the oil phase interface inside the hole are received by any one of the 3 ultrasonic array transducers 21 to reach a peak value, then the phase and the focal distance of the transmitting source are fixed, and the frequency spectrum and the characteristic frequency of the reflection or transmission signals are obtained.

In some embodiments, the plunger pump 31 is connected to the crude oil injection unit 41 and the carbon dioxide injection unit 42, respectively, and is configured to inject the displacement medium into the crude oil injection unit 41 and the carbon dioxide injection unit 42 by driving pressure, as shown in fig. 2.

Specifically, the two ends of the plunger pump 31 are respectively provided with a plunger pump inlet valve 311 and a plunger pump outlet valve 312, and the plunger pump inlet valve 311 is connected with the processor 35, so that different working modes can be selected according to the processor 35, and the injection pressure and speed of the liquid carbon dioxide can be controlled.

Specifically, the six-way valve 32 is connected to the plunger pump 31, the plunger pump 31 is in a single-pipe operation mode, first, the six-way valve 32, the crude oil injection unit inlet valve 411 and the crude oil injection unit outlet valve 412 are sequentially opened, crude oil is injected into the cavity 100, after the crude oil is injected, the crude oil injection unit inlet valve 411 and the crude oil injection unit outlet valve 412 are closed, and the carbon dioxide injection unit inlet valve 421 and the carbon dioxide injection unit outlet valve 422 are opened, at this time, the operation pipeline of the plunger pump 31 is cut into a liquid carbon dioxide pipeline, and the pressure of the liquid carbon dioxide is gradually increased and injected into the cavity 100.

In some embodiments, the delivery assembly 40 further includes an incubator 43, and the crude oil injection unit 41, the carbon dioxide injection unit 42, and the vessel 110 are all located within the incubator 43, so that the overall temperature of the chamber 100 can be controlled to be in a constant temperature state, so that acoustic signals at different pressure points at the same temperature can be monitored, and different temperatures can be set by adjusting the heating program of the incubator.

The following describes the method for measuring the mixed phase pressure provided by the invention further:

Fig. 3 is a flowchart of a method for measuring a mixed phase pressure according to an embodiment of the present application, including the following steps:

s101, referring to a phase diagram under the temperature condition corresponding to the carbon dioxide according to the temperature condition of the mixed phase pressure test, and liquefying the carbon dioxide.

Specifically, the compressibility of carbon dioxide is very strong, it is difficult to directly inject gaseous carbon dioxide into the cavity 100, thereby prolonging the test period, and injecting gaseous carbon dioxide into the cavity can cause the crude oil to expand very severely, and measurement cannot be performed. Therefore, before starting the measurement, the gaseous carbon dioxide needs to be liquefied, and the way of liquefying the gaseous carbon dioxide is two ways of pressurization and cooling, in this embodiment, the temperature is kept at the experimental temperature, and the gaseous carbon dioxide is liquefied by adopting a pressurization way.

S102, pressurizing and injecting crude oil into a closed cavity in which core powder is placed, then injecting liquid carbon dioxide into the closed cavity in which the crude oil is injected, and detecting a first acoustic signal in the cavity after the liquid carbon dioxide is injected, wherein the core powder has a preset particle size, and the first acoustic signal is generated after ultrasonic waves of an ultrasonic array transducer in a pressure measuring device are transmitted through the core powder.

Specifically, firstly, selecting core powder 103 with a particle size close to that of a reservoir by combining pore parameter data of the reservoir; washing off floating ash in the core powder 103 in deionized water, and measuring the total volume of the core powder 103 by a drainage method after the floating ash is washed off; then, re-drying the core powder 103, loading the core powder 103 into the cavity 100, then, covering the cavity cover 112, and gradually tightening the threaded fasteners 120 on the cavity cover 112 according to a diagonal sequence to further compact the core powder 103 in the cavity 100 by the cavity cover 112; the tightness of the container assembly 10 is judged according to the pressure change of a pressure gauge (not shown) at the filling port 101 at the top of the chamber 100.

