A method and device for calculating the permeability of a tight sandstone

Abstract

The application provides a method and device for calculating the permeability of tight sandstone, and relates to the technical field of tight oil and gas development. The method comprises the following steps: obtaining a dissolution pore size distribution curve of a tight sandstone sample, and obtaining a cumulative frequency distribution curve of the dissolution pore according to the dissolution pore size distribution curve; calculating a first product between a maximum cumulative frequency and a first preset proportion, and a second product between the maximum cumulative frequency and a second preset proportion, determining an upper limit value of a critical pore size of the dissolution pore corresponding to the first product and a lower limit value of the critical pore size of the dissolution pore corresponding to the second product according to a mapping relationship; and calculating the permeability of the tight sandstone according to the upper limit value and the lower limit value of the critical pore size of the dissolution pore and using a permeability calculation model. The device executes the above method. The method and device provided in the application can improve the accuracy of calculating the permeability of tight sandstone and reduce the use of cores.

Description

Technical Field

[0001] This invention relates to the field of tight oil and gas development technology, specifically to a method and apparatus for calculating the permeability of tight sandstone. Background Technology

[0002] Tight sandstone is a type of reservoir rock with very low porosity and permeability, making exploration and development difficult. Tight sandstone permeability is a key parameter for evaluating tight sandstone reservoirs, and accurate calculation of tight sandstone permeability is of great guiding significance for evaluating tight oil and gas sweet spots and formulating scientific development methods.

[0003] Existing methods for calculating the permeability of tight sandstone mainly rely on high-pressure mercury intrusion porosimetry and nuclear magnetic resonance experiments, including the Coates model, the SDR (Schlumberger Doyle Laboratory) model, and the Pittman model, which can be expressed by the following formula:

[0004] Log(K) = A + B Log(φ) + C Log(f)

[0005] Where K represents the permeability of tight sandstone, φ represents porosity, and f is a variable. In the Coates model, SDR model, and Pittman model, f represents FFI / BVI (NMR free water to bound water saturation ratio), the geometric mean of the NMR T2 spectrum, and r, respectively. i (The pore throat radius corresponding to mercury saturation of i%). A, B, and C are the parameters fitted to the multiple linear regression equation.

[0006] The existing methods for calculating the permeability of tight sandstone have two main shortcomings: First, their application is ineffective. The pore structure of tight sandstone is extremely complex, and its strong heterogeneity leads to no clear correlation between porosity φ and permeability K, resulting in low accuracy when using the above formulas to calculate the permeability of tight sandstone. Second, they waste core samples. The existing methods require numerous high-pressure mercury intrusion porosimetry or nuclear magnetic resonance (NMR) experiments to obtain the pore structure parameters of the tight sandstone samples, upon which a permeability calculation model is established. To ensure the accuracy of the permeability calculation model, the number of analytical tests is usually greater than 10. However, core samples are typically only drilled from exploratory and appraisal wells, making core samples suitable for analytical testing very scarce. Summary of the Invention

[0007] To address the problems in the prior art, embodiments of the present invention provide a method and apparatus for calculating the permeability of dense sandstone, which can at least partially solve the problems existing in the prior art.

[0008] On the one hand, this invention proposes a method for calculating the permeability of tight sandstone, including:

[0009] A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency.

[0010] Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage.

[0011] The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

[0012] The acquisition of the pore size distribution curve of the dissolution pores in the dense sandstone sample includes:

[0013] The response is based on scanning electron microscopy imaging experiments performed on the dense sandstone sample to obtain an image of the dense sandstone sample. The ImageJ software is used to calculate the pore size distribution curve of the dissolution pores.

[0014] Prior to the step of obtaining an image of the tight sandstone sample based on a scanning electron microscopy imaging experiment performed on the tight sandstone sample, the method for calculating the permeability of the tight sandstone further includes:

[0015] The dense sandstone sample was preprocessed, and an image of the dense sandstone sample was obtained in response to a scanning electron microscope imaging experiment based on the preprocessed dense sandstone sample.

[0016] The step of obtaining the cumulative frequency distribution curve of the dissolution pits based on the pore size distribution curve includes:

[0017] Based on the pore size distribution curve of the etched pores, the proportion of pores with a diameter less than or equal to the preset diameter is statistically analyzed to obtain the cumulative proportion of pores from the smallest diameter to the preset diameter. The cumulative proportion is used as the cumulative frequency, and the pore size of the etched pores corresponding to the cumulative frequency is constructed.

