Effect of mixed wettability of tight reservoirs on the pore scale imbibition law
The imbibition predicated upon the capillary pressure,can effectively produce the oil and com-plement the formation energy.In order to explore the relationship between the mixed wetting percent-age and the imbibition recovery,as well as the imbibition law in the typical mixed wetting pore-throats,the pore scale imbibition numerical model is established based on phase field theory and Navier-Stokes e-quation.A series of numerical simulations of pore scale imbibition processes are conducted to analyze of the influence of different mixed wetting degrees on imbibition oil recovery.Results indicate that the im-bibition recovery of core with the mixed wetting of 10％is higher than that of pure water-wetting sys-tem.For the low mixed wetting percentage,the mixed wetting pore-throats are also the main channel for imbibition oil recovery,whose imbibition effect is the similar as that of the water-wetting channel.When the mixed wetting percentage exceeds 40％,the imbibition recovery is less than 10％,resulting in the poor imbibition effect.For the high mixed wetting percentage,the well-connected and contiguous water-wetting pore-throats become the main advantageous channel for imbibition,while the continuous oil wetting pore-throats hinder the fluid flow,inducing the cessation of the imbibition.The results eluci-date the imbibition mechanism and flow potential of mixed wetting degree and mixed wetting distribu-tion,which is of great significance for improving the recovery rate of tight oil reservoirs.
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