CN110231272B - Compact sandstone pore diameter and nuclear magnetic resonance T2Method and system for determining value conversion relation - Google Patents
Compact sandstone pore diameter and nuclear magnetic resonance T2Method and system for determining value conversion relation Download PDFInfo
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- CN110231272B CN110231272B CN201910616296.2A CN201910616296A CN110231272B CN 110231272 B CN110231272 B CN 110231272B CN 201910616296 A CN201910616296 A CN 201910616296A CN 110231272 B CN110231272 B CN 110231272B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
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Abstract
The embodiment of the invention discloses a compact sandstone pore diameter and nuclear magnetic resonance T2Value conversionA method and a system for determining a relationship relate to the technical field of geological evaluation of oil and gas reservoir reservoirs, and the method comprises the following steps: carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core; acquiring pore radius and volume data through the three-dimensional digital core, and further acquiring a digital core pore radius distribution map; carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram; based on digital core pore radius distribution diagram and nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values, fit rcAnd T2The relational expression (c) of (c). The embodiment of the invention realizes the tight sandstone pore radius and the nuclear magnetic resonance T2Quantitative calculation of value conversion relation, compared with the prior art which utilizes mercury intrusion pore throat distribution and nuclear magnetic resonance T2The obtained conversion relation of the spectrogram is more reliable, and the full-size pore structure of the compact sandstone reservoir is further accurately represented.
Description
Technical Field
The embodiment of the invention relates to the technical field of geological evaluation of oil and gas reservoir reservoirs, in particular to compact sandstonePore size and NMR T2A method and system for determining value conversion relationship.
Background
The tight sandstone gas is unconventional natural gas which has the highest yield and the most practical significance at present in China, the pore structure of the tight sandstone reservoir has the characteristics of fine pores and throats or fine pores and throats, the sizes of the pores and the throats determine the storage space and the seepage capacity of reservoir fluid, and the storage capacity and the recovery ratio are remarkably controlled, so that the identification of full-scale pore radius distribution has very important practical significance on the evaluation and development of tight sandstone gas reservoirs.
The conventional techniques for evaluating the pore structure mainly comprise the conventional high-pressure mercury intrusion technique, the constant-speed mercury intrusion technique, the CT scanning technique and the like, but the single techniques have defects in identifying the pore size. The high-pressure mercury injection technology can identify the size of a throat which plays a main control role in reservoir seepage and the volume size of a pore communicated with the throat, but cannot distinguish the radius size of the pore; the constant-speed mercury pressing technology can only reflect the characteristics of part of pores communicated with a relatively thick throat and cannot meet the requirement of developing fine pictures of the pores of the small-size throat; the resolution of the CT scanning technique in practical operation is limited, and the measurement resolution has a certain relationship with the size of the sample, for example, for a sample with a diameter of 6mm, the resolution that can be achieved by the CT technique at present is 2.9 μm, but the reduction of the size of the sample is not representative for a dense sandstone sample with strong heterogeneity, so the resolution of the CT scanning technique is obviously insufficient for dense sandstone with a very large proportion of fine pore throats.
The nuclear magnetic resonance technology has been widely used in the field of oil exploration and development, and according to the nuclear magnetic resonance principle, T2For fluids in a single pore, there are three relaxation mechanisms, the total transverse relaxation time T2And free relaxation (T)2B) Surface relaxation (T)2S) Diffusion relaxation (T)2D) Is represented by the formula (1):
since the diffusion relaxation in the uniform magnetic field is negligible and the free relaxation is mainly related to the physical properties of the saturated fluid, the first term and the third term on the right side in the formula (1) can simplify the processing, and the surface relaxation is mainly related to the mineral composition and the specific surface area of the rock sample, and the formula (1) can be simplified into the formula (2):
where ρ is2The rock surface relaxation rate is determined by rock surface properties and mineral composition, and S/V is the specific surface area of a single pore channel and is inversely proportional to the pore radius. Now that it is related to the pore radius, equation (2) can be further modified to equation (3):
wherein FsIs the shape factor of the pore, rcIs the pore radius, the final formula (3) can be transformed into the formula (4), C is T2Conversion to a conversion factor for the pore radius.
