Characterizing the Role of Shale Geometry and Connate Water Saturation on Performance of Polymer Flooding in Heavy Oil Reservoirs: Experimental Observations and Numerical Simulations |
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Authors: | Saber Mohammadi Mohsen Masihi Mohammad Hossein Ghazanfari |
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Institution: | 1.Department of Chemical and Petroleum Engineering,Sharif University of Technology,Tehran,Iran |
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Abstract: | Many heavy oil reservoirs contain discontinuous shales which act as barriers or baffles to flow. However, there is a lack
of fundamental understanding about how the shale geometrical characteristics affect the reservoir performance, especially
during polymer flooding of heavy oils. In this study, a series of polymer injection processes have been performed on five-spot
glass micromodels with different shale geometrical characteristics that are initially saturated with the heavy oil. The available
geological characteristics from one of the Iranian oilfields were considered for the construction of the flow patterns by
using a controlled-laser technology. Oil recoveries as a function of pore volumes of injected fluid were determined from analysis
of continuously recorded images during the experiments. We observed a clear bypassing of displacing fluid which results in
premature breakthrough of injected fluid due to the shale streaks. Moreover, the results showed a decrease of oil recovery
when shales’ orientation, length, spacing, distance of the shale from production well, and density of shales increased. In
contrast, an increase of shale discontinuity or distance of the shale streak from the injection well increased oil recovery.
The obtained experimental data have also been used for developing and validating a numerical model where good matching performance
has been observed between our experimental observations and simulation results. Finally, the role of connate water saturation
during polymer flooding in systems containing flow barriers has been illustrated using pore level visualizations. The microscopic
observations confirmed that besides the effect of shale streaks as heterogeneity in porous medium, when connate water is present,
the trapped water demonstrates another source of disturbance and causes additional perturbations to the displacement interface
leading to more irregular fingering patterns especially behind the shale streaks and also causes a reduction of ultimate oil
recovery. This study reveals the application of glass micromodel experiments for studying the effects of barriers on oil recovery
and flow patterns during EOR processes and also may provide a set of benchmark data for recovery of oil by immiscible polymer
flood around discontinuous shales. |
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