Underground fluid boiling temperature measuring method and system based on rare gas isotope

Abstract

The invention discloses an underground fluid boiling temperature measuring method and system based on rare gas isotopes, and relates to the technical field of geological prospecting, and the method comprises the following steps: S1, collecting a gas phase sample of a high-temperature geothermal fluid; s2, determining the absolute concentration of each rare gas in the gas phase sample by using a rare gas mass spectrometer; S3, correcting the abundance of the rare gas according to the absolute concentration of each rare gas to obtain the corrected vapor phase abundance; and S4, calculating the final underground fluid boiling temperature according to the corrected vapor phase abundance of each rare gas. According to the invention, the inert property of the rare gas is utilized to accurately and reliably measure the boiling temperature of the underground fluid, and an effective technical means is provided for geothermal resource exploration, volcano monitoring and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of geological exploration, and in particular to a method and system for measuring the boiling temperature of underground fluid based on rare gas isotopes. Background Art

[0002] In the field of geoscience, accurate measurement of subsurface fluid temperature is crucial for geothermal resource exploration and development, volcanic activity monitoring, and the study of the chemical evolution of hydrothermal systems. Currently, commonly used methods for measuring subsurface fluid temperature are mostly based on reactive gas chemical equilibrium methods. For example, empirical gas thermometers are established using the concentrations of single reactive gases such as CO2, H2S, and H2, or multi-gas ratios such as CO2-H2 and H2S-H2, as well as reactive and inert gas ratios such as CO2 / Ar and H2 / Ar. These methods are based on the theoretical assumption that the gas content and gas ratios in geothermal fluid emissions are controlled by temperature-dependent gas-gas and mineral-gas equilibria in the reservoir, and that these equilibria are "frozen" during the fluid's ascent to the surface. However, in practical applications, these methods have significant drawbacks. During the ascent of underground fluids, reactive gases are highly susceptible to processes such as steam condensation and boiling, causing changes in gas composition and making it difficult to distinguish between original reservoir conditions and secondary processes. The chemical equilibrium assumption is difficult to meet in many practical scenarios. Changes in temperature, pressure, or redox potential during fluid ascent can trigger kinetically controlled chemical reequilibria, making the calculated temperature inaccurate in reflecting reservoir conditions. Furthermore, air introduced during sampling dilutes the native gas signal, making it difficult for traditional methods to effectively distinguish between native atmospheric components and secondary contamination. Therefore, a more reliable and accurate method for measuring underground fluid temperature is urgently needed. Summary of the Invention

[0003] In order to solve the above problems, the present invention proposes a method and system for measuring the boiling temperature of underground fluids based on rare gas isotopes.

[0004] The technical solution of the present invention is: a method for measuring the boiling temperature of underground fluid based on rare gas isotopes comprises the following steps:

[0005] S1. Collect gas phase samples of high-temperature geothermal fluid;

[0006] S2. determining the absolute concentration of each noble gas in the gas phase sample using a noble gas mass spectrometer;

[0007] S3. Correcting the abundance of the noble gases according to the absolute concentrations of the noble gases to obtain a corrected vapor phase abundance;

[0008] S4. Calculate the final underground fluid boiling temperature based on the corrected vapor phase abundance of each rare gas.

[0009] Further, in S2, the gas phase sample is determined by using a rare gas mass spectrometer. 40 Ar / 36 Ar isotope ratio, and determine 20 Ne, 36 Ar and 84 The absolute concentration of Kr.

[0010] Furthermore, S3 includes the following sub-steps:

[0011] S31. constructing a mixing line model for each noble gas;

[0012] S32. Correct the abundance of the noble gases according to the mixing line models of the noble gases to obtain corrected vapor phase abundance.

[0013] Furthermore, in S31, the expression of the mixing line model of the rare gas is:

[0014] [i] 样品 =f·[i] v +(1-f)·[i] 空气 ;

[0015] Where, [i] 样品 represents the measured concentration of noble gas i in the gas phase sample, [i] v represents the concentration of noble gas i in the virgin vapor phase, [i] 空气 represents the concentration of rare gas i in the air, and f represents the proportion of native vapor phase.

