ELEMENT GEOCHEMISTRY CHARACTERISTIC RESPONSE FOR KARSTIFICATION IN THE TAHE OILFIELD

The Tahe Oilfield is located in the southwest margin of Akekule Uplift in north Tarim Basin.It went through several times tectonic uplift from the late Caledonian to the early Hercynian,this lead to Ordovician carbonate formation be exposed to the surface for a long time and suffering from intense air fresh-water weathering,leaching and dissolving and developed a set of complicated superficial karst system.Throuth research of arenaceous and pelitic karstic cave deposit about its' trace element such as B,V,Ga,Rb,etc,and REE characteristic in the main region of the Tahe Oilfield,it indicated that most samples took on characteristic of fresh-water corrosion.While,samples of the four wells such as T615 showed influenced by seawater,it can be indicated that seawater-freshwater mixing corrosion caused by widely marine transgression in early of Carboniferous Period probably overlay and improved the Ordovician karst system in the Tehe Oilfield.