A method and system for obtaining permeability of a tight sand reservoir

Abstract

This invention provides a method and system for obtaining the permeability of tight sandstone reservoirs, belonging to the field of seismic exploration technology. First, the disconnected porosity is estimated. Then, the estimated disconnected porosity is used to correct the logging porosity. The corrected logging porosity is then fitted with permeability to obtain a fitted curve. Finally, the permeability is predicted based on the fitted curve. This invention is based on a tight sandstone petrological model, uses the obtained disconnected porosity to correct the logging porosity, and then uses the corrected logging porosity to predict and estimate permeability, thus improving the correlation between porosity and permeability in tight sandstone and increasing the accuracy of permeability prediction and estimation.

Description

Technical Field

[0001] This invention belongs to the field of seismic exploration technology, specifically relating to a method and system for obtaining the permeability of tight sandstone reservoirs. Background Technology

[0002] Permeability is a crucial parameter for evaluating and developing fluid mineral reservoirs, and it has always been a core issue addressed by geophysical logging. To predict permeability, researchers have made long-term and persistent efforts. Currently, the main methods for obtaining reservoir permeability include core laboratory measurements, wireline formation testing, drill pipe formation testing, well test permeability testing, and well log interpretation. Among these, well log interpretation is a relatively common method. Since porosity logging curves are generally quite complete, permeability interpretation methods in well log data typically utilize the theoretical relationship between porosity and permeability, employing statistical cross-plot analysis and fitting techniques to calculate permeability based on the porosity curve. Reservoir permeability is an important indicator of high-quality reservoirs; therefore, after obtaining the wellhead permeability fitting relationship, this relationship can be extended to other locations within the study area to predict reservoir permeability.

[0003] When predicting permeability in tight sandstone, the weak correlation between porosity and permeability characteristics can easily lead to inaccurate permeability predictions based on porosity. This weak correlation arises because of the well-developed intermittent porosity in tight sandstone. Therefore, when predicting permeability in tight clastic rocks, it is necessary to correct for the influence of intermittent porosity, improve the correlation between porosity and permeability, and use the corrected porosity to predict permeability, thereby improving the accuracy of permeability prediction. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and provide a method and system for obtaining the permeability of tight sandstone reservoirs. Based on rock physics models and existing conventional logging curves (P-wave, S-wave, porosity), the method correlates the correction of unconnected pores with the fitting process of the porosity-permeability relationship to obtain the prediction of the logging permeability curve, thereby improving the accuracy of logging interpretation of tight clastic rocks and providing a new practical method for permeability interpretation.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for obtaining the permeability of tight sandstone reservoirs. The method involves first estimating the non-connected porosity, correcting the logging porosity using the estimated non-connected porosity, fitting the corrected logging porosity to the permeability to obtain a fitting curve, and then using the fitting curve to predict the permeability.

[0007] A further improvement of the present invention is that:

[0008] The method specifically includes the following steps:

[0009] (1) Estimate the porosity of unconnected porosity;

[0010] (2) Correct the logging porosity, fit the corrected logging porosity with the permeability, and obtain the fitting curve;

[0011] (3) Based on the fitted curve, the permeability is predicted.

[0012] A further improvement of the present invention is that:

[0013] Step (1) Estimation of non-connected porosity, the operation includes:

[0014] The difference between the measured P-wave and S-wave velocities and the forward modeling predicted P-wave and S-wave velocities of saturated rock is used as the system energy of the simulated annealing method. By iteratively searching for the numerically optimal solution of disconnected porosity within a given range, the system energy in the simulated annealing method is minimized. The disconnected porosity obtained at this time is the estimated result.

[0015] A further improvement of the present invention is that:

[0016] The estimation of non-connected porosity includes the following steps:

[0017] (11) Select the search range for non-connected porosity and give the compaction coefficient according to the characteristics of the study area;

[0018] (12) Initialize the disconnected porosity and calculate the P-wave and S-wave velocities of saturated rock corresponding to the forward modeling prediction of the initial disconnected porosity.

