Method for determining CO2 injection starting time in CO2 displacement CH4 process

The invention relates to a CO2 injection starting time determination method in a CO2 displacement CH4 process. The CO2 injection starting time determination method comprises the following steps: constructing a geological model required by CO2 displacement CH4 numerical simulation and carrying out grid division; on the basis of the required geologic model after grid division, a CO2 flooding CH4 numerical simulation multi-field multi-phase mathematical model is constructed; numerical simulation is conducted in the multi-field multi-phase mathematical model, and the CO2 injection amount and the CH4 exploitation amount corresponding to different CO2 starting time are obtained; performing linear analysis on the CO2 injection amount and the CH4 exploitation amount corresponding to different CO2 starting time; and determining the starting time of CO2 injection in a specific gas injection period. 本发明涉及一种CO2驱替CH4过程中注CO2起始时间确定方法，其所述方法包括：CO2驱CH4数值模拟所需地质模型的构建及网格划分；基于网格划分后的所需地质模型，构建所述CO2驱CH4数值模拟多场多相数学模型；在所述多场多相数学模型中进行数值模拟