Free gas saturation and gas occurrence ratio analysis method based on pore space

Abstract

The present application discloses a method for analyzing free gas saturation and gas occurrence ratio based on pore space, and relates to the technical field of coal rock development. The method comprises: conducting coal rock pore-related experiments to obtain the total pore space, which includes pore adsorption space and pore free space; establishing a free gas saturation calculation model; based on the pore adsorption space and pore free space, in combination with the free gas saturation calculation model, establishing an adsorbed gas and free gas quantity calculation model; based on the adsorbed gas and free gas quantity calculation model, establishing an adsorbed gas and free gas content relative ratio calculation model, and determining the relative proportion of adsorbed gas and free gas content. The present application can more comprehensively grasp the occurrence form of gas in coal rock, the content distribution characteristics and the relationship between the gas and the reservoir pore structure, reveal the migration mechanism and process of gas in the reservoir, and provide a solid theoretical support for subsequent reservoir evaluation.

Description

Technical Field

[0001] The present application relates to the technical field of coal and rock development, and in particular to a method for analyzing free gas saturation and gas occurrence ratio based on pore space. Background Art

[0002] At present, the analysis of free gas saturation and gas storage ratio in coal rock pores mainly includes pore structure experiments, on-site gas content tests and isothermal adsorption experiments.

[0003] Among them, the pore structure experiment is a full-aperture characterization experiment, involving four experiments: micron CT, high-pressure mercury injection, nitrogen adsorption, and carbon dioxide adsorption. The principle of micron CT is to scan the core with a computer tomography device to obtain a three-dimensional internal structure image at the micron scale, and calculate the relevant parameters of pores with a pore size of more than 1μm by introducing morphological and statistical parameters (pore fractal dimension, shape coefficient, and orientation factor). The principle of high-pressure mercury injection is to press mercury into the pores of porous media by applying external pressure, so as to obtain the pore distribution characteristics within the pore size range of a few nanometers to a few microns; the principle of nitrogen adsorption is to place the sample in a low-temperature environment, so that nitrogen is adsorbed on the surface of the sample, and the relationship between the amount of adsorbed gas and the relative pressure is measured to obtain the pore distribution characteristics of pores 2~200nm; carbon dioxide adsorption is similar to nitrogen adsorption, except that the gas selection is different, and the pore distribution characteristics below 2nm are obtained. However, the limitation of quantitative characterization lies in the fact that there are many testing methods for coal rock pore structure in the industry. Each method has different principles and applicable pore size range. There is no unified standard when splicing multiple test results together to obtain the pore volume and specific surface area within the full pore size range. Different splicing methods may lead to differences in quantitative results.

[0004] The principle of on-site pressure-maintained gas content test is to keep the pressure unchanged during the coring process, and to measure the gas content after collecting coal and rock samples. The specific steps include sample collection, pressure-maintained treatment, gas content determination and other links. The pressure-maintained coring and gas measurement method can reduce gas escape during the coring process and improve the accuracy of the measurement. However, the adsorption performance is uncertain: the adsorption performance of coal and rock to gas is affected by many factors, such as coal quality, temperature, pressure, etc. Although the isothermal adsorption experiment is carried out under simulated reservoir conditions, the temperature and pressure in the actual reservoir are complex and changeable, and it is difficult to fully simulate with limited experimental conditions. The test results can only be infinitely close but cannot fully reflect the actual situation of the formation.

[0005] The principle of isothermal adsorption experiment is to contact the adsorbent with the coal sample at a certain temperature, observe the adsorption capacity and adsorption rate of the coal sample, and obtain important parameters such as Langmuir volume and Langmuir pressure, which represent the maximum adsorption capacity and adsorption characteristics of the sample. However, the influencing factors of isothermal adsorption experiment are diverse: the actual coal rock reservoir is much more complicated, including the heterogeneity of coal rock structure, the influence of pore water on coal rock adsorption, etc.

