A method for controlling driving fluid breakthrough caused by zones of pressure communication, i.e., a matrix bypass event (“MBE”) or a wormhole, having a void space and possibly areas of enhanced permeability (a halo region) associated with the void space, within a subterranean formation arising from use of a driving fluid in reservoirs where heavy/viscous oil is being produced. In embodiments, the method includes injection of a slurry of a cementitious material into the zone, which upon setting, provides a cement plug in the void space that reduces the pressure communication and flow of driving fluid within the zone. Another step injects a gel precursor within the zone, which upon setting, produces a gel plug that also reduces pressure communication and driving fluid flow through the halo region of the zone.