Title page for ETD etd-07132005-091607

Type of Document Dissertation
Author Ayirala, Subhash C.
Author's Email Address sayira1@lsu.edu
URN etd-07132005-091607
Title Measurement and Modeling of Fluid-Fluid Miscibility in Multicomponent Hydrocarbon Systems
Degree Doctor of Philosophy (Ph.D.)
Department Petroleum Engineering
Advisory Committee
Advisor Name Title
Dandina N. Rao Committee Chair
Anuj Gupta Committee Member
Edward B. Overton Committee Member
Karsten E. Thompson Committee Member
Donald Dean Adrian Dean's Representative
  • improved oil recovery
  • gas injection
  • compositional effects
  • vanishing interfacial tension technique
  • interfacial tension
  • miscibility
  • solubility
Date of Defense 2005-06-23
Availability unrestricted
Carbon dioxide injection has currently become a major gas injection process for improved oil recovery. Laboratory evaluations of gas-oil miscibility conditions play an important role in process design and economic success of field miscible gas injection projects. Hence, this study involves the measurement and modeling of fluid-fluid miscibility in multicomponent hydrocarbon systems. A promising new vanishing interfacial tension (VIT) experimental technique has been further explored to determine fluid-fluid miscibility. Interfacial tension measurements have been carried out in three different fluid systems of known phase behavior characteristics using pendent drop shape analysis and capillary rise techniques. The quantities of fluids in the feed mixture have been varied during the experiments to investigate the compositional dependence of fluid-fluid miscibility.

The miscibility conditions determined from the VIT technique agreed well with the reported miscibilities for all the three standard fluid systems used. This confirmed the sound conceptual basis of VIT technique for accurate, quick and cost-effective determination of fluid-fluid miscibility. As the fluid phases approached equilibrium, interfacial tension was unaffected by gas-oil ratio in the feed, indicating the compositional path independence of miscibility. Interfacial tension was found to correlate well with solubility in multicomponent hydrocarbon systems. The experiments as well as the use of existing computational models (equations of state and Parachor) indicated the importance of counter-directional mass transfer effects (combined vaporizing and condensing mass transfer mechanims) in fluid-fluid miscibility determination.

A new mechanistic Parachor model has been developed to model dynamic gas-oil miscibility and to determine the governing mass transfer mechanism responsible for miscibility development in multicomponent hydrocarbon systems. The proposed model has been validated to predict dynamic gas-oil miscibility in several crude oil-gas systems. This study has related various types of developed miscibility in gas injection field projects with gas-oil interfacial tension and identified the multitude of roles played by interfacial tension in fluid-fluid phase equilibria. Thus, the significant contributions of this study are further validation of a new measurement technique and development of a new computational model for gas-oil interfacial tension and miscibility determination, both of which will have an impact in the optimization of field miscible gas injection projects.

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