Injection Of Air With Reduced Oxygen For Improved Oil Recovery From Ultra-Low Permeability Oil Reservoirs

Air injection into low and ultra low permeability reservoirs are an effective technique for improved oil recovery.Compared to other gases,air injection has abundant air supply and economic advantages.Contra to the explosion and injection pipe string corrosion into air injection,this paper raised injection of air with reduced oxygen for improved oil recovery.This paper is based on EOR mechanism of ultra low permeability of reservoir and injection phlogisticated air,analyzing ultra low groutability and influence factors of gas permeability.Using the super low permeability resevoirs Changqing Oilfield as an example,establishing the geological model and the injection process phlogisticated air reservoir numerical simulation model,low temperature oxidation kinetics mechanical model and fluid phase permeability model.The effects of different injection methods,well pattern and injection production parameters on the ultra low permeability reservoir were studied.The simulation results show that using the staggered horizontal well injection production system?both the injection well and horizontal well are horizontal wells?and the complex well system of horizontal-straight wells has the best flooding effect.Horizontal well gas injection not only can effectively supplement the formation energy,increase the oil drainage area,but also the formation of lateral linear displacement in the formation,increase the sweep volume,improve oil recovery.The design of complex well pattern with the combination of hor izontal well and horizontal well,changing the"line to line"displacement in the variable reservoir to“face to line”displacement,which can reduce the gas injection pressure and increase the swept volume.Oxygen reduction can be used when the local permeability is very low to solve the problem of injection and add formation pressure.Horizontal well injection is suitable for the development of ultra-low permeability reservoirs.It has the characteristics of high recovery rate,low injection pressure and good comprehensive mining effect.The results show that the length of the horizontal well is 800⁹00m,the distance between the two wells is 1000m,the row distance is 250³00m.When the penetration ratio of injection and production wells is 0.375,the mining effect is the best.To evaluate the sensitive factors influencing the recovery effect of ultra low permeability reservoir,analyzes the horizontal wells and wells,horizontal wells fracture azimuth horizon,phlogisticated air oxygen content and gas injection rate and other parameters affect the recovery rate,and optimize the parameters.Studies have shown that horizontal wells have the best effect when parallel to natural fractures.The reduced oxygen air flooding in ultra-low permeability reservoir,not only has the advantages of nitrogen flooding,air O₂ low temperature oxidation can also occur in the underground,improve the recovery,while reducing the low O₂ content of oxygen in the air,can effectively prevent the risk of explosion in production wels.