Oil is recovered mainly by oil drilling (natural oil sources are scarce). This comes after studies of the structural geology (at the scale of the reservoir), the analysis of the sedimentary basin, the characterization of the reservoir (mainly in terms of the porosity and permeability of the structures of geological reservoirs). It is refined and separated, most easily by distilling, into a large number of consumer products, gasoline (petrol) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Oil is used in the manufacture of a wide variety of materials, and it is estimated that the world consumes about 90 million barrels a day.