Determination of Parameters for Individual Layers by Transient Well Tests in Multilayer Reservoirs

Approximate expressions for the pressure response and flow rates of individual layers are given when a well produces at a constant production rate from an infinite multilayer reservoir either with or without interlayer crossflow. The kh product and skin factor of each layer can be determined by one drawdown test if the common wellbore pressure and the rate of each layer can be measured at the same time. The behavior of the crossflow, caused by skin factors, is discussed. A new method for determining the vertical permeabilities of the shales between layers is developed with the crosspoint of the two straight lines of drawdown or buildup curves. This method avoids measuring the wellbore pressures of the producing interval and the closed interval simultaneously.