[0006] Therefore, with the continuous advancement of coal and rock development technology and the deepening of research, it is necessary to gradually improve and perfect the existing calculation models to better adapt to the complexity of actual reservoirs. Summary of the invention

[0007] The present invention proposes a method for analyzing free gas saturation and gas occurrence ratio based on pore space, including: Conduct coal-rock pore-related experiments to obtain the pore volume and specific surface area data of full-diameter pores, and divide the pore size range of adsorption space and free space to obtain the total pore space, which includes pore adsorption space and pore free space; A free gas saturation calculation model was established by combining pore free space, field measured gas content, and isothermal adsorption curves; Based on the pore adsorption space and pore free space, combined with the free gas saturation calculation model, a calculation model for the amount of adsorbed gas and free gas is established; Based on the calculation model of the amount of adsorbed gas and free gas, a calculation model for the relative proportion of adsorbed gas and free gas content is established to determine the relative proportion of adsorbed gas and free gas content.

[0008] As described above, the free gas saturation and gas occurrence ratio analysis method based on pore space, wherein, in the total pore space, according to the full pore volume and specific surface area distribution characteristics, the surface area provided by the pores within the full pore size range is determined as the pore adsorption space of coal gas, and the pore volume provided by the mesopores and macropores is determined as the pore free space.

[0009] In the above-mentioned free gas saturation and gas occurrence ratio analysis method based on pore space, the porosity damage rate is obtained through the overburden porosity permeability test, and the porosity damage rate is used to correct the pore free space to obtain the corrected pore free space.

[0010] The above-mentioned free gas saturation and gas storage ratio analysis method based on pore space, wherein the corrected free gas storage space is obtained according to the field measured gas content and isothermal adsorption curve, specifically includes the following sub-steps: Calculate the saturated adsorption capacity of the coal seam at reservoir pressure, i.e. the adsorbed gas content; Correction of free gas content according to adsorbed gas content; According to the corrected free gas content and gas compressibility coefficient, the pore space occupied by the free gas under the in-situ conditions of the reservoir is obtained, that is, the corrected free gas occurrence space.

[0011] In the above-mentioned free gas saturation and gas occurrence ratio analysis method based on pore space, the free gas saturation is calculated based on the corrected free gas occurrence space and the corrected pore free space.

[0012] The above-mentioned free gas saturation and gas occurrence ratio analysis method based on pore space, wherein a calculation model for the amount of adsorbed gas and free gas is established, specifically: Idealize the coalbed methane macromolecule into a spherical methane molecule, and calculate the cross-sectional area and volume of a single methane molecule based on the diameter of the methane molecule. According to the pore adsorption space and the cross-sectional area of ​​methane molecules, a calculation model for the amount of adsorbed gas is established; According to the free gas storage space, combined with the volume of a single methane molecule, and taking into account the space utilization rate of spherical molecules, a free gas quantity calculation model is established.

[0013] The free gas saturation and gas occurrence ratio analysis method based on pore space as described above, wherein a calculation model for the relative ratio of adsorbed gas to free gas content is established, specifically: based on the adsorbed gas quantity calculation model and the free gas quantity calculation model, a calculation model for the ratio of the two is established as a calculation model for the relative ratio of adsorbed gas to free gas content.

[0014] The beneficial effects achieved by this application are as follows: (1) Deepen the understanding of reservoir mechanism: Through the data of free gas saturation and the relative proportion of adsorbed gas to free gas content, we can have a more comprehensive understanding of the occurrence form and content distribution characteristics of gas in coal rock and its relationship with the reservoir pore structure, further reveal the migration mechanism and process of gas in the reservoir, and provide solid theoretical support for subsequent reservoir evaluation.

[0015] (2) Optimizing mining plans: During the mining process, reasonable control of reservoir pressure is crucial, as it is directly related to reservoir stability and gas migration. By understanding the relative proportion of adsorbed gas and free gas, we can more accurately predict the impact of pressure changes on the occurrence of both, thereby formulating more scientific and reasonable pressure management measures to achieve sustainable development and utilization of coalbed methane. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0017] Figure 1 This is a flow chart of a method for analyzing free gas saturation and gas occurrence ratio based on pore space provided in Example 1 of the present application. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0019] Embodiment 1 like Figure 1 As shown, the first embodiment of the present application provides a method for analyzing free gas saturation and gas occurrence ratio based on pore space, including: Step 110: Conduct coal-rock pore-related experiments to obtain pore volume and specific surface area data of full-aperture pores, and divide the pore size range of adsorption space and free space to obtain the total pore space, which includes pore adsorption space and pore free space; Specifically, conventional experiments on coal rock reservoirs mainly include coal rock pore-related experiments, isothermal adsorption experiments, and on-site gas content tests. Based on the pore adsorption space and pore free space provided by pores at all levels of coal rock reservoirs, a free gas saturation calculation model is established, and on this basis, a calculation model for the relative proportion of adsorbed gas and free gas content is further established.

