Abstract
In this paper, a rigorous approach is reported for the grouping of the C7+ fraction via the gamma distribution of Whitson to create pseudo-components. The parameters of the gamma distribution were chosen to optimally match the molecular weight distribution of the original heavy end so that a representative simplification was possible. The Peng-Robinson Equation of State (EoS) was fitted to the derived pseudo-component properties and Binary Interaction Parameters (BIPs) for thermodynamic consistency. The approach was applied to a test reservoir fluid from a Kazakhstani oil field, and phase behavior was simulated for the lumped and detailed composition. The results confirmed considerable consistency in the predicted phase envelopes to demonstrate that the grouping method preserved key fluid properties. This integration of Whitson-based lumping with EoS adjustment provided sound justification for delumping and phase behavior modeling in compositional simulations as well as surface facility design.