[0016] Furthermore, S4 includes the following sub-steps:

[0017] S41. Calculating the independent temperature of each noble gas based on the corrected vapor phase abundance and gas-liquid phase partition coefficient of each noble gas;

[0018] S42. Calculate the final underground fluid boiling temperature based on the independent temperatures of the respective rare gases.

[0019] Furthermore, in S41, the independent temperature T of the rare gas i The calculation formula is:

[0020]

[0021] Where, [i] ASW represents the initial abundance of air-saturated water, represents the vapor phase abundance after correction for noble gases, It represents the gas-liquid partition coefficient of the noble gas i at temperature T.

[0022] Furthermore, in S42, the final calculation formula for the underground fluid boiling temperature T is:

[0023]

[0024] Where, T Ne express 20 Independent temperature of Ne, T Ar express 36 Ar independent temperature, T Kr express 84 Kr is independent of temperature, σ Ne express 20 Measurement accuracy of Ne, σ Ar express 36 Measurement accuracy of Ar, σ Kr express 84 Measurement accuracy of Kr.

[0025] The beneficial effects of the present invention are:

[0026] (1) The method for measuring the boiling temperature of underground fluids of the present invention has a strong anti-interference ability: rare gases have inert properties and are not affected by complex underground chemical reactions, mineral precipitation and other processes. They can directly reflect the physical fractionation temperature. Compared with traditional thermometers based on reactive gases, the method has stronger adaptability in complex geothermal environments (such as acidic fluids and areas with high CO2 concentrations) and can effectively avoid the interference of chemical reaction uncertainties on temperature measurement.

[0027] (2) The method for measuring the boiling temperature of underground fluids of the present invention has high measurement accuracy: through the multi-rare gas collaborative correction technology, the 20 Ne, 36 Ar and 84 The mixing line model constructed by using three rare gases, Kr, can accurately deduct secondary atmospheric pollution and control the atmospheric pollution correction error within ±5°C. The temperature calculation method with multi-element collaborative verification further improves the measurement accuracy, allowing the temperature error to be controlled within ±10°C, which is significantly better than the ±30°C error range of traditional methods.

[0028] (3) The method for measuring the boiling temperature of underground fluids of the present invention has a wide range of applications: the present invention does not rely on the chemical equilibrium hypothesis and can directly track the physical fractionation process. It is applicable to transient fluids (such as supercritical fluids before volcanic eruptions) and non-equilibrium fluids that are difficult to measure by traditional methods. It can provide more comprehensive and accurate temperature data support for geothermal resource exploration and development and volcanic activity monitoring, and has important application value, especially under complex geological conditions (such as plate boundary zones and mantle plume activity areas).

[0029] (4) The data reliability of the underground fluid boiling temperature determination method of the present invention is high: by comparing and verifying with the results of traditional thermometers, the rationality and reliability of the temperature determination of the present invention are ensured. At the same time, the multi-element mutual verification method reduces the impact of single element measurement errors on the results, thereby improving the credibility of the data.

[0030] Based on the above method, the present invention also proposes a system for measuring the boiling temperature of underground fluids based on rare gas isotopes, which includes a sample collection module, a rare gas measurement module, an atmospheric pollution correction module, and a temperature calculation module;

[0031] The sample collection module is used to collect gas phase samples of high-temperature geothermal fluids;

[0032] The rare gas measurement module is used to determine the absolute concentration of each rare gas in the gas phase sample;

[0033] The atmospheric pollution correction module is used to correct the abundance of rare gases according to the absolute concentration of each rare gas to obtain the corrected vapor phase abundance;

[0034] The temperature calculation module is used to calculate the final underground fluid boiling temperature based on the corrected vapor phase abundance of each rare gas.

