Matrix permeability calculation method and system

Abstract

A matrix permeability calculation method and system are disclosed. The method may include: establishing a natural gamma-neutron logging crossover diagram of sandstones of different particle sizes, determining the constraint limits of sandstones of different particle sizes; obtaining a rock particle size profile according to the natural gamma-neutron logging crossover diagram; determining the median particle size range corresponding to different particle sizes according to the rock particle size profile; establishing a crossover diagram according to the known median particle size, the constraint limit and the natural gamma, calculating the initial median particle size of the unknown sandstone; determining the median particle size of the unknown sandstone according to the median particle size range corresponding to the unknown sandstone and the initial median particle size; and calculating the matrix permeability according to the median particle size. The present invention realizes the evaluation of the matrix permeability by establishing a particle size profile calculation chart, calculating the median particle size, reflecting the influence of particle size on the matrix permeability, and combining the fracture permeability to accurately determine the permeability of the dual-porosity medium reservoir.

Description

Technical Field

[0001] The present invention relates to the field of petroleum exploration and development, and more specifically, to a matrix permeability calculation method and system. Background Art

[0002] Permeability is an important parameter to measure the permeability of reservoirs and plays a very important role in the exploration and development of oil and gas fields. Well logging evaluation of permeability is mostly achieved by establishing its relationship with other rock physical parameters to achieve indirect evaluation of permeability. For single-porous media, the pore space is mainly primary intergranular pores with good homogeneity. The earliest study on single-porous sandstone found that the logarithm of permeability has a linear relationship with porosity. However, this method did not consider the influence of pore structure changes and could not meet the accuracy requirements of permeability evaluation of complex reservoirs. Subsequently, the relationship between permeability, porosity and irreducible water saturation was proposed. The irreducible water saturation was used to reflect the changes in pore structure, which improved the accuracy of permeability. However, irreducible water saturation often requires nuclear magnetic logging data to obtain. The relationship between sandstone permeability and particle sorting and average particle size is given, but this method focuses on analyzing permeability from the perspective of particle distribution and weakens the influence of porosity. The KC formula is proposed based on capillary theory. This formula is well applied in lithic sandstone formations, but the KC constant and specific surface area are difficult to determine. In terms of dual-porosity media, rock pores are considered to be composed of two parts: matrix and fractures, where the matrix permeability is the same as that of the single-porous medium. Fracture permeability is affected by many factors, such as fracture porosity, aperture, density, inclination, and length. The models for solving fracture permeability after simplifying the fracture system mainly include the flat plate model, the Kazemi model, and the Warren-Root model. The fracture permeability of the parallel plate model is calculated by multiplying the square of the fracture porosity and the aperture. The Warren-Root model simplifies the dual-porosity medium reservoir into a geological model in which orthogonal fractures cut the bedrock block into a hexahedron. The fracture direction is consistent with the main permeability direction, and the fracture width is assumed to be a constant. The fracture network can be uniformly distributed or non-uniformly distributed. The use of a non-uniformly distributed fracture network can study the anisotropy of the fracture network or the changes in a certain direction. In summary, predecessors have conducted in-depth research on the permeability theoretical model and established a series of single-pore medium and dual-pore medium models, trying to establish the relationship between permeability and other rock physical parameters to achieve permeability evaluation. However, there are few studies on obtaining the lithology grain size profile through logging evaluation, and then using this profile as a constraint to constrain the median grain size result calculated by natural gamma logging, and finally using the calculated median grain size and porosity to jointly calculate the permeability. Therefore, it is necessary to develop a matrix permeability calculation method and system.

[0003] The information disclosed in the background technology section of the present invention is only intended to deepen the understanding of the general background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0004] The present invention proposes a matrix permeability calculation method and system, which can achieve matrix permeability evaluation by establishing a particle size profile calculation chart and calculating the median particle size, reflecting the influence of particle size on matrix permeability. Combined with fracture permeability, the permeability of dual-porosity medium reservoir can be accurately determined.

