Research On Sedimentary System, Sequence Stratigraphy, Reservoir Evaluation For Chang 8-6 Oil Beds Of Yanchang Formation In Zhenyuan-Jingchuan Field, Ordos Basin

According to the comprehensive detailed analysis of drilling, well core, logging and seismic data, we believed that Zhenyuan-Jingchuan field developed delta-lacustrine sedimentary system in Chang 8-6 Member of Yanchang Formation. Huge basin and shallow water, long river and slow gradient was first put in southwest Ordos basin by use of comparing sedimentology. It was a shallow delta, and the framework sandstone of delta front was subaqueous distributary channel, but mouth bar was sparse.Yanchang Formation of this field can be divided into one super long term base level cycle and three long term base level cycle through detailed study of high resolution sequence stratigrahy. Chang8-7 belongs to the second long term base level cycle and Chang6 belongs to lower of the third long term base level cycle. We first mapped sedimentary microfacies in the framework of middle term base level cycle based on establishing isochronous stratigraphic framework of Chang 8-6 and analyzed the dominated factors of sequence stratigraphy.Analyzed diagenesis intensity by the transformation of clay mineral, vitrinite reflectance, authigenic mineral characters, result implied that diagenesis intensity of Chang 8 was higher than Chang 6 and Zhenyuan was higher than Jinchuang. The diagenesis intensity of Chang 6 belongs to A period of later diagenesis in Jinchuang field, and B period of later diagenesis in Zhenyuan field, but Chang 8 belongs to B-C period of later diagenesis in Zhenyuan field relatively. It is showed that oil and water relative permeability which calculated by well log can depict precisely production of reservoir. We concluded the expression of the width of subaqueous distributary channel and the thickness of channel sandstone of high and low accommodation by analyzing the relationship between the width of subaqueous distributary channel and the thickness of channel sandstone of different accommodation. We concluded...