Oil and gas production handbook An introduction to oil and gas production

Figure 18. LNG terminal process overview 
 
At the receiving 
terminal, LNG is 
stored in local 
cryogenic tanks. It is 
regasified to ambient 
temperature on 
demand, commonly in 
a sea water heat 
exchanger, and then 
injected into the gas 
pipeline system. 
Cove point LNG terminal 
 
LNG ship
LNG discharge 
line
Gas return line
Compressor
LNG tank
Recondenser
Vaporizer
Gas 
pipelines
Sea water
T ambient
(10°C ÷ 25°C)
Discharge sea water
(5°C ÷ 20°C)

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77 
 
6 Refining 
Up to the early 1970s, crude oil prices were kept reasonably stable by major 
international oil companies and industrialized nations. Less value was 
created in the upstream production operations and relatively more profits 
were generated in refining and distribution operations. With the 1973 oil 
crisis and rising crude oil prices, more of the value was created upstream.  
 
Now, the success of a modern refinery depends more on economies of scale 
and the ability to process a wide range of crudes into the maximum quantity 
of high value fuels and feedstock. A refinery that is able to handle multiple 
types from heavy to light crude is said to have to have a large swing.  Trade 
specifications such as ”West Texas Intermediate” (WTI) API 38.3°, “Brent 
Blend” API 38.3°, “Heavy Arab Crude” API 27.7° or “Grane” API 18.7° are 
examples of such crudes. 
 
Medium light crudes can be used directly in early engines and burners. 
Modern consumers, such as gas and diesel engines, aviation turbojet 
engines and ship bunkers need fuels manufactured to precise specifications. 
This includes removing contaminants and pollutants, such as sulfur. 
6.1 Fractional distillation 
The basic refinery uses fractional distillation. Incoming crude is heated to its 
boiling point. It then enters the distillation column, which separates the 
different fractions. The column is of the reflux type, where colder condensed 
fluids running down are reheated by rising vapors that in turn condense. This 
produces clear thermal zones where the different products can be drained. 
 
NOTE: The schematic on the following page is simplified. Both continuous 
and vacuum distillation is used in separate columns to avoid heating the raw 
crude to more than 370 °C. Overheating would cause thermal cracking and 
excessive coke that may also plug pipes and vessels. Also a sidecut stripper 
is used, in addition to the main column, to further improve separation. 
Sidecut is another name for the fractions emerging from the side (rather than 
top and bottom) of the main column, i.e., naphtha, gasoline, kerosene and 
diesel. 
  
The fractions are a mix of alkanes and aromatics and other hydrocarbons, so 
there is not a linear and uniformly rising relationship between carbon number 
and boiling point and density, although there is a rough fit. Even so, this 
means that each fraction contains a distribution of carbon numbers and 
hydrocarbons. 

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78 
 
6.2 Basic products 
The basic products from fractional distillation are: