A method and system for obtaining a reservoir pore throat radius distribution spectrum

Abstract

The application provides a reservoir pore throat radius distribution spectrum acquisition method and system. The method comprises the following steps: obtaining a porosity curve of a target reservoir, i.e. a curve of porosity changing with depth; determining a distribution mode, and then determining N pore throat radii; obtaining a relationship model between the frequency of a rated pore throat radius and porosity, and a relationship model between the frequencies of the N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii; based on the porosity curve of the target reservoir, the relationship model between the frequency of the rated pore throat radius and porosity, and the relationship model between the frequencies of the N pore throat radii, the frequency of the N pore throat radii at each depth of the target reservoir is determined, so that the pore throat radius distribution spectrum at each depth of the target reservoir is determined. The method can continuously construct the reservoir pore throat radius distribution spectrum from the conventional porosity curve, and realizes continuous and quantitative characterization of the reservoir pore structure.

Description

Technical Field

[0001] The present invention relates to the field of reservoir evaluation, and in particular to a method and system for obtaining a reservoir pore throat radius distribution spectrum. Background Art

[0002] Pore ​​structure is defined as the size and connectivity of a rock's pores. It consists of two elements: porosity and connectivity. Reservoirs with high porosity and good pore connectivity are generally considered to have good pore structures, while reservoirs with low porosity and poor pore connectivity, high porosity but poor pore connectivity, or low porosity but good pore connectivity are all considered to have poor pore structures.

[0003] With the continuous advancement of oil and gas exploration, favorable reservoirs with good pore structures and high permeability have been depleted. Low-permeability, tight reservoirs with relatively complex pore structures have gradually become the primary targets of oil and gas exploration. These reservoirs are highly heterogeneous, and their permeability patterns do not conform to the classic Darcy theorem, posing significant challenges in reservoir effectiveness evaluation, parameter calculation, and fluid property identification. For these reservoir types, pore structure is a crucial factor in determining reservoir effectiveness. Generally speaking, reservoirs with relatively good pore structures also have high permeability, and the more fully oil and gas are stored, the more likely they are to form high-yield reservoirs. Reservoirs with relatively poor pore structures, on the other hand, are not fully filled with oil and gas, and may even be unable to enter the rock pore spaces and accumulate. These reservoirs are considered poor oil and gas formations or non-reservoirs. Therefore, quantitative evaluation of rock pore structure is a key approach to improving the exploration efficiency of complex reservoirs and reducing development risks.

[0004] Capillary pressure curves are effective data for quantitatively evaluating reservoir pore structure. By processing these curves, a pore throat radius distribution spectrum can be obtained. This pore throat radius distribution spectrum can be used to determine the pore throat radius distribution range and dominant pore throat radius distribution interval of the reservoir rock. Parameters such as the average pore throat radius, maximum pore throat radius, and median radius can also be calculated. This helps classify reservoir types and determine reservoir effectiveness. However, when using capillary pressure curves to obtain pore throat radius distribution spectra for quantitative reservoir pore structure characterization, the number of capillary pressure curves is very limited, making it impossible to continuously obtain pore throat radius distribution spectra for continuous quantitative characterization of reservoir pore structure. This results in an inability to quantitatively characterize the pore structure in well sections where coring and mercury injection testing are not performed. Summary of the Invention

[0005] The object of the present invention is to provide a method and system for acquiring a reservoir pore throat radius distribution spectrum, which can be used to continuously and quantitatively characterize the reservoir pore structure in a formation.

[0006] In order to achieve the above object, the present invention provides a method for obtaining a reservoir pore throat radius distribution spectrum, wherein the method comprises:

[0007] Obtain the porosity curve of the target reservoir, i.e., the curve showing the change of porosity with depth;

[0008] Determine the point distribution method and then determine N pore throat radii;

[0009] Obtaining a relationship model between the frequency of a rated pore throat radius and porosity, and a relationship model between the frequencies of N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii;

[0010] Based on the porosity curve of the target reservoir, the frequency of the N pore throat radii at each depth of the target reservoir is determined by utilizing the relationship model between the frequency of the rated pore throat radius and porosity and the relationship model between the frequencies of the N pore throat radii, thereby determining the pore throat radius distribution spectrum at each depth of the target reservoir.

[0011] In the above acquisition method, preferably, acquiring the porosity curve of the target reservoir includes:

[0012] Obtain porosity logging data of target reservoir;

[0013] Based on the porosity logging data of the target reservoir, the porosity curve of the target reservoir is determined.

[0014] In the above acquisition method, preferably, the determined N pore throat radii are:

[0015]

[0016] Where R c (i) is the i-th pore throat radius, μm; N is the number of pore throat radius points, and its value is generally greater than or equal to 13;

[0017] More preferably, N is 13-48;

[0018] More preferably, the rated pore throat radius is the pore throat radius when i=11, 12, 13, 14, or 15.

[0019] In the above acquisition method, preferably, the rated pore throat radius is 0.14 μm-0.009 μm.

[0020] In the above acquisition method, preferably, the relationship model between the frequency of the rated pore throat radius and the porosity is:

[0021]

[0022] Where amp(E) is the frequency of the rated pore throat radius, %; is the porosity, %; A', B' and C' are coefficients, and their values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data.

[0023] In the above acquisition method, preferably, the relationship model between the frequencies of the N pore throat radii is:

[0024]

[0025] Where amp(i) is the frequency of the i-th pore throat radius; a(i), b(i), and c(i) are coefficients, whose values ​​can be obtained by calibration using core mercury injection test data; and E is the i value corresponding to the rated pore throat radius, that is, the sequence number of the rated pore throat radius among the N pore throat radii.

