106 PETROLEUM TECHNOLOGY, ECONOMICS, AND POLITICS
depending on its composition. It is usually black or dark brown,
although it may be yellowish or even greenish. In fact, the need
to classify crude oil arose because the quality of crude oil dictates
the level of processing and conversion necessary to achieve what a
refiner sees as an optimal mix of products.
Different types of crude oil yield a different mix of products,
depending on the crude oil's natural qualities. Their density, measured as American Petroleum Institute (API) gravity, and their sulfur content, typically differentiates crude oil types. Crude oil with
a low API gravity is considered a heavy crude oil and typically has
higher sulfur content and a larger yield of lower-valued products.
Therefore, the lower the API of a crude oil, the lower the value it
has to a refiner as it will either require more processing or yield a
higher percentage of lower-valued products such as heavy fuel oil,
which can often sell for less than crude oil.
Using more expensive, lighter and sweeter crude oil requires less
refinery upgrading. However, supplies of light, sweet crude oil are
decreasing and the differential between heavier and sourer crudes
is increasing. Using cheaper heavier crude oil means more investment in upgrading processes. Costs and payback periods for refinery processing units must be weighed against anticipated crude oil
costs and the projected differential between light and heavy crude
oil prices. Furthermore, the difference in value between light and
heavy oil is primarily determined in the market for each type and
a widening of the differential generally leads to poorer profitability
for heavy oil producers.
Crude slates and refinery configurations must take into account
the type of products that will ultimately be needed in the marketplace. The quality specifications of the final products are also
increasingly important as environmental requirements become
more stringent.
The original methods of classification arose because of the commercial interest in and recognition of the different types of crude
oil, and were a means of providing refinery operators with a rough
guide to processing conditions. It is therefore not surprising that
systems based on a superficial inspection of a physical property,
such as specific gravity or API (Baume) gravity, are easily applied,
and are actually used to a large extent in expressing the quality of
crude oils. Such a system is approximately indicative of the general
character of a crude oil as long as materials of one general type are
under consideration. For example, among crude oils from a particular area, an oil of 40°API (specific gravity = 0.825) is usually more
depending on its composition. It is usually black or dark brown,
although it may be yellowish or even greenish. In fact, the need
to classify crude oil arose because the quality of crude oil dictates
the level of processing and conversion necessary to achieve what a
refiner sees as an optimal mix of products.
Different types of crude oil yield a different mix of products,
depending on the crude oil's natural qualities. Their density, measured as American Petroleum Institute (API) gravity, and their sulfur content, typically differentiates crude oil types. Crude oil with
a low API gravity is considered a heavy crude oil and typically has
higher sulfur content and a larger yield of lower-valued products.
Therefore, the lower the API of a crude oil, the lower the value it
has to a refiner as it will either require more processing or yield a
higher percentage of lower-valued products such as heavy fuel oil,
which can often sell for less than crude oil.
Using more expensive, lighter and sweeter crude oil requires less
refinery upgrading. However, supplies of light, sweet crude oil are
decreasing and the differential between heavier and sourer crudes
is increasing. Using cheaper heavier crude oil means more investment in upgrading processes. Costs and payback periods for refinery processing units must be weighed against anticipated crude oil
costs and the projected differential between light and heavy crude
oil prices. Furthermore, the difference in value between light and
heavy oil is primarily determined in the market for each type and
a widening of the differential generally leads to poorer profitability
for heavy oil producers.
Crude slates and refinery configurations must take into account
the type of products that will ultimately be needed in the marketplace. The quality specifications of the final products are also
increasingly important as environmental requirements become
more stringent.
The original methods of classification arose because of the commercial interest in and recognition of the different types of crude
oil, and were a means of providing refinery operators with a rough
guide to processing conditions. It is therefore not surprising that
systems based on a superficial inspection of a physical property,
such as specific gravity or API (Baume) gravity, are easily applied,
and are actually used to a large extent in expressing the quality of
crude oils. Such a system is approximately indicative of the general
character of a crude oil as long as materials of one general type are
under consideration. For example, among crude oils from a particular area, an oil of 40°API (specific gravity = 0.825) is usually more