CN-121994854-A - Nuclear magnetic resonance T based on least square method and mercury-pressing data2Spectral aperture conversion method

CN121994854ACN 121994854 ACN121994854 ACN 121994854ACN-121994854-A

Abstract

The invention belongs to the technical field of reservoir pore structure characterization, and relates to a nuclear magnetic resonance T 2 spectrum pore diameter conversion method based on least square method and mercury intrusion data. The method comprises the steps of interpolating and fitting the cumulative distribution frequency of nuclear magnetic resonance about relaxation time to obtain the relation between the cumulative distribution frequency of relaxation time and mercury-pressing pore radius, interpolating and fitting the cumulative distribution frequency of high-pressure mercury about pore radius to obtain the relation between the cumulative distribution frequency of pore radius and mercury-pressing pore radius, establishing an error function based on the relation between the cumulative distribution frequency of relaxation time and mercury-pressing pore radius and the relation between the cumulative distribution frequency of pore radius and mercury-pressing pore radius, establishing a conversion function for converting the cumulative distribution curve of nuclear magnetic resonance T 2 relaxation time into the cumulative distribution curve of high-pressure mercury-pressing pore throat radius, substituting the error function into the conversion function to obtain the conversion coefficient in the conversion function, and completing nuclear magnetic resonance T 2 spectrum pore diameter conversion.

Inventors

HE YUANYUAN
ZHANG YONGLING
TANG YANGANG
SONG ZEZHANG
LIANG XIAO
JIANG FUJIE
NIE HAIFENG
WEI PENG

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260508
Application Date: 20241107

Claims (10)

1. The nuclear magnetic resonance T 2 spectral aperture conversion method based on the least square method and mercury intrusion data is characterized by comprising the following steps of: acquiring high-pressure mercury experimental data and nuclear magnetic resonance experimental data of a plurality of samples, drawing a cumulative distribution curve of nuclear magnetic resonance T 2 relaxation time to obtain cumulative distribution frequency of nuclear magnetic resonance about the relaxation time; Interpolation and fitting are carried out on the cumulative distribution frequency of the nuclear magnetic resonance about the relaxation time to obtain the relationship between the cumulative distribution frequency of the relaxation time and the mercury-pressing pore radius; Based on the relation between the cumulative distribution frequency of the relaxation time and the mercury-pressing pore radius and the relation between the cumulative distribution frequency of the pore radius and the mercury-pressing pore radius, establishing an error function according to a least square method; Establishing a conversion function for converting the cumulative distribution curve of the nuclear magnetic resonance T 2 relaxation time into the cumulative distribution curve of the high-pressure mercury pore throat radius; substituting the error function into a conversion function to obtain a conversion coefficient in the conversion function, and finishing nuclear magnetic resonance T 2 spectral aperture conversion.
2. The nuclear magnetic resonance T 2 spectral aperture conversion method based on the least square method and mercury-pressing data according to claim 1, wherein when the cumulative distribution curve of the high-pressure mercury pore throat radius is drawn, the mercury saturation in the high-pressure mercury experimental data is selected to be smaller than the maximum mercury inlet saturation and larger than the mercury saturation corresponding to the displacement pressure.
3. The method of nuclear magnetic resonance T 2 spectral aperture transformation based on least squares and mercury intrusion data according to claim 1, wherein the interpolation and fitting uses gaussian peak-to-peak fitting.
4. The method for transforming nuclear magnetic resonance T 2 spectrum aperture based on least square method and mercury intrusion data according to claim 1, wherein the relation between the cumulative distribution frequency and mercury intrusion aperture radius based on the relaxation time and the relation between the cumulative distribution frequency and mercury intrusion aperture radius based on the aperture radius are specifically: Wherein S (LgT 2 ) represents the relation between the cumulative distribution frequency of the relaxation time and the mercury intrusion aperture radius, S (Lgr) represents the relation between the cumulative distribution frequency of the aperture radius and the mercury intrusion aperture radius, r max represents the maximum pore throat radius, and r min represents the minimum pore throat radius.
5. The method for transforming nuclear magnetic resonance T 2 spectral aperture based on least square method and mercury intrusion data according to claim 4, wherein the transformation function for creating the cumulative distribution curve of relaxation time of nuclear magnetic resonance T 2 into the cumulative distribution curve of throat radius of high-pressure mercury intrusion is specifically: Wherein C represents a conversion coefficient, ρ 2 represents a transverse surface relaxation intensity, μm/ms, F s represents a pore shape factor, T 2 represents a transverse relaxation time, n represents a power function, and r represents a pore throat radius.
6. The method for transforming nuclear magnetic resonance T 2 spectral aperture based on least square method and mercury intrusion data according to claim 5, wherein the error function is solved to obtain: Taking the logarithm of the two sides of the formula (3) to obtain: Substituting formula (4) into formula (1) to obtain:
7. The method for transforming the nuclear magnetic resonance T 2 spectral aperture based on the least square method and the mercury intrusion data according to claim 1, wherein substituting the error function into the conversion function to calculate the conversion coefficient in the conversion function specifically includes: setting values of different conversion coefficients C and power functions n, substituting the values into an error function T, drawing images of the error function T, the conversion coefficients C and the power functions n in a three-dimensional coordinate system, and obtaining the values of the conversion coefficients C and the power functions n as required final conversion coefficients when the error function T obtains the minimum value.
8. A nuclear magnetic resonance T 2 spectral aperture conversion system based on least square method and mercury intrusion data, comprising: The data acquisition module acquires high-pressure mercury experimental data and nuclear magnetic resonance experimental data of a plurality of samples, and draws a cumulative distribution curve of nuclear magnetic resonance T 2 relaxation time to obtain cumulative distribution frequency of nuclear magnetic resonance about the relaxation time; the interpolation fitting module is used for interpolating and fitting the cumulative distribution frequency of the nuclear magnetic resonance about the relaxation time to obtain the relationship between the cumulative distribution frequency of the relaxation time and the mercury-filled pore radius; The error function establishing module is used for establishing an error function based on the relation between the cumulative distribution frequency of the relaxation time and the mercury-pressing pore radius and the relation between the cumulative distribution frequency of the pore radius and the mercury-pressing pore radius; The conversion function establishing module is used for establishing a conversion function for converting the cumulative distribution curve of the nuclear magnetic resonance T 2 relaxation time into the cumulative distribution curve of the throat radius of the high-pressure mercury-filled hole; And the conversion coefficient obtaining module substitutes the error function into the conversion function to obtain the conversion coefficient in the conversion function, so as to complete nuclear magnetic resonance T 2 spectral aperture conversion.
9. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the method of nuclear magnetic resonance T 2 spectral aperture conversion based on least squares and mercury intrusion data according to any one of claims 1 to 7 when the computer program is executed.
10. A computer readable storage medium storing a computer program which, when executed by a processor, implements the steps of the method for nuclear magnetic resonance T 2 spectral aperture conversion based on least squares and mercury intrusion data of any one of claims 1-7.

