Abstract: Yan 2 Block in Benbutu oilfield is a hydrocarbon rich block with faults and anticlines. The distribution of oil layers is determined mainly by faults, structures, sources and edge water energy. After the issue of velocity pitfall in this area was solved in 2001, the seismic data were reprocessed through 3D pre-stack depth migration, structural shapes were materialized, oil - bearing area increased from 3.0km 2 to 5. 6km 2, and proved reserves enlarged from 2.13 million tons to 3. 37 million tons.