| This paper investigated the structural attitude of Chang-61 reservoir of Yanchang Formation in this region on the basis of the research result of Ordos Basin geotectonics and regional geology research combined with the regional structural evolution characteristics. According to the drilling and well logging curves data interpretation results, determined the structural attitude of the top surface of Chang-61 reservoir as partially developed nose-like microscopic structure which has a certain effect on the control of reservoir gather. For the purpose of formation fine correlation,this paper determined the longitudinal guiding bed and guide seam on the basis of formation research result of Yanchang Formation in Triassic, Ordos Basin, and combined with Regional geological features. On the basis above, finished the formation fine correlation and division of drilled wells in the research area using sedimentary theory, on the principle of cyclic correlation and graduation control, and concluded that the Chang-61 can be further divided into Chang-611 and Chang-612, each for about 20m thick. It also determined the longitudinal sequence of sedimentary facies association through the core examination and electrofacies analysis ,using the lithological association characteristics,color, sedimentary structural and some other facis marks, combined with regional depositional setting,recognised that the Chang-611 and Chang-612 reservoir is delta plane deposit,where mainly developed distributary channel,crevasse,and interdistributary microfacies, the main charactersistics of sedimentary facies and sand bodies distribution presents a northeast-southwest zebraic trend, the distributary channel is separated by interdistributary deposits.In order to investigate the areal distribution of reservoir parameters, determine the geologic reserve parameters, and make fine log interpretation, a well log interpretation chart has been set up in accord with that region, taken original well log into consideration and combined with oil testing result. According to the fine chat interpretation of well log , the cutoff of porosity, permeability, oil saturation are respectively 8%, 0.3×10-3μm2 and 20%, average effective oil bearing thickness is 14.4m, all of these data provide a basis for geologic reserve calculation.This paper made fine investigation on the petrological characteristics, physical characteristics, heterogeneity characteristics, percolation features, microscopic pore structure characteristics etc. of Chang-61 reservoir on the basis of well logs and various kinds analytical data .The results shows the pores of Chang -61 are mainly primary granular porosity and feldspar vugular pore, the throats are mainly medium-fine-sized, fine and tiny, the pore throat structure are mainly big pore–tiny throat and medium pore–tiny throat, which are the major types of hydrocarbon pore volume in the research area. The porosity and permeability on the average of target stratum of Chang-61 are 9.94% and 1.2×10-3μm2 respectively. The district is a reservoir with low porosity and permeability on the whole. The reservoir layer shows strong inlayer heterogeneity, interlayer heterogeneity and areal heterogeneity.The relatively high porosity and high permeability reservoirs are mainly distributed in the main river development area. The formation sensitivity is evaluated on the basis of analysis of velocity sensitivity, water sensitivity, acid sensitivity of reservoir sandstone by drilling core test.This paper established an effective thickness standard for the stratigraphic division of Chang-61 reservoir, and divided the drilled well for effective thickness on the basis of core data, by the method of log interpretation, and tested by formation test and pilot production. According to reserves parameter determination standards for the petroleum industry and the characteristics of Chang-61 reservoir, determined required parameters for caculaiton, and made reserves evaluation. The reserve is 1088.42×104t. The reservoir has a low reserves abundance: 31.40×104t/km2.
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