Study On Numerical Simulation Of Non-condensable Gases Assisted SAGD Technology For Oil Sand Bitumen

The homogeneous M oil sand in western Canada is characterized by low pressure and its bitumen is characterized by high density,high viscosity,high hydrocarbon ratio,and high heavy metal content.Conventional steam assisted gravity drainage technology?SAGD?faces serious problems such as excessive heat loss to the overburden,low heat utilization,and high steam oil ratio.And researches show that the steam and gas push technology?SAGP?can effectively reduce heat loss and improve the steam oil ratio.However,the injection of non-condensing gas also affects the development of the steam chamber,which affects the ultimate recovery factor.Therefore,the purpose of this paper is to explore the mining mechanism and feasibility of SAGP technology with different non-condensate gas,and to provide a theoretical basis for the on-site oil sand bitumen SAGP technology development.Firstly,the interaction characteristics between three non-condensable gases?CH₄,N₂,CO₂?and bitumen is investigated by laboratory experiment.Secondly,simulates the phase behavior on the basis of the experiment results by Winprop.Then,based on the reservoir parameters of M oil sand,typical numerical models of non-condensable gases assisted SAGD are established.Thirdly,analyzes the effect of non-condensate gas on the expansion of the steam chamber.Finally,through the optimization of the gas injection parameters,the optimal SAGP development scheme is obtained for the M oil sand.The experiment results show that these non-condensable gases can reduce oil viscosity,enhance oil flow capacity,and expand oil volume in the formation,thus supplementing the formation energy.The results also show that CO₂ has the strongest swelling and viscosity reduction effect,and the CO₂-bitumen system has the lowest interfacial tension.The numerical simulation results show that during the steam chamber upward expansion stage,non-condensable gas distributes in the upper part of the steam chamber,which slows the rising speed of the steam chamber,at the same time,non-condensable gas forms a thin layer under the overburden which reduces the heat loss of steam.And,during the stage of steam chamber expands along the overburden,non-condensable gas distributes on the lateral boundary of the steam chamber,which leads to the even expansion of steam chamber.Also,the temperature and pressure of the steam chamber can be effectively maintained,which lead to the increase of oil production rate.The presence of non-condensable gas will delay the arrival of the final drainage stage and decrease the oil production rate of this stage.The research shows that for M oil sand,injecting CH₄ slug after the steam chamber reaches the top of the reservoir and maintain the gas-liquid ratio at 5²0%can get the optimal results.This scheme can effectively reduce the cumulative gasoline ratio and reduce the steam demand.