South China

where develops several sets of marine organic-rich shales

is an important area for shale gas E & D.Compared with North America

the marine organic-rich shales in southern China have the characteristics of old geologic age

high maturity

multi-episodic tectonic movements

complex surface conditions

complicated earth stress state and large differences of preservation conditions.In comparison with the Longmaxi shale that has achieved a breakthrough in shale gas exploration and development in Sichuan Basin and its periphery

the Lower Cambrian Niutitang shale has an older age

greater particularity and complexity and higher requirement to preservation conditions.On the basis of the geological conditions of the complex structure areas in southern China

the preservation conditions of the Niutitang shale in the Cen'gong block were analyzed through precise seismic interpretation

tectonic evolution

material foundation

cap rocks

reservoir pressure

and component of natural gas and aquifers.The results indicate that late tectonic reconstruction dominated by denudation and faulting is the major factor leading to the dissipation of shale gas.The tectonic evolution of the study area has the characteristic of "moderate early uplifting

long-term stability and intensive late reformation".Besides

NE-NNE-trending trough-like folds

high dip-angle thrust faults and strike-slip faults are well-developed in the study area

and the central wide and gentle structure zone has less faults

moderate buried depth and good preservation conditions.In addition

the component of the natural gas and strata water shows that the superior roof

floor and regional cap rocks can effectively retard the gas dissipation and strata water invasion.Finally

an evaluation index system of structural preservation conditions is put forward and applied to identify the favorable preservation zones in the Cen'gong block.