Investigation effect of wettability and heterogeneity in water flooding and on microscopic residual oil distribution in tight sandstone cores with NMR technique

Abstract

Abstract In order to explore the effect of wettability and pore throat heterogeneity on oil recovery efficiency in porous media, physical simulation experiment and nuclear magnetic resonance (NMR) measurements were conducted to investigate how crude oil residing in different sized pores are recovered by water flooding. Experimental results indicate that the recovery factor of water flooding is governed by spontaneous imbibition and also pore throat heterogeneity. It is found that intermediate wetting cores lead to the highest final recovery factor in comparison with water wet cores and weak oil wet cores, and the recovery oil difference in clay micro pore is mainly because of the wettability, the difference in medium pore and large pore is affected by pore throat heterogeneity. Water wet core has a lower recovery factor in medium and large pore due to its poor heterogeneity, in spite of the spontaneous imbibition effect is very satisfying. Intermediate wetting cores has significant result in different sized pore and throat, the difference in medium pore and large pore is affected by pore throat heterogeneity.