Geosciences Center��CNPC Greatwall Drilling Corporation��Beijing 100101��China

Analyzing the stratigraphic characteristics of the Arys oilfield and South Arys structure��the authors identified four marker beds based on the logging data��and considered that the Akshabluk Formation was distributed in a relatively stable conditions in Cretaceous and Late Jurassic��which was used detailed comparison of geological characteristics in sublayers level�� Meanwhile��the authors considered that the Akshabluk Formation was unconformable with its underlying Kumker Formation��which should be the residual formation of Middle-Lower Jurassic�� Moreover�� the authors analyzed the stratigraphic relation of the corresponding layers of the South Arys structure��which showed that the unconformity was existed between the Akshabluk Formation and Kumker Formation��indicating the fact of unconformity between the Akshabluk Formation and its underlying Jurassic strata in Arys oilfield�� On the basis of the recognition of unconformable relationship��the reservoirs of the Arys oilfield in Lower Jurassic were the multiple stratigraphic unconformity reservoirs in type�� Present oil wells of the basement were independent reservoirs controlled by paleo-uplift��