Application of the layered stabilized flow model to estimate the original gas in place of multi-layered commingled gas reservoirs

Abstract

The purpose of this report is to investigate the applicability of the Layered Stabilized Flow Model (LSFM). Proposed by El-Banbi and Wattenbarger in 1996, the approach combines the material balance equation and the productivity index equation to estimate the original gas in place (OGIP) of the individual layers comprising a commingled gas reservoir. The LSFM basically calculates a “model production rate” for each layer and sums up these layer rates to calculate the “total model production rate” for the commingled reservoir. This total model production rate is then compare to an actual production rate data and the difference between the two is minimized through non-linear regression analysis. The method is simple and requires only the flow rate and the flowing bottomhole pressure history together with the initial reservoir pressure and gas properties. The method shows excellent results for moderate to high permeability reservoirs even with long shut-ins and considerable variations in the flowing bottomhole pressures. Five cases were analyzed using the technique. Comparison with other estimation methods was done verify the performance of the model.