Method and system for determining existence state of shale gas and storage medium

Abstract

The invention discloses a method and system for determining the existence state of shale gas and a storage medium, and the method comprises the steps: collecting a core rock sample of a reservoir in which to-be-researched shale gas is located, and carrying out rock mass gas content analysis on the core rock sample to obtain the total analysis gas content at different metering moments; performing methane carbon isotope testing on the analytic gas obtained at different analytic sampling moments so as to obtain corresponding methane carbon isotope data; and calculating the proportion of the total analytic gas volume in the analyzed total gas content at different metering moments, and analyzing the correlation between the methane carbon isotope data and the analytic gas volume proportion, so as to obtain the existence state of the shale gas to be researched according to the analysis result. According to the invention, the content of the free gas and the adsorbed gas in the shale gas well can be accurately obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of petroleum, geology and mining exploration and development, and in particular relates to a method, system and storage medium for determining the existence status of shale gas. Background Art

[0002] Shale gas refers to natural gas that is found in organic-rich shale and its interlayered muddy siltstone. It is mainly a continuous gas reservoir that is self-generated and self-stored. It is an accumulation of natural gas stored in a dense shale formation system in an adsorbed and free state. It is an unconventional natural gas. Shale gas resources are abundant and have broad development prospects. Good exploration and development benefits have been achieved in many different regions. It is currently a hot spot for unconventional natural gas exploration and development. Among them, great achievements have been made in shale gas research in the Sichuan Basin and surrounding areas. At the same time, a series of major breakthroughs have been made in shale gas exploration.

[0003] A shale gas content assessment method based on methane carbon isotopes in the prior art estimates relevant parameters by matching calculation and experimental results, and uses the change of methane carbon isotope values ​​during shale gas degassing to establish a corresponding relationship with the percentage of free gas and adsorbed gas in the degassing process, so as to calculate the total gas volume. This method can calculate the lost gas volume, desorbed gas volume and residual gas volume on the one hand, and the free gas volume and adsorbed gas volume on the other hand. At the same time, the isotope fractionation of the invention can calculate the lost gas, desorbed gas and residual gas on the one hand; and can calculate the free gas and adsorbed gas on the other hand. In addition, the prior art is also based on the gray correlation method, and on the basis of comprehensively considering the relationship between shale adsorption and temperature, pressure, organic carbon content, quartz and clay mineral content, it dynamically corrects key parameters such as Langmuir volume and Langmuir pressure, and establishes a new model for calculating adsorbed gas and free gas content. Although the aforementioned prior art has realized the assessment of shale gas content, the assessment process is relatively complicated.

[0004] In addition, the current judgment of the free gas and adsorbed gas content in shale gas mainly relies on logging data. For the judgment of free gas content, the more commonly used method is to calculate it through the porosity and gas saturation in the logging data. For adsorbed gas, a large number of isothermal adsorption experimental data show that the amount of adsorbed gas in shale often shows a good positive correlation with the shale organic carbon content (TOC). Therefore, the adsorbed gas content in the prior art is mainly obtained by fitting and calculating the shale TOC data in geochemical logging. In other words, the prior art studies the content and percentage of free gas and adsorbed gas in shale gas based on the key parameter of shale organic carbon content. However, this study is mainly based on the Langmuir volume model of methane isothermal adsorption, and the free gas and adsorbed gas content are quantitatively calculated by correcting temperature and pressure, or the occurrence mode of shale gas is studied based on the carbon isotope fractionation phenomenon. The research methods are relatively complicated and the calculation amount is slightly large.

[0005] Quantitative evaluation of the free gas and adsorbed gas content in shale reservoirs is the basis for achieving efficient exploration and development of shale gas. Therefore, improving the efficiency of quantitative evaluation of the free gas and adsorbed gas content in shale reservoirs, as well as improving the accuracy of quantitative evaluation, can effectively achieve the goal of efficient exploration and development of shale gas. Summary of the invention

[0006] In order to solve the above problems, an embodiment of the present invention provides a method for determining the existence status of shale gas, including: collecting core samples of the reservoir where the shale gas to be studied is located, and analyzing the gas content of the rock mass to obtain the total analyzed gas volume at different metering times; performing methane carbon isotope testing on the analyzed gas obtained at different analysis sampling times, so as to obtain corresponding methane carbon isotope data; calculating the ratio of the total analyzed gas volume at the different metering times to the total analyzed gas content, and analyzing the correlation between the methane carbon isotope data and the analyzed gas volume ratio, so as to obtain the existence status of the shale gas to be studied according to the analysis results.

