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

Abstract

The application provides a method and system for determining the permeability of a tight sandstone reservoir. The method comprises: obtaining the porosity and pore throat radius distribution spectrum of the target reservoir; dividing the pore throat radius distribution spectrum of the target reservoir into two parts, i.e., a large-aperture part and a small-aperture part; determining the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part based on the pore throat radius distribution spectrum of the large-aperture part and the small-aperture part of the target reservoir; and determining the permeability of the target reservoir based on the ratio and the porosity of the target reservoir. The method can accurately determine the permeability of a reservoir in a tight sandstone reservoir with strong heterogeneity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of reservoir evaluation, in particular to a method and system for determining the permeability of tight sandstone reservoirs. BACKGROUND

[0002] Permeability is a key parameter reflecting the seepage capacity of a reservoir, and its value reflects the level of the seepage capacity of the reservoir and is closely related to the productivity of the reservoir. Generally speaking, the higher the permeability, the stronger the seepage capacity of the reservoir, and the higher the corresponding productivity, and vice versa. Therefore, accurate evaluation of the permeability of a reservoir is the key to solving the problems of effective reservoir identification and productivity prediction. Permeability is one of the key parameters that need to be accurately determined in reservoir evaluation.

[0003] So far, except for core experiments, there is no method that can directly use logging data to quantitatively determine the permeability of a reservoir. The existing methods for determining the permeability of a reservoir can be roughly divided into three categories: (1) using statistical regression to determine the permeability. This method is based on the porosity and permeability data of core experiments, uses empirical statistical methods to establish the corresponding relationship between porosity and permeability, and determines the permeability by combining the porosity. (2) using nuclear magnetic resonance logging to determine the permeability. This method first obtains parameters such as reservoir porosity, irreducible water saturation, and T2 geometric mean from nuclear magnetic resonance logging data, and then determines the permeability using the empirical SDR model or Timur model; (3) determining the permeability based on the flow unit theory. This method is mainly aimed at reservoirs with poor core porosity-permeability correlation due to complex pore structure. First, the reservoir is divided into several types using the flow unit difference, then for each type of reservoir, the core porosity-permeability relationship is established, and finally, based on the classification of the actual reservoir using the flow unit, the corresponding porosity-permeability relationship for each type of reservoir is substituted to determine the permeability of the reservoir. These methods can determine the permeability of specific reservoirs, but they are all empirical statistical methods based on core experiments, have regional limitations, and have low model accuracy, which cannot be widely applied. In addition, the establishment process of these models does not consider the influence and contribution of pore structure on the permeability of the reservoir.

[0004] Therefore, there is still a need to study new methods for accurately determining the permeability of a reservoir. SUMMARY

[0005] The purpose of the present application is to provide a method and system for determining the permeability of tight sandstone reservoirs.

[0006] In order to achieve the above purpose, the present application provides a method for determining the permeability of tight sandstone reservoirs, wherein the method comprises:

[0007] obtaining a porosity of the target reservoir;

[0008] obtaining a pore throat radius distribution spectrum of the target reservoir;

[0009] dividing the pore throat radius distribution spectrum of the target reservoir into a large pore diameter part and a small pore diameter part; wherein the corresponding permeability increases as the cumulative amplitude of the pore throat radius distribution of the large pore diameter part increases, and the corresponding permeability increases as the cumulative amplitude of the pore throat radius distribution of the small pore diameter part decreases;

[0010] determining a ratio of the cumulative amplitude of the pore throat radius distribution of the large pore diameter part to the cumulative amplitude of the pore throat radius distribution of the small pore diameter part of the target reservoir based on the pore throat radius distribution spectrum of the large pore diameter part and the pore throat radius distribution spectrum of the small pore diameter part of the target reservoir;

[0011] determining the permeability of the target reservoir based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large pore diameter part to the cumulative amplitude of the pore throat radius distribution of the small pore diameter part of the target reservoir and the porosity of the target reservoir.

[0012] In the above method, preferably, dividing the pore throat radius distribution spectrum of the target reservoir into a large pore diameter part and a small pore diameter part comprises:

[0013] obtaining a pore throat radius division threshold; wherein the large pore diameter part and the small pore diameter part obtained by dividing the pore throat radius distribution spectrum of the tight sandstone reservoir according to the pore throat radius division threshold satisfy: the corresponding permeability increases as the cumulative amplitude of the pore throat radius distribution of the large pore diameter part increases, and the corresponding permeability increases as the cumulative amplitude of the pore throat radius distribution of the small pore diameter part decreases;

[0014] dividing the pore throat radius distribution spectrum of the target reservoir into a large pore diameter part and a small pore diameter part based on the pore throat radius division threshold;

[0015] More preferably, obtaining the pore throat radius division threshold comprises:

[0016] 1) obtaining the pore throat radius distribution spectrum of a plurality of tight sandstone reservoir cores with known permeability;

[0017] 2) selecting a pore throat radius value, and dividing the pore throat radius distribution spectrum of each core into a large pore diameter part and a small pore diameter part according to the pore throat radius value, and analyzing the relationship between the cumulative amplitude of the pore throat radius distribution of the large pore diameter part and the permeability and the relationship between the cumulative amplitude of the pore throat radius distribution of the small pore diameter part and the permeability;

[0018] 3) repeating step 2), and taking the pore throat radius value corresponding to the best correlation between the cumulative amplitude of the pore throat radius distribution and the permeability as the pore throat radius division threshold;

[0019] More preferably, the pore throat radius division threshold is 0.4 μm.

