Device and method for determining molecular diffusion coefficient of multi-component gas-liquid system in rock core

Abstract

The invention relates to a device and method for determining a molecular diffusion coefficient of a multi-component gas-liquid system in a rock core. The device mainly comprises an inlet pump, a confining pressure pump, a pressure returning pump, an intermediate container, a rock core clamper, an oil-gas two-phase separator, a pressure sensor and a computer, wherein one end of the intermediate container is connected with the inlet pump; thee other end of the intermediate container is connected with the rock core clamper; the rock core clamper is connected with the pressure return pump, the confining pressure pump and the oil-gas two-phase separator; and two ends of the rock core clamper are connected with the pressure sensor and the computer. The method comprises the following steps of: transferring an oil sample and a gas sample into the rock core through the inlet pump; contacting an oil phase with a gas phase to generate diffusion and cause the reduction of the gas phase pressure; monitoring the pressure change of a gas phase zone; after the gas and liquid reach the balance, enabling the drained fluid in the rock core to enter the oil-gas two-phase separator; and analyzing and testing the gas phase composition and the property change. The device and method disclosed by the invention are reliable in principle and simple and convenient in operation; and the molecular diffusion coefficient of each component of the multi-component gas-liquid system in real rock core in the gas phase and oil phase can be determined under different temperature and pressure conditions of an oil reservoir and reasonable base data is provided for quantitatively evaluating the influence on the improvement on the recovery ratio caused by a molecular diffusion effect.

Description

technical field [0001] The patent of the present invention relates to the determination of the molecular diffusion coefficient of mass transfer between the gas-liquid phase, especially the device and method for determining the molecular diffusion coefficient of a multi-component oil-gas system in the actual rock core under high temperature and high pressure conditions in the petroleum industry. Background technique [0002] Gas injection to enhance oil recovery is an important technical means to enhance oil recovery at home and abroad. The injected gas and formation crude oil change the fluid properties of crude oil through interphase mass transfer and improve the flow capacity of crude oil. The experimental test of gas-oil phase equilibrium is the basic work of gas injection scheme design, which provides fluid high-pressure physical property parameters for gas injection numerical simulation; among them, the determination of molecular diffusion coefficient is an important par...

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Problems solved by technology

[0004] (1) The theoretical estimation method is only applicable to the calculation of the diffusion coefficient of single-component or three-component oil and gas molecules;

[0005] (2) Most of the molecular diffusion coefficient test methods do not consider the influence of porous media;

[0006] (3) The experimental test temperature and pressure conditions cannot meet the actual gas injection requirements of the oil field;

[0007] (4) The determination method of molecular diffusion coefficient based on concentration test established by Juarez et al. is only applicable to single-component gas-liquid system in

[0008] Molecular diffusion in the sand-packing model cannot determine the molecular diffusion coefficient of multi-component hydrocarbon systems in real oil and gas reservoirs

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