The Yaha oil and gas field in the Tarim Basin is the largest oil and gas condensate discovered in the mainland of China up to now, which consists of 12 petroleum pools. The distribution of oil and gas is characterized by "oil enriched in the west, gas enriched in the east" , "oil enriched in the upper, gas enriched in the lower" and " lighter in the upper, heavier in the lower". The character was cause by gravitational differentiation, when oil and gas injected from the northwest during two peaks of petroleum injection. It formed a "positive differential entrapment injected from the middle" model, which is different from those of Gussow and Schowalter.