[0018] The step of calculating the permeability of tight sandstone based on the upper limit and lower limit of the critical pore diameter of the dissolution pores and using a permeability calculation model with predetermined model parameters includes:

[0019] The permeability of tight sandstone is calculated using the permeability calculation model represented by the following expression:

[0020] logKCal =AlogR Cri-U +BlogR Cri-D +C

[0021] Among them, K Cal R represents the permeability of the dense sandstone. Cri-U R is the upper limit of the critical pore diameter of the dissolution hole. Cri-D Let A be the lower limit of the critical pore diameter of the dissolution pore, B be the first fitting coefficient corresponding to the upper limit of the critical pore diameter of the dissolution pore, and C be a constant.

[0022] Determining the model parameters includes:

[0023] The first fitting coefficient, the second fitting coefficient, and the constant are fitted according to the experimental parameters required by the pre-constructed permeability calculation model to obtain the model parameters.

[0024] The first preset percentage is 90%, and the second preset percentage is 10%.

[0025] On one hand, the present invention proposes a device for calculating the permeability of tight sandstone, comprising:

[0026] The acquisition unit is used to acquire the pore size distribution curve of the dissolution pores in the dense sandstone sample, and to acquire the cumulative frequency distribution curve of the dissolution pores based on the pore size distribution curve; the cumulative frequency distribution curve of the dissolution pores reflects the mapping relationship between the pore size and the cumulative frequency.

[0027] The determining unit is used to calculate a first product between the maximum cumulative frequency and a first preset percentage, and to calculate a second product between the maximum cumulative frequency and a second preset percentage, and to determine an upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product and a lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product according to the mapping relationship; the first preset percentage is greater than the second preset percentage;

[0028] The calculation unit is used to calculate the permeability of tight sandstone based on the upper limit of the critical pore diameter of the dissolution pore and the lower limit of the critical pore diameter of the dissolution pore, and using a permeability calculation model with predetermined model parameters.

[0029] In another aspect, embodiments of the present invention provide an electronic device, including: a processor, a memory, and a bus, wherein,

[0030] The processor and the memory communicate with each other via the bus;

[0031] The memory stores program instructions that can be executed by the processor, and the processor can execute the following methods by calling the program instructions:

[0032] A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency.

[0033] Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage.

[0034] The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

[0035] This invention provides a non-transitory computer-readable storage medium, comprising:

[0036] The non-transitory computer-readable storage medium stores computer instructions that cause the computer to perform the following methods:

[0037] A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency.

[0038] Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage.

[0039] The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

[0040] The method and apparatus for calculating the permeability of tight sandstone provided in this invention obtains the pore size distribution curve of a tight sandstone sample, and obtains the cumulative frequency distribution curve of the pores based on the pore size distribution curve. The cumulative frequency distribution curve reflects the mapping relationship between the pore size and the cumulative frequency. A first product between the maximum cumulative frequency and a first preset percentage is calculated, and a second product between the maximum cumulative frequency and a second preset percentage is calculated. Based on the mapping relationship, an upper limit value of the critical pore size corresponding to the first product and a lower limit value of the critical pore size corresponding to the second product are determined. The first preset percentage is greater than the second preset percentage. Based on the upper limit value and the lower limit value of the critical pore size, and using a permeability calculation model with predetermined model parameters, the permeability of tight sandstone is calculated, which can improve the accuracy of calculating the permeability of tight sandstone and reduce the use of core samples. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0042] Figure 1 This is a flowchart illustrating a method for calculating the permeability of dense sandstone according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the aperture distribution and cumulative distribution curves provided in an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram showing the intersection of experimentally measured permeability and the upper limit of the critical pore diameter of the dissolution pores provided in the embodiments of the present invention.

[0045] Figure 4 This is a schematic diagram showing the intersection of experimentally measured permeability and the lower limit of critical pore diameter for dissolution pores provided in an embodiment of the present invention.

[0046] Figure 5 This is a schematic diagram showing the intersection of model-calculated permeability and experimentally measured permeability provided in an embodiment of the present invention.

[0047] Figure 6 This is a schematic diagram of the structure of a dense sandstone permeability calculation device provided in an embodiment of the present invention.

[0048] Figure 7 This is a schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0050] Figure 1 This is a flowchart illustrating a method for calculating the permeability of tight sandstone according to an embodiment of the present invention, as shown below. Figure 1 As shown, the method for calculating the permeability of tight sandstone provided in this embodiment of the invention includes:

[0051] Step S1: Obtain the pore size distribution curve of the dense sandstone sample, and obtain the cumulative frequency distribution curve of the pores based on the pore size distribution curve; the cumulative frequency distribution curve of the pores reflects the mapping relationship between the pore size and the cumulative frequency.