[0020] Taking the low- and medium-rank coal-rock wells in the Junggar Basin as an example, the free gas saturation and gas occurrence ratio of coal-rock pores in Well A and Well B in the Junggar Basin were analyzed. A total of 2 cores were taken in Well A, with a total core length of 2.51m and an average reflectivity of 0.65%; a total of 3 cores were taken in Well B, with a total core length of 6.3m and an average reflectivity of 0.75%. The specific data are shown in Table 1: Table 1 Coal rock and coal quality data table

[0021] The above-mentioned void classification method was used to classify the voids in Well A and Well B of the low- and medium-rank coal rocks in the Junggar Basin. Well A took 2 cores with a total core length of 2.51m and an average reflectivity of 0.65%; Well B took 3 cores with a total core length of 6.3m and an average reflectivity of 0.75%. The full pore volume and specific surface area data table shown in Table 2 below were obtained: Table 2 Full pore volume and specific surface area data

[0022] The pore free space includes adsorption space and free space; according to the distribution characteristics of the full pore volume and specific surface area, the surface area provided by the pores in the full pore range is determined as the adsorption space of coal rock gas; the pore volume provided by the mesopores and macropores is used as the free space. The IUPAC pore classification method is preferably used, micropores (pore diameter <2nm), mesopores (pore diameter 2nm~50nm), and macropores (pore diameter >50nm). V1, V2, and V3 are the pore volumes corresponding to micropores, mesopores, and macropores, respectively; S1, S2, and S3 are the specific surface areas corresponding to micropores, mesopores, and macropores, respectively. The surface area provided by the pores in the full pore range is used as the pore adsorption space of the adsorbed gas, and the pore volume provided by the mesopores and macropores is used as the pore free space in the free state.

[0023] Pore ​​adsorption space range and quantitative characterization: In coal rock, micropores provide a large number of adsorption sites for gas molecules due to their extremely small pore size and high specific surface area, thus becoming the main storage space for adsorbed gas. Although the specific surface area of ​​mesopores and macropores is low, they also contribute a small amount of adsorption space. Therefore, in this application, the surface area provided by pores within the full pore size range is used as the pore adsorption space of coal rock gas, that is, S1+ S2+S3.

[0024] The scope and quantitative characterization of pore free space: Micropores are mainly pores between macromolecules in the coal matrix and can only store adsorbed gas, while the pore volume provided by mesopores and macropores can be used as free space, that is, V1+V2. However, free space can not only store gas, but also may contain a certain amount of water. In order to calculate the free gas space more accurately, the "free gas saturation" parameter should be introduced to participate in the calculation. Free gas saturation refers to the ratio of the volume of free gas in the pores to the total volume of the pores, which reflects the degree to which the pore space is filled with free gas. Specifically, the free gas saturation that reflects the degree to which the pore space is filled with free gas is determined based on the ratio of the volume of free gas in the pores to the total volume of the pores, and the pore free space is determined based on the pore volume provided by the mesopores and macropores and the free gas saturation.

[0025] From Table 1, we can see that the adsorption space provided by each gram of coal rock in Well A is 151.9m 2 、100.2m 2 , the adsorption space provided by each gram of coal rock in Well B is 95.7m 2、47.3 m 2 、102.0 m 2 ; The free space of each cylinder in Well A is 0.1894cm 3 / g, 0.1053 cm 3 / g; the free space of each tube in Well B is 0.1109 cm 3 / g, 0.0419 cm 3 / g, 0.0449cm 3 / g. The quantitative characterization of the pore volume and specific surface area of ​​the full-aperture pores of coal rock in this application can accurately obtain the pore volume and specific surface area distribution characteristics of pores at all levels of coal rock through pore structure-related testing methods, thereby dividing the pore adsorption space and pore free space of the pores.

