Methods, systems, and electronic equipment for calculating effective porosity at T2 cutoff values ​​in fine-grained lithology

Abstract

The application discloses a kind of fine lithology variable T2 cut-off effective pore calculation method, system and electronic equipment, belong to complex lithology oil and gas reservoir well logging evaluation technical field, based on nuclear magnetic resonance logging data's sandy conglomerate reservoir, on the basis of accurately dividing lithology, comprehensively consider the influencing factor of rock composition and pore structure, establish the effective porosity calculation model of different nuclear magnetic T2 cut-off value by lithology, using the method of lithology fitting formula, without relying on a large number of nuclear magnetic experiment calibration, can utilize conventional logging, nuclear magnetic resonance T2 spectrum data and experimental pore structure data, realize the effective porosity calculation of complex lithology, and compared with fixed T2 cut-off value calculation effective porosity, greatly improve the calculation precision of reservoir effective porosity, can provide key parameters for reservoir physical property evaluation, saturation calculation contains, convenient and fast, conducive to the rapid scale application on production, with good universality and popularization value.

Description

Technical Field

[0001] This invention belongs to the field of logging evaluation technology for complex lithological oil and gas reservoirs, specifically involving a method, system, and electronic equipment for calculating effective porosity based on the T2 cutoff value of subdivided lithological variations. Background Technology

[0002] Nuclear magnetic resonance (NMR) logging, as a logging method that can directly provide information on reservoir porosity and its distribution, plays an increasingly important role in oil and gas reservoir exploration and development. By processing and interpreting NMR T2 spectra, parameters reflecting reservoir total porosity, effective porosity, bound water saturation, movable oil saturation, and permeability can be obtained. The magnitude of the T2 cutoff is crucial influencing these NMR parameters. Studies have found that the T2 spectrum distribution is not only closely related to the size and distribution of rock porosity but also to lithology, measurement parameters, and clay content. Complex lithological reservoirs exhibit diverse internal sedimentary characteristics and structures, resulting in complex and varied reservoir lithology and pore structures. Calculating effective porosity by fixing the T2 cutoff value cannot accurately characterize rock porosity. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method, system and electronic device for calculating effective porosity with a subdivided lithological T2 cutoff value, so as to solve the technical problem that the calculation of effective porosity with a fixed T2 cutoff value in the prior art cannot accurately characterize the porosity of rocks.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A method for calculating the effective pore size with varying T2 cutoff values ​​for subdivided lithology includes the following steps:

[0006] Based on lithological classification, the T2 spectral characteristics of nuclear magnetic resonance for different lithologies were extracted;

[0007] Based on the helium porosity of different lithologies, and by comparing the characteristics of nuclear magnetic resonance T2 spectra, the effective porosity T2 cutoff value for each lithology was calculated using an inversion iterative method.

[0008] Based on the main controlling factors of the effective porosity T2 cutoff value of nuclear magnetic resonance, calculation models for the effective porosity T2 cutoff value of nuclear magnetic resonance were established according to lithology.

[0009] The T2 cutoff value of the reservoir is calculated using a nuclear magnetic resonance (NMR) effective porosity T2 cutoff value calculation model. Combined with the NMR porosity calculation formula, the effective porosity of the reservoir is then calculated.

[0010] Preferably, based on nuclear magnetic resonance logging data, the effective porosity T2 cutoff value characteristics of nuclear magnetic resonance T2 spectra for different lithologies are statistically analyzed.

[0011] Preferably, based on the NMR spectral characteristics of different lithologies and in comparison with the T2 spectral characteristics of NMR, the effective pore T2 cutoff value for different lithologies is obtained by inversion and iteration using equation (1), and finally the effective pore T2 cutoff value is determined according to the root mean square error equation (2):

[0012]

[0013]

[0014] In the formula, T 2cutoff T2 is the effective aperture cutoff value for nuclear magnetic resonance; T 2max φ is the maximum relaxation time of nuclear magnetic resonance. k Porosity calculated for different T2 cutoff values; φ is the effective porosity. XI is the actual value. is the predicted value, and n is the number of samples.

[0015] Preferably, the effective T2 cutoff value determined according to the root mean square error formula (2) is the effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology if the root mean square error is less than 2.5.

[0016] Preferably, the main controlling factors include average capillary radius, sorting coefficient, displacement pressure, clay content, and clay type.

