Method for analyzing nuclear magnetic signal of separated water in mixed-phase fluid

Abstract

The invention discloses a method for analyzing a nuclear magnetic signal of separated water in a mixed-phase fluid, and relates to the technical field of gas reservoir development. The method comprises the following steps: respectively separating a nuclear magnetic signal of ethanol in a mixed solution of ethanol and water by adopting a time domain analysis method and a differential spectrum method; comparing and analyzing the nuclear magnetic signal of the ethanol in the separated mixed solution of the ethanol and the water with the nuclear magnetic signal of the ethanol with the same mass and the nuclear magnetic signal of the mixed solution of the ethanol and the heavy water with the same mass ratio, and verifying the feasibility of separating the nuclear magnetic signal of the water in the mixed solution by a time domain analysis method and a differential spectrum method; and then separating the nuclear magnetic signal of water in the mixed solution of ethanol and water by adopting a time domain analysis method and a differential spectrum method respectively, and determining an optimal separation method to separate the nuclear magnetic signal of water in the mixed solution of ethanol and water. According to the method, the T2 relaxation time distribution and content of different fluids in the mixed-phase solution can be quantitatively analyzed, and a feasibility verification basis is provided for quantitatively analyzing the content and distribution of water in a porous medium in the process of displacing a water-containing rock core with ethanol.

Description

Technical Field

[0001] The invention relates to the technical field of gas reservoir development for low-permeability oil and gas reservoir exploration and development, and more specifically to an analysis method for nuclear magnetic signals of separated water in a mixed-phase fluid. Background Art

[0002] During the development of gas reservoirs, the reservoirs are prone to capillary self-imbibition due to the small throat radius, primary water and micro-cracks in the reservoirs. At the same time, during the development of gas reservoirs, various water-based working fluids such as drilling fluids, completion fluids, well washing fluids, workover fluids and fracturing fluids will contact and invade the formations, forming liquid phase retention, resulting in a large number of pore throats being occupied by liquids, which reduces the effective diameter of the gas flow channel in the reservoir, increases the flow resistance sharply, and shows a significant water lock effect, which greatly limits the economic and efficient development of gas reservoirs.

[0003] In order to relieve the water lock damage of gas reservoirs, some experts and scholars have proposed that a desiccant can be injected to react quickly with the formation water in the reservoir near the wellbore, so as to consume the formation water and reduce the resistance of the channel. Ethanol is used as a carrier of the desiccant. When the desiccant reacts chemically with water, ethanol and water are miscible with each other. Since there is no interface and capillary force between the two fluids during the miscibility process, all fluid molecules can move freely, and the fluid as a whole behaves as a single-phase fluid. Therefore, it is impossible to determine the distribution and content of water in the mixed-phase fluid.

[0004] Nuclear magnetic resonance technology has been widely used in reservoir engineering and reservoir geology due to its advantages such as simplicity, speed and accuracy. In order to use nuclear magnetic resonance technology to quantitatively study the distribution and content of water in mixed phase fluids in porous media, it is necessary to know whether nuclear magnetic resonance technology can separate the nuclear magnetic signal of water in mixed phase solutions. There is a lack of research in this area in the existing technology. Summary of the invention

[0005] In order to overcome the defects and deficiencies in the above-mentioned prior art, the present invention provides an analysis method for the nuclear magnetic signal of separating water in a mixed phase fluid. The purpose of the present invention is to provide an analysis method for the nuclear magnetic signal of separating water in a mixed phase fluid, so as to study the feasibility of using nuclear magnetic resonance technology to separate the nuclear magnetic signal of water in a mixed phase solution, and meet the demand for separating the nuclear magnetic signal of miscible fluids. The present invention provides an analysis method for the nuclear magnetic signal of separating water in a mixed phase fluid, which quickly separates the nuclear magnetic signal of a miscible fluid by nuclear magnetic resonance technology, verifies the feasibility of using nuclear magnetic resonance technology to separate the nuclear magnetic signal of water in a mixed phase solution, and provides a feasibility verification basis for quantitatively analyzing the content and distribution of water in a mixed solution of ethanol and water in a porous medium during displacement.

[0006] In order to solve the problems existing in the above-mentioned prior art, the present invention is achieved through the following technical solutions: The present invention provides a method for analyzing nuclear magnetic signals of separated water in a mixed phase fluid, the method comprising the following steps: S1. Setting up an analysis and comparison test group and setting up nuclear magnetic resonance test parameters; the comparison test group includes an ethanol group, a water group, a mixed solution group of ethanol and water, a mixed solution group of ethanol and heavy water, and a mixed solution group of heavy water and water; S2. Separate the NMR signals of ethanol in the mixed solution of ethanol and water in multiple test groups by time domain analysis and differential spectrum method, and compare them with the NMR signals of ethanol of the same mass and the NMR signals of the mixed solution of ethanol and heavy water of the same mass ratio; verify the feasibility of separating the NMR signals of ethanol in the mixed solution of ethanol and water by time domain analysis and differential spectrum method; After the verification of steps S3 and S2 is passed, the nuclear magnetic resonance signals of water in the mixed solutions of ethanol and water in multiple test groups are separated by time domain analysis and differential spectrum method respectively; S4, comparing and analyzing the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the time domain analysis method, the nuclear magnetic signal of water of the same mass, and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity, to determine the critical mass ratio C when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by the time domain analysis method; S5. Compare and analyze the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by differential spectroscopy with the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity, and determine the critical mass ratio D when the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by differential spectroscopy is most accurate; S6. Compare the critical mass ratio C and the critical mass ratio D, and select the method corresponding to the smaller critical mass ratio to separate the nuclear magnetic resonance signal of water in the mixed solution of ethanol and water.

[0007] Further preferably, in step S2, the nuclear magnetic signals of ethanol in the mixed solutions of ethanol and water in multiple test groups are separated by time domain analysis and differential spectrum method respectively; the nuclear magnetic signals of ethanol separated by time domain analysis and the nuclear magnetic signals of ethanol separated by differential spectrum method are obtained in each test group; the accuracy of the nuclear magnetic signals of ethanol separated by time domain analysis and the nuclear magnetic signals of ethanol separated by differential spectrum method are qualitatively analyzed respectively, and the analysis shows that there is a critical mass ratio A, when the mass ratio of ethanol in the mixed solution of ethanol and water is greater than or equal to the critical mass ratio A, the nuclear magnetic signals of ethanol in the mixed solution of ethanol and water separated by time domain analysis and differential spectrum method are the most accurate.