[0026] Step 120, establishing a free gas saturation calculation model based on pore free space, on-site measured gas content, and isothermal adsorption curve; When conducting on-site gas content tests, the desorbed gas and free gas content data can be obtained. However, due to the complexity of some physical processes in the actual operation, such as the adsorption-desorption-desorption process of gas from the core drilling to the desorption tank is a dynamic and cyclic process, which leads to certain deviations in the desorbed gas and free gas content data. Therefore, it is necessary to correct the free gas content through the isothermal adsorption curve and then calculate the free gas saturation in the pores.

[0027] This application corrects the relevant parameters for calculating free gas saturation. In order to calculate free gas saturation more accurately, the actual measured free gas content and pore free space on site are considered to have certain deviations from the actual reservoir conditions. First, the isothermal adsorption curve is used to obtain the in-situ saturated adsorption of coal rock, thereby correcting the deviation of free gas content caused by desorption and diffusion of adsorbed gas. Secondly, the porosity damage rate is used to correct the in-situ pore free space. The correction method is applicable to changes in different coal rock types and reservoir conditions, and has strong universality and flexibility.

[0028] Free gas content correction, specifically: the coal rock langmuir model can reflect the gas adsorption capacity of coalbed methane at different pressures, so the saturated adsorption capacity of the coal seam at the reservoir pressure can be calculated , that is, to obtain a more accurate adsorbed gas content and then correct the free gas content.

[0029] The Langmuir equation formula is as follows: (1) Then, the corrected free gas content is obtained by subtracting the in-situ saturated adsorption amount from the total gas content. : (2) In the formula, To measure the gas content on site; is the isothermal adsorption Langmuir volume; is the isothermal adsorption Rankine pressure; is the in-situ saturated adsorption capacity; is the corrected free gas content; is the in situ reservoir pressure.

[0030] The field gas content test and isothermal adsorption data of Well A and Well B are shown in Table 3. The free gas content is corrected according to Formula (1) and Formula (2). After correction, the free gas content of each cylinder in Well A is 4.94 cm 3 / g, 4.48cm 3 / g; the free gas content of each tube in Well B is 8.04cm 3 / g, 6.16cm 3 / g, 6.66m 3 / g: Table 3 Measured gas content in the study area and gas content parameters of isothermal adsorption experiment

[0031] The corrected free gas content is measured under ground temperature and pressure conditions. However, under reservoir conditions, when pressure and temperature change, the volume of space occupied by the gas will also change. The law of change conforms to the ideal gas state equation. The degree of change can be represented by the gas compressibility coefficient Z: (3) Where Z is the gas compressibility coefficient; are the gas pressure, volume and temperature under the surface state; P, V and T are the gas pressure, volume and temperature under the in-situ conditions of the reservoir.

[0032] According to the corrected free gas content and gas compressibility, the pore space occupied by free gas under the in-situ conditions of the reservoir can be obtained, that is, the corrected free gas storage space : (4) The pore structure data obtained in conventional experiments are obtained under normal pressure conditions. In order to restore the pore volume under reservoir pressure, plunger samples are drilled in the coal rock core section to conduct overburden porosity tests. The porosity damage rate can be calculated based on the result data. , porosity damage rate As shown in Table 4 below: Table 4 Porosity damage rate

[0033] The free space of each well in Well A under the in-situ reservoir pressure 0.1661 cm3 / g, 0.0594cm 3 / g; the free space of each tube in Well B is 0.0870 cm 3 / g, 0.0268 cm 3 / g, 0.0283 cm 3 / g.

[0034] Free gas saturation The space occupied by free gas per unit mass Pore ​​free space The ratio of , formula (2), formula (3), and formula (4) are substituted into the final free gas saturation calculation model as follows: (5) Substituting the reservoir pressure and temperature of Wells A and B into Formula (3), the gas compressibility coefficients of the two wells are obtained, which are 83.54 for Well A and 95.47 for Well B. Substituting the compressibility coefficient and the corrected free gas content into Formula (4), the space occupied by free gas under the in-situ reservoir conditions is obtained. The space occupied by free gas in each well of Well A is 0.0591 cm3 / g and 0.0537 cm3 / g, and the space occupied by free gas in each well of Well B is 0.0843 cm3 / g, 0.0645 cm3 / g, and 0.0698 cm3 / g. Given the free space and the space occupied by free gas under the reservoir pressure, the free gas saturation is obtained according to Formula (5). The free gas saturations of each well of Well A are 35.59% and 90.36%, respectively; the free gas saturations of each well of Well B are 96.82%, 100%, and 100%, respectively. Table 5 is the calculation parameter table of free gas saturation in the study area: Table 5 Calculation parameters of free gas saturation in the study area

