Application of material balance method to nitrogen anti-water-coning technology

Nitrogen anti-water-coning is simplified into two processes of gas driving oil and oil driving water based on the mechanisms of nitrogen repressing water coning and enhancing oil recovery. Material balance method is employed to study nitrogen anti-water-coning technology in heavy oil reservoirs with bottom water and multi-periodic steam huff and puff. The calculation methods of gas oil contact, water oil contact, the oil volume enabled by injected nitrogen, and the formation volume of enriched oil zone are established. The methods are applied to a production well of heavy oil reservoir with bottom water in the Shengli Oilfield, showing that injecting nitrogen for 20 days, 13 days and 10 days can push water coning to the original water oil contact at nitrogen injection rates of 600, 900, and 1 200 m3/h (standard conditions), respectively. The technology can effectively control water coning and increase oil production during effective periods.