[0052] Step S2: Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Determine the upper limit of the critical pore diameter of the dissolution hole corresponding to the first product and the lower limit of the critical pore diameter of the dissolution hole corresponding to the second product based on the mapping relationship; the first preset percentage is greater than the second preset percentage.

[0053] Step S3: Calculate the permeability of the tight sandstone based on the upper limit of the critical pore diameter of the dissolution pore and the lower limit of the critical pore diameter of the dissolution pore, and using a permeability calculation model with predetermined model parameters.

[0054] In step S1 above, the device acquires the pore size distribution curve of the dense sandstone sample, and obtains the cumulative frequency distribution curve of the pores based on the pore size distribution curve; the cumulative frequency distribution curve reflects the mapping relationship between the pore size and the cumulative frequency. The device can be a computer device that performs this method. It should be noted that the acquisition and analysis of data involved in this embodiment of the invention are authorized by the user. The pore size distribution curve is explained as follows:

[0055] This curve typically represents the proportion or number of dissolution pores of different sizes. It shows the size of the pores and the corresponding number or volume distribution of the pores, usually with the pore size on the horizontal axis and the number or proportion of pores on the vertical axis.

[0056] The method for obtaining the pore size distribution curve of the dissolution pores in the dense sandstone sample includes:

[0057] The response is based on scanning electron microscopy (SEM) imaging experiments performed on the dense sandstone sample, obtaining an image of the dense sandstone sample. ImageJ software is then used to calculate the pore size distribution curve of the dissolution pores from the image. The main functions of ImageJ software are as follows:

[0058] Image stack functionality: Supports stacking multiple images in a single window using multiple threads for parallel processing.

[0059] Plugin and macro support: It has an open structure, supports user-defined plugins and macros, and is highly extensible.

[0060] Geometric feature analysis: It can calculate a series of geometric features of the object under analysis within a selected area, such as length, angle, perimeter, area, etc.

[0061] Specifically, backscattered two-dimensional large-area scanning electron microscopy (SEM) imaging experiments can be performed on dense sandstone samples to obtain images of the samples. The backscattered SEM experimental conditions are: temperature 25℃ and pressure 0.101 MPa.

[0062] The process of performing scanning electron microscopy imaging experiments on dense sandstone samples is described below:

[0063] Sample preparation: First, the dense sandstone sample needs to be cut to an appropriate size for scanning electron microscopy (SEM) observation. The sample surface needs to be polished and cleaned to reduce surface roughness and ensure image quality.

[0064] Coating treatment: Since sandstone samples usually have low conductivity, it may be necessary to coat the sample surface with a thin metal (such as gold or carbon) coating to enhance conductivity and thus avoid charge accumulation during electron microscopy observation.

[0065] Sample mounting: Mount the prepared sample onto the sample holder of the scanning electron microscope, ensuring that the sample is stable and in the proper position to obtain clear images.

[0066] Adjusting electron microscope parameters: Adjust the working voltage, beam current intensity, scanning mode, and other parameters of the electron microscope according to the characteristics of the sample to obtain the best imaging effect.

[0067] Imaging: The scanning electron microscope is activated, and the sample surface is scanned by an electron beam to collect secondary electrons and backscattered electrons emitted from the sample surface, generating a high-resolution image.

[0068] Data analysis: The acquired images can be used to analyze the microstructure of dense sandstone, such as pore characteristics, grain morphology, and distribution. This information helps in understanding the physical and chemical properties of the sandstone.

[0069] Results Recording: Finally, the imaging results and analysis data are recorded to form an experimental report for subsequent research and application.

[0070] The pore size distribution curve of the dissolution pores can be obtained using ImageJ software by following these steps:

[0071] Preparing images of dense sandstone samples:

[0072] Use a microscope to take images of the etched holes, ensuring the images are clear and have a sufficiently high resolution.

[0073] Import images:

[0074] Open ImageJ software, select "File" > "Open" to import the captured image.

[0075] Convert to grayscale image:

[0076] If the image is in color, you can select "Image" > "Type" > "8-bit" to convert it to a grayscale image.

[0077] Binarization:

[0078] Use "Image" > "Adjust" > "Threshold" to select an appropriate threshold to binarize the image, making the holes black and the background white. Adjust the slider and click "Apply" to apply the threshold.

[0079] Noise removal:

[0080] If there is noise in the image, you can use "Process" > "Filters" > "Median" or "GaussianBlur" to smooth the image and remove small noise spots.