[0008] Further preferably, in step S4, the integral size of the absolute value of the difference between the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by time domain analysis and the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity is compared and analyzed; when the integral value of the absolute value of the difference is zero, the nuclear magnetic signal of water in the mixed solution of ethanol and water coincides with the nuclear magnetic signal of water of the same mass, or with the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio C when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by time domain analysis.

[0009] Further preferably, in step S5, the integral size of the absolute value of the difference between the nuclear magnetic signal of water in the mixed solution of ethanol and water obtained by separation by differential spectroscopy and the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity is compared and analyzed; when the integral value of the absolute value of the difference is zero, the nuclear magnetic signal of water in the mixed solution of ethanol and water coincides with the nuclear magnetic signal of water of the same mass, or with the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio D when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by differential spectroscopy.

[0010] Further preferably, in step S6, the critical mass ratio C when the time domain analysis method is most accurate for separating the nuclear magnetic signal of water in a mixed solution of ethanol and water is less than the critical mass ratio D when the difference spectrum method is most accurate for separating the nuclear magnetic signal of water in a mixed solution of ethanol and water. That is, when the time domain analysis method is most accurate for separating the nuclear magnetic signal of water in a mixed solution of ethanol and water, the applicable range of the mass ratio of water to ethanol is wider than that of the difference spectrum method, and the time domain analysis method is more suitable for separating the nuclear magnetic signal of water in a mixed solution of ethanol and water.

[0011] Further preferably, in step S4, the critical mass ratio C when the time domain analysis method is used to most accurately separate the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is 5.25; in step S5, the critical mass ratio D when the difference spectrum method is used to most accurately separate the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is 8.01.

[0012] Further preferably, in step S2, the method of separating the nuclear magnetic resonance signal of ethanol in the mixed solution of ethanol and water by time domain analysis is specifically as follows: According to the set NMR test parameters, the NMR signal of the mixed solution of ethanol and water is measured, which is recorded as E2; the NMR signal of water with the same mass as the water in E2 is recorded as E1, and the NMR signal of the mixed solution of ethanol and heavy water with the same mass ratio as E2 is recorded as E3; The attenuation signal of E1 was subtracted from the attenuation signal of E2, and then the T2 relaxation time E2′ of the ethanol in the mixed solution of ethanol and water was inverted using the time domain analysis method. The difference between the relaxation time E3 of the mixed solution of ethanol and heavy water with the same mass ratio and the relaxation time E2″ of the ethanol solution with the same mass ratio was compared.

[0013] Further preferably, in step S2, the method of separating the nuclear magnetic signal of ethanol in the mixed solution by differential spectroscopy is specifically as follows: According to the set NMR test parameters, the NMR signal of the mixed solution of Yichunban and water was measured, which was recorded as E2; the NMR signal of water with the same mass as the water in E2 was recorded as E1, and the NMR signal of the mixed solution of ethanol and heavy water with the same mass ratio as E2 was recorded as E3; E1, E2 and E3 were inverted into T2 relaxation time distribution, and then the relaxation time of E1 was subtracted from the relaxation time of E2 using the difference spectrum method to obtain the T2 relaxation time E2' of ethanol in the mixed solution of ethanol and water. The difference between the relaxation time E2' and the relaxation time E3 of the mixed solution of ethanol and heavy water with the same mass ratio and the relaxation time E2" of the ethanol solution with the same mass ratio were compared.

[0014] Further preferably, in step S2, by performing a qualitative analysis on the nuclear magnetic resonance signal of ethanol in the mixed solution of ethanol and water, it is determined that when the mass proportion of ethanol in the mixed solution of ethanol and water increases, the T2 relaxation time distribution and the nuclear magnetic resonance signal amount of ethanol separated from the mixed solution of ethanol and water show a trend of gradually approaching the T2 relaxation time distribution and the nuclear magnetic resonance signal amount of the mixed solution of ethanol with the same mass and the same mass ratio of ethanol and heavy water.

[0015] Further preferably, in step S4, the critical mass ratio C when the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is most accurately separated by the time domain analysis method is determined, specifically, By using the time domain analysis method, the nuclear magnetic signal W2′ of water in the mixed solution of ethanol and water, the nuclear magnetic signal W1 of water having the same mass as the water in the mixed solution of ethanol and water, and the nuclear magnetic signal W3 of the mixed solution of heavy water and water having the same mass ratio of water to ethanol as the mixed solution of ethanol and water are obtained; The absolute value integral of the difference between W1, W2′ and W3 is used to quantitatively evaluate the distribution of the nuclear magnetic signals of the three. When the absolute value integral of the difference between W2′ and W1 and W3 is 0, the NMR signal of water in the mixed solution of ethanol and water separated by the time domain analysis method is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical value C.

[0016] More preferably, in step S5, the critical mass ratio D when the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is most accurately separated by differential spectroscopy is determined, specifically, By using the difference spectrum method, the nuclear magnetic signal W2" of water in the mixed solution of ethanol and water, the nuclear magnetic signal W1 of water with the same mass as the water in the mixed solution of ethanol and water, and the nuclear magnetic signal W3 of the mixed solution of heavy water and water with the same mass ratio of water to ethanol as the mixed solution of ethanol and water are obtained; The absolute value integral of the difference between W1, W2" and W3 was used to quantitatively evaluate the distribution of the nuclear magnetic signals of the three. When the absolute value integral of the difference between W2" and W1 and W3 is 0, the NMR signal of water in the mixed solution of ethanol and water separated by the differential spectrum method is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical value D.

[0017] More preferably, the nuclear magnetic resonance test parameters are specifically set as follows: the waiting time TW of the nuclear magnetic resonance test is set to 20000 ms, and the number of echoes NECH is set to a maximum of 18000.

