Method and system for calculating effective hole of subdivided lithologic variation T2 cut-off value, and electronic equipment

Abstract

The invention discloses a subdivided lithologic variable T2 cutoff value effective hole calculation method and system and electronic equipment, and belongs to the technical field of complex lithologic oil and gas reservoir well logging evaluation. Based on a glutenite reservoir of nuclear magnetic resonance well logging information, on the basis of accurate division of lithology, influence factors of rock components and pore structures are comprehensively considered, and the effective holes of the lithologic variable T2 cutoff value are calculated; according to the method, effective porosity calculation models of different nuclear magnetic T2 cutoff values are established according to lithology, a method of fitting a formula according to lithology is adopted, a large amount of nuclear magnetic experiment calibration is not needed, and effective porosity calculation of complex lithology can be realized by utilizing conventional logging, nuclear magnetic resonance T2 spectrum data and experimental pore structure data; compared with a method for calculating the effective porosity through a fixed T2 cut-off value, the method has the advantages that the calculation precision of the effective porosity of the reservoir is greatly improved, key parameters can be provided for reservoir physical property evaluation and saturation calculation, convenience and rapidness are achieved, rapid large-scale application in production is facilitated, and good universality and popularization value are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of well logging evaluation of complex lithology oil and gas reservoirs, and specifically relates to a method, system and electronic equipment for calculating effective holes with T2 cutoff values ​​of subdivided lithology. Background Art

[0002] As a logging method that can directly provide information on reservoir pore size and its distribution, nuclear magnetic resonance logging plays an increasingly important role in the exploration and development of oil and gas reservoirs. By processing and interpreting the nuclear magnetic resonance T2 spectrum, parameters such as total reservoir porosity, effective porosity, irreducible water saturation, movable oil saturation and permeability can be obtained. Among them, the size of the T2 cutoff is the key to affecting these parameters of nuclear magnetic resonance. Studies have found that the distribution of T2 spectra is not only closely related to the size and distribution of rock pores, but also closely related to lithology, measurement parameters and clay content. Complex lithology reservoirs have different internal sedimentary characteristics and structures, resulting in complex and diverse reservoir lithology and pore structure. Calculating effective porosity by fixing the T2 cutoff value cannot accurately characterize rock pores. Summary of the invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method, system and electronic equipment for calculating effective pores with variable T2 cutoff value of subdivided lithology, so as to solve the technical problem that the effective porosity calculated with fixed T2 cutoff value in the prior art cannot accurately characterize the rock pores.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for calculating effective pores with variable T2 cutoff values ​​for subdividing lithology comprises the following steps:

[0006] Based on the lithology classification, the NMR T2 spectrum characteristics of different lithologies are extracted;

[0007] According to the experimental helium porosity of different lithologies and the characteristics of nuclear magnetic resonance T2 spectrum, the effective pore T2 cutoff value of each lithology was calculated by inversion iteration method;

[0008] Determine and establish a calculation model for the effective pore T2 cutoff value of NMR based on the main controlling factors of the effective pore T2 cutoff value of NMR according to lithology;

[0009] The reservoir variable T2 cutoff value is calculated through the NMR effective pore T2 cutoff value calculation model, and the reservoir effective porosity is calculated by combining the NMR porosity calculation formula.

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

[0011] Preferably, according to the nuclear magnetic resonance spectrum characteristics of different lithologies, compared with the nuclear magnetic resonance T2 spectrum characteristics, the effective hole T2 cutoff values ​​of different lithologies are inverted and iterated by formula (1), and finally the effective hole T2 cutoff value is determined according to the root mean square error formula (2):

[0012]

[0013]

[0014] Where, T 2cutoff is the effective hole T2 cutoff value of NMR; T 2max is the maximum relaxation time of NMR; φ k is the 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 hole T2 cutoff value is determined according to the root mean square error formula (2), and the root mean square error less than 2.5 is the effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology.

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

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

[0018]

[0019]

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

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

[0022] Preferably, the reservoir variable T2 cutoff value is calculated by using a nuclear magnetic resonance effective pore T2 cutoff value calculation model, and the reservoir effective porosity is calculated in combination with a nuclear magnetic resonance porosity calculation formula.

[0023]

[0024] Where, T 2max T is the maximum relaxation time of NMR; 2变 is the reservoir variable T2 cutoff value; φ k is the porosity calculated for different T2 cutoff values; φ is the effective porosity.