[0035] Step 130: Based on the pore adsorption space and the pore free space, in combination with the free gas saturation calculation model, a calculation model for the amount of adsorbed gas and free gas is established; Generally, the size of coalbed methane macromolecules is between 0.32 and 0.55 nm, and the gas component is mainly methane. Therefore, this application uses the size of methane molecules to represent coalbed methane macromolecules to establish a calculation model. Assuming that the methane molecule is an ideal sphere and the diameter d of the methane molecule is known to be 0.38 nm, the cross-sectional area of ​​a single methane molecule can be calculated. 1.13354E -19 m 2 The volume of a single methane molecule 2.87163E -23 cm 3 .

[0036] Based on the monolayer adsorption theory, the gas adsorption space and the cross-sectional area of ​​the methane molecule are known, and a model for calculating the amount of adsorbed gas can be established as follows: (6) In the formula, are the specific surface areas corresponding to micropores, mesopores, and macropores, respectively; is the cross-sectional area of ​​a methane molecule; is the number of methane molecules in the adsorption space.

[0037] Knowing the free space and free gas saturation, we can know the space occupied by free gas. Combined with the volume of a single methane molecule and considering the space utilization rate of spherical molecules, a free gas quantity calculation model is established. The formula is as follows: (7) In the formula, , are the pore volumes corresponding to mesopores and macropores, respectively; is the volume of one methane molecule; is the number of molecules of matter in the free space; is the molecular space utilization, which is 0.74; is the free gas saturation.

[0038] Given the storage space of adsorbed gas and free gas, combined with the cross-sectional area and volume of gas molecules, substitute them into formula (6) and formula (7) to obtain the amount of adsorbed gas and free gas.

[0039] Step 140: Based on the calculation model of the amount of adsorbed gas and free gas, a calculation model for the relative proportion of adsorbed gas and free gas content is established to determine the relative proportion of adsorbed gas and free gas content.

[0040] This application uses pore space and gas molecule size to innovatively establish a method for calculating the relative proportion of adsorbed gas and free gas content. Based on the size of methane molecules and the storage space of gases in different storage states, a calculation model for the number of gases in different storage states is established to obtain the relative proportion of adsorbed gas and free gas content, thereby gaining a deeper understanding of the storage state and distribution law of gas in the reservoir.

[0041] The ratio of adsorbed gas content to free gas content, K, is the ratio of the two. The final calculation model is as follows: (8) According to formula (8), the relative proportions of adsorbed gas content in well A are 46.81% and 39.00% respectively; the relative proportions of adsorbed gas content in well B are 28.00%, 37.66% and 55.27% respectively, as shown in Table 6: Table 6 Relative proportion of adsorbed gas and free gas content

[0042] It can be seen from the above that although the reflectivity and coal rock components of the two are different, both wells have reached adsorption saturation, resulting in the generation of free gas. From the perspective of storage space, Well A shows greater advantages, with higher adsorption space and free space, which indicates that after gas is generated in the reservoir, Well A can provide more storage space to store gas; however, the measured results show that the gas content of Well B is higher than that of Well A. On the one hand, it is affected by many factors such as coal-forming materials, coal-forming environment, and preservation conditions; on the other hand, combined with the data on free gas saturation and relative proportion of free gas content, further analysis can be made from the perspective of seepage production mechanism: the free gas saturation of Well B is as high as over 95% and the free gas content accounts for a higher proportion, indicating that the pores are almost completely occupied by gas, with less water, and free gas is more likely to seep, which is conducive to gas production; in contrast, the pores of Well A contain varying degrees of moisture, with local water content even reaching 65% and a low free gas content, which makes it difficult for free gas to be discharged, and high water content easily leads to water lock, which hinders the flow of gas and further reduces the gas production capacity of Well A.

