As a systematic study of the Wufeng-Longmaxi Formation was carried out by paleontological comparison

thin section identification

scanning electron microscopy and Nitrogen Adsorption Method in Qilong Village outcrop

Xishui

Guizhou Province

the following main insights are obtained: ① The Wufeng-Longmaxi Formation in Qilong Village outcrop is complete

and is conformable with overlying Silurian Shiniulan Formation and the underlying Ordovician Jianc

aogou Formation

with 12 graptolite biozones developed and without unconformity; ② Based on a variety of sedimentary fabric features

six major shale lithofacies in the Wufeng-Longmaxi Formation are determined; ③ The quartz content of the Wufeng Longmaxi Formation decreases

while clay minerals increase gradually from the bottom to the top in Qilong Village outcrop

which shows the content of brittle minerals decreases

and a decrease of fracability of the shale from the bottom to the top; ④ The organic matter types of Wufeng-Longmaxi Formation in Qilong Village outcrop are mainly of type Ⅰ and type Ⅱ

1

and the high TOC shale is mainly distributed in the Wufeng and lower Longmaxi Formation; ⑤ There is relatively low paleoproductivity of the Wufeng-Longmaxi Formation in Qilong Village outcrop. The high quality black shale was deposited in anoxic-dysoxic conditions

and high content of organic matter benefits from the high burial efficiency of organic matter; ⑥ The organic pores of the Wufeng-Longmaxi Formation in Qilong Village outcrop are mainly distributed in Wufeng and lower Longmaxi Formation

while organic pores were not developed in the upper member of Longmaxi Formation or Guanyinqiao member. The abundance of the small pores vertically decreases with stratigraphy upwards and The abundance of the large pore increases with stratigraphy upwards; ⑦ The natural gas adsorption capacity of the Wufeng-Longmaxi Formation in Qilong Village outcrop is a minimum of 1.62 m

3

/t

a maximum of 2.8 m

3

/t

and an average value of 2.13 m

3

/t. This shows that the larger the

TOC

value is

the stronger the corresponding adsorption capacity will be

and indicates organic matter content plays a decisive role in gas-bearing capacity of organic-rich shales.