Reserve - estimation statistics show the significance of oil carbonate reserves. Water injection is deemed to be the most successful and widespread secondary recovery method.
The LoSal (low salinity) is a well-established and proved technique for water flooding applied in sandstone rocks to enhance the recovery efficiency for such reservoirs; this method tailors the water salinity degree to extract the highest amount of STOIIP. On the other hand, a few lab experiments subjected to carbonate rocks whether dolomite or limestone.
The research deals with carbonate rocks where - in most real case histories-water flooding fails due to many reasons; however the most common reason is fractures existence in the carbonate rocks.
The research applied water injection for eight carbonate (limestone) core samples extracted from an Egyptian offshore oil field near Gulf of Suez.
Water salinity was tuned three times; three different water salinity to investigate the effect of different water salinities on (1) Residual oil saturation, (2) Recovery Efficiency and (3) relative permeability curves.
Results showed for majority of core samples a decrease in residual oil saturation (Sor) with decreasing water salinity and increase in recovery efficiency (Er).
Results showed from relative permeability curves that mostly enhancement was due to wettability modification or alteration as shown.
Also, results show that there is no clear relationship between applied differential pressure or absolute permeability and residual oil saturation and recovery efficiency. However, low pressure differential (1.5 psi) is enough to afford adequate injection rates of water into the core samples. The results obtained are analyzed through relative permeability curves.
That is achieved through:
Residual oil saturation
Recovery efficiency
Wettability alteration or modification; from relative permeability curves.
Water flooding- as a mean of secondary recovery method for pressure maintenance-dates backs up early as 1865, the use of water flooding as a recovery method did not come into widespread acceptance and use until the early 1950's. In the west Texas, there was a significant expansion of the oil industry in the 1950's with the discovery of a number of very large fields such as Wasson, Slaughter, Levelled, North and South Cowden, Means and Seminole.