rc＝CT2(4)
As can be seen from the formula (4), the value of the pore radius conversion coefficient C or the pore radius and T can be obtained by any suitable method2Value conversion relation (actual rock pore structure is complex, pore diameter and T)2The relationship of (A) is not necessarily a simple linear relationship, and the conversion relation of the two can be expressed as rc＝C(T2) Can be T) to2And converting the spectrogram into a pore radius distribution diagram, thereby realizing the representation of the full-scale pore size distribution of the compact sandstone reservoir.
Nuclear magnetic resonance T for the same rock sample2The spectrogram and the high-pressure mercury pressing capillary pressure curve are the data representation of the pore development characteristics of the sample, and the prior art compares the nuclear magnetic resonance T2And calculating the conversion coefficient of the spectrogram and the high-pressure mercury pressing capillary pressure curve. By researching the principles of nuclear magnetic resonance and high-pressure mercury injection, the inventor finds that the pore throat information reflected by the nuclear magnetic resonance and the high-pressure mercury injection is largerThe difference is as follows: nuclear magnetic resonance T2The spectrogram can reflect the distribution of all pores, and the amplitude of the curve reflects the proportion of corresponding pores in the pore space; the high-pressure mercury intrusion can only reflect the distribution of the throats and the proportion of the corresponding throat communicated with the pore space, the amplitude of the curve reflects the proportion of the pore space communicated with the throat, and the larger pore size forming the pore space is not reflected, so the nuclear magnetic resonance T2The spectrogram and the pressure curve of the capillary have no comparative significance, and the nuclear magnetic resonance T is used2The pore radius conversion relation obtained by comparing the spectrogram with the mercury pressing capillary pressure curve is unreliable and is difficult to popularize and use.
Based on the above analysis, a tight sandstone pore diameter and nuclear magnetic resonance T are needed2The technical scheme of the method and the system for determining the value conversion relationship further obtains a more reliable conversion relationship to obtain the distribution data of the full-scale pore radius.
Disclosure of Invention
Therefore, the embodiment of the invention provides a compact sandstone pore diameter and nuclear magnetic resonance T2A method and a system for determining the value conversion relationship to solve the problems of the prior art due to the pore-throat distribution and nuclear magnetic resonance T2The reliability caused by the conversion relation obtained by comparing the spectrograms is not high.
In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:
according to the first aspect of the embodiment of the invention, the pore diameter and the nuclear magnetic resonance T of the tight sandstone2The method for determining the value conversion relation comprises the following steps:
carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core;
acquiring pore radius and pore volume data through the three-dimensional digital core, and acquiring a digital core pore radius distribution map based on the pore radius and pore volume data;
carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram;
based on the digital core pore radius distribution diagram and the nuclear magnetismVibrating T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values.
Further, the tight sandstone sample is a plunger sample with a diameter of 6mm and a length of 20 mm.
Further, the step of performing CT scanning on the obtained tight sandstone sample to obtain a three-dimensional digital core specifically includes:
scanning the compact sandstone sample by using a CT scanning device to obtain a CT value three-dimensional data volume of the compact sandstone sample;
and carrying out threshold processing on the CT value three-dimensional data volume through image processing software to obtain a three-dimensional digital core capable of distinguishing a pore space and a rock skeleton.
Further, the acquiring of the pore radius and pore volume data through the three-dimensional digital core specifically includes:
and identifying the pores and throats of the three-dimensional digital core to obtain the radius of all identifiable pores and the volume data of the pores.
Further, the abscissa of the digital core pore radius distribution diagram is the pore radius, and the ordinate is the porosity component.
Further, the saturated saline was a sodium chloride solution having a concentration of 40000 mg/L.
Further, the nuclear magnetic resonance measurement uses an echo interval less than or equal to 0.2 ms.
Further, the core pore radius distribution graph based on the number and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2The step of the relational expression of the values specifically includes:
accumulating the porosity component corresponding to each pore radius according to the pore radius from large to small based on the digital core pore radius distribution diagram to obtain a variation curve of the first accumulated porosity and the pore radius;
based on said nuclear magnetic resonance T2Spectrum according to nuclear magnetic resonance T2The value of T for each NMR is from large to small2The porosity component corresponding to the value is accumulated to obtain a second accumulated porosity and a nuclear magnetic resonance T2A change in value curve.
Further, the core pore radius distribution graph based on the number and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2The step of relating values, further comprising:
according to the principle of equal porosity, comparing the variation curve of the first cumulative porosity and the pore radius, and the second cumulative porosity and the nuclear magnetic resonance T2Curve of variation of value through pore radius r at the same porositycAnd nuclear magnetic resonance T2Value, establish pore radius rcAnd nuclear magnetic resonance T2A cross plot of values;
for the pore radius rcAnd nuclear magnetic resonance T2Fitting the intersection graph of the values by a formula to obtain the radius r of the porecAnd T2Conversion of values relation: r isc＝C(T2)。
According to a second aspect of the embodiment of the invention, the tight sandstone pore diameter and nuclear magnetic resonance T2A system for determining a value conversion relationship, comprising:
a scanning unit: the CT scanning device is used for carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core;
an acquisition unit: the digital core pore radius distribution diagram is obtained based on the pore radius and pore volume data;
a measurement unit: is used for carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram;
a fitting unit: for dividing the pore radius based on the digital corePatterning and said NMR T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values.
The embodiment of the invention has the following advantages: carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core; acquiring pore radius and pore volume data based on the three-dimensional digital core, and further acquiring a digital core pore radius distribution map; carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram; by comparing the digital core pore radius distribution diagram with the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values. The embodiment of the invention realizes the tight sandstone pore radius and the nuclear magnetic resonance T2Quantitative calculation of value conversion relation2The spectrogram is converted into a pore radius distribution diagram, compared with the prior art which utilizes mercury intrusion pore throat distribution and nuclear magnetic resonance T2The conversion relation obtained by comparison of the spectrograms is more reliable, and the full-size pore structure of the compact sandstone reservoir is further accurately represented, so that guidance is provided for evaluation and development practice of the compact sandstone gas reservoir.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.
FIG. 1 shows a tight sandstone pore size and NMR T provided in an embodiment of the present invention2A flow chart of a method of determining a value conversion relationship;
FIG. 2 is a sectional view of a CT value three-dimensional data volume of a tight sandstone sample according to an embodiment of the present invention;
FIG. 3 is a cross-sectional view of a three-dimensional digital core according to an embodiment of the invention;
FIG. 4 is a digital core pore radius distribution diagram in an embodiment of the present disclosure;
FIG. 5 shows the T obtained after the nuclear magnetic resonance measurement of saturated brine for the tight sandstone sample in the embodiment of the invention2A spectrogram;
FIG. 6 is a graph of cumulative porosity versus pore radius for an embodiment of the present invention;
FIG. 7 shows the cumulative porosity and NMR T in the example of the invention2A graph of the variation of the values;
FIG. 8 shows the pore radius r in an embodiment of the present inventioncAnd nuclear magnetic resonance T2A cross plot of values;
FIG. 9 shows a tight sandstone pore size and NMR T provided in an embodiment of the present invention2And the structure of the determination system of the value conversion relation is shown in the figure.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
FIG. 1 is a schematic diagram of an embodiment of the present inventionCompact sandstone pore diameter and nuclear magnetic resonance T2A flow chart of a method for determining a value transformation relationship, see fig. 1, comprising the steps of:
s1, carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core;
s2, acquiring pore radius and pore volume data through the three-dimensional digital core, and acquiring a digital core pore radius distribution map based on the pore radius and pore volume data;
s3, carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram;
s4, based on the digital core pore radius distribution diagram and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values.
