A large set of dark grey to black colored mudstone and shale deposited in the middle to lower part of the upper
Sinian Doushantuo Formation in the middle Yangtze Platform，most of which are deeply buried in the Basin and with a good
shale gas resource potential. Based on drilling cores and outcrop section investigation，a systematical study on fundamental
geology was carried out. We also analyzed the sequence stratigraphy and sedimentary facies of the Doushantuo Formation，and
established regional stratigraphic framework. The lithology of the upper Sinian Doushantuo Formation is characteristic of four
different lithofacies，and the thickness of which is different in drilling cores and outcrop sections with variation ranges from 90
to 250 m. In general，the stratum is thickening along the direction of northwest to southeast. Doushantuo Formation was divided
into a second-order sequence（SS1），which contains four third-order sequences（SQ1、SQ2、SQ3、SQ4）. Sedimentary facies of
Doushantuo Formation were subdivided into tidal-flat and platform with three subfacies as open platform，shallow water shelf
and intra-platform basin respectively. In Doushantuo period，the sedimentary environments of Doushantuo Formation varied
from southeast to northwest as open platform and restricted platform in the study area，intra-platform basin face in the area of
Huajipo，Well X1 and Jiuliya.
