Method and device for evaluating production proportions of different gases in deep coalbed methane reservoir

A method for evaluating production proportions of different gases in a deep coalbed methane reservoir, comprising following steps:

• obtaining physical property parameters of a target coalbed methane reservoir;
• calculating, after fracturing flowback and before production, a coalbed porosity and a coalbed water saturation at the beginning of production of the target coalbed methane reservoir after the fracturing flowback based on the physical property parameters of the target coalbed methane reservoir;
• calculating an original adsorbed gas reserve, an original free gas reserve, and an original dissolved gas reserve of the target coalbed methane reservoir based on the physical property parameters of the target coalbed methane reservoir, the coalbed porosity, and the coalbed water saturation;
• calculating an average coalbed pressure value of the target coalbed methane reservoir each day based on the original adsorbed gas reserve, the original free gas reserve, and the original dissolved gas reserve of the target coalbed methane reservoir, a cumulative gas production, a cumulative water production, and a cumulative water influx each day, the coalbed porosity and the coalbed water saturation at the beginning of production of the target coalbed methane reservoir after the fracturing flowback, and the physical property parameters;
• calculating a cumulative free gas production, a cumulative adsorbed gas production, and a cumulative dissolved gas production of the target coalbed methane reservoir based on the average coalbed pressure value of the target coalbed methane reservoir each day, the original adsorbed gas reserve, the original free gas reserve, the original dissolved gas reserve, the cumulative gas production, the cumulative water production, and the cumulative water influx each day, the coalbed porosity and the coalbed water saturation at the beginning of production of the target coalbed methane reservoir after the fracturing flowback, and the physical property parameters;
• calculating a daily free gas production, a daily adsorbed gas production, and a daily dissolved gas production of the target coalbed methane reservoir based on the cumulative free gas production, the cumulative adsorbed gas production, and the cumulative dissolved gas production of the target coalbed methane reservoir each day;
• and
• calculating daily production proportions of free gas, adsorbed gas, and dissolved gas in the target coalbed methane reservoir based on the daily free gas production, the daily adsorbed gas production, and the daily dissolved gas production.