[0007] Preferably, the time interval between each adjacent metering moment is 30 seconds; and the time interval between each adjacent analytical sampling moment is 60 minutes.

[0008] Preferably, before performing methane carbon isotope testing on the analyzed gases obtained at different analyzed sampling times, the method further comprises: collecting the analyzed gases obtained at different analyzed sampling times by using a saturated brine drainage method.

[0009] Preferably, the step of analyzing the correlation between the methane carbon isotope data and the analyzed gas volume ratio includes: performing nonlinear fitting on the methane carbon isotope data and the analyzed gas volume ratio in a rectangular coordinate system, thereby using the current fitting relationship curve to characterize the correlation.

[0010] Preferably, the current correlation is represented by an exponential function, wherein the base of the exponential function is a natural constant, the methane carbon isotope data represents the independent variable index of the exponential function, and the analyzed gas volume ratio represents the dependent variable of the exponential function.

[0011] Preferably, in the step of obtaining the existence state of the shale gas to be studied according to the analysis results, it includes: recording the data point on the current fitting relationship curve at the end time of the analysis as the first point, and recording the data point at the initial time of the analysis as the second point, so as to form a first straight line after connecting the first point and the second point; making a tangent to the current fitting relationship curve with the first point as the tangent point, and making a first perpendicular line perpendicular to the x-axis through the second point, and then making a second perpendicular line on the first straight line, wherein the second perpendicular line passes through the intersection of the tangent and the first perpendicular line; according to the intersection of the second perpendicular line and the current fitting relationship curve, obtaining the free gas content in the shale gas to be studied, and then obtaining the adsorbed gas content in the shale gas to be studied according to the free gas content.

[0012] Preferably, the step of analyzing the gas content of the core sample includes: during the analysis process, the core sample is located in a closed cavity inside a desorption tank, wherein the ambient temperature of the area where the desorption tank is located is the same as the formation temperature of the reservoir where the shale gas to be studied is located.

[0013] Preferably, the step of collecting core samples of the reservoir where the shale gas to be studied is located includes: collecting the core samples using a closed coring process, thereby preventing the core samples from being contaminated by drilling fluid.

[0014] The present invention also provides a computer-readable storage medium comprising a series of instructions for executing method steps for determining the presence status of shale gas.

[0015] On the other hand, the present invention also provides a system for determining the existence status of shale gas, the system comprising the following modules: an analyzed gas volume metering module, which is used to collect core rock samples from the reservoir where the shale gas to be studied is located, and analyze the gas content of the rock mass to obtain the total analyzed gas volume at different metering times; a carbon isotope testing module, which is used to perform methane carbon isotope testing on the analyzed gas obtained at different analysis sampling times, so as to obtain corresponding methane carbon isotope data; an existence status generation module, which is used to calculate the ratio of the total analyzed gas volume at the different metering times to the total analyzed gas content, and analyze the correlation between the methane carbon isotope data and the analyzed gas volume ratio, so as to obtain the existence status of the shale gas to be studied according to the analysis results.

[0016] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0017] The present invention proposes a method, system and storage medium for determining the existence status of shale gas. The method first collects core samples in the reservoir where the shale gas to be studied is located, and analyzes the rock gas content of the collected core samples to obtain the total analyzed gas volume data analyzed at different metering times, and the analysis results of the analyzed gas samples at different analysis sampling times. Afterwards, by performing a methane carbon isotope test on the analyzed gas samples, methane carbon isotope data is obtained, and the ratio of the total analyzed gas volume at different metering times to the analyzed total gas content is calculated, and the correlation between the methane carbon isotope data and the analyzed gas volume ratio is further obtained, so as to determine the existence status of the current shale gas to be studied based on the correlation. Different from the conventional method ideas, the present invention realizes the rapid and accurate acquisition of the percentage of free gas and adsorbed gas in shale gas wells.

