Production data analysis of coalbed methane wells to estimate the time required to reach to peak of gas production

•Production data are treated and analysed for CBM wells.•The signatures for time of peak gas production are identified.•The signatures obtained for constant and variable bottom-hole pressure constrains.•The time of peak production is estimated for simulation and field examples.•The estimation accuracy depends on production data quality and fitted functions.

For coalbed methane (CBM) wells with rising gas production, the time required to reach to peak of gas production and the peak gas rate are two fundamental features of production profile. This paper investigates the time of occurrence of peak of production using production data analysis (PDA). The methodology is simple and requires gas rates and flowing bottom-hole pressures (BHP). The derivative of square of BHP over gas rate at standard condition with respect to time is calculated for observed production data. Then using the methodology in the current work, signatures for time of peak production are identified. The signatures of peak time are obtained for constant and variable bottom-hole pressure operational constrains. The contribution of this method is to use the production data to estimate the time of peak production. Field and simulation production data are analysed to illustrate both signatures and estimations of time of peak production. The accuracy of estimation depends on the quality of production data and the goodness of the fitted functions used in this approach. This method provided satisfactory estimations for time of peak production for field and simulated cases presented in this paper. The current analysis may contribute to production forecasting for the negative decline portion of production profile.