32
that characterizes the reservoir under consideration. Under field conditions, the
pressure may drop below the bubble point without forming gas bubbles due to an
energy barrier that has to be overcome during nucleation as described in the classical nucleation theory (Blander and Katz 1975). A large pressure difference known
as capillary or Laplace pressure impedes growth of nuclei below the so-called critical nucleation radius. Different approaches exist to predict the related critical supersaturation, i.e., the pressure difference to the equilibrium conditions, at which
nucleation sets on (Kalikmanov 2013; Bauget and Lenormand 2002). In most cases,
the interfacial tension is used as a crucial property for describing the nucleation
phenomena, also because of practical reasons. Transferred to the situation of deepsea spills, gas-saturated droplets undergo a decreasing pressure on their way toward
the sea surface and may at some point start to degas which is discussed in this book
in Chap. 5 and in Pesch et al. (2018) and subsequently change further properties like
viscosity and density. In continuation, methods are explained for determining the
relevant properties of real fluid mixtures at the predominating elevated pressures
under deep-sea conditions.
3.2.1 Bubble Point
Determination of the bubble point of a live oil is part of the PVT analysis. The volume inside the sampling cylinder, mostly containing a piston to separate the oil
from a hydraulic fluid, is increased step-by-step while continuously recording the
pressure. At the bubble point, pressure reduction slows down due to formation of a
compressible second phase (Danesh 1998).
3.2.2 Gas Saturation
The capacity of the petroleum liquid to dissolve gas at given conditions may be
determined by different ways:
1. Completely decompress the live oil from the bubble point down to atmospheric
pressure while capturing the amount of gas previously being dissolved (Jaggi
et al. 2017; Chap. 8).
2. Gravimetrically, using a microbalance for detecting the gas uptake of the liquid
phase at given pressure and temperature until reaching equilibrium (Knauer et al.
2017).
In Sect. 3.3.2 we report solubility data determined by both methods along with
modeled data. There is a deviation among both experimental approaches: at lower
pressures the second method seems to give more reliable data, whereas at higher pressures, the gravitational method (2) clearly underestimates the solubility due to the
extraction of lighter components and subsequent loss of mass (see also Sect. 3.3.2).
T. B. P. Oldenburg et al.
that characterizes the reservoir under consideration. Under field conditions, the
pressure may drop below the bubble point without forming gas bubbles due to an
energy barrier that has to be overcome during nucleation as described in the classical nucleation theory (Blander and Katz 1975). A large pressure difference known
as capillary or Laplace pressure impedes growth of nuclei below the so-called critical nucleation radius. Different approaches exist to predict the related critical supersaturation, i.e., the pressure difference to the equilibrium conditions, at which
nucleation sets on (Kalikmanov 2013; Bauget and Lenormand 2002). In most cases,
the interfacial tension is used as a crucial property for describing the nucleation
phenomena, also because of practical reasons. Transferred to the situation of deepsea spills, gas-saturated droplets undergo a decreasing pressure on their way toward
the sea surface and may at some point start to degas which is discussed in this book
in Chap. 5 and in Pesch et al. (2018) and subsequently change further properties like
viscosity and density. In continuation, methods are explained for determining the
relevant properties of real fluid mixtures at the predominating elevated pressures
under deep-sea conditions.
3.2.1 Bubble Point
Determination of the bubble point of a live oil is part of the PVT analysis. The volume inside the sampling cylinder, mostly containing a piston to separate the oil
from a hydraulic fluid, is increased step-by-step while continuously recording the
pressure. At the bubble point, pressure reduction slows down due to formation of a
compressible second phase (Danesh 1998).
3.2.2 Gas Saturation
The capacity of the petroleum liquid to dissolve gas at given conditions may be
determined by different ways:
1. Completely decompress the live oil from the bubble point down to atmospheric
pressure while capturing the amount of gas previously being dissolved (Jaggi
et al. 2017; Chap. 8).
2. Gravimetrically, using a microbalance for detecting the gas uptake of the liquid
phase at given pressure and temperature until reaching equilibrium (Knauer et al.
2017).
In Sect. 3.3.2 we report solubility data determined by both methods along with
modeled data. There is a deviation among both experimental approaches: at lower
pressures the second method seems to give more reliable data, whereas at higher pressures, the gravitational method (2) clearly underestimates the solubility due to the
extraction of lighter components and subsequent loss of mass (see also Sect. 3.3.2).
T. B. P. Oldenburg et al.