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

BENELLI, FEDERICO; PISONI, GERARDO O.; CISMONDI, MARTÍN

Bucaramanga

Congreso; PetroPhase 2022 (The 22nd International Conference on Petroleum Phase Behavior and Fouling); 2022

Unired y Ecopetrol

Reservoir fluids may present complex phase diagrams involving three-phase behavior,due to the presence of different compounds that -when exceeding certain quantities- caninduce the separation of a second liquid phase. Typical and important cases are carbondioxide, water and asphaltenes, while the mere asymmetry in the mixture of hydrocarbonscan also be responsible for a three-phase region in the fluid phase envelope. Althoughthe behavior and practical implications are quite different in each of these cases, theirphase diagrams may share some qualitative characteristics, and therefore require similarmethods and strategies for their calculation.A general computation strategy, including details on the calculation method forthree-phase envelopes and highlighting the importance of double-saturation points,was presented in Petrophase 2017.1 That work focused on the behavior of asphaltenicreservoir fluids, illustrating three different possible topologies for the complete phaseenvelope, based on reservoir fluid cases taken from the literature.In this work we study different composition effects on these complex phase diagrams forreservoir fluids, with focus on the transitions between different topologies. New possibletopologies have also been identified and considered in the extension of the strategy forcomputing complete phase envelopes with two and three-phase boundaries. Referencefluids considered in this study consisted again of compositions and parameters takenfrom the literature, but in simplified lumped versions. Starting from those fluids, differentalterations in compositions were used to analyze the effect on the predicted phasediagram. The effects and relations observed could help to advance the understanding ofasphaltenes phase behavior in reservoir fluids.(1) Cismondi, M. Phase envelopes for reservoir fluids with asphaltene onset lines: Anintegral computation strategy for complex combinations of two and three-phasebehavior. Energy & Fuels, 2018, 32, 2742-2748.