[0043] Through the above analysis, for Well A, due to its obvious storage space advantage but high water content, the key consideration should be how to reduce the water content and improve the gas seepage capacity. In the development plan, it can be considered to transform the reservoir permeability and adopt drainage gas production technology for production; for Well B, since it already has a high free gas saturation and gas production potential, it can be exploited first to achieve economic benefits as soon as possible, but in order to maintain the stability of the reservoir and achieve sustainable development, it is also necessary to pay attention to adopting a reasonable production rate and pressure control strategy to avoid excessive exploitation that causes a sharp drop in reservoir pressure, maintain the reservoir pressure within a certain range, and ensure stable gas production.

[0044] In summary, based on the pore space of coal rock, the gas storage space in different occurrence states was quantitatively characterized, and a free gas saturation calculation model and a calculation model for the relative proportion of adsorbed gas and free gas content were established. In the process of establishing the model, this application fully considered multiple factors such as the pore structure, adsorption characteristics, temperature and pressure changes, free gas saturation, and spatial molecular utilization of coal rock, so that the results are closer to the actual situation. The calculation model proposed in this application will help to deepen the understanding of the coal rock gas production mechanism, predict the occurrence state and output potential of coal rock gas, and thus provide a scientific basis for the exploration and development of coal rock gas.

[0045] According to the method of the present invention, the adsorption space and free space size of coal rock pores can be clarified, and the pore space can be innovatively used to obtain the free gas saturation and the relative content ratio of adsorbed gas and free gas. The specific effects are as follows: First, by calculating the data, we can more comprehensively understand the occurrence form of gas in coal rock, the distribution characteristics of its content, and its relationship with the pore structure of the reservoir, and further reveal the migration mechanism and process of gas in the reservoir; and in the evaluation of coal-rock gas well reservoirs, a combined evaluation model of "gas generation-adsorption-gas storage-free gas saturation" has been formed, which not only takes into account the gas generation capacity, adsorption capacity and gas storage space of the coal seam, but also takes free gas saturation as an important consideration. Different levels of the combined model of "gas generation-adsorption-gas storage-free gas saturation" will lead to significant differences in production capacity between wells. Through scientific evaluation methods and means, the production capacity and potential of coal-rock gas wells can be predicted more accurately.

[0046] Secondly, after clarifying the gas occurrence form and content distribution characteristics, it is possible to provide guiding data for on-site production measures and analyze the influencing factors of well differences in combination with production capacity: for example, wells with high free gas saturation are more prone to seepage, that is, gas production can be achieved under a smaller pressure difference. This type of well may have a higher initial production capacity during the production process and can be mined first, but it is necessary to pay attention to adopting a reasonable production rate and pressure control strategy to avoid excessive exploitation that leads to a sharp drop in reservoir pressure and ensure stable gas production; for wells with low free gas saturation, it is necessary to focus on how to reduce the water content and improve the gas seepage capacity. In the development plan, it is necessary to consider the transformation of reservoir permeability and the use of drainage gas production technology for production.

[0047] In summary, the method of the present invention has a good application effect in deepening the understanding of reservoir mechanism and optimizing coal rock gas extraction strategy.

[0048] Corresponding to the above embodiment, an embodiment of the present application provides a computer storage medium, including: at least one memory and at least one processor; The memory is used to store one or more program instructions; The processor is used to run one or more program instructions to execute a pore space-based free gas saturation and gas occurrence ratio analysis method.

[0049] Corresponding to the above-mentioned embodiments, an embodiment of the present application provides a computer-readable storage medium, which contains one or more program instructions, and the one or more program instructions are used by the processor to execute a free gas saturation and gas occurrence ratio analysis method based on pore space.

[0050] The embodiments disclosed in the present application provide a computer-readable storage medium, in which computer program instructions are stored. When the computer program instructions are executed on a computer, the computer executes the above-mentioned free gas saturation and gas occurrence ratio analysis method based on pore space.

[0051] In the embodiment of the present application, the processor may be an integrated circuit chip having the ability to process signals. The processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0052] The methods, steps and logic diagrams disclosed in the embodiments of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiments of the present application can be directly embodied as a hardware decoding processor for execution, or a combination of hardware and software modules in the decoding processor for execution. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The processor reads the information in the storage medium and completes the steps of the above method in combination with its hardware.

[0053] The storage medium may be a memory, which may be, for example, a volatile memory or a nonvolatile memory, or may include both volatile and nonvolatile memory.