[0025] The present invention also discloses a system for calculating effective holes with variable T2 cutoff values ​​for subdividing lithology, comprising:

[0026] An extraction unit is used to extract the nuclear magnetic resonance T2 spectrum characteristics of different lithologies based on lithology classification;

[0027] The first calculation unit is used to calculate the effective pore T2 cutoff value of each lithology through an inversion iteration method according to the experimental helium porosity of different lithologies and the nuclear magnetic resonance T2 spectrum characteristics;

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

[0029] The second calculation unit is used to calculate the reservoir variable T2 cutoff value through the nuclear magnetic resonance effective pore T2 cutoff value calculation model, and calculate the reservoir effective porosity in combination with the nuclear magnetic resonance porosity calculation formula.

[0030] The present invention also discloses an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for calculating effective holes with variable T2 cutoff values ​​for subdivided lithology described in any one of the above items are implemented.

[0031] The present invention also discloses a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the method for calculating effective holes with variable T2 cutoff values ​​for subdivided lithology described in any one of the above items are implemented.

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

[0033] A method for calculating effective porosity with variable T2 cutoff values ​​for subdivided lithology is provided for sandstone conglomerate reservoirs based on nuclear magnetic resonance logging data. On the basis of accurate division of lithology, the method comprehensively considers the influencing factors of rock composition and pore structure, establishes effective porosity calculation models with different nuclear magnetic resonance T2 cutoff values ​​for different lithology, and calculates effective porosity for sandstone conglomerate reservoirs in oilfield exploration and development. The effective porosity calculation method with variable T2 cutoff values ​​for complex lithology reservoirs based on nuclear magnetic resonance logging data mentioned in the present invention has a rigorous theoretical basis and a clear physical meaning of the formula. In practical applications, the method of fitting formula for different lithology is adopted, and there is no need to rely on a large number of nuclear magnetic resonance experimental calibrations. Conventional logging, nuclear magnetic resonance T2 spectrum data and experimental pore structure data can be used to realize effective porosity calculation of complex lithology. Compared with the calculation of effective porosity with a fixed T2 cutoff value, the present invention greatly improves the calculation accuracy of effective porosity of reservoirs, can provide key parameters for reservoir physical property evaluation and saturation calculation, is convenient and fast, is conducive to rapid large-scale application in production, and has good universality and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of a method for calculating effective holes with variable T2 cutoff values ​​for subdividing lithology according to the present invention;

[0035] Figure 2 This is the inversion iteration result diagram of the effective porosity T2 cutoff value of the present invention;

[0036] Figure 3 is a correlation coefficient diagram of the reservoir parameters and the effective pore T2 cutoff value of the present invention;

[0037] Figure 4 This is a graph showing the calculation results of effective porosity with a variable T2 cutoff value according to the present invention;

[0038] Figure 5 It is a schematic diagram of an effective hole calculation system with a variable T2 cutoff value for subdividing lithology according to the present invention. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only 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 creative work 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 and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0042] Complex lithology reservoirs have different internal sedimentary characteristics and structures, resulting in complex and diverse reservoir lithology and pore structure. Calculating effective porosity by fixing the T2 cutoff value cannot accurately characterize rock pores. The present invention provides a method for calculating effective porosity with a variable T2 cutoff value for complex lithology reservoirs based on nuclear magnetic resonance logging data. By analyzing the main controlling factors of the nuclear magnetic resonance T2 cutoff value, a T2 cutoff value calculation formula is established for each lithology. In combination with the nuclear magnetic resonance porosity calculation formula, an effective porosity calculation method with a variable T2 cutoff value is constructed, thereby realizing continuous and accurate calculation of effective porosity in the vertical direction. This method can quickly and accurately calculate the effective porosity of the reservoir without nuclear magnetic resonance experiments in the early stage, and provide technical support for the detailed interpretation and evaluation of logging reservoir parameters.

[0043] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0044] See also Figure 1 , a method for calculating effective pores with variable T2 cutoff values ​​for subdivided lithology, characterized in that it comprises the following steps:

[0045] S1: Based on the lithology classification, the NMR T2 spectrum characteristics of different lithologies are extracted;

[0046] S2: Based on the experimental helium porosity of different lithologies and the characteristics of nuclear magnetic resonance T2 spectra, the effective pore T2 cutoff value of each lithology is calculated through the inversion iteration method;

[0047] S3: Determine and establish a calculation model for the effective pore T2 cutoff value of NMR according to the main controlling factors of the effective pore T2 cutoff value of NMR according to lithology;

[0048] S4: Calculate the reservoir variable T2 cutoff value through the NMR effective pore T2 cutoff value calculation model, and calculate the reservoir effective porosity by combining the NMR porosity calculation formula.

