Research On Sequence Characteristics Of Nantun Group In Southern Area Of Wuerxun Hollow

Based on the theories and methods of the sequence stratigraphy, sedimentology, structural geology, petroleum geology, as well as the analytical data of seismic, well logging, core, the author analyses and studies the sequence stratigraphic framework and precipitation facies of the NanTun formation in the southern area carefully and deeply. At the same time, combines with the research results of previous studies and the initial work above, the author carries on the forecast about the reservoir facies. The results have actual guiding significances on the future hydrocarbon exploration and development as well as the allocation of the well location in the area.On the basis of analysing and drawing on the experience of the results of previous studies carefully, we success on the unification of the drilling stratification and the seismic interface, and establish the sequence stratigraphic framework combining the well logging with seismic. At last, we divide the NanTun formation into two third-order sequences from bottom to top, as SQN1and SQN2. All system tracts are fully developed in each third-order sequence. The interface of the two third-order sequence is located at the conversion surface of the lithology and electrical. The interface presents the character of partly truncation below, and it presents the character of onlap above. Finally we divided SQN1 into four fouth-order sequences from bottom to top, as N1SQ1, N1SQ2, N1SQ3 and N1SQ4. We also divide SQN2 into three fouth-order sequences from bottom to top, as N2SQ1, N2SQ2 and N2SQ3. All system tracts are fully developed in each four-order sequence.Through ananlyse the controlling factors on the sequence such as structure subsidence, climatic change, sediment supply and lake level changes in the research area, we interprete the effects of various controlling factors on the sequence development. The finding suggested that structure subsidence was the main factor on controlling the layer sequence development of the faulted period.Combining with the data of crop, seismic, well drilling and logging, the characters of precipitation facies, depositional model and depositional systems distribution of the NanTun formation are defined. The main precipitation facies in the NanTun formation are Fan-delta, braided fluvial delta , lacustrine and Lake Floor fan .Finally, considering of the research above, we point out the favorable reservoir facies.