“…The fluid‐fluid displacement in rough‐walled rock fractures, on the other hand, has also been a topic of extensive research. Most research efforts were dedicated to the fluid occupancy and invasion morphology of one phase displacement by another [ Fernández et al ., ; Amundsen et al ., ; Glass et al ., ; Neuweiler et al ., ; Bergslien and Fountain , ; Karpyn et al ., ; Haugen et al ., ; Babadagli et al ., ], and the flow patterns/structures during the simultaneous flow of two fluids and the macroscopic hydraulic properties [ Frette et al ., ; Fourar and Bories , ; Persoff and Pruess , ; Liu et al ., ; Detwiler et al ., ; Chen and Horne , ; Detwiler , ; Alturki et al ., ; Yang et al ., ; Babadagli et al ., ; Ye et al ., ]. Fourar and Bories [] and Fourar et al .…”