Page 198 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Fluid-rock interactions 181

Figure 8.7 CT images of Mancos shale core under various icps (the CT cut face image at
72 h was reconstructed using the all cross-section images).
From these three tests, the following observations can be made.
(1) Under a lower confining pressure, more fractures were generated dur-
ing the initial water imbibition.
(2) Generated fractures could be closed, reopened, closed and reopened .
In other words, opening or closing of a fracture was dynamic,
depending on the water concentration change rate and stress conditions
(Zhang and Sheng, 2017a; 2017b, 2017c, 2018).
(3) At the end of each test, very few fractures remained open, regardless of
the magnitude of confining pressure, which were also observed earlier
(Zhang and Sheng, 2017a; 2017c).