Page 53 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

Low-Salinity Water Flooding: from Novel to Mature Technology 35

0 0
σ s ðεðγ ÞÞ 5 Δσðεðγ ÞÞ (2.4)
Normalized permeability is then inversely proportional to the strained
particle concentration, enabling the induced formation damage via LSWF
to be quantified (Zeinijahromi et al., 2015a) using Eq. (2.5):

k 0
5 1 1 βσ s ðεÞ (2.5)
kðσ s Þ
where: k 0 is the initial undamaged permeability, k(σ s ) is the damaged for-
mation permeability, and β is the formation damage coefficient reflecting
the degree of formation damage due to pore plugging. This approach
to explain and model fines-assisted water flooding is supported by experi-
mental studies (Lemon, 2011; Hussain et al., 2013).

2.6.2 LSWF to induce fines-migration-related formation
damage
Zeinijahromi et al. (2015a) used these relationships to simulate the effects
of induced formation damage applying LSWF to improve the sweep
efficiency of edge-water drive reservoirs with in-situ movable fines.
A small volume of LSW was injected into the downdip, watered-out
wells, creating a low-permeability barrier to water encroachment.
Slowing water encroachment and inhibiting its preferential flow relative
to oil resulted in IOR of 3 5% in the reservoir simulated. The incre-
mental oil recovery was attributed to the delay of water breakthrough in
the up-dip producing wells and delaying their abandonment.
Zeinijahromi et al. (2015b) reported on the performance of long-term
LSWF in the Zichebashskoe oil field (Russia) in reducing permeability by
fines migration decreasing injected water mobility and increasing reser-
voir sweep. The 24-year production history of that field included only 7
years of LSWF. Reservoir simulation sensitivity analysis matching the field
production history was used to explain why the incremental oil recovery
and decrease in water cut due to LSWF was so small (i.e., just 4%). Three
factors can be identified from the simulation analysis as possible explana-
tion for this: (1) the oil-bearing formation had been extensively flooded
during the primary production phase by high-salinity water, encroaching
from the underlying aquifer, during the 17 years of production resulting
in high water cuts of produced fluids. This change to the reservoir had
occurred before LSWF began, which potentially impacted the availability
of mobile fines once LSWF began; (2) LSWF injection directly into