CN114544684A - Rock sample hole fracture structure characterization method - Google Patents

Rock sample hole fracture structure characterization method Download PDF

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Publication number
CN114544684A
CN114544684A CN202210078284.0A CN202210078284A CN114544684A CN 114544684 A CN114544684 A CN 114544684A CN 202210078284 A CN202210078284 A CN 202210078284A CN 114544684 A CN114544684 A CN 114544684A
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Prior art keywords
shale sample
sample
metal
shale
pore
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崔子昂
孙梦迪
潘哲君
高波
王永超
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China University of Geosciences
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China University of Geosciences
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
    • G01N23/2251—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident electron beams, e.g. scanning electron microscopy [SEM]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/2202—Preparing specimens therefor

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
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Abstract

The invention provides a rock sample pore fracture structure characterization method, and relates to the field of unconventional natural gas experiments; the method for characterizing the pore fracture structure of the rock sample comprises the following steps: s1, preparing a shale sample, and drying the shale sample; s2, placing the shale sample and the solid metal into a pressurizing container, melting the solid metal into liquid metal, injecting the liquid metal into the shale sample, and cooling and solidifying the liquid metal to obtain the shale sample after the metal is injected; s3, cutting the shale sample after metal injection, and observing through a scanning electron microscope to obtain the pore crack structural characteristics of the shale sample; the invention can observe the real occurrence condition of the solid metal in the pore structure of the shale sample, the communication condition of the pore structure and the size of the pore structure which can be entered by the liquid metal under different target pressures, thereby realizing the visualization of the pore structure in the shale sample.