[0054] Among them, the non-volatile memory can be a read-only memory (ROM), a programmable ROM (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory.

[0055] The volatile memory may be a random access memory (RAM) which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate synchronous DRAM (DDRSDRAM), enhanced synchronous DRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus DRAM (DRRAM).

[0056] The storage media described in the embodiments of the present application are intended to include, but are not limited to, these and any other suitable types of memory.

[0057] Those skilled in the art should be aware that in one or more of the above examples, the functions described in this application can be implemented by a combination of hardware and software. When the software is applied, the corresponding functions can be stored in a computer-readable medium or transmitted as one or more instructions or codes on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein the communication media includes any medium that is convenient for transmitting a computer program from one place to another. The storage medium can be any available medium that a general or special-purpose computer can access.

[0058] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation methods of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made on the basis of the technical solutions of the present application should be included in the scope of protection of the present application.

Claims

1. A method for analyzing free gas saturation and gas occurrence ratio based on pore space, characterized in that: include: Conduct coal-rock pore-related experiments to obtain the pore volume and specific surface area data of full-diameter pores, and divide the pore size range of adsorption space and free space to obtain the total pore space, which includes pore adsorption space and pore free space; A free gas saturation calculation model was established by combining pore free space, field measured gas content, and isothermal adsorption curves; Based on the pore adsorption space and pore free space, combined with the free gas saturation calculation model, a calculation model for the amount of adsorbed gas and free gas is established; Based on the calculation model of the amount of adsorbed gas and free gas, a calculation model for the relative proportion of adsorbed gas and free gas content is established to determine the relative proportion of adsorbed gas and free gas content.

2. The method for analyzing free gas saturation and gas occurrence ratio based on pore space according to claim 1, characterized in that: In the total pore space, according to the distribution characteristics of full pore volume and specific surface area, the surface area provided by the pores within the full pore size range is determined as the pore adsorption space of coal rock gas, and the pore volume provided by the mesopores and macropores is determined as the pore free space.

3. The method for analyzing free gas saturation and gas occurrence ratio based on pore space according to claim 2, characterized in that: The porosity damage rate is obtained through the overburden pressure porosity permeability test, and the porosity damage rate is used to correct the pore free space to obtain the corrected pore free space.

4. The method for analyzing free gas saturation and gas occurrence ratio based on pore space according to claim 3, characterized in that: The corrected free gas storage space is obtained based on the on-site measured gas content and isothermal adsorption curve, which specifically includes the following sub-steps: Calculate the saturated adsorption capacity of the coal seam at reservoir pressure, i.e. the adsorbed gas content; Correction of free gas content according to adsorbed gas content; According to the corrected free gas content and gas compressibility coefficient, the pore space occupied by the free gas under the in-situ conditions of the reservoir is obtained, that is, the corrected free gas occurrence space.

5. The method for analyzing free gas saturation and gas occurrence ratio based on pore space according to claim 4, characterized in that: The free gas saturation is calculated based on the corrected free gas storage space and the corrected pore free space.

6. The method for analyzing free gas saturation and gas occurrence ratio based on pore space according to claim 5, characterized in that: A calculation model for the amount of adsorbed gas and free gas is established, specifically: Idealize the coalbed methane macromolecule into a spherical methane molecule, and calculate the cross-sectional area and volume of a single methane molecule based on the diameter of the methane molecule. According to the pore adsorption space and the cross-sectional area of ​​methane molecules, a calculation model for the amount of adsorbed gas is established; According to the free gas storage space, combined with the volume of a single methane molecule, and taking into account the space utilization rate of spherical molecules, a free gas quantity calculation model is established.

7. The method for analyzing free gas saturation and gas occurrence ratio based on pore space according to claim 6, characterized in that: A calculation model for the relative proportion of adsorbed gas and free gas content is established. Specifically, based on the calculation model for the amount of adsorbed gas and the calculation model for the amount of free gas, a calculation model for the ratio of the two is established as a calculation model for the relative proportion of adsorbed gas and free gas content.

8. A computer storage medium, characterized in that: include: at least one memory and at least one processor; The memory is used to store one or more program instructions; A processor is used to run one or more program instructions to execute the free gas saturation and gas occurrence ratio analysis method based on pore space as described in any one of claims 1 to 7.

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