Specifically, the pore volume of the pore medium composed of the core powder 103 in the cavity 100 is estimated according to the cavity volume, the drainage volume of the core powder 103 and the pressing depth of the cavity cover 112, and the crude oil is injected into the closed cavity 100 with the core powder 103 under pressure.

The crude oil is injected slowly at a low speed, and the injection amount of the crude oil is about 30% of the pore medium system, and the pores at the lower part of the cavity 100 are filled with the oil phase. Because of capillary force between the pores and the surface of the cavity 100, the oil phase interface inside the core powder 103 is not slightly bent horizontally, but the monitoring effect of the sound wave on the interface is not affected, and the whole of the cavity 100 filled with the crude oil is placed in the incubator 43, so that the whole equipment reaches the preset temperature condition.

Specifically, liquid carbon dioxide is injected into the cavity 100 for injecting crude oil through the liquid injection port 101, the ultrasonic array transducer 21 is used for collecting a first acoustic signal, and a relatively stable oil phase interface can be maintained in the pore before the mixing, and at this time, the pore is composed of two phases of an oil phase and a liquid carbon dioxide phase.

And S103, increasing the pressure of liquid carbon dioxide in the cavity, and measuring a second acoustic signal in the pressurized cavity, wherein the second acoustic signal is generated after ultrasonic waves are transmitted through the core powder.

Specifically, before the phase mixing, the correlation coefficient of the acoustic wave characteristics between adjacent pressure points is high, once the phase mixing occurs, a phase mixing belt can occur in the pore, and the newly occurring phase mixing belt is equivalent to adding an interface, so that characteristic parameters such as waveform, frequency spectrum and the like of acoustic wave signals can be obviously changed.

S104, determining cross-correlation coefficients of the second acoustic signal and the first acoustic signal, drawing the cross-correlation coefficients into a curve, and determining the pressure of the corresponding liquid carbon dioxide as the minimum miscible pressure corresponding to the core powder when an inflection point appears in the cross-correlation coefficient curve.

Specifically, the cross correlation coefficient is used to represent the correlation degree of two signals at different moments, the larger the cross correlation coefficient is, the higher the similarity of the two signals is, in this embodiment, the method of gradually increasing the pressure value is selected to measure MMP, and the selection range of the pressure value is smaller.

Specifically, for the second acoustic signal, the cross-correlation coefficient is solved by comparing with the first acoustic signal, and a relatively stable oil phase interface can be kept in the pore interior before mixing, so that the correlation coefficient of the acoustic wave characteristics between adjacent pressure points is high, the cross-correlation coefficient is a smooth curve, once a relatively obvious mixed phase zone appears, the cross-correlation coefficient curve can appear an inflection point, and then by combining with the spectrum information difference, whether the mixed phase appears in the pore interior can be judged, and the pressure point corresponding to the occurrence of the turning point of the cross-correlation coefficient curve is MMP of the oil phase and liquid carbon dioxide in the pore interior under the temperature condition.

After the measurement, the relief valve 34 externally connected to the liquid injection port 101 was opened, and the cavity pressure was released at the pressure release port 33 to take out the crude oil mixture for the next experiment.

In some embodiments, before the pressurized injection of the crude oil into the closed cavity in which the core powder 103 is placed, the method further comprises: the core powder 103 with the preset particle size is screened out, and the core powder 103 is compacted in the closed cavity 100.

The core powders 103 with different apertures are distributed in the cavity 100 in a staggered manner, so that a porous structure with various types, complex structure and strong heterogeneity is formed in the three-dimensional space.

Firstly, drying a reservoir rock core, crushing the rock core by adopting a jaw crusher or a impact crusher, screening out rock core powder 103 with different particle sizes by adopting screen powder with different mesh numbers according to the pore parameters of an actual reservoir, specifically, if the influence of a pore structure on MMP is to be analyzed, changing the particle size of the reservoir rock core, and comparing acoustic signals of pressure points of the rock core powder 103 with different particle sizes.

Specifically, the core powder 103 is a real core, which is more in line with the structure of the actual reservoir porous medium, and the core powder 103 is compacted by the cavity cover 112, so that the core powder 103 is mutually adhered, the pore size is reduced, and the pore structure is more stable.

