Assessment of correlations and simulation software to calculate phase diagrams of pre-salt fluids

Abstract

The presence of heavy n-alkanes , together with CO₂ and water, affects the accuracy of existing correlations used in equations of state. Moreover, they impact the performance of simulation software, resulting in flawed calculations. In this work, the most used correlations for predicting the properties of heavy n-alkanes are analyzed. Calculations were made using commercial software packages for two compositions of pre-salt reservoirs, and considering the Peng-Robinson and the Soave-Redlich-Kowng equations of state. The properties of the estimated C₂₀₊fraction affected the numerical stability, and the calculated PT diagrams are unexpected. The reasons for the observed pitfalls are discussed.

Keywords:

• heavy n-alkanes
• phase diagrams
• pre-salt reservoir

Acknowledgments

The first author would like to acknowledge the National Agency of Petroleum, Natural Gas and Biofuels (ANP – Brazil), and Shell Brazil Ltda., through the Investment in Research, Development and Innovation Clause.