The Study Of Sedimentary Facies Of Dongying Formation In W20 Oil-field, Jizhong Depression

W20 Oilfield is located in the middle of Shigezhuang structural belt. Wen’an slope, Jizhong Depression. It is the major oil producing blocks of Dongying Formation. In recent years,W20 well area,W11 well area and W102 well area have gained industrial oil flow,which showing Dongying Formation of the W20 Oilfield having a good exploration and development potential,and W20 Oilfield is the important blocks of building capacity of Dongying Formation in Wen’an slope. But in recent years,the production wells have multiple oil-water systems, sand body connectivity is uncertain and sedimentary microfacies is not clear, those problems severely restrict the rolling development of the latter part of the Oilfield.According to the theory of sequence stratigraphy and high resolution sequence stratigraphy, combining with the study of core observation and description in target layer, logging data,well logging data and geophysical data,sedimentary microfacies characteristics of Dongying Formation in W20 Oilfield have studied. Based on the analysis of oil-water relationship of the producing wells, the reservoir types are clarified,which providing evidence for finding the favorable oil and gas accumulation in the study area. Based on the above research, three conclusions are drawed as following :1. According to the theory of sequence stratigraphy and high resolution sequence stratigraphy, combining with the study of logging data,well logging data, core data and three-dimensional seismic data covering the study area, Dongying Formation was divded into a medium-term cycles, two short term cycles and four ultra-short term cycles.2. Based on the core observation and description of Dongying Formation in the study area and the surrounding area,by the means of geophysical logging, the logging template applying to the target layer of the study area is summarized. We analyzed single well sedimentary microfacies on this basis and identified side beaches, natural levees, floodplain and river swamps.3. With the relationship between oil and water, the characteristics of sand body distribution of the production wells in the study area, in the target layer of Dongying Formation,the main reservoirs are structural-lithologic reservoirs and lithologic reservoirs. The structural-lithologic reservoirs are mainly affected by the faults, the lateral sealing of faults affects the oil- gas migration. The lithologic reservoirs are mainly affected by sand distribution and palaeogeomorphology. According to the trap types and reservoir types in study area, in this paper, favorable oil and gas accumulation is found, which provides technical support for the next evaluation and building capacity.