[0020] In the method, preferably, the ratio of the cumulative amplitude of the large-pore portion pore throat radius distribution to the cumulative amplitude of the small-pore portion pore throat radius distribution of the target reservoir is determined based on the pore throat radius distribution spectrum of the large-pore portion of the target reservoir and the pore throat radius distribution spectrum of the small-pore portion of the target reservoir, comprising:

[0021] determining the cumulative amplitude of the large-pore portion pore throat radius of the target reservoir based on the pore throat radius distribution spectrum of the large-pore portion of the target reservoir;

[0022] determining the cumulative amplitude of the small-pore portion pore throat radius of the target reservoir based on the pore throat radius distribution spectrum of the small-pore portion of the target reservoir;

[0023] determining the ratio of the cumulative amplitude of the large-pore portion pore throat radius distribution to the cumulative amplitude of the small-pore portion pore throat radius distribution of the target reservoir based on the cumulative amplitude of the large-pore portion pore throat radius of the target reservoir and the cumulative amplitude of the small-pore portion pore throat radius of the target reservoir;

[0024] wherein,

[0025]

[0026] wherein, RC1 is the cumulative amplitude of the small-pore portion pore throat radius; RC2 is the cumulative amplitude of the large-pore portion pore throat radius; rc_dist(i) is the amplitude value corresponding to the i-th pore throat radius from small to large in the pore throat radius distribution spectrum; n is the order number of the pore throat radius corresponding to the boundary line of the large-pore portion and the small-pore portion in the pore throat radius distribution spectrum sorted from small to large; N is the total number of the pore throat radius values in the pore throat radius distribution spectrum; R c_ratio is the ratio of the cumulative amplitude of the large-pore portion pore throat radius distribution to the cumulative amplitude of the small-pore portion pore throat radius distribution.

[0027] In the method, preferably, the permeability of the target reservoir is determined based on the ratio of the cumulative amplitude of the large-pore portion pore throat radius distribution to the cumulative amplitude of the small-pore portion pore throat radius distribution of the target reservoir and the porosity of the target reservoir, comprising:

[0028] obtaining a permeability determination model; wherein the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the large-pore portion pore throat radius distribution to the cumulative amplitude of the small-pore portion pore throat radius distribution and the porosity;

[0029] determining the permeability of the target reservoir based on the ratio of the cumulative amplitude of the large-pore portion pore throat radius distribution to the cumulative amplitude of the small-pore portion pore throat radius distribution of the target reservoir and the porosity of the target reservoir, and using the permeability determination model;

[0030] More preferably, the obtaining the permeability determination model comprises:

[0031] obtaining permeability of the tight sandstone reservoir core of a plurality of known porosity, a ratio of a cumulative amplitude of the large-pore throat radius distribution to a cumulative amplitude of the small-pore throat radius distribution;

[0032] obtaining the permeability determination model based on the permeability, the porosity, the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution of each core;

[0033] More preferably, the permeability determination model is:

[0034]

[0035] wherein, K is the permeability, mD; is the porosity, %; R c_ratio is the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution; A and B are coefficients, A is preferably 0.1033, and B is preferably 0.8111.

[0036] The present application also provides a tight sandstone reservoir permeability determination system, wherein the system comprises:

[0037] a porosity obtaining module for obtaining the porosity of the target reservoir;

[0038] a pore throat radius distribution spectrum obtaining module for obtaining the pore throat radius distribution spectrum of the target reservoir;

[0039] a large and small pore size part dividing module for dividing the pore throat radius distribution spectrum of the target reservoir into a large pore size part and a small pore size part; wherein the corresponding permeability increases as the cumulative amplitude of the large-pore throat radius distribution increases, and the corresponding permeability increases as the cumulative amplitude of the small-pore throat radius distribution decreases;

[0040] a ratio obtaining module for determining the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution based on the pore throat radius distribution spectrum of the large-pore size part and the pore throat radius distribution spectrum of the small-pore size part of the target reservoir;

[0041] a permeability determination module for determining the permeability of the target reservoir based on the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution and the porosity of the target reservoir.

[0042] In the above system, preferably, the large and small pore size part dividing module comprises:

[0043] The threshold determination submodule is used to obtain a pore throat radius division threshold; wherein the large-aperture part and the small-aperture part obtained by dividing the pore throat radius distribution spectrum of the tight sandstone reservoir according to the pore throat radius division threshold satisfy: as the cumulative amplitude of the pore throat radius distribution of the large-aperture part increases, the corresponding permeability increases, and as the cumulative amplitude of the pore throat radius distribution of the small-aperture part decreases, the corresponding permeability increases;

[0044] The large-aperture part and the small-aperture part division submodule is used to divide the pore throat radius distribution spectrum of the target reservoir into a large-aperture part and a small-aperture part based on the pore throat radius division threshold;

[0045] More preferably, the threshold determination submodule comprises:

[0046] The first training data acquisition unit is used to obtain the pore throat radius distribution spectrum of a plurality of tight sandstone reservoir cores with known permeability;

[0047] The threshold determination unit is used to repeatedly select a pore throat radius value, divide the pore throat radius distribution spectrum of each core into a large-aperture part and a small-aperture part according to the pore throat radius value, analyze the relationship between the cumulative amplitude of the pore throat radius distribution of the large-aperture part and the permeability and the relationship between the cumulative amplitude of the pore throat radius distribution of the small-aperture part and the permeability, and take the pore throat radius value corresponding to the best correlation between the cumulative amplitude of the pore throat radius distribution and the permeability as the pore throat radius division threshold;

[0048] More preferably, the pore throat radius division threshold is 0.4 μm.

[0049] In the above system, preferably, the ratio acquisition module comprises:

[0050] The first cumulative amplitude determination submodule is used to determine the cumulative amplitude of the pore throat radius of the large-aperture part of the target reservoir based on the pore throat radius distribution spectrum of the large-aperture part of the target reservoir;

[0051] The second cumulative amplitude determination submodule is used to determine the cumulative amplitude of the pore throat radius of the small-aperture part of the target reservoir based on the pore throat radius distribution spectrum of the small-aperture part of the target reservoir;

[0052] The ratio determination submodule is used to determine the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part of the target reservoir based on the cumulative amplitude of the pore throat radius of the large-aperture part and the cumulative amplitude of the pore throat radius of the small-aperture part of the target reservoir;

[0053] wherein,

[0054]

[0055] In the formula, RC1 is the cumulative amplitude of the pore throat radius of the small-aperture part; RC2 is the cumulative amplitude of the pore throat radius of the large-aperture part; rc_dist(i) is the amplitude value corresponding to the ith pore throat radius in the pore throat radius distribution spectrum from small to large; n is the sequence number of the pore throat radius corresponding to the boundary line of the large-aperture part and the small-aperture part in the pore throat radius distribution spectrum from small to large; N is the total number of the pore throat radius values in the pore throat radius distribution spectrum; R c_ratio RC2 is the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part.

