The lacustrine mud shale in Jurassic of Sichuan Basin is characterized by fast sedimentary phase transition

complex and diverse lithological combination types

and strong reservoir inhomogeneity

which is quite different from the marine shale. Therefore

it is of great significance to establish a typical geological section of Jurassic lacustrine shale in Sichuan Basin and further study the microfacies and lithologic assemblage characteristics of lacustrine shale. The Da'anzhai section of Fulu Town

Liangping District

Chongqing

Eastern Sichuan is selected as the research object. Through the division of small layers

fine description of sedimentary microfacies and lithologic combination characteristics

sample collection

field profile measurement

organic geochemistry

reservoir physical properties and whole rock X-ray diffraction

it is shown that the Da'anzhai section of Fulu town is mainly carbonate lake sediments. The microfacies and lithologic assemblages have three stages: initial transgression

maximum transgression and initial regression. The first and third members of the Da'anzhai formation are mainly composed of the microfacies of the thick layer mesoclastic limestone deposited in the bioclastic beaches of the carbonate shallow lake; The second member of Da'anzhai formation is a semi deep lacustrine subfacies. There are two microfacies: Storm beach and semi deep lacustrine mud. They are characterized by two lithologic associations

i.e. unequal thickness interbedding of grey clastic limestone and grey black shale

and thick black shale with thin shell limestone

With high content of brittle minerals and better permeability and compressibility

it is a sweet spot for shale oil and gas enrichment. Compared with the typical shale gas drilling

The semi deep lacustrine facies of the second member is mainly distributed in Fuling Jiannan area in eastern Sichuan

which is conducive to the formation of shale oil and gas. The carbonate shallow lacustrine clastic shoals of the first and third members are mainly distributed in Central Sichuan Northeast Sichuan

which is conducive to the enrichment of tight oil and gas.