Abstract:

To provide data for the reservoir evaluation of the lower Silurian organic-rich shales in the Lower Yangtze Region, in this
study we analyze the characteristics of pore structures of the shales based on the study of samples from the LunShan 5 well in the
Ningzhen Area. Comprehensive methods were employed, mainly including field emission scanning electron microscopy (FE-SEM),
small angle X-ray scattering (SAXS) and low-temperature nitrogen adsorption(LT-N2GA). Results indicate that the pores in the shales
are generally nanoscale and can be classified into four types in general, i.e., organic pores, interparticle pores, mineral matrix pores and
microfractures. The interparticle pores dominate among these multiple types of pores. The pore size distribution of the shales are
complex, as mesopores (2~50 nm) were distributed most widely and some micropores (＜2 nm) and macropores (＞50 nm) have also
been observed. In terms of the controls of the pore size distribution of the shales, we conduct a correlation between pore volume and
brittle minerals (e.g., quartz, pyrite and albite) contents, clay contents and TOC. It is implied that mineral compositions are the primary
control, contents of brittle minerals and clay minerals also play a certain influence (especially for micropores and mesopores), whereas
TOC has the least impacts.

Key words: Ningzhen Area；Gaojiabian Formation；field emission scanning electron microscopy(FE-SEM)；small angle X-ray scattering(SAXS)；low-temperature nitrogen adsorption(LT-N2GA)；pore structure.