The criteria for an acceptable formation watercut level in the western Sulige gasfield in Ordos Basin can be summarized as salinity≥50g/L

sodium-chlorine ratio<0.5

sodium-calcium ratio<1 and fracturing fluid flowback rate≥100%.Based on a comprehensive analysis of water formation chemical characteristics

hydrogen and oxygen isotopes as well as trace element "Br"

the paper concludes that the formation water in the western Sulige gasfield was of continental sedimentary origin and experienced extensive water-rock interaction and evaporation processes.The analysis also indicates that sealing condition for the formation water in the Upper Paleozoic is good

thus which is favorable for gas accumulation and preservation.Further analysis in combination with consideration of hydrocarbon accumulation elements such as source rocks

reservoir and cap rocks reveals that the formation water is residual water from the process of weak dynamic hydrocarbon accumulation.The complicated gas-water distribution pattern is caused by reservoir heterogeneity and microstructures on the background of low hydrocarbon-generating intensity and low tectonic position.The formation water of high salinity in the eastern Ordos Basin is suggested to be related to the water-rock process of the Ordovician salinastone.