Page 345 - Enhanced Oil Recovery in Shale and Tight Reservoirs

318 Enhanced Oil Recovery in Shale and Tight Reservoirs

Figure 11.9 Oil saturation at 0.4 days (A) and 9 days (B) in the case of surfactant injec-
tion only (sand rock).

in the matrix, especially near the producer. In the sand rock, the perme-
ability is not low, so that surfactant solution can partially enter the matrix
instead of breaking through the fracture only.
For further comparison, the oil saturations at 0.4 and 9 days for the case
of alkali injection only in the shale rock are shown in Figs. 11.10A, 11.10B,
respectively. It can be seen the saturation changes significantly in the matrix
from 0.4 to 9 days. More interesting, the oil saturations by 9 days at the two