CN114624274A - Method for detecting multiphase flow phase content - Google Patents

Abstract

The invention provides a method for detecting the phase content of multiphase flow. The method comprises the following steps: sampling the multiphase flow to be detected to obtain a multiphase flow sample, and performing three-phase separation on oil, gas and water in the multiphase flow sample; respectively carrying out nuclear magnetic resonance on water and oil in the purified water and the multiphase flow sample to obtain first amplitude values of corresponding free attenuation signals, and determining hydrogen-containing indexes corresponding to the water and the oil by using the first amplitude values; applying a diffusion editing pulse sequence to the water and the oil to obtain diffusion coefficients corresponding to the water and the oil; and carrying out pulse transmission on the multiphase flow to be detected by using the variable echo interval pulse sequence to obtain an echo signal, and determining the phase content of the multiphase flow to be detected according to the echo signal, the hydrogen-containing index and the diffusion coefficient. The invention makes up the defect that oil and water are difficult to distinguish, realizes the quantification of the contents of different fluid components, does not need to collect relaxation information of the measured fluid, has high measurement speed, and can realize the on-line measurement of the multiphase flow phase content rate with full range, high efficiency, environmental protection and safety.

Description

Method for detecting multiphase flow phase content

Technical Field

The invention relates to the technical field of petroleum industry, in particular to a method for detecting multiphase flow phase content.

Background

In the industrial links of oil exploitation, gathering and transportation, fracturing, oil testing and the like, a large amount of complex multiphase fluids needing to be detected exist, and the complex fluids are mainly formed by mixing 3 different components such as crude oil, formation water, natural gas and the like. In addition, due to the requirement of industrial production, multiphase flow always keeps a continuous flowing state, and online detection is needed, which brings great difficulty to the quantitative detection of the phase content, and means that the traditional method which depends on relaxation spectrum and diffusion spectrum and needs to take a long time to measure the phase content is not applicable.

In the existing detection mode, after sampling multiphase flow to be detected regularly (once a day or even longer), natural sedimentation or centrifugation is adopted, and after layering is realized based on density difference of each component, metering is carried out. The disadvantages of such methods are quite evident: (1) sampling after the fluid flow state needs to be blocked (production is hindered); (2) the detected sample is discarded to cause pollution; (3) the time is required from sampling to laboratory detection, so that the detection data is delayed, and the efficiency is low; (4) in the sampling process, due to the change of the temperature and the pressure of the sample, the physical parameters of the sample can be changed, and the measurement result cannot reflect the real data of the fluid in the pipeline.

The application of the nuclear magnetic resonance technology in the aspect of quantitative detection of the complex fluid is mature, and the nuclear magnetic resonance technology is distinguished due to the advantages of accuracy, greenness, safety and the like compared with other technologies, but the current nuclear magnetic resonance detection technology of the complex fluid also depends on sampling measurement, namely cannot be used for on-line measurement of the flowing fluid.

Disclosure of Invention

The embodiment of the invention mainly aims to provide a method for detecting the multiphase flow phase content, so that the defect that the multiphase flow phase content is difficult to distinguish when groups are distinguished by adopting relaxation time parameters is overcome, and the online measurement of the multiphase flow phase content can be realized.

In order to achieve the above object, an embodiment of the present invention provides a method for detecting a phase content of a multiphase flow, where the method includes:

sampling multiphase flow to be detected to obtain a multiphase flow sample, and performing three-phase separation on oil, gas and water in the multiphase flow sample;

respectively carrying out nuclear magnetic resonance on the purified water and the oil in the multiphase flow sample to obtain a first amplitude of a corresponding free attenuation signal, and determining a hydrogen-containing index corresponding to the water and the oil in the multiphase flow sample by using the first amplitude;

applying a diffusion editing pulse sequence to the water and the oil in the multiphase flow sample to obtain a diffusion coefficient corresponding to the water and the oil in the multiphase flow sample;

and carrying out pulse transmission on the multiphase flow to be detected by using the variable echo interval pulse sequence to obtain an echo signal, and determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be detected according to the echo signal, the hydrogen-containing index and the diffusion coefficient.

Optionally, in an embodiment of the present invention, the method further includes: the corresponding phase content of three single-phase fluids of oil, gas and water are used for petroleum exploitation, gathering and transportation, fracturing and oil testing.