[0081] Particle analysis:

[0082] On the binarized image, select "Analyze" > "Analyze Particles". In the pop-up dialog box, set appropriate size and roundness ranges to ensure that only holes are analyzed. Check "Show outlines" to view the outlines of the holes.

[0083] Record aperture data:

[0084] After the analysis is complete, ImageJ will generate a results window that records the area and other information for each hole. The pore size data can be extracted from this window (the pore size can be calculated from the area, and is typically estimated using the formula: pore diameter = 2 × sqrt(area / π)).

[0085] Plot the aperture distribution curve:

[0086] Export the results to software such as Excel, calculate the frequency corresponding to each aperture, and use Excel to draw a histogram to generate the aperture distribution curve.

[0087] Analysis and Explanation:

[0088] Based on the pore size distribution curve, the characteristics of the dissolution pores can be further analyzed, such as the uniformity of pore size distribution and the pore size range.

[0089] The cumulative frequency distribution curve of the dissolution pits is explained as follows:

[0090] This curve represents the proportion of holes with a diameter less than or equal to a specific size out of the total number of holes by summing up the aperture distribution curves. It shows the cumulative number or proportion of holes from the smallest aperture to a specific aperture, usually with aperture size on the horizontal axis and cumulative frequency on the vertical axis.

[0091] Aperture distribution curves reflect the individual distribution of pores, while cumulative frequency distribution curves reflect the cumulative characteristics of pore size. They provide different information but can complement each other.

[0092] The step of obtaining the cumulative frequency distribution curve of the dissolution pits based on the pore size distribution curve includes:

[0093] Based on the pore size distribution curve, the proportion of pores with a diameter less than or equal to a preset diameter is statistically analyzed to obtain the cumulative proportion of pores from the smallest diameter to the preset diameter. This cumulative proportion is used as the cumulative frequency, and a pore size corresponding to the cumulative frequency is constructed. The preset diameter refers to a preset pore size, which can correspond to a specific pore size mentioned above.

[0094] A cumulative frequency distribution curve for dissolution pores is a statistical chart used to describe the size distribution characteristics of dissolution pores (or voids) in a material. This curve allows for a visual observation of the distribution of dissolution pores of different sizes throughout the sample. The cumulative frequency distribution represents the cumulative proportion of pores in the sample that are smaller than or equal to a specific pore size, usually expressed as a percentage.

[0095] Drawing such a curve typically requires the following steps:

[0096] Data collection: First, the size of the etched holes in the sample needs to be measured and the diameter of each hole recorded.

[0097] Data processing: Sort the measurement data by aperture size and calculate the frequency of occurrence of each aperture.

[0098] Cumulative frequency calculation: For each aperture, calculate the total number of apertures smaller than or equal to that aperture, and then calculate the cumulative frequency.

[0099] Plot the curve: Plot the cumulative frequency distribution curve with aperture as the x-axis and cumulative frequency as the y-axis.

[0100] By analyzing the cumulative frequency distribution curve of dissolution pores, researchers can obtain important material properties such as porosity and pore size distribution characteristics, which is of great significance for the performance evaluation and application of materials.

[0101] Prior to the step of obtaining an image of the tight sandstone sample based on a scanning electron microscopy imaging experiment performed on the tight sandstone sample, the method for calculating the permeability of the tight sandstone further includes:

[0102] The dense sandstone sample is preprocessed, and an image of the dense sandstone sample is obtained based on a scanning electron microscope imaging experiment performed on the preprocessed dense sandstone sample. The preprocessing of the dense sandstone sample may specifically include:

[0103] The dense sandstone sample was subjected to oil / salt washing, mechanical grinding, and argon ion polishing in sequence. The oil / salt washing treatment is described as follows:

[0104] a. First, place the sample into a high-temperature and high-pressure oil washing instrument and use organic solvents to wash away the residual oil and mud in the core.

[0105] b. Then, place the washed oil sample into a crucible, repeatedly add distilled water and boil to wash away the residual salt in the sample;

[0106] c. Finally, place the salt-washed sample into an oven and raise the temperature to 100℃ to remove the water from the sample.

[0107] The mechanical grinding process is explained below:

[0108] The flatness of mechanical grinding should be less than 1µm.

[0109] The argon ion spectrophotometry process is explained below:

[0110] The maximum diameter of the sample in the argon ion cutting experiment was 38 mm, and the maximum diameter of the processed area was 25 mm.

