Inflow performance relationship in two-phase CBM wells

Abstract：Based on the kinematic and continuing equations of the steady fluid flow, an approach was proposed to predict inflow performance relationship （IPR） for two-phase （gas and water） coalbed methane （CBM） wells. And the mathematical model of two-phase flow and IPR were developed. The function of pseudopressure was used to study the productivity equation for twophase CBM wells. The results show that the small errors of less than 8 % between the prediction and measured values are achieved due to the permeability, skin factor and non-Darcy flow. CBM productivity increases from 0.1 kg/s up to 0.6 kg/s when bottom hole pressures （BHPs） are from 5.0 MPa to 2.1 MPa. Adjusting BHP can effectively increase producing pres- sure drop, which is beneficial to gas desorption and water flow and enhance CBM production. The IPR curves move towards the right direction due to the increased permeability and de- creased skin factor. An enhanced permeability from 2 X 10 3 μm2 up to 2 X 10.2 μm2 leads to the enhanced production of gas and water from 0. 205 kg/s to 1.2 kg/s. During the pumpingproduction, the effective permeability of water decreases while the effective permeability of CBM and supply boundary increase, which makes the IPR curve move towards the left direc- tion.