CRUDE OIL CLASSIFICATION AND BENCHMARKS 111
extremely viscous as it occurs in the definition of tar sand. In fact,
when used in conjunction with the recovery method, pour point
offers more general applicability to the conditions of the oil in the
reservoir or the bitumen in the deposit, and a comparison of the two
temperatures shows promise and warrants further consideration.
4.1.7 Recovery Method
All of the classification systems described above are based on the
assumption that petroleum can be more or less characterized by the
properties of one or a few fractions. However, the properties of certain fractions of a crude oil are not always reflected in those of other
fractions of the same oil; plus, any method of classification in which
the properties of a certain fraction are extrapolated to the whole
crude oil must be applied with caution as serious errors can arise.
In order to classify petroleum, heavy oil, and tar sand bitumen, the use of a single parameter such as viscosity is not enough
(Speight, 2007). Other properties, such as API gravity, elemental
analysis, composition, the properties of the fluid in the reservoir,
and the method of recovery need to be acknowledged.
The United States Congress has defined tar sands as "the several rock types that contain an extremely viscous hydrocarbon
which is not recoverable in its natural state by conventional oil well
production methods including currently used enhanced recovery
techniques" (US Congress, 1976). By inferences, conventional petroleum and heavy oil can be recovered by currently used enhanced
recovery techniques. Furthermore, conventional petroleum can be
recovered by primary and secondary techniques.
However, the methods of pricing crude oil require something
more than these general properties and methods of classification,
although some of the parameters, such as API gravity and sulfur
content, are still employed. It is here that the need for benchmark
crude oils enters the arena.
4.2 Classification of Reserves
The classification of reserves and, hence, reserve estimates for
crude oil, are very difficult to develop. There are various versions
of crude oil reserves of which the most frequently used is the BP
Statistical Review of World Energy (BP, 2008). However, even the
extremely viscous as it occurs in the definition of tar sand. In fact,
when used in conjunction with the recovery method, pour point
offers more general applicability to the conditions of the oil in the
reservoir or the bitumen in the deposit, and a comparison of the two
temperatures shows promise and warrants further consideration.
4.1.7 Recovery Method
All of the classification systems described above are based on the
assumption that petroleum can be more or less characterized by the
properties of one or a few fractions. However, the properties of certain fractions of a crude oil are not always reflected in those of other
fractions of the same oil; plus, any method of classification in which
the properties of a certain fraction are extrapolated to the whole
crude oil must be applied with caution as serious errors can arise.
In order to classify petroleum, heavy oil, and tar sand bitumen, the use of a single parameter such as viscosity is not enough
(Speight, 2007). Other properties, such as API gravity, elemental
analysis, composition, the properties of the fluid in the reservoir,
and the method of recovery need to be acknowledged.
The United States Congress has defined tar sands as "the several rock types that contain an extremely viscous hydrocarbon
which is not recoverable in its natural state by conventional oil well
production methods including currently used enhanced recovery
techniques" (US Congress, 1976). By inferences, conventional petroleum and heavy oil can be recovered by currently used enhanced
recovery techniques. Furthermore, conventional petroleum can be
recovered by primary and secondary techniques.
However, the methods of pricing crude oil require something
more than these general properties and methods of classification,
although some of the parameters, such as API gravity and sulfur
content, are still employed. It is here that the need for benchmark
crude oils enters the arena.
4.2 Classification of Reserves
The classification of reserves and, hence, reserve estimates for
crude oil, are very difficult to develop. There are various versions
of crude oil reserves of which the most frequently used is the BP
Statistical Review of World Energy (BP, 2008). However, even the