Page 97 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

Estimates of undiscovered conventional and unconventional sources vary as
widely the oil price among different sources. The figure illustrates that if one
assumes that an oil price of 50 USD per barrel prevails, the estimated
economically recoverable reserves with current technology will be about 550
Billion tons of oil equivalent, or 4 Trillion barrels, while an oil price of 100
USD/bl will permit about 800 Billion tons corresponding to more than 5,5
trillion barrels or about 140 years of consumption at current rates.

Economical production cost and discovery are uncertain factors. With
continued high oil prices, figures of around 1-2 trillion barrels of conventional
(more gas than oil) and 3 trillion barrels unconventional are often quoted, for
a total remaining producible hydrocarbon reserve of about 5 trillion barrels of
oil. It is expected that up to a third of oil fuel production may come from
unconventional sources within the next decade.

7.1.1 Extra heavy crude
Very heavy crude are hydrocarbons with an API grade of about 15 or below.
The most extreme heavy crude currently extracted is Venezuelan 8 API
crude e.g. in eastern Venezuela (Orinoco basin). If the reservoir temperature
is high enough, the crude will flow from the reservoir. In other areas, such as
Canada, the reservoir temperature is lower, and steam injection must be
used to stimulate flow from the formation.

When reaching the surface, the crude must be mixed with diluents (often
LPGs) to allow it to flow in pipelines. The crude must be upgraded in a
processing plant to make lighter SynCrude with a higher yield of high value
fuels. Typical SynCrude has an API of 26-30. The diluents are recycled by
separating them out and piping them back to the wellhead site. The crude
undergoes several stages of hydrocracking and coking to form lighter
hydrocarbons and remove coke. It is often rich in sulfur (sour crude) which
must be removed.

7.1.2 Tar sands
Tar sands can be often strip-mined. Typically two tons of tar sand will yield
one barrel of oil. Typical tar sand contains sand grains with a water
envelope, covered by a bitumen film that may contain 70% oil. Various fine
particles can be suspended in the water and bitumen.

This type of tar sand can be processed with water extraction. Hot water is
added to the sand, and the resulting slurry is piped to the extraction plant
where it is agitated and the oil skimmed from the top. Provided that the water

95