Optionally, in an embodiment of the present invention, the three-phase separation of oil, gas and water in the multiphase flow sample includes: and (3) carrying out three-phase separation on the multiphase flow sample by using a standing mode or a centrifugal technology to obtain three single-phase fluids of oil, gas and water.

Optionally, in an embodiment of the present invention, the performing nuclear magnetic resonance on the water and the oil in the purified water and the multiphase flow sample respectively to obtain the first amplitudes of the corresponding free decay signals includes: respectively putting the purified water and the oil in the multiphase flow sample into a testing container; the inner diameter and the outer diameter of the test container are the same as those of a fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter, and the length of the test container is larger than that of an antenna of the multiphase flow nuclear magnetic resonance flowmeter; and placing the test container in a detection area of the multiphase flow nuclear magnetic resonance flowmeter, and measuring to obtain the first amplitude values of free attenuation signals corresponding to water and oil in the purified water and the multiphase flow sample.

Optionally, in an embodiment of the present invention, the determining the hydrogen index corresponding to water and oil in the multiphase flow sample by using the first amplitude value includes: determining the hydrogen index of the water in the multiphase flow sample according to the ratio of the first amplitude of the free decay signal of the water in the multiphase flow sample to the first amplitude of the free decay signal of the purified water; and determining the hydrogen-containing index of the oil in the multiphase flow sample according to the ratio of the first amplitude of the free attenuation signal of the oil in the multiphase flow sample to the first amplitude of the free attenuation signal of the purified water.

Optionally, in an embodiment of the present invention, the performing pulse transmission on the multiphase flow to be detected by using the variable echo spacing pulse sequence to obtain the echo signal includes: connecting the multiphase flow to be detected with a multiphase flow nuclear magnetic resonance flowmeter so that the multiphase flow to be detected continuously flows under a probe of the multiphase flow nuclear magnetic resonance flowmeter, and performing two pulse transmissions with different half echo intervals on the multiphase flow to be detected by using a variable echo interval pulse sequence to obtain echo signals including a first echo signal and a second echo signal.

Optionally, in an embodiment of the present invention, the performing, by using the variable echo spacing pulse sequence, two pulse transmissions with different half echo spacings on the multiphase flow to be detected includes: pulse emission is carried out on the multiphase flow to be detected by using a 90-degree pulse and a 180-degree pulse which is separated from the 90-degree pulse by a first half echo interval, so as to obtain a scanning head amplitude value and a first echo signal; and carrying out pulse transmission on the multiphase flow to be detected by using a 90-degree pulse and a 180-degree pulse separated from the 90-degree pulse by a second half echo interval to obtain a second echo signal.

Optionally, in an embodiment of the present invention, the determining the corresponding phase content rates of oil, gas, and water in the multiphase flow to be detected according to the echo signal, the hydrogen-containing index, and the diffusion coefficient includes: and determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be detected according to the first echo signal, the second echo signal, the first half echo interval, the second half echo interval, the hydrogen-containing index and the diffusion coefficient.

The invention makes up the defect that oil and water are difficult to distinguish by using the difference of relaxation time, realizes the quantification of the contents of different fluid components based on the difference of diffusion coefficients of all the components of the fluid, does not need to collect the relaxation information of the fluid to be measured, has high measurement speed, and can realize the online measurement of the multiphase flow phase content rate with full range, high efficiency, environmental protection and safety.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a flow chart of a method for detecting phase fraction of a multiphase flow according to an embodiment of the present invention;

FIG. 2 is a flow chart of determining a first amplitude of a free running decay signal in an embodiment of the present invention;

FIG. 3 is a flowchart of the scanning of the echo spacing pulse sequence according to an embodiment of the present invention;

FIG. 4 is a flow chart of the phase fraction detection of the multiphase stream in an embodiment of the present invention;

fig. 5A and 5B are schematic diagrams of a pulse sequence with a varying echo spacing according to an embodiment of the present invention.

Detailed Description

The embodiment of the invention provides a method for detecting the multiphase flow phase content, which is suitable for all laboratories and engineering application fields related to (three-phase and within) online measurement of the multiphase flow phase content.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

At present, the existing multiphase flow phase content detection method relates to online detection of phase content of oil-gas-water three-phase flow, and mainly aims at detecting the phase content of relaxation time differences of components of the three-phase flow.

Fig. 1 is a flowchart illustrating a method for detecting a phase fraction of a multiphase flow according to an embodiment of the present invention, where the method includes:

step S1, sampling the multiphase flow to be measured to obtain a multiphase flow sample, and performing three-phase separation on oil, gas and water in the multiphase flow sample.