[0018] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 This is a step diagram of a method for determining the existence status of shale gas according to an embodiment of the present application.

[0021] Figure 2 An example diagram of the correlation of the method for determining the existence status of shale gas in an embodiment of the present application.

[0022] Figure 3 This is a module block diagram of a system for determining the existence status of shale gas according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0024] In addition, the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be performed in an order different from that shown here.

[0025] Shale gas refers to natural gas that is found in organic-rich shale and its interlayered muddy siltstone. It is mainly a continuous gas reservoir that is self-generated and self-stored. It is an accumulation of natural gas stored in a dense shale formation system in an adsorbed and free state. It is an unconventional natural gas. Shale gas resources are abundant and have broad development prospects. Good exploration and development benefits have been achieved in many different regions. It is currently a hot spot for unconventional natural gas exploration and development. Among them, great achievements have been made in shale gas research in the Sichuan Basin and surrounding areas. At the same time, a series of major breakthroughs have been made in shale gas exploration.

[0026] A shale gas content assessment method based on methane carbon isotopes in the prior art estimates relevant parameters by matching calculation and experimental results, and uses the change of methane carbon isotope values ​​during shale gas degassing to establish a corresponding relationship with the percentage of free gas and adsorbed gas in the degassing process, so as to calculate the total gas volume. This method can calculate the lost gas volume, desorbed gas volume and residual gas volume on the one hand, and the free gas volume and adsorbed gas volume on the other hand. At the same time, the isotope fractionation of the invention can calculate the lost gas, desorbed gas and residual gas on the one hand; and can calculate the free gas and adsorbed gas on the other hand. In addition, the prior art is also based on the gray correlation method, and on the basis of comprehensively considering the relationship between shale adsorption and temperature, pressure, organic carbon content, quartz and clay mineral content, it dynamically corrects key parameters such as Langmuir volume and Langmuir pressure, and establishes a new model for calculating adsorbed gas and free gas content. Although the aforementioned prior art has realized the assessment of shale gas content, the assessment process is relatively complicated.

[0027] In addition, the current judgment of the free gas and adsorbed gas content in shale gas mainly relies on logging data. For the judgment of free gas content, the more commonly used method is to calculate it through the porosity and gas saturation in the logging data. For adsorbed gas, a large number of isothermal adsorption experimental data show that the amount of adsorbed gas in shale often shows a good positive correlation with the shale organic carbon content (TOC). Therefore, the adsorbed gas content in the prior art is mainly obtained by fitting and calculating the shale TOC data in geochemical logging. In other words, the prior art studies the content and percentage of free gas and adsorbed gas in shale gas based on the key parameter of shale organic carbon content. However, this study is mainly based on the Langmuir volume model of methane isothermal adsorption, and the free gas and adsorbed gas content are quantitatively calculated by correcting temperature and pressure, or the occurrence mode of shale gas is studied based on the carbon isotope fractionation phenomenon. The research methods are relatively complicated and the calculation amount is slightly large.

[0028] Quantitative evaluation of the free gas and adsorbed gas content in shale reservoirs is the basis for achieving efficient exploration and development of shale gas. Therefore, improving the efficiency of quantitative evaluation of the free gas and adsorbed gas content in shale reservoirs, as well as improving the accuracy of quantitative evaluation, can effectively achieve the goal of efficient exploration and development of shale gas.

[0029] Therefore, in order to solve the above problems, the embodiment of the present invention proposes a method, system and storage medium for determining the existence state of shale gas. The method first collects core samples in the reservoir where the shale gas to be studied is located, and analyzes the rock gas content of the collected core samples to obtain the total analyzed gas volume data analyzed at different metering times, and the analysis results of the analyzed gas samples at different analysis sampling times. After that, by testing the analyzed gas samples with methane carbon isotopes, methane carbon isotope data is obtained, and the ratio of the total analyzed gas volume at different metering times to the analyzed total gas content is calculated, and the correlation between the methane carbon isotope data and the analyzed gas volume ratio is further obtained, so as to determine the existence state of the current shale gas to be studied according to the correlation. Different from the conventional method, the present invention measures the percentage of free gas and adsorbed gas in shale gas based on the methane carbon isotope fractionation effect, realizes the rapid and accurate acquisition of the percentage of free gas and adsorbed gas in shale gas wells, and provides technical support for shale gas exploration and development.

