Page 61 - Formation Damage during Improved Oil Recovery Fundamentals and Applications
P. 61
Low-Salinity Water Flooding: from Novel to Mature Technology 43
the clogging of fine particles into the pore-throats (Huang et al., 2008;
Yuan and Moghanloo, 2016; Yuan, 2017a,b). In practice, it is, therefore,
possible to improve the performance of LSWF by combining it with
nanoparticles applications in multilayered radial flow systems.
In an example of multilayered radial flow system (Fig. 2.12), the ratio
of permeability between two parallel layers is set as 2.0, and all the
other properties are identical. During the injection of low-salinity water,
the injection pressure for two layers is always kept identical. However, injec-
tion pressure increases with time due to progressive formation damage. The
production pressure at the outlet (production well) is also kept constant.
Even with the total injection rate held constant in the injection well, the
fractional rates of water entering each layer continuously change over time,
because of the changes of total fluid mobility within each layer.
The injection pressure loss at different times can be obtained by
integrating the flowing pressure gradient from the injection well to the
production well, as shown in Eq. (2.12):
1
)
ð
dx D
ðÞ
ðÞ
Δp 1 t D 5 q 1 t D
4πx D λ t1
0
1
ð
dx D 1 1
ðÞ
ðÞ
ðÞ
Δp 2 t D 5 q 2 t D q t t D 5 Const: 1
1 1
4πx D λ t2 ! Ð dx D Ð dx D
0
1 0 4πx D λ t1 0 4πx D λ t2 (2.12)
ð
dx D
ðÞ
ðÞ
Δpt D 5 q t t D
4πx D λ t
0
1
5
1
Ð dx D
0 4πx D λ t
Due to the layered heterogeneity, the fluid flowing mobility within
each layer is different (Yuan et al. 2018b). Assuming constant injection
rates for the sum of the layers, a harmonic mean of flowing mobility for
the multilayered system can be derived from Eq. (2.12). As low-salinity
waterflooding continues, the injection pressure to maintain a constant
injection rate continues to increase due to the formation damage caused
by fines migration. The injection pressure loss for the whole-layered
system can be calculated using the harmonic mean of flowing mobility, as
expressed by Eq. (2.13):
