Crude oil comprises a mixture of thousands of hydrocarbon molecules with 5 to more than 60 carbons. The molecules vary from straight chains, circles, to chains with side chains. Shorter hydrocarbon molecules have low viscosity and vice versa.At surface temperature and pressure, natural gas has a composition of hydrocarbon with one, two, three, and four carbons i.e., (CH4) methane, (C2H6) ethane, (C3H8) propane and (C4H10) butane. Typically natural gas is composed of 88% methane, 5% ethane, 2 percent propane, and 1% butane.