ORIGIN AND OCCURRENCE OF OIL 57
more viscous crude oils in amounts up to several thousand parts
per million, and can have serious consequences during processing
of these feedstocks. Because petroleum is a mixture of widely varying constituents and proportions, its physical properties also vary
widely and the color varies from near colorless to black.
At the time of writing, world crude oil reserves are on the order
of 1.3 trillion barrels (1.3 x 10
12
barrels) of which the United States
has 28.4 billion barrels (28.4 x 10
9
barrels), or 2.1% of the total world
reserves (BP, 2010).
In the crude state petroleum has minimal value, but when refined
it provides high-value liquid fuels, solvents, lubricants, and many
other products. Crude petroleum can be separated into a variety of
different generic fractions by distillation. And, the terminology of
these fractions has been bound by utility and often bears little relationship to composition.
The United States imports approximately 65% of its daily crude
oil and crude oil product requirements. As recent events have
shown, there seems to be little direction in terms of stability of supply or any measure of self-sufficiency in liquid fuels precursors,
other than resorting to military action. This is particularly important for the United States refineries because a disruption in supply
could cause major shortfalls in feedstock availability.
In keeping with the preferential use of lighter crude oil as well as
the maturation effect in the reservoir, crude oil currently available to
the refinery is somewhat different in composition and properties to
those available approximately 50 years ago (Swain, 1991,1993,1997,
2000). The current crude oils are somewhat heavier insofar as they
have higher proportions of non-volatile (asphaltic) constituents. In
fact, by the standards of yesteryear, many of the crude oils in use
would have been classified as heavy feedstocks, bearing in mind
that they may not approach the definitions used today for heavy
crude oil. Changes in feedstock character, such as this tendency to
heavier materials, require adjustments to refinery operations to handle these heavier crude oils to reduce the amount of coke formed
during processing and to balance the overall product slate.
2.6.2 Natural Gas
Natural gas is the gaseous mixture associated with petroleum
reservoirs and is predominantly methane, but does contain other
combustible hydrocarbon compounds as well as non-hydrocarbon compounds (Chapter 1) (Speight, 1993; Mokhatab et al, 2006;
more viscous crude oils in amounts up to several thousand parts
per million, and can have serious consequences during processing
of these feedstocks. Because petroleum is a mixture of widely varying constituents and proportions, its physical properties also vary
widely and the color varies from near colorless to black.
At the time of writing, world crude oil reserves are on the order
of 1.3 trillion barrels (1.3 x 10
12
barrels) of which the United States
has 28.4 billion barrels (28.4 x 10
9
barrels), or 2.1% of the total world
reserves (BP, 2010).
In the crude state petroleum has minimal value, but when refined
it provides high-value liquid fuels, solvents, lubricants, and many
other products. Crude petroleum can be separated into a variety of
different generic fractions by distillation. And, the terminology of
these fractions has been bound by utility and often bears little relationship to composition.
The United States imports approximately 65% of its daily crude
oil and crude oil product requirements. As recent events have
shown, there seems to be little direction in terms of stability of supply or any measure of self-sufficiency in liquid fuels precursors,
other than resorting to military action. This is particularly important for the United States refineries because a disruption in supply
could cause major shortfalls in feedstock availability.
In keeping with the preferential use of lighter crude oil as well as
the maturation effect in the reservoir, crude oil currently available to
the refinery is somewhat different in composition and properties to
those available approximately 50 years ago (Swain, 1991,1993,1997,
2000). The current crude oils are somewhat heavier insofar as they
have higher proportions of non-volatile (asphaltic) constituents. In
fact, by the standards of yesteryear, many of the crude oils in use
would have been classified as heavy feedstocks, bearing in mind
that they may not approach the definitions used today for heavy
crude oil. Changes in feedstock character, such as this tendency to
heavier materials, require adjustments to refinery operations to handle these heavier crude oils to reduce the amount of coke formed
during processing and to balance the overall product slate.
2.6.2 Natural Gas
Natural gas is the gaseous mixture associated with petroleum
reservoirs and is predominantly methane, but does contain other
combustible hydrocarbon compounds as well as non-hydrocarbon compounds (Chapter 1) (Speight, 1993; Mokhatab et al, 2006;