Marginal economics underscores the importance for accurate estimation of production profile and expected ultimate recovery or EUR in unconventional resources. While the Arps family of type-curves and the stretched-exponential model appears to yield reasonable estimation of EURs, all insufficiently explain the intrinsic behavior of unconventional reservoirs. This study introduces and applies a new semianalytical approach for estimating production profile and EUR, validated by numerical simulations and verified by field data for unconventional gas and oil reservoirs.
We obtained analytical solutions by considering concentric compressibility elements, analogous to electrical capacitors, in series using the continuity equation to obtain production from conceptual geobodies. This configuration mimics decreasing contributions from a series of concentric reservoir segments into the well with increasing distance from the stimulated-reservoir volume or SRV. The analytical formulation captures production behavior of early-time and SRV-dominated flow patterns, leading to good estimation of expected-ultimare recovery or EUR.