SEDIMENTARY CHARACTERISTICS OF CHANG 9 OF YANGCHANG FORMATION IN PENGYANG-JINGCHUAN AREA, ORDOS BASIN

Chang 9 Oil-bearing in the southwest of Ordos Basin shows a favorable exploration potential. However, few studies have been done on the Chang 9 member in the Pengyang-Jingchuan area in the southwest margin of the basin, especially there is a lack of research on sedimentary environment, The paper studies sedimentary characteristics of Chang 9 member in the Pengyang-Jingchuan Area by means of field outcrop, core logging, grading analysis, thin section authentication and so on. The results show: Chang 9 Member in the study area is influenced by the provenance in the southwest and the south and the types of rocks are mainly feldspathic quartz sandstone and lithic quartz sandstone and the lithology is mainly grey-green and grey-white fine sandstone, siltstone, grey-black silty mudstone and black mud stone. In Phase Chang 9, distinctive river delta plain subfacies, delta front subfacies and shallow lake subfacies are mainly developing in the study area. The lake shoreline moves southwestwards from Phase Chang 92 to Phase Chang 91, the area of the shallow lake is continuously expanding and this period is aperiod of lake basin expansion. There may be potential source rocks among black mudstones in the study area.