[0035] The beneficial effects of the present invention are as follows: the underground fluid boiling temperature measurement system of the present invention utilizes the inert properties of rare gases to achieve accurate and reliable measurement of the underground fluid boiling temperature, providing an effective technical means for geothermal resource exploration and volcano monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of a method for determining the boiling temperature of underground fluids based on noble gas isotopes;

[0037] Figure 2 This is a schematic diagram of the structure of the underground fluid boiling temperature measurement system based on rare gas isotopes;

[0038] Figure 3 A comparison diagram of the noble gas isotope (He) source and the air side (Air);

[0039] Figure 4 This is the relationship between the ratio of atmospheric rare gases and fractionation;

[0040] Figure 5 It is a statistical diagram of the expected maximum fractionation line of gas and liquid phases;

[0041] Figure 6 This is the temperature correction diagram for gas phase fractionation mixed with air. DETAILED DESCRIPTION

[0042] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0043] like Figure 1 As shown, the present invention provides a method for measuring the boiling temperature of underground fluid based on rare gas isotopes, comprising the following steps:

[0044] S1. Collect gas phase samples of high-temperature geothermal fluid;

[0045] S2. determining the absolute concentration of each noble gas in the gas phase sample using a noble gas mass spectrometer;

[0046] S3. Correcting the abundance of the noble gases according to the absolute concentrations of the noble gases to obtain a corrected vapor phase abundance;

[0047] S4. Calculate the final underground fluid boiling temperature based on the corrected vapor phase abundance of each rare gas.

[0048] In S1, for high-temperature geothermal fluids, gas phase samples are collected first, such as steam phase samples collected from geothermal boreholes or natural exhaust fumaroles.

[0049] Sampling requirements: Use metal containers with good airtightness for sampling. Before sampling, fully purge the container with steam to remove the air inside to ensure that the collected samples can truly represent the original fractionation state of the underground and avoid the samples from being contaminated by the atmosphere during the collection process.

[0050] In the embodiment of the present invention, in S2, a rare gas mass spectrometer is used to determine the gas phase sample 40 Ar / 36 Ar isotope ratio, and determine 20 Ne, 36 Ar and 84 The absolute concentration of Kr.

[0051] 20 Ne, 36 Ar and 84 The concentration of Kr is used for subsequent temperature calculations. 40 Ar / 36 Ar isotope ratios can be used to identify mantle-derived argon and help determine whether the sample is affected by mantle fluid.

[0052] In this embodiment of the present invention, S3 includes the following sub-steps:

[0053] S31. constructing a mixing line model for each noble gas;

[0054] S32. Correct the abundance of the noble gases according to the mixing line models of the noble gases to obtain corrected vapor phase abundance.

[0055] Through the joint20 Ne, 36 Ar and 84 The mixture equation of the three rare gases Kr is solved to obtain the corrected vapor phase abundance This can deduct the impact of secondary air pollution on the sample and obtain more accurate information on the concentration of rare gas in the original vapor phase.

[0056] In the embodiment of the present invention, in S31, it is assumed that the collected sample is a mixture of a primary vapor phase (with a proportion of f) and a secondary air phase (with a proportion of 1-f). The expression of the mixing line model of the noble gas is:

[0057] [i] 样品 =f·[i] v +(1-f)·[i] 空气 ;

[0058] Where, [i] 样品 represents the measured concentration of noble gas i in the gas phase sample, [i] v represents the concentration of noble gas i in the virgin vapor phase, [i] 空气 represents the concentration of rare gas i in the air, and f represents the proportion of native vapor phase.

[0059] In this embodiment of the present invention, S4 includes the following sub-steps:

[0060] S41. Calculating the independent temperature of each noble gas based on the corrected vapor phase abundance and gas-liquid phase partition coefficient of each noble gas;

[0061] S42. Calculate the final underground fluid boiling temperature based on the independent temperatures of the respective rare gases.