[0026] In the above acquisition method, preferably, the relationship model between the frequency of obtaining the rated pore throat radius and the porosity, and the relationship model between the frequencies of N pore throat radii include:

[0027] Obtain the porosity of the core used for model calibration;

[0028] Obtain mercury injection experimental data of rock cores for model calibration;

[0029] Based on the mercury injection experimental data of the core used for model calibration, the frequencies corresponding to the N pore throat radii of each core are determined respectively;

[0030] Determine a relationship model between the frequency of the rated pore throat radius and the porosity based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core;

[0031] Determining a relationship model between the frequencies of the N pore throat radii based on the frequencies corresponding to the N pore throat radii of each core;

[0032] More preferably, based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, determining the relationship model between the frequency of the rated pore throat radius and the porosity includes:

[0033] Based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, respectively determine a relationship model between the frequency of each pore throat radius and the porosity;

[0034] Among the relationship models between the frequency of each pore throat radius and porosity, the model with the best correlation is selected as the relationship model between the frequency of the rated pore throat radius and porosity; the pore throat radius corresponding to the model is the rated pore throat radius;

[0035] More preferably, based on the mercury injection experimental data of the core used for model calibration, the frequencies corresponding to the N pore throat radii of each core are determined respectively by the following formula:

[0036] amp(1)=S Hg (1)

[0037] amp(i)=S Hg (i)-S Hg (i-1), i=2,3,…,N

[0038] Where S Hg (i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius;

[0039] More preferably, obtaining mercury injection experimental data of a core for model calibration includes:

[0040] Based on N pore throat radii, the mercury injection pressure corresponding to the N pore throat radii is determined respectively;

[0041] Based on the mercury injection pressure corresponding to N pore throat radii, mercury injection experiments are carried out on each core to obtain the mercury saturation corresponding to each mercury injection pressure;

[0042] More preferably, the core used for model calibration is taken from the area where the target reservoir is located;

[0043] In a specific embodiment, based on the porosity of each core and the frequency corresponding to the N pore throat radii of each core, when determining the relationship model between the frequency of each pore throat radius and the porosity, a one-variable quadratic statistical regression method can be used to determine the relationship model between the frequency of each pore throat radius and the porosity. The values ​​of A'(i), B'(i) and C'(i) in are used to determine the relationship model between the frequency of each pore throat radius and porosity; where amp(i) is the frequency of the i-th pore throat radius, %. is the porosity, %; A'(i), B'(i) and C'(i) are coefficients, whose values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data;

[0044] In a specific embodiment, based on the frequencies corresponding to the N pore throat radii of each core, when determining the relationship model between the frequencies of the N pore throat radii, a method of univariate quadratic statistical regression can be used to determine the relationship model between the frequencies of the N pore throat radii. The values ​​of a(i), b(i) and c(i) in are used to determine the relationship model between the frequencies of N pore throat radii.

[0045] In the above acquisition method, preferably, determining the pore throat radius distribution spectrum at each depth of the target reservoir includes:

[0046] For each depth of the target reservoir, a plot is drawn with N pore throat radii as logarithmic abscissas and the frequencies of N pore throat radii as linear ordinates to obtain the pore throat radius distribution spectrum at the depth of the target reservoir.

[0047] The present invention also provides a reservoir pore throat radius distribution spectrum acquisition system, wherein the system comprises:

[0048] Porosity curve acquisition module: used to obtain the porosity curve of the target reservoir, that is, the curve showing the change of porosity with depth;

[0049] Pore ​​throat radius determination module: used to determine the point distribution method and then determine N pore throat radii;

[0050] Model acquisition module: used to obtain a relationship model between the frequency of the rated pore throat radius and the porosity and a relationship model between the frequencies of N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii;

[0051] Pore ​​throat radius distribution spectrum acquisition module: used to determine the frequencies of N pore throat radii at each depth of the target reservoir based on the porosity curve of the target reservoir, using the relationship model between the frequency of the rated pore throat radius and porosity, and the relationship model between the frequencies of N pore throat radii, thereby determining the pore throat radius distribution spectrum at each depth of the target reservoir.

[0052] In the above acquisition system, preferably, the porosity curve acquisition module includes:

[0053] Well logging data acquisition submodule: used to obtain porosity logging data of target reservoir;

[0054] Porosity curve determination submodule: used to determine the porosity curve of the target reservoir based on the porosity logging data of the target reservoir.

[0055] In the above acquisition system, preferably, the N pore throat radii determined by the pore throat radius determination module are:

[0056]

[0057] Where R c (i) is the i-th pore throat radius, μm; N is the number of pore throat radius distribution points, and its value is generally

[0058] Greater than or equal to 13;

[0059] More preferably, N is 13-48;

[0060] More preferably, the rated pore throat radius is the pore throat radius when i=11, 12, 13, 14, or 15.

[0061] In the above acquisition system, preferably, the rated pore throat radius is 0.14 μm-0.009 μm.

[0062] In the above acquisition system, preferably, the relationship model between the frequency of the rated pore throat radius and the porosity is:

[0063]

[0064] Where amp(E) is the frequency of the rated pore throat radius, %; is the porosity, %; A', B' and C' are coefficients, and their values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data.

[0065] In the above acquisition system, preferably, the relationship model between the frequencies of the N pore throat radii is:

[0066]

[0067] Where amp(i) is the frequency of the i-th pore throat radius; a(i), b(i), and c(i) are coefficients, whose values ​​can be obtained by calibration using core mercury injection test data; and E is the i value corresponding to the rated pore throat radius, that is, the sequence number of the rated pore throat radius among the N pore throat radii.