[0030] Embodiment 1

[0031] Figure 1 This is a step diagram of a method for determining the presence of shale gas in an embodiment of the present application. Figure 1 To illustrate the various steps of this method.

[0032] like Figure 1As shown, in step S110, a core sample of the reservoir where the shale gas to be studied is collected, and the gas content of the rock mass is analyzed to obtain the total analyzed gas volume at different metering times. The present invention analyzes the existence state of shale gas in the reservoir based on the gas-containing state of the core of the reservoir where the shale gas is located. In an embodiment of the present application, first, a core sample is collected in a shale gas coring well of the reservoir where the shale gas to be studied is located, so as to obtain the existence state of the shale gas to be studied by using the gas-containing state of the core sample currently collected. Then, the collected core sample is subjected to rock gas content analysis, and a plurality of different metering times are preset to measure the total analyzed gas volume from the initial stage of the analysis to each metering time. Since the analysis results of the core sample are continuously generated as the analysis process advances, the total analyzed gas volume at each preset metering time in the analysis result is extracted in real time during the analysis process in this embodiment, thereby obtaining the total analyzed gas volume at different metering times.

[0033] Furthermore, in the step of collecting core samples from the reservoir where the shale gas to be studied is located, a closed coring process is used to collect the core samples, thereby preventing the core samples from being contaminated by drilling fluid. Closed coring refers to a special drilling coring process that enables the core obtained in water-based drilling fluid to be basically free from the contamination of drilling fluid, can truly reproduce the original geological porosity, oil saturation, water invasion and water content of the formation, and is based on the joint action of a special closed coring tool and a closed fluid. Accordingly, this embodiment uses a closed coring process to collect core samples from the reservoir where the shale gas to be studied is located, effectively preventing the core samples from being contaminated by drilling fluid, greatly improving the accuracy of the analysis results, and thereby making the determined existence status of the shale gas to be studied more accurate.

[0034] In the step of analyzing the gas content of the rock mass of the core sample, during the analysis process, the core sample is located in a closed cavity inside the desorption tank, wherein the ambient temperature of the area where the desorption tank is located is the same as the formation temperature of the reservoir where the shale gas to be studied is located. In an embodiment of the present application, after the core sample in the well is collected, the collected core sample is moved from the well to the wellhead position, and then when it reaches the wellhead, it is immediately taken out and placed in the closed cavity inside the desorption tank for analysis. During the analysis process, the ambient temperature of the area where the desorption tank is located is kept the same as the formation temperature of the reservoir where the shale gas to be studied is located, so as to obtain an accurate rock gas content analysis result that is not affected by the external environment and can truly reflect the gas-containing state of the reservoir where the shale gas to be studied is located.

[0035] Further, in step S120, the methane carbon isotope test is performed on the analyzed gas obtained at different analysis sampling times, so as to obtain corresponding methane carbon isotope data. Specifically, the present embodiment also presets a plurality of different analysis sampling times to sample the analyzed gas generated during the analysis process. Based on the characteristic that the analysis results of the core samples are continuously generated as the analysis process progresses, the present embodiment also collects the analyzed gas generated at each preset analysis sampling time in the analysis results in real time during the analysis process, and obtains the analyzed gas at different analysis sampling times. Next, the methane carbon isotope test is performed on the analyzed gas obtained at each analysis sampling time, and the methane carbon isotope data of the analyzed gas at each analysis sampling time is obtained.

[0036] In a specific embodiment of the present application, the time interval between each adjacent metering moment is preferably 30 seconds; and the time interval between each adjacent analytical sampling moment is 60 minutes. It should be noted that the present invention does not specifically limit the time interval between each adjacent metering moment and the time interval between each adjacent analytical sampling moment, and those skilled in the art can set them according to the actual accuracy of the shale gas existence status to be obtained.

