  Oil spills have posed a serious threat to our marine and ecological
environment in recent times. Containment of spills proliferating via small
drops merging with oceans/seas is especially difficult since their mitigation
is closely linked to the coalescence dependent spreading. This
inter-connectivity and its dependence on the physical properties of the drop
has not been explored until now. Furthermore, pinch-off behavior and scaling
laws for such three-phase systems have not been reported. To this end, we
investigate the problem of gentle deposition of a single drop of oil on a pool
of water, representative of an oil spill scenario. Methodical study of 11
different n-alkanes, polymers and hydrocarbons with varying viscosity and
initial spreading coefficients is conducted. Regime map, scaling laws for
deformation features and spreading behavior are established. The existence of a
previously undocumented regime of delayed coalescence is revealed. It is seen
that the inertia-visco-capillary (I-V-C) scale collapses all experimental drop
deformation data on a single line while the early stage spreading is found to
be either oscillatory or asymptotically reaching a constant value, depending on
the viscosity of the oil drop unlike the well reported monotonic, power law
late-time spreading behavior. These findings are equally applicable to
applications like emulsions and enhanced oil recovery.
