Аннотации:
In this paper, the effects of salinity and active ions on wettability alteration in carbonate
reservoirs with different initial wettability conditions with implications in smart water flood design,
optimization, and performance analysis are experimentally investigated. Contact angle measurement
was used as the main tool to study the alteration in wettability. Other analytical techniques such
as pH measurements along with energy-dispersive X-ray spectroscopy (EDS) were used to support
the analysis. Initial wettability of the tested carbonate samples ranges from strongly water wet to
preferentially water wet, neutral wet, oil wet, and strongly oil wet (5 cases or groups) condition.
Four different synthetic brines, namely high salinity (Hsal), low salinity (Lsal), and smart waters 1
and 2 (SW1 = a Mg brine, and SW2 = a Mg and sulfate brine) were prepared and used by adjusting
the salinity and ion concentration to study their effects on wettability alteration. Low-salinity brine
(Lsal) proved to be more effective than high-salinity brine (Hsal) for the wettability alteration of calcite
surfaces at intermediate (neutral) or oil-wet conditions. The smart brine containing only the Mg2+ ion
(SW1) was able to alter the wettability of calcite surfaces in intermediate or oil-wet states. The sulfate
ion played a catalytic role in wettability alteration by the magnesium ion, and the process was faster,
as indicated by higher wettability alteration index values. High-salinity brine (Hsal) is a good choice
for design of water floods in reservoir rocks with initial wettability in the range of strongly water
wet to neutral wet conditions. In the wettability alteration process of oil-wet samples, brine with a
high magnesium ion concentration was slower than brine containing high concentrations of both
magnesium and sulfate ions. This can be attributed to the catalytic role of the sulfate ion compared
to that of the magnesium ion. Finally, the results showed that the initial wettability of the reservoir
rock plays a major role in design of a proper water flood to maximize oil recovery from carbonate
reservoirs. The results obtained from this research work suggests that some effective smart water
flooding scenarios can be developed and executed incorporating different smart brines to manage
the reservoir rock wettability and maximize the oil recovery from carbonate oil reservoirs.