[0111] In step S2 above, the device calculates a first product between the maximum cumulative frequency and a first preset percentage, and a second product between the maximum cumulative frequency and a second preset percentage. Based on the mapping relationship, it determines the upper limit of the critical pore diameter corresponding to the first product and the lower limit of the critical pore diameter corresponding to the second product; the first preset percentage is greater than the second preset percentage. The first and second preset percentages can be set independently according to actual conditions; for example, the first preset percentage can be selected as 90%, and the second preset percentage can be selected as 10%. Figure 2As shown, the upper limit of the critical pore diameter for dissolution pores is 595.2 nm, and the lower limit of the critical pore diameter for dissolution pores is 82.7 nm.

[0112] There is a close relationship between the critical pore size limit of dissolution pores and the permeability of dense sandstone. As dissolution pores form, an increase in pore size leads to an increase in rock permeability. Specifically:

[0113] Pore ​​size: Larger dissolution pores can more effectively connect with surrounding pores, thereby improving the fluid flow in the rock and thus increasing permeability.

[0114] Critical pore size limit: The critical pore size refers to the pore size at which, under certain conditions, the pore structure begins to significantly affect the fluid flow properties. When the pore size of the dissolution pores reaches or exceeds this critical value, the permeability will increase rapidly.

[0115] Influence of porosity: Dense sandstone has low original porosity. Dissolution can significantly change its pore structure, increase porosity, and thus improve permeability.

[0116] Dissolution mechanism: The dissolution process mainly leads to increased porosity through chemical reactions and physical erosion. The better the connectivity of such pores, the stronger the fluid flow capacity.

[0117] Mechanical properties of rocks: The mineral composition, structure and mechanical properties of sandstone can also affect the formation and development of dissolution pores, and thus affect its permeability.

[0118] In summary, the critical pore size limit of dissolution pores is closely related to the permeability of tight sandstone, mainly manifested in the fact that increasing pore size and improving pore connectivity can significantly increase permeability. In practical applications, understanding the relationship between these two factors is of great significance for predicting and improving the exploitation and management of resources such as oil and gas and groundwater.

[0119] In step S3 above, the device calculates the permeability of tight sandstone based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters. The calculation of the permeability of tight sandstone based on the upper and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters, includes:

[0120] The permeability of tight sandstone is calculated using the permeability calculation model represented by the following expression:

[0121] logK Cal =AlogR Cri-U +BlogR Cri-D +C

[0122] Among them, K CalR represents the permeability of the dense sandstone. Cri-U R is the upper limit of the critical pore diameter of the dissolution hole. Cri-D Let A be the lower limit of the critical pore diameter of the dissolution pore, B be the first fitting coefficient corresponding to the upper limit of the critical pore diameter of the dissolution pore, and C be a constant. Figure 3 As shown, the experimentally measured permeability is related to the upper limit of the critical pore size R of the dissolution pores. Cri-U They have a good correlation, with a correlation coefficient R. 2 It is 0.8293; for example Figure 4 As shown, the permeability K was measured experimentally. Exp The lower limit of the critical pore diameter R of the dissolution pore Cri-D They have a good correlation, with a correlation coefficient R. 2 The value is 0.8527, therefore, a permeability calculation model can be established based on these two parameters.

[0123] Determining the model parameters includes:

[0124] The model parameters are obtained by fitting the first fitting coefficient, the second fitting coefficient, and the constant to the experimental parameters required by the pre-constructed permeability calculation model. The experimental parameters are shown in Table 1.

[0125] Table 1

[0126]

[0127]

[0128] Based on the data in Table 1, the fitting coefficients A and B, and the constant C were determined to be 0.5111, -1.2684, and 1.1531, respectively.

[0129] Therefore, the penetration rate calculation model can be expressed as:

[0130] logK Cal =0.5111logR Cri-U -1.2684logR Cri-D +1.1531

[0131] like Figure 5 The figure shows the crossover curve between the permeability calculated by the model and the permeability measured experimentally, with a correlation coefficient R. 2 The correlation coefficient is as high as 0.9772, indicating a very strong correlation, and the mean absolute error is only 13.6%, which proves the computational accuracy of the model.

[0132] The permeability calculation method for dense sandstone provided in this invention quantitatively characterizes the pore size distribution range of dissolution pores by conducting backscattered two-dimensional large-area scanning electron microscopy imaging experiments on dense sandstone samples. Based on the quantitative contribution of the upper and lower limits of the critical pore size of dissolution pores to permeability, a permeability calculation model is constructed, which greatly improves the accuracy of permeability calculation.