[0056] In the system, preferably, the permeability determination module comprises:

[0057] The model determination sub-module is configured to obtain a permeability determination model, wherein the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part and the porosity;

[0058] The permeability determination sub-module is configured to determine the permeability of the target reservoir by using the permeability determination model based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part of the target reservoir and the porosity of the target reservoir;

[0059] More preferably, the model determination sub-module comprises:

[0060] The second training data obtaining unit is configured to obtain the permeability of a plurality of dense sandstone reservoir cores with known porosity, the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part;

[0061] The model determination unit is configured to obtain a permeability determination model based on the permeability, the porosity, the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part of each core;

[0062] More preferably, the permeability determination model is:

[0063]

[0064] In the formula, K is the permeability, mD; is the porosity, %; R c_ratio RC2 is the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part; A and B are coefficients, A is preferably 0.1033, and B is preferably 0.8111.

[0065] The existing permeability determination method does not consider the pore structure of the reservoir, directly adopts the experience statistical method to calculate the reservoir permeability, and thus the applicability is not strong, and the method cannot be applied on a large scale. The tight sandstone reservoir permeability determination method provided by the present application determines the tight sandstone reservoir permeability based on the pore throat radius distribution. Based on the in-depth analysis on the shape of the pore throat radius distribution spectrum, the parameter sensitive to the high and low permeability, that is, the ratio of the cumulative amplitude of the large aperture part of the pore throat radius distribution to the cumulative amplitude of the small aperture part of the pore throat radius distribution, can accurately determine the reservoir permeability in the tight sandstone reservoir with strong heterogeneity. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 It is a porosity and permeability cross plot of a conventional core analysis of a certain tight sandstone reservoir 10633.

[0067] Figure 2 It is a core pore throat radius distribution spectrum and permeability comparison graph of a certain tight sandstone reservoir with good pore structure.

[0068] Figure 3 It is a core pore throat radius distribution spectrum and permeability comparison graph of a certain tight sandstone reservoir with poor pore structure.

[0069] Figure 4 It is a flow chart of the tight sandstone reservoir permeability determination method provided by one embodiment of the present application.

[0070] Figure 5 It is a large aperture part of the pore throat radius cumulative amplitude and the permeability correlation graph determined by taking 0.4 μm as the pore throat radius threshold.

[0071] Figure 6 It is a small aperture part of the pore throat radius cumulative amplitude and the permeability correlation graph determined by taking 0.4 μm as the pore throat radius threshold.

[0072] Figure 7 It is a schematic diagram of the permeability determination model determined in one embodiment of the present application.

[0073] Figure 8 It is a structure schematic diagram of the tight sandstone reservoir permeability determination system provided by one embodiment of the present application.

[0074] Figure 9 It is a schematic diagram of the logging curve, porosity data, pore throat distribution spectrum and permeability data involved in example 1. DETAILED DESCRIPTION

[0075] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0076] The existing reservoir permeability determination method is generally not applicable to the determination of the permeability of a tight sandstone reservoir. Taking a method for determining the reservoir permeability by using the correspondence between porosity and permeability as an example, the method is described. Figure 1 The figure shows the porosity and permeability crossplot of a conventional analysis of a core of a certain tight sandstone reservoir 10633. From the figure, it can be seen that Figure 1 It can be seen that, for a tight sandstone reservoir, due to the complex pore structure, the relationship between the core porosity and the permeability is very complex. At the same porosity, the corresponding permeability difference is more than 3 orders of magnitude. For example, taking the core porosity equal to 8.0% as an example, the corresponding permeability is distributed between 0.006-2.32 mD. In this case, the empirical statistical method cannot establish a relationship model between the reservoir permeability and the porosity, or the accuracy of the established relationship model between the permeability and the porosity is not high.

[0077] The inventors believe, after a large amount of research, that the pore structure, as a key factor controlling the reservoir permeation capacity, has a certain control effect on the permeability. Generally, the better the pore structure of a reservoir, the higher the corresponding permeability at the same porosity, and vice versa. Based on this, one of the reasons why the existing tight sandstone reservoir permeability determination model has low accuracy is that the influence of the pore structure on the reservoir permeability is not fully considered. In order to accurately determine the reservoir permeability, the pore structure of the reservoir needs to be effectively characterized first. In order to accurately determine the permeability of a tight sandstone reservoir, the inventors, on the basis of analyzing the shape of the pore throat radius distribution spectrum which is relatively effective in reflecting the pore structure of the reservoir, propose a method for determining the permeability of a tight sandstone reservoir by using the pore throat radius distribution.

[0078] The following will illustrate the influence of the pore throat radius and its distribution on the permeability by comparing the pore throat radius distribution spectrum and the experimental porosity and permeability of two representative cores of a certain tight sandstone reservoir. Figure 2 The pore throat radius distribution spectrum of a core with relatively high porosity and permeability is Figure 3 The pore throat radius distribution spectrum of a core with relatively low porosity and permeability is. From the figure, it can be seen that Figure 2 and Figure 3The morphological comparison of the pore throat radius distribution spectrum shows that rocks with higher porosity and permeability have better pore structures, with large pores dominating and small pores accounting for a relatively smaller proportion. Conversely, rocks with a larger proportion of small pores have poorer pore structures, and correspondingly lower porosity and permeability. Therefore, if a parameter can be established to quantitatively reflect the relative proportions of large and small pores in the pore throat radius distribution of rocks, it can be used to intuitively and quantitatively reflect the pore structure of tight sandstone reservoirs, and further used to estimate reservoir permeability.

[0079] The present invention provides a method for determining the permeability of tight sandstone reservoirs using pore throat radius distribution. The method divides the pore throat radius distribution spectrum of tight sandstone reservoirs into two parts: large pore diameter and small pore diameter. The method determines the ratio of the cumulative amplitude of the pore throat radius distribution in the large pore diameter part to the cumulative amplitude of the pore throat radius distribution in the small pore diameter part, thereby characterizing the pore structure of the rock. Then, combined with the reservoir porosity, the permeability of the tight sandstone reservoir is determined.