[0017] Preferably, based on the main controlling factors of the effective pore T2 cutoff value of nuclear magnetic resonance, a comprehensive pore structure index is constructed by formula (3), a comprehensive logging pore structure index is constructed by formula (4), and finally, a calculation model for the effective pore T2 cutoff value of nuclear magnetic resonance is established by formula (5) according to lithology.

[0018]

[0019]

[0020] T 2变 =e·PZ 测井 +f·TS-g·V cl d (5)

[0021] In the formula, SP is the sorting coefficient; RC is the average capillary radius; Pd is the exhaust pressure; a is an empirical coefficient; φ D Porosity is calculated for density; CNL is the neutron logging value; RT is the formation resistivity logging value; b is an empirical coefficient; c is an empirical coefficient; e is an empirical coefficient; f is an empirical coefficient; TS is the rock particle sorting value; g is an empirical coefficient; V cl t is clay content; TS is rock particle sorting calculated by electrical imaging; d is clay type coefficient; g 2变 This is the T2 cutoff value for reservoir variation.

[0022] Preferably, the reservoir's variable T2 cutoff value is calculated using a nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and the reservoir's effective porosity is calculated using a nuclear magnetic resonance porosity calculation formula.

[0023]

[0024] In the formula, T 2max T is the maximum relaxation time of nuclear magnetic resonance; 2变 The T2 cutoff value for reservoir variation; φ k Porosity calculated for different T2 cutoff values; φ is the effective porosity.

[0025] This invention also discloses a system for calculating effective pore size with varying T2 cutoff values ​​for subdivided lithology, comprising:

[0026] The extraction unit is used to extract the T2 spectral characteristics of different lithologies based on lithological classification;

[0027] The first calculation unit is used to calculate the effective porosity T2 cutoff value for each type of lithology based on the helium porosity of different lithologies and the characteristics of nuclear magnetic resonance T2 spectra, by means of an inversion iterative method.

[0028] The model building unit is used to determine and establish a calculation model for the effective porosity T2 cutoff value of nuclear magnetic resonance based on the main controlling factors of the effective porosity T2 cutoff value of nuclear magnetic resonance according to lithology.

[0029] The second calculation unit is used to calculate the reservoir's variable T2 cutoff value using the nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and to calculate the reservoir's effective porosity using the nuclear magnetic resonance porosity calculation formula.

[0030] The present invention also discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the effective pore size calculation method for the variable T2 cutoff value of subdivided lithology described above.

[0031] The present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for calculating the effective pore size of the variable T2 cutoff value for subdivided lithology as described above.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] A method for calculating effective porosity with varying T2 cutoff values ​​based on lithological subdivisions is presented for sandstone and conglomerate reservoirs using nuclear magnetic resonance (NMR) logging data. This method, based on accurate lithological classification, comprehensively considers the influence of rock composition and pore structure, establishing effective porosity calculation models with different NMR T2 cutoff values ​​for each lithology. This method is used to calculate the effective porosity of sandstone and conglomerate reservoirs in oilfield exploration and development. The method for calculating effective porosity with varying T2 cutoff values ​​in complex lithological reservoirs based on NMR logging data mentioned in this invention has a rigorous theoretical foundation and clear physical meaning of the formulas. In practical applications, the method uses lithological fitting formulas, eliminating the need for extensive NMR experimental calibration. It can utilize conventional logging, NMR T2 spectrum data, and experimental pore structure data to calculate the effective porosity of complex lithologies. Compared with calculating effective porosity with a fixed T2 cutoff value, this invention significantly improves the accuracy of reservoir effective porosity calculation, providing key parameters for reservoir property evaluation and saturation calculation. It is convenient and fast, conducive to rapid large-scale application in production, and has good universality and promotional value. Attached Figure Description

[0034] Figure 1 This is a flowchart of a method for calculating the effective pore size of varying T2 cutoff values ​​for subdivided lithology according to the present invention;

[0035] Figure 2 This is a diagram showing the inversion and iteration results of the effective porosity T2 cutoff value of this invention;

[0036] Figure 3 This is a correlation coefficient diagram between reservoir parameters and effective pore T2 cutoff values ​​according to the present invention;

[0037] Figure 4 This is a graph showing the calculation results of the effective porosity of the variable T2 cutoff value in this invention;

