243
10
Petroleum Analysis
10.1 INTRODUCTION
Petroleum exhibits a wide range of physical properties and several relationships can be made between
various physical properties (Speight, 2001). Whereas the properties such as viscosity, density, boiling point, and color of petroleum may vary widely, the ultimate or elemental analysis varies, as
already noted, over a narrow range for a large number of petroleum samples. The carbon content is
relatively constant, while the hydrogen and heteroatom contents are responsible for the major differences between petroleum. Coupled with the changes brought about to the feedstock constituents
by refinery operations, it is not surprising that petroleum characterization is a monumental task.
Although it is possible to classify refinery operations using the three general terms (1) separation,
(2) conversion, and (3) finishing (Chapter 15), the chemical composition of a feedstock is a much
truer indicator of refining behavior. Whether the composition is represented in terms of compound
types or in terms of generic compound classes, it can enable the refiner to determine the nature of
the reactions. Hence, chemical composition can play a large part in determining the nature of the
products that arise from the refining operations. It can also play a role in determining the means by
which a particular feedstock should be processed (Wallace et al., 1988; Speight, 2001; Speight and
Ozum, 2002).
The physical and chemical characteristics of crude oils and the yields and properties of products
or fractions prepared from them vary considerably and are dependent on the concentration of the
various types of hydrocarbons and minor constituents present. Some types of petroleum have economic advantages as sources of fuels and lubricants with highly restrictive characteristics because
they require less specialized processing than that needed for production of the same products from
many types of crude oil. Others may contain unusually low concentrations of components that are
desirable fuel or lubricant constituents, and the production of these products from such crude oils
may not be economically feasible.
Evaluation of petroleum for use as a feedstock usually involves an examination of one or more of
the physical properties of the material. By this means, a set of basic characteristics can be obtained
that can be correlated with utility. To satisfy specific needs with regard to the type of petroleum to
be processed, as well as to the nature of the product, various standards organizations, such as the
American Society for Testing and Materials in North America and the Institute of Petroleum in
Britain, have devoted considerable time and effort to the correlation and standardization of methods for the inspection and evaluation of petroleum and petroleum products (Institute of Petroleum,
IP, 2012). Thus, it is appropriate that in any discussion of the physical properties of petroleum and
petroleum products reference be made to the corresponding test, and accordingly, the various test
numbers have been included in the text.
10.2 PETROLEUM ASSAY
An efficient assay is derived from a series of test data that give an accurate description of petroleum
quality and allow an indication of its behavior during refining. The first step is, of course, to assure
adequate (correct) sampling by use of the prescribed protocols (ASTM D4057).
Thus, analyses are performed to determine whether each batch of crude oil received at the refinery is suitable for refining purposes. The tests are also applied to determine if there has been any
10
Petroleum Analysis
10.1 INTRODUCTION
Petroleum exhibits a wide range of physical properties and several relationships can be made between
various physical properties (Speight, 2001). Whereas the properties such as viscosity, density, boiling point, and color of petroleum may vary widely, the ultimate or elemental analysis varies, as
already noted, over a narrow range for a large number of petroleum samples. The carbon content is
relatively constant, while the hydrogen and heteroatom contents are responsible for the major differences between petroleum. Coupled with the changes brought about to the feedstock constituents
by refinery operations, it is not surprising that petroleum characterization is a monumental task.
Although it is possible to classify refinery operations using the three general terms (1) separation,
(2) conversion, and (3) finishing (Chapter 15), the chemical composition of a feedstock is a much
truer indicator of refining behavior. Whether the composition is represented in terms of compound
types or in terms of generic compound classes, it can enable the refiner to determine the nature of
the reactions. Hence, chemical composition can play a large part in determining the nature of the
products that arise from the refining operations. It can also play a role in determining the means by
which a particular feedstock should be processed (Wallace et al., 1988; Speight, 2001; Speight and
Ozum, 2002).
The physical and chemical characteristics of crude oils and the yields and properties of products
or fractions prepared from them vary considerably and are dependent on the concentration of the
various types of hydrocarbons and minor constituents present. Some types of petroleum have economic advantages as sources of fuels and lubricants with highly restrictive characteristics because
they require less specialized processing than that needed for production of the same products from
many types of crude oil. Others may contain unusually low concentrations of components that are
desirable fuel or lubricant constituents, and the production of these products from such crude oils
may not be economically feasible.
Evaluation of petroleum for use as a feedstock usually involves an examination of one or more of
the physical properties of the material. By this means, a set of basic characteristics can be obtained
that can be correlated with utility. To satisfy specific needs with regard to the type of petroleum to
be processed, as well as to the nature of the product, various standards organizations, such as the
American Society for Testing and Materials in North America and the Institute of Petroleum in
Britain, have devoted considerable time and effort to the correlation and standardization of methods for the inspection and evaluation of petroleum and petroleum products (Institute of Petroleum,
IP, 2012). Thus, it is appropriate that in any discussion of the physical properties of petroleum and
petroleum products reference be made to the corresponding test, and accordingly, the various test
numbers have been included in the text.
10.2 PETROLEUM ASSAY
An efficient assay is derived from a series of test data that give an accurate description of petroleum
quality and allow an indication of its behavior during refining. The first step is, of course, to assure
adequate (correct) sampling by use of the prescribed protocols (ASTM D4057).
Thus, analyses are performed to determine whether each batch of crude oil received at the refinery is suitable for refining purposes. The tests are also applied to determine if there has been any