Method for measuring porosity of undisturbed formation of shale

Abstract

The invention relates to the technical field of shale undisturbed formation porosity determination, and discloses a shale undisturbed formation porosity determination method, which comprises: selecting a representative rock sample from a shale formation, carrying out necessary cutting and oil washing treatment on the selected rock sample, crushing the treated shale sample, and screening to obtain the shale undisturbed formation porosity. The method comprises the following steps: selecting particles with proper mesh number, and measuring the density of a shale skeleton sample under the condition of simulating formation temperature and pressure by utilizing a high-temperature and high-pressure magnetic suspension balance or other high-precision density measuring equipment. According to the method, more accurate formation porosity parameters can be obtained by directly measuring the porosity of the shale undisturbed formation, errors caused by change of a pore structure in the processes of sample treatment, transportation and the like are avoided, and the porosity condition of the shale in the formation can be reflected more truly by simulating the formation pressure condition for measurement. Errors caused by differences between experimental conditions and stratum conditions are avoided, and accuracy is improved.

Description

Technical Field

[0001] The invention relates to the technical field of measuring the porosity of shale original formations, and in particular to a method for measuring the porosity of shale original formations. Background Art

[0002] The porosity of shale original formation is an important parameter in the field of shale oil and gas exploration and development. It involves the resource potential evaluation of shale oil and gas, the selection of exploration targets, the calculation of reserves, the economic evaluation of mining, and the optimization of development measures. Porosity refers to the ratio of the sum of the volumes of all pore spaces in a rock sample to the volume of the rock sample, which is called the total porosity of the rock. It is expressed as a percentage. The larger the total porosity of the reservoir, the larger the pore space in the rock. From a practical point of view, only those pores that are interconnected are of practical significance, because they can not only store oil and gas, but also allow oil and gas to permeate through them. Therefore, in production practice, the concept of effective porosity is proposed. Effective porosity refers to the ratio of the sum of the volumes of pores that are interconnected and allow fluid to flow under normal pressure conditions to the total volume of the rock sample, expressed as a percentage;

[0003] Traditional measurement methods include gas adsorption, mercury injection, nuclear magnetic resonance, helium expansion, etc. However, these traditional measurement methods are difficult to fully simulate formation conditions when used. Formation conditions are complex and changeable, including pressure, temperature, fluid properties and other factors. Traditional measurement methods are usually difficult to fully simulate these real formation conditions under laboratory conditions, which may lead to deviations between the measurement results and the actual situation and cannot guarantee accuracy. Therefore, a new method is proposed to solve this technical problem and improve accuracy. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a method for measuring the porosity of shale original formations, which has the advantages of improving accuracy, etc., and solves the problem that the traditional method mentioned in the above background technology cannot improve accuracy.

[0006] (II) Technical solution

[0007] In order to achieve the purpose of improving the accuracy of the above background technology, the present invention provides the following technical solution: a method for measuring the porosity of shale original formation, comprising the following steps:

[0008] Step 1: Select representative rock samples from the shale formation, and perform necessary cutting and oil washing on the selected rock samples;

[0009] Step 2: crush and sieve the treated shale sample to select particles with appropriate mesh size;

[0010] Step 3: Using a high-temperature and high-pressure magnetic suspension balance or other high-precision density measuring equipment, the density of the shale skeleton sample is measured under conditions simulating formation temperature and pressure;

[0011] Step 4: Analyze the composition of the fluid in the shale sample, and calculate the density of the fluid in the shale under the formation temperature and pressure based on the composition of the fluid and the underground density of each fluid;

[0012] Step 5: Obtain the overall density of shale in the target formation through density logging data and geological exploration methods;

[0013] Step 6: Verify the measurement results by using methods such as nuclear magnetic resonance to evaluate the reliability and accuracy of the measurement results;

[0014] Step 7: Organize the measurement results into a report format, including sample information, experimental conditions, measurement steps, measurement results and verification results.

