Main controlling factors for remaining oils in horizontal wells in sandstone reservoirs with bottom water in the Tahe Oil Field

In blocks no.1 and 9 in the Tahe Oil Field, complicated oil/water relationship and various controlling factors have made it difficult to tap remaining oils in sandstone reservoirs with bottom water during high water cut period. Water flooding pattern and remaining oil occurrence were analyzed in view of different controlling factors. Horizontal tracks and interlayers have four different configurations:totally blocking, horizontal to interlayers, crossing interlayers, and half blocking. The permeability of horizontal layers can be divided to four styles:two stage type, serration type, step type, and homogeneous type. Combining with production performance, we studied water flooding mode in horizontal section corresponding to different configurations and permeability styles, and discussed its control on remaining oil. Some methods for tapping remaining oil in reservoirs with bottom water were proposed.