Abstract: Because of water/oil mobility ratio，injection/production difference，long term erosion and denudation，dominant
flow field will gradually develop in reservoirs in the long process of waterflooding. It has been proved that distribution and
migration of liquid and formation of remaining oil are all greatly influenced by dominant flow field. It has also been proved that
the dominant flow fields are quite different if formed in different blocks，different style reservoirs，different well patterns and
different working systems. According to the main feature of dominant flow field big streamline field intensity，streamline field
index（SFI）is induced to divide dominent flow field. The formation and stage of dominant flow field are divided by streamline
field index and PV index，degree of reserve recovery and injection efficiency. The dominant flow field is at early stage when
streamline field index is more than 1.5，and injection efficiency is high，and degree of reserve recovery is low. The dominant
flow field is at middle stage when streamline field index is more than 1.5，and injection efficiency is low，and degree of reserve
recovery is low. The dominant flow field is at later stage when streamline field index is more than 1.5，and injection efficiency
is high，and degree of reserve recovery is high.

Key words: dominant pathways, characterization, modified stream line, flow field, remaining oil