Description

Rock sample hole fracture structure characterization method
Technical Field
The invention relates to the field of unconventional natural gas experiments, in particular to a rock sample pore fracture structure characterization method.
Background
The pore structure of shale reservoirs is more complex than conventional sandstone and carbonate reservoirs, including networks of interconnected pores and networks of unconnected pores. The characterization of the shale pore structure has important significance for the evaluation of shale gas reserves and the research of shale gas migration behavior.
In recent years, the high-pressure mercury intrusion method is widely applied to the aspect of porous medium evaluation as an effective pore size distribution characterization means. The mercury injection basic principle is as follows: mercury is not wet to general solid, external pressure is applied to make mercury enter pore throats, and the larger the external pressure is, the smaller the radius of the pore throats where mercury can enter is. The pore volume of the pore throat can be known by measuring the volume of mercury entering the pore under different external pressures. However, during the process of reducing the pressure of the mercury pressing, the mercury automatically flows out of the sample due to the pressure reduction, and the actual occurrence of the mercury in different pressure stages in the pores of the porous medium cannot be observed. In addition, the experimental sample can be polluted by mercury, mercury and compounds thereof can invade human bodies through different ways such as respiratory tract, skin or digestive tract, and the contact of experimenters and mercury vapor can cause great influence on the health.
Disclosure of Invention
The invention aims to solve the technical problem that the actual occurrence condition of metal in a rock sample pore crack structure cannot be observed when the rock sample pore crack structure is represented by the existing high-pressure mercury intrusion method.
The invention provides a rock sample hole fracture structure characterization method, which comprises the following steps:
s1, preparing a shale sample, and drying the shale sample;
s2, placing the shale sample and the solid metal into a pressurizing container, melting the solid metal into liquid metal, injecting the liquid metal into the shale sample, and cooling and solidifying the liquid metal to obtain the shale sample after the metal is injected;
and S3, cutting the shale sample after metal injection, and observing through a scanning electron microscope to obtain the pore crack structural characteristics of the shale sample.
Further, in step S1, the method for preparing the shale sample is as follows:
weighing a certain mass of shale, and cutting 0.5-2 cm of shale along the vertical bedding direction of a shale core column3The shale sample is obtained.
Further, in step S1, the method of the drying process is as follows:
and (3) placing the shale sample in a vacuum drying oven, and drying for 24-48 h at the temperature of 60-100 ℃.
Further, in step S2, the method for preparing the shale sample after metal injection includes the following steps:
s21, carrying out vacuum pumping treatment on the pressurizing container to enable the vacuum degree in the pressurizing container to be 0.05-0.1 Pa;
s22, heating the solid metal to be molten into liquid metal;
s23, pressurizing the air pressure in the pressurizing container to a target pressure so that the liquid metal is injected into the shale sample;
and S24, cooling to solidify the liquid metal, and reducing the pressure in the pressurizing container to atmospheric pressure to obtain the shale sample injected with the metal.
Further, the target pressure is 0-200 MPa
Further, in step S2, the solid metal is an alloy composed of tin, indium, bismuth, and lead, and has a melting point of 40 to 80 ℃.
Further, in step S3, the shale sample after metal injection is cut along a direction perpendicular to the inside of the layer.
Further, in step S3, before observing the pore structure of the shale sample through the scanning electron microscope, the fracture surface of the shale sample after being injected with the metal is subjected to argon ion polishing treatment.
The technical scheme provided by the embodiment of the invention has the following beneficial effects: according to the method for characterizing the pore fracture structure of the rock sample, solid metal is melted into liquid metal and then injected into the shale sample, after the liquid metal is cooled and solidified, the shale sample after the metal is injected is cut, and the pore fracture structure characteristics of the shale sample are obtained through observation of a scanning electron microscope, so that the real occurrence condition of the solid metal in the pore fracture structure of the shale sample, the communication condition of the pore fracture structure and the size of the pore fracture structure into which the liquid metal can enter under different target pressures can be observed, and the visualization of the pore fracture structure in the shale sample is realized; simultaneously, through pouring into liquid metal to wait that liquid metal solidifies the back and cut the shale sample, can avoid to a certain extent because of adopting the direct damage to the hole crack structure in the shale sample that leads to the fact of cutting the shale sample of cutting machine.
Drawings
FIG. 1 is a scanning electron microscope image of an edge crack of a shale sample after metal injection in an embodiment of the present disclosure;
FIG. 2 is a scanning electron microscope image of internal fractures of a shale sample after metal injection in an embodiment of the present disclosure;
FIG. 3 is a graph of the spectral analysis of the corresponding sample at EDS Spot 1 in FIG. 2.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
The embodiment of the invention provides a rock sample hole fracture structure characterization method, which comprises the following steps:
s1, preparing a shale sample, and drying the shale sample;
s2, placing the shale sample and the solid metal into a pressurizing container, melting the solid metal into liquid metal, injecting the liquid metal into the shale sample in a pressurizing mode, and obtaining the shale sample after the metal is injected after the liquid metal is cooled and solidified;
and S3, cutting the shale sample after metal injection along the central plane and the direction vertical to the inside of the layer, and observing through a scanning electron microscope to obtain the pore crack structural characteristics of the shale sample.
In the step, cutting the shale sample after being injected with metal through a cutting machine; the scanning electron microscope obtains a photo of a section of the shale sample, and the photo is judged according to the characteristic of higher gray value and EDS (electron-ray spectroscopy) element analysis, so that the pore crack structural characteristic of the shale sample can be obtained; the EDS energy spectrum element analysis is used to detect whether the sample in the feature corresponding region with a higher gray value contains the metal element injected in this embodiment.
Specifically, in step S1, the method for preparing the shale sample is as follows:
weighing a certain mass of shale, and cutting 0.5-2 cm along the vertical bedding direction of a shale core column3The shale sample is obtained.
Illustratively, in this embodiment, the shale sample has a size of 1cm3。
As a variation of this implementation, the shale sample may also be 0.5cm in size3Or 2cm3。
Specifically, in step S1, the method of the drying process is as follows:
and (3) placing the shale sample in a vacuum drying oven, and drying for 24-48 h at the temperature of 60-100 ℃.
Illustratively, in the embodiment, the drying temperature of the shale sample is 60 ℃, and the drying time is 48 h.
It is understood that the drying time of the shale sample can be adjusted according to the drying temperature.
Specifically, in step S2, the preparation method of the shale sample after metal injection includes the following steps:
s21, carrying out vacuum pumping treatment on the pressurizing container to enable the vacuum degree in the pressurizing container to be 0.05-0.1 Pa;
illustratively, in this embodiment, the vacuum is 0.08 Pa.
S22, heating the solid metal to be molten into liquid metal;
s23, pressurizing the air pressure in the pressurizing container to a target pressure so that the liquid metal is injected into the shale sample;
and S24, cooling to solidify the liquid metal, and reducing the pressure in the pressurizing container to atmospheric pressure to obtain the shale sample injected with the metal.
In this step, maintaining the target pressure for a certain time (so that the liquid metal can enter the pore structure of the shale sample at the target pressure for a sufficient time), and cooling the liquid metal; the time for maintaining the target pressure may be set as needed, for example, may be 1h, and may be specifically adjusted according to the magnitude of the target pressure.
Specifically, the target pressure is 0-200 MPa, the target pressure can be adjusted as required, and the sizes of pore crack structures which can be entered by liquid metal under different pressurizing conditions can be compared by setting different target pressures; illustratively, the liquid metal can be pressed into the pore structure of the shale at target pressures of 10MPa, 50MPa, 100MPa, 150MPa, and 200MPa, as desired.
Specifically, in step S2, the solid metal is an alloy composed of tin, indium, bismuth, and lead, and has a melting point of 40 to 80 ℃.
The melting point of the solid alloy can be adjusted by adjusting the proportion of tin, indium, bismuth and lead elements in the solid metal; illustratively, in the present embodiment, the melting point of the solid metal is 65 ℃, so that the solid metal is solid at room temperature, and the shale sample injected with the metal is convenient to cut and observe at room temperature; in addition, the mercury-free mercury is solid at normal temperature, is not easy to volatilize, and does not influence the health of operators compared with mercury with strong volatility.
Further, in step S3, before observing the pore structure of the shale sample through the scanning electron microscope, argon ion polishing is performed on the section of the shale sample after metal injection to obtain a smooth and flat shale sample surface, which is convenient for later observation.
According to the method for characterizing the pore fracture structure of the rock sample in the embodiment, the actual situation that liquid metal enters the pore fracture structure of the shale sample under different target pressures can be observed, the shale sample injected with the liquid metal is cut, and the injection situation of solidified solid metal in the pore fracture structure of the shale sample can be observed through a scanning electron microscope, referring to attached figures 1 and 2. The EDS point analysis is to fix an electron beam on a certain point in the shale sample to perform qualitative or quantitative analysis, and shows a peak pattern diagram given by scanning energy spectrum points, wherein each element has a peak in the diagram, so that the elements contained in the sample can be seen; as can be seen from FIG. 2 and FIG. 3, the shale sample has a large amount of Sn, in, Bi and Pb elements which are not contained in the shale itself, and the feasibility of the scheme is proved through the energy spectrum analysis of a field emission scanning electron microscope (EDS Spot 1) on the high-gray-level circle part of the pore structure in the shale sample.
The above is not relevant and is applicable to the prior art.
In this document, the terms front, back, upper and lower are used to define the components in the drawings and the positions of the components relative to each other, and are used for clarity and convenience of the technical solution. It is to be understood that the use of the directional terms should not be taken to limit the scope of the claims.
The features of the embodiments and embodiments described herein above may be combined with each other without conflict.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (8)