[0068] In the above acquisition system, preferably, the pore throat radius distribution spectrum acquisition module includes:

[0069] Porosity acquisition submodule: used to obtain the porosity of the core used for model calibration;

[0070] Mercury injection data acquisition submodule: used to obtain mercury injection experimental data of cores for model calibration;

[0071] Frequency determination submodule: used to determine the frequencies corresponding to the N pore throat radii of each core based on the mercury injection experimental data of the core used for model calibration;

[0072] A first model determination submodule is used to determine a relationship model between the frequency of the rated pore throat radius and the porosity based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core;

[0073] The second model determination submodule is used to determine a relationship model between the frequencies of the N pore throat radii based on the frequencies corresponding to the N pore throat radii of each core;

[0074] More preferably, the first model determination submodule includes:

[0075] A first acquisition unit is configured to determine a relationship model between the frequency and porosity of each pore throat radius based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core;

[0076] The second acquisition unit is configured to select a model with the best correlation among the relationship models between the frequencies of the pore throat radii and the porosity as the relationship model between the frequencies of the rated pore throat radii and the porosity; wherein the pore throat radius corresponding to the model is the rated pore throat radius;

[0077] More preferably, the frequency determination submodule determines the frequencies corresponding to the N pore throat radii of each core by the following formula:

[0078] amp(1)=S Hg (1)

[0079] amp(i)=S Hg (i)-S Hg (i-1), i=2,3,…,N

[0080] Where S Hg (i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius;

[0081] More preferably, the mercury intrusion data acquisition submodule includes:

[0082] Mercury injection pressure determination unit: used to determine the mercury injection pressure corresponding to N pore throat radii based on N pore throat radii;

[0083] Mercury injection saturation acquisition unit: used to perform mercury injection experiments on each core based on the mercury injection pressure corresponding to N pore throat radii, and obtain the mercury injection saturation corresponding to each mercury injection pressure;

[0084] More preferably, the core used for model calibration is taken from the area where the target reservoir is located;

[0085] In a specific embodiment, the first acquisition unit is specifically used to use a one-variable quadratic statistical regression method to determine the relationship model between the frequency of each pore throat radius and the porosity. The values ​​of A'(i), B'(i) and C'(i) in are used to determine the relationship model between the frequency of each pore throat radius and porosity; where amp(i) is the frequency of the i-th pore throat radius, %. is the porosity, %; A'(i), B'(i) and C'(i) are coefficients, whose values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data;

[0086] In a specific embodiment, the second model determination submodule is specifically used to use a one-variable quadratic statistical regression method to determine the relationship model between the frequencies of N pore throat radii. The values ​​of a(i), b(i) and c(i) in are used to determine the relationship model between the frequencies of N pore throat radii.

[0087] In the above-mentioned acquisition system, preferably, the pore throat radius distribution spectrum acquisition module is specifically used to plot, for each depth of the target reservoir, N pore throat radii as logarithmic horizontal coordinates and the frequencies of N pore throat radii as linear vertical coordinates to obtain the pore throat radius distribution spectrum at the depth of the target reservoir.

[0088] The technical solution provided by the present invention can continuously construct a reservoir pore throat radius distribution spectrum from a conventional porosity curve, so as to achieve the purpose of continuously and quantitatively characterizing the reservoir pore structure and evaluating the reservoir effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 The pore throat radius distribution diagram of three representative cores from reservoir A in a certain block.

[0090] Figure 2 This is a flow chart of a method for obtaining a reservoir pore throat radius distribution spectrum provided in one embodiment of the present invention.

[0091] Figure 3 A framework diagram of a reservoir pore throat radius distribution spectrum acquisition system provided in one embodiment of the present invention.

[0092] Figure 4 The porosity of 90 cores in Example 1 of the present invention is The pore throat radius R corresponding to the 12th mercury injection pressure is c (12) = 0.072 μm) and the correlation between the frequency amp (12).

[0093] Figure 5 This is a morphological comparison diagram of the pore throat radius distribution spectrum obtained for a core sample in Example 1 of the present invention using the method provided by the present invention and the pore throat radius distribution spectrum obtained according to the core mercury injection capillary pressure experiment.

[0094] Figure 6 This is the pore throat radius distribution spectrum of the target reservoir in Example 1 of the present invention. DETAILED DESCRIPTION

[0095] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0096] When evaluating the pore structure of a reservoir using the pore throat radius distribution spectrum obtained by the existing mercury injection capillary pressure curve, there is a problem that the number of cores is small and the pore structure of the rock cannot be continuously and quantitatively characterized. In order to overcome the deficiency of the existing use of the core pore throat radius distribution spectrum that cannot continuously and quantitatively evaluate the pore structure of the reservoir and to realize continuous evaluation of the pore structure of the reservoir in the formation, the inventors have established a method of obtaining the reservoir pore throat radius distribution spectrum using porosity based on an in-depth analysis of the core capillary pressure curve and the obtained pore throat radius distribution spectrum. This method can obtain the pore throat radius distribution of the reservoir using the porosity that can be determined by conventional well logging; when the reservoir pore throat radius distribution spectrum is obtained using this method, it can be achieved on the basis of calibration using the limited core capillary pressure curve and using the porosity curve that is easy to calculate by conventional well logging to continuously construct the reservoir pore throat radius distribution spectrum, so as to use it to continuously and quantitatively characterize the reservoir pore structure.

[0097] The following uses the porosity, capillary mercury injection pressure, and corresponding pore throat radius distribution spectrum of three representative cores taken from reservoir A in a certain block as an example to illustrate. The experimental data of the porosity, capillary pressure, and corresponding pore throat radius distribution spectrum of the three representative cores are shown in Table 1. As can be seen from Table 1, the number of points used in this batch of experiments is 13. For the core samples in the same batch of mercury injection experiments, the applied mercury injection pressure is the same. Based on the known correlation between pore throat radius and capillary pressure, the corresponding pore throat radius point distribution method is also the same, and the point distribution method is:

[0098]

[0099] Where R c (i) is the radius of the i-th pore throat, μm.