[0015] Preferably, the selected rock samples are ensured to represent the characteristics of the entire shale formation, and rock samples with typical characteristics are selected from the shale formation, including bedding development, mineral composition, and rock color to ensure that the selected rock samples are evenly distributed in the shale formation and are representative;

[0016] The cutting and oil washing of rock samples also includes the following steps:

[0017] Step 1: Use professional cutting tools and equipment to cut the rock samples into regular shapes, and ensure that the samples are not damaged during the cutting process. Cut the rock samples into shapes and sizes suitable for experimental analysis;

[0018] Step 2: Place the cut rock samples into an oil washing device and use appropriate solvents to soak and wash them to remove crude oil and other organic matter in the rock samples to avoid affecting the porosity measurement results.

[0019] During the cleaning process, the solvent temperature, immersion time and number of cleanings need to be controlled to ensure the complete removal of crude oil and other organic matter. During the oil washing process, it is necessary to avoid damaging the rock samples or changing their pore structure. It is necessary to ensure the full recovery and treatment of the solvent to avoid pollution to the environment. Before cutting the rock samples and washing the oil, the samples need to be marked and recorded for tracking and comparison in subsequent experiments.

[0020] Preferably, the sample is crushed and sieved, and the particles with appropriate mesh size are selected as follows:

[0021] Use professional crushing equipment to crush the processed shale samples into smaller particles. During the crushing process, the speed, crushing time and crushing degree of the crushing equipment need to be controlled;

[0022] The crushed shale samples are sieved through sieves of different mesh sizes. The mesh size of the sieve determines the particle size of the particles passing through the sieve. According to the experimental requirements, particles of appropriate mesh size are selected for subsequent experiments.

[0023] The processed shale samples are crushed and sieved, and particles of appropriate mesh size are selected in order to obtain shale samples that meet the experimental requirements. Particles of different mesh sizes have different particle size distributions, which will affect the porosity measurement results. By selecting particles of appropriate mesh size, the accuracy and repeatability of the experimental results can be ensured. During the crushing and sieving process, it is necessary to avoid damaging the pore structure of the shale samples. Therefore, it is necessary to select suitable crushing equipment and screens, and control the parameters during the processing. When selecting particles of appropriate mesh size, it is necessary to consider the requirements of the experimental method and the characteristics of the shale samples. Particles of different mesh sizes may have different effects on the experimental results.

[0024] Preferably, the formation temperature and pressure are important factors affecting the shale skeleton density. The shale skeleton sample is placed under set temperature and pressure conditions for measurement by a high temperature and high pressure experimental device. The experimental device can accurately control the temperature and pressure parameters to ensure the accuracy of the measurement results, and specifically:

[0025] The processed shale samples are crushed and sieved, and particles with appropriate mesh size are selected as shale skeleton samples;

[0026] Before measuring, the high temperature and high pressure magnetic suspension balance or other high precision density measuring equipment needs to be calibrated;

[0027] The shale skeleton sample is placed in the measuring device, and the simulated formation temperature and pressure conditions are set to perform density measurement;

[0028] The density of the shale skeleton sample is calculated according to the measurement results and related formulas, where p is the density of the shale skeleton under formation temperature and pressure, m is the mass of the shale skeleton sample, and V is the volume of the shale skeleton under formation temperature and pressure. The density parameter is then obtained according to p=m / V.

[0029] In this experiment, a high-temperature and high-pressure magnetic levitation balance and other high-precision density measurement equipment were used. The high-temperature and high-pressure magnetic levitation balance uses magnetic levitation technology to suspend the sample during the measurement process, avoiding the influence of the contact force between the sample and the measuring container on the measurement results in traditional measurement methods. At the same time, the formation conditions are simulated in a high-temperature and high-pressure environment, making the measurement results closer to the actual situation. It has high precision, high stability and repeatability, and can accurately measure the density of shale skeleton samples under simulated formation temperature and pressure conditions.

