Device and method for measuring axial diffusion coefficient of gas in porous medium

Abstract

The invention provides a device and a method for measuring an axial diffusion coefficient of gas in a porous medium and belongs to the field of oil-gas field development. The device comprises a constant temperature oil bath (1), and a holder (2), a container (16) and a high pressure gas cylinder (11) which are arranged in the constant temperature oil bath (1), wherein a lead sleeve (4) is arranged in the holder (2) and is in a cylindrical structure of which two ends are open; a plug (3) is arranged at one end of the lead sleeve (4), and a plug (7) with a valve is arranged at the other end of the lead sleeve (4); an outer cylindrical surface of the plug (3) and an outer cylindrical surface of the plug (7) with the valve are in sealing contact with an inner surface of the lead sleeve (4); a sample cavity is formed in an inner cavity of the lead sleeve (4) between the plug (3) and the plug (7) with the valve; a porous medium (5) is arranged in the sample cavity.

Description

technical field [0001] The invention belongs to the field of oil and gas field development, in particular to a device and method for measuring the axial diffusion coefficient of gas in a porous medium. Background technique [0002] There are currently two methods for measuring the diffusion coefficient of gases in liquids in the literature. Generally speaking, these methods are divided into two categories: direct methods and indirect methods. Whether it is direct or indirect measurement, it can only describe the concentration or diffusion of the gas in the liquid phase, but cannot directly measure the diffusion coefficient of the gas. [0003] (1) Direct method: sample the fluid at different times and different diffusion distances, then analyze these samples to obtain the gas concentration data, and then combine the corresponding mathematical model to derive the diffusion coefficient. However, the sampling process disturbs the flow field in the system, which causes experime...

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Problems solved by technology

The Petroleum and Natural Gas Industry Standard SY / T6129-1995 of the People's Republic of China has formulated the standard for the determination of the diffusion coefficient of hydrocarbon gases in rocks. This standard fixes the core in the holder and injects nitrogen and hydrocarbon gas into the diffusion chambers at both ends of the core. , by gas chromatography to measure the composition of gas at both ends under different time conditions, and the diffusion coefficient of hydrocarbon gas in porous media can be obtained through processing. There are two shortcomings of this method: one is that it is difficult to realize without gas chromatography; Second, sampling the gas in the diffusion chamber at both ends will destroy the diffusion balance and cause large experimental errors.

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