| Changjiaweizi region which is about 1663 km2, locates on the middle of Qijia-Gulong Depression which is the second structure unit of Songliao basin. In this paper, Putaohua oil reservoir is the target layer,and it has a good regional cap rock, a good oil source rock of Qingshankou formation. So it is enrich of oil and gas,and must have a well foreground of exploration.It is forcasted that there will be over a hundred million ton petroleum in the first member of Yaojia formation of Putaohua oil reservoir.It is imprecise to identify the layer using seism,because of the interbed of thin sandstone and thin mudstone.And that makes imprecise cognition to the lithology and sedimentary face of reservoir.The study of properties and control factors hasn't done yet,so it has an effect to the forther exploration and exploitation.In view of the above problems,guided by reservoir sedimentation and reservoir geology,the studies of description of the characteristics and influence factors of reservoir are done to the Putaohua oil reservoir in Changjiaweizi with the help of comprehensive applying latest microscopic testing techniques for this kind of reservoir,also integrated with macroscopic reservoir study. The purpose of the above studies is to dissenction the characteristics of lithology, types of reservoir space, pore structure, porosity and permeability, to classify and evaluate the reservoirs.The influence factors to the gathering capability are analysed based on the studies of reservoir deposition and diagenesis. This is favourable to select available target., reasonable to classify exploration layer'series, to select inject and production system, and to improve the effect of oilfield exploration and development.On the basis of studying regional geologic setting and petroleum geologic background, by means of core observation, thin-section analysis, granularity analysis and so on, analyze the deposition; and describe the characteristic of sand in reservoir of Putaohua oil reservoir. That is a basic to evaluated reservoir and analyzes influence factors. Three sedimentary facies of delta, lacustrine and lacustrine fan are recognized and including seven sedimentary subfacies and thirteen sedimentary microfacies. The main reservoir sand types are distributary channel under water sedimentary sand, estuary dam sedimentary sand, sheet sand sedimentary sand,braided channel sedimentary sand and turbidite sedimentary sand. Using thin-section analysis, combined the methods of scanning electron microscope, microsopic analysis by cathode luminescence and so on, to identify pore styles the types of diageneisi, which include compaction, agglutination, metasomatism, dissolution. Compaction makes the protogenesis intergranule pore shrink rapidly; cementation in metasomatism fill and destroy pore; dissolution dissolve the grain or cementation to form expansile erosion intergranular and intraganular pore. This is the evolvement of reservoir.The characteristics of Putaohua oil reservoir are described under the methods below, common thin-section identify, casting thin-section observation, scanning electron microscope, microscopic analysis by cathode luminescence and so on. The studied area's sandstone is mainly composed with arkose clastic and clastic arkose sandstone,in which the content of quartz is low and arkose clastic is high. The interstitial filling materials are mainly clay minerals and carbonas cements. The maturation of mineral composition and rock structure is lower. There are eight pore types which are common intergranule pore, narrowing intergranule pore, erosion enlarge intergranule pore,erosion pore in the interstitial filling materials, erosion intragranular pore, casting erosion pore, fracture pore, and pore among clay minerial. Thereinto, erosion enlarge intergranule pore which takes 70 percent and erosion intragranular pore which takes 20 percent give a priority to the pore. The types of throat are mainly shrinking part of variable fracture and flaky or bend flaky throat, and sometimes tubal throat can be seen. The average of throat diametral is 0.218-3.577μm, and throat can be divided into the following two types under the standard, thin throat and imperceptible throat. It is mainly made up of imperceptible throat. Synthesizing mercury intrusion parameter,and characteristics of porosity, permeability and sedimentary facies, we can divide pore structure in this the region into the following three types,ⅡA,ⅡB,ⅢA.ⅢA is the main part. TypeⅡA has the characteristics of middle or high porosity and middle or low permeability and thin throat; typeⅡB has middle porosity and low permeability and imperceptible throat; typeⅢA has low porosity and low permeability andimperceptible throat. The results which are from mass core analysis and testing indicate that, porosity which distributes between 10%-15% in this region is respectively 41.32%; and 15%-20% distribution takes 34.16%. Permeability of core which distributes 0.01-1×10-3μm2 takes 61.71%, and 1-100×10-3μm2 takes 33.06%. According to the evaluated standard of Daqing oilfield, reservoirs in this area are totally middle porosity and low permeability.Following the method of weighting, we select eight parameters which can image reservoir's microscopic and macroscopic reservoir capability such as porosity, permeability, sedimentary microfacies, pore structure and so on. Using the method and the above parameters to divide seven small layers of Putaohua oil reservoir into three types named good, medium and bad. No.2,3,7 small layers are good reservoirs; No.4,6 are medium one; No.1,5 are bad one. Good reservoirs are mainly distributing in well Gu 463-2 and Long 31-2.On the basis of above studies, we discuss the main factors which influent reservoir properties. Two important factors which are sedimentation and diagenesis give the control to the reservoir. In part of sedimentation, they are material composition, granularity size, matrix content of sandstone to control the reservoir properties, and building a corresponding relationship between material composition, granularity size, matrix content and parameters of reservoir properties, to analyze the characteristics of avail reservoir. That is such a reservoir which is high in arkose and clastic, wide in granularity, low in matrix content, distributaries channel under water sandstone and braided channel sedimentary sandstone. Secondary diagenesis is the main factor to reservoir which includes compaction, agglutination, meta-somatism, dissolution.is a main control action except sedimentation. Dissolution is good for reservoir properties. And erosion enlarge intergranule pore, erosion intragranular pore and casting erosion pore which are formed from dissolution are main reservoir spaces in this region. Otherwise, compaction and agglutination destroy the reservoir. Compaction can make original intragranular pore smaller, and cement form agglutination fill the pore and throat which is more serious. So, avail reservoir is short of compactation and agglutination and well develop in dissolution.By means of large number of real and basic geological documents and core analysis and testing data, the microscopic and macroscopic characteristics of the reservoirs have been researched in detail, thus it has provided basic geological evidence for petroleum potential prediction in each target region and preference the most advantageous exploration and development target. The above studied results possess much more important guided significance and practical value for forther exploration and exploitation.
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