基于微纳米CT技术的化学驱后微观剩余油定量描述

Quantitative Description of Microscopic Remaining Oil after Chemical Flooding Based on Micro-nano CT Technology

利用微纳米CT技术及室内岩心驱油实验,对岩心微观孔隙结构进行三维重构,研究水驱后和化学驱后微观剩余油的分布特征、赋存状态,定量描述不同尺寸孔隙内微观剩余油饱和度,明确不同驱油体系对微观剩余油的动用程度。结果表明:水驱后转聚合物驱的剩余油饱和度为22.3%,水驱后转二元复合驱的剩余油饱和度为18.4%,水驱后转非均相复合驱提高采收率效果明显,最终剩余油饱和度为12%。经三维重构后可以直观地看到不同驱油体系后微观剩余油的分布特征。化学驱后不同孔径内的剩余油饱和度均有所降低,大于25μm孔径内的剩余油动用效果明显,聚合物驱动用程度为66.7%.二元复合驱动用程度为75.7%、非均相复合驱动用程度为85.5%。聚合物驱和二元复合驱对孔径5μm以下孔隙内的剩余油动用程度较低,分别只有19.3%和35.9%;非均相复合驱对小于5μm孔径内的剩余油动用程度达到52.5%。非均相复合体系具有扩大波及体积和降低界面张力的双重作用。

Micro-nano CT technology and laboratory core oil displacement experiments are used to reconstruct the microscopic pore structure of the cores in three dimensions.The distribution characteristics and occurrence status of the microscopic remaining oil after water flooding and chemical flooding are studied and the micro scopic remaining oil saturation in the pores of different sizes is quantitatively described.The producing degree of various oil displacement systems on the microscopic remaining oil is known.The results show that the re maining oil saturation of polymer flooding is 22.3%after water flooding,that of polymer/surfactant binary flooding is 18.4%after water flooding,and that of heterogeneous composite flooding is 12%after water flood ing with the best effect of enhancing oil recovery.After three-dimensional reconstruction,the distribution char acteristics of microscopic remaining oil by different oil displacement systems may be clarified intuitively.After chemical flooding,the remaining oil saturation in different pore sizes has reduced.The remaining oil saturation in pores flooding,and heterogeneous composite flooding is 66.7%,75.7%,and 85.5%respectively.The remain ing oil in pores with a diameter of less than 5μm is less produced by polymer flooding and polymer/surfac tant binary flooding,and the producing degree is only 19.3%and 35.9%respectively.After the heterogeneous composite flooding,the remaining oil in pores with a diameter of less than 5μm is produced by 52.5%.The heterogeneous composite system has the dual effects of expanding the swept volume and reducing the interfa cial tension.