[0100] Therefore, the differences in pore structure and pore throat radius of rocks are mainly reflected by the frequencies corresponding to different pore throat radius distribution intervals. For rocks with better pore structure, the frequency values ​​corresponding to the larger pore throat radius distribution intervals are higher. Conversely, for rocks with poorer pore structure, the frequency values ​​corresponding to the smaller pore throat radius distribution intervals are higher. The pore throat radius distribution spectra of three cores representing different pore structures are shown in Figure 2. Figure 1 Therefore, it is only necessary to calculate the different pore throat radii R c(i) corresponds to the frequency value amp(i), which can be used to obtain the rock pore throat radius distribution spectrum. The pore throat radius distribution spectrum can then be used to evaluate the rock pore structure. Porosity is a macroscopic factor that measures rock pore structure, and therefore, it must be closely related to the pore throat radius distribution spectrum. Based on this, a correlation can be established between rock porosity and the frequency corresponding to the pore throat radius. Using this correlation, the frequency values ​​corresponding to different pore throat radii can be obtained from the porosity curve. Combining the known pore throat radius with the corresponding frequency values, the pore throat radius distribution spectrum can be constructed.

[0101] Table 1 Capillary pressure curves of three representative cores and corresponding experimental data of pore throat radius distribution

[0102]

[0103] See also Figure 2 A specific embodiment of the present invention provides a method for obtaining a reservoir pore throat radius distribution spectrum, wherein the method comprises:

[0104] Step S1: obtaining a porosity curve of a target reservoir, i.e., a curve showing porosity variation with depth;

[0105] Step S2: Determine the point distribution method, and then determine N pore throat radii;

[0106] Step S3: Obtaining a relationship model between the frequency of the rated pore throat radius and the porosity and a relationship model between the frequencies of N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii;

[0107] Step S4: Based on the porosity curve of the target reservoir, the frequency of the N pore throat radii at each depth of the target reservoir is determined by using the relationship model between the frequency of the rated pore throat radius and the porosity, and the relationship model between the frequencies of the N pore throat radii, thereby determining the pore throat radius distribution spectrum at each depth of the target reservoir.

[0108] Furthermore, in step S1, obtaining the porosity curve of the target reservoir includes:

[0109] Step S11: Acquire porosity logging data of the target reservoir;

[0110] Among them, the porosity logging data of the target reservoir can be collected using conventional logging instruments;

[0111] Step S12: determining a porosity curve of the target reservoir based on the porosity logging data of the target reservoir;

[0112] The porosity curve of the target reservoir can be determined based on the porosity logging data of the target reservoir by conventional methods in the art, for example, by calculation using a core calibration logging method.

[0113] The point distribution method can be determined based on the mercury injection test of the sampled core in the target reservoir area; further, the N pore throat radii determined in step S2 are:

[0114]

[0115] Where R c (i) is the i-th pore throat radius, μm; N is the number of pore throat radius distribution points, and its value is generally greater than or equal to 13, preferably between 13-48.

[0116] In a specific embodiment, the value of N is 13;

[0117] Furthermore, the rated pore throat radius is the pore throat radius when i=11, 12, 13, 14, or 15.

[0118] Furthermore, the rated pore throat radius is 0.14 μm-0.009 μm;

[0119] In a specific embodiment, the nominal pore throat radius is 0.072 μm.

[0120] Furthermore, the relationship model between the frequency of the rated pore throat radius and porosity is:

[0121]

[0122] Where amp(E) is the frequency of the rated pore throat radius, %; is the porosity, %; A', B' and C' are coefficients, and their values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data.

[0123] Furthermore, the relationship model between the frequencies of the N pore throat radii is:

[0124]

[0125] Where amp(i) is the frequency of the i-th pore throat radius; a(i), b(i), and c(i) are coefficients, whose values ​​can be obtained by calibration using core mercury injection test data; and E is the i value corresponding to the rated pore throat radius, that is, the sequence number of the rated pore throat radius among the N pore throat radii.

[0126] Furthermore, in step S3, the relationship model between the frequency of the rated pore throat radius and the porosity and the relationship model between the frequencies of the N pore throat radii are obtained, including:

[0127] Obtain the porosity of the core used for model calibration;

[0128] Obtain mercury injection experimental data of rock cores for model calibration;

[0129] Based on the mercury injection experimental data of the core used for model calibration, the frequencies corresponding to the N pore throat radii of each core are determined respectively;

[0130] Determine a relationship model between the frequency of the rated pore throat radius and the porosity based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core;

[0131] Determining a relationship model between the frequencies of the N pore throat radii based on the frequencies corresponding to the N pore throat radii of each core;

[0132] Furthermore, based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, a relationship model between the frequency of the rated pore throat radius and the porosity is determined, including:

[0133] Based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, respectively determine a relationship model between the frequency of each pore throat radius and the porosity;

[0134] Among the relationship models between the frequency of each pore throat radius and porosity, the model with the best correlation is selected as the relationship model between the frequency of the rated pore throat radius and porosity; the pore throat radius corresponding to the model is the rated pore throat radius;

[0135] Furthermore, based on the mercury injection experimental data of the core used for model calibration, the frequencies corresponding to the N pore throat radii of each core are determined respectively by the following formula:

[0136] amp(1)=S Hg (1)

[0137] amp(i)=S Hg (i)-S Hg (i-1), i=2,3,…,N

[0138] Where S Hg (i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius;

[0139] Furthermore, the obtaining of mercury injection experimental data of the core for model calibration includes:

[0140] Based on N pore throat radii, the mercury injection pressure corresponding to the N pore throat radii is determined respectively;

[0141] Based on the mercury injection pressure corresponding to N pore throat radii, mercury injection experiments are carried out on each core to obtain the mercury saturation corresponding to each mercury injection pressure;

[0142] Furthermore, the core used for model calibration is taken from the area where the target reservoir is located;

[0143] In a specific embodiment, based on the porosity of each core and the frequency corresponding to the N pore throat radii of each core, when determining the relationship model between the frequency of each pore throat radius and the porosity, a one-variable quadratic statistical regression method can be used to determine the relationship model between the frequency of each pore throat radius and the porosity. The values ​​of A'(i), B'(i) and C'(i) in the formula are used to determine the relationship model between the frequency of each pore throat radius and porosity; where amp(i) is the frequency of the i-th pore throat radius, % is the porosity, %; A'(i), B'(i) and C'(i) are coefficients, whose values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data;

[0144] In a specific embodiment, based on the frequencies corresponding to the N pore throat radii of each core, when determining the relationship model between the frequencies of the N pore throat radii, a method of univariate quadratic statistical regression can be used to determine the relationship model between the frequencies of the N pore throat radii. The values ​​of a(i), b(i) and c(i) in are used to determine the relationship model between the frequencies of N pore throat radii.