[0019] (13) Perform the following calculations in each iteration of the simulated annealing algorithm:

[0020] a) Update the disconnected porosity and calculate the P-wave and S-wave velocities of saturated rock corresponding to the forward modeling prediction of the updated disconnected porosity;

[0021] b) The acceptance criteria in the simulated annealing algorithm are used to determine whether to accept the updated disconnected porosity;

[0022] c) Calculate the system energy J. If J is greater than the termination iteration threshold or the number of iterations has not yet reached the maximum number of iterations, return to step a).

[0023] (14) After convergence in step (13), the obtained non-connected porosity is the estimation result.

[0024] A further improvement of the present invention is that:

[0025] The specific calculation process for the P-wave and S-wave velocities of saturated rock predicted by the forward modeling is as follows:

[0026] Assuming the disconnected pores are completely saturated with water, and all oil or gas is contained in the connected pores, given the known porosity of the disconnected pores... Total porosity and water saturation S w Under the conditions, the oil or gas saturation S in the interconnected pores is obtained. He for:

[0027]

[0028] The water saturation S in the connected pores we for:

[0029]

[0030] This shows that when all the water in a rock exists in unconnected pores, S we If the value becomes 0, then the bulk modulus of the mixed fluid is:

[0031] K f =K w S we +K H (1-S we )

[0032] In the formula: K w K H These are the bulk moduli of water, oil, or gas, respectively.

[0033] Then, the equivalent elastic modulus of the saturated fluid is estimated using Wood's formula, and the equivalent density ρ of the fluid is estimated using the following formula. f :

[0034] ρ f =S w ρ w +(1-S w )ρ o

[0035] Where, ρ w and ρ o The densities of groundwater and oil are respectively.

[0036] Then calculate the density ρ of the saturated rock. sat :

[0037]

[0038] For connectivity porosity, ρ ma Density of the rock matrix;

[0039] Then calculate the modulus of the saturated rock:

[0040]

[0041] U sat =U dry

[0042] Among them, K sat U is the bulk modulus of saturated rock. sat K represents the shear modulus of saturated rock. dry U is the bulk modulus of the rock skeleton. dry K represents the shear modulus of the rock skeleton. ma K represents the bulk modulus of a rock matrix with discontinuous porosity. f The bulk modulus of the mixed fluid. For interconnected porosity;

[0043] Then, the P-wave and S-wave velocities of the saturated rock are calculated, i.e., the P-wave velocity VP predicted by the forward modeling. sat and transverse wave velocity VS sat :

[0044]

[0045]

[0046] A further improvement of the present invention is that:

[0047] The density of the rock matrix is ​​calculated as follows:

[0048] First, the longitudinal wave velocity of the rock matrix containing unconnected pores is calculated using formula (1), and its transverse wave velocity is estimated using Raymer's extended formula (2):

[0049]

[0050]

[0051] In the formula: V PS V SS For the corrected P-wave and S-wave velocities of the rock matrix; V Pm V Sm The initial P-wave and S-wave velocities of the rock matrix can be calculated from the moduli of the matrix's constituent minerals; V Pf The longitudinal wave velocity of fluid in unconnected pores is generally considered to be the presence of non-flowing formation water in unconnected pores. For non-connected porosity, Total porosity For connectivity porosity; ρ m The density of the initial matrix minerals; ρ fl The density of the fluid in the unconnected pores;

[0052] The effective compressive modulus C of the modified rock matrix is ​​obtained from the velocity value of the modified rock matrix through equation (3). s and shear modulus U s :

[0053] U s =ρ ms v 2 ss

[0054]

[0055] In the formula: ρ ms To correct the density of the matrix minerals;

[0056]

[0057] Among them, the bulk modulus K of the rock matrix considering the non-connected porosity ma =1 / C s The shear modulus of a rock matrix with non-connected porosity is U. ma =U s The density of the rock matrix is ​​ρ ma =ρ ms .

[0058] A further improvement of the present invention is that:

[0059] The bulk modulus and shear modulus of the rock skeleton are calculated as follows:

[0060]

[0061]

[0062] Among them, K dry U represents the bulk modulus of the rock skeleton. dry The shear modulus of the rock skeleton;

[0063] The formula visualizes the overall influence of consolidation characteristics and pore shape on the overall structure as a parameter Z, namely the compactness coefficient, which is obtained empirically.

