Experimental study on the existence of nano-scale pores and the evolution of organic matter in organic-rich shale

Abstract

To explore the characteristics of nanopores in organic-rich shale, the shale of the Upper Yangtze area under different maturity are studied. Scanning electron microscopy (SEM), low temperature nitrogen experiment (LP-N2-GA) and the Frenkel-Halsey-Hill (FHH) fractal model were used. Results show that the intergranular pores and organic pores are most developed, and the pore size is distributed from a few nanometers to several tens of micrometers. The SEM gray scale images make the pore development characteristics of shale be observed more intuitively. Based on the results of low temperature nitrogen adsorption test and FHH fractal model, the results show the fractal dimension of shale is positively correlated with TOC and quartz, but negatively related to clay minerals and feldspar. There is a good relation between maturity and pore volume.With releasing of pressure, the pore evolution gradually returns to the normal compaction trend, and the pore volume of the shale decrease.

Keywords

• shale
• nano-pore
• pore evolution
• maturity