ASPHALTENES (molecular properties)
Thermodynamic or kinetic control ??
in scientific modeling as well as in
industrial applications natural petroleum media and their components
particular, disperse phases) are commonly regarded as systems evolving
under thermodynamic control. In other words,
it is commonly assumed that physico-chemical parameters of petroleum
uniquely determined by the current thermodynamic parameters (first of
the current pressure ant
temperature). These assumptions are employed for evaluation of the
effects of various technological operations – e.g. thermal treatment in
reservoirs, transportation and storage equipment; pressure depletion as
result of oil/gas production; intermixing of different migrating fluids
course of reservoir development, etc.
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Our experiments have shown that the current
structure) of a disperse phase in petroleum is critically determined by
kinetic control. At the same set of
thermodynamic parameters various long-lived states of a disperse phase
co-exist. Each of these states has a unique “individual history” (has been
achieved as a result of a specific succession of
particular, for asphaltene dispersions of critical importance are
their individual “thermal histories” in the range of industrial
E.g., a short-time thermal treatment at 28-30oC
results in a noticeable restructuring of asphaltene
colloids – dimension of colloid particles, as well as their interaction
energies, increase; interactions with other petroleum components also
strongly affected. At lower temperatures the new state of asphaltene
is thermodynamically non-equilibrium.
However, owing to kinetic control the newly-acquired properties may be
over periods of several months/years (i.e. there is a certain “long-term
Temperature effect on an average volume of a particle in asphaltene
(Fluorescence studies of model oils)
Effect of pre-heating temperature on association energy in asphaltene
colloids at 8-18оС. (Rheological experiments with bitumen
Markedly different behaviour of asphaltene
colloids in: (1) a thermodynamically equilibrium state and (2) a
long-lived metastable state induced by a short-time pre-heating to 28-30оС.
(Mass of deposits at steel surfaces immersed in bitumen solutions)
different behaviour of asphaltene colloids in: (1) a thermodynamically
equilibrium state and (2) a long-lived metastable state induced by a
short-time pre-heating to 28-30оС.
(Dynamic viscosity of bitumen solutions)
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