Abstract: The Kezilesu group of Lower Cretaceous is the most important oil -bearing series in southwestern Tarim basin. Study of reservoir characteristics shows that the major rock type is lithic fine sandstone developed in braided river channel. The reservoir space is dominated by intergranular and intragranular solution pores. The reservoir petrophysical property is controlled by the sedimentary environment, the diagenesis and the type and content of clay mineral. Kezilesu group is deposited above the paleo-landform formed by Paleozoic weathering and erosion. It is recognized that Wuqia, Wuboer and Fusha structural belts are of large thickness of Lower Cretaceous strata, lie on the favorable sedimentary facies, and should be the favorable and target zones for further petroleum exploration in this area.

Key words: Tarim basin, southwestern Tarim depression, Cretaceous, Kezilesu group, reservoir characteristic