| Honglian-Yuanyichang area is located in Taibei Depression of Tuha Basin, with area of 400km2. The reservoir of main production layers is Kalaza and Sanshilidadun Formations. Based on sequence division this paper studied two aspects: (1) To get better understanding of sedimentary characteristics and reservoir distribution of Kalaza and Sanshilidadun Formations; (2) To find the reason why the wells drilled in Yuanyichang area lost. Focusing on the above problems, the paper follows a path from point (well) to line (cross section), to surface (map), to area (field), and adopts several advanced geologic theories and technologies, taking reservoir sedimentology, high-resolution sequence stratigraphy for instance. Following research fruits are achieved:1. Cores of wells has been carefully observed and described. Combining with logging study, it is considered that J3k-K1 contains alluvial fan and brided river delta, which can be divided into 6 sub-facies and 13 micro-facies.2. High-resolution sequence stratigraphy theory has been used to analyze stacking patterns of short-term cycle, zone J3k-K1 is divided into 2 long-term stratigraphic cycles: SQ1 and SQ2, and SQ2 is divided into 2 middle-term stratigraphic cycles.3. By way of the theories of sedimentology, 9 electrofacies models have been established. In connection with seismic attributes, contour map of sand thickness and sand/strata ratio described the sedimentary facies in stratigraphic frame.4. After deep understanding the information of Yuanyichang area, we considered that the reason why the well lost is that the thrust fault activated for long time and leads the oil spilled over.5. Sand distribution researched in Yunayichang area and two favorable positions for drilling forecasted according to seismic inversion, attribution analysis and tectonic features.
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