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摘要
This work investigates the use of scanning electron microscopy (SEM), low-field nuclear magnetic resonance (NMR) relaxation, and mercury intrusion capillary pressure (MICP) to reveal the pore size distribution (PSD) characteristics of shales. The comparisons were conducted using six shale samples from the Dongying Depression, Bohai Bay Basin, China. The results show that SEM can effectively reveal the PSD of shale but cannot detect micropores (<100 nm in diameter) smaller than the imaging resolution or selected macropores if a smaller region of interest (ROI) with a higher resolution is used. Two limitations of MICP were addressed. First, high-pressure intrusion by mercury might either deform or destroy the skeletal porous structure of shale due to the compressibility of the clay minerals and the nanopore system. Second, pore-shielding effects can induce high uncertainty in the MICP PSD results. The large pores are shielded by access to small pores, and thus, the volume of small pores obtained from the MICP test consists of actual small pores and those large pores controlled by small pores. Thus, pore-shielding effects obviously underestimate the meso- and macropore volumes and simultaneously overestimate the intrusion volume of the micropores, particularly if shale contains a small amount of quartz. Thus, the pore scale of shale might be underestimated by MICP. After comparison of the PSD results via SEM imaging, NMR relaxation, and MICP, it was found that NMR relaxation is an efficient tool for nondestructive and quantitative evaluation of shale pore size.
- 出版日期2017-9
- 单位中国石油大学（华东）