[0049] The present invention is based on the sandstone reservoir of nuclear magnetic resonance logging data. On the basis of accurate division of lithology, the method comprehensively considers the influencing factors of rock composition and pore structure, establishes effective porosity calculation models with different nuclear magnetic resonance T2 cutoff values ​​for different lithology, and calculates the effective porosity of the sandstone reservoir in oil field exploration and development. The effective porosity calculation method of complex lithology reservoir with variable T2 cutoff value based on nuclear magnetic resonance logging data mentioned in the present invention has a rigorous theoretical basis and a clear physical meaning of the formula. In practical applications, the method of fitting formula for different lithology is adopted, and there is no need to rely on a large number of nuclear magnetic experiment calibrations. Conventional logging, nuclear magnetic resonance T2 spectrum data and experimental pore structure data can be used to realize the effective porosity calculation of complex lithology. Compared with the calculation of effective porosity with a fixed T2 cutoff value, the present invention greatly improves the calculation accuracy of reservoir effective porosity, can provide key parameters for reservoir physical property evaluation and saturation calculation, is convenient and fast, is conducive to rapid large-scale application in production, and has good universality and promotion value.

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

[0051] In some embodiments, in S2, according to the nuclear magnetic resonance spectrum characteristics of different lithologies, compared with the nuclear magnetic resonance T2 spectrum characteristics, the effective hole T2 cutoff values ​​of different lithologies are inverted and iterated by formula (1), and finally the effective hole T2 cutoff value is determined according to the root mean square error formula (2):

[0052]

[0053]

[0054] Where, T 2cutoff is the effective hole T2 cutoff value of NMR; T 2max is the maximum relaxation time of NMR; φ k is the 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] Further preferably, the effective hole T2 cutoff value is determined according to the root mean square error formula (2), and the root mean square error less than 2.5 is the effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology.

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

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

[0058]

[0059]

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

[0061] Where, SP is the sorting coefficient; RC is the average capillary radius; Pd is the displacement pressure; a is the empirical coefficient; φ D is the porosity calculated from density; CNL is the neutron logging value, unit %; RT is the formation resistivity logging value, unit ohm.m; b is the empirical coefficient; c is the empirical coefficient; e is the empirical coefficient; f is the empirical coefficient; TS is the rock particle sorting, unit decimal, calculated from electrical imaging data; g is the empirical coefficient; V cl is the clay content; TS is the rock particle sorting, unit decimal, calculated from electrical imaging data; d is the clay type coefficient; T 2变 is the T2 cutoff value for the reservoir.

[0062] In some embodiments, the reservoir variable T2 cutoff value is calculated by using a nuclear magnetic resonance effective pore T2 cutoff value calculation model, and the reservoir effective porosity is calculated in combination with a nuclear magnetic resonance porosity calculation formula.

[0063]

[0064] Where, T 2cutoff is the effective aperture T2 cutoff value of NMR, in ms, T 2max is the maximum relaxation time of NMR, in ms; φ k is the porosity calculated for different T2 cutoff values, in decimals; φ is the effective porosity, in decimals.

[0065] See also Figure 5 The present invention also discloses a variable T2 cutoff value effective hole calculation system for subdividing lithology, comprising:

[0066] An extraction unit is used to extract the nuclear magnetic resonance T2 spectrum characteristics of different lithologies based on lithology classification;

[0067] The first calculation unit is used to calculate the effective pore T2 cutoff value of each lithology through an inversion iteration method according to the experimental helium porosity of different lithologies and the nuclear magnetic resonance T2 spectrum characteristics;

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

[0069] The second calculation unit is used to calculate the reservoir variable T2 cutoff value through the nuclear magnetic resonance effective pore T2 cutoff value calculation model, and calculate the reservoir effective porosity in combination with the nuclear magnetic resonance porosity calculation formula.

