Evaluation of Nondarcy Skin Correlations for Gas Wells in the Trinidad East Coast Marine Area

Abstract

Rate dependent skin is a key factor influencing the deliverability of gas producing wells because of the phenomena of high velocity flow behavior around a limited, near wellbore cross-sectional area. Forchheimer (1901) [1] proposed an additional factor in Darcy’s original equation to account for the pressure drop due to high velocity flux in the porous media, known as "Inertial Resistance Factor (β)", which is now a determinant parameter in the flow modeling of gas wells. Several authors have developed different correlations that account for the inertial forces acting under these producing conditions. Multi-rate and Pressure Transient Analysis (PTA) evaluation was performed on nine (9) gas well tests in the Dolphin Field. The Non-Darcy Flow Coefficient (NDFC) obtained was compared with predicted NDFC’s using 18 Beta (β) correlations, where each correlation has its own assumptions and determinant parameters. Existing correlations do not match the actual NDFC in the field, as a consequence, a new Inertial Resistance Factor Correlation (IRFC) is proposed for assessing the unknown NDFC in the ECMA fields with a minimum percentage error of 17%. The following study will detail the results of a probabilistic approach which uses correlations to provide a better estimate of NDFC in the Dolphin field, with the final objective of reducing uncertainty in forecasting production on recompletions and new wells in East Coast Marine Area fields.