Page 355 - Enhanced Oil Recovery in Shale and Tight Reservoirs

328 Enhanced Oil Recovery in Shale and Tight Reservoirs

Figure 11.17 Oil recovery factor versus pressure gradient from surfactant flooding
sand models.

existence of high-permeability fractures between the injector and the
producer.
For comparison, the oil recovery factor versus pressure gradient for
alkaline flooding from shale and sand models is plotted in Fig. 11.18. The
relationship shows less linearity, indicating that the relationship is more
complex than that in surfactant flooding. In addition to the pressure gradient
effect, wettability alteration plays an important role.
In the above shale models, the fracture permeability is 2000 mD. This
results in such high permeability ratio between the fracture and matrix
that the injected fluid channels through the fracture, and surfactants or
any chemicals added in the injected fluid may not function. To check this

Figure 11.18 Oil recovery factor versus pressure gradient for alkali flooding from shale
and sand models.