[0005] According to one aspect of the present invention, a method for calculating matrix permeability is proposed. The method may include: establishing a natural gamma-neutron logging crossplot of sandstones of different particle sizes to determine the constraint limits of sandstones of different particle sizes; obtaining a rock particle size profile based on the natural gamma-neutron logging crossplot; determining a particle size median range corresponding to different particle sizes based on the rock particle size profile; establishing a crossplot based on the known particle size median, the constraint limit and the natural gamma, and calculating the initial particle size median of the unknown sandstone; determining the particle size median of the unknown sandstone based on the particle size median range corresponding to the unknown sandstone and the initial particle size median; and calculating the matrix permeability based on the particle size median.

[0006] Preferably, determining the median grain size of the unknown sandstone based on the median grain size range corresponding to the unknown sandstone and the initial median grain size includes: judging whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone; if so, taking the initial median grain size as the median grain size of the unknown sandstone; if not, taking the boundary value with the smallest difference from the initial median grain size as the median grain size of the unknown sandstone.

[0007] Preferably, the matrix permeability is calculated by formula (1):

[0008]

[0009] Where K is the matrix permeability, MD is the median particle size, and a is the calculation parameter. is the porosity.

[0010] Preferably, the calculating of the matrix permeability according to the median particle size includes: establishing a three-phase fitting formula according to the known matrix permeability, the median particle size and the porosity, and then calculating the unknown matrix permeability.

[0011] Preferably, the method further comprises: calculating the dual-porosity medium permeability according to the matrix permeability and the fracture permeability.

[0012] Preferably, the fracture permeability is calculated by formula (2):

[0013]

[0014] Among them, K f is the fracture permeability, is the fracture porosity, b f is the crack opening.

[0015] Preferably, the dual-porosity medium permeability is calculated by formula (3):

[0016] K'=K+K f (3)

[0017] Among them, K' is the permeability of the dual-porosity medium and K is the matrix permeability.

[0018] According to another aspect of the present invention, a matrix permeability calculation system is proposed, characterized in that the system comprises: a memory storing computer executable instructions; a processor, wherein the processor runs the computer executable instructions in the memory to perform the following steps: establishing a natural gamma-neutron logging crossplot of sandstones of different grain sizes to determine the constraint limits of sandstones of different grain sizes; obtaining a rock grain size profile based on the natural gamma-neutron logging crossplot; determining a range of median grain sizes corresponding to different grain sizes based on the rock grain size profile; establishing a crossplot based on known median grain sizes, the constraint limits and natural gamma, and calculating an initial median grain size of an unknown sandstone; determining the median grain size of the unknown sandstone based on the range of median grain sizes corresponding to the unknown sandstone and the initial median grain size; and calculating matrix permeability based on the median grain size.

[0019] Preferably, determining the median grain size of the unknown sandstone based on the median grain size range corresponding to the unknown sandstone and the initial median grain size includes: judging whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone; if so, taking the initial median grain size as the median grain size of the unknown sandstone; if not, taking the boundary value with the smallest difference from the initial median grain size as the median grain size of the unknown sandstone.

[0020] Preferably, the matrix permeability is calculated by formula (1):

[0021]

[0022] Where K is the matrix permeability, MD is the median particle size, and a is the calculation parameter. is the porosity.

[0023] Preferably, the calculating of the matrix permeability according to the median particle size includes: establishing a three-phase fitting formula according to the known matrix permeability, the median particle size and the porosity, and then calculating the unknown matrix permeability.

[0024] Preferably, the method further comprises: calculating the dual-porosity medium permeability according to the matrix permeability and the fracture permeability.

[0025] Preferably, the fracture permeability is calculated by formula (2):

[0026]

[0027] Among them, K f is the fracture permeability, is the fracture porosity, b f is the crack opening.

[0028] Preferably, the dual-porosity medium permeability is calculated by formula (3):

[0029] K'=K+K f (3)

[0030] Among them, K' is the permeability of the dual-porosity medium and K is the matrix permeability.