In the embodiment, the compact sandstone sample source is a K gas reservoir of a compact sandstone gas field in a certain basin in the western China, and the K gas reservoir has the following characteristics: the buried depth is large (the depth is more than 6500m), the reservoir thickness is large (200 m-350 m), the effective thickness is generally more than 100m, the physical property of the reservoir is poor (the porosity is 3-7%, and the matrix permeability is less than 0.01mD), the rock type is feldspar quarry debris sandstone or rock debris feldspar sandstone, the lithology is mainly fine sandstone (the development of mud gravel at a local well section), and the microscopic characteristics of the reservoir are represented by the development of fine pore throats and the complex pore throat structure.
The embodiment of the invention provides a compact sandstone pore diameter and nuclear magnetic resonance T2The method for determining the value conversion relation comprises the steps of carrying out CT scanning on an obtained compact sandstone sample to obtain a three-dimensional digital core; acquiring pore radius and pore volume data based on the three-dimensional digital core, and further acquiring a digital core pore radius distribution map; carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram; by comparing the digital core pore radius distribution diagram with the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values. The embodiment of the invention realizes the tight sandstone pore radius and the nuclear magnetic resonance T2Quantitative calculation of value conversion relation2The spectrogram is converted into a pore radius distribution diagram, compared with the prior art which utilizes mercury intrusion pore throat distribution and nuclear magnetic resonance T2The conversion relation obtained by comparison of the spectrograms is more reliable, and the full-size pore structure of the compact sandstone reservoir is further accurately represented, so that guidance is provided for evaluation and development practice of the compact sandstone gas reservoir.
On the basis of the above embodiment of the present invention, the tight sandstone sample is a plunger sample with a diameter of 6mm and a length of 20 mm.
Specifically, in order to ensure that the sample is representative of the pore throat structure of the tight sandstone reservoir and to ensure proper CT scanning resolution, a tight sandstone plunger sample with the diameter of 6mm and the length of 20mm is drilled, oil washing, salt washing and drying pretreatment are carried out according to the oil industry specification after the sample is prepared, then the helium porosity of the sample is measured, and the helium porosity of the sample is measured to be 5.5%.
On the basis of any one of the embodiments of the present invention, the step of performing CT scanning on the obtained tight sandstone sample to obtain the three-dimensional digital core specifically includes:
scanning the compact sandstone sample by using a CT scanning device to obtain a CT value three-dimensional data volume of the compact sandstone sample;
and carrying out threshold processing on the CT value three-dimensional data volume through image processing software to obtain a three-dimensional digital core capable of distinguishing a pore space and a rock skeleton.
Specifically, a CT scanning device is used to perform CT scanning on the tight sandstone sample to obtain a CT value three-dimensional data volume of the sample, the resolution of the sample CT value three-dimensional data volume in this embodiment is 2.9 μm (that is, the voxel is 2.9 μm), the obtained CT number three-dimensional data volume is subjected to data processing by using existing CT image processing software (for example, Avizo Fire), and the CT value three-dimensional data volume is represented as a three-dimensional grayscale image in the software, see fig. 2. According to the principle that the pore space and the rock framework have obvious difference on the CT value, the existing CT image processing software is used for carrying out threshold processing on the CT value three-dimensional data body, a reasonable threshold is defined to distinguish the pore space and the rock framework, and the three-dimensional distribution data body of the pore space and the rock framework is obtained, namely the three-dimensional digital core, and the three-dimensional distribution data body is shown in figure 3.
On the basis of any one of the above embodiments of the present invention, the acquiring pore radius and pore volume data by using the three-dimensional digital core specifically includes:
and identifying the pores and throats of the three-dimensional digital core to obtain the radius of all identifiable pores and the volume data of the pores.
The abscissa of the digital core pore radius distribution diagram is the pore radius, and the ordinate is the porosity component.