1. A rock sample hole fracture structure characterization method is characterized by comprising the following steps:
s1, preparing a shale sample, and drying the shale sample;
s2, placing the shale sample and the solid metal into a pressurizing container, melting the solid metal into liquid metal, injecting the liquid metal into the shale sample, and cooling and solidifying the liquid metal to obtain the shale sample after the metal is injected;
and S3, cutting the shale sample after metal injection, and observing through a scanning electron microscope to obtain the pore crack structural characteristics of the shale sample.
2. The method for characterizing the pore fracture structure of the rock sample according to claim 1, wherein in step S1, the method for preparing the shale sample is as follows:
weighing a certain mass of shale, and cutting 0.5-2 cm along the vertical bedding direction of a shale core column3The shale sample is obtained.
3. The method for characterizing the pore fracture structure of the rock sample according to claim 1, wherein in step S1, the drying treatment method comprises the following steps:
and (3) placing the shale sample in a vacuum drying oven, and drying for 24-48 h at the temperature of 60-100 ℃.
4. The method for characterizing the pore fracture structure of the rock sample according to claim 1, wherein in step S2, the preparation method of the shale sample after metal injection comprises the following steps:
s21, carrying out vacuum pumping treatment on the pressurizing container to enable the vacuum degree in the pressurizing container to be 0.05-0.1 Pa;
s22, heating the solid metal to be molten into liquid metal;
s23, pressurizing the air pressure in the pressurizing container to a target pressure so that the liquid metal is injected into the shale sample;
and S24, cooling to solidify the liquid metal, and reducing the pressure in the pressurizing container to atmospheric pressure to obtain the shale sample injected with the metal.
5. The method for characterizing the pore fracture structure of a rock sample according to claim 4, wherein the target pressure is 0-200 MPa.
6. The method for characterizing the pore fracture structure of the rock sample according to claim 1, wherein in the step S2, the solid metal is an alloy consisting of tin, indium, bismuth and lead, and the melting point is 40-80 ℃.
7. The method for pore fracture structural characterization of rock samples according to claim 1, wherein in step S3, the shale sample after metal injection is cut in a direction perpendicular to the inside of the layer.
8. The method for characterizing the pore fracture structure of the rock sample according to claim 1, wherein in step S3, before observing the pore fracture structure of the shale sample through the sem, the fracture surface of the shale sample after being injected with the metal is subjected to argon ion polishing treatment.
CN202210078284.0A 2022-01-24 2022-01-24 Rock sample hole fracture structure characterization method Pending CN114544684A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117309526A (en) * 2023-10-07 2023-12-29 东北石油大学 Preparation and application methods of multi-experiment characterization rock slice

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117309526A (en) * 2023-10-07 2023-12-29 东北石油大学 Preparation and application methods of multi-experiment characterization rock slice

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