Although thermal methods have been popular and successfully applied in heavy oil recovery,they are often found to be uneconomic or impractical. Therefore,alternative production protocols are being actively pursued and an interesting option is water and/or polymer flooding. Such a technique has been successfully tested in laboratory investigations,where oil recovery was found to be much higher than expected(paper SCA2011-18). Moreover,in some of the core scale experiments reported using 2D slabs of Bentheimer sandstone,X-ray scans performed during the flooding sequence provided evidence of an interesting new phenomenon – post breakthrough,highly dendritic water fingers were seen to thicken and coalesce,forming braided water channels and improving sweep efficiency. However,the causes of this behaviour are not clearly understood and the mechanisms governing such displacements consequently require further investigation. To this end,we describe a new fully dynamic network model that has been developed to investigate finger thickening during water flooding of extra-heavy oils. The displacement physics has been implemented at the pore scale and,following a successful benchmarking exercise against numerous micromodel experiments,a range of slab-scale(30cm x 30cm)simulations has been carried out and compared with the corresponding experimental observations. We show that the model is able to replicate finger architectures similar to those observed in the experiments and go on to reproduce and interpret,for the first time to our knowledge,finger thickening following water breakthrough. Finally,we examine the impact of several parameters – core length,wettability and injection rate – on the finger swelling phenomenon. Keywords: viscous fingering,finger thickening,heavy oil,recovery,non-thermal,immiscible displacement
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