Specifically, in the existing CT image processing software, the existing algorithm (for example, the maximum sphere method) is used to identify the pores and the throats of the three-dimensional digital core, and then the identified pore throats are subjected to quantitative analysis to obtain the radius of all identifiable pores and the volume data of the pores, so that a digital core pore radius distribution map can be further obtained; the abscissa of the digital core pore radius distribution diagram is the pore radius, and the ordinate is the porosity component, wherein the porosity component is the ratio of the pore volume to the compact sandstone sample volume.
It should be noted that the pore throat recognizable in this embodiment is not the entire pore throat in the sample, and since the CT resolution is 2.9 μm, the minimum pore radius that can be actually and accurately recognized in this embodiment is about 5 μm, see fig. 4.
On the basis of any one of the above embodiments of the present invention, the saturated saline is a sodium chloride solution with a concentration of 40000 mg/L; the echo interval used for the nuclear magnetic resonance measurement is less than or equal to 0.2 ms.
Specifically, in this embodiment, the same tight sandstone sample is subjected to brine (40000mg/L sodium chloride solution) saturation treatment, and further nuclear magnetic resonance measurement is performed on the sandstone sample of saturated brine according to the rock sample nuclear magnetic resonance measurement industry specification, so as to obtain T2Spectra. Wherein, the sample is compact sandstoneThe echo interval is set to 0.2ms, see fig. 5.
On the basis of any one of the above embodiments of the present invention, the pore radius distribution map based on the digital core and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2The step of the relational expression of the values specifically includes:
accumulating the porosity component corresponding to each pore radius according to the pore radius from large to small based on the digital core pore radius distribution diagram to obtain a variation curve of the first accumulated porosity and the pore radius;
based on said nuclear magnetic resonance T2Spectrum according to nuclear magnetic resonance T2The value of T for each NMR is from large to small2The porosity component corresponding to the value is accumulated to obtain a second accumulated porosity and a nuclear magnetic resonance T2A change in value curve.
On the basis of any one of the above embodiments of the present invention, the pore radius distribution map based on the digital core and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2The step of relating values, further comprising:
according to the principle of equal porosity, comparing the variation curve of the first cumulative porosity and the pore radius, and the second cumulative porosity and the nuclear magnetic resonance T2Curve of variation of value through pore radius r at the same porositycAnd nuclear magnetic resonance T2Value, establish pore radius rcAnd nuclear magnetic resonance T2A cross plot of values;
for the pore radius rcAnd nuclear magnetic resonance T2Fitting the intersection graph of the values by a formula to obtain the radius r of the porecAnd T2Conversion of values relation: r isc＝C(T2)。
It should be noted that the above numbers are only from the standpoint of the principles of nuclear magnetic resonance and CTCharacter core pore radius distribution diagram and nuclear magnetic resonance T2The physical meanings represented by the spectrograms are consistent, but the sampling points of the spectrograms are different, the represented pore radius ranges are also different, and similarity comparison cannot be directly carried out according to the shapes, so that the method adopts the principle of equal porosity for comparison.
The method specifically comprises the following steps: accumulating the porosity component corresponding to each pore radius according to the pore radius distribution diagram from large to small of the digital core pore radius to obtain a variation curve of the first accumulated porosity and the pore radius, and referring to fig. 6; for nuclear magnetic resonance T2Spectrum according to nuclear magnetic resonance T2The value of T for each NMR is from large to small2The porosity component corresponding to the value is accumulated to obtain a second accumulated porosity and a nuclear magnetic resonance T2Curves of change, see fig. 7; according to the principle of equal porosity, comparing the variation curve of the first cumulative porosity and the pore radius, and the second cumulative porosity and the nuclear magnetic resonance T2Curve of variation of value through pore radius r at the same porositycAnd nuclear magnetic resonance T2Value, establish pore radius rcAnd nuclear magnetic resonance T2A cross plot of values, see FIG. 8; for pore radius rcAnd nuclear magnetic resonance T2Fitting the intersection graph of the values by a formula to obtain the radius of the pore and the nuclear magnetic resonance T2Conversion relation r of valuec＝C(T2)。
In this example, the pore radius and T are obtained by fitting2The conversion relation of the values is not a simple linear relation, the correlation coefficient reaches more than 0.9, and in addition, the pore radius distribution calculated according to the conversion relation is consistent with the pore size observed by a scanning electron microscope.