In some embodiments, before the pressurized injection of the crude oil into the closed cavity in which the core powder 103 is placed, the method further comprises: the core powder 103 is subjected to a wetting treatment.

Specifically, the wettability of the reservoir rock can influence the capillary pressure, the relative permeability and the seepage characteristic of the reservoir rock, so that the distribution of fluid in the porous medium structure is influenced, and the distribution is a key factor influencing MMP calculation, so that the wettability influence is analyzed, the wettability treatment is performed on the core powder 103, and the wettability treatment is performed by contrasting the mixed phase pressure points under the powder with different wetting conditions.

In this embodiment, a device and a method for measuring a mixed phase pressure, the device includes a container assembly 10, a pressure assembly 30, a conveying assembly 40 and an acoustic wave measuring assembly 20; the core powder 103 is placed within the container assembly 10, and the delivery assembly 40 is configured to inject crude oil and liquid carbon dioxide into the interior of the cavity 100; the pressure assembly 30 is configured to provide a driving pressure to the delivery assembly 40; the acoustic wave measurement assembly 20 is configured to measure acoustic signals within the cavity 100; the method comprises the steps of pressurizing and injecting crude oil into a cavity 100 in which core powder 103 is placed, injecting liquid carbon dioxide into the cavity 100 after the crude oil is injected, and measuring a first acoustic signal; increasing the pressure of the liquid carbon dioxide within the cavity 100 and measuring a second acoustic signal; and calculating the cross-correlation coefficient of the second acoustic signal and the first acoustic signal, wherein the corresponding pressure is the minimum miscible pressure when the inflection point appears on the cross-correlation coefficient curve. In this way, the container assembly 10 is adopted to contain the core powder 103, the cavity cover 112 is adopted to compact the core powder 103, the ultrasonic array transducer 21 is adopted to capture the acoustic signals of liquid carbon dioxide and crude oil under different pressures, and the cross correlation calculation is carried out on the collected acoustic signals.

It should be noted that references in the specification to "one embodiment," "an example embodiment," "some embodiments," etc., indicate that the embodiment may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

Generally, terms should be understood at least in part by use in the context. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, at least in part depending on the context. Similarly, terms such as "a" and "an" may also be understood to convey a singular usage or a plural usage, depending at least in part on the context.

It should be readily understood that the terms "on … …", "above … …" and "above … …" in this disclosure should be interpreted in the broadest sense so that "on … …" means not only "directly on something" but also includes "on something" with intermediate features or layers therebetween, and "above … …" or "above … …" includes not only the meaning "on something" or "above" but also the meaning "above something" or "above" without intermediate features or layers therebetween (i.e., directly on something).

Further, spatially relative terms, such as "below," "beneath," "above," "over," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (9)

1. The mixed phase pressure measuring device is characterized by comprising a container assembly, an acoustic wave measuring assembly, a pressure assembly and a conveying assembly;

The container assembly comprises an openable and closable container, the container is provided with a closed cavity, the cavity is provided with a liquid injection port and an oil injection port, and the cavity is configured to contain core powder of a real core after wetting treatment; wherein the core powder has a preset particle size and is compacted in the cavity;

The container assembly further comprises a bracket, wherein the container body of the container is connected to the bracket and can rotate around a horizontal axis relative to the bracket so as to uniformly mix the core powder in the cavity;

The conveying assembly comprises a crude oil injection unit and a carbon dioxide injection unit, wherein the crude oil injection unit is communicated with the oil injection port and used for injecting crude oil into the cavity, and the carbon dioxide injection unit is communicated with the liquid injection port and used for injecting liquid carbon dioxide into the cavity;

The pressure assembly is configured to provide driving pressures for the crude oil injection unit and the carbon dioxide injection unit, and comprises a plunger pump and a processor, wherein the plunger pump is controlled by the processor and used for feeding back pressure points in real time;

