非常规油气储集孔隙多尺度连通性的定量显微CT研究

Quantitative and Multi-Scale Characterization of Pore Connections in Tight Reservoirs with Micro-CT and DCM

非常规油气储集孔隙结构复杂多样,以纳米级孔喉系统为主,局部发育毫米-微米级孔隙和裂隙。孔、裂隙大小、形态及三维连通性等微观结构特征对油气赋存状态、运移方式、渗流特征等地质问题研究具有重要意义。常规方法无法实现微纳孔隙多尺度三维结构及连通性分析。本文采用同步辐射多能CT技术,结合数据约束模型(DCM)方法对非常规油气储集微纳孔、裂隙研究,可实现多尺度三维可视化表征,进一步获得孔、裂隙体积统计分布及其三维连通结构等信息。基于上海光源显微CT实验平台,针对碳酸盐岩及陆相页岩两种样品,成功获得了孔、裂隙三维结构以及统计分布、三维连通结构等定量信息。实验结果表明,该方法有望成为非常规油气储集研究强有力的手段。

The pore structures,whose sizes range from millimeters to micro-or even nano-meters,are complex in unconventional tight oil and gas reservoirs. Quantitative understanding of size,shape,distribution and connections of pores are important in estimating the relationships among total reserve,recoverable reserve and production rate. However,it has been a challenging task to adequately obtain 3D pore structures and interconnections at present due to the inherent multiscale characteristics of pores. In this paper,the technique of data-constrained modeling（DCM） combined with multi-energy synchrotron radiation-based X-ray CT was used investigate the pore and fracture connectivity in unconventional oil and gas reservoirs. This method can obtain the micro-CT data for multi-scale pores and fractures and thus can obtain pore-size distributions and connections. The CT experiments were performed on limestone and shale samples in the Shanghai Synchrotron Radiation Facility and quantitative 3D structures,size distributions and connections of the pores and fractureswere successfully obtained via DCM analyses,indicating that CT combined with DCM is a powerful tool for characterizing unconventional（tight） reservoirs.