[0064] A second aspect of the present invention provides a system for obtaining the permeability of tight sandstone reservoirs, the system comprising:

[0065] The non-connected porosity acquisition unit is used to estimate the non-connected porosity.

[0066] The curve fitting unit, connected to the disconnected porosity estimation unit, is used to correct the logging porosity using the estimated disconnected porosity, and then fit the corrected logging porosity with the permeability to obtain the fitting curve.

[0067] The permeability prediction unit, connected to the curve fitting unit, is used to predict permeability based on the fitted curve.

[0068] A further improvement of the present invention is that:

[0069] The system also includes:

[0070] The saturated rock P-wave and S-wave velocity acquisition unit is connected to the disconnected porosity acquisition unit and is used to calculate the P-wave and S-wave velocities of saturated rock predicted by forward modeling.

[0071] The rock matrix density acquisition unit is connected to the saturated rock P-wave and S-wave velocity acquisition unit and is used to calculate the rock matrix density.

[0072] The rock skeleton modulus acquisition unit, connected to the rock matrix density acquisition unit, is used to calculate the bulk modulus and shear modulus of the rock skeleton.

[0073] A third aspect of the present invention provides a computer-readable storage medium storing at least one computer-executable program, which, when executed by the computer, causes the computer to perform the steps in the method for obtaining the permeability of tight sandstone reservoirs described above.

[0074] Compared with the prior art, the beneficial effects of the present invention are:

[0075] This invention is based on a petrological model of tight sandstone, estimates the obtained non-connected porosity, corrects the logging porosity, and then uses the corrected logging porosity to predict and estimate permeability, thereby improving the correlation between porosity and permeability in tight sandstone and improving the accuracy of permeability prediction and estimation. Attached Figure Description

[0076] Figure 1 This is a flowchart of the method of the present invention;

[0077] Figure 2a It is a porosity curve obtained from a well logging test and a porosity curve after correction for non-connected porosity obtained from prediction.

[0078] Figure 2b It is the uncorrected fit between porosity and permeability;

[0079] Figure 2c It is a fitting relationship between porosity and permeability after correction for disconnected pores. Detailed Implementation

[0080] The present invention will now be described in further detail with reference to the accompanying drawings:

[0081] The technical problem this invention aims to solve is to improve the accuracy of well logging permeability interpretation and reservoir permeability estimation in tight sandstone. Utilizing a rock physics model that incorporates the effects of disconnected pores and the degree of compaction, and based on an optimized algorithm, disconnected porosity is predicted point-by-point. Finally, the obtained disconnected pore data is used to correct the porosity data for porosity-permeability fitting, thereby improving the accuracy of well logging interpretation and reservoir permeability estimation.

[0082] The known data required for constructing a rock physics model that incorporates the effects of disconnected pores and densification, and for predicting permeability (consistent with conventional methods, requiring no additional data, and readily available from well logging and literature) include: P-wave and S-wave logging data, total porosity logging data, quartz content logging data, clay mineral content logging data, density logging data, water saturation logging data, formation water modulus and density, quartz modulus and density, clay mineral modulus and density, and oil (gas) modulus and density in the reservoir.

[0083] This invention is based on a rock physics model and measured porosity. First, the non-connected porosity is estimated. Then, the logging porosity is corrected using the non-connected porosity (i.e., the logging porosity is subtracted from the non-connected porosity). The corrected porosity is then fitted with permeability to obtain a fitting curve. Finally, the permeability is predicted by combining the fitting curve.

[0084] The method of the present invention is illustrated in the following embodiments:

[0085]

Example 1

[0086] like Figure 1 As shown, the method includes the following steps:

[0087] (1) Calculation of the elastic modulus of the rock skeleton and the density of the rock matrix

[0088] Tight clastic reservoirs fall under the category of sandstone reservoirs, and their mixed minerals include quartz and clay minerals. Using the known quartz and clay mineral contents, the elastic modulus and density of the mixed minerals (i.e., the rock matrix) can be obtained using the VRH averaging model.

