The Study Of The Character And Distribution Of Reservior In The Upper Paleozoic Group In Tabamiao Area Of Ordos Basin

The article starts with the core observation, make use of the data of core analysis and well-logging, applied various analysis methods to study the reservoir of the upper paleozoic group in Tabamiao area of Ordos basin. The study contents include: lithofacies, well-logging facies, sedimentary facies, the diagenesis of the sandstones, the character of reservoirs, the control factors of the reservoirs etc.12 kinds of lithofacies and 9 kinds of well-logging facies have been identified in the Paleozoic group in Tabamiao area by observe the core and contraste the well-logging data. According to the regional geology and the character of the lithofacies and well-logging facies, 4 kinds of sedimentary facies and 3 kinds of depositional system: marine system, delta system and fluvial system have been identified. The sedimentary facies of Taiyuan formation is marine faceis, up to Sanxi formation, the sedimentary facies is delta facies, the Xiashihezi formation Hel and He2 member are braided river facies, He3 member is meandering river facies.The mains types of sandstone of Taiyuan formation are lithic quartzarenite and quartzarenite; the mainly types of sandstone of Sanxi formation and Xiashihezi formation is litharenite.The dominant storage space is the solution micropores, the honeycomb-like solution pores and the kaolinitic intercrystalline pores. The pore throat is small to very small. The main characteristics of the reservoirs are low porosity and low permeability. The average porosity of sandstone is 6.2%, average permeability is 0.46 X 10-3u m2.The diagenesis of the sandstone is very complex, the types of diagenesis include: compaction and pressure solution, cemetation and replacement, hydration, alteration, solution, etc. The diagenesis controlled the characteristics of sandstone's storage space and reservoir quality, which can be proved from facts that quantity of original seldom preserved due to strong compaction and cementation; principal storage space of sandstone is micropores or super-micropores for weak solution and strong alteration, it have small pore radius and fine throat. This is the direct reason of bad reservoir property of sandstone, especially lower permeability.The influence and control factors of reservoirs include: deposition, diagenesisand tectogenesis. The deposition is the basic factor, it control the shape and distribution of sand body, and influence the type and the intensity of the diagenesis; the diagenesis is the key factor, it control the process of pore evolvement, so the diagenesis control the sandstone's storage space and reservoir quality directly; The fracture of the tectogenesis formation could improve the porosity and permeability of sandstone.At last, we classify the reservoirs and predict new benefit places.