[0070] [Example]

[0071] See also Figure 1 The embodiment of the present invention provides a method for calculating effective holes with variable T2 cutoff values ​​for subdividing lithology, comprising the following steps:

[0072] Step 1: Based on the lithology classification, extract the characteristics of the nuclear magnetic resonance T2 spectra of different lithologies. According to the lithology classification results of the study area, the lithologies are divided into four categories: limy conglomerate, tuffaceous conglomerate, conglomerate, and gravelly sandstone. According to the nuclear magnetic resonance logging data, the effective porosity T2 cutoff value characteristics of the nuclear magnetic resonance T2 spectra of different lithologies are statistically analyzed.

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

[0074] According to the characteristics of nuclear magnetic resonance spectra of different lithologies and combined with the experimental helium porosity, the effective pore T2 cutoff values ​​of different lithologies are inverted and iterated by formula (1). Finally, the effective pore T2 cutoff value is determined according to the root mean square error formula (2). The effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology is determined when the root mean square error is less than 2.5:

[0075]

[0076]

[0077] Where, T 2cutoff is the effective aperture T2 cutoff value of NMR, ms, T 2max is the maximum relaxation time of NMR, in ms; φ k is the 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 2This is the inversion iteration result diagram of the effective porosity T2 cutoff value. The blue broken line in the figure is sandy conglomerate, and the effective porosity T2 cutoff value interval determined by inversion iteration is 11.2-14.1ms; the red broken line is tuffous sandy conglomerate, and the effective porosity T2 cutoff value interval determined by inversion iteration is 16.5-19ms; the green broken line is gravel-bearing sandstone, and the effective porosity T2 cutoff value interval determined by inversion iteration is 4.1-6.7ms; the purple broken line is gray sandy conglomerate, and the effective porosity T2 cutoff value interval determined by inversion iteration is 21-24.3ms.

[0079] Step 3: Analyze the main controlling factors of the effective pore T2 cutoff value of NMR, and establish the calculation model of the effective pore T2 cutoff value of NMR by lithology. By analyzing the control factors such as relevant rock physics experimental parameters and logging curve parameters, the key parameters of the main control are selected as the average capillary radius, sorting coefficient, displacement pressure, clay content, and clay type. Figure 3 Figure 2 is the correlation coefficient diagram between reservoir parameters and effective pore 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] According to the main control key parameters, the pore structure comprehensive index is constructed by formula (3), the well logging pore structure comprehensive index is constructed by formula (4), and finally the NMR effective pore T2 cutoff value calculation model is established according to lithology by formula (5).

[0081]

[0082]

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

[0084] Where, SP is the sorting coefficient, in decimal units; RC is the average capillary radius, in μm; Pd is the displacement pressure, in MPa; V cl is the clay content, unit: %, calculated by regional empirical formula; TS is the rock particle sorting coefficient, calculated by electrical imaging, a decimal; d is the clay type coefficient, ranging from 1 to 2.

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

[0086]

[0087] The four lithology NMR effective pore T2 cutoff value calculation models established by formula (5) are:

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

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

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

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

[0092] Step 4: Calculate the reservoir variable T2 cutoff value through the NMR effective pore T2 cutoff value calculation model, and accurately calculate the reservoir effective porosity by combining the NMR porosity calculation formula.

[0093]

[0094] Where, T 2cutoff is the effective aperture T2 cutoff value of NMR, in ms, T 2max is the maximum relaxation time of NMR, in ms; φ k is the porosity calculated for different T2 cutoff values, in decimals; φ is the effective porosity, in decimals.

[0095] like Figure 4 The figure is a result diagram of effective porosity calculation with variable T2 cutoff value. The third track in the figure is the core lithology profile, the fourth track is the lithology profile calculated by logging, tracks 5-8 are conventional logging curves and logging gas logging curves, track 9 is the nuclear magnetic resonance T2 spectrum, track 10 is the comparison between the effective porosity calculated with variable T2 cutoff value and the core porosity, and track 11 is the comparison between the effective porosity calculated with fixed T2 cutoff value and the core porosity. It can be seen from the figure that the comparison accuracy of the effective porosity calculated by the variable T2 cutoff value and the core porosity is higher, thereby verifying the reliability of the method of the present invention.

[0096] The present invention also discloses an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for calculating effective holes with variable T2 cutoff values ​​for subdivided lithology described in any one of the above items are implemented.

[0097] The present invention also discloses a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the method for calculating effective holes with variable T2 cutoff values ​​for subdivided lithology described in any one of the above items are implemented.