[0030] Preferably, the fluid in the shale sample usually includes a water phase, an oil phase and a gas phase. First, the composition of these fluids needs to be determined, that is, their respective volume fractions in the shale. After determining the composition of the fluid, the underground density of each fluid is determined, and then the weighted average method is used to calculate the fluid density in the shale under the formation temperature and pressure.

[0031] Select multiple rock samples from the shale sample development section with typical characteristics, ensure that the rock samples are homogeneous, and the sample thickness should be greater than 1 meter. Under the conditions of formation temperature and pressure, process the rock samples through steps such as crushing, washing, and drying. Use a high-temperature and high-pressure magnetic suspension balance to measure the density of the shale skeleton sample, perform composition analysis on the fluid in the shale sample, determine the volume fractions of the water phase, oil phase, and gas phase, and use the corresponding calculation formula to obtain the density of the fluid in the shale under formation temperature and pressure based on the composition of the fluid and the underground density of each fluid. Combined with the shale skeleton density and the density of the fluid in the shale under formation temperature and pressure, use the porosity calculation formula to obtain the original formation porosity of the shale;

[0032] The porosity is then calculated based on porosity = (1 – skeleton density / total density) × 100%.

[0033] Preferably, the density logging is a logging method that uses the Compton scattering effect to study the density of rock formations. During the drilling process, the density logging instrument can be used to continuously measure and record the density data of the formation. By analyzing and processing the density logging data, the overall density of the shale in the target formation can be calculated. During the geological exploration process, rock samples of the target formation can be obtained through geological surveys, drilling sampling and other means. Laboratory analysis of the rock samples, such as density measurement and mineral composition analysis, can obtain more detailed information on the physical properties of the rock.

[0034] Porosity calculation formula: After obtaining the overall density of shale, the porosity of the original shale formation can be calculated by combining other parameters. The porosity calculation formula is usually:

[0035] Porosity = (p_ma-p_b) / (p_ma-p_f) × 100%, where p_ma is the rock skeleton density, p_b is the overall density of shale, and p_f is the fluid density;

[0036] The rock skeleton density is usually obtained through laboratory analysis, while the fluid density may need to be calculated based on the fluid composition and temperature and pressure conditions of the formation or obtained by consulting relevant manuals.

[0037] Preferably, the nuclear magnetic resonance method is based on the interaction principle of the magnetic moment of atomic nuclei in a magnetic field, and obtains relevant information about the rock pore structure by measuring the relaxation time and signal intensity of a rock sample under an external magnetic field. The specific steps are:

[0038] Step 1: Obtain shale samples from the target formation and ensure that the samples are representative;

[0039] Step 2: Use a nuclear magnetic resonance instrument to measure the shale sample and record data such as relaxation time and signal intensity;

[0040] Step 3: Calculate the porosity of the sample using a specific algorithm and model based on the NMR measurement data;

[0041] Step 4: Compare and verify the results: Compare the porosity measured by NMR with the porosity measured by other methods.

[0042] The NMR method can perform measurements without destroying the sample, thus preserving the integrity and originality of the sample. The NMR method has high sensitivity to tiny pores and can detect pore structures that are difficult to detect using traditional methods. The NMR method can not only measure porosity, but also obtain more pore structure information such as pore size distribution and pore connectivity, providing a comprehensive basis for reservoir evaluation.

[0043] Preferably, the report form of the measurement results of the shale original formation porosity is a systematic process, which aims to clearly and accurately convey the experimental details, measurement results and their verification, describe the sample collection location, formation depth, lithology and other information, briefly describe the appearance, color, texture, etc. of the sample, explain the sample processing process before measurement, such as cleaning, drying, cutting, list the main equipment used for porosity measurement and its model, accuracy, describe the laboratory's environmental conditions such as temperature and humidity, and explain in detail the measurement parameters used in the experiment, such as the magnetic field strength and measurement time of the nuclear magnetic resonance method.