[0038] Figure 5 This is a schematic diagram of an effective pore size calculation system for varying T2 cutoff values ​​in lithology according to the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings:

[0042] Complex lithological reservoirs exhibit diverse internal sedimentary characteristics and structures, resulting in varied lithology and pore structures. Calculating effective porosity using a fixed T2 cutoff value cannot accurately characterize rock porosity. This invention provides a method for calculating effective porosity in complex lithological reservoirs using variable T2 cutoff values ​​based on nuclear magnetic resonance (NMR) logging data. By analyzing the main controlling factors of the NMR T2 cutoff value, a T2 cutoff value calculation formula is established for each lithology. Combined with the NMR porosity calculation formula, a method for calculating effective porosity with variable T2 cutoff values ​​is constructed, thereby achieving continuous and accurate calculation of effective porosity vertically. This method can quickly and accurately calculate reservoir effective porosity even without prior NMR experiments, providing technical support for the refined interpretation and evaluation of well logging reservoir parameters.

[0043] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0044] See Figure 1 A method for calculating the effective pore size of variable T2 cutoff value for subdivided lithology, characterized by comprising the following steps:

[0045] S1: Based on lithological classification, extract the T2 spectral characteristics of different lithologies using nuclear magnetic resonance;

[0046] S2: Based on the helium porosity of different lithologies, and by referring to the characteristics of nuclear magnetic resonance T2 spectra, the effective porosity T2 cutoff value for each lithology is calculated through an inversion iterative method.

[0047] S3: Determine and establish a calculation model for the effective porosity T2 cutoff value of nuclear magnetic resonance based on the main controlling factors of the effective porosity T2 cutoff value of nuclear magnetic resonance according to lithology;

[0048] S4: Calculate the reservoir's variable T2 cutoff value using the nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and then calculate the reservoir's effective porosity using the nuclear magnetic resonance porosity calculation formula.

[0049] This invention relates to sandstone and conglomerate reservoirs based on nuclear magnetic resonance (NMR) logging data. The method, based on accurate lithological classification, comprehensively considers the influence of rock composition and pore structure, establishing effective porosity calculation models with different NMR T2 cutoff values ​​for each lithology. This method calculates the effective porosity of sandstone and conglomerate reservoirs in oilfield exploration and development. The effective porosity calculation method for complex lithological reservoirs with varying T2 cutoff values ​​based on NMR logging data mentioned in this invention has a rigorous theoretical foundation and clear physical meaning of the formulas. In practical applications, the method uses lithological fitting formulas, eliminating the need for extensive NMR experimental calibration. It can utilize conventional logging, NMR T2 spectrum data, and experimental pore structure data to calculate the effective porosity of complex lithologies. Compared with calculations using fixed T2 cutoff values, this invention significantly improves the accuracy of reservoir effective porosity calculation, providing key parameters for reservoir property evaluation and saturation calculation. It is convenient and fast, conducive to rapid large-scale application in production, and has good universality and promotional value.

[0050] In some embodiments, in S1, based on nuclear magnetic resonance logging data, the effective porosity T2 cutoff value characteristics of nuclear magnetic resonance T2 spectra for different lithologies are statistically analyzed.

[0051] In some embodiments, in S2, based on the NMR spectral characteristics of different lithologies and compared with the NMR T2 spectral characteristics, the effective pore T2 cutoff value of different lithologies is inverted and iterated using Equation (1), and finally the effective pore T2 cutoff value is determined according to the root mean square error Equation (2):

[0052]

[0053]

[0054] In the formula, T 2cutoff T2 is the effective aperture cutoff value for nuclear magnetic resonance; T 2max φ is the maximum relaxation time of nuclear magnetic resonance. k Porosity calculated for different T2 cutoff values; φ is the effective porosity. XI is the actual value. is the predicted value, and n is the number of samples.

[0055] More preferably, the effective T2 cutoff value determined according to the root mean square error formula (2) is the effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology if the root mean square error is less than 2.5.

[0056] In some embodiments, the controlling factors include average capillary radius, sorting coefficient, displacement pressure, clay content, and clay type.

[0057] In some embodiments, based on the main controlling factors of the effective pore T2 cutoff value of nuclear magnetic resonance, a comprehensive pore structure index is constructed by equation (3), a comprehensive logging pore structure index is constructed by equation (4), and finally, a calculation model for the effective pore T2 cutoff value of nuclear magnetic resonance is established by equation (5) according to lithology.

