Unconventional shale gas reservoirs have become a very important part of the resource base throughout the world, but especially in the United States. Production data analysis techniques using various forms of material balance time originally put forth by Palacio and Blasingame (1993) have been proposed and validated in recent publications for a variety of problems (including shale gas and coalbed methane systems) using an adjusted system compressibility function similar to that proposed by Bumb and McKee (1988) to account for adsorbed gas. These modified material balance solutions allow for "type curves" (rate or pressure solutions) to be used in a conventional analysis manner.
The significant challenge in the application of production data analysis for shale gas systems is to determine what the parameter values (analysis results) represent within the context of the inherent complexity of these systems. In this work we propose a slight (but substantive) modification to material balance time and apply the technique to synthetic and field data to assess the capability of this approach for the analysis of production data from gas shales. The formulation we use is that of Cox, et al. (2002) which provides a means for evaluation production data as an equivalent "well test", where we are able to observe characteristic flow regimes in the data and constrain several of the key parameters of interests in shale gas systems. While the field results are difficult to corroborate, the relative magnitudes of the parameters we obtained appear to be reasonable.