[0044] Compared with the prior art, the present invention provides a method for measuring the porosity of shale undisturbed formations, which has the following beneficial effects:

[0045] 1. The present invention can obtain more accurate formation porosity parameters by directly measuring the porosity of the original shale formation, avoiding errors caused by changes in the pore structure during sample processing and transportation, and can more realistically reflect the porosity of shale in the formation by simulating formation pressure conditions, avoiding errors caused by differences between experimental conditions and formation conditions, thereby improving accuracy.

[0046] 2. The accurate porosity parameters of the present invention provide important support for the theoretical research of shale oil and gas exploration and development, and help to reveal key issues such as the pore structure characteristics and fluid distribution laws of shale reservoirs. In order to meet the needs of shale oil and gas exploration and development, the measurement methods are constantly improved and innovated. The application of new technologies and methods has promoted technological progress and development in the field of shale oil and gas exploration and development.

[0047] 3. The present invention provides accurate porosity parameters, which are of great significance for evaluating the resource potential of shale oil and gas, selecting exploration targets, calculating reserves, and evaluating the economic feasibility of mining. It can help decision makers more accurately evaluate the storage performance of shale reservoirs and formulate reasonable exploration and development plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] See also Figure 1 A method for determining the porosity of an original shale formation comprises the following steps:

[0051] Step 1: Select representative rock samples from the shale formation, and perform necessary cutting and oil washing on the selected rock samples;

[0052] Step 2: crush and sieve the treated shale sample to select particles with appropriate mesh size;

[0053] Step 3: Using a high-temperature and high-pressure magnetic suspension balance or other high-precision density measuring equipment, the density of the shale skeleton sample is measured under conditions simulating formation temperature and pressure;

[0054] Step 4: Analyze the composition of the fluid in the shale sample, and calculate the density of the fluid in the shale under the formation temperature and pressure based on the composition of the fluid and the underground density of each fluid;

[0055] Step 5: Obtain the overall density of shale in the target formation through density logging data and geological exploration methods;

[0056] Step 6: Verify the measurement results by using methods such as nuclear magnetic resonance to evaluate the reliability and accuracy of the measurement results;

[0057] Step 7: Organize the measurement results into a report format, including sample information, experimental conditions, measurement steps, measurement results and verification results.

[0058] Specifically, Figure 1As shown, the rock samples selected are ensured to represent the characteristics of the entire shale formation, and rock samples with typical characteristics are selected from the shale formation, including bedding development, mineral composition, and rock color, to ensure that the selected rock samples are evenly distributed in the shale formation and are representative;

[0059] The cutting and oil washing of rock samples also includes the following steps:

[0060] Step 1: Use professional cutting tools and equipment to cut the rock samples into regular shapes, and ensure that the samples are not damaged during the cutting process. Cut the rock samples into shapes and sizes suitable for experimental analysis;

[0061] Step 2: Place the cut rock samples into an oil washing device and use appropriate solvents to soak and wash them to remove crude oil and other organic matter in the rock samples to avoid affecting the porosity measurement results.

[0062] Through the above technical scheme, the solvent temperature, immersion time and number of cleaning times need to be controlled during the cleaning process to ensure the complete removal of crude oil and other organic matter. During the oil washing process, it is necessary to avoid damaging the rock sample or changing its pore structure. It is necessary to ensure the full recovery and treatment of the solvent to avoid pollution to the environment. Before cutting the rock sample and washing the oil, the sample needs to be marked and recorded as necessary for tracking and comparison in subsequent experiments.

[0063] Specifically, Figure 1 As shown, the sample is crushed and sieved, and the particles with appropriate mesh size are selected as follows:

[0064] Use professional crushing equipment to crush the processed shale samples into smaller particles. During the crushing process, the speed, crushing time and crushing degree of the crushing equipment need to be controlled;

[0065] The crushed shale samples are sieved through sieves of different mesh sizes. The mesh size of the sieve determines the particle size of the particles passing through the sieve. According to the experimental requirements, particles of appropriate mesh size are selected for subsequent experiments.