[0018] Compared with the prior art, the beneficial technical effects brought by the present invention are as follows: Based on the principle of nuclear magnetic resonance, the present invention establishes a nuclear magnetic resonance signal separation method for ethanol and water in a mixed solution. This method can be used to quantitatively analyze the T2 relaxation time and distribution of different fluids in a mixed-phase solution, and also provides a feasibility verification basis for quantitatively analyzing the distribution and content of water in a mixed solution of ethanol and water in a porous medium during the displacement process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The relaxation time of ethanol in a mixed solution of ethanol and water (5:1) is separated by time domain analysis, and the relaxation time of ethanol and heavy water solution (5:1) and ethanol (5) is compared; Figure 2 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (5:1) separated by time domain analysis, and the NMR signal of ethanol and heavy water solution (5:1) and ethanol (5); Figure 3 The relaxation time of ethanol in the mixture of ethanol and water (4:2) separated by time domain analysis is compared with the relaxation time of ethanol and heavy water solution (4:2) and ethanol (4); Figure 4 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (4:2) separated by time domain analysis, and the NMR signal of ethanol and heavy water solution (4:2) and ethanol (4); Figure 5The relaxation time of ethanol in the mixture of ethanol and water (3:3) separated by time domain analysis is compared with the relaxation time of ethanol and heavy water solution (3:3) and ethanol (3); Figure 6 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (3:3) separated by time domain analysis, and the NMR signal of ethanol and heavy water solution (3:3) and ethanol (3); Figure 7 The relaxation time of ethanol in a mixed solution of ethanol and water (1:5) is separated by time domain analysis, and the relaxation time of ethanol and heavy water solution (1:5) and ethanol (1) is compared; Figure 8 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (1:5) separated by time domain analysis, and the NMR signal of ethanol and heavy water solution (1:5) and ethanol (1); Fig. 9 This is a comparison chart of the relaxation time of ethanol in a mixed solution of ethanol and water (5:1) separated by differential spectroscopy, the relaxation time of ethanol and heavy water solution (5:1) and ethanol (5); Fig.10 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (5:1) separated by differential spectroscopy, and the NMR signal of ethanol and heavy water solution (5:1) and ethanol (5); Fig.11 This is a comparison chart of the relaxation time of ethanol in a mixed solution of ethanol and water (4:2) separated by differential spectroscopy, the relaxation time of ethanol and heavy water solution (4:2) and ethanol (4); Fig.12 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (4:2) separated by differential spectroscopy, and the NMR signal of ethanol and heavy water solution (4:2) and ethanol (4); Fig.13 This is a comparison chart of the relaxation time of ethanol in a mixed solution of ethanol and water (3:3) separated by differential spectroscopy, the relaxation time of ethanol and heavy water solution (3:3) and ethanol (3); Fig.14 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (3:3) separated by differential spectroscopy, and the NMR signal of ethanol and heavy water solution (3:3) and ethanol (3); Fig.15 This is a comparison chart of the relaxation time of ethanol in a mixed solution of ethanol and water (1:5) separated by differential spectroscopy, the relaxation time of ethanol and heavy water solution (1:5) and ethanol (1); Fig.16 This is a comparison chart of the NMR signal of ethanol in a mixed solution of ethanol and water (1:5) separated by differential spectroscopy, and the NMR signal of ethanol and heavy water solution (1:5) and ethanol (1); Fig.17The relaxation time of water in the mixture of ethanol and water (5:1) separated by time domain analysis is compared with the relaxation time of water and heavy water solution (1:5) and water (1); Fig.18 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (5:1) separated by time domain analysis, and the NMR signal of water and heavy water solution (1:5) and water (1); Fig.19 The relaxation time of water in the mixture of ethanol and water (3:3) separated by time domain analysis is compared with the relaxation time of water and heavy water solution (3:3) and water (3); Fig. 20 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (3:3) separated by time domain analysis, and the NMR signal of water and heavy water solution (3:3) and water (3); Fig.21 The relaxation time of water in the mixture of ethanol and water (2:4) separated by time domain analysis is compared with the relaxation time of water and heavy water solution (4:2) and water (4); Fig. 22 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (2:4) separated by time domain analysis, and the NMR signal of water and heavy water solution (4:2) and water (4); Fig.23 The relaxation time of water in the mixture of ethanol and water (1:5) separated by time domain analysis is compared with the relaxation time of water and heavy water solution (5:1) and water (5); Fig.24 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (1:5) separated by time domain analysis, and the NMR signal of water and heavy water solution (5:1) and water (5); Fig.25 The absolute value integral of the difference between the NMR signals of water and water of the same mass in a mixed solution of ethanol and water by time domain analysis is related to the mass ratio of water to ethanol. Fig.26 It is the relationship between the absolute value integral of the difference between the NMR signals of water and water of the same mass specific gravity in the mixed solution of ethanol and water by time domain analysis and the mass ratio of water to ethanol; Fig. 27 This is a comparison chart of the relaxation time of water in a mixed solution of ethanol and water (5:1) separated by differential spectroscopy, and the relaxation time of water and heavy water solution (1:5) and water (1); Fig.28 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (5:1) separated by differential spectroscopy, and the NMR signal of water and heavy water solution (1:5) and water (1); Fig.29This is a comparison chart of the relaxation time of water in a mixed solution of ethanol and water (3:3) separated by differential spectroscopy, the relaxation time of water and heavy water solution (3:3) and water (3); Fig.30 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (3:3) separated by differential spectroscopy, and the NMR signal of water and heavy water solution (3:3) and water (3); Fig.31 This is a comparison chart of the relaxation time of water in a mixed solution of ethanol and water (2:4) separated by differential spectroscopy, and the relaxation time of water and heavy water solution (4:2) and water (4); Fig.32 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (2:4) separated by differential spectroscopy, and the NMR signal of water and heavy water solution (4:2) and water (4); Fig.33 This is a comparison chart of the relaxation time of water in a mixed solution of ethanol and water (1:5) separated by differential spectroscopy, and the relaxation time of water and heavy water solution (5:1) and water (5); Fig.34 This is a comparison chart of the NMR signal of water in a mixed solution of ethanol and water (1:5) separated by differential spectroscopy, and the NMR signal of water and heavy water solution (5:1) and water (5); Fig.35 The absolute value integral of the difference between the NMR signals of water and water of the same mass in a mixed solution of ethanol and water by differential spectroscopy is related to the mass ratio of water to ethanol. Fig.36 It is the relationship between the absolute value integral of the difference between the NMR signals of water and water of the same mass specific gravity in a mixed solution of ethanol and water by difference spectroscopy and the mass ratio of water to ethanol; Fig.37 This is the flow chart for the separation of NMR signals of water in a mixed fluid of ethanol and water. DETAILED DESCRIPTION

[0020] The following is an exemplary embodiment of the present invention that helps to fully understand the claims and their equivalents in conjunction with the accompanying drawings, wherein the specific details will be considered as exemplary only, and do not limit the scope of the present invention. Therefore, those of ordinary skill in the art can make various changes and modifications to the embodiments without departing from the scope and spirit of the present invention.

[0021] Example 1 As a preferred embodiment of the present invention, for ease of understanding, this embodiment further elaborates and illustrates the technical solution of the present invention with specific examples.

[0022] The present invention provides an analysis method for nuclear magnetic resonance signals of water separated in a mixed phase fluid, in particular, an analysis method for nuclear magnetic resonance signals of ethanol and water separated in a mixed solution of ethanol and water, and verifies and analyzes the feasibility of using nuclear magnetic resonance technology to separate nuclear magnetic resonance signals of water in a mixed phase solution. This method can not only add a new method for separating nuclear magnetic resonance signals of miscible flow using nuclear magnetic resonance technology, but also provide a feasibility verification basis for quantitatively analyzing the content and distribution of water in a mixed solution of ethanol and water in a porous medium during a displacement process.

