Author/Authors :
Zolfaghari، H. نويسنده Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran Zolfaghari, H. , Zebarjadi، A. نويسنده Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran Zebarjadi, A. , Shahrokhi، O. نويسنده Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh, Scotland Shahrokhi, O. , Ghazanfari، Mohammad Hosein نويسنده Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran Ghazanfari, Mohammad Hosein
Abstract :
Several studies have shown that oil recovery significantly increases by low salinity water flooding
(LSWF) in sandstones. However, the mechanism of oil recovery improvement is still controversial.
CO2 that develops buffer in the presence of water is expected as a deterrent factor in LSWF efficiency
based on the mechanism of interfacial tension reduction due to pH uprising. No bright evidence in
literature supports this idea. Herein, a set of core floods including a pair of CO2 water alternating gas
(WAG) and a pair of water injection tests were conducted and the efficiency of LSWF and high
salinity water flooding (HSWF) was compared for each pair. HSWF was followed by LSWF in
tertiary mode. The results showed that not only did not CO2 deteriorate LSWF recovery efficiency, it
improved recovery, because CO2-low salinity WAG showed the best performance among the other
types at a constant pore volume injected. The positive results in both secondary and tertiary modes
with Kaolinite free samples used herein showed that Kaolinite release was not the critical
phenomenon in LSWF brisk performance. In addition, different pressure behaviors of CO2 WAG
processes in comparison with the reported behavior of LSWF proves that LSWF performance may not
depend on how pressure changes through flooding.