The acoustic wave measuring assembly comprises a plurality of ultrasonic array transducers, is used for improving the accuracy of ultrasonic wave receiving signals, and can still capture reflected signals after a reflecting interface is changed; the ultrasonic array transducer can adjust focal length and phase, and improve signal to noise ratio of signal measurement so as to accurately find an interface; the ultrasonic array transducer is arranged in the container and is configured to measure an acoustic signal in the cavity, the ultrasonic array transducer is electrically connected with the processor, and the processor is configured to determine a minimum miscible pressure corresponding to the core powder according to the driving pressure and the acoustic signal, wherein the acoustic signal is generated after ultrasonic waves of the ultrasonic array transducer are transmitted through the core powder;

The ultrasonic array transducers are connected to an ultrasonic transmitting and receiving instrument through ultrasonic signal cables and used for capturing waveform and spectrum characteristic parameter information of crude oil and liquid carbon dioxide in a miscible state under different temperature and pressure conditions, the ultrasonic transmitting and receiving instrument is connected with the processor, and the processor is used for carrying out cross-correlation calculation on waveform signals under adjacent pressures so as to obtain the minimum miscible pressure of liquid carbon dioxide displacement crude oil.

2. The apparatus of claim 1, wherein the container comprises the container body and a cavity cover, the container body having an opening, the cavity cover covering the opening to enclose the cavity with the container body, and the cavity cover being configured to abut against an outside of the core powder to compact the core powder.

3. The apparatus of claim 2, wherein the cover is connected to the container body by a threaded fastener, and the tightening of the threaded fastener is adjustable to compress the core powder by the cover.

4. A miscible pressure measurement apparatus as claimed in any of claims 1 to 3 wherein a plurality of said ultrasonic array transducers are spaced around the perimeter of said cavity, each said ultrasonic array transducer being an ultrasonic array; at least one of the plurality of ultrasonic array transducers serves as an ultrasonic transmitter, and the remaining ultrasonic array transducers of the plurality of ultrasonic array transducers serve as ultrasonic receivers.

5.A miscible pressure measurement apparatus as claimed in any of claims 1 to 3, wherein the plunger pump is connected to the crude oil injection unit and the carbon dioxide injection unit respectively and is configured to inject a displacement medium into the crude oil injection unit and the carbon dioxide injection unit by the driving pressure.

6. The miscible pressure measurement apparatus of claim 5 wherein said delivery assembly further comprises an incubator, said crude oil injection unit, said carbon dioxide injection unit, and said vessel being located within said incubator.

7. A method of measuring a mixed phase pressure, characterized by being applied to the mixed phase pressure measuring apparatus as claimed in any one of claims 1 to 6, the method comprising:

According to the temperature condition of the mixed phase pressure test, referring to a phase diagram under the temperature condition corresponding to carbon dioxide, and liquefying the carbon dioxide;

Pressurizing and injecting crude oil into a closed cavity in which core powder is placed, injecting liquid carbon dioxide into the closed cavity in which the crude oil is injected, and detecting a first acoustic signal in the cavity after the liquid carbon dioxide is injected, wherein the core powder has a preset particle size, and the first acoustic signal is generated after ultrasonic waves of an ultrasonic array transducer in the miscible pressure measuring device are transmitted through the core powder;

Increasing the pressure of liquid carbon dioxide in the cavity, and measuring a second acoustic signal in the cavity after pressurization, wherein the second acoustic signal is generated after ultrasonic waves are transmitted through the core powder;

And determining the cross-correlation coefficient of the second acoustic signal and the first acoustic signal, drawing the cross-correlation coefficient into a curve, and determining the pressure of the liquid carbon dioxide corresponding to the inflection point of the cross-correlation coefficient curve as the minimum miscible pressure corresponding to the rock core powder.

8. The method of claim 7, wherein prior to the pressurized injection of the crude oil into the closed cavity containing the core powder, further comprising: and screening out core powder with preset particle size, and compacting the core powder in the closed cavity.

9. The method according to any one of claims 7 or 8, wherein before the pressurized injection of the crude oil into the closed cavity in which the core powder is placed, the method further comprises: and carrying out wetting treatment on the core powder.