In crude oil we will find various hydrocarbon ‘constructions’

Most of the substances in crude oil and oil products are so called hydrocarbons. 

Molecules of those substances are built from two basic chemical elements: carbon and hydrogen atoms, however other elements such as sulphur and nitrogen compounds are also available, albeit in much smaller quantities.

In crude oil we will find hydrocarbon constructions

In crude oil we will find hydrocarbon ‘constructions’ like the group called the paraffins or alkanes (linear or branched hydrocarbon structures), naphthenes or cycloalkanes (cyclic structure) and aromatics (double bonds cyclic structure). 

After a high temperature thermal cracking process a new hydrocarbon group is produced

After a high temperature thermal cracking process a new hydrocarbon group, called olefins or alkenes (paraffins or naphthene structures but with (a) double carbon-carbon bond(s), are produced. The double bond(s) so produced are unfortunately weaker than a single bond. The double bond(s) will make this olefin chemically unstable and can react relatively easy with other compounds or elements, reducing the long term storage stability.