[0031] The methods and apparatus of the present invention have other features and advantages that will be apparent from, or will be described in detail in, the accompanying drawings and subsequent detailed descriptions incorporated herein, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0033] Figure 1 A flow chart showing the steps of a matrix permeability calculation method according to the present invention.

[0034] Figure 2 A natural gamma-neutron logging cross-plot of sandstones with different grain sizes according to an embodiment of the present invention is shown.

[0035] Figure 3 A natural gamma-ray-neutron logging crossplot of a sandstone-mudstone section based on grain size classification according to an embodiment of the present invention is shown.

[0036] Figure 4 A schematic diagram of a sandstone-mudstone reservoir grain size profile according to an embodiment of the present invention is shown.

[0037] Figure 5 A cross-plot of median particle size and natural gamma according to an embodiment of the present invention is shown.

[0038] Figure 6 The figure shows an application effect diagram according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0040] Figure 1 A flow chart showing the steps of a matrix permeability calculation method according to the present invention.

[0041] In this embodiment, the matrix permeability calculation method according to the present invention may include: step 101, establishing a natural gamma-neutron logging crossplot of sandstones with different grain sizes, and determining the constraint limits of sandstones with different grain sizes; step 102, obtaining a rock grain size profile according to the natural gamma-neutron logging crossplot; step 103, determining a range of median grain sizes corresponding to different grain sizes according to the rock grain size profile; step 104, establishing a crossplot according to known median grain sizes, constraint limits and natural gamma, and calculating an initial median grain size of an unknown sandstone; step 105, determining a median grain size of the unknown sandstone according to the median grain size range corresponding to the unknown sandstone and the initial median grain size; step 106, calculating the matrix permeability according to the median grain size.

[0042] In one example, determining the median grain size of the unknown sandstone based on the median grain size range corresponding to the unknown sandstone and the initial median grain size includes: judging whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone; if so, taking the initial median grain size as the median grain size of the unknown sandstone; if not, taking the boundary value with the smallest difference from the initial median grain size as the median grain size of the unknown sandstone.

[0043] In one example, the matrix permeability is calculated by formula (1):

[0044]

[0045] Where K is the matrix permeability, MD is the median particle size, and a is the calculation parameter. is the porosity.

[0046] In one example, calculating the matrix permeability according to the median particle size includes: establishing a three-phase fitting formula according to known matrix permeability, median particle size, and porosity, and then calculating the unknown matrix permeability.

[0047] In one example, the method further includes: calculating the dual-porosity medium permeability according to the matrix permeability and the fracture permeability.

[0048] In one example, the fracture permeability is calculated by formula (2):

[0049]

[0050] Among them, K f is the fracture permeability, is the fracture porosity, b f is the crack opening.

[0051] In one example, the permeability of the dual-porosity medium is calculated by formula (3):

[0052] K'=K+K f (3)

[0053] Among them, K' is the permeability of the dual-porosity medium and K is the matrix permeability.

[0054] Specifically, for dual-porosity medium reservoirs, fracture permeability can be evaluated by fracture porosity and fracture opening calculated by imaging logging, and matrix permeability is closely related to porosity and rock pore structure. Rock particle size is one of the characterization methods of rock pore structure. For reservoirs with the same porosity but different particle sizes, the reservoir with finer particle size has higher bound water saturation, smaller pore throat radius, higher pore tortuosity, and lower permeability. For rock particles with finer particle size, the particle specific surface area is large, and it is easier to adsorb radioactive elements such as uranium, thorium, and potassium during deposition. In addition, rock particles with finer particle size are deposited at a location far away from the source, and have a longer contact time with radioactive elements than rocks with coarser particle size, resulting in higher natural gamma logging values ​​for rocks with finer particle size. At the same time, rocks with finer particle size have a small capillary radius, high capillary water content, and large specific surface area. The film water content on the surface of hydrophilic rock particles is high, resulting in higher neutron logging values. Therefore, natural gamma and neutron logging curves have a certain correlation with reservoir particle size. Core slice particle size analysis experiments, core observations, and logging particle size analysis can provide relatively accurate particle size classification, particle size median, particle size distribution standard deviation and other parameters. Therefore, the relationship between rock particle size classification, particle size median, and natural gamma and neutron logging can be established. The particle size evaluation based on logging data can be realized, and then the reservoir permeability calculation can be realized.

