Characteristics Of The Reservoir And The Influence Factors Of Physical Properities In Tongbomiao-Nantun Formation, Lower Cretaceous, Southern Part Of Wuerxun Depression

The south of Wuerxun Depression in Halaer Basin, while the focused layer, as an important area of reservoir location, resources potential, is the Lower Cretaceous, Tongbomiao - Nantun Formation. The study purpose in this paper is to discuss the reservoir and identify the clay minerals kaolinite in this area on the impact of reservoir properties from the perspective of the petrology, digenesis, and porosity evolution of the angle of depression in the southern region Wuerxun. The research result that has theoretical and practical significance, will provide both a theoretical basis for the research and a real support for the production in the future.The petrology study is a basis of the research on Diagenesis. Based on the rock thin identification and the observation of the scanned electron micrograph, as well as the collected data, the analysis shows that the rock type of the study area reservoir is sandstone, tuffaceous sandstone, sediment-tuff and tuff, especially sandstone which includes lithic sandstone, feldspathic lithic sandstone, lithic feldspathic sandstone and feldspathic sandstone.Based on the analysis of both the ordinary thin - section and the casting lamella and the observation of scanning electron microscope photos, as well as the collected information, we studied the diagenesis characteristics of sandstone in Tongbomiao- Nantun Formation. The types of diagenesis are mainly divided as compaction, cementation, replacement and erosion - dissolution. Cementation includes siliceous cementation, carbonate and authigenic clay mineral cementation. Diagenesis symbiosis series are compaction, clay coating, early siderite cementation, erosion - dissolution, secondary overgrowth - authigenic quartz, authigenic gaolinite and illite, calcite cementation and dolomite cementation. The diagenesis phase is in middle diagenetic A phase mostly, while in early diagenetic A and B phase sometimes, the depth for each phase is:early diagenetic A (Ro<0.35%):1419mearly diagenetic B (Ro=0.35⁰.5%):1600mmedium diagenetic A ( Ro=0.5¹.3%):3031mThe diagenetic facies can be devideed into three types as the early weak compaction - siderite filling - authigenic clay mineral coating diagenetic facie; strong compaction dissolution-kaolinite, quartz secondary overgrowth, authigenic quartz microlite diagenetic facie; dissolution - carbonate replacement and cementation.The pore types of Tongbomiao Formation and Nantun Formation include intergranular pore, filling inner pore, crack pore, solution pore by means of casting thin - section observation and SEM analysis. According to the Clastic reservoir pore structure level and the divided logo by Di Shi– xiang(1991), it is determined that the pore structure of the study area is mostly medium (â…¡), minor bad (â…¢) and good (â… ).The characteristics of sandstone reservior on the study area are medium - low porosity and low permeability. The porosity range is from 0.46% to 25.5% and on average of 11.78%; the permeability range is from 0.01 to 2204×10-3μm2 and on average of 21.47×10^-3μm².Compaction and cementation reduces the properties of the reservior while the dissolution increases and influences it.The compaction reduces the amount of the original pore that decreases gradually. The permeability is also decreased while the depth increases. The dissolution can form the secondary pores and improve the reservior properties.For the sedimentary facies, the reservior property of fan - delta front and braided channel - delta front are relatively better since it is in a Strong hydrodynamic condition of depositional environment to be conducive to the formation of kaolinite.Between the Porosity and permeability of kaolinite, the correlation is good. and has a positive correlation with the porosity while a negative correlation with permeability. The physical properties of the areas with high kaolinite content is relatively good.