[0098] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented 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] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0100] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function 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 rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does 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 pores with variable T2 cutoff values ​​for subdivided lithology, characterized in that: The following steps are involved: Based on the lithology classification, the NMR T2 spectrum characteristics of different lithologies are extracted; According to the experimental helium porosity of different lithologies and the characteristics of nuclear magnetic resonance T2 spectrum, the effective pore T2 cutoff value of each lithology was calculated by inversion iteration method; Determine and establish a calculation model for the effective pore T2 cutoff value of NMR based on the main controlling factors of the effective pore T2 cutoff value of NMR according to lithology; The reservoir variable T2 cutoff value is calculated through the NMR effective pore T2 cutoff value calculation model, and the reservoir effective porosity is calculated by combining the NMR porosity calculation formula.

2. The method for calculating effective pores with variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that: According to the NMR logging data, the effective porosity T2 cutoff value characteristics of NMR T2 spectra of different lithologies were statistically analyzed.

3. The method for calculating effective pores with variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that: According to the NMR spectrum characteristics of different lithologies and the NMR T2 spectrum characteristics, the effective hole T2 cutoff values ​​of different lithologies are inverted and iterated by formula (1), and finally the effective hole T2 cutoff value is determined according to the root mean square error formula (2): Where, T 2cutoff is the effective hole T2 cutoff value of NMR; T 2max is the maximum relaxation time of NMR; φ k is the 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.

4. A method for calculating effective pores with variable T2 cutoff values ​​for subdivided lithology according to claim 3, characterized in that: The effective hole T2 cutoff value is determined according to the root mean square error formula (2), and the root mean square error less than 2.5 is the effective T2 cutoff value of the nuclear magnetic spectrum corresponding to the lithology.

5. The method for calculating effective pores with variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that: The main controlling factors include average capillary radius, sorting coefficient, displacement pressure, clay content and clay type.

6. The method for calculating effective pores with variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that: According to the main controlling factors of the effective pore T2 cutoff value of NMR, the comprehensive pore structure index is constructed by formula (3), the comprehensive pore structure index of well logging is constructed by formula (4), and finally the calculation model of the effective pore T2 cutoff value of NMR is established by lithology by formula (5): T 2变 =e·PZ 测井 +f·TS-g·V cl d (5) Where, SP is the sorting coefficient; RC is the average capillary radius; Pd is the displacement pressure; a is the empirical coefficient; φ D is the porosity calculated from density; CNL is the neutron logging value; RT is the formation resistivity logging value; b is the empirical coefficient; c is the empirical coefficient; e is the empirical coefficient; f is the empirical coefficient; TS is the rock particle sorting; g is the empirical coefficient; V cl is the clay content; TS is the rock particle sorting calculated by electrical imaging; d is the clay type coefficient; T 2变 is the T2 cutoff value for the reservoir.

7. The method for calculating effective pores with variable T2 cutoff value for subdivided lithology according to claim 1, characterized in that: The reservoir variable T2 cutoff value is calculated by the NMR effective pore T2 cutoff value calculation model, and the reservoir effective porosity is calculated by combining the NMR porosity calculation formula: Where, T 2max is the maximum relaxation time of NMR; T 2变 is the reservoir variable T2 cutoff value; φ k is the porosity calculated for different T2 cutoff values; φ is the effective porosity.

8. A variable T2 cutoff effective hole calculation system for subdividing lithology, characterized in that: include: An extraction unit is used to extract the nuclear magnetic resonance T2 spectrum characteristics of different lithologies based on lithology classification; The first calculation unit is used to calculate the effective pore T2 cutoff value of each lithology through an inversion iteration method according to the experimental helium porosity of different lithologies and the nuclear magnetic resonance T2 spectrum characteristics; The model building unit is used to determine and establish a calculation model for the effective pore T2 cutoff value of nuclear magnetic resonance according to the main controlling factors of the effective pore T2 cutoff value of nuclear magnetic resonance by lithology; The second calculation unit is used to calculate the reservoir variable T2 cutoff value through the nuclear magnetic resonance effective pore T2 cutoff value calculation model, and calculate the reservoir effective porosity in combination with the nuclear magnetic resonance porosity calculation formula.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for calculating effective pores with variable T2 cutoff values ​​for subdivided lithology as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the method for calculating effective pores with a variable T2 cutoff value for subdivided lithology according to any one of claims 1 to 7.

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