[0080] See Figure 4 A specific embodiment of the present invention provides a method for determining the permeability of tight sandstone reservoirs, wherein the method includes:

[0081] Step S1: Obtain the porosity of the target reservoir;

[0082] Step S2: Obtain the pore throat radius distribution spectrum of the target reservoir;

[0083] Step S3: Divide the pore throat radius distribution spectrum of the target reservoir into two parts: large pore size and small pore size. The permeability increases as the cumulative amplitude of the pore throat radius distribution in the large pore size part increases, and the permeability increases as the cumulative amplitude of the pore throat radius distribution in the small pore size part decreases.

[0084] Step S4: Based on the pore throat radius distribution spectrum of the large-diameter portion and the small-diameter portion of the target reservoir, determine the ratio of the cumulative amplitude of the pore throat radius distribution of the large-diameter portion to the cumulative amplitude of the pore throat radius distribution of the small-diameter portion of the target reservoir.

[0085] Step S5: Determine the permeability of the target reservoir based on the ratio of the cumulative amplitude of the pore throat radius distribution in the large-diameter portion to the cumulative amplitude of the pore throat radius distribution in the small-diameter portion, and the porosity of the target reservoir.

[0086] Further, in step S1, obtaining the porosity of the target reservoir includes:

[0087] The porosity of the target reservoir is determined using core experiments or well logging data.

[0088] Further, in step S2, obtaining the pore throat radius distribution spectrum of the target reservoir includes:

[0089] Step S21: obtaining a capillary pressure curve of the target reservoir; wherein the capillary pressure curve of the target reservoir can be determined by, but not limited to, core capillary pressure experiment or nuclear magnetic resonance logging data;

[0090] Step S22: determining a pore throat radius distribution spectrum of the target reservoir based on the capillary pressure curve of the target reservoir;

[0091] Further, in step S22, determining the pore throat radius distribution spectrum of the target reservoir based on the capillary pressure curve of the target reservoir comprises:

[0092] Step S221: determining each pore throat radius based on each capillary pressure on the capillary pressure curve of the target reservoir by using the relationship between the capillary pressure and the pore throat radius; wherein the relationship between the capillary pressure and the pore throat radius is preferably:

[0093] wherein i = 1, 2, …, N

[0094] wherein P c (i) is the ith capillary pressure, MPa; R c (i) is the ith pore throat radius, pm; N is the total number of capillary pressure points on the capillary pressure curve; Q is the surface contact angle of the two-phase fluid, (°); 2s cos(Q) is the surface tension of the two-phase fluid, dyn / cm; for the common air-mercury two-phase fluid system, 2s cos(Q) is a fixed value of 0.735;

[0095] Step S222: determining the amplitude value corresponding to each pore throat radius according to the mercury saturation corresponding to each capillary pressure on the capillary pressure curve of the target reservoir; wherein the amplitude value corresponding to each pore throat radius is preferably determined by the following formula:

[0096] rc_dist(1) = S Hg (1)

[0097] rc_dist(i) = S Hg (i) - S Hg (i-1)

[0098] wherein rc_dist(i) is the amplitude value corresponding to the ith pore throat radius; S Hg (i) is the non-wetting phase saturation corresponding to the ith capillary pressure on the capillary pressure curve, %;

[0099] Step S223: determining the pore throat radius distribution spectrum of the target reservoir based on the determined each pore throat radius and the amplitude value corresponding to each pore throat radius.

[0100] Furthermore, in step S3, dividing the pore throat radius distribution spectrum of the target reservoir into two parts—large pore size and small pore size—includes:

[0101] Step S31: Obtain the pore throat radius division threshold; wherein, the large-diameter part and small-diameter part obtained by dividing the pore throat radius distribution spectrum of tight sandstone reservoir according to the pore throat radius division threshold satisfy: as the cumulative amplitude of the pore throat radius distribution of the large-diameter part increases, the permeability increases; as the cumulative amplitude of the pore throat radius distribution of the small-diameter part decreases, the permeability increases.

[0102] Step S32: Based on the pore throat radius division threshold, divide the pore throat radius distribution spectrum of the target reservoir into two parts: large pore diameter and small pore diameter.

[0103] Furthermore, in step S31, obtaining the threshold for dividing the pore throat radius includes:

[0104] Step S311: Obtain the pore throat radius distribution spectrum of multiple tight sandstone reservoir cores with known permeability;

[0105] Step S312: Select a pore throat radius value, and divide the pore throat radius distribution spectrum of each core into a large pore diameter part and a small pore diameter part according to the pore throat radius value. Analyze the relationship between the cumulative amplitude of the pore throat radius distribution in the large pore diameter part and the permeability, and the relationship between the cumulative amplitude of the pore throat radius distribution in the small pore diameter part and the permeability.

[0106] Step S312: Repeat step S312 and take the pore throat radius value corresponding to the best correlation between the cumulative amplitude of the pore throat radius distribution and the permeability as the pore throat radius division threshold.

[0107] Furthermore, the threshold for defining the pore throat radius is 0.4 μm;

[0108] In one specific embodiment, analysis of the pore throat radius distribution spectrum of 92 core samples showed that when the pore throat radius was 0.4 μm, the cumulative amplitudes of the pore throat radius distribution in the large-diameter and small-diameter portions showed the strongest correlation with permeability (e.g., Figure 5 and Figure 6 As shown in the figure, as the cumulative amplitude of the throat radius distribution in the large-diameter part increases and the cumulative amplitude of the throat radius distribution in the small-diameter part decreases, the corresponding permeability increases significantly.

[0109] Further, in step S4, based on the pore throat radius distribution spectrum of the large-diameter portion and the small-diameter portion of the target reservoir, the ratio of the cumulative amplitude of the pore throat radius distribution in the large-diameter portion to the cumulative amplitude of the pore throat radius distribution in the small-diameter portion of the target reservoir is determined, including:

[0110] Step S41: determining the pore throat radius cumulative amplitude of the large-aperture part of the target reservoir based on the pore throat radius distribution spectrum of the large-aperture part of the target reservoir;

[0111] Step S42: determining the pore throat radius cumulative amplitude of the small-aperture part of the target reservoir based on the pore throat radius distribution spectrum of the small-aperture part of the target reservoir;

[0112] Step S43: determining the ratio of the cumulative amplitude of the large-aperture part pore throat radius distribution to the cumulative amplitude of the small-aperture part pore throat radius distribution of the target reservoir based on the cumulative amplitude of the large-aperture part and the cumulative amplitude of the small-aperture part of the target reservoir;

[0113] wherein,

[0114]

[0115] In the formula, RC1 is the cumulative amplitude of the pore throat radius of the small-aperture part; RC2 is the cumulative amplitude of the pore throat radius of the large-aperture part; rc_dist(i) is the amplitude value corresponding to the i-th pore throat radius from small to large in the pore throat radius distribution spectrum; n is the sequence number of the pore throat radius corresponding to the boundary line of the large-aperture part and the small-aperture part in the pore throat radius distribution spectrum sorted from small to large; N is the total number of the pore throat radius values in the pore throat radius distribution spectrum; R c_ratio is the ratio of the cumulative amplitude of the large-aperture part pore throat radius distribution to the cumulative amplitude of the small-aperture part pore throat radius distribution.

