Gas reservoir decline-curve analysis using type curves with real gas pseudopressure and normalized time

A normalized time has been developed that linearizes the rate decline vs. normalized time for a gas reservoir producing against constant wellbore pressure during (external) boundary-dominated flow. This allows type-curve matching of the exponential decline curve for a reservoir with any shape. Values of G, k_gh, and k_g/φ can be determined from this type-curve match. It was determined that gas reservoir depletion plotted vs. actual time does not match exponential, harmonic, or hyperbolic decline curves, and future performance can lead to overestimates of reserves and future rate.