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Introduction
the diluted oil to the refinery [5]. Fluid and composition properties are usually de-
termined from laboratory studies on samples collected from the bottom of the well
or at the surface but such experimental data are, however, not always available or
very costly to obtain and so, their determination in real-time during test drilling is
of key importance [6]. Estimates of viscosity and phase behaviour can be performed
using empirical equations (Equations of State) but there is one major drawback; the
composition of the crude oil has a major influence on the predicted properties and
must be estimated if not available. To improve on traditional methods of analysis
and predictions of equations of state, non-destructive spectroscopic techniques have
been investigated as a means to quantitatively analyse crude oils because of their
versatility, fast response and low cost.
1.1 Crude Oils
1.1.1 Formation
Crude oil and natural gas are the product of compression and heating of ancient
organic materials over geological time frames [7, 8]. Today’s oils are formed from
the preserved remains of prehistoric plankton and algae, which had settled to a
sea or lake bottom in large quantities under anoxic conditions. The remains of
prehistoric terrestrial plants, on the other hand, tends to form coal (Figure 1.1). The
Figure 1.1: Formation of crude oil from land and sea based sources.
Viscosity Pressure-Volume-Temperature (PVT) phase behaviour are commonly determined.
PVT diagrams are specific to a crude oil and can be used for modeling the behaviour of the
oil at any pressure and temperature; for example, what happens to the crude oil when brought
from the reservoir to the surface [6].
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