The multiphase flow to be detected is sampled, then oil, gas and water are separated in a standing or centrifugal mode, and the gas in the multiphase flow sample is natural gas.

Step S2, performing nuclear magnetic resonance on the purified water and the water and oil in the multiphase flow sample respectively to obtain corresponding first amplitude values of the free attenuation signals, and determining the hydrogen-containing index corresponding to the water and the oil in the multiphase flow sample by using the first amplitude values.

The method comprises the steps of utilizing a multiphase flow nuclear magnetic resonance flowmeter to perform nuclear magnetic resonance on water and oil in purified water and a multiphase flow sample respectively, and measuring a first amplitude value of a free attenuation (FID) signal. Furthermore, the ratio of the first amplitude of the FID of the oil and water sample to the first amplitude of the FID of the pure water reagent is the hydrogen index of the oil and water.

Step S3, a diffusion editing pulse sequence is applied to the water and the oil in the multiphase flow sample, and the diffusion coefficient corresponding to the water and the oil in the multiphase flow sample is obtained.

Wherein, a Diffusion editing (Diffusion editing) pulse sequence is applied to oil and water samples in the multiphase flow sample, and the Diffusion coefficients of the oil and the water are obtained by measurement.

Step S4, pulse-emitting the multiphase flow to be tested by using the variable echo interval pulse sequence to obtain echo signals, and determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be tested according to the echo signals, the hydrogen-containing index and the diffusion coefficient.

The method comprises the steps of adopting a variable echo interval pulse sequence to carry out pulse transmission on multiphase flow to be detected, and successively carrying out two times of scanning with different half echo intervals to obtain echo signals corresponding to the two times of scanning. In addition, the corresponding phase content rates of the oil, gas and water in the multiphase flow to be detected are determined according to different echo intervals, echo signals, hydrogen-containing indexes and diffusion coefficients of the pulse sequences scanned twice. Specifically, the phase fraction includes oil content, gas content and water content.

As an embodiment of the invention, the method further comprises: the corresponding phase content of three single-phase fluids of oil, gas and water are used for petroleum exploitation, gathering and transportation, fracturing and oil testing. For example: during oil exploitation, the oil reservoir dynamics can be known according to the oil content of the liquid phase, and the optimization of an exploitation strategy is guided; in the gathering and transportation link, the water content can guide the watering operation; in the fracturing and oil testing links, the gas content, the water content and the oil content are dynamically changed, and real-time monitoring is very important for accurately grasping the fracturing effect and evaluating the productivity.

As an embodiment of the present invention, the three-phase separation of oil, gas and water in a multiphase flow sample comprises: three-phase separation is carried out on the multiphase flow sample by using a standing mode or a centrifugal technology to obtain three single-phase fluids of oil, gas and water.

As an embodiment of the present invention, as shown in fig. 2, the obtaining of the first amplitude of the corresponding free decay signal by performing the nmr on the water and the oil in the pure water and the multiphase flow sample respectively includes:

step S21, respectively putting the purified water and the water and oil in the multiphase flow sample into a testing container; the inner diameter and the outer diameter of the test container are the same as those of a fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter, and the length of the test container is larger than that of an antenna of the multiphase flow nuclear magnetic resonance flowmeter.

The method comprises the following steps of preparing 3 test containers, wherein the inner diameter and the outer diameter of each test container are the same as the inner diameter and the outer diameter of a fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter, and the length of each test container is larger than the length of an antenna of the multiphase flow nuclear magnetic resonance flowmeter. 2 single-phase fluids (oil, water) were loaded into 2 test vessels, respectively, and a pure water reagent was loaded into the other test vessel.

And step S22, placing the test container in a detection area of the multiphase flow nuclear magnetic resonance flowmeter, and measuring to obtain the first amplitude values of free attenuation signals corresponding to water and oil in the purified water and the multiphase flow sample.

Wherein, 3 test containers are respectively arranged in a detection area of the multiphase flow nuclear magnetic resonance flowmeter, and the first amplitude of a corresponding free attenuation (FID) signal is measured (the FID signal is a continuously attenuated signal, and the maximum amplitude when the signal is attenuated again is the first amplitude). The ratio of the first amplitude of the FID of the oil and the water to the first amplitude of the FID of the pure water reagent is the hydrogen index of the oil and the water. The hydrogen index of the natural gas is in direct proportion to the pressure in the pipe, can be obtained by looking up a table, and can be used for installing a pressure gauge in a nuclear magnetic resonance pipeline and reading the pressure in the pipe in real time.