[0133] The method for calculating the permeability of tight sandstone provided in this invention involves obtaining a pore size distribution curve of a tight sandstone sample, and then obtaining a cumulative frequency distribution curve of the pores based on the pore size distribution curve. The cumulative frequency distribution curve reflects the mapping relationship between the pore size and the cumulative frequency. A first product is calculated between the maximum cumulative frequency and a first preset percentage, and a second product is calculated between the maximum cumulative frequency and a second preset percentage. Based on the mapping relationship, an upper limit value for the critical pore size of the pores corresponding to the first product and a lower limit value for the critical pore size of the pores corresponding to the second product are determined. The first preset percentage is greater than the second preset percentage. The permeability of the tight sandstone is calculated using a permeability calculation model with predetermined model parameters based on the upper and lower limits of the critical pore size of the pores. This method improves the accuracy of calculating the permeability of tight sandstone and reduces the use of core samples.

[0134] Furthermore, obtaining the pore size distribution curve of the dissolution pores in the dense sandstone sample includes:

[0135] The response is based on scanning electron microscopy imaging experiments performed on the dense sandstone sample, obtaining an image of the dense sandstone sample. The ImageJ software is then used to calculate the pore size distribution curve of the dissolution pores from the image. This can be referred to the above embodiments for further explanation and will not be repeated here.

[0136] Furthermore, prior to the step of obtaining an image of the tight sandstone sample based on a scanning electron microscopy imaging experiment performed on the tight sandstone sample, the method for calculating the permeability of the tight sandstone further includes:

[0137] The dense sandstone sample is preprocessed, and an image of the dense sandstone sample is obtained based on a scanning electron microscope imaging experiment performed on the preprocessed dense sandstone sample. This can be referred to the above embodiments for further explanation, and will not be repeated here.

[0138] Further, obtaining the cumulative frequency distribution curve of the dissolution pits based on the pore size distribution curve includes:

[0139] Based on the pore size distribution curve, the proportion of pores with a diameter less than or equal to a preset diameter is statistically analyzed to obtain the cumulative proportion of pores with diameters from the minimum to the preset diameter. This cumulative proportion is used as the cumulative frequency, and the pore size corresponding to the cumulative frequency is constructed. This can be referred to the above embodiment for explanation, and will not be repeated here.

[0140] Further, the step of calculating the permeability of tight sandstone based on the upper limit and lower limit of the critical pore diameter of the dissolution pores and using a permeability calculation model with predetermined model parameters includes:

[0141] The permeability of tight sandstone is calculated using the permeability calculation model represented by the following expression:

[0142] logK Cal =AlogR Cri-U +BlogR Cri-D +C

[0143] Among them, K Cal R represents the permeability of the dense sandstone. Cri-U R is the upper limit of the critical pore diameter of the dissolution hole. Cri-D Let A be the lower limit of the critical pore diameter of the dissolution pore, B be the first fitting coefficient corresponding to the upper limit of the critical pore diameter of the dissolution pore, and C be a constant. Refer to the above embodiments for further explanation; no further details will be provided.

[0144] Further, determining the model parameters includes:

[0145] The first fitting coefficient, the second fitting coefficient, and the constant are fitted to the experimental parameters required by the pre-constructed permeability calculation model to obtain the model parameters. This can be referred to the above embodiments for explanation, and will not be repeated here.

[0146] Furthermore, the first preset percentage is 90%, and the second preset percentage is 10%. This can be referred to the above embodiments for further explanation, and will not be repeated here.

[0147] Figure 6 This is a schematic diagram of the structure of a dense sandstone permeability calculation device provided in an embodiment of the present invention, as shown below. Figure 6 As shown, the tight sandstone permeability calculation device provided in this embodiment of the invention includes an acquisition unit 601, a determination unit 602, and a calculation unit 603, wherein:

[0148] The acquisition unit 601 is used to acquire the pore size distribution curve of the dissolution pores in the dense sandstone sample, and to acquire the cumulative frequency distribution curve of the dissolution pores based on the pore size distribution curve; the cumulative frequency distribution curve of the dissolution pores reflects the mapping relationship between the pore size and the cumulative frequency; the determination unit 602 is used to calculate the first product between the maximum cumulative frequency and the first preset percentage, and to calculate the second product between the maximum cumulative frequency and the second preset percentage, and to determine the upper limit value of the critical pore size of the dissolution pores corresponding to the first product and the lower limit value of the critical pore size of the dissolution pores corresponding to the second product based on the mapping relationship; the first preset percentage is greater than the second preset percentage; the calculation unit 603 is used to calculate the permeability of the dense sandstone based on the upper limit value of the critical pore size of the dissolution pores and the lower limit value of the critical pore size of the dissolution pores, and using a permeability calculation model with predetermined model parameters.