[0055] The matrix permeability calculation method according to the present invention may include:

[0056] The natural gamma-ray-neutron logging crossplot of sandstones with different grain sizes is established to determine the constraint limits of sandstones with different grain sizes.

[0057] In order to achieve continuous evaluation of the particle size of sandstone and mudstone profiles, the strata are first divided into five categories according to particle size: coarse sandstone, medium sandstone, fine sandstone, siltstone, and mudstone. Conventional logging data are used to determine the particle size type of reservoirs at different depths. From the analysis of the theoretical basis, it can be seen that the rock particle size has a good correlation with the natural gamma logging and neutron logging values, so the natural gamma logging and neutron logging are selected as the basic curves for lithology identification.

[0058] Thin section grain size test is the most effective way to determine rock grain size. This test can accurately obtain the number of particles, median grain size, mean grain size distribution, standard deviation of grain size distribution, rectangle mean, standard deviation, skewness, cusp and other parameters at the sampling point through image analysis or microscopic identification. This test is an effective way to obtain rock grain size information. However, the grain size of rock thin sections only reflects the grain size at the sampling point, with high vertical resolution. Natural gamma logging and neutron logging often reflect the comprehensive response of rocks in a depth section, with low vertical resolution. In formations with rapid vertical changes in lithology, the correspondence between the two is poor, and the results of rock grain size tests cannot be directly used to calibrate conventional logging results. Therefore, it is necessary to optimize the results of thin section grain size tests based on the results of core observation grain size analysis, and use the thin section data of the entire core section with relatively stable lithology and a large single lithology layer thickness as reliable data. Then, based on the core description or core physical property analysis data and the conventional logging response relationship, the core is returned to the original position, and the intersection chart of natural gamma and neutron logging is produced based on the reliable thin-section grain size experimental data after the return. Since the rock thin sections involved in the grain size analysis experiment are mostly located in the sandstone section, it is necessary to combine the logging data to determine the distribution range of natural gamma and neutron logging of siltstone and mudstone. Similarly, the siltstone and mudstone sections with stable logging lithology are selected, and the logging values ​​of this section are read to obtain the natural gamma-neutron logging intersection chart of sandstones of different grain sizes, and then determine the constraint limits of sandstones of different grain sizes.

[0059] According to the natural gamma-ray-neutron logging intersection diagram, the rock grain size evaluation results at different depths are determined, and the thin layers (thickness less than 0.5m) are merged to obtain the rock grain size profile, and then the median grain size range corresponding to different grain sizes is determined, namely, 1-2mm for boulder, 0.5-1mm for coarse sand, 0.25-0.5mm for medium sand, 0.125-0.25mm for fine sand, 0.0625-0.125mm for very fine sand, 0.0039-0.0312mm for silt sand, and <0.0039mm for clay.

[0060] The rock grain size experiment can obtain parameters such as the median rock grain size, the mean value of grain size distribution, the standard deviation of grain size distribution, the rectangular mean value, standard deviation, skewness, and cusp. The median grain size is selected as the link between lithology and permeability. There is a correlation between rock natural gamma, neutron logging and rock grain size. Since neutron logging is greatly affected by porosity, its correlation with grain size is poorer than that of gamma. Therefore, a relationship chart between the median rock grain size and natural gamma can be established based on the rock grain size experiment to achieve the evaluation of the median grain size logging. According to the known median grain size, constraint limits and natural gamma, an intersection diagram is established to calculate the initial median grain size of the unknown sandstone. Determine whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone. If so, the initial median grain size is taken as the median grain size of the unknown sandstone. If not, the boundary value with the smallest difference from the initial median grain size is taken as the median grain size of the unknown sandstone.