The embodiment of the invention provides a compact sandstone pore diameter and nuclear magnetic resonance T2A method for determining the value conversion relation between the pore radius of the tight sandstone and the nuclear magnetic resonance T2Quantitative calculation of value conversion relation2The spectrogram is converted into a pore radius distribution diagram, compared with the prior art which utilizes mercury intrusion pore throat distribution and nuclear magnetic resonance T2The conversion relation obtained by comparing the spectrograms is more reliable,and the full-size pore structure of the compact sandstone reservoir is further accurately characterized, so that guidance is provided for evaluation and development practice of the compact sandstone gas reservoir.
FIG. 9 shows a tight sandstone pore size and NMR T provided in an embodiment of the present invention2The schematic structural diagram of the determination system of the value conversion relationship, see fig. 9, includes:
a scanning unit: the CT scanning device is used for carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core;
an acquisition unit: the digital core pore radius distribution diagram is obtained based on the pore radius and pore volume data;
a measurement unit: is used for carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram;
a fitting unit: for the core hole radius distribution map and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values.
The embodiment of the invention provides a compact sandstone pore diameter and nuclear magnetic resonance T2The determination system of the value conversion relation performs CT scanning on the acquired compact sandstone sample through a scanning unit to obtain a three-dimensional digital core; acquiring pore radius and pore volume data based on the three-dimensional digital core through an acquisition unit, and further acquiring a digital core pore radius distribution map; performing saturated brine nuclear magnetic resonance measurement on the compact sandstone sample through a measurement unit to obtain nuclear magnetic resonance T2A spectrogram; comparing the digital core pore radius distribution diagram with the nuclear magnetic resonance T through a fitting unit2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values. Realizing compact sandstone pore radius and nuclear magnetic resonance T2Quantitative calculation of value conversion relationshipsNuclear magnetic resonance of T2The spectrogram is converted into a pore radius distribution diagram, compared with the prior art which utilizes mercury intrusion pore throat distribution and nuclear magnetic resonance T2The conversion relation obtained by comparison of the spectrograms is more reliable, and the full-size pore structure of the compact sandstone reservoir is further accurately represented, so that guidance is provided for evaluation and development practice of the compact sandstone gas reservoir.
On the basis of the above embodiment of the present invention, the tight sandstone sample is a plunger sample with a diameter of 6mm and a length of 20 mm.
On the basis of the above embodiment of the present invention, the scanning unit is specifically configured to:
scanning the compact sandstone sample by using a CT scanning device to obtain a CT value three-dimensional data volume of the compact sandstone sample;
and carrying out threshold processing on the CT value three-dimensional data volume through image processing software to obtain a three-dimensional digital core capable of distinguishing a pore space and a rock skeleton.
On the basis of the foregoing embodiment of the present invention, the obtaining unit is specifically configured to:
and identifying the pores and throats of the three-dimensional digital core to obtain the radius of all identifiable pores and the volume data of the pores.
The abscissa of the digital core pore radius distribution diagram is the pore radius, and the ordinate is the porosity component.
On the basis of the above embodiment of the invention, the saturated saline is a sodium chloride solution with the concentration of 40000 mg/L; the echo interval used for the nuclear magnetic resonance measurement is less than or equal to 0.2 ms.
On the basis of the above embodiment of the present invention, the fitting unit is specifically configured to:
accumulating the porosity component corresponding to each pore radius according to the pore radius from large to small based on the digital core pore radius distribution diagram to obtain a variation curve of the first accumulated porosity and the pore radius;
based on said nuclear magnetic resonance T2Spectrum according to nuclear magnetic resonance T2The value of T for each NMR is from large to small2Holes corresponding in valueThe porosity components are accumulated to obtain a second accumulated porosity and a nuclear magnetic resonance T2A change in value curve.
