Sedmentary Facies Of The Oil-congtaining Interval Chang 8 Of Yanchang Formation In BaiBao On Ordos Basin

The Baibao area of Ordos basin, which possesses abundant oil and gas resources and should be paid more attention ,has bright prospect in oil and gas exploration.By collecting data about outcrop, core, and many other elementary geological data, at the same time using sedimentary analyse and geological analyse, in this thesis, sequence division were applied, provenance were analysised, type of sedimentary facies were identified, the extension of sand bodies, distributing of sedimentary facies and physical conditions of reservoir were studied and the paleogeograpby were reconstruced. Sedimentary system of the oil-bearing interval chang8 of Yanchang Formation in Baibao were realized by the research above. Finally the favorable area were found out.Based on the primary marks of contrast in region and interface of sequence stratigraphy, stratum of the oil-bearing interval chang8 of Yanchang Formation were divised.The Baibao area is far-flung and have more than one sediment source. From palaeo-structure pattern, distribution of sedimentary system, depositional structure and texture, composition characteristics of debris, cathodoluminescence of quartz, characteristics of heavy minerals, characteristics of rare earth element and trace element, sediment source of study area was discussed. It indicated there are three sections in the area , such as, debris material of northern area derived from Yinshan and Wulangeer ancient promontory which is granite, granite-genesis and hiotite schist; The west sediment come from ZguoziShan, Luoshan which is not only ancient granite ,gneiss, but also quartite of Sinian, metamorphic rock and carbonate rock. The southwest sediment source is come from Longxian-Baoji Oldland which is ancient granite, gneiss, quartite of Sinian, metamorphic rock and carbonate rock, metamorphic rock.Based on outcrop observation, core description, single well-log and sequence analysis, , combined with analytic result of plane configuration of sandstone , characteristics petrology and log displays of all substratum, chang8 of Yanchang formation are composed of Lake system and Delta system. Divided sedimentary parfacies identified into meandering delta front, braided delta front and shallow lake. Developed in four kinds of microfacies, which is sheet sand, distributary channel, distributary gap and bank sand. Distributary channel is a advantage belt for sand develop. The sand bodies have coarse grain size, good sorting ,lack of matrix, growth intergranular pore and large of sand bodies scale, all of them are adventage of reservoir development and valuable target for evaluation.Base on the connecting-well section and combined with the synthetic study of geological back ground of the study area, the paleogeographic evolution was reconstructed. Depositional model of Baibao area is blong to water platform delta in chang8. The distributary channel deposits is the main reservoir sand. Through analysis of source rocks, distribution characteristics of sedimentary facies,, reservoir property, seal function of cap rocks, trap types , the favorable exploration area can be found out in the main oil-bearing beds in Baibao...