Page 112 - Hybrid Enhanced Oil Recovery Using Smart Waterflooding

104 Hybrid Enhanced Oil Recovery using Smart Waterflooding

tertiary recoveries of coreflooding. The crude oil has injection of Flopaam 3630s polymer slug follows the
TAN of 0.15 mg KOH/g and TBN of 1.29 mg KOH/g. surfactant slug injection. The coreflooding experiments
The formation water of 231,194.9 ppm TDS and syn- are designed with secondary waterflood, and tertiary
thetic water of 14,063.3 ppm TDS are prepared. The surfactant flood followed by polymer flood. The core-
synthetic water is modified to make the low-salinity flooding experiments use high- and low-salinity
and low-hardness alkaline solution by extracting the makeup brines. As observed in the previous studies
divalent cations and adding the chemical additive. of LSPF, the polymer has less degradation in low
Two samples of low-salinity and low-hardness alkali so- salinity condition to reach the target viscosity. Less
lutions with different concentrations of chemical addi- polymer concentration by a factor of 2 is required for
tive are prepared. The diluted synthetic water of the low-salinity polymeric solution compared with
3587.45 ppm TDS is also investigated. As the salinity the high-salinity polymeric solution. The polymer
decreases and pH increases, both IFT and contact angle slug injection increases the differential pressure regard-
decrease. The results of IFT and contact angle measure- less of salinity condition. Despite the less polymer con-
ments indicate that the acidic component of crude oil centration, significantly higher increment of
reduces the IFT at high pH condition and modifies the differential pressure is observed in LSPF compared
wettability. In the adsorption test, the low-salinity and with the polymer flood using high salinity. It implies
low-hardness alkali solution shows slightly higher the higher injectivity to be secured for LSPF. Before
adsorption than the synthetic seawater and the polymer slug injection, the surfactant slug size of
low-salinity water, but the discrepancy is acceptable. 0.5 PV is designed to be injected. During the surfactant
The stability test of emulsion measures the separation injection with small slug size, oil recovery negligibly or
efficiency of water from emulsion system for the hardly increases. However, the succeeding polymer
low-salinity water and low-salinity and low-hardness flood produces immobile oil because of the prein-
solutions. Lower separation efficiency is observed for jected surfactant additive (Fig. 4.35) and reduces
the alkali solutions compared with the low-salinity wa- 717% of residual oil saturation. It is obviously
ter. It implies that the low-salinity and low-hardness concluded that low salinityeaugmented surfactant/
alkali solution generates more stable water-in-oil polymer flood has enough potential to produce the
emulsion. In addition, it results in less swelling of trapped oil by improving both displacement and
bentonite. With the favorable aspects of low-salinity sweep efficiencies. Synergetic effects between LSPF
and low-hardness alkali solution, higher oil recovery and LSSF can be secured through low salinitye
is obtained in displacement experiments compared augmented surfactant/polymer flood (LSSP) as well
with the waterflood and LSWF. as low chemical injection.
Wang, Ayirala, AlSofi, Al-Yousef, and Aramco (2018)
published the experimental attempts of LSSF for the car-
ALKALINE-SURFACTANT-POLYMER FLOOD bonate oil recovery. The connate water has salinity of
The chemical EOR has a huge potential to employ the 213.723 mg/L TDS, and the high-salinity water has
synergetic effects by incorporating the low-salinity wa- salinity of 57,610 mg/L TDS. The low-salinity water is
ter or smart water as the makeup brine. Although the prepared by diluting the high-salinity water by a factor
mechanism and effect of LSWF are not fully clarified, of 10. A sulfonated polyacrylamide and betaine-type
the LSWF obviously plays positive roles on the stability amphoteric surfactant are used. The contact angle and
of chemical, adsorption of chemical, formation dam- z-potential are measured to confirm the potential of
age, optimum condition for the chemical EOR, etc. wettability modification in low-salinity water condition
With the clear evidence of the synergy between LSWF for the specific carbonate rock. The reduction in contact
and single chemical EOR process, the coapplications angle and decrease toward more negative z-potential are
of alkaline, surfactant, and polymer flood to be com- observed in low-salinity water condition compared
bined with the LSWF are further investigated to enhance with the high-salinity water condition. These observa-
the synergy. tions consistently agree with the previous experimental
Previously, Johannessen and Spildo (2014) re- results of LSWF. It is evaluated that the LSWF modifies
ported an enhanced potential to reduce IFT by the the wettability of carbonate rock from oil-wet to weakly
LSSF and the higher oil recovery from sandstone core- oil-wet or intermediate wet. With the evidence of LSWF
flooding with the comparable capillary number effectiveness, the tertiary LSSP application is evaluated
improvement. In the coreflooding experiment, poly- and compared with the conventional surfactant-
mer slug injection is applied to support the LSSF. The polymer flood using high-salinity water as makeup