[0145] Furthermore, in step S4, determining the pore throat radius distribution spectrum at each depth of the target reservoir includes:

[0146] For each depth of the target reservoir, a plot is drawn with N pore throat radii as logarithmic abscissas and the frequencies corresponding to the N pore throat radii as linear ordinates to obtain the pore throat radius distribution spectrum at the depth of the target reservoir.

[0147] An embodiment of the present invention further provides a system for acquiring a reservoir pore throat radius distribution spectrum, which is used to implement the above-mentioned embodiment of the method for acquiring a reservoir pore throat radius distribution spectrum.

[0148] Figure 3 : is a structural block diagram of a reservoir pore throat radius distribution spectrum acquisition system according to an embodiment of the present invention, the system comprising:

[0149] Porosity curve acquisition module 21: used to obtain the porosity curve of the target reservoir, that is, the curve showing the change of porosity with depth;

[0150] The pore throat radius determination module 22 is used to determine the point distribution method and then determine N pore throat radii;

[0151] Model acquisition module 23: used to obtain a relationship model between the frequency of the rated pore throat radius and the porosity, and a relationship model between the frequencies of N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii;

[0152] The pore throat radius distribution spectrum acquisition module 24 is used to determine the frequencies of the N pore throat radii at each depth of the target reservoir based on the porosity curve of the target reservoir, using the relationship model between the frequency of the rated pore throat radius and the porosity, and the relationship model between the frequencies of the N pore throat radii, thereby determining the pore throat radius distribution spectrum at each depth of the target reservoir.

[0153] Furthermore, the porosity curve acquisition module 21 includes:

[0154] Logging data acquisition submodule 211: used to acquire porosity logging data of the target reservoir;

[0155] The porosity curve determination submodule 212 is configured to determine the porosity curve of the target reservoir based on the porosity logging data of the target reservoir.

[0156] Furthermore, the N pore throat radii determined by the pore throat radius determination module 22 are:

[0157]

[0158] Where R c (i) is the i-th pore throat radius, μm; N is the number of pore throat radius distribution points, and its value is generally greater than or equal to 13, preferably between 13-48.

[0159] In a specific embodiment, the value of N is 13;

[0160] Furthermore, the rated pore throat radius is the pore throat radius when i=11, 12, 13, 14 or 15.

[0161] Furthermore, the rated pore throat radius is 0.14 μm-0.009 μm;

[0162] In a specific embodiment, the nominal pore throat radius is 0.072 μm.

[0163] Furthermore, the relationship model between the frequency of the rated pore throat radius and porosity is:

[0164]

[0165] Where amp(E) is the frequency of the rated pore throat radius, %; is the porosity, %; A', B' and C' are coefficients, and their values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data.

[0166] Furthermore, the relationship model between the frequencies of the N pore throat radii is:

[0167]

[0168] Where amp(i) is the frequency of the i-th pore throat radius; a(i), b(i), and c(i) are coefficients, whose values ​​can be obtained by calibration using core mercury injection test data; and E is the i value corresponding to the rated pore throat radius, that is, the sequence number of the rated pore throat radius among the N pore throat radii.

[0169] Furthermore, the pore throat radius distribution spectrum acquisition module 24 includes:

[0170] Porosity acquisition submodule 241: used to obtain the porosity of the core used for model calibration;

[0171] Mercury injection data acquisition submodule 242: used to obtain mercury injection experimental data of the core for model calibration;

[0172] Frequency determination submodule 243: used to determine the frequencies corresponding to the N pore throat radii of each core based on mercury injection experimental data of the core used for model calibration;

[0173] The first model determination submodule 244 is configured to determine a relationship model between the frequency of the rated pore throat radius and the porosity based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core;

[0174] The second model determination submodule 245 is configured to determine a relationship model between the frequencies of the N pore throat radii based on the frequencies corresponding to the N pore throat radii of each core;

[0175] Furthermore, the first model determination submodule 244 includes:

[0176] The first acquisition unit 2441 is configured to determine a relationship model between the frequency and porosity of each pore throat radius based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core;

[0177] The second acquisition unit 2442 is configured to select a model with the best correlation among the relationship models between the frequencies of the pore throat radii and the porosity as the relationship model between the frequencies of the rated pore throat radii and the porosity; the pore throat radius corresponding to the model is the rated pore throat radius;

[0178] Furthermore, the frequency determination submodule 243 determines the frequencies corresponding to the N pore throat radii of each core using the following formula:

[0179] amp(1)=S Hg (1)

[0180] amp(i)=S Hg (i)-S Hg (i-1), i=2,3,…,N

[0181] Where S Hg(i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius;

[0182] Furthermore, the mercury intrusion data acquisition submodule 242 includes:

[0183] The mercury injection pressure determining unit 2421 is used to determine the mercury injection pressures corresponding to the N pore throat radii based on the N pore throat radii;

[0184] The mercury injection saturation acquisition unit 2422 is used to perform a mercury injection test on each core based on the mercury injection pressure corresponding to N pore throat radii, and obtain the mercury injection saturation corresponding to each mercury injection pressure;

