Составители:
The 2004 International Conference on Heavy Organic Depositions
Los Cabos, Baja, Mexico, November 2004
WELL-DEFINED METASTABLE (TRANSIENT) STATES
OF ASPHALTENE COLLOIDS
Igor N. Evdokimov
Department of Physics, Gubkin Russian State University of Oil and Gas,
Leninsky Prospekt, 65, Moscow B-296, GSP-1, 119991, Russia.
E-mail: [email protected]
Abstract
Experiments with crude oils, toluene solutions of oils and of vac-
uum residua have shown that the colloidal subsystems of these flu-
ids may be transformed to long-lived (up to 6 months at RT) me-
tastable (possibly transient) states merely by a mild thermal pre-
treatment (e.g. 0.5 hr at 28–36°C). These states are fairly well-
defined as revealed by distinctly different data sets for various pa-
rameters in non-treated (equilibrium) and pre-treated (metastable)
fluids. In particular, at 20°C a metastable (transient) state is dis-
tinguished by ≈25% increase of the mass of deposits at metal sur-
faces, by ≈5% decrease of dynamic viscosity, etc. A plausible
mechanism of transition to a metastable (transient) state is partial
“desorption” of resin “shells” from asphaltene molecular nano-
clusters (MNCs) as a result of a structural transformation of MNCs
at ≈28°C. Consequently, steric stabilization of asphaltene colloids
by resins is disrupted and directly interacting MNCs may form
more complex aggregates, fairly long-lived at lower temperatures.
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