[0061] According to the median particle size, the Kozeny-Carman formula for uniform media proposed based on gross theory can be used to calculate the matrix permeability through formula (1). It is also possible to establish a three-phase fitting formula based on the known matrix permeability, median particle size, and porosity to calculate the unknown matrix permeability. The fracture permeability can then be calculated through formula (2), and the permeability of the dual-porosity medium can be calculated through formula (3) based on the matrix permeability and fracture permeability.

[0062] This method achieves the evaluation of matrix permeability by establishing a particle size profile calculation chart and calculating the median particle size, reflecting the influence of particle size on matrix permeability. Combined with fracture permeability, the permeability of dual-porosity medium reservoir can be accurately determined.

[0063] Application Examples

[0064] To facilitate understanding of the solution and effects of the embodiments of the present invention, a specific application example is given below. Those skilled in the art should understand that this example is only for facilitating understanding of the present invention, and any specific details thereof are not intended to limit the present invention in any way.

[0065] The matrix permeability calculation method of the present invention was applied to process a certain tight sandstone reservoir.

[0066] The natural gamma-ray-neutron logging crossplot of sandstones with different grain sizes is established to determine the constraint limits of sandstones with different grain sizes.

[0067] Figure 2 A natural gamma-neutron logging cross-plot of sandstones with different grain sizes according to an embodiment of the present invention is shown.

[0068] Figure 3 A natural gamma-ray-neutron logging crossplot of a sandstone-mudstone section based on grain size classification according to an embodiment of the present invention is shown.

[0069] First, the strata are divided into five categories according to their grain size: coarse sandstone, medium sandstone, fine sandstone, siltstone, and mudstone. Conventional logging data are used to determine the grain size type of reservoirs at different depths. Natural gamma and neutron logging are selected as the basic curves for lithology identification, and the natural gamma-neutron logging cross-plots of sandstones of different grain sizes are obtained, such as Figure 2 As shown in the figure, the horizontal axis is natural gamma, the vertical axis is neutron porosity, and different grayscales represent sandstones of different grain sizes. The lightest color is coarse sandstone, followed by medium sandstone, and then fine sandstone. Figure 2 It can be seen that coarse sandstone is mainly distributed in the range of low gamma and low neutrons, while fine sandstone shows the characteristics of relatively high gamma and high neutrons. This chart can be used to divide the grain size of sandstone. Similarly, select the siltstone and mudstone section with stable lithology in the logging, read the logging value of this section, and add it to Figure 2 On, such as Figure 3 As shown, the constraints of sandstones with different grain sizes are determined.

[0070] Figure 4 A schematic diagram of a sandstone-mudstone reservoir grain size profile according to an embodiment of the present invention is shown.

[0071] According to the natural gamma-ray-neutron logging cross-plot, the rock grain size evaluation results at different depths are determined, and thin layers (thickness less than 0.5m) are merged to obtain the rock grain size profile, such as Figure 4 As shown, the median particle size range corresponding to different particle sizes is determined, which is 1-2mm for boulder, 0.5-1mm for coarse sand, 0.25-0.5mm for medium sand, 0.125-0.25mm for fine sand, 0.0625-0.125mm for very fine sand, 0.0039-0.0312mm for silt sand and <0.0039mm for clay.

[0072] Figure 5 A median grain size-natural gamma cross-plot according to an embodiment of the present invention is shown, wherein the light-colored dots are median grain sizes obtained from rock grain size experiments, and the dark-colored dots are natural gamma values ​​corresponding to the boundaries of coarse, medium, and fine grains.