[0066] Through the above technical scheme, the processed shale samples are crushed and screened, and particles of appropriate mesh size are selected in order to obtain shale samples that meet the experimental requirements. Particles of different mesh sizes have different particle size distributions, which will affect the porosity measurement results. By selecting particles of appropriate mesh size, the accuracy and repeatability of the experimental results can be ensured. During the crushing and screening process, it is necessary to avoid damaging the pore structure of the shale sample. Therefore, it is necessary to select suitable crushing equipment and screens, and control the parameters in the processing process. When selecting particles of appropriate mesh size, it is necessary to consider the requirements of the experimental method and the characteristics of the shale sample. Particles of different mesh sizes may have different effects on the experimental results.

[0067] Specifically, Figure 1 As shown, the formation temperature and pressure are important factors affecting the density of shale skeletons. The shale skeleton samples are placed under set temperature and pressure conditions for measurement by a high temperature and high pressure experimental device. The experimental device can accurately control the temperature and pressure parameters to ensure the accuracy of the measurement results, and specifically:

[0068] The processed shale samples are crushed and sieved, and particles with appropriate mesh size are selected as shale skeleton samples;

[0069] Before measuring, the high temperature and high pressure magnetic suspension balance or other high precision density measuring equipment needs to be calibrated;

[0070] The shale skeleton sample is placed in the measuring device, and the simulated formation temperature and pressure conditions are set to perform density measurement;

[0071] The density of the shale skeleton sample is calculated according to the measurement results and related formulas, where p is the density of the shale skeleton under formation temperature and pressure, m is the mass of the shale skeleton sample, and V is the volume of the shale skeleton under formation temperature and pressure. The density parameter is then obtained according to p=m / V.

[0072] Through the above technical scheme, and in this experiment, a high-temperature and high-pressure magnetic levitation balance and other high-precision density measurement equipment are used, among which the high-temperature and high-pressure magnetic levitation balance: uses magnetic levitation technology to suspend the sample during the measurement process, avoiding the influence of the contact force between the sample and the measuring container on the measurement result in the traditional measurement method. At the same time, the formation conditions are simulated by a high-temperature and high-pressure environment, so that the measurement results are closer to the actual situation, with high precision, high stability and repeatability, and can accurately measure the density of shale skeleton samples under simulated formation temperature and pressure conditions.

[0073] Specifically, Figure 1As shown, the fluid in the shale sample usually includes water phase, oil phase and gas phase. First, the composition of these fluids needs to be determined, that is, their respective volume fractions in the shale. After determining the composition of the fluid, the underground density of each fluid is determined, and then the weighted average method is used to calculate the fluid density in the shale under the formation temperature and pressure.

[0074] Through the above technical scheme, multiple rock samples of shale sample development sections with typical characteristics are selected to ensure homogeneity between the rock samples and that the sample thickness should be greater than 1 meter. Under formation temperature and pressure conditions, the rock samples are processed through crushing, cleaning, drying and other steps. The density of the shale skeleton sample is measured using a high-temperature and high-pressure magnetic suspension balance. The composition of the fluid in the shale sample is analyzed to determine the volume fractions of the water phase, oil phase and gas phase. According to the composition of the fluid and the underground density of each fluid, the density of the fluid in the shale under formation temperature and pressure is obtained using the corresponding calculation formula. In combination with the shale skeleton density and the density of the fluid in the shale under formation temperature and pressure, the porosity calculation formula is used to obtain the original formation porosity of the shale.

[0075] The porosity is then calculated based on porosity = (1 – skeleton density / total density) × 100%.

