- ASME B31.8 defines ‘petroleum’ as: ‘crude oil, condensate, natural gasoline, natural gas liquids, liquefied petroleum gas, and liquid petroleum products.’.
- Petroleum is a range of compounds of hydrogen and carbon.
- Hence, petroleum is known as a ‘hydrocarbon’.
Oil and Gas
- Oil and natural gas are made of hydrocarbon molecules.
- These hydrocarbons range from light gases (e.g., methane), to liquids (e.g., crude oil), to heavy, gummy near-solids.
- The differences in hydrocarbons are due to varying proportions of hydrogen and carbon making up the hydrocarbon molecule:
- natural gas is the simplest hydrocarbon (it is mainly methane, CH4).
Examples of liquid hydrocarbons
Liquid hydrocarbons have more complex structures:
Oil and gas
- Crude oil and natural gas are made up of a variety of ‘hydrocarbons’.
- These hydrocarbons are called:
- paraffins (e.g., methane, CH4);
- aphthenes (e.g., cyclohexane, C6H12); and,
- aromatics (e.g., benzene, C6H6).
- Crude oil is usually a liquid at ambient temperatures.
- Natural gas is usually a gas at ambient temperatures.
Wax and hydrates
- A drop in temperature can create solids in crude oil and natural gas:
- ‘wax’ (solid paraffin) can form in crude oil;
- ‘hydrates’ (a mix of water and methane, in ice form) can form in natural gas.
- These solids can cause problems in pipelines:
- increases pumping requirements;
- can block the pipeline; and,
- lowers pipeline efficiency.
- Reduced throughput means reduced revenue for the pipeline company.