By the observation of the organic microscopic composition and scanning electron microscopy of the whole rock

the black shale of the Upper Ordovician Wufeng-Lower Silurian Longmaxi formation in Pengshui and its adjacent core wells Microscopic observation

classification and research of hydrocarbon-forming organism systems. It is found that the main hydrocarbon-forming organism types of shale in Pengshui and its adjacent areas are alginite（phytoplankton

suspected sources

benthic algae

etc.）

animal debris（graptolite

radiolarian

chitinozoa and foraminifera） and bacteria

etc. Among them

the main hydrocarbon-forming organisms in organic-rich shale in Wufeng-Longmaxi formation（

TOC

≥2.0 %） are phytoplankton

suspecte

d sources

bacteria

graptolite

etc.

which have high abundance and differentiation. Hydrocarbon-forming organisms are the main source of oil and gas

meanwhile

the organic pores formed after its complex thermal evolution are the main carriers of shale gas occurrence. As there is a good coupling relationship between source and reservoir in the organic-rich shale section of Wufeng-Longmaxi formation

it is supposed to be the best geological sweet spot layer.