Abstract Many operators of tight gas reservoir fields are interested in determining the infill well potential in these fields. Over drilling may prove to be uneconomical; whereas, under drilling would leave unexplored reserves in the ground. In predicting EUR of a potential in fill well, the operator is interested in knowing what percentage of the production will be from incremental reserves (newly accessed) vs. acceleration reserves (which can be produced from existing wells). Higher the percentage of incremental reserves better is the potential of an in fill well. In this paper, we present a novel method for determining the incremental vs. acceleration potential for in fill well in a tight gas reservoir. We evaluate the existing wells by plotting the data in a form so that the data can be linearly extrapolated. We predict the EUR for individual wells before and after new wells in the vicinity are drilled. By knowing how much gas is "diverted" from the older wells, we determine the acceleration component of an in fill well. By repeating the process as the field is being developed, we can determine the fraction of acceleration and incremental components of the EUR at each stage of infill drilling. We will also know how the EUR is changing as the well spacing is slowly reduced. To ensure our results are reasonable, we also compare our EUR values with EUR’s reported by the operator as proved reserves. Armed with this information, we can extrapolate in fill well potential for a smaller spacing, including the contribution due to acceleration vs. incremental production. We developed this procedure for Wamsutter field in Wyoming. Using the procedure, we recommended in fill well locations to the operator. The comparison between actual data and the predicted results will be presented.