Device and method for testing gas diffusion coefficient in porous media

Abstract

The invention discloses a device and a method for testing a gas diffusion coefficient in a porous medium. The device mainly comprises a clamp holder, gas sampling systems, a confining pressure pump, a pressure balancing system, a gas supply system, a gas chromatograph analyzer and a vacuum pump; the two ends of the clamp holder are connected to the inlet ends of the gas sampling systems; the outlet ends of the gas sampling systems are connected with the gas chromatograph analyzer and the vacuum pump; the two ends of the clamp holder are connected with the gas supply system respectively, and are also connected with the confining pressure pump and the pressure balancing system; the clamp holder comprises a housing, a sample bridge, a sample cavity and a plug; a confining pressure cavity is arranged in the housing; the sample bridge is positioned in the center of the clamp holder; a porous medium sample is stored in the sample cavity. Through the adoption of the method, influence on a test result, which is caused by the seepage flow of gases in the porous medium in a testing process and pressure fluctuation during gas sampling, is eliminated, and interference of residual gases in a sampling pipeline to the test result is effectively reduced. The device and the method are reliable in principle and simple and convenient to operate, improves the accuracy of the diffusion coefficient to be tested, and has a broad market prospect.

Description

technical field [0001] The invention relates to a device and method for testing gas diffusion coefficient in porous media in the field of molecular mass transfer analysis, and is especially suitable for measuring device and method for gas-gas two-component diffusion coefficient in porous media. Background technique [0002] Molecular diffusion (diffusion for short) is a common phenomenon in nature, which specifically refers to the phenomenon of directional transfer of molecules in the system caused by the difference of substance concentration in the macroscopic view. Molecular diffusion coefficient (referred to as diffusion coefficient) is a physical quantity that reflects the diffusion ability of a substance, and is used to quantitatively describe the strength of molecular diffusion under certain conditions. Diffusion coefficient is widely used in oil and gas migration research, analysis of underground oil and gas reserves, productivity prediction, gas injection to enhance ...

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Problems solved by technology

[0007] (2) During the indirect method test, the existing sampling method brings errors to the test results

[0008] In the indirect method, it is necessary to sample the gas in the gas chamber at both ends of the porous medium many times for chromatographic analysis of the concentration change of the components. However, the current published devices generally cause pressure disturbances in the gas chamber at both ends of the porous medium when sampling, thus giving Diffusion Coefficient Measurements Introduce Errors

In addition, during multiple sampling and analysis, the last sampling gas remaining in the pipeline connected to the gas component analysis system will also affect the next analysis result (Chinese patents CN1773246A, CN102980837B)

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