Simulation Study On WAG-CO2 Injection Optimization For Less Asphaltene Precipitation In Light Oil

Flow assurance issues due to asphaltene precipitation in light oil reservoirs during
water-alternating-carbon dioxide gas (WAG-CO2) injection are common. The
possibility of asphaltene precipitation is often neglected during enhanced oil
recovery (EOR) planning phase due to its minute amount in light oils. Another
problem is the lack of prior knowledge on the WAG parameters that could possibly
enhance the asphaltene precipitation during WAG-CO2 injection. Based on the
severity of the problem, this study was initiated with the aim to determine and
suggest the optimum WAG parameters, namely WAG injection rate, WAG injection
pressure, WAG cycle sizes, WAG ratio and injected water salinity for lesser
asphaltene precipitation. A compositional model was built using compositional
simulator for the purpose of this study. The impacts of each WAG parameter were
determined by varying the parameters one at a time while keeping others constant in
the simulation runs. The results revealed the parameter with profound effects is only
the injection pressure. The higher the injection pressure, the lesser the amount of
asphaltene precipitated and deposited. WAG ratio of 2:1 gives better oil recovery and
lesser asphaltene precipitation due to waterblocking effect. Other parameters have a
slight effect or no effect at all on the asphaltene precipitation. Based on this study, it
can be deduced that manipulating the injection pressure and WAG ratio will control
the amount of asphaltene precipitated and deposited. The outcomes of this study will
benefit the operators adopting WAG-CO2 method in light oil fields through better
management of flow assurance problems caused by asphaltene precipitation.