Device and measuring method for hydrocarbon diffusion coefficient in rocks under high temperature and high pressure

Abstract

The invention provides a device and measuring method for the hydrocarbon diffusion coefficient in rocks under high temperature and high pressure. The device mainly comprises a rock diffusion coefficient tester, a vacuum pump, a confining pressure pump, hydrocarbon gas source, nitrogen (N2) gas source, a left piston container, a right piston container, an automatic pressure pump, a chromatographic detector, a computer, a drying device and a rock saturated water device and the like. According to the device and method, the consistent accurate accordance of the gas injection balance pressure in the diffusion chambers respectively arranged at two ends of a core holder can be achieved and the existence of the hydrocarbon diffusion driven by the concentration gradient not by the pressure gradient in the whole process of experiment is ensured. Meanwhile, according to the device and method, the problem of low gas injection balance pressure, relatively low experimental temperature and having difference with the actual formation condition of the gas source balance pressure control device in the measuring of normal diffusion coefficient is resolved.

Description

technical field [0001] The invention relates to an experimental equipment and a measuring method for measuring the diffusion coefficient of hydrocarbons in rocks, in particular to an experimental equipment and a measuring method for measuring the diffusing coefficients of hydrocarbons in rocks under high temperature and high pressure conditions, belonging to natural gas geology in the technical field of petroleum exploitation Analyze technical fields. Background technique [0002] Diffusion refers to a physical process in which gas molecules migrate freely from a high-concentration area through various media to a low-concentration area under the action of a concentration gradient of hydrocarbon gas to reach equilibrium. Diffusion is one of the important mechanisms of oil and gas migration. It is important for the migration, accumulation, and accumulation of oil and gas, especially natural gas (due to its small molecule, light weight, and strong activity, so it has strong dif...

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Problems solved by technology

[0003] At present, the determination of the diffusion coefficient of rock hydrocarbons in laboratories at home and abroad is mainly carried out under the conditions of normal temperature and normal pressure (room temperature 22°C, 0.2MPa gas injection equilibrium pressure, 3MPa confining pressure), and the existing diffusion coefficient measurement devices mostly use precision pressure gauges, etc. Controlling the balance pressure of gas injection in the diffusion chambers at both ends cannot well ensure that the balance pressure of gas injection in the diffusion chambers at both ends remains the same at all times, and it is easy to generate a small pressure difference, so it cannot fully guarantee that the entire experimental process is only driven by concentration gradients without pressure gradients. In addition, because the gas injection equilibrium pressure controlled by the conventional gas source pressure control equipment is generally small and the experimental temperature is relatively low, there is a big difference between the rock in the formation in the state of saturated formation water, high temperature and high pressure under the actual geological conditions. Can not reflect the true diffusion ability of rock hydrocarbons under geological conditions

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