微CT扫描重建低渗气藏微观孔隙结构——以新场气田上沙溪庙组储层为例

Reconstruction of microscopic pore structure in low permeability gas reservoirs by micro-CT scanning:an example from the Upper Shaximiao Formation in Xinchang gas field

为了提高气藏采收率,从微观孔隙结构出发,建立孔隙网络模型,定量描述孔隙微观尺度上的渗流机理。以川西新场气田上沙溪庙组岩心为例,开展孔隙结构三维重构研究。首先采用微CT技术对岩心进行扫描获得投影数据,采用FDK算法重建岩心灰度图像,然后以宏观孔隙度为基础利用二值分割法分割灰度图像,最后使用光线跟踪算法得到三维孔隙结构图像,即数字岩心。对数字岩心的相关性质进行统计分析,得到的数字岩心孔隙度与岩心实验孔隙度基本一致,相对误差约为0.1。这一数值与新场气田上沙溪庙组储层物性相吻合,说明微CT扫描法重构微观孔隙结构是可行的。该研究为建立孔隙网络模型及开展后续微观渗流模拟研究奠定了基础。

In order to enhance gas recovery,it is necessary to construct pore network model and quantitatively describe micro-pore-scale percolation mechanism based on micro-pore structure.Taking cores of the Upper Shaximiao Formation in the Xinchang gas field of western Sichuan Basin as an example,this paper studies 3D reconstruction of pore structure.First,using micro-CT to scan core to get projection data,and using the FDK algorithm for construction of grayscale images.Then based on experimental porosity,using 2-value segmentation to cut grayscale images and using ray tracing algorithm to get 3D pore structure image（digital core）.Statistical analysis of the properties of digital core shows that the porosity of digital core is almost identical to the measured core porosity with a relative error of only 0.1,which is in coincide with the properties of Upper Shaximiao Formation in the Xinchang gas field.It shows that reconstruction of micro pore structure with micro-CT scanning is feasible.The study provides a solid foundation for pore network modeling and subsequent microscopic flow simulation study.