[0073] The rock grain size experiment can obtain the median rock grain size, the average value of grain size distribution, the standard deviation of grain size distribution, the average value of rectangle, standard deviation, skewness, cusp and other parameters. The median grain size is selected as the link between lithology and permeability. There is a correlation between rock natural gamma, neutron logging and rock grain size. Since neutron logging is greatly affected by porosity, its correlation with grain size is poorer than that of gamma. Therefore, the rock grain size median-natural gamma cross-plot can be established based on the rock grain size experiment, such as Figure 5As shown, the grain size median logging evaluation is realized, and the intersection diagram is established based on the known grain size median, constraint limit and natural gamma to calculate the initial grain size median of the unknown sandstone. It is judged whether the initial grain size median is within the grain size median range corresponding to the unknown sandstone. If so, the initial grain size median is taken as the grain size median of the unknown sandstone. If not, the boundary value with the smallest difference from the initial grain size median is taken as the grain size median of the unknown sandstone.

[0074] According to the median particle size, the Kozeny-Carman formula for uniform media proposed based on gross theory can be used to calculate the matrix permeability through formula (1). It is also possible to establish a three-phase fitting formula based on the known matrix permeability, median particle size, and porosity to calculate the unknown matrix permeability. The fracture permeability can then be calculated through formula (2), and the permeability of the dual-porosity medium can be calculated through formula (3) based on the matrix permeability and fracture permeability.

[0075] Figure 6 The application effect diagram of an embodiment of the present invention is shown. From left to right in the figure, there are productivity test channel, depth channel, lithology curve channel, resistivity channel, porosity curve channel, grain size profile channel, grain size median channel, porosity channel, matrix permeability channel, fracture permeability channel and total permeability channel. Figure 6 It can be seen that the calculated matrix permeability is controlled by porosity and, under the same porosity conditions, is negatively correlated with natural gamma, which better reflects the effect of particle size on matrix permeability. Combined with the fracture permeability calculated by imaging logging, the permeability of dual-porosity medium reservoirs can be determined more accurately.

[0076] In summary, the present invention achieves the evaluation of matrix permeability by establishing a particle size profile calculation chart and calculating the median particle size, which reflects the influence of particle size on matrix permeability. Combined with fracture permeability, the permeability of dual-porosity medium reservoir can be accurately determined.

[0077] Those skilled in the art should understand that the purpose of the above description of the embodiments of the present invention is only to exemplarily illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any given examples.

[0078] According to an embodiment of the present invention, a matrix permeability calculation system is provided, characterized in that the system comprises: a memory storing computer executable instructions; a processor, wherein the processor runs the computer executable instructions in the memory to perform the following steps: establishing a natural gamma-neutron logging crossover diagram of sandstones of different grain sizes to determine the constraint limits of sandstones of different grain sizes; obtaining a rock grain size profile according to the natural gamma-neutron logging crossover diagram; determining a range of median grain sizes corresponding to different grain sizes according to the rock grain size profile; establishing a crossover diagram according to known median grain sizes, constraint limits and natural gamma to calculate an initial median grain size of an unknown sandstone; determining the median grain size of the unknown sandstone according to the range of median grain sizes corresponding to the unknown sandstone and the initial median grain size; and calculating matrix permeability according to the median grain size.

[0079] In one example, determining the median grain size of the unknown sandstone based on the median grain size range corresponding to the unknown sandstone and the initial median grain size includes: judging whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone; if so, taking the initial median grain size as the median grain size of the unknown sandstone; if not, taking the boundary value with the smallest difference from the initial median grain size as the median grain size of the unknown sandstone.

[0080] In one example, the matrix permeability is calculated by formula (1):

[0081]

[0082] Where K is the matrix permeability, MD is the median particle size, and a is the calculation parameter. is the porosity.

[0083] In one example, calculating the matrix permeability according to the median particle size includes: establishing a three-phase fitting formula according to known matrix permeability, median particle size, and porosity, and then calculating the unknown matrix permeability.

[0084] In one example, the method further includes: calculating the dual-porosity medium permeability according to the matrix permeability and the fracture permeability.

[0085] In one example, the fracture permeability is calculated by formula (2):

[0086]

[0087] Among them, K f is the fracture permeability, is the fracture porosity, b f is the crack opening.

