Research and application of nitrogen foam coning control technique for heavy oil reservoir with bottom water in offshore oilfield

The sensitivity elements of nitrogen foam coning-control fluid are analyzed,and the nitrogen foam coning-control fluid is developed to meet the demand for controlling bottom water coning the heavy oil reservoir in Qinhuangdao 32-6 oilfield in Bohai Bay.The simulation analysis indicates that effect of exclusion of water is best when the nitrogen is injected for 20 days,mass concentration of surface acting agent is 10 g/L,gas fluid ratio is 2∶1,soak time is 2 to 5 days.Laboratory evaluation shows that the foaming agent YS-FA150 has better compatibility with produced water,formation water and aquifer water,with foam half-life of 3 871 s,drain half-life of 215 s;the foam system with gas-liquid ratio of 2∶1 has the resistance factor up to 90;the saturated foaming agent can make core permeability recovered 99.8%.The field application shows that the new Nitrogen foam coning-control fluid can restrain the bottom water coning along the high-permeability zone effectively and gave good performance in a tested well,with the water cut reduced from 92.8% to 62.5%,the fluid production decreased by 40 m3 per day,the oil output increased by 22 m3 per day,and the cumulative oil increment of 3 500 m3,presenting the obvious overall benefit.The technology can enhance the oil production further after bottom water coning reservoir and has good application prospects.