[0089] The VRH average model can be obtained from the literature. The correspondence between elastic modulus and P-wave and S-wave velocities can be easily found in the literature. Thus, the P-wave and S-wave velocities and densities of the mixed minerals, i.e., the rock matrix, can be obtained.

[0090] However, for dense clastic rocks, it is necessary to correct for non-connected pores. The corrected effective modulus is obtained using formulas (1) and (2). First, the longitudinal wave velocity of the rock matrix containing non-connected pores is calculated using formula (1), and its transverse wave velocity is estimated using Raymer extended formula (2).

[0091]

[0092]

[0093] In the formula: V PS V SS For the corrected P-wave and S-wave velocities of the rock matrix; V Pm V Sm The initial P-wave and S-wave velocities of the rock matrix can be calculated from the moduli of the matrix's constituent minerals; V Pf The longitudinal wave velocity of fluid in unconnected pores is generally considered to be the presence of non-flowing formation water in unconnected pores. For non-connected porosity, Total porosity For connectivity porosity; ρ m The density of the initial matrix minerals; ρ fl The density of the fluid in the unconnected pores;

[0094] From the velocity value of the modified rock matrix, the effective compressive modulus C of the modified rock matrix (including unconnected pores) can be obtained through equation (3). s and shear modulus U s :

[0095] U s =ρ ms v 2 ss

[0096]

[0097] In the formula: ρ ms To correct the density of the matrix minerals.

[0098]

[0099] Among them, the bulk modulus K of the rock matrix considering the non-connected porosity ma =1 / C s The shear modulus of a rock matrix with non-connected porosity is U. ma =U s ; Connectivity porosity is Non-connected porosity Total porosity The density of the rock matrix is ​​ρ ma =ρ ms ;

[0100] Next, to obtain the rock skeleton modulus, the following formula is used:

[0101]

[0102]

[0103] Among them, K dry U represents the bulk modulus of the rock skeleton. dry This represents the shear modulus of the rock skeleton.

[0104] In theory, the formula visualizes the overall effects of consolidation characteristics (densification degree) and pore shape as a parameter Z, i.e., the densification coefficient, which can be obtained empirically.

[0105] (2) Forward modeling to predict the P-wave velocity and S-wave velocity of saturated rock

[0106] First, calculate the fluid modulus and density in the pores using the following formulas to obtain K. f and ρ f .

[0107] Assuming the disconnected pores are completely saturated with water, and all oil or gas is contained in the connected pores, given the known porosity of the disconnected pores... Total porosity and water saturation S w Under these conditions, the oil (or gas) saturation S in the interconnected pores can be obtained. He for:

[0108]

[0109] The water saturation S in the connected pores we for:

[0110]

[0111] This shows that when all the water in a rock exists in unconnected pores, S we If the value becomes 0, then the bulk modulus of the mixed fluid is:

[0112] K f =K w S we +K H (1-S we (9)

[0113] In the formula: K w K H These are the bulk moduli of water, oil (or gas), respectively.

[0114] Then, the equivalent elastic modulus of the saturated fluid is estimated using Wood's formula (Mavko et al., 1996), and the equivalent density ρ of the fluid is estimated using the following formula. f :

[0115] ρ f =S w ρ w+(1-S w )ρ o (10)

[0116] Where, ρ w and ρ o These are the densities of groundwater and oil, respectively.

[0117] Then calculate the density ρ of the saturated rock. sat :

[0118]

[0119] For connectivity porosity, ρ ma Density of the rock matrix;

[0120] Then calculate the modulus of the saturated rock:

[0121]

[0122] U sat =U dry (13)

[0123] Among them, K sat U is the bulk modulus of saturated rock. sat K represents the shear modulus of saturated rock. dry U is the bulk modulus of the rock skeleton. dry K represents the shear modulus of the rock skeleton. ma K represents the bulk modulus of a rock matrix with discontinuous porosity. f The bulk modulus of the mixed fluid. For interconnected porosity;

[0124] Then the P-wave and S-wave velocities of saturated rock can be calculated, i.e., the P-wave and S-wave velocities predicted by forward modeling:

[0125]

[0126]

[0127] Among them, VP sat It is the P-wave velocity predicted by forward modeling, VS sat It is the shear wave velocity predicted by forward modeling.