[0149] Specifically, the acquisition unit 601 in the device is used to acquire the pore size distribution curve of the dissolution pores in the dense sandstone sample, and to acquire the cumulative frequency distribution curve of the dissolution pores based on the pore size distribution curve; the cumulative frequency distribution curve of the dissolution pores reflects the mapping relationship between the pore size and the cumulative frequency; the determination unit 602 is used to calculate the first product between the maximum cumulative frequency and the first preset percentage, and to calculate the second product between the maximum cumulative frequency and the second preset percentage, and to determine the upper limit value of the critical pore size of the dissolution pores corresponding to the first product and the lower limit value of the critical pore size of the dissolution pores corresponding to the second product based on the mapping relationship; the first preset percentage is greater than the second preset percentage; the calculation unit 603 is used to calculate the permeability of the dense sandstone based on the upper limit value of the critical pore size of the dissolution pores and the lower limit value of the critical pore size of the dissolution pores, and using a permeability calculation model with predetermined model parameters.

[0150] The tight sandstone permeability calculation device provided in this invention obtains the pore size distribution curve of a tight sandstone sample, and obtains the cumulative frequency distribution curve of the pores based on the pore size distribution curve. The cumulative frequency distribution curve reflects the mapping relationship between the pore size and the cumulative frequency. A first product between the maximum cumulative frequency and a first preset percentage is calculated, and a second product between the maximum cumulative frequency and a second preset percentage is calculated. Based on the mapping relationship, an upper limit value of the critical pore size corresponding to the first product and a lower limit value of the critical pore size corresponding to the second product are determined. The first preset percentage is greater than the second preset percentage. Based on the upper limit value and the lower limit value of the critical pore size, and using a permeability calculation model with predetermined model parameters, the permeability of the tight sandstone is calculated, which can improve the accuracy of calculating the permeability of tight sandstone and reduce the use of core samples.

[0151] Furthermore, the acquisition unit 601 is specifically used for:

[0152] The response is based on scanning electron microscopy imaging experiments performed on the dense sandstone sample to obtain an image of the dense sandstone sample. The ImageJ software is used to calculate the pore size distribution curve of the dissolution pores.

[0153] Furthermore, prior to the step of obtaining an image of the tight sandstone sample based on a scanning electron microscopy imaging experiment performed on the tight sandstone sample, the tight sandstone permeability calculation device is also used to:

[0154] The dense sandstone sample was preprocessed, and an image of the dense sandstone sample was obtained in response to a scanning electron microscope imaging experiment based on the preprocessed dense sandstone sample.

[0155] Furthermore, the acquisition unit 601 is specifically used for:

[0156] Based on the pore size distribution curve of the etched pores, the proportion of pores with a diameter less than or equal to the preset diameter is statistically analyzed to obtain the cumulative proportion of pores from the smallest diameter to the preset diameter. The cumulative proportion is used as the cumulative frequency, and the pore size of the etched pores corresponding to the cumulative frequency is constructed.

[0157] Furthermore, the computing unit 603 is specifically used for:

[0158] The permeability of tight sandstone is calculated using the permeability calculation model represented by the following expression:

[0159] logK Cal =AlogR Cri-U +BlogR Cri-D +C

[0160] Among them, K Cal R represents the permeability of the dense sandstone. Cri-U R is the upper limit of the critical pore diameter of the dissolution hole. Cri-D Let A be the lower limit of the critical pore diameter of the dissolution pore, B be the first fitting coefficient corresponding to the upper limit of the critical pore diameter of the dissolution pore, and C be a constant.

[0161] Furthermore, the dense sandstone permeability calculation device is also used for:

[0162] The first fitting coefficient, the second fitting coefficient, and the constant are fitted according to the experimental parameters required by the pre-constructed permeability calculation model to obtain the model parameters.

[0163] Furthermore, the first preset percentage is 90%, and the second preset percentage is 10%.

[0164] The embodiments of the present invention provide a dense sandstone permeability calculation device that can be used to execute the processing flow of the above-described method embodiments. Its functions will not be repeated here, but can be referred to the detailed description of the above-described method embodiments.

[0165] Figure 7 This is a schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention, such as... Figure 7 As shown, the electronic device includes: a processor 701, a memory 702, and a bus 703;

[0166] The processor 701 and the memory 702 communicate with each other via the bus 703.

[0167] The processor 701 is used to call program instructions in the memory 702 to execute the methods provided in the above-described method embodiments, including, for example:

[0168] A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency.

[0169] Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage.

