Abstract: The thick sandy conglomerate reservoir is developed in Qie12 block of the Kunbei oilfield of Qaidam Basin. The key geological factors restricting reservoir development are the genetic type and distribution law of sandy conglomerate. By comprehensive utilization of geological information, wireline logging data, seismic information and production dynamic data, the genetic type, distribution law of sandy conglomerate and its controlling effect on hydrocarbon enrichment are systematically studied under the control of the isochronal stratigraphic framework. The results shows that alluvial fan facies is developed in the lower part of the Ganchaigou Group in Qie12 block. Five microfacies are identified including braided channel, debris flow, sheet flood, runoff channel and flood plain. Four sedimentary structure units are identified including “pano-connective sand-gravel body” sandwiched intermittent channel, stable channel forming overlapping compound channel, braided channel and lateral sheet flood, and runoff channel inlaid flood plain mudstone. Alluvial fan shows a sedimentary sequence of grain size upward-fining and retrograding sequence vertically and six alluvial fan bodies from north to south are developed on the plane. The sedimentary facies belt has obvious control effect on oil and gas distribution, the sedimentary structure units control the vertical enrichment of oil and gas, and the fan body evolution controls hydrocarbon plane aggregation.

Key words: sedimentary sequence, alluvial fan, sandy conglomerate reservoir, Qie12 block, Qaidam Basin