Applying a Time-Dependent Darcy Equation for Decline Analysis for Wells of Varying Reservoir Type

Abstract

Abstract Decline analysis has been widely applied for predicting hydrocarbon reserves. The approach developed by Arps in 1944 not only is still being used but has also served as the basis for which others developed different approaches. However, with modern day computing facilities the analysis can be conducted beyond the process of identifying lines and curves on semi-log/log-log paper as proposed by Arps or matching the history to the type curves as proposed by other authors. A time-dependent Darcy equation allows for analyzing rate-time decline taking into account the reservoir properties that are unique to the well yet vary with pressure/time. Therefore, it can be used to adequately match the slope of the decline curve that is also changing with pressure/time for the same reasons. The time-dependent Darcy equation also allows for generalizing the decline behavior that is unique to a particular geographical region or reservoir type. In turn, this improves the quality of the analysis, particularly, in a situation where only limited production history is available. Rocky mountain field examples are provided to illustrate the simplicity and the effectiveness of the approach.