[0116] Further, in step S5, determining the permeability of the target reservoir based on the ratio of the cumulative amplitude of the large-aperture part pore throat radius distribution to the cumulative amplitude of the small-aperture part pore throat radius distribution of the target reservoir and the porosity of the target reservoir comprises:

[0117] Step S51: obtaining a permeability determination model; wherein the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the large-aperture part pore throat radius distribution to the cumulative amplitude of the small-aperture part pore throat radius distribution and the porosity;

[0118] Step S52: determining the permeability of the target reservoir by using the permeability determination model based on the ratio of the cumulative amplitude of the large-aperture part pore throat radius distribution to the cumulative amplitude of the small-aperture part pore throat radius distribution of the target reservoir and the porosity of the target reservoir;

[0119] Still further, in step S51, obtaining the permeability determination model comprises:

[0120] Step S511: obtaining the permeability of the tight sandstone reservoir core with the known porosity and the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution;

[0121] Step S512: obtaining the permeability determination model based on the permeability, the porosity, the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution of each core;

[0122] Further, the permeability determination model is:

[0123]

[0124] wherein, K is the permeability, mD; is the porosity, %; R c_ratio is the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution; A and B are coefficients, A is preferably 0.1033, and B is preferably 0.8111;

[0125] In a specific embodiment, through the analysis of the permeability, the porosity, the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution of 92 cores, (K is the permeability, is the porosity) and R c_ratio (the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution) has a very strong exponential relationship (as shown in Figure 7 ), and the permeability of the tight sandstone reservoir can be accurately calculated by using the exponential relationship under the condition that R c_ratio and are known; compared with the relationship between the conventional core porosity and the permeability as shown in Figure 1 , the accuracy of the permeability determination is greatly improved by using the correlation relationship.

[0126] The embodiment of the present application also provides a tight sandstone reservoir permeability determination system, which is used for implementing the tight sandstone reservoir permeability determination method embodiment as described above, and the system includes: Figure 8 as shown in the figure, the system includes:

[0127] The porosity obtaining module 81 is used for obtaining the porosity of the target reservoir;

[0128] The pore throat radius distribution spectrum obtaining module 82 is used for obtaining the pore throat radius distribution spectrum of the target reservoir;

[0129] The large and small aperture part division module 83 is configured to divide the pore throat radius distribution spectrum of the target reservoir into a large aperture part and a small aperture part, wherein the permeability of the large aperture part increases with the increase of the cumulative amplitude of the pore throat radius distribution of the large aperture part, and the permeability of the small aperture part increases with the decrease of the cumulative amplitude of the pore throat radius distribution of the small aperture part.

[0130] The ratio acquisition module 84 is configured to determine the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part based on the pore throat radius distribution spectrum of the large aperture part and the pore throat radius distribution spectrum of the small aperture part of the target reservoir.

[0131] The permeability determination module 85 is configured to determine the permeability of the target reservoir based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part and the porosity of the target reservoir.

[0132] Further, the porosity acquisition module 81 is specifically configured to determine the porosity of the target reservoir by using core experiments or logging data.

[0133] Further, the pore throat radius distribution spectrum acquisition module 82 comprises:

[0134] The capillary pressure curve acquisition sub-module 821 is configured to acquire the capillary pressure curve of the target reservoir.

[0135] The pore throat radius distribution spectrum determination sub-module 822 is configured to determine the pore throat radius distribution spectrum of the target reservoir based on the capillary pressure curve of the target reservoir.

[0136] Further, the pore throat radius distribution spectrum determination sub-module 822 comprises:

[0137] The pore throat radius determination unit 8221 is configured to determine each pore throat radius by using the relationship between the capillary pressure and the pore throat radius based on each capillary pressure on the capillary pressure curve of the target reservoir, wherein the relationship between the capillary pressure and the pore throat radius is preferably:

[0138] Wherein, i = 1, 2, …, N

[0139] In the formula, P c (i) is the i th capillary pressure, MPa; R c (i) is the i th pore throat radius, μm; N is the total number of capillary pressure points on the capillary pressure curve; θ is the surface contact angle of the two-phase fluid, (°); σ is the surface tension of the two-phase fluid, dyn / cm; for the common air-mercury two-phase fluid system, 2σcos(θ) is a fixed value of 0.735;

[0140] The amplitude value determination unit 8222 is configured to determine the amplitude value corresponding to each pore throat radius according to the mercury saturation corresponding to each capillary pressure on the capillary pressure curve of the target reservoir.

[0141] rc_dist(1) = S Hg (1)

[0142] rc_dist(i) = S Hg (i) - S Hg (i - 1)

[0143] wherein rc_dist(i) is the amplitude value corresponding to the ith pore throat radius; S Hg (i) is the non-wetting phase saturation, % corresponding to the ith capillary pressure on the capillary pressure curve;

[0144] The pore throat radius distribution spectrum determination unit 8223 is configured to determine the pore throat radius distribution spectrum of the target reservoir based on the determined pore throat radii and the amplitude values corresponding to the pore throat radii.