According to the principle of equal porosity, comparing the variation curve of the first cumulative porosity and the pore radius, and the second cumulative porosity and the nuclear magnetic resonance T2Curve of variation of value through pore radius r at the same porositycAnd nuclear magnetic resonance T2Value, establish pore radius rcAnd nuclear magnetic resonance T2A cross plot of values;
for the pore radius rcAnd nuclear magnetic resonance T2Fitting the intersection graph of the values by a formula to obtain the radius r of the porecAnd T2Conversion of values relation: r isc＝C(T2)。
The embodiment of the invention provides a compact sandstone pore diameter and nuclear magnetic resonance T2A determination system of value conversion relation for realizing compact sandstone pore radius and nuclear magnetic resonance T2Quantitative calculation of value conversion relation2The spectrogram is converted into a pore radius distribution diagram, compared with the prior art which utilizes mercury intrusion pore throat distribution and nuclear magnetic resonance T2The conversion relation obtained by comparison of the spectrograms is more reliable, and the full-size pore structure of the compact sandstone reservoir is further accurately represented, so that guidance is provided for evaluation and development practice of the compact sandstone gas reservoir.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (7)
1. Compact sandstone aperture and nuclear magnetic resonance T2The method for determining the value conversion relationship is characterized by comprising the following steps of:
carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core;
acquiring pore radius and pore volume data through the three-dimensional digital core, and acquiring a digital core pore radius distribution diagram based on the pore radius and pore volume data, wherein the abscissa of the digital core pore radius distribution diagram is the pore radius, and the ordinate is the porosity component;
carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram;
based on the digital core pore radius distribution diagram and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values;
based on the digital core pore radius distribution diagram and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2The step of the relational expression of the values specifically includes:
accumulating the porosity component corresponding to each pore radius according to the pore radius from large to small based on the digital core pore radius distribution diagram to obtain a variation curve of the first accumulated porosity and the pore radius;
based on said nuclear magnetic resonance T2Spectrum according to nuclear magnetic resonance T2The value of T for each NMR is from large to small2The porosity component corresponding to the value is accumulated to obtain a second accumulated porosity and a nuclear magnetic resonance T2A change curve of the value;
according to the principle of equal porosity, comparing the variation curve of the first cumulative porosity and the pore radius, and the second cumulative porosity and the nuclear magnetic resonance T2Curve of variation of value through pore radius r at the same porositycAnd nuclear magnetic resonance T2Value, establish pore radius rcAnd nuclear magnetic resonance T2A cross plot of values;
for the pore radius rcAnd nuclear magnetic resonance T2Fitting the intersection graph of the values by a formula to obtain the radius r of the porecAnd T2Conversion of values relation: r isc＝C(T2)。
2. The tight sandstone pore size and nuclear magnetic resonance T of claim 12The method for determining the value conversion relationship is characterized in that the tight sandstone sample is a plunger sample with the diameter of 6mm and the length of 20 mm.
3. The tight sandstone pore size and nuclear magnetic resonance T of claim 12The method for determining the value conversion relationship is characterized in that the step of performing CT scanning on the obtained compact sandstone sample to obtain the three-dimensional digital core specifically comprises the following steps:
scanning the compact sandstone sample by using a CT scanning device to obtain a CT value three-dimensional data volume of the compact sandstone sample;
and carrying out threshold processing on the CT value three-dimensional data volume through image processing software to obtain a three-dimensional digital core capable of distinguishing a pore space and a rock skeleton.
4. The tight sandstone pore size and nuclear magnetic resonance T of claim 12The method for determining the value conversion relationship is characterized in that the method for acquiring the pore radius and pore volume data through the three-dimensional digital core specifically comprises the following steps:
and identifying the pores and throats of the three-dimensional digital core to obtain the radius of all identifiable pores and the volume data of the pores.
5. The tight sandstone pore size and nuclear magnetic resonance T of claim 12The method for determining the value conversion relationship is characterized in that the saturated saline is a sodium chloride solution with the concentration of 40000 mg/L.
