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Hydrates: Hydrocarbons

Petroeum

  • 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.

Oil barrel pouring oil

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.
Wax
Wax
Hydrates
Hydrates

Pipelines

  • 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.
Hydrates being removed from a gas pipeline.
Hydrates being removed from a gas pipeline.
This class will now focus on hydrate formation. See our bitesize class on ‘Wax’ if you want a quick introduction to this solid.

 

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