[0145] Further, the large and small pore diameter part division module 83 comprises:

[0146] The threshold determination sub-module 831 is configured to obtain a pore throat radius division threshold; wherein the large pore diameter part and the small pore diameter part obtained by dividing the pore throat radius distribution spectrum of the tight sandstone reservoir according to the pore throat radius division threshold satisfy: the corresponding permeability increases as the cumulative amplitude of the large pore diameter part pore throat radius distribution increases, and the corresponding permeability increases as the cumulative amplitude of the small pore diameter part pore throat radius distribution decreases;

[0147] The large and small pore diameter part division sub-module 832 is configured to divide the pore throat radius distribution spectrum of the target reservoir into a large pore diameter part and a small pore diameter part based on the pore throat radius division threshold;

[0148] Further, the threshold determination sub-module 831 comprises:

[0149] The first training data acquisition unit 8311 is configured to acquire the pore throat radius distribution spectrum of a plurality of tight sandstone reservoir cores with known permeability;

[0150] The threshold determination unit 8312 is configured to repeatedly select a pore throat radius value, divide the pore throat radius distribution spectrum of each core into a large pore diameter part and a small pore diameter part according to the pore throat radius value, analyze the relationship between the cumulative amplitude of the large pore diameter part pore throat radius distribution and the permeability and the relationship between the cumulative amplitude of the small pore diameter part pore throat radius distribution and the permeability, and take the pore throat radius value corresponding to the best correlation between the cumulative amplitude of the pore throat radius distribution and the permeability as the pore throat radius division threshold;

[0151] Further, the pore throat radius division threshold is 0.4 μm.

[0152] Further, the ratio obtaining module 84 comprises:

[0153] The first cumulative amplitude determination sub-module 841 is configured to determine the cumulative amplitude of the pore throat radius of the large-aperture part of the target reservoir based on the pore throat radius distribution spectrum of the large-aperture part of the target reservoir.

[0154] The second cumulative amplitude determination sub-module 842 is configured to determine the cumulative amplitude of the pore throat radius of the small-aperture part of the target reservoir based on the pore throat radius distribution spectrum of the small-aperture part of the target reservoir.

[0155] The ratio determination sub-module 843 is configured to determine the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part of the target reservoir to the cumulative amplitude of the pore throat radius distribution of the small-aperture part of the target reservoir based on the cumulative amplitude of the pore throat radius of the large-aperture part of the target reservoir and the cumulative amplitude of the pore throat radius of the small-aperture part of the target reservoir.

[0156] wherein,

[0157]

[0158]

[0159] wherein, RC1 is the cumulative amplitude of the pore throat radius of the small-aperture part; RC2 is the cumulative amplitude of the pore throat radius of the large-aperture part; rc_dist(i) is the amplitude value corresponding to the ith pore throat radius from small to large in the pore throat radius distribution spectrum; n is the sequence number of the pore throat radius corresponding to the boundary line of the large-aperture part and the small-aperture part in the pore throat radius distribution spectrum sorted from small to large; N is the total number of the pore throat radius values in the pore throat radius distribution spectrum; R c_ratio is the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part.

[0160] Further, the permeability determination module 85 comprises:

[0161] The model determination sub-module 851 is configured to obtain a permeability determination model; wherein, the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part and the porosity;

[0162] The permeability determination sub-module 852 is configured to determine the permeability of the target reservoir based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large-aperture part to the cumulative amplitude of the pore throat radius distribution of the small-aperture part of the target reservoir and the porosity of the target reservoir by using the permeability determination model.

[0163] Furthermore, the model determination submodule 851 includes:

[0164] Second training data acquisition unit 8511: used to acquire the permeability of tight sandstone reservoir cores with multiple known porosities and the ratio of the cumulative amplitude of the pore throat radius distribution of the large-diameter portion to the cumulative amplitude of the pore throat radius distribution of the small-diameter portion.

[0165] Model determination unit 8512: used to obtain a permeability determination model based on the ratio of the cumulative amplitude of the pore throat radius distribution in the large-diameter part to the cumulative amplitude of the pore throat radius distribution in the small-diameter part of each core.

[0166] Furthermore, the penetration rate determination model is as follows:

[0167]

[0168] In the formula, K is the permeability, mD; Porosity, %; R c_ratio It is the ratio of the cumulative amplitude of the throat radius distribution in the large-diameter section to the cumulative amplitude of the throat radius distribution in the small-diameter section; A and B are coefficients, with A preferably being 0.1033 and B preferably being 0.8111.

[0169] Example 1

[0170] This embodiment provides a method for determining the permeability of tight sandstone reservoirs, used to predict the permeability of a well in a certain area, specifically including the following steps:

[0171] 1. Based on the logging curves of the target well, determine the porosity at different depths of the target well.

[0172] See the logging curves for the target well. Figure 9 The porosity at different depths of the target well, determined based on the logging curves of the target well, is shown in [reference]. Figure 9 POR in;

[0173] To verify the accuracy of the porosity at different depths of the target well determined based on the logging curves of the target well, laboratory porosity tests were conducted on core samples taken from different depths of the target well. The results are shown in [reference needed]. Figure 9 The CPOR in the data, compared with POR, shows that the porosity at different depths of the target well determined based on the logging curve of the target well has high reliability.

[0174] 2. Based on the logging curves of the target well, determine the distribution spectrum of the pore throat radius at different depths of the target well.

[0175] The reservoir pore throat radius distribution spectrum acquisition method disclosed in CN115096788A is referred to for determining the pore throat radius distribution spectrum of the target well at different depths, and the pore throat radius distribution spectrum of the target well at different depths is shown in Figure 9 .

[0176] 3. The pore throat radius distribution spectrum at different depths of the target well is divided into two parts of large pore diameter and small pore diameter, specifically:

[0177] 3.1. A pore throat radius division threshold is obtained.