[0023] Based on the reason of nuclear magnetic resonance, the hydrogen atom can be regarded as a nucleus with a spinning current loop rotating around the core direction. This nucleus can produce a magnetic moment, called nuclear magnetic moment (μ), also known as magnetic dipole. A single hydrogen nucleus has a nuclear magnetic moment, but a group of hydrogen nuclei does not exhibit a magnetic moment. When there is an external static magnetic field Bo, the entire group of atomic nuclei is magnetized and will exhibit a macroscopic magnetization vector as a whole. This macroscopic magnetization vector is parallel to the external magnetic field BO. According to Curie's law, the macroscopic magnetization vector M of the nucleus in the BO magnetic field is: Where k represents the Boltzmann constant; It represents the magnetic gyro ratio. The magnetic gyro ratio of hydrogen nucleus is 26.7519×10 7 (rad T -1 S -1 ) ; T represents absolute temperature, K; h represents Planck’s constant; I represents the spin quantum number of the atomic nucleus, I=0, 1 / 2, 1, 3 / 2…

[0024] From the above formula, we can see that the macroscopic magnetization vector M is the direct measurement object of nuclear magnetic resonance. When the atomic nucleus is selected, its numerical value is determined by the number of spins per unit volume N, the external magnetic field strength BO and the temperature T.

[0025] Due to the nature of NMR technology, NMR identification of different fluids can currently be divided into two categories: ① Fluid identification method based on pulse scanning sequence and time parameters mainly distinguishes the nuclear magnetic signals of different fluids by selecting appropriate scanning pulse sequence and test parameters. This is because different fluids have different diffusion abilities under the applied gradient field, which makes the relaxation time of different fluids different. This difference can be highlighted by changing the echo interval, etc. Then, the nuclear magnetic signals are inverted and processed by the difference spectrum method (DSM) and time domain analysis method (TDA) to obtain the relaxation time distribution of different fluids. The difference spectrum method refers to the waiting time for proton polarization to be determined by the CPMG pulse sequence during the nuclear magnetic resonance test, that is, the time before a new CPMG pulse sequence is restarted after a CPMG pulse test. The waiting time value needs to be large enough to ensure that the proton polarization is complete. If TW is too small, some spin nuclei may not have fully recovered to the thermal equilibrium state before being subjected to a 90-degree pulse and nuclear magnetic resonance begins. In this way, the detected nuclear magnetic signal will be weakened. When the TW value decreases to a certain extent, the nuclear magnetic signal of this part of the spin nuclei that cannot be fully polarized may not be detected at all. By setting different TW values ​​to measure the T2 relaxation time of the mixed oil, gas and water, the nuclear magnetic signal of a certain fluid can be retained by subtracting the relaxation time, that is, the attenuation curves of two nuclear magnetic signals with different waiting times are inverted to obtain the corresponding T2 spectrum, and then the T2 spectrum with a long waiting time is subtracted from the T2 spectrum with a short waiting time. The difference spectrum obtained is the T2 spectrum distribution of the remaining fluid. The time domain analysis method refers to subtracting the echo train signal with a short waiting time TWS from the echo train signal with a long waiting time TWL to obtain the echo train difference of another fluid, and then inverting the echo train difference with multi-exponential inversion to obtain the T2 signal distribution of this fluid. Both the time domain analysis method and the difference spectrum method belong to the double TW method, and the time domain analysis method is an extension and improvement of the difference spectrum method. It performs subtraction operations in the time domain and inverts the echo train difference. This method is more accurate and has less noise than the difference spectrum method.

[0026] ② The method of identifying fluids based on added reagents is mainly because the signal intensity of nuclear magnetic resonance is related to the fluid and temperature, and is generally a constant value. There are differences in the T1 and T2 values ​​of different fluids, and these values ​​can be changed by changing the magnetic field around the protons, thereby achieving the purpose of distinguishing different fluids through the difference in T1 and T2 values. The common method is mainly to add two major types of reagents: paramagnetic reagents and ferromagnetic reagents, which shorten the T1 and T2 times respectively, highlight other liquid signals, and achieve the purpose of distinguishing fluids.

[0027] In addition, fluids that cannot detect nuclear magnetic signals can be used to directly distinguish and identify fluids. The commonly used reagent is heavy water, which has chemical and physical properties similar to ordinary water and can largely replace ordinary water.

[0028] Based on the principle of nuclear magnetic resonance, it is known that the nuclear magnetic signal is only related to the number of hydrogen nuclei, magnetic gyrometry, external magnetic field and temperature, that is, the nuclear magnetic signal of a mixed solution of ethanol and water can be regarded as the collection of the nuclear magnetic signal of the same volume of ethanol and the same volume of water. Based on the above-mentioned nuclear magnetic resonance identification method for oil, gas and water and the principle of nuclear magnetic resonance, it can be known that the nuclear magnetic signal of a mixed solution of ethanol and water can be regarded as the sum of the nuclear magnetic signals of the separate masses of water and ethanol. Therefore, the nuclear magnetic signal of the same mass of ethanol can be deducted from one of the mixed solutions to achieve the purpose of separating the nuclear magnetic signal of water in the mixed solution of ethanol and water. Therefore, time domain analysis and differential spectrum method are used to separate nuclear magnetic signals.

[0029] Reference Manual Attached Figure 7 As shown, the technical solution of the present invention is described in detail below.

[0030] The first step is to set up multiple groups of mixed solutions of ethanol, water and heavy water with different mass ratios, and set the nuclear magnetic resonance test parameters.

[0031] Based on the above principle, multiple groups of mixed solutions of ethanol, water and heavy water with different mass ratios were designed (as shown in Table 1). The waiting time TW of the NMR test was set to 20000 ms, and the number of echoes NECH was set to a maximum of 18000 to ensure that the hydrogen nuclei in the fluid could relax completely.

[0032] Table 1 Solution ratios of different mass ratios In the second step, the time domain analysis method is used to separate the ethanol nuclear magnetic resonance signals in the multiple groups of mixed solutions of ethanol and water with different mass ratios in step S1, and the nuclear magnetic resonance signals of ethanol separated by the time domain analysis method are obtained.

