Hydrogeochemical characteristics of Yingcheng Formation in Changling Fault Depression and its petroleum geologic significance

The conventional chemical composition and trace element characteristics of oilfield water from main exploratory wells of the Yingcheng Formation in Yaoyingtai-Chaganhua area in the Changling Fault Depression were analyzed.The NaHCO₃ type water accounts for 80% of water samples.The CaCl₂ type water mainly distri-butes around wells YS1 and YS2.ρ(HCO₃^-),total salinity (TDS),and desulfurization coefficient (rSO₄^2-×100/rCI^-)are well consistent with each other.High TDS area corresponds to low desulfurization coefficient,indicating for good sealing capacity and slow water exchange,which are favorable for petroleum accumulation and pre-servation.The high content of K is a sign for good permeability reservoir.The high content of Ba reflects a strong reducing environment and may be more favorable for natural gas preservation.In brief,combined with tectonic activity,the hydrogeochemical characteristics of formation water can be used to effectively judge the conditions for petroleum accumulation and preservation.