[0178] 92 cores in the area where the target well is located are obtained; the capillary pressure curves of each core are determined through the core capillary pressure experiment; based on the capillary pressure curves of each core, the pore throat radius distribution spectrum of each core is determined; through the analysis of the pore throat radius distribution spectrum of the 92 cores, it is shown that when the pore throat radius is 0.4 μm, the correlation between the cumulative amplitude of the large pore diameter part of the pore throat radius distribution and the cumulative amplitude of the small pore diameter part of the pore throat radius and the permeability is the strongest (as shown in Figure 5 and Figure 6 ), and with the increase of the cumulative amplitude of the large pore diameter part of the pore throat radius distribution and the decrease of the cumulative amplitude of the small pore diameter part of the pore throat radius distribution, the corresponding permeability is obviously increased; therefore, the pore throat radius division threshold is 0.4 μm;

[0179] The pore throat radius distribution spectrum of each core is determined by the following method:

[0180] Based on each capillary pressure on the capillary pressure curve of the target core, the relationship between the capillary pressure and the pore throat radius is determined by using the following formula:

[0181] Wherein, i = 1, 2, …, N

[0182] In the formula, P c (i) is the i-th capillary pressure, MPa; R c (i) is the i-th pore throat radius, μm; N is the total number of capillary pressure points on the capillary pressure curve; θ is the surface contact angle of two-phase fluid, (°); σ is the surface tension of two-phase fluid, dyn / cm; 2σcos(θ) is a fixed value of 0.735;

[0183] According to the mercury saturation degree corresponding to each capillary pressure on the capillary pressure curve of the target core, the amplitude value corresponding to each pore throat radius is determined: wherein the amplitude value corresponding to each pore throat radius is determined by the following formula:

[0184] rc_dist(1) = S Hg (1)

[0185] rc_dist(i) = S Hg(i) -S Hg (i-1)

[0186] wherein rc_dist(i) is the amplitude value corresponding to the i-th pore throat radius; S Hg (i) is the non-wetting phase saturation, % corresponding to the i-th capillary pressure on the capillary pressure curve;

[0187] Based on the determined pore throat radius and the amplitude value corresponding to each pore throat radius, the pore throat radius distribution spectrum of the target core is determined.

[0188] 3.2, based on the pore throat radius division threshold, the pore throat radius distribution spectrum at different depths of the target well is divided into two parts of large pore diameter and small pore diameter.

[0189] 4, based on the pore throat radius distribution spectrum of the large pore diameter part and the pore throat radius distribution spectrum of the small pore diameter part at different depths of the target well, the ratio of the cumulative amplitude of the large pore diameter part pore throat radius distribution to the cumulative amplitude of the small pore diameter part pore throat radius distribution at different depths of the target well is determined;

[0190] wherein the ratio of the cumulative amplitude of the large pore diameter part pore throat radius distribution to the cumulative amplitude of the small pore diameter part pore throat radius distribution at different depths of the target well is determined by the following way:

[0191] Based on the pore throat radius distribution spectrum of the large pore diameter part at the target depth, the cumulative amplitude of the pore throat radius of the large pore diameter part at the target depth is determined;

[0192] Based on the pore throat radius distribution spectrum of the small pore diameter part at the target depth, the cumulative amplitude of the pore throat radius of the small pore diameter part at the target depth is determined;

[0193] Based on the cumulative amplitude of the pore throat radius of the large pore diameter part and the cumulative amplitude of the pore throat radius of the small pore diameter part at the target depth, the ratio of the cumulative amplitude of the large pore diameter part pore throat radius distribution to the cumulative amplitude of the small pore diameter part pore throat radius distribution at the target depth is determined;

[0194] wherein,

[0195]

[0196] wherein RC1 is the cumulative amplitude of the pore throat radius of the small pore diameter part; RC2 is the cumulative amplitude of the pore throat radius of the large pore diameter part; rc_dist(i) is the amplitude value corresponding to the i-th pore throat radius value from small to large on the pore throat radius distribution spectrum; n is the order number of the pore throat radius corresponding to the boundary line of the large pore diameter part and the small pore diameter part on the pore throat radius distribution spectrum in the sequence of each pore throat radius on the pore throat radius distribution spectrum from small to large; N is the total number of each pore throat radius value on the pore throat radius distribution spectrum; R c_ratioThe ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution.

[0197] 5. Determine the permeability at different depths of the target well based on the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution and the porosity at different depths of the target well, in particular:

[0198] 5.1. Obtain a permeability determination model; wherein the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution and the porosity; in particular:

[0199] Obtain 92 cores in the area where the target well is located; determine the porosity, the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution, and the permeability of each core;

[0200] Based on the permeability, porosity, and the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution of each core, obtain a permeability determination model (as shown in Figure 7 ); wherein the permeability determination model is:

[0201]

[0202] In the formula, K is the permeability, mD; is the porosity, %; R c_ratio is the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution; A and B are coefficients, A is 0.1033, and B is 0.8111;

[0203] 5.2. Determine the permeability at different depths of the target well based on the ratio of the cumulative amplitude of the large-pore throat radius distribution to the cumulative amplitude of the small-pore throat radius distribution and the porosity at different depths of the target well, and use the permeability determination model, the result is shown as PERM in Figure 9 .

[0204] In order to verify the accuracy of the determined permeability at different depths of the target well, indoor permeability tests are performed on the cores taken from different depths of the target well, and the results are shown as CPERM in Figure 9 . It can be known from the comparison between CPERM and PERM that the permeability at different depths of the target well determined in the embodiment has high reliability.

[0205] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of determining permeability of a tight sand reservoir, wherein, The method comprises: obtaining the porosity of the target reservoir; obtaining the pore throat radius distribution spectrum of the target reservoir; dividing the pore throat radius distribution spectrum of the target reservoir into two parts of large aperture and small aperture; wherein, as the cumulative amplitude of the pore throat radius distribution of the large aperture part increases, the corresponding permeability increases, and as the cumulative amplitude of the pore throat radius distribution of the small aperture part decreases, the corresponding permeability increases; determining the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part of the target reservoir based on the pore throat radius distribution spectrum of the large aperture part and the pore throat radius distribution spectrum of the small aperture part of the target reservoir; determining the permeability of the target reservoir based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part of the target reservoir and the porosity of the target reservoir; wherein, the determination of the permeability of the target reservoir based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part of the target reservoir and the porosity of the target reservoir comprises: obtaining a permeability determination model; wherein, the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part and the porosity; determining the permeability of the target reservoir by using the permeability determination model based on the ratio of the cumulative amplitude of the pore throat radius distribution of the large aperture part to the cumulative amplitude of the pore throat radius distribution of the small aperture part of the target reservoir and the porosity of the target reservoir; wherein, the obtaining of the permeability determination model comprises: obtaining the permeability of a plurality of dense sandstone reservoir cores with known porosity, ratio of cumulative amplitude of pore throat radius distribution of large aperture part to cumulative amplitude of pore throat radius distribution of small aperture part; obtaining the permeability determination model based on the permeability, porosity, ratio of cumulative amplitude of pore throat radius distribution of large aperture part to cumulative amplitude of pore throat radius distribution of small aperture part of each core; wherein, the permeability determination model is: where K is permeability, mD; is porosity, %; R c_ratio is the ratio of the cumulative amplitude of the large-pore portion of the pore throat radius distribution to the cumulative amplitude of the small-pore portion of the pore throat radius distribution; A and B are coefficients.