[0037] Before performing methane carbon isotope testing on the analyzed gas obtained at different analytical sampling times, this embodiment uses the saturated salt water drainage method to collect the analyzed gas obtained at different analytical sampling times. In practical applications, although the main components of shale gas are alkanes, it also contains a small amount of non-alkane substances. Accordingly, this embodiment uses the saturated salt water drainage method to collect the analyzed gas obtained at each analytical sampling time, avoiding the loss of substances in the analyzed gas that can be dissolved in pure water and react with pure water, and maximizing the comprehensive collection of analyzed gas, thereby improving the accuracy of the results of determining the existence status of shale gas.

[0038] In step S130, the ratio of the total analyzed gas volume at different metering moments to the total analyzed gas content is calculated, and the correlation between the methane carbon isotope data and the analyzed gas volume ratio is analyzed, so as to obtain the existence state of the shale gas to be studied according to the analysis results. In the embodiment of the present application, after the analysis process is completed, the total gas content analyzed from the current core sample is determined according to the total analyzed gas volume at the analysis termination time, and then the total gas content is used, combined with the total analyzed gas volume at each metering moment, to calculate the ratio of the total analyzed gas volume at different metering moments to the total analyzed gas content. Next, the correlation between the methane carbon isotope data and the analyzed gas volume ratio at the same moment is used to determine the correlation between the two, so as to obtain the existence state of the shale gas to be studied according to the correlation.

[0039] In the step of analyzing the correlation between the methane carbon isotope data and the analyzed gas volume ratio, the methane carbon isotope data and the analyzed gas volume ratio are nonlinearly fitted in the rectangular coordinate system, so as to characterize the correlation using the current fitting relationship curve. Specifically, the methane carbon isotope data is used as the x-axis data, and the analyzed gas volume ratio is used as the y-axis data, and the data points of the methane carbon isotope data and the analyzed gas volume ratio belonging to the corresponding coordinate axis and at the same time are mapped to the rectangular coordinate system, and the smooth curve is used to sequentially connect the data points, so as to obtain the following: Figure 2 The nonlinear fitting relationship curve ( Figure 2 1 is an example diagram of the correlation of the method for determining the existence state of shale gas in the embodiment of the present application). Before mapping the analyzed gas volume ratio to the rectangular coordinate system, it is first converted into data in percentage form to facilitate the subsequent calculation of the percentage of adsorbed gas and free gas in the shale gas. Figure 2 The nonlinear fitting relationship curve shown is fitted using the methane carbon isotope data shown in Table 1 and the corresponding data in the statistical table of analyzed gas volume ratios:

[0040] Table 1 Methane carbon isotope data and analyzed gas volume statistics

[0041] Serial number <![CDATA[Methane carbon isotope (δ 13 CPDB (‰))]]> Percentage of analyzed gas volume to total gas volume (%) 1 -31.80 3.70 2 -31.40 12.46 3 -31.00 20.48 4 -30.40 27.95 5 -30.00 33.39 6 -29.10 40.88 7 -28.60 46.59 8 -27.40 53.02 9 -23.50 70.23 10 -19.60 81.92 11 -15.30 88.80 12 -12.00 93.37 13 -9.20 96.27 14 -5.00 99.10

[0042] Further, the current correlation is represented by an exponential function. In the embodiment of the present application, based on the fitted nonlinear fitting relationship curve, it is determined that there is an exponential relationship between the methane carbon isotope data and the analytical gas volume ratio (i.e., the resolution rate), so the present embodiment uses an exponential function to represent the current correlation. Among them, the base of the exponential function is the natural constant e, the methane carbon isotope data represents the independent variable index of the exponential function, and the analytical gas volume ratio represents the dependent variable of the exponential function.

