Research On Enhance Heavy Oil Recovery By Cyclic Steam And Gas Co-stimulation

In Bohai oil field, a new production method has been submitted which depends on the formation of steam and flue gas through burning combustion raw material. Before put forwarding this method, cold production or pumping is being adopted, causing low production rate. To study the heavy oil production mechanism by Cyclic Steam and Gas Co-stimulation and optimize the injection parameters, the physical simulation experiment and numerical simulation has been developed.The results of rheological experiment and PVT experiment by heavy oil saturated CH4,N2,CO2under different temperature and pressure show that the effect of heavy oil viscosity saturated gas at lower temperature is more evident that the higher temperature. The heavy oil viscosity,bubble point pressure,density,volume factor can be effected by CO2significantly. The effect is unconspicuous by N2.Using the high pressure independently developed sandpack model to carry out the throughput simulation experimental, the results show that the higher production is increased by steam+CO2stimulation on the horizontal well,and that is lower by steam+CO2+N2and steam+N2,and the average productivity index of heavy oil reservoir with high pressure composite increased more than3times.The results of numerical simulation show that the temperature of injected steam and gas co-stimulation is200℃when reservoir pressure is3MPa,and it is300℃when reservoir pressure is lOMPa; and the optimized volume ratio of gas and steam is0.25-0.5for3MPa,and it is0.5for lOMPa; and the optimized injected steam volume is10m3/m for about20days, and the optimized injected gas volume is1500m3/m for about20daysThe mechanism of steam and gas co-stimulation has been also discussed. Firstly, the injected CO2+N2and steam can reduce oil viscosity.Secondly; they can increase producing energy and expand the heating area. Simultaneously, they can assist gravity displacement.Laboratory experiment and numerical simulation show that steam and gas co-stimulation is a highly effective stimulation treatment and the improvement of heavy oil reservoir steam stimulation effect.