A study on core spontaneous imbibition behavior via nuclear magnetic resonance and displacement experiments

Abstract

ABSTRACT Spontaneous imbibition is auniversal phenomenon in nature, which plays asignificant role in the two-phase flow of gas reservoirs with water. To quantitatively evaluate the spontaneous imbibition behavior of tight sandstone gas reservoirs, this paper conducts experiments on cores with different imbibition times based on core imbibition experiments, combined with nuclear magnetic resonance (NMR) and displacement experiments. In this paper, some significant findings were obtained by the imbibition experiments and NMR, which mainly included the T2 spectral response of spontaneous imbibition and the relationship between threshold pressure gradient (TPG) and water saturation. Homogenous propulsion of water through the macropores which are about 0.5 μm and the effective permeability has decreased by 70–80%. Displacement experiments proved that the threshold pressure phenomenon existed in the imbibition cores, the longer the imbibition time, the higher the water saturation, and the bigger TPG. After the dimensionless treatment, there is apositive linear correlation between TPG and water saturation. The results of this research play an important role in the study of percolation laws of agas reservoir with water and distribution characteristics of residual gas.