Experimental Study on the Distribution of Retained Fracturing Fluids and Its Effect on the Permeability and Wettability in Tight Oil Reservoirs

Figure 4

Photographic images for the stereoscopic microscope of different stages of core slice A-1.

(a) Original sample

(b) Saturated water sample

(c) Oil displacement water

(d) Water drive oil

(e) Oil reverse displacement water