Description

Nuclear magnetic resonance T 2 spectrum aperture conversion method based on least square method and mercury-pressing data Technical Field The invention belongs to the technical field of reservoir pore structure characterization, and relates to a nuclear magnetic resonance T 2 spectrum pore diameter conversion method based on least square method and mercury intrusion data. Background Dense gas is a major type of unconventional natural gas and has important significance and function in the natural gas resource structure. In the deep-ultra-deep layer, the clear pore size distribution of the compact sandstone is important to the exploration of oil and gas resources and the evaluation of the amount of the recoverable resources of the compact reservoir. Dense sandstone gas is becoming more and more important in recent years as an important component of world oil and gas resources that cannot be ignored. With the development of tight sandstone reservoir studies, more and more methods have been proposed for better characterization. In the experimental method of high-pressure mercury-pressing, mercury preferentially enters the pore space with the largest size, and gradually enters the smaller throat along with the increase of pressure, so that the mercury-pressing method has the biggest defect that mercury-pressing cannot reflect the pore information communicated with the pores corresponding to the pressure smaller than the maximum mercury-feeding pressure as one of the pore structure characterization methods. The physical basis of the nuclear magnetic resonance technology is to detect the related information of the rock pore structure and the pore fluid by measuring the nuclear magnetic resonance relaxation signal amplitude and the relaxation rate of hydrogen nuclei in the rock pore fluid by utilizing the self-generated magnetism of the hydrogen nuclei and the interaction of an external magnetic field of the hydrogen nuclei, and the related information can reflect the information of all pore throats in the rock core. The relaxation time of the nmr experiment is thus converted to a pore radius that better reflects the pore structure of the tight reservoir. In general, when the pore fluid is a single-phase wetting phase fluid, the relaxation of the fluid itself in the pores of the porous medium is much weaker than the relaxation of the surface of the medium and is negligible. At the same time, under ideal uniform magnetic field conditions, the influence of diffusion on nuclear magnetic measurement can be neglected. Thus, in a uniform magnetic field, the transverse relaxation time within a single pore channel of saturated water can be approximated as: Wherein T 2surface represents the surface relaxation time, ms, ρ 2 represents the transverse surface relaxation intensity, μm/ms, and S/V represents the specific surface area of the individual pores, μm 2/μm3. As can be obtained from formula (1.1), T 2 is related to the specific surface of the porous medium. For pore structures simplified into spheres and columns, the relationship between the specific surface and the pore diameter is as follows: Wherein F s is a pore shape factor, the spherical pore is 3, and the columnar pore is 2. The simultaneous type (1.1), (2.2) can be obtained: However, under practical formation conditions, natural pores are not of standard spherical or columnar morphology. The former performs a series of statistical analyses to find that the T 2 distribution and the pore radius more accord with a power function relation. Where n is a power function. The prior equipment and research method can not directly utilize the formula to convert the nuclear magnetic resonance T 2 distribution into a pore size distribution curve. Disclosure of Invention The invention aims to solve the technical problem that the distribution of nuclear magnetic resonance T 2 cannot be directly converted into a pore diameter distribution curve in the prior art, and provides a nuclear magnetic resonance T 2 spectrum pore diameter conversion method based on a least square method and mercury intrusion data. In order to achieve the above purpose, the invention is realized by adopting the following technical scheme: In a first aspect, the invention provides a nuclear magnetic resonance T 2 spectral aperture conversion method based on least square method and mercury intrusion data, comprising the following steps: acquiring high-pressure mercury experimental data and nuclear magnetic resonance experimental data of a plurality of samples, drawing a cumulative distribution curve of nuclear magnetic resonance T 2 relaxation time to obtain cumulative distribution frequency of nuclear magnetic resonance about the relaxation time; Interpolation and fitting are carried out on the cumulative distribution frequency of the nuclear magnetic resonance about the relaxation time to obtain the relationship between the cumulative distribution frequency of the relaxation time and the mercury-pressing