Study On Sediment,Diagenesis And Oilness Quality Of The Mesozoic In South Of Ordos Basin

Ordos Basin, the second largest basin in China, possesses abundant potential reserves of petroleum and natural gas. With the exploration and development carried out in recent years, mesozoic group in south region has found oil field with a hundred million reserves. So it is vital to further comprehension of geology ,make good use of high-resolution data about thin section analysis and well logs, develop study on sedimental petrology and evaluation on fine reservoir technology by combining with the results of test and analysis, objectively and reasonably evaluate sand body and analyze reservoir, forecast and looking for local sections of enrichment and high yield, and develop prospecting for new fields. Based on the theory of petrology and the combination of thick and thin facies, through the observation of analysis of rock slices and other ways such as scan electronic microscope, electric probe and X-rays analysis,etc., the rock of this area is fallen into five types: conglomerate, mid-coarse sand stone, fine sand stone , silt sand stone, shale. By syntheticall using data of seism and well-logs and combining with basin construct and evolution history, despositional facies in this area are fallen into 4kinds :alluvial-fanfacies, deltafacies, lacustrine facies, braided stream facies. It is concluded from the physical property of reservoir of sand body in different depositonal environment that the most favorable reservoirs are sand bodies of watercourse and offset unwatercourse, secondly the estuary sand bar in delta facies, the most unfavorable lacustrine facies and far-forth sand bar. Clay minerals and its evolvement characteristics, which is much concerned with the process of organic matter maturation ,oil and gas forming ,creation of newly-born mineral,development degree of secondary porosity and reservoir,are one of the most important characteristics. Clay minerals and its evolvement characteristics are concluded.Types of porposity and its evolvement characteristics are researched,which have primary porosity and secondary porosity. Double development belts of secondary porosity are about 1300-1500m and 1700-1900m.Diagenesis types and stages of organic matter maturation are discussed. And development belts of secondary porosity must be namely favorable reservoirs In the light of rock constituents and structures and its characteristics of oil-storage,reservoirs in study area are five types,and oil-producing conditions and favorable sections are also forecast.