Significant progress has been made in the exploration and development of shale gas in the Wufeng-Longmaxi Formation of Sichuan Basin

but shale gas content varies greatly among different well locations. Through the analysis of formation water salinity

geochemical index and formation water type in Well-PY1 HF

Well-JY1 HF

Well-NY1 HF

Well-LY1 and other wells in Southeastern Chongqing

it is found that CaCl2 water type reflects good shale gas preservation conditions

while the water types of NaHCO3 and Na2 SO4 reflect formation water and atmospheric water are interconnected to different extent

leading to a relatively poor preservation condition. Based on the characteristics of large-scale faults and residual syncline structures developing in Southeastern Chongqing and the formation water characteristics of Wufeng-Longmaxi Formation

the groundwater seepage mode can be divided into two types: the infiltration type in the large-scale fault development area and the centripetal flow type in the residual syncline area

corresponding to different shale gas preservation conditions. In the area with large-scale faults

the surface water infiltrates deeply along the faults

causing great damage to shale gas reservoir

most of them contain few gases. The formation water in the residual syncline is centripetal flow

and the deep part of the syncline is relatively well preserved. The surface water and the formation water form a free alternating zone at the syncline edge

and the preservation condition of shale gas reservoir is poor

thus the gas bearing property is poor. In the core part of the syncline

the closer to the core part

the weaker the influence of atmospheric water infiltration is

and the better the preservation condition will be.