[0033] Firstly, the time domain analysis method was used to separate the ethanol NMR signal in the mixed solution of ethanol and water. According to the set test parameters, the NMR signal E2 of the mixed solution of ethanol, water and heavy water with a mass ratio of 1:5:0 (Group 5), the NMR signal E1 of the mixed solution of ethanol, water and heavy water with a mass ratio of 0:5:0 (Group 3), and the NMR signal E3 of the mixed solution of ethanol, water and heavy water with a mass ratio of 1:0:5 (Group 2) in Table 1 were measured. The attenuation signal of E1 was subtracted from the attenuation signal of E2, and then the attenuation signal of ethanol, water and heavy water with a mass ratio of 1:5:0 was inverted by the time domain analysis method. The T2 relaxation time E2′ of ethanol in the water mixed solution (Group 5) is compared with the relaxation time difference between the mixed solution E3 of ethanol, water and heavy water with a mass ratio of 1:0:5 (Group 2) and the relaxation time E2" of the mixed solution E3 of ethanol, water and heavy water with a mass ratio of 1:0:0 (Group 1). A similar method can be used to compare the nuclear magnetic resonance signal E2′ of ethanol separated from the mixed solutions of ethanol and water with different mass ratios with the nuclear magnetic resonance signal E3 of the mixed solution containing ethanol and heavy water with the same mass ratio and the nuclear magnetic resonance signal E2" of the same mass of ethanol, such as Figure 1-Figure 8 shown.

[0034] The third step is to use the differential spectrum method to separate the ethanol nuclear magnetic resonance signals in the multiple groups of mixed solutions of ethanol, water and heavy water with different mass ratios in step S1 according to the set nuclear magnetic resonance test parameters, and obtain the nuclear magnetic resonance signals of ethanol separated by the differential spectrum method.

[0035] The difference spectrum method was used to separate the ethanol nuclear magnetic signal in the mixed solution. According to the set test parameters, the nuclear magnetic signal E2 of the mixed solution of ethanol, water and heavy water with a mass ratio of 1:5:0 (Group 5), the nuclear magnetic signal E1 of the mixed solution of ethanol, water and heavy water with a mass ratio of 0:5:0 (Group 3), and the nuclear magnetic signal E3 of the mixed solution of ethanol, water and heavy water with a mass ratio of 1:0:5 (Group 2) in Table 1 were measured. E1, E2 and E3 were inverted into T2 relaxation time distribution, and then the relaxation time of E1 was subtracted from the relaxation time of E2 by the difference spectrum method to obtain the distribution of ethanol, water and heavy water with a mass ratio of 1:5:0. The T2 relaxation time E2′ of ethanol in the water mixed solution (Group 5) is compared with the relaxation time E3 of the mixed solution of ethanol, water and heavy water with a mass ratio of 1:0:5 (Group 2) and the relaxation time E2" of the mixed solution of ethanol, water and heavy water with a mass ratio of 1:0:0 (Group 1). The difference between the three can be obtained by using the difference spectrum method. The nuclear magnetic signal E2′ of ethanol separated from the mixed solutions of ethanol and water with different mass ratios can be compared with the nuclear magnetic signal E3 of the mixed solution containing ethanol, water and heavy water with the same mass ratio and the nuclear magnetic signal E2" of the same mass of ethanol, as shown in the figure. Figure 9-Figure 16 shown.

[0036] In the fourth step, when the mass proportion of ethanol in the ethanol-water mixed solution increases, the T2 relaxation time distribution and nuclear magnetic signal quantity of ethanol separated from the ethanol-water mixed solution (group 5) and the T2 relaxation time distribution and nuclear magnetic signal quantity of the same mass ethanol solution (group 3) and the same mass ratio of ethanol and deuterium water solution (group 2) show a trend of gradually approaching each other. When the mass ratio of ethanol to water in the ethanol-water mixed solution is greater than a certain critical value, the T2 relaxation time of ethanol separated from the ethanol-water mixed solution coincides with the T2 relaxation time distribution of the same mass ratio of ethanol and deuterium water solution and the same mass ethanol solution, that is, the nuclear magnetic signal separation of ethanol in the ethanol-water mixed solution is the most accurate. In other words, there is a critical mass ratio of ethanol to water in the ethanol-water mixed solution. When the mass ratio of ethanol to water in the mixed solution is greater than or equal to the critical value, the time domain analysis method and the difference spectrum method are most accurate in separating the nuclear magnetic signal of ethanol in the ethanol-water mixed solution.

[0037] The fifth step is to find the critical mass ratio of water to ethanol in a mixed solution of ethanol and water when the time domain analysis method is most accurate for separating the nuclear magnetic resonance signals of water, and the critical mass ratio of water to ethanol in a mixed solution of ethanol and water when the difference spectrum method is most accurate for separating the nuclear magnetic resonance signals of water, according to the same method as above.

[0038] By verifying the separation of the T2 relaxation time of ethanol in a mixed solution of ethanol and water, it can be known that when the mass ratio of ethanol to water in the mixed solution of ethanol and water is greater than or equal to a certain value, the separated nuclear magnetic resonance signal of ethanol is most accurate. Therefore, the T2 relaxation time of water in a mixed solution of ethanol and water can be separated in the same way to find the critical mass ratio of water and ethanol in the mixed solution when the nuclear magnetic resonance signal of water in the mixed solution of ethanol and water is separated most accurately. First, through the above steps, the relaxation time of water in the mixed solution of ethanol and water with different mass ratios in Table 1 is separated by time domain analysis and difference spectrum method, as shown in FIG. Figures 17 to 24 , Figures 27 to 34 As shown. Then, the NMR signal W2′ of water in the ethanol and water mixture, the NMR signal W1 of water of the same mass, and the NMR signal W3 of the heavy water and water mixture of the same mass ratio are obtained by time domain analysis and differential spectrum method. When the absolute value integral of the difference between W2′ and W1, W2′ and W3 is 0 (such as Fig.25 and Fig.26 , Fig.35 and Fig.36 As shown in Table 2, the NMR signals of the two overlap, that is, the NMR signal of water in the mixed solution of ethanol and water separated by different methods is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio, as shown in Table 2. The specific experimental analysis process is as follows Fig.37 shown.