[0043] In the step of obtaining the existence state of the shale gas to be studied according to the analysis results, first, the data point on the current fitting relationship curve at the end time of the analysis is recorded as the first point, and the data point at the initial time of the analysis is recorded as the second point, so that the first point and the second point are connected to form a first straight line; then, a tangent line of the current fitting relationship curve is made with the first point as the tangent point, and a first perpendicular line perpendicular to the x-axis is made through the second point, and then a second perpendicular line is made on the first straight line, wherein the second perpendicular line passes through the intersection of the tangent line and the first perpendicular line; finally, according to the intersection of the second perpendicular line and the current fitting relationship curve, the free gas content in the shale gas to be studied is obtained, and then the adsorbed gas content in the shale gas to be studied is obtained according to the free gas content.

[0044] Continue to refer to Figure 2In a specific embodiment of the present application, the data point on the current fitting relationship curve at the end of the analysis is recorded as the first point (point A), and the data point at the initial time of the analysis is recorded as the second point (point C). Then, the first point (point A) and the second point (point C) are connected to form a first straight line L3. Next, the tangent L1 of the current fitting relationship curve is made with the first point (point A) as the tangent point, and the first vertical line L2 perpendicular to the x-axis is made through the second point (point C), and then the second vertical line L4 perpendicular to the first straight line L3 is made on the first straight line L3, wherein the second vertical line L4 passes through the intersection of the tangent L1 and the first vertical line L2. Afterwards, the intersection of the second vertical line L4 and the current fitting relationship curve is recorded as point B, and a third straight line L5 perpendicular to the y-axis is made through point B. Accordingly, the intersection of the third straight line L5 and the y-axis is recorded as point E, and the y-axis value corresponding to point E is the percentage of free gas content in the current shale gas to be studied. The shale gas to be studied is mainly composed of free gas and adsorbed gas, so the adsorbed gas content percentage can be obtained by using the current free gas content percentage. In a specific embodiment of the present application, the free gas content percentage is about 75%, from which the corresponding adsorbed gas content percentage can be obtained to be about 25%.

[0045] Embodiment 2

[0046] Based on the method for determining the existence status of shale gas described in the first embodiment above, an embodiment of the present invention further provides a system for determining the existence status of shale gas. Figure 3 This is a module block diagram of a system for determining the existence status of shale gas according to an embodiment of the present application.

[0047] like Figure 3 As shown, the system for determining the existence status of shale gas in the embodiment of the present invention includes: an analyzed gas volume metering module 31, a carbon isotope testing module 32 and an existence status generating module 33. Specifically, the analyzed gas volume metering module 31 is implemented according to the method described in the above step S110, and is configured to analyze the gas content of the rock mass after collecting the core rock sample of the reservoir where the shale gas to be studied is located, and obtain the total analyzed gas volume at different metering times; the carbon isotope testing module 32 is implemented according to the method described in the above step S120, and is configured to perform a methane carbon isotope test on the analyzed gas obtained at different analysis sampling times, so as to obtain corresponding methane carbon isotope data; the existence status generating module 33 is implemented according to the method described in the above step S130, and is configured to calculate the ratio of the total analyzed gas volume at different metering times to the total analyzed gas content, and analyze the correlation between the methane carbon isotope data and the analyzed gas volume ratio, so as to obtain the existence status of the shale gas to be studied according to the analysis results.

[0048] The embodiment of the present invention further provides a computer-readable storage medium, in which at least one instruction is stored, and the instruction is loaded and executed by the processor to implement the operation of determining the existence state of shale gas performed in the method of the above embodiment. For example, the computer-readable storage medium can be ROM (Read Only Memory), RAM (Random Access Memory), CD-ROM (Compact Disc-Read Only Memory), magnetic tape, floppy disk and optical data storage device, etc.

[0049] The present invention discloses a method, system and storage medium for determining the existence state of shale gas. The method first collects core samples in the reservoir where the shale gas to be studied is located, and analyzes the rock gas content of the collected core samples to obtain the total analyzed gas volume data analyzed at different metering times, and the analysis results of the analyzed gas samples at different analysis sampling times. Afterwards, by performing a methane carbon isotope test on the analyzed gas samples, methane carbon isotope data is obtained, and the ratio of the total analyzed gas volume at different metering times to the analyzed total gas content is calculated, and the correlation between the methane carbon isotope data and the analyzed gas volume ratio is further obtained, so as to determine the existence state of the current shale gas to be studied according to the correlation. The present invention is different from the conventional method and realizes the rapid and accurate acquisition of the percentage of free gas and adsorbed gas in shale gas wells.

