CRUDE OIL CLASSIFICATION AND BENCHMARKS
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valuable than one of 20°API (specific gravity = 0.934) because it
contains more light fractions (e.g., gasoline) and fewer heavy, undesirable asphaltic constituents.
Crude oil is a mixture of hydrocarbons, often found together
with natural gas. The main characteristics of by which crude oil is
defined are: (1) density which, in the oil industry, is usually measured by its API gravity, and (2) sulfur content. Thus, crude oil is
usually described as sweet (low sulfur) or sour (high sulfur) and
light or heavy, depending on its density. Heavier oils may also be
described as medium and extra heavy oil although the definition of
this later is open to question. Although the classification of crude
oil may be defined by API gravity and sulfur content, this is not the
complete story and other methods of classification are available.
Only those methods of classification that have the potential to
affect the price are included here. Other methods are available
(Speight, 2007) but are more specific to the scientific aspect of crude
oil rather than to the pricing and are not included here.
4.1.1 Classification as a Hydrocarbon Resource
Petroleum is referred to generically as a fossil energy resource and
is further classified as a hydrocarbon resource and, for illustrative
or comparative purposes in this text, coal and oil shale kerogen
have also been included in this classification. However, the inclusion of coal and oil shale under the broad classification of hydrocarbon resources has incorrectly required that the term hydrocarbon
be expanded to include the macromolecular non-hydrocarbon
species that constitute coal and oil shale kerogen. The use of the
term organic sediments would be more accurate (Figure 4.1). The
inclusion of coal and oil shale kerogen in the category hydrocarbon
resources is due to the fact that these two natural resources will
produce hydrocarbons on high-temperature processing. Therefore,
if coal and oil shale kerogen are to be included in the term hydrocarbon resources, it is more appropriate that they be classed as
hydrocarbon-producing resources under the general classification
of organic sediments (Figure 4.2).
4.1.2 Classification by Chemical Composition
Composition refers to the specific mixture of chemical compounds
that constitute petroleum.
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valuable than one of 20°API (specific gravity = 0.934) because it
contains more light fractions (e.g., gasoline) and fewer heavy, undesirable asphaltic constituents.
Crude oil is a mixture of hydrocarbons, often found together
with natural gas. The main characteristics of by which crude oil is
defined are: (1) density which, in the oil industry, is usually measured by its API gravity, and (2) sulfur content. Thus, crude oil is
usually described as sweet (low sulfur) or sour (high sulfur) and
light or heavy, depending on its density. Heavier oils may also be
described as medium and extra heavy oil although the definition of
this later is open to question. Although the classification of crude
oil may be defined by API gravity and sulfur content, this is not the
complete story and other methods of classification are available.
Only those methods of classification that have the potential to
affect the price are included here. Other methods are available
(Speight, 2007) but are more specific to the scientific aspect of crude
oil rather than to the pricing and are not included here.
4.1.1 Classification as a Hydrocarbon Resource
Petroleum is referred to generically as a fossil energy resource and
is further classified as a hydrocarbon resource and, for illustrative
or comparative purposes in this text, coal and oil shale kerogen
have also been included in this classification. However, the inclusion of coal and oil shale under the broad classification of hydrocarbon resources has incorrectly required that the term hydrocarbon
be expanded to include the macromolecular non-hydrocarbon
species that constitute coal and oil shale kerogen. The use of the
term organic sediments would be more accurate (Figure 4.1). The
inclusion of coal and oil shale kerogen in the category hydrocarbon
resources is due to the fact that these two natural resources will
produce hydrocarbons on high-temperature processing. Therefore,
if coal and oil shale kerogen are to be included in the term hydrocarbon resources, it is more appropriate that they be classed as
hydrocarbon-producing resources under the general classification
of organic sediments (Figure 4.2).
4.1.2 Classification by Chemical Composition
Composition refers to the specific mixture of chemical compounds
that constitute petroleum.