Experimental investigation of different brines imbibition influences on co-and counter-current oil flows in carbonate reservoirs

Imbibition of water,as wetting phase in oil-wet fractured carbonate reservoirs,plays a key role in fluid flow between matrix and fracture system.The type of injected seawater and its chemistry would profoundly influence the imbibition process.In this study,the impact of smart water(a brine that its ions have been adjusted to facilitate oil recovery)and low salinity water on co-and counter-current imbibition processes for oil-wet carbonate cores has been experimentally investigated.The results show an increase of about 10% in oil recovery for co-and counter-currents for smart seawater imbibition compared to that of low salinity seawater.In addition,as a result of the influence of co-and counter-current on each other,by co-current removal from one core face,the countercurrent in the other face would be intensified by as much as about 75%.A close examination of different lengths(5,7 and 9 cm)of carbonate cores with the same permeability revealed that by decreasing porous medium length,the amount of counter-current producing oil would be decreased so that in the 5 cm core,counter current oil production will not happen.For similar core lengths by increasing permeability,the share of counter current flow would be decreased approximately 18% since the capillary pressure could not overcome non-wetting phase viscous forces.Considering the role of matrix length along with a modified brine(which is designed according to the matrix mixture)strengthen the relevant mechanisms to have more oil production so that the higher thickness of matrix causes the higher amount of co-current oil producing and consequently more total recovery.

Impact of solutal Marangoni convection on oil recovery during chemical flooding

In this study,the impacts of solutal Marangoni phenomenon on multiphase flow in static and micromodel geometries have experimentally been studied and the interactions between oil droplet and two different alkaline solutions(i.e.MgS04 and Na_2 CO_3) were investigated.The static tests revealed that the Marangoni convection exists in the presence of the alkaline and oil which should carefully be considered in porous media.In the micromodel experiments,observations showed that in the MgS04 flooding,the fluids stayed almost stationary,while in the Na2 C03 flooding,a spontaneous movement was detected.The changes in the distribution of fluids showed that the circular movement of fluids due to the Marangoni effects can be effective in draining of the unswept regions.The dimensional analysis for possible mechanisms showed that the viscous,gravity and diffusion forces were negligible and the other mechanisms such as capillary and Marangoni effects should be considered in the investigated experiments.The value of the new defined Marangoni/capillary dimensionless number for the Na2 C03 solution was orders of magnitude larger than the MgS04 flooding scenario which explains the differences between the two cases and also between different micromodel regions.In conclusion,the Marangoni convection is activated by creating an ultra-low IFT condition in multiphase flow problems that can be profoundly effective in increasing the phase mixing and microscopic efficiency.