Abstract:

The Eopaleozoic shale in South China is assessed as the preferred target for shale gas exploration and development in China, and the research on its organic matters is imperative.Some shale samples are taken from the Eopaleozoic such as the Lower Cambrian, Upper Ordovician and Lower Silurian in Anhui, Guizhou and Sichuan provinces in South China.The naturally fractured surfaces(perpendicular to or parallel to the beddings)and the argon ion milled surface are prepared from these shale samples.Under the scanning electron microscope(SEM)with field emission, the maceral, che-mical composition, occurrences of the organic matters and pore types are systematically observed and studied.The results show that the organic maceral types are dominated by bituminite and bacteria and algae body with strong potential of hydrocarbon generation.The bituminite is composed of spherulites with several to dozens of nanometers in diameter with stripped, interstitial, thin films and amorphous occurrences.The bacteria and algae body has obvious characteristics of biological morphology, mainly in clastic form and dozens of micrometers in diameter.On the basis of identification of maceral, the genetic types of the organic pores are classified into biological pore, vesicular pore, bitum-spherulite pore and molded pore.And both the vesicular pore and bitum-spherulite pore occur in the interior of bituminite and their diameters are of nanometer-scale, which are the direct evidences of hydrocarbon generation from organic matters.Therefore, the development degree of these pores is viewed as one of the indexes for hydrocarbon generation potential assessment of the source rocks.

Key words: maceral, pore type, SEM, organic matter, Eopaleozoic, shale