Experimental investigations and field applications showed an increase in oil recovery by using low salinity water injection. The mechanisms leading to the increase in oil recovery by low salinity water injection are debatable. Furthermore, low salinity water injection requires relatively fresh water to dilute sea water which is not available in many areas around the world especially the Arabian Gulf region. Using low salinity water as an enhanced oil recovery process is a costly process because it requires a lot of fresh water to dilute the sea water.

In this study we introduce an economic and new chemical enhanced oil recovery fluid capable of recovering additional oil from sandstone reservoirs after the primary water flooding stage. The new chemical enhanced oil recovery fluid utilizes high pH chelating agents at low concentrations prepared in sea water without any dilution. Coreflood experiments were performed using Berea sandstone cores at 100°C to test the effectiveness of this new EOR fluid system.

The results of the coreflooding experiments showed that the new fluid system is able to recover additional oil up to 30% from the initial oil in place after sea water flooding. Zeta potential measurements were performed using the new fluid system and crushed Berea cores to identify the mechanism leading to this additional oil recovery. The results of the zeta potential revealed more negative values for the new system more than the sea water and low salinity water, confirming that the rock wettability is altered to a more water-wet condition. This changed in rock wettability could be due to rock dissolution and the chelation of the different ions such as calcium, magnesium and iron ions. The new fluid system very attractive as its cost is low compared to the cost of diluting the sea water in the case of low salinity water flooding.

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