When petroleum companies abandon an oil well, more than half
the reservoir’s oil is usually left behind as too difficult to recover. Now,
however, much of the residual oil can be recovered with the help of
nanoparticles and a simple law of physics.
Oil to be recovered is confined in tiny pores within rock,
often sandstone. Often the natural pressure in a reservoir is so high that the
oil flows upwards when drilling reaches the rocks containing the oil.