[0128] (3) Obtaining the porosity of disconnected porosities

[0129] In the forward simulation process of steps (1)-(2), an additional parameter needs to be given: non-connected porosity; the following describes how to determine the optimal value of this parameter, i.e., the estimation result, through optimization algorithm.

[0130] The difference between the measured P-wave and S-wave velocities (the measured P-wave and S-wave velocities refer to the P-wave and S-wave velocities of the tight sandstone reservoir actually detected) and the P-wave and S-wave velocities of the saturated rock simulated by forward modeling (i.e. the P-wave and S-wave velocities of the saturated rock calculated in steps (1)-(2)) is taken as the system energy of the simulated annealing method. By iteratively searching for the numerical optimal solution of the disconnected porosity within a given range, the system energy in the simulated annealing method is minimized, and the disconnected porosity obtained at this time is the estimated result.

[0131] Please refer to the following process for details:

[0132] (31) Select the search range for non-connected porosity and give the compaction coefficient Z according to the characteristics of the study area;

[0133] Generally, 10% of the total porosity is used as the median of the search range, and the range can be expanded by 50% above and below the median. For example, if the total porosity is generally 0.1, then the search range for non-connected porosity is 0.005-0.015.

[0134] The density coefficient Z can generally be given as an empirical value based on the geological background, and the range is generally between 1 and 10.

[0135] (32) Initialize the disconnected porosity and calculate the saturated rock P-wave and S-wave velocities predicted by forward modeling based on steps (1)-(2).

[0136] Initializing the non-connected porosity involves randomly assigning a value within a defined search range. As shown above, the range is 0.005-0.015, so a random value can be assigned within this range, such as 0.008 or 0.011, etc.

[0137] (33) Perform the following calculations in each iteration of the simulated annealing algorithm:

[0138] a) Update the disconnected porosity and calculate the P-wave and S-wave velocities of saturated rock corresponding to the forward modeling prediction of the updated disconnected porosity;

[0139] Updating the disconnected porosity is a common method described in materials on simulated annealing algorithms. Specifically, it involves adding a certain value (which the simulated annealing algorithm itself determines) to the original disconnected porosity, thus changing the value of the disconnected porosity. This will not be elaborated upon here.

[0140] b) The acceptance criteria in the simulated annealing algorithm are used to determine whether to accept the updated disconnected porosity;

[0141] c) Calculate the system energy J. If J is greater than the termination iteration threshold or the number of iterations has not yet reached the maximum number of iterations, return to step a).

[0142] (34) After convergence in step (33), the obtained non-connected porosity is the estimation result.

[0143] Simulated annealing algorithm is existing technology and will not be described in detail here.

[0144] (4) Permeability prediction with correction for non-connected porosity.

[0145] After obtaining the non-connected porosity, the logging porosity (which refers to the total porosity of the tight sandstone reservoir actually detected) is subtracted from the non-connected porosity (i.e., the non-connected porosity estimated in step (3)) and then fitted with the permeability, or the empirical relationship is introduced (the empirical relationship is easily obtained from the core or theoretical model) to obtain a more accurate reservoir permeability prediction result and improve the accuracy of the well permeability curve interpretation.

[0146] The fitting method may be conventional linear fitting or nonlinear fitting, depending on the situation. The fitting algorithm is a commonly used mathematical method, which will not be elaborated here.

[0147] The empirical relationship uses an existing function, which will not be elaborated on here.

[0148] Permeability prediction specifically involves using the relationship fitted to this well to predict permeability based on porosity when there are no permeability measurements in other wells; or, after obtaining porosity data using the inversion method, the fitting relationship can be used to obtain permeability data and analyze reservoir permeability in areas without wells.

[0149] The method of the present invention will be further illustrated below through an application example.

[0150]

Example 2

[0151] The study area in the Sichuan Basin belongs to the category of tight sandstone reservoirs, with poor porosity and permeability conditions and a generally good porosity-permeability relationship, but some areas have a poor relationship. Figure 2a It is a porosity curve obtained from a well logging test and a porosity curve after correction for non-connected porosity obtained from prediction. Figure 2b It is the uncorrected fit between porosity and permeability, from Figure 2b The data shows a certain relationship between porosity and permeability, but there are some data points that deviate from the fitted relationship, indicating that the fitting of the porosity-permeability relationship has room for improvement. Figure 2c This is a fitted relationship between porosity and permeability after correction for disconnected pores. The correlation of the fitted relationship is very high, and it can be applied with relatively high confidence in the study area. Applying this fitted relationship can effectively improve the accuracy of permeability prediction and reservoir permeability estimation.

