Coal pore correction method based on mercury injection experiment

A correction method and pore technology, which is applied in the analysis of suspensions and porous materials, measuring devices, instruments, etc., can solve the problems of increased mercury injection, calculation errors, calculation models and actual pore errors, etc.

Active Publication Date: 2019-02-15
HENAN POLYTECHNIC UNIV
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Problems solved by technology

Since the coal matrix is ​​elastic and compressible, the mercury injection test will produce a compression effect on the coal under high pressure, resulting in an increase in the amount of mercury injection. The direct interpretation of the test data is that the transition pores (2-50nm) are significantly higher than the real value; (3) Calculation error caused by pore shape: In the calculation of mercury injection volume, it is assumed that the pores are cylindrical pores and obtained from the Washburn equation. In the calculation of specific surface area, it is assumed that the sample must not contain ink bottle-shaped pores and will not deform under external pressure. Ink bottle pores are widely developed in coal, and can be compressed and deformed during the mercury injection process, which makes there are major errors between the commonly used calculation models and the actual pores

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  • Coal pore correction method based on mercury injection experiment
  • Coal pore correction method based on mercury injection experiment
  • Coal pore correction method based on mercury injection experiment

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0065] Embodiment 1. The correction of matrix compression effect is as follows:

[0066] The amount of mercury injected during the mercury injection test is the sum of the amount of mercury filled in the pores, the amount of compression deformation of the matrix, and the amount of shrinkage deformation of pores not filled with mercury. As the mercury injection pressure increases, the amount of mercury-filled pores will gradually increase, and the pore deformation will also change accordingly. Therefore, in the process of mercury injection, the mercury injection amount under different mercury injection pressures is related to the number of pores in the coal and the compression of the coal matrix. The amount of deformation and the amount of shrinkage and deformation of coal pores is a dynamic process, and the relationship between the three is extremely complicated. It is difficult to accurately describe the continuous change of each variable and the relationship between them. Ho...

Embodiment 2

[0076] Embodiment 2, the intergranular pore effect and the hemp skin effect correction are as follows:

[0077] The mercury injection error in the low-pressure section is mainly due to the intergranular pore effect and the hemp skin effect. When the particle size of the test sample is small and the particles are randomly piled up, mercury can only enter the gaps between the particles under a certain pressure. The amount of mercury intrusion caused by the intergranular pores is called the intergranular pore effect. The surface of coal particles is uneven, with well-developed edges and corners. At the initial stage of mercury injection, it is difficult to be completely filled with mercury in the rough pits and corners. As the pressure gradually increases, the cavity gradually shrinks and disappears until it is completely filled with mercury. The amount is called the hemp effect. This is an important factor affecting the amount of mercury injected in the low-pressure section.

...

Embodiment 3

[0082] Embodiment 3, the correction of pore shape effect is as follows:

[0083] According to the provisions of ISO 15901-1:2005, the pores of porous materials are cylindrical, and the relationship between the calculated pressure and the pore diameter is calculated by the washburn equation to obtain the following formula:

[0084]

[0085] Among them, σ is the surface tension of mercury, which is 0.485N / m; d p is the pore diameter, in nm; p is the mercury injection pressure, in MPa; θ is the wetting angle of coal to mercury, in radians;

[0086] The relationship between pore diameter and pressure is also different for different pore shapes. The mercury injection pressure is related to the additional pressure Δp generated by the curved liquid surface in the pore fissure. According to the Young-Laplace equation, the relationship between Δp and the radius of curvature of the liquid surface in different shapes can be obtained for:

[0087]

[0088] Among them, σ is the sur...

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Abstract

The invention discloses a coal pore correction method based on a mercury injection experiment. The coal pore correction method comprises the following steps: 1) performing low pressure section and high pressure section mercury injection tests on a to-be-tested coal sample by utilizing a mercury injection instrument and obtaining mercury injection data; 2) performing pore structure correction including matrix compression effect correction, inter-granular pore effect and skin effect correction effect correction and pore shape effect correction; 3) performing quantitative characterization on a pore structure by utilizing corrected data. The invention provides a model for correcting coal pores by utilizing the mercury injection tests, which can be used for coal-bed methane reservoir evaluationand research on gas prevention and control and the like; a mercury injection test method in the national standard is referenced and utilized, mercury injection pressure and mercury injection amount data are obtained, and then related factors affecting the mercury injection test accuracy are corrected; correction results can accurately characterize the coal pores. Therefore, a strong technical support is provided for coal-bed methane exploitation and underground gas prevention and control.

Description

technical field [0001] The invention relates to the technical field of mercury intrusion experiments, in particular to a method for correcting pores in coal based on mercury intrusion experiments. Background technique [0002] Pores in coal are the main channels for the occurrence and migration of groundwater and coalbed methane (gas). The development characteristics of pores in coal reservoirs (pore number, pore size, and pore size distribution, etc.) directly affect the enrichment and migration of coalbed methane. It is an important basic parameter for gas prevention and coalbed methane mining. Accurate determination of pore characteristics in coal reservoirs is of great significance for underground gas drainage in coal mines and surface coalbed methane development. [0003] The real pore information obtained from the mercury intrusion test is restricted by many factors, and the influencing factors are different for different particle sizes and different pressure stages. ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N15/08
CPCG01N15/088G01N15/0886G01N2015/0813
Inventor 宋党育李云波何凯凯吉小峰
Owner HENAN POLYTECHNIC UNIV
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