| The Zhen 287 area of Zhen Yuan oilfield is located in the southwest of Yishan slope of Ordos Basin,is one of the major oil and gas producing area. The main subjects of this study is Chang 81 reservoir of Zhen 287 area of Zhen Yuan oilfield, predecessors studies as a guider, combining observation of core、well logging and analysis test of the data, to description the study area of reservoir from both of macro and microscope. Based on the above study, the reservoir is classified and evaluated comprehensivly.West-dipping monoclinic structure is the study area’s features, angle of gradient is small, less than 1°, The nose uplift towards northeast to southwest development, part of the nose uplift trending near East to west, the structure of each layer has a strong inheritance; this study divided Chang 81 layer of Zhen 287 area of Zhen Yuan oilfield into three small layer: Chang 811, Chang 812 and Chang 813 the thickness of each layer has a little change.Study area growing braided river of delta front, mainly developed micro-phase of underwater distributary channel and shunt Bay, in some areas estuary dam developed. Five channel developed in Chang 813 layer, the river is narrow; seven channel developed in Chang 812 layer, the river is growing much longer and wider than Chang 813; the river of Chang 811 is shrinking, developmental six narrow channel.The range of the porosity of the reservoir from 4.74% to 11.68%, the average of the porosity is 9.87%; the permeability value of the reservoir is ranged from 0.02×10-3μm to 1.2×10-3μm2, with an average of 0.847×10-3μm2. According to the porosity and permeability grading standards of Ordos Basin, the study area is belongs to a low and especially low porosity and permeability.Study area with gray brown, gray and black fine-grained feldspathic lithic sandstone, the shape of the detrital mostly second round to subangular round, the sort is moderate, the type of cement is main of film to pore; the type of the contact between the particles mostly point to line; cements are mainly clay minerals, carbonate and siliceous material and other components.Intergranular and feldspar dissolved pore are the main types of the area, there is a little moldic pore and micro-cracks in study area, intergranular pore accounted for 1.4%, feldspar solution accounted for 0.8%, other pore types accounted for 0.12%, according to the pore and throat classification criteria of ChangQing Oilfield, the type of the pore and throat is middle and small pore and micro throat.The study area of the reservoir is weakly lipophilic, velocity sensitivity is middle, water sensitivity and alkali sensitivity is middle to weak,acid sensitivity and salt sensitivity is weak, so we should pay attention to the flow rate control in the process of the development, reduce the impact of the permeability of the change of the flow velocity, pay more attention to the injecting material’s salinity and PH, to reduce formation damage implants and increase of the oil efficiency.Comprehensive analysis of reservoir characteristics and test data, the study area is divided into three type:Ⅰ,Ⅱ and Ⅲ,Ⅰ and Ⅱ type of reservoir mainly in sand thickness and good communication part of the river, the Ⅲ type of the reservoir is near the Bay area, sand is thin, generally distributed banded. Chang 812 is mainly of Ⅰ and Ⅱ type, the Ⅲ type is less, Chang 812 is the main layers; the Ⅱ type is main in Chang 813 and 811, the type of the Ⅲis scattered. Integrated classification and evaluation is important to guiding the reservoir’s rational and effective development. |
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