[0076] Specifically, Figure 1 As shown, the density logging is a logging method that uses the Compton scattering effect to study the density of rock formations. During the drilling process, the density logging instrument can be used to continuously measure and record the density data of the formation. By analyzing and processing the density logging data, the overall density of the shale in the target formation can be calculated. During the geological exploration process, rock samples of the target formation can be obtained through geological surveys, drilling sampling and other means. Laboratory analysis of the rock samples, such as density measurement and mineral composition analysis, can obtain more detailed information on the physical properties of the rock.

[0077] Through the above technical solution, the porosity calculation formula is: After obtaining the overall density of shale, the porosity of the original shale formation can be calculated by combining other parameters. The porosity calculation formula is usually:

[0078] Porosity = (p_ma-p_b) / (p_ma-p_f) × 100%, where p_ma is the rock skeleton density, p_b is the overall density of shale, and p_f is the fluid density;

[0079] The rock skeleton density is usually obtained through laboratory analysis, while the fluid density may need to be calculated based on the fluid composition and temperature and pressure conditions of the formation or obtained by consulting relevant manuals.

[0080] Specifically, Figure 1As shown, the nuclear magnetic resonance method is based on the interaction principle of the magnetic moment of the atomic nucleus in the magnetic field. By measuring the relaxation time and signal intensity of the rock sample under the external magnetic field, the relevant information of the rock pore structure is obtained. The specific steps are:

[0081] Step 1: Obtain shale samples from the target formation and ensure that the samples are representative;

[0082] Step 2: Use a nuclear magnetic resonance instrument to measure the shale sample and record data such as relaxation time and signal intensity;

[0083] Step 3: Calculate the porosity of the sample using a specific algorithm and model based on the NMR measurement data;

[0084] Step 4: Compare and verify the results: Compare the porosity measured by NMR with the porosity measured by other methods.

[0085] Through the above technical solution, the NMR method can be measured without destroying the sample, thus preserving the integrity and originality of the sample. The NMR method has high sensitivity to tiny pores and can detect pore structures that are difficult to detect with traditional methods. The NMR method can not only measure porosity, but also obtain more pore structure information such as pore size distribution and pore connectivity, providing a comprehensive basis for reservoir evaluation.

[0086] Specifically, Figure 1 As shown, the report format of the porosity determination results of shale undisturbed formations is a systematic process, which aims to clearly and accurately convey the experimental details, determination results and their verification, describe the sample collection location, formation depth, lithology and other information, briefly describe the appearance, color, texture, etc. of the sample, explain the sample processing process before the measurement, such as cleaning, drying, cutting, list the main equipment used for porosity determination and its model and accuracy, describe the laboratory's environmental conditions such as temperature and humidity, and explain in detail the measurement parameters used in the experiment, such as the magnetic field strength and measurement time of the nuclear magnetic resonance method.

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for determining the porosity of shale undisturbed formations, characterized in that: The following steps are involved: Step 1: Select representative rock samples from the shale formation, and perform necessary cutting and oil washing on the selected rock samples; Step 2: crush and sieve the treated shale sample to select particles with appropriate mesh size; Step 3: Using a high-temperature and high-pressure magnetic suspension balance or other high-precision density measuring equipment, the density of the shale skeleton sample is measured under conditions simulating formation temperature and pressure; Step 4: Analyze the composition of the fluid in the shale sample, and calculate the density of the fluid in the shale under the formation temperature and pressure based on the composition of the fluid and the underground density of each fluid; Step 5: Obtain the overall density of shale in the target formation through density logging data and geological exploration methods; Step 6: Verify the measurement results by using methods such as nuclear magnetic resonance to evaluate the reliability and accuracy of the measurement results; Step 7: Organize the measurement results into a report format, including sample information, experimental conditions, measurement steps, measurement results and verification results.

2. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The rock samples selected are ensured to represent the characteristics of the entire shale formation, and rock samples with typical characteristics are selected from the shale formation, including bedding development, mineral composition, and rock color, to ensure that the selected rock samples are evenly distributed in the shale formation and are representative; The cutting and oil washing of rock samples also includes the following steps: Step 1: Use professional cutting tools and equipment to cut the rock samples into regular shapes, and ensure that the samples are not damaged during the cutting process. Cut the rock samples into shapes and sizes suitable for experimental analysis; Step 2: Place the cut rock samples into an oil washing device and use appropriate solvents to soak and wash them to remove crude oil and other organic matter in the rock samples to avoid affecting the porosity measurement results.

3. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The sample is crushed and sieved, and the particles with appropriate mesh size are selected as follows: Use professional crushing equipment to crush the processed shale samples into smaller particles. During the crushing process, the speed, crushing time and crushing degree of the crushing equipment need to be controlled; The crushed shale samples are sieved through sieves of different mesh sizes. The mesh size of the sieve determines the particle size of the particles passing through the sieve. According to the experimental requirements, particles of appropriate mesh size are selected for subsequent experiments.

4. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The formation temperature and pressure are important factors affecting the density of shale skeletons. The shale skeleton samples are placed under set temperature and pressure conditions for measurement by a high temperature and high pressure experimental device. The experimental device can accurately control the temperature and pressure parameters to ensure the accuracy of the measurement results, and specifically: The processed shale samples are crushed and sieved, and particles with appropriate mesh size are selected as shale skeleton samples; Before measuring, the high temperature and high pressure magnetic suspension balance or other high precision density measuring equipment needs to be calibrated; The shale skeleton sample is placed in the measuring device, and the simulated formation temperature and pressure conditions are set to perform density measurement; The density of the shale skeleton sample is calculated according to the measurement results and related formulas, where p is the density of the shale skeleton under formation temperature and pressure, m is the mass of the shale skeleton sample, and V is the volume of the shale skeleton under formation temperature and pressure. The density parameter is then obtained according to p=m / V.

5. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The fluids in the shale sample usually include water phase, oil phase and gas phase. First, it is necessary to determine the composition of these fluids, that is, their respective volume fractions in the shale. After determining the composition of the fluids, the underground density of each fluid is determined, and then the weighted average method is used to calculate the fluid density in the shale under the formation temperature and pressure.

6. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The density logging is a logging method that uses the Compton scattering effect to study the density of rock formations. During the drilling process, the density logging instrument can be used to continuously measure and record the density data of the formation. By analyzing and processing the density logging data, the overall density of the shale in the target formation can be calculated. During the geological exploration process, rock samples of the target formation can be obtained through geological surveys, drilling sampling and other means. Laboratory analysis of the rock samples, such as density measurement and mineral composition analysis, can obtain more detailed information on the physical properties of the rock.

7. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The nuclear magnetic resonance method is based on the interaction principle of the magnetic moment of the atomic nucleus in the magnetic field. It obtains relevant information about the rock pore structure by measuring the relaxation time and signal intensity of the rock sample under an external magnetic field. The specific steps are as follows: Step 1: Obtain shale samples from the target formation and ensure that the samples are representative; Step 2: Use a nuclear magnetic resonance instrument to measure the shale sample and record data such as relaxation time and signal intensity; Step 3: Calculate the porosity of the sample using a specific algorithm and model based on the NMR measurement data; Step 4: Compare and verify the results: Compare the porosity measured by NMR with the porosity measured by other methods.

8. The method for determining the porosity of shale original formation according to claim 1, characterized in that: The above-mentioned compilation of the measurement results of the shale original formation porosity into a report form is a systematic process, which aims to clearly and accurately convey the experimental details, measurement results and their verification, describe the sample collection location, formation depth, lithology and other information, briefly describe the appearance, color, texture, etc. of the sample, explain the sample processing process before measurement, such as cleaning, drying, cutting, list the main equipment used for porosity measurement and its model and accuracy, describe the laboratory's environmental conditions such as temperature and humidity, and explain in detail the measurement parameters used in the experiment, such as the magnetic field strength and measurement time of the nuclear magnetic resonance method.

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