[0185] Furthermore, the core used for model calibration is taken from the area where the target reservoir is located;

[0186] In a specific embodiment, the first acquisition unit 2441 is specifically used to use a one-variable quadratic statistical regression method to determine the relationship model between the frequency of each pore throat radius and the porosity. The values ​​of A'(i), B'(i) and C'(i) in are used to determine the relationship model between the frequency of each pore throat radius and porosity; where amp(i) is the frequency of the i-th pore throat radius, %. is the porosity, %; A'(i), B'(i) and C'(i) are coefficients, whose values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data;

[0187] wherein, based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, a relationship model between the frequency of the rated pore throat radius and the porosity is determined;

[0188] In a specific embodiment, the second model determination submodule 245 is specifically used to use a one-variable quadratic statistical regression method to determine the relationship model between the frequencies of the pore throat radii. The values ​​of a(i), b(i) and c(i) in are used to determine the relationship model between the frequencies of each pore throat radius.

[0189] Furthermore, the pore throat radius distribution spectrum acquisition module 24 is specifically used to plot, for each depth of the target reservoir, N pore throat radii as logarithmic horizontal coordinates and the frequencies corresponding to the N pore throat radii as linear vertical coordinates to obtain the pore throat radius distribution spectrum at the depth of the target reservoir.

[0190] Example 1

[0191] A method for obtaining a reservoir pore throat radius distribution spectrum is used to identify the pore throat radius distribution spectrum of a sandstone conglomerate formation (serving as a target reservoir) in an exploration well A in a certain block.

[0192] The method is carried out in the following steps:

[0193] 1. Obtain porosity logging data of the target reservoir, and determine the porosity curve of the target reservoir based on the porosity logging data of the target reservoir;

[0194] The results are as follows Figure 6 shown.

[0195] 2. Determine the point distribution method and then determine the 13 pore throat radii R c (i)

[0196]

[0197] Where R c (i) is the radius of the i-th pore throat, μm.

[0198] 3. Obtain the relationship model between the frequency of the rated pore throat radius and porosity, and the relationship model between the frequencies of N pore throat radii; specifically, including:

[0199] 3.1. Select 90 representative core samples from the target reservoir area as cores for model calibration.

[0200] 3.2. Conduct conventional physical property and mercury injection tests on 90 cores used for model calibration to obtain core porosity and mercury injection test data;

[0201] In the process of obtaining mercury injection test data, based on the 13 pore throat radii determined in step 2, the mercury injection pressures corresponding to the 13 pore throat radii are determined respectively. Based on the mercury injection pressures corresponding to the 13 pore throat radii, mercury injection tests are performed on each core to obtain the mercury saturation corresponding to each mercury injection pressure.

[0202] 3.3 Based on the mercury injection experimental data of the core used for model calibration, the frequency amp(i) corresponding to the 13 pore throat radii of each core is determined by the following formula:

[0203] amp(1)=S Hg (1)

[0204] amp(i)=S Hg (i)-S Hg (i-1), i=2,3,…,N

[0205] Where S Hg (i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius.

[0206] 3.4. Using the quadratic statistical regression method, the relationship model between the frequency of each pore throat radius and porosity is determined The values ​​of A'(i), B'(i) and C'(i) in are used to determine the relationship model between the frequency of each pore throat radius and porosity; where amp(i) is the frequency of the i-th pore throat radius, %. is the porosity, %; A'(i), B'(i) and C'(i) are coefficients, whose values ​​can be obtained by calibration of core mercury injection test and conventional physical property test data;

[0207] Among the relationship models between the frequency of each pore throat radius and porosity, the model with the best correlation is selected as the relationship model between the frequency of the rated pore throat radius and porosity; the pore throat radius corresponding to the model is the rated pore throat radius;

[0208] Determine the 12th pore throat radius (R c (12) = 0.072 μm) as the rated pore throat radius, and the relationship model between the frequency of the rated pore throat radius and the porosity is: like Figure 4 shown.

[0209] 3.5. Using the quadratic statistical regression method, the relationship model between the frequencies of each pore throat radius is determined. The values ​​of a(i), b(i) and c(i) in are used to determine the relationship model between the frequencies of each pore throat radius.

[0210] Analysis of 90 cores with different pore throat radii R c The results of the correlation between the frequency values ​​amp(i) corresponding to the pore-throat radius are shown in Table 2. As can be seen from the table, for all 90 core samples, the correlation between the frequencies corresponding to two adjacent pore-throat radii is the strongest. As the difference in pore-throat radius increases, the correlation between the corresponding frequencies decreases.

[0211] Table 2 Correlation between frequencies corresponding to different pore throat radii

[0212]

[0213]

[0214] Based on the correlations between frequencies corresponding to different pore-throat radii shown in Table 2, and combined with the mercury injection test results from 90 representative core samples in this example, the values ​​of a(i), b(i), and c(i) in the relationship model between frequencies for each pore-throat radius were calibrated. This calibrated frequency calculation model for each pore-throat radius was obtained, as shown in Table 3.