[0058]

[0059]

[0060] T 2变 =e·PZ 测井 +f·TS-g·V cl d (5)

[0061] In the formula, SP is the sorting coefficient; RC is the average capillary radius; Pd is the exhaust pressure; a is an empirical coefficient; φ D Porosity is calculated for density; CNL is the neutron logging value, in %; RT is the formation resistivity logging value, in ohm·m; b is an empirical coefficient; c is an empirical coefficient; e is an empirical coefficient; f is an empirical coefficient; TS is the rock particle sorting calculation, in decimals, calculated from electrical imaging data; g is an empirical coefficient; V cl t is the clay content; TS is the rock particle sorting calculation, in decimals, calculated from electrical imaging data; d is the clay type coefficient; T 2变 This is the T2 cutoff value for reservoir variation.

[0062] In some embodiments, the reservoir's variable T2 cutoff value is calculated using a nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and the reservoir's effective porosity is calculated using a nuclear magnetic resonance porosity calculation formula.

[0063]

[0064] In the formula, T 2cutoff T2 cutoff value for effective aperture in nuclear magnetic resonance imaging, in milliseconds (ms). 2max φ is the maximum relaxation time of nuclear magnetic resonance (NMR), in milliseconds (ms). k Porosity calculated for different T2 cutoff values, in decimal units; φ is the effective porosity, in decimal units.

[0065] See Figure 5 The present invention also discloses a system for calculating effective pore size with varying T2 cutoff values ​​for subdivided lithology, comprising:

[0066] The extraction unit is used to extract the T2 spectral characteristics of different lithologies based on lithological classification;

[0067] The first calculation unit is used to calculate the effective porosity T2 cutoff value for each type of lithology based on the helium porosity of different lithologies and the characteristics of nuclear magnetic resonance T2 spectra, by means of an inversion iterative method.

[0068] The model building unit is used to determine and establish a calculation model for the effective porosity T2 cutoff value of nuclear magnetic resonance based on the main controlling factors of the effective porosity T2 cutoff value of nuclear magnetic resonance according to lithology.

[0069] The second calculation unit is used to calculate the reservoir's variable T2 cutoff value using the nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and to calculate the reservoir's effective porosity using the nuclear magnetic resonance porosity calculation formula.

[0070]

Example

[0071] See Figure 1 This invention provides a method for calculating the effective pore size of varying T2 cutoff values ​​for subdivided lithology, comprising the following steps:

[0072] Step 1: Based on lithological classification, extract the T2 spectral characteristics of different lithologies using nuclear magnetic resonance (NMR). According to the lithological classification results of the study area, the lithologies are divided into four categories: calcareous conglomerate, tuffaceous conglomerate, sandstone, and gravelly sandstone. Based on NMR logging data, the effective porosity T2 cutoff values ​​of the NMR T2 spectra of different lithologies are statistically analyzed.

[0073] Step 2: Based on the helium porosity of different lithologies, and by referring to the characteristics of the nuclear magnetic resonance T2 spectrum, the effective porosity T2 cutoff value for each lithology is calculated using an inversion iterative method.

[0074] Based on the NMR spectral characteristics of different lithologies and combined with the experimental helium porosity, the effective pore T2 cutoff value for different lithologies is obtained by inversion and iteration using equation (1). Finally, the effective pore T2 cutoff value is determined according to the root mean square error equation (2). The effective T2 cutoff value for the corresponding NMR spectrum of the lithology is less than 2.5.

[0075]

[0076]

[0077] In the formula, T 2cutoff The effective aperture T2 cutoff value for nuclear magnetic resonance (NMR) is given in milliseconds (ms). 2max φ is the maximum relaxation time of nuclear magnetic resonance (NMR), in milliseconds (ms). k Porosity calculated for different T2 cutoff values, in decimals; φ is the effective porosity, in decimals. XI is the actual value. is the predicted value, and n is the number of samples.