In this embodiment, determining the hydrogen index corresponding to water and oil in the multiphase flow sample by using the first amplitude value includes:

determining the hydrogen-containing index of the water in the multiphase flow sample according to the ratio of the first amplitude of the free attenuation signal of the water in the multiphase flow sample to the first amplitude of the free attenuation signal of the purified water;

and determining the hydrogen-containing index of the oil in the multiphase flow sample according to the ratio of the first amplitude of the free attenuation signal of the oil in the multiphase flow sample to the first amplitude of the free attenuation signal of the purified water.

As an embodiment of the present invention, the pulse transmission of the multiphase flow to be measured by using the variable echo spacing pulse sequence, and obtaining the echo signal includes:

the method comprises the steps of connecting a multiphase flow to be detected into a fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter so that the multiphase flow to be detected continuously flows under a probe of the multiphase flow nuclear magnetic resonance flowmeter, carrying out two pulse transmissions with different half echo intervals on the multiphase flow to be detected by utilizing a variable echo interval pulse sequence, and obtaining echo signals including a first echo signal and a second echo signal.

In this embodiment, as shown in fig. 3, performing two pulse transmissions with different half-echo intervals on the multiphase flow to be measured by using the variable echo interval pulse sequence includes:

step S31, pulse-emitting the multiphase flow to be tested by using a 90-degree pulse and a 180-degree pulse separated from the 90-degree pulse by a first half echo interval to obtain a scanning head amplitude and a first echo signal;

step S32, pulse-transmitting the multiphase flow to be measured by using a 90-degree pulse and a 180-degree pulse spaced apart from the 90-degree pulse by a second half echo spacing, to obtain a second echo signal.

Wherein, the pulse sequence used for the first scanning consists of a 90 DEG pulse and a 180 DEG pulse. The method comprises the steps of generating an FID signal after 90-degree pulse excitation, transmitting 180-degree pulses after a first half echo interval of the scanning head amplitude value of the FID signal, and then acquiring a first echo signal after the first half echo interval. A rescan is then performed, again with a rescan pulse sequence consisting of a 90 ° pulse and a 180 ° pulse, except that a second echo signal is acquired with a second half-echo interval.

In this embodiment, determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be measured according to the echo signal, the hydrogen index and the diffusion coefficient includes:

and determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be detected according to the first echo signal, the second echo signal, the first half echo interval, the second half echo interval, the hydrogen-containing index and the diffusion coefficient.

Specifically, the phase fraction S is derived from the formulae (1) to (4)_Oil、S_{Water (W)}、S_{Qi (Qi)}。

M(0)＝S_{Water (W)}M_{0, water}HI_{Water (W)}+S_OilM_{0, water}HI_Oil+S_{Qi (Qi)}M_{0, water}HI_{Qi (Qi)} (3)

S_{Water (W)}+S_Oil(s)+S_{Qi (Qi)}＝1 (4)

Wherein, T_{2, water}、T_{2, oil}Transverse relaxation times of water and oil, respectively, gamma is the gyromagnetic ratio, a fixed value, M_{0, oil}、M_{0, water}First amplitude, τ, of free decay (FID) signals corresponding to oil and water, respectively₁For the first half of the echo interval, τ₂For the second half echo interval, HI_Oil、HI_{Water (I)}And HI_{Qi (Qi)}Hydrogen index of oil, water and natural gas, M (0) is scanning head amplitude, D_Oil、D_{Water (W)}Diffusion coefficients of oil and water respectively, G is the magnetic field gradient of the multiphase flow nuclear magnetic resonance flowmeter, M (2 tau)₁) Is the amplitude of the echo acquired in the first scan, M (2 τ)₂) Is the echo amplitude, S, acquired in the second scan_Oil、S_{Water (W)}、S_{Qi (Qi)}The phase content of the multiphase flow oil, gas and water to be measured is respectively. The unknowns in the above formulae (1) to (4) include S_Oil、S_{Water (W)}、S_{Qi (Qi)}And the others are known parameters.