[0215] Table 3 Frequency calculation models corresponding to different pore throat radii

[0216] serial number Pore ​​throat radius (μm) Frequency prediction model corresponding to each pore throat radius 1 0.036 <![CDATA[amp(13)=0.0646×[amp(12)] 2 -0.229×amp(12)+5.23]]> 2 0.144 <![CDATA[amp(11)=-0.0014×[amp(12)] 2 +0.520×amp(12)+2.23]]> 3 0.287 <![CDATA[amp(10)=0.0737×[amp(11)] 2 -0.356×amp(11)+4.67]]> 4 0.574 <![CDATA[amp(9)=0.0371×[amp(10)] 2 +0.023×amp(10)+3.63]]> 5 1.148 <![CDATA[amp(8)=0.0058×[amp(9)] 2 +0.251×amp(9)+2.73]]> 6 2.297 <![CDATA[amp(7)=0.0422×[amp(8)] 2 -0.206×amp(8)+0.35]]> 7 4.594 <![CDATA[amp(6)=0.1747×[amp(7)] 2 -1.047×amp(7)+5.02]]> 8 9.188 <![CDATA[amp(5)=0.7191×[amp(6)] 2 -8.526×amp(6)+23.53]]> 9 18.375 amp(4)=0.0 10 36.750 amp(3)=0.0 11 73.500 amp(2)=0.0 12 147.000 amp(1)=0.0

[0217] In order to determine the credibility of the established model, for a certain core, the frequency-porosity relationship model of the rated pore throat radius determined in step 3.4 is used to calculate the porosity of the core. After calculating the value of amp(12), we further calculate the frequency values ​​corresponding to other pore throat radii using the successive iteration method based on the relationship model between the frequencies of the pore throat radii established in step 3.5, and then calculate the frequency values ​​corresponding to the known pore throat radius R. c (i) is the logarithmic horizontal axis, with different pore throat radii R calculated c (i) The corresponding frequency amp(i) is plotted as a linear ordinate to obtain the pore throat radius distribution spectrum of the core. The results are as follows: Figure 5 shown. Figure 5 This is a morphological comparison diagram of the pore throat radius distribution spectrum obtained using the method of the present invention and the pore throat radius distribution spectrum actually obtained using the core mercury injection experiment. It can be seen from the figure that the two are basically consistent in the main distribution range and frequency, which proves the credibility of the model established in this embodiment and the effectiveness of the method of the present invention.

[0218] The core used in the embodiment of the present invention was taken from a sandstone reservoir with a relatively dense rock. The main pore throat radius distribution range is between 0.036 and 18.375 μm. Therefore, Table 2 only analyzes the correlation between the frequencies corresponding to different pore throat radii when the pore throat radius is less than 18.375 μm. At the same time, when using the successive iteration method to calculate the frequencies corresponding to different pore throat radii, only the frequency values ​​of pore throat radii less than 18.375 μm are calculated. Therefore, Table 3 only gives the frequency prediction model corresponding to different pore throat radii when the pore throat radius is less than 18.375 μm.

[0219] 4. Based on the porosity curve of the target reservoir, the frequency of the N pore throat radii at each depth of the target reservoir is determined using the relationship model between the frequency of the rated pore throat radius and the porosity, and the relationship model between the frequencies of the N pore throat radii, thereby determining a pore throat radius distribution spectrum at each depth of the target reservoir; wherein, for each depth of the target reservoir, a plot is drawn with the N pore throat radii as logarithmic abscissas and the frequencies of the N pore throat radii as linear ordinates to obtain the pore throat radius distribution spectrum at that depth of the target reservoir;

[0220] The results are as follows Figure 6 shown.

[0221] Figure 6The effect diagram shown is divided into five tracks. The first track includes the natural gamma curve (GR), the natural potential curve (SP) and the caliper curve (CAL); the second track includes the density logging (DEN) curve, the neutron logging (CNL) curve and the acoustic transit time logging (AC) curve; the third track is the array induction resistivity curve; the PHIT in the fourth track is the porosity curve calculated using conventional density and neutron logging data; the fifth track RC_DIST is the reservoir pore throat radius distribution spectrum continuously obtained using the method provided by the embodiment of the present invention, and the black solid line is the average value of the pore throat radius distribution (often referred to as the average pore throat radius). It should be noted that for the convenience of software drawing, the obtained pore throat radius distribution spectrum is uniformly resampled into 30 points, and the pore throat radius distribution range is resampled to within the range of 0.01-100.0μm. From the shape of the pore throat radius distribution spectrum obtained in the figure, it can be seen that the pore throat radius of this layer is mainly distributed between 0.01-3.0μm. This shows that the reservoir pore throat radius is small and the pore structure is poor. However, in the 2157.0-2177.0 m well section, the distribution range of the pore throat radius distribution spectrum obtained is significantly wider, mainly distributed in the range of 0.01-20.0 μm. It is judged that large pore throats are dominant in this layer, and the pore structure is relatively good. This judgment is confirmed by the oil test data. The oil test results of the 2138.0-2170.0 m well section show that the daily oil production is 221.0 cubic meters and the daily gas production is 1.054×10 4 m 3 , which is a high-yield oil and gas layer, verifying the reliability of using pore throat radius distribution spectrum to identify effective reservoirs.

[0222] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for obtaining a reservoir pore throat radius distribution spectrum, wherein: The method includes: Obtain the porosity curve of the target reservoir, i.e., the curve showing the change of porosity with depth; Determine the point distribution method and then determine N pore throat radii; Obtaining a relationship model between the frequency of a rated pore throat radius and porosity, and a relationship model between the frequencies of N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii; Based on the porosity curve of the target reservoir, the frequencies of the N pore throat radii at each depth of the target reservoir are determined using the relationship model between the frequency of the rated pore throat radius and the porosity, and the relationship model between the frequencies of the N pore throat radii, thereby determining the pore throat radius distribution spectrum at each depth of the target reservoir; Wherein, the N pore throat radii determined are: Where R c (i) is the radius of the i-th pore throat, μm; N is greater than or equal to 13; Wherein, the rated pore throat radius is the pore throat radius when i=11, 12, 13, 14, or 15; The relationship model between the frequency of the rated pore throat radius and the porosity is: Where amp(E) is the frequency of the rated pore throat radius, %; is the porosity, %; A', B' and C' are coefficients; The relationship model between the frequencies of the N pore throat radii is: Where amp(i) is the frequency of the i-th pore throat radius; a(i), b(i) and c(i) are coefficients; and E is the value of i corresponding to the rated pore throat radius.