[0078] Figure 2The graph shows the results of the inversion iteration for the effective porosity T2 cutoff value. The blue line represents sandstone and conglomerate, with the effective porosity T2 cutoff value determined by the inversion iteration ranging from 11.2 to 14.1 ms; the red line represents tuffaceous sandstone and conglomerate, with the effective porosity T2 cutoff value determined by the inversion iteration ranging from 16.5 to 19 ms; the green line represents gravelly sandstone, with the effective porosity T2 cutoff value determined by the inversion iteration ranging from 4.1 to 6.7 ms; and the purple line represents calcareous sandstone and conglomerate, with the effective porosity T2 cutoff value determined by the inversion iteration ranging from 21 to 24.3 ms.

[0079] Step 3: Analyze the main controlling factors of the effective porosity T2 cutoff value from nuclear magnetic resonance (NMR) and establish calculation models for the effective porosity T2 cutoff value based on lithology. By analyzing relevant rock physics experimental parameters and well logging curve parameters, the key controlling parameters are selected as average capillary radius, sorting coefficient, displacement pressure, clay content, and clay type. For example... Figure 3 The graph shows the correlation coefficients between reservoir parameters and the effective pore size T2 cutoff value, where the clay content is 0.6%, the average capillary radius is 0.51, the sorting coefficient is 0.52, and the displacement pressure is 0.65.

[0080] Based on the key control parameters, a comprehensive pore structure index is constructed using equation (3), a comprehensive logging pore structure index is constructed using equation (4), and finally, a nuclear magnetic resonance effective pore T2 cutoff value calculation model is established based on lithology using equation (5).

[0081]

[0082]

[0083] T 2变 =e·PZ 测井 +f·TS-g·v cl d (5)

[0084] In the formula, SP is the sorting coefficient, in decimal place; RC is the average capillary radius, in μm; Pd is the discharge pressure, in MPa; V cl Clay content, in % (%), calculated using regional empirical formulas; TS, rock particle sorting coefficient, calculated using electro-imaging, decimal; d, clay type coefficient, ranging from 1 to 2.

[0085] The well logging PZ calculation model established by equation (4) is as follows:

[0086]

[0087] The four lithological nuclear magnetic resonance effective porosity T2 cutoff values ​​calculation models established by equation (5) are as follows:

[0088] 1) Sandstone and conglomerate: T 21 = 1.524 × PZ + 3.421 × TS - 0.354 × V cl 1.5

[0089] 2) Tuffaceous sandstone and conglomerate: T 22 = 1.750 × PZ + 3.691 × TS - 0.366 × V cl 1.5

[0090] 3) Gravelly-bearing sandstone: T 23 = 1.452 × PZ + 3.190 × TS - 0.434 × V cl 1.5

[0091] 4) Calcareous sandstone and conglomerate: T 24 = 1.769 × PZ + 3.694 × TS - 0.341 × V cl 1.5

[0092] Step 4: Calculate the reservoir's variable T2 cutoff value using the nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and then accurately calculate the reservoir's effective porosity using the nuclear magnetic resonance porosity calculation formula.

[0093]

[0094] In the formula, T 2cutoff T2 cutoff value for effective aperture in nuclear magnetic resonance imaging, in milliseconds (ms). 2max φ is the maximum relaxation time of nuclear magnetic resonance (NMR), in milliseconds (ms). k Porosity calculated for different T2 cutoff values, in decimal units; φ is the effective porosity, in decimal units.

[0095] like Figure 4 The figure shows the results of calculating effective porosity with varying T2 cutoff values. In the figure, channel 3 represents the core lithology profile, channel 4 represents the calculated lithology profile from well logging, channels 5-8 represent conventional well logging curves and well gas logging curves, channel 9 represents the nuclear magnetic resonance T2 spectrum, channel 10 compares the effective porosity calculated with varying T2 cutoff values ​​with the core porosity, and channel 11 compares the effective porosity calculated with a fixed T2 cutoff value with the core porosity. As can be seen from the figure, the comparison between the effective porosity calculated with varying T2 cutoff values ​​and the core porosity is more accurate, thus verifying the reliability of the method of this invention.

[0096] The present invention also discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the effective pore size calculation method for the variable T2 cutoff value of subdivided lithology described above.

[0097] The present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for calculating the effective pore size of the variable T2 cutoff value for subdivided lithology as described above.

