致密砂岩微米级孔隙网络系统石油驱替实验三维在线模拟

致密油储层孔隙度和渗透率均较低，其微米级孔隙网络系统内石油赋存状态是致密油成藏地质研究中亟待解决的核心问题之一。采用油气驱替系统与X射线微米CT扫描系统联用，通过对3 mm和5 mm直径致密砂岩干岩心、饱和碘化钾（KI）溶液及油驱替KI溶液后致密砂岩岩心在线CT扫描及数据重构，三维展示了致密砂岩微米级孔隙网络系统中石油的赋存状态。研究发现孔隙半径10 μm以上孔隙的连通性较好，是石油聚集的优势孔隙网络系统，致密砂岩62.9%~84.1%的石油聚集于半径在10~60 μm之间的孔隙内；孔隙半径小于10 μm的孔隙数量多，但其在空间上多呈孤立状分布，该部分孔隙的石油充满度较低，只聚集了致密砂岩内6.8%~20.0%的石油。致密砂岩含油饱和度随孔径呈阶梯状增长，半径小于10 μm、10~60 μm和60~80 μm的孔隙的含油饱和度分别为10%~40%，30%~75%，40%~75%。致密砂岩微米级孔隙网络系统石油的赋存与孔隙的尺寸、成因类型及空间分布特征有关。 

Three-dimensional simulation of oil distribution during waterflooding in a micrometer-sized pore network system of tight sandstone

The porosity and permeability of tight oil reservoirs are quite low.The occurrence of oil in tight oil reservoirs,which are composed of a micrometer-sized pore network system,is one of the most important scientific issues to be solved in tight oil research.Oil was removed from two tight sandstone core samples(with diameter 3 mm and 5 mm)which were saturated with KI and oil and monitored by core flooding system using X-ray Micro-CT,to display the occurrence and accumulation characteristics of oil in the micrometer-sized pore network.Pores with radius larger than 10μm have good connectivity and comprise the dominant pore network system for oil accumulation,while 62.9%-84.1%of the oil accumulates in pores with radius from 10-60μm.Pores with radius smaller than 10μm are huge in number;however,most of them are isolated in space,the oil saturation of these pores is low and they only gathered 6.8%-20.0%of oil in tight sandstone.The oil saturation of tight sandstone increases in three steps with pore radius in the range of 10%-40%for pores with radius smaller than 10μm,30%-75%for pores with radius 10-60μm,40%-75%for pores with radius 60-80μm.The occurrence of oil in micrometer-sized pore network systems in tight sandstones is controlled by the size,origin and spatial distribution of pores.