2. The method according to claim 1, wherein N is 13-48.

3. The method according to claim 1 or 2, wherein: The rated pore throat radius is 0.14 μm-0.009 μm.

4. The method according to claim 1, wherein The relationship model between the frequency of obtaining the rated pore throat radius and the porosity, and the relationship model between the frequencies of N pore throat radii include: Obtain the porosity of the core used for model calibration; Obtain mercury injection experimental data of rock cores for model calibration; Based on the mercury injection experimental data of the core used for model calibration, the frequencies corresponding to the N pore throat radii of each core are determined respectively; Determine a relationship model between the frequency of the rated pore throat radius and the porosity based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core; Based on the frequencies corresponding to the N pore throat radii of each core, a relationship model between the frequencies of the N pore throat radii is determined.

5. The method according to claim 4, wherein Based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, a relationship model between the frequency of the rated pore throat radius and the porosity is determined, including: Based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core, respectively determine a relationship model between the frequency of each pore throat radius and the porosity; Among the relationship models between the frequency of each pore throat radius and the porosity, the model with the best correlation is selected as the relationship model between the frequency of the rated pore throat radius and the porosity; the pore throat radius corresponding to the model is the rated pore throat radius.

6. The method according to claim 4, wherein: Based on the mercury injection experimental data of the core used for model calibration, the frequencies corresponding to the N pore throat radii of each core are determined by the following formula: amp(1)=S Hg (1) amp(i)=S Hg (i)-S Hg (i-1),i=2,3,…,N Where S Hg (i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius.

7. The method according to claim 4, wherein: The acquisition of mercury injection experimental data of the core for model calibration includes: Based on N pore throat radii, the mercury injection pressure corresponding to the N pore throat radii is determined respectively; Based on the mercury injection pressures corresponding to N pore throat radii, mercury injection experiments were performed on each core to obtain the mercury saturation corresponding to each mercury injection pressure.

8. The method according to claim 1, wherein Determining the pore throat radius distribution spectrum at each depth of the target reservoir includes: For each depth of the target reservoir, a plot is drawn with N pore throat radii as logarithmic abscissas and the frequencies of N pore throat radii as linear ordinates to obtain the pore throat radius distribution spectrum at the depth of the target reservoir.

9. A reservoir pore throat radius distribution spectrum acquisition system, wherein: The system includes: Porosity curve acquisition module: used to obtain the porosity curve of the target reservoir, that is, the curve showing the change of porosity with depth; Pore ​​throat radius determination module: used to determine the point distribution method and then determine N pore throat radii; Model acquisition module: used to obtain a relationship model between the frequency of the rated pore throat radius and the porosity, and a relationship model between the frequencies of N pore throat radii; wherein the rated pore throat radius is one of the N pore throat radii; A pore throat radius distribution spectrum acquisition module is configured to determine the frequencies of the N pore throat radii at each depth of the target reservoir based on the porosity curve of the target reservoir and using the relationship model between the frequency of the rated pore throat radius and the porosity and the relationship model between the frequencies of the N pore throat radii, thereby determining the pore throat radius distribution spectrum at each depth of the target reservoir; Among them, the N pore throat radii determined by the pore throat radius determination module are: Where R c (i) is the radius of the i-th pore throat, μm; N is greater than or equal to 13; Wherein, the rated pore throat radius is the pore throat radius when i=11, 12, 13, 14, or 15; The relationship model between the frequency of the rated pore throat radius and the porosity is: Where amp(E) is the frequency of the rated pore throat radius, %; is the porosity, %; A', B' and C' are coefficients; The relationship model between the frequencies of the N pore throat radii is: Where amp(i) is the frequency of the i-th pore throat radius; a(i), b(i) and c(i) are coefficients; and E is the value of i corresponding to the rated pore throat radius.

10. The system according to claim 9, wherein: N is 13-48.

11. The system according to claim 9 or 10, wherein: The rated pore throat radius is 0.14 μm-0.009 μm.

12. The system of claim 9, wherein: The pore throat radius distribution spectrum acquisition module includes: Porosity acquisition submodule: used to obtain the porosity of the core used for model calibration; Mercury injection data acquisition submodule: used to obtain mercury injection experimental data of cores for model calibration; Frequency determination submodule: used to determine the frequencies corresponding to the N pore throat radii of each core based on the mercury injection experimental data of the core used for model calibration; A first model determination submodule is used to determine a relationship model between the frequency of the rated pore throat radius and the porosity based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core; The second model determination submodule is configured to determine a relationship model between the frequencies of the N pore throat radii based on the frequencies corresponding to the N pore throat radii of each core.

13. The system according to claim 12, wherein the first model determination submodule comprises: A first acquisition unit is configured to determine a relationship model between the frequency and porosity of each pore throat radius based on the porosity of each core and the frequencies corresponding to the N pore throat radii of each core; The second acquisition unit is used to select a model with the best correlation among the relationship models between the frequencies of the pore throat radii and the porosity as the relationship model between the frequencies of the rated pore throat radius and the porosity; wherein the pore throat radius corresponding to the model is the rated pore throat radius.

14. The system according to claim 12, wherein: The frequency determination submodule determines the frequencies corresponding to the N pore throat radii of each core using the following formula: amp(1)=S Hg (1) amp(i)=S Hg (i)-S Hg (i-1),i=2,3,…,N Where S Hg (i) is the mercury saturation corresponding to the mercury injection pressure corresponding to the i-th pore throat radius, %; amp(i) is the frequency of the i-th pore throat radius.

15. The system according to claim 12, wherein: The mercury injection data acquisition submodule includes: Mercury injection pressure determination unit: used to determine the mercury injection pressure corresponding to N pore throat radii based on N pore throat radii; Mercury injection saturation acquisition unit: used to perform mercury injection experiments on each core based on the mercury injection pressure corresponding to N pore throat radii, and obtain the mercury injection saturation corresponding to each mercury injection pressure.

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