Low Salinity Waterflood (LSW) is an emerging Enhanced Oil Recovery (EOR) method that is simple to implement and has been shown to yield substantial increase in oil recovery over conventional waterflood, especially in oil-wet sandstone reservoirs. The mechanism for increased oil recovery is a wettability change from oil-wet to water-wet, which is induced by ion exchange between the injected fluid and the clay surface.
This paper presents the geochemistry that is required to model LSW and a method for shifting the relative permeabilities from oil-wet conditions to water-wet conditions. Excellent matches of core displacement data were achieved with a compositional simulator that incorporates those processes.
As ion exchange with the clay surface is important for the success of LSW, a method for modeling clay distribution and content based on facies is proposed. A new concept for LSW optimization based on well placement is introduced and demonstrated with reservoir simulation. As there are uncertainties associated with the geological modeling of the clay distribution, this paper shows how robust optimization can be applied to reduce uncertainties in the LSW optimization through well placement.