[0152] The present invention also provides a system for obtaining the permeability of tight sandstone reservoirs, and an embodiment of the system is as follows:

[0153]

Example 3

[0154] The system includes:

[0155] The non-connected porosity acquisition unit is used to estimate the non-connected porosity.

[0156] The curve fitting unit, connected to the disconnected porosity estimation unit, is used to correct the logging porosity using the estimated disconnected porosity, and then fit the corrected logging porosity with the permeability to obtain the fitting curve.

[0157] The permeability prediction unit, connected to the curve fitting unit, is used to predict permeability based on the fitted curve.

[0158] The system for obtaining the permeability of tight sandstone reservoirs also includes:

[0159] The saturated rock P-wave and S-wave velocity acquisition unit is connected to the disconnected porosity acquisition unit and is used to calculate the P-wave and S-wave velocities of saturated rock predicted by forward modeling.

[0160] The rock matrix density acquisition unit is connected to the saturated rock P-wave and S-wave velocity acquisition unit and is used to calculate the rock matrix density.

[0161] The rock skeleton modulus acquisition unit, connected to the rock matrix density acquisition unit, is used to calculate the bulk modulus and shear modulus of the rock skeleton.

[0162] The present invention also provides a computer-readable storage medium, embodiments of which are as follows:

[0163]

Example 4

[0164] The computer-readable storage medium stores at least one computer-executable program, which, when executed by the computer, causes the computer to perform the steps in the method for obtaining the permeability of tight sandstone reservoirs described above.

[0165] Finally, it should be noted that the above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the application methods and principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the methods described in the above specific embodiments of the present invention. Therefore, the methods described above are only preferred and have no limiting significance.

Claims

1. A method for obtaining the permeability of tight sandstone reservoirs, characterized in that, First, estimate the non-connected porosity. Then, use the estimated non-connected porosity to correct the logging porosity. Finally, use the corrected logging porosity to fit the permeability to obtain a fitting curve. Then, combine the fitting curve to predict the permeability. The method specifically includes the following steps: (1) Estimate the porosity of unconnected porosity; (2) Correct the logging porosity, fit the corrected logging porosity with the permeability, and obtain the fitting curve; (3) Based on the fitted curve, the permeability is predicted; The operation of estimating the non-connected porosity in step (1) includes: taking the difference between the measured P-wave and S-wave velocities and the P-wave and S-wave velocities of the saturated rock predicted by forward modeling as the system energy of the simulated annealing method; by iteratively searching for the numerical optimal solution of the non-connected porosity within a given range, so that the system energy in the simulated annealing method is minimized; and the non-connected porosity obtained at this time is the estimated result. The specific calculation process for the P-wave and S-wave velocities of saturated rock predicted by the forward modeling is as follows: Assuming the disconnected pores are completely saturated with water, and all oil or gas is contained in the connected pores, given the known porosity of the disconnected pores... Total porosity and water saturation S w Under the conditions, the oil or gas saturation in the interconnected pores is obtained. S He for: The water saturation in the connected pores S we for: This shows that when all the water in a rock exists in unconnected pores, S we If the value becomes 0, then the bulk modulus of the mixed fluid is: In the formula: K w , K H These are the bulk moduli of water, oil, or gas, respectively. Then, the equivalent elastic modulus of the saturated fluid is estimated using Wood's formula, and the equivalent density of the fluid is estimated using the following formula. ρ f : in, ρ w and ρ o The densities of groundwater and oil are respectively. Then calculate the density of the saturated rock. ρ sat : For connectivity porosity, ρ ma Density of the rock matrix; Then calculate the modulus of the saturated rock: in, K sat The bulk modulus of saturated rock. U sat The shear modulus of saturated rock. K dry The bulk modulus of the rock skeleton. U dry The shear modulus of the rock skeleton. K ma The bulk modulus of a rock matrix with non-connected porosity. K f The bulk modulus of the mixed fluid. For interconnected porosity; Then, the P-wave and S-wave velocities of the saturated rock are calculated, i.e., the P-wave velocity predicted by the forward modeling. VP sat and transverse wave velocity VS sat : ； The bulk modulus and shear modulus of the rock skeleton are calculated as follows: in, K dry The bulk modulus of the rock skeleton; U dry The shear modulus of the rock skeleton; U ma Shear modulus of rock matrix with non-connected porosity; The formula visualizes the overall influence of consolidation characteristics and pore shape on the overall structure as a parameter Z, namely the compactness coefficient, which is obtained empirically.