[0050] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0051] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims of the present invention.

[0052] It should be understood by those skilled in the art that the modules or steps of the present invention described above can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0053] Although the embodiments disclosed in the present invention are as above, the above contents are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for determining the existence state of shale gas, characterized in that: include: Collect core samples of the reservoir where the shale gas to be studied is located, and analyze the gas content of the rock mass to obtain the total analyzed gas volume at different metering times; Conduct methane carbon isotope testing on the analyzed gas obtained at different analysis sampling times, so as to obtain corresponding methane carbon isotope data; The ratio of the total analyzed gas volume at the different metering moments to the total analyzed gas content is calculated, and the correlation between the methane carbon isotope data and the analyzed gas volume ratio is analyzed, so as to obtain the existence status of the shale gas to be studied according to the analysis results.

2. The method according to claim 1, characterized in that The time interval between each adjacent measurement moment is 30 seconds; The time interval between each adjacent analytical sampling moment is 60 minutes.

3. The method according to claim 1 or 2, characterized in that: Before performing methane carbon isotope testing on the analyzed gas obtained at different analysis sampling times, the method further comprises: The saturated brine method is used to collect the analysis gas obtained at different analysis sampling times.

4. The method according to any one of claims 1 to 3, characterized in that The step of analyzing the correlation between the methane carbon isotope data and the analyzed gas volume ratio includes: Nonlinear fitting is performed on the methane carbon isotope data and the analyzed gas volume ratio in a rectangular coordinate system, so that the correlation is characterized by using the current fitting relationship curve.

5. The method according to claim 4, characterized in that The current correlation is represented by an exponential function, wherein the base of the exponential function is a natural constant, the methane carbon isotope data represents the independent variable index of the exponential function, and the analyzed gas volume ratio represents the dependent variable of the exponential function.

6. The method according to claim 4 or 5, characterized in that: The step of obtaining the existence state of the shale gas to be studied according to the analysis results includes: Recording the data point at the end of the analysis on the current fitting relationship curve as the first point, and recording the data point at the initial time of the analysis as the second point, so as to form a first straight line after connecting the first point and the second point; Draw a tangent line of the current fitting relationship curve with the first point as the tangent point, draw a first perpendicular line perpendicular to the x-axis through the second point, and then draw a second perpendicular line on the first straight line, wherein the second perpendicular line passes through the intersection of the tangent line and the first perpendicular line; According to the intersection of the second vertical line and the current fitting relationship curve, the free gas content in the shale gas to be studied is obtained, and then the adsorbed gas content in the shale gas to be studied is obtained according to the free gas content.

7. The method according to any one of claims 1 to 6, characterized in that: The step of analyzing the gas content of the rock mass on the core rock sample includes: During the analysis process, the core rock sample is located in a closed cavity inside a desorption tank, wherein the ambient temperature of the area where the desorption tank is located is the same as the formation temperature of the reservoir where the shale gas to be studied is located.

8. The method according to any one of claims 1 to 7, characterized in that: The steps of collecting core samples of the shale gas reservoir to be studied include: The core samples are collected by adopting a closed coring process, thereby preventing the core samples from being contaminated by drilling fluid.

9. A computer-readable storage medium, characterized in that: It contains a series of instructions for executing the method steps for determining the existence status of shale gas as claimed in any one of claims 1 to 8.

10. A system for determining the presence of shale gas, characterized in that: The system includes the following modules: The analyzed gas volume metering module is used to collect core samples of the reservoir where the shale gas to be studied is located, analyze the gas content of the rock mass, and obtain the total analyzed gas volume at different metering times; A carbon isotope test module is used to test the methane carbon isotope of the analyzed gas obtained at different analysis sampling times, so as to obtain corresponding methane carbon isotope data; The existence status generation module is used to calculate the ratio of the total analyzed gas volume at different metering times to the total analyzed gas content, and analyze the correlation between the methane carbon isotope data and the analyzed gas volume ratio, so as to obtain the existence status of the shale gas to be studied according to the analysis results.

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