Research on reservoir productivity difference of Yan'an formation of Jingbian oilfield in Ordos basin

The oil reservoirs of Yan'an formation of Jingbian oilfield in Ordos basin widely distributed with large difference in productivity.During 2007-2008,the resistivity and thickness of oil layers in Dunwa area were relatively small and the production rate per well was higher which the wells with daily initial production rate of more than 15t had reached to 12 and had slow declining rate at the early stage of production.This was caused by the relatively deep burial depth,relatively light crude oil,high formation water salinity,obvious oil and water separation of reservoirs,clear and active bottom water of reservoirs,relatively high formation energy or later stage of good energy preservation of Yan-9 in Yan'an formation of this area.The resistivity and thickness of oil layers in Xinzhuangwan area were relatively large and the production rate per well was relatively lower which the wells were only up to 7 with daily initial production rate of only 5t and fast declining rate at the early stage of production.This was related to the relatively shallow burial depth,heavy crude oil,higher oxidation degree of oil,higher irreducible water saturation,low formation water salinity,poor oil and water separation of reservoirs,distinctive reservoir bottom water,relatively low formation energy or later stage of poor energy preservation of Yan-9 in Yan'an formation of this area.