Phase Envelopes for reservoir fluids with Asphaltene onset lines: Exploring topology transitions based on compositional changes.

FEDERICO E. BENELLI; PISONI, GERARDO O.; CISMONDI, MARTÌN

Bucaramanga

Conferencia; The 22nd International Conference on Petroleum Phase Behavior and Fouling; 2022

Petrophase

Reservoir fluids may present complex phase diagrams involving three-phase behavior, due to the presence of different compounds that -when exceeding certain quantities- can induce the separation of a second liquid phase. Typical and important cases are carbon dioxide, water and asphaltenes, while the mere asymmetry in the mixture of hydrocarbons can also be responsible for a three-phase region in the fluid phase envelope. Although the behavior and practical implications are quite different in each of these cases, their phase diagrams may share some qualitative characteristics, and therefore require similar methods and strategies for their calculation.A general computation strategy, including details on the calculation method for three-phase envelopes and highlighting the importance of double-saturation points, was presented in Petrophase 2017.1 That work focused on the behavior of asphaltenic reservoir fluids, illustrating three different possible topologies for the complete phase envelope, based on reservoir fluid cases taken from the literature. In this work we study different composition effects on these complex phase diagrams for reservoir fluids, with focus on the transitions between different topologies. New possible topologies have also been identified and considered in the extension of the strategy for computing complete phase envelopes with two and three-phase boundaries. Reference fluids considered in this study consisted again of compositions and parameters taken from the literature, but in simplified lumped versions. Starting from those fluids, different alterations in compositions were used to analyze the effect on the predicted phase diagram. The effects and relations observed could help to advance the understanding of asphaltenes phase behavior in reservoir fluids.