Page 21 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

4 Bin Yuan and David A. Wood

secondary (initial water condition) modes of water flooding. Several field
examples have been reported using LSWF in North Slope of Alsaka
(Seccombe et al., 2010), Powder River Basin in Wyoming (Robertson,
2010), Norwegian continental shelf fields (Skrettingland et al., 2010) and
El-Morgan field, Gulf of Suez, Egypt (Darihim et al., 2013). Despite the
success of LSWF in core experiments and field pilots, the multiple
mechanisms impacting reservoirs and oil recovery during this technique
still remain debatable and lack of understanding.
Several major mechanism of formation damage and EOR have been
identified during LSWF, including: (1) wettability alteration toward more
water-wet conditions by releasing original mixed-wet particles (Alagic
and Skauge, 2010; Skauge, 2008); (2) wettability alteration due to mineral
dissolution and ion-exchange reactions (Lager et al. 2006); (3) emulsion
and clay swelling by multicomponent ionic exchanges among crude oil,
brine, and clay particles (Sorbie and Collins, 2010); (4) local pH increases
at water-clay interfaces that desorb organic materials from pore surfaces
(Austad et al., 2008); (5) fines migration (Aksulu et al., 2012) carrying
small amounts of residual oil through the detachment of oil-coated parti-
cles from rock grains. In addition, selected blockage of high-permeability
layers by fines migration provides a simple mobility-control method to
enhance sweep efficiency (Zeinijahromi, 2013; Yuan and Moghanloo,
2017b, 2018a).
To offset the potential damage of fines migration, different types of
acid systems have been developed to remove the formation fines plugged
in the near-wellbore region. In addition, gravel packs and sand-control
screens have been applied in the well bores under various downhole
conditions (Khilar and Fogler, 1998). Amorim et al. (2007) studied the
performance of various salts to inhibit clay swelling on various clays, and
confirmed that CaCl 2 concentrations were the most effective in inhibiting
clay swelling. They also defined the critical salt concentration (CSC)
required to inhibit clay swelling in the samples studied using different
salts, as: 0.5 M for NaCl, 0.4 M for KCl but only 0.2 M for CaCl 2 .
Nanoparticles can effectively mitigate formation damage caused by fine
particles and clogging pore-throats through enhancing attractive forces
among fine particles and grains (Arab and Pourafshary, 2013). Yuan et al.
(2018b,c) justified the positive effects of nanoparticle treatments (both
preflush and coinjection) to control fines migration.
In addition to the performance benefits, the synergistic effects of
applying IOR techniques in combination are well documented. Hence, it