[0039] Table 2 The critical mass ratio of water to ethanol when the NMR signals of water in the mixed solution obtained by different methods overlap with the NMR signals of water of the same mass and the NMR signals of the mixed solution of heavy water and water of the same mass ratio Example 2 As another preferred embodiment of the present invention, refer to the attached specification Fig.37 As shown, this embodiment discloses a method for analyzing nuclear magnetic signals of separated water in a mixed phase fluid, the method comprising the following steps: S1. Setting up an analysis and comparison test group and setting up nuclear magnetic resonance test parameters; the comparison test group includes an ethanol group, a water group, a mixed solution group of ethanol and water, a mixed solution group of ethanol and heavy water, and a mixed solution group of water and heavy water; S2. Separate the NMR signals of ethanol in mixed solutions of ethanol and water in multiple test groups using time domain analysis and differential spectrum method, and compare them with the NMR signals of ethanol of the same mass and the NMR signals of mixed solutions of ethanol and heavy water of the same mass ratio; verify the feasibility of separating the NMR signals of ethanol in mixed solutions using time domain analysis and differential spectrum method; The nuclear magnetic signals of ethanol in the mixed solutions of ethanol and water in multiple test groups were separated by time domain analysis and differential spectrum method respectively; the nuclear magnetic signals of ethanol separated by time domain analysis and differential spectrum method were obtained in each test group; the accuracy of the nuclear magnetic signals of ethanol separated by time domain analysis and differential spectrum method were qualitatively analyzed respectively, and the results showed that there was a critical mass ratio A, and when the mass ratio of ethanol in the mixed solution of ethanol and water was greater than or equal to the critical mass ratio A, the nuclear magnetic signals of ethanol in the mixed solution of ethanol and water separated by time domain analysis and differential spectrum method were the most accurate.

[0040] After the verification of steps S3 and S2 is passed, the nuclear magnetic resonance signals of water in the mixed solutions of ethanol and water in multiple test groups are separated by time domain analysis and differential spectrum method respectively; S4, comparing and analyzing the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the time domain analysis method, the nuclear magnetic signal of water of the same mass, and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity, to determine the critical mass ratio C when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by the time domain analysis method; In step S4, a comparative analysis is performed on the integral of the absolute value of the difference between the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the time domain analysis method and the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity; when the integral of the absolute value of the difference is zero, the nuclear magnetic signal of water in the mixed solution of ethanol and water coincides with the nuclear magnetic signal of water of the same mass or the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio C when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by the time domain analysis method.

[0041] S5. Compare and analyze the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by differential spectroscopy with the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity, and determine the critical mass ratio D when the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by differential spectroscopy is most accurate; In step S5, the integral size of the absolute value of the difference between the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the differential spectrum method and the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity is compared and analyzed; when the integral value of the absolute value of the difference is zero, the nuclear magnetic signal of water in the mixed solution of ethanol and water coincides with the nuclear magnetic signal of water of the same mass or the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio D when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by the differential spectrum method.

[0042] S6. Compare the critical mass ratio C and the critical mass ratio D, and select a method corresponding to a smaller critical mass ratio to separate the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water; The critical mass ratio C when the time domain analysis method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water is less than the critical mass ratio D when the difference spectrum method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water. That is, when the time domain analysis method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water, the mass ratio of water to ethanol has a wider applicable range than the difference spectrum method. The time domain analysis method is more suitable for the separation of the nuclear magnetic signal of water in a mixed solution of ethanol and water. Specifically, In step S6, since the difference spectrum method and the time domain analysis method are the most accurate in separating the nuclear magnetic signal of water in a mixed solution of ethanol and water, the critical mass ratios of water to ethanol obtained by the two methods are different, among which the critical mass ratio of the difference spectrum method is greater than that of the time domain analysis method. This means that when separating the nuclear magnetic signal of water in a mixed solution of ethanol and water, the time domain analysis method has a smaller critical mass ratio and a wider range of application than the difference spectrum method. Therefore, compared with the two methods, the time domain analysis method is more suitable for separating the nuclear magnetic signal of water in a mixed solution of ethanol and water.

[0043] As an implementation of this embodiment, in step S2, the method of separating the nuclear magnetic resonance signal of ethanol in the mixed solution by using the time domain analysis method is specifically as follows: According to the set NMR test parameters, the NMR signal of the mixed solution of ethanol and water is measured, which is recorded as E2; the NMR signal of water with the same mass as the water in E2 is recorded as E1, and the NMR signal of the mixed solution of ethanol and heavy water with the same mass ratio as E2 is recorded as E3; The attenuation signal of E1 was subtracted from the attenuation signal of E2, and then the T2 relaxation time E2′ of the ethanol in the mixed solution of ethanol and water was inverted using the time domain analysis method. The difference between the relaxation time E3 of the mixed solution of ethanol and heavy water with the same mass ratio and the relaxation time E2″ of the ethanol solution with the same mass ratio was compared.

[0044] In step S2, the method of separating the nuclear magnetic signal of ethanol in the mixed solution by differential spectroscopy is specifically as follows: According to the set NMR test parameters, the NMR signal of the mixed solution of Yichunban and water was measured, which was recorded as E2; the NMR signal of water with the same mass as the water in E2 was recorded as E1, and the NMR signal of the mixed solution of ethanol and heavy water with the same mass ratio as E2 was recorded as E3; E1, E2 and E3 were inverted into T2 relaxation time distribution, and then the relaxation time of E1 was subtracted from the relaxation time of E2 using the difference spectrum method to obtain the T2 relaxation time E2' of ethanol in the mixed solution of ethanol and water. The difference between the relaxation time E2' and the relaxation time E3 of the mixed solution of ethanol and heavy water with the same mass ratio and the relaxation time E2" of the ethanol solution with the same mass ratio were compared.

[0045] In step S2, by performing a qualitative analysis on the nuclear magnetic resonance signal of ethanol in the mixed solution of ethanol and water, it is determined that when the mass proportion of ethanol in the mixed solution of ethanol and water increases, the T2 relaxation time distribution and the nuclear magnetic resonance signal amount of ethanol separated from the mixed solution of ethanol and water show a trend of gradually approaching the T2 relaxation time distribution and the nuclear magnetic resonance signal amount of the mixed solution of ethanol solution with the same mass and the mixed solution of ethanol and heavy water with the same mass ratio.

[0046] As another implementation of this embodiment, in step S4, the critical mass ratio C when the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is most accurately separated by the time domain analysis method is determined, specifically, By using the time domain analysis method, the nuclear magnetic signal W2′ of water in the mixed solution of ethanol and water, the nuclear magnetic signal W1 of water having the same mass as the water in the mixed solution of ethanol and water, and the nuclear magnetic signal W3 of the mixed solution of heavy water and water having the same mass ratio of water to ethanol as the mixed solution of ethanol and water are obtained; The absolute value integral of the difference between W1, W2′ and W3 is used to quantitatively evaluate the distribution of the nuclear magnetic signals of the three. When the absolute value integral of the difference between W2′ and W1 and W3 is 0, the NMR signal of water in the mixed solution of ethanol and water separated by the time domain analysis method is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical value C.