[0098] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0099] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0100] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0101] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating effective porosity of varying T2 cutoff values ​​in subdivided lithology, characterized in that, Includes the following steps: Based on lithological classification, the T2 spectral characteristics of nuclear magnetic resonance for different lithologies were extracted; Based on the helium porosity of different lithologies, and by comparing the characteristics of nuclear magnetic resonance T2 spectra, the effective porosity T2 cutoff value for each lithology was calculated using an inversion iterative method. Based on the main controlling factors of the effective pore T2 cutoff value of nuclear magnetic resonance (NMR), a calculation model for the effective pore T2 cutoff value of NMR is established according to lithology. The main controlling factors of the effective pore T2 cutoff value of NMR include average capillary radius, sorting coefficient, displacement pressure, clay content, and clay type. Based on the main controlling factors of the effective pore T2 cutoff value of NMR, a comprehensive pore structure index is constructed through equation (3), a comprehensive logging pore structure index is constructed through equation (4), and finally, a calculation model for the effective pore T2 cutoff value of NMR is established according to lithology through equation (5). （3） （4） = （5） In the formula, SP This is the sorting coefficient; RC The average capillary radius; Pd To relieve driving pressure; This is an empirical coefficient; Calculate porosity for density; These are neutron logging values; These are formation resistivity logging values; This is an empirical coefficient; This is an empirical coefficient; This is an empirical coefficient; This is an empirical coefficient; For sorting rock particles; This is an empirical coefficient; V cl Clay content; d For clay type coefficient; This represents the T2 cutoff value for reservoir variation; The T2 cutoff value of the reservoir is calculated using a nuclear magnetic resonance (NMR) effective porosity T2 cutoff value calculation model. Combined with the NMR porosity calculation formula, the effective porosity of the reservoir is then calculated.

2. The method for calculating effective porosity of variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that, Based on nuclear magnetic resonance logging data, the characteristics of effective porosity T2 cutoff values ​​of nuclear magnetic resonance T2 spectra for different lithologies were statistically analyzed.

3. The method for calculating effective porosity of variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that, Based on the NMR spectral characteristics of different lithologies, and by comparing them with the T2 spectral characteristics of NMR, the effective pore T2 cutoff value for different lithologies is obtained through inversion and iteration using equation (1). Finally, the effective pore T2 cutoff value is determined according to the root mean square error equation (2). （1） （2） In the formula, The effective aperture T2 cutoff value for nuclear magnetic resonance (NMR) is given. This is the maximum relaxation time of nuclear magnetic resonance (NMR). Porosity calculated for different T2 cutoff values; Effective porosity; XI This is the actual value. For predicted values, n This represents the number of samples.

4. The method for calculating effective porosity of variable T2 cutoff value for subdivided lithology according to claim 3, characterized in that, The effective T2 cutoff value is determined according to the root mean square error formula (2). If the root mean square error is less than 2.5, it is the effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology.

5. The method for calculating effective porosity of variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that, The reservoir's variable T2 cutoff value is calculated using a nuclear magnetic resonance (NMR) effective porosity T2 cutoff value calculation model. Combined with the NMR porosity calculation formula, the reservoir's effective porosity is then calculated. （6） In the formula, This is the maximum relaxation time of nuclear magnetic resonance (NMR). This represents the T2 cutoff value for reservoir variation; Porosity calculated for different T2 cutoff values; Effective porosity.

6. A system for calculating effective porosity with varying T2 cutoff values ​​for subdivided lithology, characterized in that, The method for calculating the effective porosity of the variable T2 cutoff value for subdivided lithology as described in any one of claims 1 to 5 includes: The extraction unit is used to extract the T2 spectral characteristics of different lithologies based on lithological classification; The first calculation unit is used to calculate the effective porosity T2 cutoff value for each type of lithology based on the helium porosity of different lithologies and the characteristics of nuclear magnetic resonance T2 spectra, by means of an inversion iterative method. The model building unit is used to determine and establish a calculation model for the effective porosity T2 cutoff value of nuclear magnetic resonance based on the main controlling factors of the effective porosity T2 cutoff value of nuclear magnetic resonance according to lithology. The second calculation unit is used to calculate the reservoir's variable T2 cutoff value using the nuclear magnetic resonance effective porosity T2 cutoff value calculation model, and to calculate the reservoir's effective porosity using the nuclear magnetic resonance porosity calculation formula.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for calculating the effective porosity of the variable T2 cutoff value of subdivided lithology as described in any one of claims 1-5.

8. A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for calculating the effective porosity of the variable T2 cutoff value for subdivided lithology as described in any one of claims 1-5.

Images