26
properties of the petroleum from the well head into the deep sea. A better understanding of these properties is crucial for the development of near-field oil spill
models, oil droplet and gas bubble calculations, and partitioning behavior of oil
components in the water. Section 3.1 introduces general aspects of the origin of
petroleum, the impact of geochemical processes on the composition of a petroleum,
and some molecular compositional and physicochemical background information
of the Macondo well oil. Section 3.2 gives an overview over experimental determination of all relevant physicochemical properties of petroleum, especially of petroleum under reservoir conditions. Based on the phase equilibrium modeling using
equations of state (EOS), a number of these properties can be predicted which is
presented in Sect. 3.3 along with a comparison to experimental data obtained with
methods described in Sect. 3.2.
Keywords Physicochemical oil properties · Molecular oil composition · Deep sea
· Petroleum reservoir · Phase equilibria modeling
3.1 Molecular Composition and Physical Properties
of Petroleum in Reservoirs
Petroleum is one of the most complex naturally occurring organic mixtures containing
in some cases over 100,000 different chemical molecules (including isomers). It originates from sedimentary organic matter which itself is derived from once-living organisms. The molecular composition of petroleum varies greatly, ranging from the
simplest gas (methane), condensates, conventional crude oil to heavy oil and oil sands
bitumen with complex molecules such as asphaltenes with molecular weights in
excess of 1000 daltons (Da). The composition of oil is commonly divided into four
fractions based on liquid chromatography behavior of the oil constituents. Two of
these fractions comprise the saturated and aromatic hydrocarbons, whereas the other
two non-hydrocarbon fractions are named resins and asphaltenes. The latter two fractions contain one or more heteroatoms in the form of functional groups per molecule.
The majority of heteroatoms (defined as atoms which are not carbon or hydrogen) in
oil constituents are typically nitrogen, sulfur, and oxygen. In addition, metals such as
nickel and vanadium are common in porphyrinic structures. The proportions of these
hydrocarbon and non-hydrocarbon fractions vary greatly from non-hydrocarbon fractions containing less than 1% in some condensates to over 50% in highly viscous
extra-heavy oils and bitumen from the oil sands. In conventional crude oils, the proportion of the non-hydrocarbon fractions is typically below 20%. The composition
and the interaction of the oil constituents determine the physical and chemical properties of petroleum such as density, viscosity, water solubility, evaporation, and emulsion-forming potential among others. For example, some oil sands bitumens have
densities greater than that of water and viscosities of over 1000,000 centipoise (cP) at
ambient conditions, whereas the viscosities of some condensates are equal or below
that of water (1 cP) with densities as low as 750 kg m
−3
.
T. B. P. Oldenburg et al.
properties of the petroleum from the well head into the deep sea. A better understanding of these properties is crucial for the development of near-field oil spill
models, oil droplet and gas bubble calculations, and partitioning behavior of oil
components in the water. Section 3.1 introduces general aspects of the origin of
petroleum, the impact of geochemical processes on the composition of a petroleum,
and some molecular compositional and physicochemical background information
of the Macondo well oil. Section 3.2 gives an overview over experimental determination of all relevant physicochemical properties of petroleum, especially of petroleum under reservoir conditions. Based on the phase equilibrium modeling using
equations of state (EOS), a number of these properties can be predicted which is
presented in Sect. 3.3 along with a comparison to experimental data obtained with
methods described in Sect. 3.2.
Keywords Physicochemical oil properties · Molecular oil composition · Deep sea
· Petroleum reservoir · Phase equilibria modeling
3.1 Molecular Composition and Physical Properties
of Petroleum in Reservoirs
Petroleum is one of the most complex naturally occurring organic mixtures containing
in some cases over 100,000 different chemical molecules (including isomers). It originates from sedimentary organic matter which itself is derived from once-living organisms. The molecular composition of petroleum varies greatly, ranging from the
simplest gas (methane), condensates, conventional crude oil to heavy oil and oil sands
bitumen with complex molecules such as asphaltenes with molecular weights in
excess of 1000 daltons (Da). The composition of oil is commonly divided into four
fractions based on liquid chromatography behavior of the oil constituents. Two of
these fractions comprise the saturated and aromatic hydrocarbons, whereas the other
two non-hydrocarbon fractions are named resins and asphaltenes. The latter two fractions contain one or more heteroatoms in the form of functional groups per molecule.
The majority of heteroatoms (defined as atoms which are not carbon or hydrogen) in
oil constituents are typically nitrogen, sulfur, and oxygen. In addition, metals such as
nickel and vanadium are common in porphyrinic structures. The proportions of these
hydrocarbon and non-hydrocarbon fractions vary greatly from non-hydrocarbon fractions containing less than 1% in some condensates to over 50% in highly viscous
extra-heavy oils and bitumen from the oil sands. In conventional crude oils, the proportion of the non-hydrocarbon fractions is typically below 20%. The composition
and the interaction of the oil constituents determine the physical and chemical properties of petroleum such as density, viscosity, water solubility, evaporation, and emulsion-forming potential among others. For example, some oil sands bitumens have
densities greater than that of water and viscosities of over 1000,000 centipoise (cP) at
ambient conditions, whereas the viscosities of some condensates are equal or below
that of water (1 cP) with densities as low as 750 kg m
−3
.
T. B. P. Oldenburg et al.