[0088] In one example, the permeability of the dual-porosity medium is calculated by formula (3):

[0089] K'=K+K f (3)

[0090] Among them, K' is the permeability of the dual-porosity medium and K is the matrix permeability.

[0091] This system establishes a particle size profile calculation chart, calculates the median particle size, and evaluates the matrix permeability, reflecting the effect of particle size on matrix permeability. Combined with fracture permeability, the permeability of dual-porosity medium reservoirs can be accurately determined.

[0092] Those skilled in the art should understand that the purpose of the above description of the embodiments of the present invention is only to exemplarily illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any given examples.

[0093] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for calculating matrix permeability, characterized in that: include: Establish the natural gamma-neutron logging crossplot of sandstones with different grain sizes and determine the constraint limits of sandstones with different grain sizes; Obtaining a rock grain size profile according to the natural gamma-ray-neutron logging crossplot; According to the rock grain size profile, determining the median range of grain sizes corresponding to different grain sizes; A median grain size-natural gamma cross-plot is established based on the known median grain size, the constraint limit and natural gamma to calculate the initial median grain size of the unknown sandstone; Determine the median grain size of the unknown sandstone according to the median grain size range corresponding to the unknown sandstone and the initial median grain size; Calculating matrix permeability based on the median particle size; Wherein, determining the median grain size of the unknown sandstone according to the median grain size range corresponding to the unknown sandstone and the initial median grain size includes: Determine whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone. If so, take the initial median grain size as the median grain size of the unknown sandstone. If not, take the boundary value with the smallest difference from the initial median grain size as the median grain size of the unknown sandstone.

2. The matrix permeability calculation method according to claim 1, wherein: The matrix permeability is calculated by formula (1): Where K is the matrix permeability, MD is the median particle size, and a is the calculation parameter. is the porosity.

3. The matrix permeability calculation method according to claim 1, wherein: Calculating the matrix permeability according to the median particle size includes: According to the known matrix permeability, the median particle size and the porosity, a three-phase fitting formula is established to further calculate the unknown matrix permeability.

4. The matrix permeability calculation method according to claim 2 or 3, wherein: Also includes: The dual-porosity medium permeability is calculated based on the matrix permeability and the fracture permeability.

5. The matrix permeability calculation method according to claim 4, wherein: The crack permeability is calculated by formula (2): Among them, K f is the fracture permeability, is the fracture porosity, b f is the crack opening.

6. The matrix permeability calculation method according to claim 5, wherein: The permeability of the dual-porosity medium is calculated by formula (3): K'=K+K f (3) Among them, K' is the permeability of the dual-porosity medium and K is the matrix permeability.

7. A matrix permeability calculation system, characterized in that: The system includes: a memory storing computer executable instructions; A processor, wherein the processor runs the computer executable instructions in the memory to perform the following steps: Establish the natural gamma-neutron logging crossplot of sandstones with different grain sizes and determine the constraint limits of sandstones with different grain sizes; Obtaining a rock grain size profile according to the natural gamma-ray-neutron logging crossplot; According to the rock grain size profile, determining the median range of grain sizes corresponding to different grain sizes; A median grain size-natural gamma cross-plot is established based on the known median grain size, the constraint limit and natural gamma to calculate the initial median grain size of the unknown sandstone; Determine the median grain size of the unknown sandstone according to the median grain size range corresponding to the unknown sandstone and the initial median grain size; Calculating matrix permeability based on the median particle size; Wherein, determining the median grain size of the unknown sandstone according to the median grain size range corresponding to the unknown sandstone and the initial median grain size includes: Determine whether the initial median grain size is within the median grain size range corresponding to the unknown sandstone. If so, take the initial median grain size as the median grain size of the unknown sandstone. If not, take the boundary value with the smallest difference from the initial median grain size as the median grain size of the unknown sandstone.

8. The matrix permeability calculation system according to claim 7, wherein: The matrix permeability is calculated by formula (1): Where K is the matrix permeability, MD is the median particle size, and a is the calculation parameter. is the porosity.

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