[0170] The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

[0171] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer can perform the methods provided in the above-described method embodiments, such as including:

[0172] A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency.

[0173] Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage.

[0174] The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

[0175] This embodiment provides a computer-readable storage medium storing a computer program that causes the computer to execute the methods provided in the above-described method embodiments, including, for example:

[0176] A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency.

[0177] Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage.

[0178] The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

[0179] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0180] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0181] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0182] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0183] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0184] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the permeability of tight sandstone, characterized in that, include: A pore size distribution curve of dissolution pores is obtained from a dense sandstone sample, and a cumulative frequency distribution curve of dissolution pores is obtained based on the pore size distribution curve; the cumulative frequency distribution curve of dissolution pores reflects the mapping relationship between pore size and cumulative frequency. Calculate the first product between the maximum cumulative frequency and the first preset percentage, and calculate the second product between the maximum cumulative frequency and the second preset percentage. Based on the mapping relationship, determine the upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product, and the lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product; the first preset percentage is greater than the second preset percentage. The permeability of tight sandstone is calculated based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters.

2. The method for calculating the permeability of tight sandstone according to claim 1, characterized in that, The method for obtaining the pore size distribution curve of the dissolution pores in the dense sandstone sample includes: The response is based on scanning electron microscopy imaging experiments performed on the dense sandstone sample to obtain an image of the dense sandstone sample. The ImageJ software is used to calculate the pore size distribution curve of the dissolution pores.

3. The method for calculating the permeability of tight sandstone according to claim 2, characterized in that, Prior to the step of obtaining an image of the tight sandstone sample based on a scanning electron microscopy imaging experiment performed on the tight sandstone sample, the method for calculating the permeability of the tight sandstone further includes: The dense sandstone sample was preprocessed, and an image of the dense sandstone sample was obtained in response to a scanning electron microscope imaging experiment based on the preprocessed dense sandstone sample.

4. The method for calculating the permeability of tight sandstone according to claim 1, characterized in that, The step of obtaining the cumulative frequency distribution curve of the dissolution pits based on the pore size distribution curve includes: Based on the pore size distribution curve of the etched pores, the proportion of pores with a diameter less than or equal to the preset diameter is statistically analyzed to obtain the cumulative proportion of pores from the smallest diameter to the preset diameter. The cumulative proportion is used as the cumulative frequency, and the pore size of the etched pores corresponding to the cumulative frequency is constructed.

5. The method for calculating the permeability of tight sandstone according to claim 1, characterized in that, The process of calculating the permeability of tight sandstone based on the upper limit and lower limit of the critical pore diameter of the dissolution pores, using a permeability calculation model with predetermined model parameters, includes: The permeability of tight sandstone is calculated using the permeability calculation model represented by the following expression: logK Cal =AlogR Cri-U +BlogR Cri-D +C Among them, K Cal R represents the permeability of the dense sandstone. Cri-U R is the upper limit of the critical pore diameter of the dissolution hole. Cri-D Let A be the lower limit of the critical pore diameter of the dissolution pore, B be the first fitting coefficient corresponding to the upper limit of the critical pore diameter of the dissolution pore, and C be a constant.

6. The method for calculating the permeability of tight sandstone according to claim 5, characterized in that, Determining the model parameters includes: The first fitting coefficient, the second fitting coefficient, and the constant are fitted according to the experimental parameters required by the pre-constructed permeability calculation model to obtain the model parameters.

7. The method for calculating the permeability of tight sandstone according to claim 1, characterized in that, The first preset percentage is 90%, and the second preset percentage is 10%.

8. A device for calculating the permeability of dense sandstone, characterized in that, include: The acquisition unit is used to acquire the pore size distribution curve of the dissolution pores in the dense sandstone sample, and to acquire the cumulative frequency distribution curve of the dissolution pores based on the pore size distribution curve; the cumulative frequency distribution curve of the dissolution pores reflects the mapping relationship between the pore size and the cumulative frequency. The determining unit is used to calculate a first product between the maximum cumulative frequency and a first preset percentage, and to calculate a second product between the maximum cumulative frequency and a second preset percentage, and to determine an upper limit value of the critical pore diameter of the dissolution hole corresponding to the first product and a lower limit value of the critical pore diameter of the dissolution hole corresponding to the second product according to the mapping relationship; the first preset percentage is greater than the second preset percentage; The calculation unit is used to calculate the permeability of tight sandstone based on the upper limit of the critical pore diameter of the dissolution pore and the lower limit of the critical pore diameter of the dissolution pore, and using a permeability calculation model with predetermined model parameters.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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