DefinePK

Abstract

The estimation of water influx from a surrounding aquifer into a Coalbed Methane (CBM) reservoir is a key parameter in an appropriate reservoir characterization activity since the degree of connection between natural fractures with other reservoir units has an economic impact. The solution of the traditional diffusivity equation for water influx cases has been somehow extended to CBM reservoirs so several ways of estimation the aquifer leakage factor has been introduced; including type-curve matching which involves trial-and-error processes. In this work, three expressions for the estimation of the aquifer leakage factor of CBM reservoirs are introduced using transient pressure analysis by reading characteristic featured taken from the pressure, pressure derivative and second pressure derivative versus time log-log plot. These equations were successfully tested with synthetic examples obtaining absolute deviation errors, in the worst scenario, lower than 10% which is very good for a parameter with such very small values. However, the best results provided errors lower than 1%.