Device and method for testing molecular diffusion coefficients in multi-component oil-gas system under high temperature and high pressure

Abstract

The invention relates to a device and method for testing molecular diffusion coefficients in a multi-component oil-gas system under high temperature and high pressure. The device consists of an inlet pump 1, an outlet pump 2, an intermediate container, a PVT (pressure-volume-temperature) cylinder 6, an oil-gas separator 7, a gas volume flow meter 8, a liquid phase density analyzer 10 and a chromatographic analyzer 9, wherein, one end of the intermediate container is connected with the inlet pump 1, and the other end of the intermediate container is connected with the PVT cylinder 6; the PVT cylinder is connected with the oil-gas separator 7; the separator is connected with the gas volume flow meter 8 and the liquid phase density analyzer 10; the gas volume flow meter and the liquid phase density analyzer are respectively connected with the chromatographic analyzer 9; and the other end of the PVT cylinder is connected with the outlet pump 2. The device has the advantages of reasonable principle and simple structure, and is convenient in operation; and by utilizing the method, the molecular diffusion coefficients of each component in a multi-component injected gas and actual crude oil system in gas phase and oil phase under the conditions of different reservoir temperature and pressure can be determined, thereby providing reasonable basic data for quantitative evaluation of influence of molecular diffusion effect on the enhancement of the recovery ratio by means of gas injection.

Description

technical field [0001] The invention relates to a testing device and method for the molecular diffusion coefficient of a multi-component oil-gas system under high-temperature and high-pressure conditions in the field of oil-gas phase state research in the petroleum industry. Background technique [0002] Gas injection to enhance oil recovery is an important technical means to enhance oil recovery in the petroleum industry. In porous media, when the injected gas contacts the crude oil, mass transfer will occur between the two, and the fluid phase composition or phase state will change. Under the combined action of viscous force, capillary force, gravity and molecular diffusion, the injected gas drives the oil-gas transition zone and crude oil to flow in porous media. The influence of molecular diffusion coefficient on gas injection effect has been recognized by scholars at home and abroad. In the process of gas injection to develop fractured reservoirs, molecular diffusion i...

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Problems solved by technology

[0005] (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;

[0006] (2) The experimental test method is only suitable for single-component alkane systems;

[0007] (3) The experimental test accuracy and temperature and pressure conditions cannot meet the actual gas injection requirements of the oil field;

[0008] (4) It is impossible to test the component concentration profile during the diffusion process

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