The invention uses nuclear magnetic resonance technology for online measurement of oil-gas-water multiphase flow phase content, and the principle is that quantitative discrimination is realized based on diffusion coefficient difference of different multiphase flow components. The technology replaces the existing sampling measurement method, simultaneously makes up the defect that individual parts are difficult to distinguish when the relaxation time parameters are adopted to distinguish groups, and realizes the online phase content detection method of the complex fluid with full range, high efficiency, environmental protection and safety.

In an embodiment of the present invention, as shown in fig. 4, a flow chart of multiphase flow nmr online phase fraction measurement according to the present invention is shown, and the flow chart includes two parts, namely a pre-calibration method and a formal measurement method. The preorder calibration method needs to sample to detect the basic parameters of the multiphase flow; the formal measurement method can quickly obtain the multiphase flow phase content only by two times of quick scanning with variable echo intervals, and the process can be repeatedly carried out. The method makes up the defect that oil and water are difficult to distinguish by using the difference of relaxation time in individual application scenes, and realizes quantitative evaluation of the content of different fluid components based on the difference of diffusion coefficients of the components of the fluid. The main carrier for implementing the invention is a multiphase flow nuclear magnetic resonance flowmeter, but is not limited to the device. Hardware requires that the static magnetic field generated by the nuclear magnetic resonance probe has a region of uniform gradient magnetic field (magnetic field gradient G) within which the probe antenna is placed. In practical implementation, the method includes two parts, namely a preamble calibration method and a formal measurement method, and the flow is shown in fig. 4:

method for scaling in preamble

Firstly, multiphase flow is sampled, and then three phases of oil, gas and water are separated in a standing or centrifugal mode. Preparing 3 test containers, wherein the inner diameter and the outer diameter of each test container are the same as the inner diameter and the outer diameter of the fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter, and the length of each test container is larger than the length of an antenna of the multiphase flow nuclear magnetic resonance flowmeter. 2 single-phase fluids (oil, water) were loaded into 2 test vessels, respectively, and a pure water reagent was loaded into the other test vessel. Respectively loading 3 test containers into detection regions of a multiphase flow nuclear magnetic resonance flowmeter, and measuring the first amplitude of a free attenuation (FID) signal to obtain M_{0, oil}、M_{0, water}. The ratio of the first amplitude of FID of the oil and water sample to the first amplitude of FID of the pure water reagent is the hydrogen index HI of the oil and water_Oil(s)、HI_{Water (W)}. Then, a Diffusion editing (Diffusion Ecoding) pulse sequence is applied to the oil and water samples, and the Diffusion coefficients D of the oil and the water are measured_Oil、D_{Water (W)}。

(II) formal measuring method

During formal measurement, the multiphase flow nuclear magnetic resonance flowmeter is connected to a fluid manifold to be measured, so that fluid passes through the probe under the condition of continuous flow. Multiphase flow into the pipe using the pulse trains shown in FIGS. 5A and 5BAnd (4) transmitting a line pulse. Two scans with different half-echo intervals are performed successively. The pulse sequence used for the first scan consists of one 90 ° pulse and one 180 ° pulse. Generating an FID signal after 90-degree pulse excitation, wherein the FID signal scans the initial amplitude M (0) and the half echo interval tau₁Post-emitting 180 DEG pulses, then tau₁The echo signal M (2 tau) is acquired₁). A rescan is then carried out, the rescan pulse sequence likewise consisting of a 90 DEG pulse and a 180 DEG pulse, with the exception of the half-echo spacing tau again₂Acquiring an echo signal M (2 τ)₂). Finally, the phase fraction S is deduced by the following formula_Oil、S_{Water (W)}、S_{Qi (Qi)}。

M(0)＝S_{Water (I)}M_{0, water}HI_{Water (W)}+S_OilM_{0, water}HI_Oil+S_{Qi (Qi)}M_{0, water}HI_{Qi (Qi)}

S_{Water (W)}+S_Oil+S_{Qi (Qi)}＝1

Where G is the magnetic field gradient and M (2. tau.)₁) And M (2 τ)₂) Is the echo amplitude acquired by two scans, M (0) is the FID signal amplitude acquired by the first scan, S_Oil、S_{Water (W)}、S_{Qi (Qi)}The phase content of the multiphase flow oil, gas and water to be measured is respectively. The unknowns in the above formula include S_Oil、S_{Water (W)}、S_{Qi (Qi)}The others are known parameters.

