Page 62 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

44 David A. Wood and Bin Yuan

P = P
inj 1 inj 2
q t = q 1 + q 2 = Const. Injection well

High-permeability layer 1 Flood-front

Flood-front
Low-permeability layer 2 Flood-front

Flood-front

Nanofluid treatment range P out 1 = P out 2
Figure 2.12 Scheme of near-well nanofluid pretreatment to control fines particles
during low-salinity waterflooding in two-layered heterogenous reservoirs.

ðÞ
q t t D
Δpt D 5 (2.13)
ðÞ
1 1 1
Ð 1 dx D Ð 1 dx D
0 4πx D λ t1 0 4πx D λ t2
The improvement of mobility control caused by fines migration/
straining is expressed in Eq. (2.14) as the ratio (R) of the advancing loca-
tions of the flood fronts within each layer:

x fD10 1 @f w t D1
@S w
x fD1 S wf
R 5 5 (2.14)
x fD2 x fD20 1 @f w t D2
@S w
S wf
The evolution of water saturation profile along each layer at different
moments is presented in Fig. 2.13. At the early period of low-salinity
waterflooding, a larger percentage of injected water enters the high-
permeability layer, and the flood-front along the high-permeability layer
moves much faster. However, with the accumulation of low-salinity water
in the high-permeability layer involving larger swept areas, more severe
damage of permeability is induced by amounts of fines detachment and
straining. This is a consequence of both higher flow rates and lower fluid
salinity in the high-permeability layer. As a result, both the advancing