Page 208 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

182 Bin Yuan and Rouzbeh G. Moghanloo

The modified Darcy’s flow equation is then applied by considering
the damage of core permeability caused by nanoparticles adsorption and
straining effects (Sharma, 1987):

dp
k 0
U 5 (4.5)
ð
s
a
Lμ 1 1 β σ NP 1 β S NP Þ dx D
As the injected nanoparticles concentration increases, the nanoparticles
adsorption quantities can be enhanced (the solid line in Fig. 4.2A). The
detachment of reversible adsorbed nanoparticles occurs during the postflush
of brine. The amounts of reversible nanoparticles adsorption also increase
along with the increase of the injected nanoparticles concentration (the
dashed line in Fig. 4.2A). In addition, for the cases of different nanofluid
injection concentration, the percentages of reversible adsorption remain
approximately the same, i.e., about 30% of the total amount of nanoparti-
cles adsorption. Fig. 4.2 bindicates that the nanoparticles adsorption and
straining rates vary as functions of injected nanoparticles concentration.
The higher the injected nanoparticles concentration is, the larger the nano-
particles adsorption and straining rates would be. In addition, the rates of
nanoparticles adsorption are usually larger than nanoparticles straining rates.
Fig. 4.2C summarizes the formation damage coefficients caused by both:
nanoparticles adsorption and straining. It explains the reasons why pressure
drop increases during nanofluid injection. In contrast to the relationship
between nanoparticles adsorption and straining rates, the formation damage
effects of nanoparticles straining are much larger than that of nanoparticles
adsorption. That is to say, the formation damage caused by nanoparticles
straining dominates the increase of pressure drop.

4.4 EFFECTIVENESS OF NANOPARTICLES UTILIZATION
TO MITIGATE FINES MIGRATION IN WATER FLOW

The positive contributions of nanoparticles to mitigate fines migra-
tion can be characterized by the enhancement of the maximum retention
concentration of fine particles onto rock grains through two reactions
(Yuan and Moghanloo, 2016): (1) adsorption of nanoparticles onto the
fines/grain surfaces; and (2) increased concentration of fines attachment
onto pore surfaces via reducing the surface potential between grains and
fines. Yuan et al. (2018a,b,c) proposed two different approaches of
nanoparticles utilization to effectively enhance the capability of porous