[0062] In the embodiment of the present invention, in S41, the independent temperature T of the rare gas i The calculation formula is:

[0063]

[0064] Where, [i] ASW represents the initial abundance of air-saturated water, represents the vapor phase abundance after correction for noble gases, It represents the gas-liquid partition coefficient of rare gas i at temperature T. This coefficient can be obtained through experimental data and theoretical calculations and is a function of temperature.

[0065] In the embodiment of the present invention, in S42, 20 Ne, 36 Ar and 84 Independent temperature calculation result T of Kr Ne 、T Ar and TKr A comprehensive analysis is performed, and the inverse of the measurement accuracy of each element is used as a weight to calculate the weighted average, which is used as the final underground fluid boiling temperature T. This multi-element collaborative verification method can effectively improve the accuracy and reliability of temperature calculations and reduce the impact of single element measurement errors on the results. The final calculation formula for the underground fluid boiling temperature T is:

[0066]

[0067] Where, T Ne express 20 Independent temperature of Ne, T Ar express 36 Ar independent temperature, T Kr express 84 Kr is independent of temperature, σ Ne express 20 Measurement accuracy of Ne, σ Ar express 36 Measurement accuracy of Ar, σ Kr express 84 Measurement accuracy of Kr.

[0068] Based on the above methods, such as Figure 2 As shown, the present invention also proposes a system for measuring the boiling temperature of underground fluids based on rare gas isotopes, comprising a sample collection module, a rare gas measurement module, an atmospheric pollution correction module, and a temperature calculation module;

[0069] The sample collection module is used to collect gas phase samples of high-temperature geothermal fluids;

[0070] The rare gas measurement module is used to determine the absolute concentration of each rare gas in the gas phase sample;

[0071] The atmospheric pollution correction module is used to correct the abundance of rare gases according to the absolute concentration of each rare gas to obtain the corrected vapor phase abundance;

[0072] The temperature calculation module is used to calculate the final underground fluid boiling temperature based on the corrected vapor phase abundance of each rare gas.

[0073] In the embodiment of the present invention, Figure 3 As shown, by plotting the measured helium isotope ratios against 4 He / 20 The relationship diagram of Ne can be used to determine the degree of atmospheric contamination in the sample and to correct the helium isotope ratio. In this method, although helium isotopes are mainly used to determine the contribution of mantle sources, the accurate 4 He / 20 The Ne ratio helps to make atmospheric pollution correction more accurately and provides a basis for the subsequent accurate determination of rare gas concentrations.

[0074] like Figure 4 As shown, the atmospheric origin of noble gas isotopes ( 20 Ne, 36 Ar and 84 The relationship between the abundance of Kr) and the end-member composition of air and air saturated water (ASW), as well as the predicted vapor phase abundance curve at different temperatures. It can be seen intuitively from the figure that 20 Ne, 36 Ar and 84 The abundance data of Kr fits well with the predicted vapor phase abundance curve in the temperature range of 200-340℃, indicating that the abundance of these rare gases is mainly controlled by the temperature of gas-liquid phase distribution, and preliminarily shows that the boiling temperature of underground fluids sampled at different locations is concentrated in the range of 200-340℃, providing a theoretical basis for using it for temperature inversion.

[0075] like Figure 5 As shown, the element ratios of rare gases from atmospheric sources are presented (such as 84 Kr / 36 Ar and 20 Ne / 36 Ar, 84 Kr / 36 Ar and 130 Xe / 36 The relationship between the sample and the expected fractionation curve can be further judged by this figure. Whether the sample is contaminated by air and the influence of the gas-liquid phase distribution process on the ratio of rare gas elements can be further judged. If the sample data point deviates from the expected fractionation curve and is close to the air end element, it indicates that the sample may be contaminated by air and atmospheric pollution correction is required. At the same time, the figure also shows the difference in fractionation between liquid and gas phase samples, which supports the method's 20 Ne, 36 Ar and 84 The assumption that Kr distribution is mainly controlled by gas-liquid phase partitioning.

