Fig. 2.

Number-based (A) and volume-based (B) cluster size distribution after the four injection steps shown in Fig. 1. Note the large oil clusters with volumes above 10¹⁰ μm³ that existed after the drainage steps. The red curve shows the pore size distribution of this rock extracted from the µCT image of the dry rock using a sphere fitting method (51). A continuous increase in number of clusters along with decrease in the cluster volumes indicates the change in oil structure during the drainage and imbibition processes.