[0047] As another implementation of this embodiment, in step S5, the critical mass ratio D when the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is most accurately separated by differential spectroscopy is determined, specifically, By using the difference spectrum method, the nuclear magnetic signal W2" of water in the mixed solution of ethanol and water, the nuclear magnetic signal W1 of water with the same mass as the water in the mixed solution of ethanol and water, and the nuclear magnetic signal W3 of the mixed solution of heavy water and water with the same mass ratio of water to ethanol as the mixed solution of ethanol and water are obtained; The absolute value integral of the difference between W1, W2" and W3 was used to quantitatively evaluate the distribution of the nuclear magnetic signals of the three. When the absolute value integral of the difference between W2" and W1 and W3 is 0, the NMR signal of water in the mixed solution of ethanol and water separated by the differential spectrum method is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical value D.

[0048] As an example, the nuclear magnetic resonance test parameters are specifically set as follows: the waiting time TW of the nuclear magnetic resonance test is set to 20000 ms, and the number of echoes NECH is set to a maximum of 18000.

[0049] Example 3 As another preferred embodiment of the present invention, this embodiment proposes an analysis method for nuclear magnetic resonance signals of separated water in a mixed fluid, which can not only meet the nuclear magnetic resonance signal separation requirements for components of similar miscible flows, but also provide a feasibility verification basis for quantitatively analyzing the content and distribution of water in a mixed solution of ethanol and water in a porous medium during the displacement process.

[0050] Five groups of mixed solutions of ethanol, water and heavy water with different mass ratios are designed (as shown in Table 1). The test parameters of the nuclear magnetic resonance test fluid are first set through step S1 to ensure that the fluid is fully relaxed and avoid missing signal acquisition.

[0051] Then, through step S2, using the time domain analysis method ( Figure 1 ) and difference spectrum method ( Figures 7 to 16The NMR signal of water in the ethanol and water mixed solution is obtained by using a 400 nm NMR spectrophotometer (as shown in the figure), and is qualitatively compared with the NMR signals of ethanol in the same mass ratio and the NMR signals of ethanol and heavy water in the same mass ratio. It can be seen that when the mass ratio of ethanol to water in the ethanol and water mixed solution is greater than a certain critical value (critical value A / critical value B), the T2 relaxation time of ethanol separated from the ethanol and water mixed solution coincides with the T2 relaxation time distribution of the ethanol and heavy water solution in the same mass ratio and the ethanol solution in the same mass ratio, that is, the NMR signal separation of ethanol in the ethanol and water mixed solution is most accurate.

[0052] Then according to the above analysis, it can be known that in order to accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water, it is necessary to know the critical value of the mass ratio of water to ethanol when the nuclear magnetic signal of water in a mixed solution of ethanol and water is separated most accurately. When the nuclear magnetic signal of water in a mixed solution of ethanol and water separated by the time domain analysis method is obtained by step S4, when the nuclear magnetic signal of water in a mixed solution of ethanol and water obtained by the time domain analysis method coincides with the nuclear magnetic signal of water in the same mass ratio, the critical mass ratio of water to ethanol in a mixed solution of ethanol and water is 5.23; when the nuclear magnetic signal of water in a mixed solution of ethanol and water obtained by the time domain analysis method coincides with the nuclear magnetic signal of heavy water and water in the same mass ratio, the critical mass ratio of water to ethanol in a mixed solution of ethanol and water is 5.27, and the average value is 5.25.

[0053] When the nuclear magnetic signal of water in the ethanol and water mixed solution separated by the differential spectrum method through step S5 is most accurate, that is, when the nuclear magnetic signal of water in the ethanol and water mixed solution obtained by the differential spectrum method coincides with the nuclear magnetic signal of water in the same mass ratio, the critical mass ratio of water to ethanol in the ethanol and water mixed solution is 7.94; when the nuclear magnetic signal of water in the ethanol and water mixed solution obtained by the differential spectrum method coincides with the nuclear magnetic signals of heavy water and water in the same mass ratio, the critical mass ratio of water to ethanol in the ethanol and water mixed solution is 8.07, and the average value is 8.01.

Claims

1. A method for analyzing nuclear magnetic signals of separated water in a mixed phase fluid, characterized in that: The method comprises the following steps: S1. Setting up an analysis and comparison test group and setting up nuclear magnetic resonance test parameters; the comparison test group includes an ethanol group, a water group, a mixed solution group of ethanol and water, a mixed solution group of ethanol and heavy water, and a mixed solution group of water and heavy water; S2. Separate the NMR signals of ethanol in mixed solutions of ethanol and water in multiple test groups using time domain analysis and differential spectrum method, and compare them with the NMR signals of ethanol of the same mass and the NMR signals of mixed solutions of ethanol and heavy water of the same mass ratio; verify the feasibility of separating the NMR signals of ethanol in mixed solutions using time domain analysis and differential spectrum method; After the verification of steps S3 and S2 is passed, the nuclear magnetic resonance signals of water in the mixed solutions of ethanol and water in multiple test groups are separated by time domain analysis and differential spectrum method respectively; S4, comparing and analyzing the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the time domain analysis method, the nuclear magnetic signal of water of the same mass, and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity, to determine the critical mass ratio C when the nuclear magnetic signal of water in the mixed solution of ethanol and water is most accurately separated by the time domain analysis method; S5. Compare and analyze the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by differential spectroscopy with the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of a mixed solution of water and water of the same mass specific gravity, and determine the critical mass ratio D when the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by differential spectroscopy is most accurate; S6. Compare the critical mass ratio C and the critical mass ratio D, and select the method corresponding to the smaller critical mass ratio to separate the nuclear magnetic resonance signal of water in the mixed solution of ethanol and water.

2. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid as claimed in claim 1, characterized in that: In step S2, the nuclear magnetic signals of ethanol in the mixed solution of ethanol and water in multiple test groups are separated by time domain analysis and differential spectrum method respectively; the nuclear magnetic signals of ethanol separated by time domain analysis and the nuclear magnetic signals of ethanol separated by differential spectrum method are obtained in each test group; the accuracy of the nuclear magnetic signals of ethanol separated by time domain analysis and the nuclear magnetic signals of ethanol separated by differential spectrum method are qualitatively analyzed respectively, and the analysis shows that there is a critical mass ratio A, when the mass ratio of ethanol in the mixed solution of ethanol and water is greater than the critical mass ratio A, the nuclear magnetic signal of ethanol separated by time domain analysis is accurate; there is a critical mass ratio B, when the mass ratio of ethanol in the mixed solution of ethanol and water is greater than the critical mass ratio B, the nuclear magnetic signal of ethanol separated by differential spectrum method is accurate.

3. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid as claimed in claim 1 or 2, characterized in that: In step S4, a comparative analysis is performed between the integral of the absolute value of the difference between the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the time domain analysis method and the nuclear magnetic signal of water of the same mass and the nuclear magnetic signal of water in the mixed solution of water and water of the same mass specific gravity; when the integral of the absolute value of the difference is zero, the nuclear magnetic signal of water in the mixed solution of ethanol and water coincides with the nuclear magnetic signal of water of the same mass or the nuclear magnetic signal of water in the mixed solution of water and water of the same mass specific gravity. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio C when the time domain analysis method is most accurately used to separate the nuclear magnetic signal of water in the mixed solution.

4. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid as claimed in claim 3, characterized in that: In step S5, the integral of the absolute value of the difference between the nuclear magnetic signal of water in the mixed solution of ethanol and water separated by the differential spectrum method and the nuclear magnetic signal of water in the mixed solution of water and water of the same mass specific gravity is compared and analyzed; when the integral of the absolute value of the difference is zero, the nuclear magnetic signal of water in the mixed solution of ethanol and water coincides with the nuclear magnetic signal of water of the same mass, or with the nuclear magnetic signal of water in the mixed solution of water and water of the same mass specific gravity. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical mass ratio D when the nuclear magnetic signal of water in the mixed solution is most accurately separated by the differential spectrum method.

5. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid as claimed in claim 4, characterized in that: In step S6, the critical mass ratio C when the time domain analysis method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water is less than the critical mass ratio D when the difference spectrum method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water, that is, the application scope of the time domain analysis method is wider than that of the difference spectrum method, and the time domain analysis method is suitable for the separation of nuclear magnetic signals of water in a mixed solution of ethanol and water.

6. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid as claimed in claim 5, characterized in that: In step S4, the critical mass ratio C when the time domain analysis method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water is 5.25; in step S5, the critical mass ratio D when the difference spectrum method is used to most accurately separate the nuclear magnetic signal of water in a mixed solution of ethanol and water is 8.

01.

7. The method for analyzing nuclear magnetic signals of separating water in a mixed phase fluid according to claim 1, characterized in that: In step S2, the method of separating the nuclear magnetic signal of ethanol in the mixed solution by time domain analysis is specifically as follows: According to the set NMR test parameters, the NMR signal of the mixed solution of ethanol and water is measured, which is recorded as E2; the NMR signal of water with the same mass as the water in E2 is recorded as E1, and the NMR signal of the mixed solution of ethanol and heavy water with the same mass ratio as E2 is recorded as E3; The attenuation signal of E1 was subtracted from the attenuation signal of E2, and then the T2 relaxation time E2′ of the ethanol in the mixed solution of ethanol and water was inverted using the time domain analysis method. The difference between the relaxation time E3 of the mixed solution of ethanol and heavy water with the same mass ratio and the relaxation time E2″ of the ethanol solution with the same mass ratio was compared.

8. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid according to claim 1, 2 or 7, characterized in that: In step S2, the method of separating the nuclear magnetic signal of ethanol in the mixed solution by differential spectroscopy is specifically as follows: According to the set NMR test parameters, the NMR signal of the mixed solution of Yichunban and water was measured, which was recorded as E2; the NMR signal of water with the same mass as the water in E2 was recorded as E1, and the NMR signal of the mixed solution of ethanol and heavy water with the same mass ratio as E2 was recorded as E3; E1, E2 and E3 were inverted into T2 relaxation time distribution, and then the relaxation time of E1 was subtracted from the relaxation time of E2 using the difference spectrum method to obtain the T2 relaxation time E2' of ethanol in the mixed solution of ethanol and water. The difference between the relaxation time E2' and the relaxation time E3 of the mixed solution of ethanol and heavy water with the same mass ratio and the relaxation time E2" of the ethanol solution with the same mass ratio were compared.

9. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid as claimed in claim 2, characterized in that: In step S2, by performing a qualitative analysis on the nuclear magnetic resonance signal of ethanol in the mixed solution of ethanol and water, it is determined that when the mass proportion of ethanol in the mixed solution of ethanol and water increases, the T2 relaxation time distribution and the nuclear magnetic resonance signal amount of ethanol separated from the mixed solution of ethanol and water show a trend of gradually approaching the T2 relaxation time distribution and the nuclear magnetic resonance signal amount of the mixed solution of ethanol solution with the same mass and the mixed solution of ethanol and heavy water with the same mass ratio.

10. The method for analyzing nuclear magnetic signals of separating water in a mixed phase fluid according to claim 3, characterized in that: In step S4, the critical mass ratio C when the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is most accurately separated by the time domain analysis method is determined, specifically, By using the time domain analysis method, the nuclear magnetic signal W2′ of water in the mixed solution of ethanol and water, the nuclear magnetic signal W1 of water having the same mass as the water in the mixed solution of ethanol and water, and the nuclear magnetic signal W3 of the mixed solution of heavy water and water having the same mass ratio of water to ethanol as the mixed solution of ethanol and water are obtained; The absolute value integral of the difference between W1, W2′ and W3 is used to quantitatively evaluate the distribution of the nuclear magnetic signals of the three. When the absolute value integral of the difference between W2′ and W1 and W2 is 0, the NMR signal of water in the mixed solution of ethanol and water separated by the time domain analysis method is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical value C.

11. The method for analyzing nuclear magnetic signals of separating water in a mixed phase fluid according to claim 4, characterized in that: In step S5, the critical mass ratio D when the nuclear magnetic resonance signal of water in a mixed solution of ethanol and water is most accurately separated by differential spectroscopy is determined, specifically, By using the difference spectrum method, the nuclear magnetic signal W2" of water in the mixed solution of ethanol and water, the nuclear magnetic signal W1 of water with the same mass as the water in the mixed solution of ethanol and water, and the nuclear magnetic signal W3 of the mixed solution of heavy water and water with the same mass ratio of water to ethanol as the mixed solution of ethanol and water are obtained; The absolute value integral of the difference between W1, W2" and W3 was used to quantitatively evaluate the distribution of the nuclear magnetic signals of the three. When the absolute value integral of the difference between W2" and W1 and W2 is 0, the NMR signal of water in the mixed solution of ethanol and water separated by the difference spectrum method is the most accurate. At this time, the mass ratio of water to ethanol in the mixed solution of ethanol and water is the critical value D.

12. The method for analyzing the nuclear magnetic signal of separating water in a mixed phase fluid according to claim 1, 2 or 7, characterized in that: The nuclear magnetic resonance test parameters are specifically set as follows: the waiting time TW of the nuclear magnetic resonance test is set to 20000 ms, and the number of echoes NECH is set to a maximum of 18000.

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