A Review on the Progress of Ion-Engineered Water Flooding

Table 1

Summary of the investigation.

	Proposed mechanism	Reference	Experiments conducted	Conclusions drawn
1	Clay swelling and fines migration	Bernard [5]	Core flooding	Migration of fines plugs the flow channels and creates new channels. Profile modification on pore scale. Also clay swelling which squeezes out oil from pores.
2	Wettability alteration	Tang and Morrow [6]; Zhang and Morrow [7]	Imbibition test and core flooding	More diluted brine, the oil recovery being slower at initial stage and higher at final stage.
3	Various	Morrow et al. [8]; Morrow et al. [9]; Zhang and Morrow [7]; Agbalaka et al. [10]	Core flooding	With decreasing salinity, oil recovery increases.
4	Fines migration, MIE, EDL expansion	Austad et al. [11]	Zeta Potential Studies & Adsorption measurements	Initial chemical equilibrium is disturbed when LSW injected into the reservoir, which leads to detachment of oil from clay surface.
5	Wettability alteration, MIE	Lager et al. [3]; Mohanty and Chandrasekhar [12]	Core flooding	PDIs are the deriving ions in changing the wettability
6	Wettability alteration, fines migration	Yi and Sarma [13]	Core flooding, spontaneous imbibition	Rock can become more water wet by decreasing the salinity of brine or increasing the concentration. PDIs desorb carboxylic acids from rock surface.
7	Wettability alteration, MIE	Austad et al. [14]; Strand et al. [15]; Zhang and Morrow [7]	Contact angle measurements	MIE is the main mechanism behind increased oil recovery from low salinity water flooding.
8	Wettability alteration,	Yousef et al. [4]	Contact angle measurements, NMR studies. core flooding	Rock surface become more water wet by diluting injected sea water, 18% additional oil recovery after secondary stage with sea water.
9	Wettability modification	Romanuka et al. [16]	Capillary imbibition test	Higher oil recovery from injection of lower ionic strength brine.
10	Wettability alteration	Al Quraishi et al. [17]	Core flooding, zeta potential and contact angle studies	17% additional oil recovery after tertiary flooding with sea water. Contact angle dropped from 102° to 70° with 10 times diluted sea water.
11	Rock dissolution	Yousef et al. [18]	Core flooding, Zeta potential, NMR	Lowering Ca concentration of injected brine leads to calcium carbonate dissolution. As a result, the polar components of oil would be released from rock surface.
12		Mahani et al. [19]	Zeta-potential measurements, ICP-MS	With increasing pH, zeta potential is towards positive and with increasing salinity has less influence. Mineral dissolution exists with 25 times diluted SW.
13	Electric double layer effect	Ligthelm et al. [1]; Nasralla and Nasr-EL-Din [20, 21]	Zeta potential studies	By decreasing the pH of LSW, the electric charges of oil/brine and rock/brine surfaces changed from highly negative to close to zero value, which means that the expansion of EDL was reduced.
14	IFT reduction	Yousef et al. [4]	IFT studies	Salinity of injected brine has minor impact on the IFT and fluid-fluid interactions.
15		Al Quraishi et al. [17]	IFT studies	By diluting the brine up to 10 times, the interfacial tension between oil and brine reduced to only 6 units which is insignificant.