Page 282 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

Formation Damage by Organic Deposition 253

asphaltene onset pressure. The most important factors which determine
asphaltene precipitation during CO 2 flooding are the CO 2 concentration
and the pore topography (Srivastava and Huang, 1997).
It has been determined that in the Berea sandstone from west
Virginia, deposition changes the rock wettability to oil wet, regardless of
the initial rock wettability. Huang (1992) believed that, depending on the
asphaltene content, the wettability of Berea sandstone would change from
water wet to oil wet, resulting in lower crude oil recovery efficiency.
Gonzalez et al. (2007) concluded that, depending on the range of pressure
and temperature, CO 2 can either act as an inhibitor or enhancer for
asphaltene precipitation.
It can be concluded that the main parameters determining the
asphaltene precipitation and deposition are temperature, pressure, and
oil composition, hence any change in those factors may affect the crude
oil stability and trigger asphaltene precipitation. CO 2 injection may
cause a change in oil composition (the solubility of asphaltenes in oil)
and therefore acts as a precipitant for asphaltenes. That notwith-
standing, there is still need for research on asphaltene deposition under
dynamic conditions in porous media during CO 2 flooding and
and oil mixtures
on modeling asphaltene solubility in CO 2
(Seifried, 2016).

6.4 DEPOSITION IN POROUS MEDIA

As earlier stated, studies of asphaltene deposition are conducted by
means of microfluidic experiments, TC cells or core flooding experi-
ments through a porous media.

6.4.1 Microfluidic experiments
The use of microfluidic devices over the past 15 years has opened new
possibilities in studying fluid mechanics and discovering new physical
phenomena. As the dimension of the equipment shrinks, the bulk prop-
erties of the fluid become less important and interfacial properties and
fluid-solid interactions dominate.