Page 281 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

252 Rouzbeh G. Moghanloo et al.

reduce the formation damage for crude oils with a relatively high content
of asphaltenes. According to Kokal and Sayegh (1995), some of the fac-
tors which influence adsorption of asphaltenes on the mineral surface are:
(1) The morphology and chemistry of the mineral surface, (2) the amount
of asphaltenes and resins present in the crude oil, (3) the composition and
pH of the brines in the reservoir rock, and (4) pressure and temperature
in the reservoir rock.
Leontaritis and Mansoori (1988) reviewed several experiences of the
oil industry dealing with asphaltene issues during production in the
Mata-Acema and Boscan fields, Venezuela. The reservoir in the Mata-
Acema field is made out of sandstone where the producing fluid contains
mainly C7 1 fractions with an asphaltene content of 0.4% 9.8%. The
asphaltene issues reported from this field were severe, whereas no asphal-
tene problems were reported from the Boscan field. The Boscan field is a
sandstone and produces mainly heavy oils with an asphaltene content of
17.2%. Alian et al. (2011) and Behbahani et al. (2012) attributed the dif-
ferences to the lower solubility of asphaltenes in lighter crude oils in the
Mata-Acema field.
The asphaltene content from the stock tank oil produced from the
Hassi Messaoud field sandstone reservoir (Algeria) was measured to be
0.062%. Despite the very low asphaltene content, deposition problems
were reported from the start of the production onwards. Wells lost up to
25% of the wellhead pressure in only 2 weeks, causing significant loss in
production. Furthermore, a solvent treatment and circulation of oil were
used in the Ventura Avenue field (California) to avoid or reduce deposi-
tion, however, this did not lead to a great improvement in oil recovery.

6.3.3 Asphaltene deposition during CO 2 flooding
CO 2 can also induce asphaltene precipitation. Negahban et al. (2003)
studied crude oil stability after the introduction of CO 2 and hydrocar-
bons. At reservoir conditions, the crude oil was understood to be
stable in terms of asphaltene precipitation. However, whereas the addition
of CO 2 did not show any such effect, the introduction of hydrocarbons
seemed to have induced asphaltene precipitation. Gholoum et al. (2003)
investigated the effects of C1 C7 and CO 2 on the asphaltene precipita-
tion onset point on Kuwaiti reservoir fluids and stated that in their work,
CO 2 is the most effective precipitant in terms of showing the lowest