Combined Investigations of Fluid Phase Equilibria and Fluid-Solid Phase Equilibria in Complex CO2-Crude Oil Systems under High Pressure

摘要

An efficient strategy for developing a petroleum reservoir as well as designing a robust production system depends on the knowledge of the phase behavior of the fluids to be produced. Enhanced oil recovery projects, such as CO2 flooding, are even more critical as their efficiency is strictly related to the fluid's phase behavior in response to the added gas. Nevertheless, studies able to assess the complete phase behavior diagram for CO2-crude oil mixtures are scarce. Among the main reasons, one can point out the unavailability of an experimental method able to investigate such complex systems. To overcome such a challenge, the development of an experimental setup able to determine fluid phase transitions and heavy organic solids formation in opaque oils in reservoir conditions is presented. The use of a new visualization system in combination with a recently developed acoustic wave sensor offers full external scrutiny of fluid samples under high-pressure conditions. The use of a charge coupled device that works in the short wavelength infrared range allows a direct observation of the transformations occurring in the system while the external parameters are changed. It reduces the study of dark oil to the convenient investigation of transparent fluids. The study of three different CO2-crude oil systems demonstrates that by taking advantage of the complementarity of the QCR setup and opaque visibility setup, it is possible to investigate the full phase diagram of dark oil systems.