Everything about Heavy Crude totally explained
Heavy crude oil or
Extra Heavy oil is any type of
crude oil which doesn't flow easily. It is referred to as "heavy" because its
density or
specific gravity is higher than of
light crude oil.
Heavy crude oil has been defined as any liquid petroleum with an
API gravity less than 20°,
meaning that its specific gravity is greater than 0.933.
Production, transportation, and refining of
heavy crude oil present special challenges compared to light crude oil. The largest reserves of heavy oil in the world are located north of the
Orinoco river in
Venezuela, the same amount as the
conventional oil reserves of
Saudi Arabia, but 30 or more countries are known to have reserves. Heavy crude oil is closely related to
tar sands, the main difference being that tar sands generally don't flow at all.
Canada has large reserves of tar sands, located north and northeast of
Edmonton,
Alberta.
Physical properties that distinguish heavy crudes from lighter ones include higher
viscosity and
specific gravity, as well as heavier molecular composition. Extra heavy oil from the Orinoco region has a
viscosity of over 10,000
centipoise and 10°
API gravity . Generally a
diluent is added at regular distances in a pipeline carrying heavy crude to facilitate its flow.
Some
petroleum geologists categorize
bitumen from
tar sands as extra heavy oil although bitumen doesn't flow at
ambient conditions.
Economics
Heavy crude oils provide an interesting situation for the economics of petroleum development. The Resources of Heavy oil in the world are more than twice of those conventional light crude oil. On one hand, due to increased
refining costs and high sulfur content, heavy crudes are often priced at a discount to lighter ones. The increased viscosity and density also makes production more difficult (see:
reservoir engineering). On the other hand, large quantities of heavy crudes have been discovered in the Americas including
Canada,
Venezuela and
Northern California. The relatively shallow depth of heavy oil fields (often less than 3000 feet) contributes to lower
drilling costs.
Chemical properties
Heavy oil is
asphaltic. It is "heavy" (dense and viscous) due to the high presence of
naphthenes and
paraffins. Heavy oil has over 60 carbon atoms and hence a high boiling point and molecular weight. For example, the
viscosity of Venezuela's Orinoco extra-heavy crude oil lies in the range 1000-5000
cP, while Canadian extra-heavy crude has a viscosity in the range 5000-10,000 cP, about the same as molasses, and higher (up to 100,000 cP for the most viscous commercially exploitable deposits).
The "heaviness" of heavy oil is primarily the result of a relatively high proportion of a mixed bag of complex, high molecular weight, non-paraffinic compounds and a low proportion of volatile, low molecular weight compounds. Heavy oils typically contain very little paraffin and may or may not contain high levels of asphaltenes.
Environmental impact
As a rule, heavy crudes have a more severe environmental impact than light ones. With more difficult production comes the employment of a variety of
enhanced oil recovery techniques, including steam flooding and tighter well spacing, often as close as one well per acre. Heavy crudes also carry contaminants. For example, Orinoco extra heavy oil contains 3.5%
sulfur as well as
vanadium and
nickel.
(External Link
) Heavy crude oils contain more carbon in relation to hydrogen, thus releasing more carbon dioxide (a
greenhouse gas) per amount of usable energy when burned.
Advanced technologies are mitigating the environmental impact via horizontal wells and increased energy efficiency, but, barrel for barrel, heavy crudes will likely always be more environmentally damaging than light crudes.
Origin
Most geologists agree that crude becomes "heavy" as a result of
biodegradation, in which lighter ends are preferentially consumed by bacterial activity in the reservoir, leaving heavier hydrocarbons behind. This hypothesis leans heavily on the techniques of
petroleum geochemistry.
Further Information
Get more info on 'Heavy Crude'.
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