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determine the inner structure of emulsions, and can often also pro-
vide evidence of structural changes.
Recently, we have shown that the rheology of petroleum fluids
may be sensitive to structural transformations, which often are far
too subtle to be detectable by other experimental techniques (1, 2).
Hence, in this study we regard a viscometer as a probe not only of
the macroscopic flow parameters but also of the subtle molecular-
structure features of petroleum emulsions
2. Materials and Methods
2.1. Samples
The crude oil/water samples (25 vol.% of the emulsified reser-
voir water) were obtained directly from the oil-production well
(Tatarstan, Russia). The water-free oil phase contained 3.5 wt.%
asphaltenes, 1.6 wt.% waxes, 22 wt% resins. During prolonged
laboratory storage at room temperature, oil and water phases
separated from the samples by gravity, so that the studied W/O
emulsions were prepared by re-mixing the separated phases at the
initial v/v ratio.
The bitumen emulsions were prepared from the “HIMEKO”
concentrate (HIMEKO Co., Moscow) which contains 50 vol.% of bi-
tumen (pavement grade), 40 vol.% of water and 10 vol. % of stabi-
liser (CaCl
2
), acid (HCl), various unspecified surfactants, dispers-
ants and modificators. As recommended by the producer, industrial
bitumen emulsions are produced by 1/1 dilution of the concentrate
with the separately provided “KORE” solvent (hydrocarbon rectifi-
cation residues). Both products were used as received.
2.2 Apparatus and procedure
The effect of formation temperature on rheology of all samples
have been investigated at flow temperatures of 8–30°C , for shear
rates up to 150 s
-1
, in a Brookfield Programmable DV-II+ Viscome-
ter (Brookfield Eng. Labs., Inc., USA), equipped with a YULA–15
Adapter with a concentric cylinder geometry. The inner cylinder
diameter was 25.15 mm with the gaps of 1.23 mm. Each rheologi-
27
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