[0076] like Figure 6 As shown, by drawing 1 / 36 Ar and 84 Kr / 36 Ar, 20 Ne / 36 The Ar relationship diagram shows the relationship between the noble gas abundance in the sample and the expected vapor phase fractionation line and air values. The black dashed line in the figure represents the mixing line of the sample and pure atmospheric components. By extrapolating the intersection of this mixing line with the vapor phase fractionation line, the temperature after accounting for air contamination correction can be calculated, intuitively demonstrating the process and principle of atmospheric contamination correction.

[0077] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. A method for measuring the boiling temperature of underground fluids based on noble gas isotopes, characterized in that: The following steps are involved: S1. Collect gas phase samples of high-temperature geothermal fluid; S2. determining the absolute concentration of each noble gas in the gas phase sample using a noble gas mass spectrometer; S3. Correcting the abundance of the noble gases according to the absolute concentrations of the noble gases to obtain a corrected vapor phase abundance; S4. Calculate the final underground fluid boiling temperature based on the corrected vapor phase abundance of each rare gas.

2. The method for measuring the boiling temperature of underground fluids based on noble gas isotopes according to claim 1, characterized in that: In said S2, the gas phase sample is determined by using a rare gas mass spectrometer. 40 Ar / 36 Ar isotope ratio, and determine 20 Ne, 36 Ar and 84 The absolute concentration of Kr.

3. The method for measuring the boiling temperature of underground fluids based on noble gas isotopes according to claim 1, characterized in that: The S3 includes the following sub-steps: S31. constructing a mixing line model for each noble gas; S32. Correct the abundance of the noble gases according to the mixing line models of the noble gases to obtain corrected vapor phase abundance.

4. The method for measuring the boiling temperature of underground fluids based on noble gas isotopes according to claim 3, characterized in that: In S31, the expression of the mixing line model of the rare gas is: [i] 样品 =f·[i] v +(1-f)·[i] 空气 ; Where, [i] 样品 represents the measured concentration of noble gas i in the gas phase sample, [i] v represents the concentration of noble gas i in the virgin vapor phase, [i] 空气 represents the concentration of rare gas i in the air, and f represents the proportion of native vapor phase.

5. The method for measuring the boiling temperature of underground fluids based on noble gas isotopes according to claim 1, characterized in that: The S4 includes the following sub-steps: S41. Calculating the independent temperature of each noble gas based on the corrected vapor phase abundance and gas-liquid phase partition coefficient of each noble gas; S42. Calculate the final underground fluid boiling temperature based on the independent temperatures of the respective rare gases.

6. The method for measuring the boiling temperature of underground fluids based on noble gas isotopes according to claim 5, characterized in that: In the above S41, the independent temperature T of the rare gas i The calculation formula is: Where, [i] ASW represents the initial abundance of air-saturated water, represents the vapor phase abundance after correction for noble gases, It represents the gas-liquid partition coefficient of the noble gas i at temperature T.

7. The method for measuring the boiling temperature of underground fluids based on noble gas isotopes according to claim 5, characterized in that: In S42, the calculation formula for the final underground fluid boiling temperature T is: Where, T Ne express 20 Independent temperature of Ne, T Ar express 36 Ar independent temperature, T Kr express 84 Kr's independent temperature, σ Ne express 20 Measurement accuracy of Ne, σ Ar express 36 Measurement accuracy of Ar, σ Kr express 84 Measurement accuracy of Kr.

8. A system for measuring the boiling temperature of underground fluids based on noble gas isotopes, characterized in that: It includes sample collection module, rare gas measurement module, atmospheric pollution correction module and temperature calculation module; The sample collection module is used to collect gas phase samples of high-temperature geothermal fluid; The rare gas measurement module is used to determine the absolute concentration of each rare gas in the gas phase sample; The atmospheric pollution correction module is used to correct the abundance of the rare gases according to the absolute concentration of each rare gas to obtain the corrected vapor phase abundance; The temperature calculation module is used to calculate the final underground fluid boiling temperature according to the corrected vapor phase abundance of each rare gas.

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