The invention makes up the defect that oil and water are difficult to distinguish by utilizing the difference of relaxation time, realizes the quantification of the contents of different fluid components based on the difference of diffusion coefficients of the components of the fluid, does not need to acquire the relaxation information of the fluid to be measured, has high measurement speed, and can realize the online measurement of the multiphase flow phase content rate with full range, high efficiency, environmental protection and safety.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

The principle and the implementation mode of the invention are explained by applying specific embodiments in the invention, and the description of the embodiments is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims (8)

1. A method for detecting phase content of a multiphase stream, the method comprising:

sampling multiphase flow to be detected to obtain a multiphase flow sample, and performing three-phase separation on oil, gas and water in the multiphase flow sample;

respectively carrying out nuclear magnetic resonance on the purified water and the oil in the multiphase flow sample to obtain a first amplitude of a corresponding free attenuation signal, and determining a hydrogen-containing index corresponding to the water and the oil in the multiphase flow sample by using the first amplitude;

applying a diffusion editing pulse sequence to the water and the oil in the multiphase flow sample to obtain a diffusion coefficient corresponding to the water and the oil in the multiphase flow sample;

and carrying out pulse transmission on the multiphase flow to be detected by using the variable echo interval pulse sequence to obtain an echo signal, and determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be detected according to the echo signal, the hydrogen-containing index and the diffusion coefficient.

2. The method of claim 1, further comprising: the corresponding phase content of three single-phase fluids of oil, gas and water are used for petroleum exploitation, gathering and transportation, fracturing and oil testing.

3. The method of claim 1, wherein the three-phase separation of oil, gas and water in the multiphase flow sample comprises: and (3) carrying out three-phase separation on the multiphase flow sample by using a standing mode or a centrifugal technology to obtain three single-phase fluids of oil, gas and water.

4. The method of claim 1, wherein performing nmr on the water and oil in the pure water and the multiphase flow sample to obtain corresponding first amplitudes of the free decay signals comprises:

respectively putting the purified water and the oil in the multiphase flow sample into a testing container; the inner diameter and the outer diameter of the test container are the same as those of a fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter, and the length of the test container is larger than that of an antenna of the multiphase flow nuclear magnetic resonance flowmeter;

and placing the test container in a detection area of the multiphase flow nuclear magnetic resonance flowmeter, and measuring to obtain the first amplitude values of free attenuation signals corresponding to water and oil in the purified water and the multiphase flow sample.

5. The method of claim 4, wherein the determining the hydrogen index corresponding to water and oil in the multiphase flow sample using the initial amplitude value comprises:

determining the hydrogen-containing index of the water in the multiphase flow sample according to the ratio of the first amplitude of the free attenuation signal of the water in the multiphase flow sample to the first amplitude of the free attenuation signal of the purified water;

and determining the hydrogen-containing index of the oil in the multiphase flow sample according to the ratio of the first amplitude of the free attenuation signal of the oil in the multiphase flow sample to the first amplitude of the free attenuation signal of the purified water.

6. The method of claim 1, wherein the pulse transmitting the multiphase flow to be tested by using the variable echo spacing pulse sequence to obtain the echo signal comprises:

the method comprises the steps of connecting a multiphase flow to be detected into a fluid pipe of the multiphase flow nuclear magnetic resonance flowmeter so that the multiphase flow to be detected continuously flows under a probe of the multiphase flow nuclear magnetic resonance flowmeter, carrying out two pulse transmissions with different half echo intervals on the multiphase flow to be detected by utilizing a variable echo interval pulse sequence, and obtaining echo signals including a first echo signal and a second echo signal.

7. The method of claim 6, wherein the two pulse transmissions with different half-echo intervals to the multiphase flow to be tested by using the variable echo interval pulse sequence comprises:

pulse emission is carried out on the multiphase flow to be detected by using a 90-degree pulse and a 180-degree pulse which is separated from the 90-degree pulse by a first half echo interval, so as to obtain a scanning head amplitude value and a first echo signal;

and carrying out pulse transmission on the multiphase flow to be detected by using a 90-degree pulse and a 180-degree pulse separated from the 90-degree pulse by a second half echo interval to obtain a second echo signal.

8. The method of claim 7, wherein the determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be tested according to the echo signal, the hydrogen index and the diffusion coefficient comprises:

and determining the corresponding phase content rates of oil, gas and water in the multiphase flow to be detected according to the first echo signal, the second echo signal, the first half echo interval, the second half echo interval, the hydrogen-containing index and the diffusion coefficient.

Images