CO2 injecting and oil deposit displacing CO2 mixed-phase area judging method

Abstract

The invention discloses a CO2 injecting and oil deposit displacing CO2 mixed-phase area judging method. The method comprises the steps that fine oil deposit description is conducted on a target oil deposit, and a fine oil deposit geologic model is established; numerical simulation research of the target oil deposit is carried out, and an oil layer pressure distribution characteristic plate and an oil layer CO2 saturability distribution characteristic plate are obtained; through a long thin tube displacement test, the minimum mixed-phase pressure of CO2 and crude oil of the target oil deposit is determined through measurement; and a CO2 injecting and oil deposit displacing CO2 mixed-phase area is judged. The method is clear in step and easy and convenient to apply, and a set of scientific, reasonable and reliable judgment and evaluation criteria is provided for developing research of a low-permeability (compact) oil deposit CO2 injecting and oil displacing mechanism and the CO2 injecting displacement recovery efficiency improvement technique. Whether an oil deposit belongs to mixed-phase displacement or not can be judged, and whether an area to be evaluated in the oil deposit is of the mixed-phase area type or not can also be judged. Meanwhile, the method can guide low-permeability (compact) oil deposit CO2 injecting displacement to carry out corresponding development strategy research. The method has broad application and popularization prospects and remarkable economic and social benefits.

Description

technical field [0001] The present invention relates to CO injection 2 flooding enhanced oil recovery research field, specifically CO injection 2 Reservoir CO flooding 2 Miscible area judgment method. Background technique [0002] In gas flooding projects around the world, CO 2 Miscible flooding accounted for 53.9%, while CO injection in 124 2 Among the oil flooding projects, there are 108 miscible flooding projects. Visible CO 2 Whether it can be miscible with crude oil in the process of oil displacement is a matter of great concern to people, and some people even regard it as CO 2 The key to success or failure. Therefore, in determining CO 2 It is necessary to have a clear understanding of whether it is miscible flooding or not during the oil flooding project. Currently, in CO 2 Generally, the following methods are used to distinguish miscible areas in oil flooding projects: (1) If the formation pressure in the area to be evaluated is greater than the minimum mis...

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Problems solved by technology

It can be seen that the above method only considers the pressure factor, and does not pay attention to whether there is CO in the evaluation area. 2 The second method also ignores the major changes in the formation pressure field and its impact on the miscible state after the gas injection development of the oilfield, so the current judgment method has major flaws

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