A Method for Determining the Dynamic Miscible Pressure in Simulating CO2 Flooding

Abstract

The invention discloses a method for determining CO2 simulation displacement performance miscibility pressure. The method comprises the steps of 1, measuring interfacial tension between CO2 and in-place oil; 2, inputting the physical property parameter of in-place oil into a PVTi module of Eclipse numerical simulation software, conducting fluid parameter fitting to enable fluid in the PVTi module to have the same property as in-place oil, simulating CO2 displacement in the PVTi module, monitoring the tension of an oil gas interface in the PVTi module when pressure is the minimum miscibility pressure in the initial stage of a measured oil deposit, and exporting fluid property data when the tension of the oil gas interface is zero; 3, substituting the exported fluid property data into a numerical simulation model of a target oil field for virtual development, and determining the miscibility pressure at the moment by analyzing the interfacial tension change of each grid in the numerical simulation model. The method is a perfect method for quantitative representation of dynamic miscibility pressure by means of physical and numerical simulation ways, and a key technical means is provided for research of CO2 displacement percolation mechanism and development law.

Description

technical field [0001] The invention relates to a simulated CO 2 Method for determination of displacement dynamic miscibility pressure, belonging to CO 2 Miscible flooding reservoir development field. Background technique [0002] CO 2 It is a gas with high solubility in both oil and water. When it dissolves in crude oil in a large amount, it can not only expand the volume of crude oil and reduce the viscosity, but also reduce the interfacial tension between oil and water, thereby improving the displacement of crude oil in rock pores. efficiency, while at reservoir temperature when the pressure reaches CO 2 At the minimum miscibility pressure, CO 2 It will reach a miscible state with crude oil, and the oil displacement efficiency can be increased to 100%; CO 2 The carbonic acid formed after dissolving in water can also play an acidifying role. It is not affected by conditions such as well depth, temperature, pressure, formation water salinity, etc. Due to the above eff...

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Problems solved by technology

[0003] However, during CO 2 During flood development, with the CO 2 It continuously extracts light components in the formation fluid, making the subsurface fluid components gradually heavier, so theoretically the miscible pressure will continue to increase. However, the minimum miscible pressure obtained by indoor physical simulation experiments is only oil The initial minimum miscible pressure is the minimum miscible pressure of reservoir development. With the development of the oil field, if the initial minimum miscible pressure is still used, the effect of miscible development will be greatly reduced.

Due to the constant change of formation fluid components, some parameters required in the empirical formula method cannot be obtained at any time, so the conventional empirical formula method cannot obtain the dynamic miscible pressure in the reservoir

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