Material balance equations of heavy oil reservoir with bottom water exploited by injecting nitrogen foam

Bottom water coning exists in steam heating area during the multiperiodic steam huff and puff in heavy oil reservoir with bottom water.Nitrogen foam injected into bottom of water coning well can push bottom water to original water-oil contact.The process of water coning control by injecting nitrogen foam was simplified as gas driving oil,oil driving foam and foam driving water.Material balance equations were obtained to study the water coning control technology in heavy oil reservoir with bottom water.The calculation methods of augment oil volume of injected nitrogen foam and released nitrogen,thickness of enriched oil zone and depth of bottom water were proposed.These equations were applied to a production well of heavy oil reservoir with bottom water in Shengli Oilfield.The results show that the water coning can be pushed to the original water-oil contact at nitrogen injection rate of 600 m3/h after injecting nitrogen foam 19 days,and the optimum wellbore penetration into a pay zone is 14.26 m above the original water-oil contact.