特低渗透储层微观孔隙结构参数对渗流行为的影响——以鄂尔多斯盆地长6储层为例

通过压汞和渗流实验对鄂尔多斯盆地长6特低渗透储层岩心进行了孔喉结构和渗流实验研究。压汞实验表明,研究区曲线类型总体上属于B类和C类;曲线偏向图的右上方分布,中间过渡段相对较陡,进汞曲线和退汞曲线夹角较小;门槛压力和中值压力高,分选性一般;孔喉半径对渗透率的贡献由单一区域向多区域均有分布;门槛压力、中值压力等与渗透率具有良好的相关关系,但退汞效率和退汞饱和度与渗透率相关性较差。单相渗流实验表明,部分样品在低压力梯度时具有非达西渗流特征,并过渡为达西渗流;两相渗流实验结果表明,储层具有高束缚水饱和度、高残余油饱和度,两相共渗区较窄的特征。

Effect of Micro-Pore Structure Parameter on Seepage Characteristics in Ultra-Low Permeability Reservoir:A Case from Chang6 Reservoir of Ordos Basin

Based on mercury pressure and seepage experiments for the Chang6 reservoir rock with the ultra-low permeability in the Ordos basin,we discuss the pore-throat structure and seepage.Results of the mercury pressure experiments indicate that the capillary pressure curve is composed of B and C types.They are distributed in the up-right direction of typical patterns,with a higher pitch of parallel reach and a low angle between mercury-injection curve and mercury-ejection curve.Mercury pressure vaulues for threshold pressure and middle pressure are high,suggesting moderate grain sorting.The contribution of pore-throat structure to permeability exists both single and several areas.There is a good correlations among permeability,threshold pressure value,and middle pressure value,but a weak correlation among permeability,mercury-ejection efficiency,and mercury-ejection saturation occurs.The single phase experiment indicates that non-darcy seepage for few samples exist when pressure gradient is low and change into darcy flow at high pressure.Two-phase experiment suggests that the reservoirs would have the high saturation of absorbing water and residual oil,associated with the small seepage areas both water and oil phase.