Page 275 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

246 Rouzbeh G. Moghanloo et al.

Figure 6.1 Asphaltene structure.

the variation for the chemical structure of asphaltene, as shown in the struc-
ture proposed in Fig. 6.1. Sabbah et al. (2011),statesthatthe “Island” struc-
ture is the more dominant one, but ongoing debates still question the
dominance. The “Island” structure has one single polycyclic aromatic hydro-
carbons (PAH) core with cycloalkanes and external branched alkyl substitu-
ents, whereas the more recently proposed “Archipelago” structure comprises
smaller condensed aromatic groups (Yarranton et al., 2013).
Pfeiffer and Saal (1940) described the phase separation of highly aro-
matic components with polar structures promoting dispersion. Mullins
(2010, 2011) later described the self-formation of aromatic clusters from
nanoaggregates by π—π-stacking of the aromatic rings in crude oil or
toluene, referred to as the “Yen-Mullins-Model” in the literature.
Yarranton et al. (2013) described the self-association concept by stating
that asphaltenes in toluene comprise a mixture of associating and nonasso-
ciating species. Though techniques like VPO and elemental analysis,
among others, it was concluded that approximately 90% of asphaltenes
tend to self-associate with the nonassociated asphaltenes being smaller and
more aromatic than the bulk asphaltenes (Seifried, 2016).

6.1.4 Monitoring and remediation
Remediation of asphaltene deposits involves using strong chemical solvents
and exposing said deposits to turbulent flow. These chemicals have adverse
effects on health, safety, and environment, along with production deferrals
because of operation downtime. (Gonzales et al., 2016). A dynamic
model provided by Dabir et al. (2016) enables the determination of the