Research On The Imbibition Under Low Frequency Vibration In Low Permeability Reservoir

Spontaneous imbibition is an important water-flooding mechanism in the Fractured-low-permeability sandstone reservoir,and the key to improve the efficiency of water-flooding is increasing recovery of matrix-imbibition.In this paper,experiment on research of imbibition effect in the condition of low frequency vibration was conducted to determine the effect of vibration parameters such as frequency,amplitude,duration and other factors on the imbibition under the low frequency resonance vibration.Using the natural low permeability sandstone samples with similar property.The experiment results show that low frequency vibration is an effective way to improve the imbibition recovery of matrix of low permeability sandstone.And in the similar cores,there is an optimal frequency vibration in which the increased range of imbibition recovery is up to the peak,(in this paper,the optimal frequency is 30Hz,the optimal accelerate is 1.0 m/s~2,and the optimal duration is 8 hours in the experiment.Besides,Continuous waves is propitious to increase the imbibition recovery percentage.)And in all factors,frequency and acceleration are two dominative factors which have the most dramatically influence on ultimate recovery growth.The result of the movable fluid distribution range,demarcated by NMR,of vibration auxiliary imbibition and spontaneous imbibition,reveals that vibration not only improves the movable fluid variance,but increases the movable fluid flow range as well.Imbibition recovery percentage can be increased by 8%~14%in the condition of the optimal wave parameters,and the interconnected pores area with the radius of pore throat greater than 1.0?m is the main area to increase the imbibition recovery.Based on single capillary model,the analysis of speed difference of the oil-water two phase in capillary under the effect of capillary force and under the action of sine wave was conducted,and the conclusion that periodic change of fluid velocity fluctuation is help to lift the end of the capillary effect and increase fluid discharge of oil volume in the tube,thereby improve the spontaneous permeability recovery degree was also drawn.In addition,the model based on oil droplets was analysed and the force equilibrium equations was established to approach the remarks that the wave can improve the falling-off rate of oil droplets adhesive on the wall of fractal,and improve the dynamic fracture imbibition recovery degree.