In SPE 133615, Nobakht et al.  introduced a simplified method of production forecasting for tight/shale gas wells which exhibit extended periods of linear flow. The method is simple as it relies principally on a plot of inverse rate versus square root time. In the present work, we extend this method by applying a material balance constraint that allows for changing reservoir pressure with depletion. We generate curves for a type well. These curves are normalized on the basis of the initial rate of the well. This work shows that wells from similar producing areas will all fit on the same "type curve".
The advantages of this forecasting method are: (1) It requires only the initial rate and an estimate of Original Gas in Place (OGIP), (2) The cumulative gas production can be calculated at any given time without the need to time-step forward and (3) it can be used as a field development planning tool, when combined with the economics of multistage hydraulic fracturing.