Abstract: Integrated research results show tha t the Tertiary lithologic oil reservoir in south a rea, western QaidamBasin,has favorable reservoir-forming conditions, exhibiting the distribution of lithologic oil reservoirs is controlled by the present structure framework and paleo-structure developed area; The distribution of three depositiona l systems, including Ala 'er fluvia l-delta -la keshore;Alerjin flooding fan-fan delta-half-deep lacstrine facies;Kunlunshan mountains flooding fa n-fluvial-sha llow la keshore depositional system, and the fa vorable sa ndbodies formed in fluvial,delta and fan delta regressiv e system tracts controlled the enrichment of lithologic oil reservoirs; The oil-enrichment sa gs and the direction of oil-ga s migration a nd accumula tion controlled the forma tion of the lithologic oil reservoirs. After the exploration practice in recent years,it is proposed that a set of exploration method suited to the geologic features of lithologic oil reservoir in this area￡?including the analysis on sedimentary ba ckground, stratigraphic sequence division and correlation,sequence bounda ry tracing, comprehensiv e analysis of sedimenta ry facies, target ev alua tion and analysis on the regula rity of reservoirforming. Explora tion results show that the sanbodies, formed in the fan-delta depositional system in foreland Alerjin, Hongliuquan-Yuejin lake depositional system a nd fluvial delta depositiona l system inYuejin area, has the adva ntages to form the lithologic oil reservoirs and will become the promising target for next exploration in this area.

Key words: Qaidam Ba sin, Tertiary, lithologic oil reservoir, exploration practice