2. The method according to claim 1, characterized in that, The estimation of non-connected porosity specifically includes the following steps: (11) Select the search range for non-connected porosity and give the compaction coefficient according to the characteristics of the study area; (12) Initialize the disconnected porosity and calculate the P-wave and S-wave velocities of saturated rock corresponding to the forward modeling prediction of the initial disconnected porosity. (13) Perform the following calculations in each iteration of the simulated annealing algorithm: a) Update the disconnected porosity and calculate the P-wave and S-wave velocities of saturated rock corresponding to the forward modeling prediction of the updated disconnected porosity; b) The acceptance criteria in the simulated annealing algorithm are used to determine whether to accept the updated disconnected porosity; c) Calculate the system energy J. If J is greater than the termination iteration threshold or the number of iterations has not yet reached the maximum number of iterations, return to step a). (14) After convergence in step (13), the obtained non-connected porosity is the estimation result.

3. The method according to claim 1, characterized in that, The density of the rock matrix is ​​calculated as follows: First, the longitudinal wave velocity of the rock matrix containing unconnected pores is calculated using formula (1), and its transverse wave velocity is estimated using Raymer's extended formula (2): In the formula: V PS , V SS For the correction of the longitudinal and transverse wave velocities of the rock matrix; V Pm , V Sm The initial longitudinal and transverse wave velocities of the rock matrix can be calculated from the modulus of the matrix minerals. V Pf The longitudinal wave velocity of fluid in unconnected pores is generally considered to be the presence of non-flowing formation water in unconnected pores. For non-connected porosity, Total porosity For interconnected porosity; ρ m The density of the initial matrix minerals; ρ fl The density of the fluid in the unconnected pores; The effective compressive modulus of the modified rock matrix is ​​obtained from the velocity value of the modified rock matrix through equation (3). C s and shear modulus U s : In the formula: ρ ms To correct the density of the matrix minerals; Among them, the bulk modulus of the rock matrix considering the non-connected porosity K ma =1 / C s The shear modulus of a rock matrix with non-connected porosity is U ma = U s The density of the rock matrix is ρ ma = ρ ms .

4. A system for obtaining the permeability of tight sandstone reservoirs, characterized in that, For performing the method of obtaining the permeability of tight sandstone reservoirs as described in any one of claims 1-3, the system comprises: The non-connected porosity acquisition unit is used to estimate the non-connected porosity. The curve fitting unit, connected to the disconnected porosity estimation unit, is used to correct the logging porosity using the estimated disconnected porosity, and then fit the corrected logging porosity with the permeability to obtain the fitting curve. The permeability prediction unit, connected to the curve fitting unit, is used to predict permeability based on the fitted curve.

5. The system according to claim 4, characterized in that, The system also includes: The saturated rock P-wave and S-wave velocity acquisition unit is connected to the disconnected porosity acquisition unit and is used to calculate the P-wave and S-wave velocities of saturated rock predicted by forward modeling. The rock matrix density acquisition unit is connected to the saturated rock P-wave and S-wave velocity acquisition unit and is used to calculate the rock matrix density. The rock skeleton modulus acquisition unit, connected to the rock matrix density acquisition unit, is used to calculate the bulk modulus and shear modulus of the rock skeleton.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one computer-executable program, which, when executed by the computer, causes the computer to perform the steps of the method for obtaining the permeability of a tight sandstone reservoir as described in any one of claims 1-3.

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