Research Of Sedimentary And Sequence Feature In Interval 6 Of Yanchang Formation, Jiyuan Area Of Ordos Basin

Jiyuan area is located in the southwest of Ordos Basin. Interval 6 of Yanchang Formation of the Upper Triassic is one of the main production floor. Existing drilling data shows the thickness of sand body alternation are great, physical property are poorer and heterogeneity are serious, the oil-water relationship are complex. So, we should research delicate and systematic the provenance,sedimentary facie; Analyse the characteristic of high-resolution sequence stratigraphy. On this basis, we can analyse the sequence and lithofacies paleographic, dissect the characteristics of the reservoir development in the sequence-layer framework. And forecast the area which are favour of reservoir development. The research has acquired following results:1.Based on the core observation, analysis of logging and debris and minerals data, and combined with the fruit of predecessors this paper points out that the Interval 6 of Yanchang Formation in Jiyuan area in Ordos Basin developed meandering-delta and meare deposition system.2.Through analyse the heavy mineral of sandstone,detrital component of sandstone,rare-earth element and combine type sedimentary structure of rock core Etc, we analyse the provenance of Interval 6 of Yanchang Formation in Jiyuan area, the depositional stage in the study area was controlled by the northeast, northwest and southwest sources, in those ,the northeast and northwest are the main provenance orientation, while the southwest is the subordinate orientation.3. Apply the theories and methods of high-resolution sequence stratigraphy, the author studied the high-resolution sequence of the Interval 6 of Yanchang Formation. Which are divided into 1 long cyclic sequences,3 middle-term cyclic sequences and 10 short-term cyclic sequences. Distribution, structure and stacking pattern correlation of sequence of Interval 6 of Yanchang Formation in Jiyuan area have been described and compared. The Interval 6 of Yanchang Formation pertain to meandering-delta deposition system. The sequence of A model developed less, the sequence of C model developed most, at the same time, the sequence of B model developed a little. These characteristics reflex the sedimentary environment have a deep water body and the A/S≥1 is poor offset till lacking offset.4. Base on the analysis of high-resolution sequence and isochronal tracing of layer, adopt the technique of sequence-paleogeographic mapping, mainly choose the half cycle which amount sublayer sand body as isochronal layer unit, the author drawn up isopach map of layer,isopach map of sand body,distributing graph of sedimentary microfacies,well tie sect collation map of sequence framework of Interval 6 of Yanchang Formation in Jiyuan area. Base on these analysis, the author sum up the genetic type,geometric shape,plane spreading and evolution feature of sand body, and their action in the forecasting of reservoir.