Study On Sedimentary Facies Of Mesozoic-Cenozoic Erathem In Qian Xi Of The North Qaidam Basin

Qian xi should be a favorable area of oil-gas enrichment because that was on the constitution top of Sai Shiteng depression. Forty exploratory and parametric wells were prospected in Qian Xi without large progress since boring zhong 1 well September 1960, the accumulating totals of which were to70566.3m.it was shown that the area was a special one which contained full of oil-gas but could not be obtained.so the basic condition of the oil-gas progress was to augment the Study on Sedimentary Facies.After abstracting the geological characteristic, the Sedimentary Facies mark of petrology,sedimentary structure and well logging was generalized systematically through aggregate analysising the information of well core,well recording and well logging in qianxi of the north qaidam basin;Then Sedimentary Facies was divided four types containing alluvial fan,braided river,braided river delta and lacustrine basic on the study of sixteen wells'Sedimentary Facies of single well.The alluvial fan could be divided to three subfacies and six microfacies, The braided river could be divided to two subfacies and three microfacies, The braided river delta could be divided to three subfacies and seven microfacies The lacustrine developed onshore lacustrine subfacies and two microfacies.Finally,through the fabrication and analyse of cross section and flat face drawing, the result was obtained that the alluvial fan- braided river delta-onshore lacustrine sedimentary association was developed in middle Jurassic epoch, the braided river-braided river delta-onshore lacustrine sedimentary association was deceloped in Paleocene-Eocene Epoch, the alluvial fan-braided river-braided river delta- onshore lacustrine sedimentary association was developed in Oligocene Epoch, the braided river-braided river delta-onshore lacustrine sedimentary association was developed in Miocene Epoch.