The Influence of the Karatau Fault on Hydrocarbon Migration in the Aryskum Depression, Kazakhstan

In this paper, the history of Karatau strike-slip fault and its control on inversion structures and hydrocarbon migration of the Aryskum depression were discussed. Karatau fault was characterized by sinistral strike-slip in the early stage and dextral strike-slip in the late stage. Lots of positive inversion structures in the Aryskum depression formed by the dextral strike-slip movement during Eocene-Oligocene, which synchronized with the main generation and expulsion stages of major source rocks, becoming favorable traps for hydrocarbon accumulation. Karatau fault also dominated the direction of hydrocarbon expulsion andmigration in the J(1) and J(2) source rocks by altering their layer shapes, resulting in higher hydrocarbon enrichment in the depression center than that in the flanks. Meanwhile, as the thickness of regional cap rock in the middle and northern parts of the Aryskum depression is obviously higher than that in the relevant vertical fault throws which has caused little hydrocarbon dissipation from the fault, the hydrocarbon enrichment in the middle and northern parts of the depression is higher than that in the southern part.