Ordos Basin Jianshan Area Yanchang Group Leader Hu 7 Oil Reservoir Group Of The Research Of Sedimentary Facies

The Hujianshan area of Ordos basin rich oil and gas resources, the exploration degree of Chang7strata is relatively low, but it has great potential on oil and gas exploration. According to the core material, cast thin section, well logging and well drilling, this paper analyses the source rocks in work area, and research on sedimentary facies, sedimentary micro-facies and extension of sand bodies. Through the study, the author has a deep understanding of the sedimentary system of Chang7oil reservoir, especially the Chang71and Chang72small layers in Yanchang group of the Triassic in the Hujianshan area of Ordos basin, which prepare for the forecast of the favorable exploration targets.There are five mainly sections in the Chang7layer of Yanchang group of Ordos basin:northeastern district, southwestern district, northwestern district, western district and southern district. The mainly parts of the study area belong to the North East district; but nearby the Wuqi region which in the southwest corner of the study area are mainly belong to the mixed district. The lithic-arkose and feldspathic lithic sandstone are the major type of the Chang7formation in Hujianshan area; poorly rounded of the detrital sediment, middle-poor degree of sorting, fine size graded and low maturity of the sandstone structure.The Longdong area of Ordos basin is in the south of the study area, with good reservoir in Chang71and Chang73of Yanchang formation. It is found by research that the main reservoir is turbidite sandstone. Contrast the turbidite sandstone of Longdong area and the main sandstone in the study area, it shows that underwater distributary channel microfacies deposition is the mainly type of the Chang7formation in Hujianshan area, there is a clear difference with the turbidite sandstoneof Longdong area.The Hujianshan area develop lake and delta sedimentary, which lake sedimentary only develop in the Wuqi area, the southwest corner of the study area, the main types sediment subfacies of lake sedimentary are semi-deep lake and deep lake sediment subfacies. without turbidite deposition. Delta facies main develop one subfacies that is delta front subfacies and four micro-facies which are subaqueous distributary channel micro-facies; interdistributary estuary micro-facies; mouth bar micro-facies and distal bar micro-facies, but there is rarely develop mouth bar micro-facies and distal bar micro-facies in Hujianshan area.The Chang7strata deposited large connected sand body in the Hujianshan area, it is mainly develop in the deposition region of subaqueous distributary channel sandstone in the north central of study area, and Chang72sand body is more development than Chang71sand body. After the exploration found that the oil producing wells mainly distribute in the subaqueous distributary channel sand bodies, it is shows that the subaqueous distributary channel sand bodies is the major reservoir stratum in Hujianshan area. The sand bodies have fine grain size, middle sorting, which are the foundations of forming advantageous reservoirs.