C02 extraction for crude oil and its effect on crude oil viscosity

Key words:  C02 flooding  extractibility  crude oil viscosity  phase state

Abstract:

With high-pressure PVT ( pressure-volume-temperature) experimental device, extraction experiments were conducted using three different crude oil samples，and the contact process of C02 and crude oil in immiscible flooding was simulated in PVT container. The ability of C02 extraction for crude oil and the properties of residual oil after C02 extraction were studied. The volume fraction of light components entering the gas phase, viscosity and composition of residual oil in the process of extraction were measured. The experimental results show that the light components of crude oil are preferentially extracted by C02，and the lighter the crude oil，the bigger the extraction volume. After extraction the residual oil viscosity increases and is 1.1 - 2. 0 times of the crude oil viscosity. The lower the temperature，the bigger the viscosity ratio. The difference between oil and gas can be minimized by increasing injection pressure or decreasing C02 injection volume. The extraction has an important impact on heavy oil viscosity，and results in more difficult to recover the residual oil. It is recommended that C02 flooding technology should be applied priority to the light oil reservoirs.