2. The method of claim 1, wherein, the division of the pore throat radius distribution spectrum of the target reservoir into two parts of large aperture and small aperture comprises: obtaining a pore throat radius division threshold; wherein, the division of the pore throat radius distribution spectrum of the dense sandstone reservoir according to the pore throat radius division threshold obtains a large aperture part and a small aperture part that satisfy: as the cumulative amplitude of the pore throat radius distribution of the large aperture part increases, the corresponding permeability increases, and as the cumulative amplitude of the pore throat radius distribution of the small aperture part decreases, the corresponding permeability increases; dividing the pore throat radius distribution spectrum of the target reservoir into two parts of large aperture and small aperture based on the pore throat radius division threshold.

3. The method of claim 2, wherein, the obtaining of the pore throat radius division threshold comprises: 1) obtaining the pore throat radius distribution spectrum of a plurality of dense sandstone reservoir cores with known permeability; 2) selecting a pore throat radius value, and dividing the pore throat radius distribution spectrum of each core into a large aperture part and a small aperture part according to the pore throat radius value, and analyzing the relationship between the cumulative amplitude of the pore throat radius distribution of the large aperture part and the permeability and the relationship between the cumulative amplitude of the pore throat radius distribution of the small aperture part and the permeability; 3) repeat step 2), and take the pore throat radius value corresponding to the best correlation between the cumulative amplitude of the pore throat radius distribution and the permeability as the pore throat radius division threshold.

4. The method of claim 2 or 3, wherein, The pore throat radius division threshold is 0.4 μm.

5. The method of claim 1, wherein, A is 0.1033, and B is 0.8111.

6. A tight sand reservoir permeability determination system, wherein, The system comprises: a porosity acquisition module configured to acquire the porosity of the target reservoir; a pore throat radius distribution spectrum acquisition module configured to acquire the pore throat radius distribution spectrum of the target reservoir; a large-small aperture portion division module configured to divide the pore throat radius distribution spectrum of the target reservoir into a large-aperture portion and a small-aperture portion; wherein, as the cumulative amplitude of the large-aperture portion pore throat radius distribution increases, the corresponding permeability increases, and as the cumulative amplitude of the small-aperture portion pore throat radius distribution decreases, the corresponding permeability increases; a ratio acquisition module configured to determine the ratio of the cumulative amplitude of the large-aperture portion pore throat radius distribution to the cumulative amplitude of the small-aperture portion pore throat radius distribution based on the large-aperture portion pore throat radius distribution spectrum and the small-aperture portion pore throat radius distribution spectrum of the target reservoir; a permeability determination module configured to determine the permeability of the target reservoir based on the ratio of the cumulative amplitude of the large-aperture portion pore throat radius distribution to the cumulative amplitude of the small-aperture portion pore throat radius distribution and the porosity of the target reservoir; wherein the permeability determination module comprises: a model determination sub-module configured to acquire a permeability determination model; wherein the permeability determination model is a calculation model of the permeability with respect to the ratio of the cumulative amplitude of the large-aperture portion pore throat radius distribution to the cumulative amplitude of the small-aperture portion pore throat radius distribution and the porosity; a permeability determination sub-module configured to determine the permeability of the target reservoir based on the ratio of the cumulative amplitude of the large-aperture portion pore throat radius distribution to the cumulative amplitude of the small-aperture portion pore throat radius distribution and the porosity of the target reservoir by using the permeability determination model; wherein the model determination sub-module comprises: a second training data acquisition unit configured to acquire the permeability of a plurality of dense sandstone reservoir cores with known porosity, ratio of cumulative amplitude of large-aperture portion pore throat radius distribution to cumulative amplitude of small-aperture portion pore throat radius distribution; a model determination unit configured to acquire a permeability determination model based on the permeability, porosity, and ratio of cumulative amplitude of large-aperture portion pore throat radius distribution to cumulative amplitude of small-aperture portion pore throat radius distribution of each core; wherein the permeability determination model is: where K is permeability, mD; is porosity, %; R c_ratio is the ratio of the cumulative amplitude of the large-pore portion of the pore throat radius distribution to the cumulative amplitude of the small-pore portion of the pore throat radius distribution; A and B are coefficients.

7. The system of claim 6, wherein, the large-small aperture portion division module comprises: a threshold determination sub-module configured to acquire a pore throat radius division threshold; wherein the large-aperture portion and the small-aperture portion obtained by dividing the pore throat radius distribution spectrum of the dense sandstone reservoir according to the pore throat radius division threshold satisfy: as the cumulative amplitude of the large-aperture portion pore throat radius distribution increases, the corresponding permeability increases, and as the cumulative amplitude of the small-aperture portion pore throat radius distribution decreases, the corresponding permeability increases; a large-small aperture portion division sub-module configured to divide the pore throat radius distribution spectrum of the target reservoir into a large-aperture portion and a small-aperture portion based on the pore throat radius division threshold.

8. The system of claim 7, wherein, The threshold determination sub-module comprises: The first training data acquisition unit is configured to acquire the pore throat radius distribution spectrum of the tight sandstone reservoir core with a plurality of known permeabilities. The threshold determination unit is configured to repeatedly select a pore throat radius value, divide the pore throat radius distribution spectrum of each core into a large pore radius part and a small pore radius part according to the pore throat radius value, analyze the relationship between the cumulative amplitude of the pore throat radius distribution of the large pore radius part and the permeability and the relationship between the cumulative amplitude of the pore throat radius distribution of the small pore radius part and the permeability, and take the pore throat radius value corresponding to the best correlation between the cumulative amplitude of the pore throat radius distribution and the permeability as the pore throat radius division threshold.

9. The system of claim 7 or 8, wherein, The pore throat radius division threshold is 0.4 μm.

10. The system of claim 6, wherein, A is 0.1033 and B is 0.8111.

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