6. The tight sandstone pore size and nuclear magnetic resonance T of claim 1 or 52Method for determining a value transformation relation, characterized in that the echo interval used for the nuclear magnetic resonance measurement is less than or equal to 0.2 ms.
7. Compact sandstone aperture and nuclear magnetic resonance T2A system for determining a value conversion relationship, comprising:
a scanning unit: the CT scanning device is used for carrying out CT scanning on the obtained compact sandstone sample to obtain a three-dimensional digital core;
an acquisition unit: the system comprises a three-dimensional digital core, a data acquisition module and a data acquisition module, wherein the three-dimensional digital core is used for acquiring pore radius and pore volume data and acquiring a digital core pore radius distribution diagram based on the pore radius and pore volume data, the abscissa of the digital core pore radius distribution diagram is the pore radius, and the ordinate of the digital core pore radius distribution diagram is the porosity component;
a measurement unit: is used for carrying out saturated brine nuclear magnetic resonance measurement on the compact sandstone sample to obtain nuclear magnetic resonance T2A spectrogram;
a fitting unit: for the core hole radius distribution map and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2A relational expression of values;
based on the digital core pore radius distribution diagram and the nuclear magnetic resonance T2Establishing a pore radius r according to the principle of equal porositycAnd nuclear magnetic resonance T2Cross plot of values fitted to aperture radius rcAnd nuclear magnetic resonance T2The step of the relational expression of the values specifically includes:
accumulating the porosity component corresponding to each pore radius according to the pore radius from large to small based on the digital core pore radius distribution diagram to obtain a variation curve of the first accumulated porosity and the pore radius;
based on said nuclear magnetic resonance T2Spectrum according to nuclear magnetic resonance T2The value of T for each NMR is from large to small2The porosity component corresponding to the value is accumulated to obtain a second accumulated porosity and a nuclear magnetic resonance T2A change curve of the value;
comparing the first cumulative porosity with the pore radius according to the equal porosity principleAnd the second cumulative porosity and nuclear magnetic resonance T2Curve of variation of value through pore radius r at the same porositycAnd nuclear magnetic resonance T2Value, establish pore radius rcAnd nuclear magnetic resonance T2A cross plot of values;
for the pore radius rcAnd nuclear magnetic resonance T2Fitting the intersection graph of the values by a formula to obtain the radius r of the porecAnd T2Conversion of values relation: r isc＝C(T2)。
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| CN113405962B (en) * | 2020-03-16 | 2023-02-10 | 中国石油天然气股份有限公司 | Storage space evaluation method and device for carbonate reservoir |
| CN111366521B (en) * | 2020-04-14 | 2023-08-11 | 清能艾科（深圳）能源技术有限公司 | Method for multi-scale determination of porosity and related apparatus |
| CN111537544B (en) * | 2020-06-08 | 2023-04-07 | 长安大学 | Improve nuclear magnetic resonance T 2 Conversion method for spectral characterization of pore size distribution precision of tight reservoir |
| CN112067645B (en) * | 2020-07-31 | 2022-07-05 | 中国石油大学(北京) | Conversion method of nuclear magnetic resonance relaxation time and pore throat radius |
| CN112284999B (en) * | 2020-10-26 | 2022-06-17 | 中国石油大学(华东) | Sandstone pore size distribution determination method and application thereof |
| CN113008927A (en) * | 2021-04-01 | 2021-06-22 | 中海石油(中国)有限公司 | Conversion method of nuclear magnetic resonance T2 spectrum and pore distribution of coal seam |
| CN113253354A (en) * | 2021-05-12 | 2021-08-13 | 中国石油天然气集团有限公司 | Nuclear magnetic T2Method, device, medium and electronic device for determining spectrum cutoff value |
| CN114112856A (en) * | 2021-12-07 | 2022-03-01 | 核工业北京化工冶金研究院 | Uranium-bearing sandstone full-size pore structure characterization method and system |
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