Study On Numerical Simulation Of Alternating Microbial Flooding And Air Injection

Microbial Flooding works relying on microbial metabolism,which is fit for low-temperature,high-water cut field,especially exhausted reservoir,it has limitations like low metabolism efficiency and limited swept volume.Air Injection is a new EOR method with advantages like low cost price and easy injection,but it still has security problem about oxygen breakthrough.Microbe and air synergetic flooding means alterly injecting microbe and air,injected oxygen offer a favorable environment for microbe,and air push an air resistance in high penetration layer,which helps enlarge microbial swept volume,thus enhance the Microbial Flooding effect;on the other hand,microbe consumpts oxygen which makes Air Injection safer.Microbe and air synergetic flooding can take the advantage of both Microbial Flooding and Air Injection,is a new potential EOR method.Based on the mechanism study on Microbial Flooding and Air Injection,and by means of laboratory experiments,this paper studied microbial effect on oil viscosity decline,oxygen’s influence on microbial de-oiled efficiency and microbial growth concentration,and further studied microbial oxygen consumption regularity and tested oxygen consumption rate;later finish the experiment of MEOR and get the relative permeability curve by numerical simulation relying on experiment data.By using microbial flooding’s relative permeability curve and compositional model in CMG,this paper studied the single factors which affect the efficiency of EOR;finally orthogonal ways helped find out the optimizing scheme and work out the prediction EOR effect.The results show that oil viscosity could decrease mostly at a rate of 15.25%~25.80%after microbial behavior;in microbe and air synergetic flooding,air offers oxygen which helps improve the efficiency of microbial flooding,the remaining nitrogen gas helps improve the pressure of reservoir and adjust the lateral section;facultative bacteria’s maximum growth concentration with oxygen triple that without oxygen and de-oiled efficiency improves3%~12%;with the air injection rate of 3000m~3/d~5000m~3/d and in consideration of the microbial oxygen consumption,the minimum radius of secure concentration is 145m~180m;the oxygen concentration is 50g/m~3~1972g/m~3 in the place of 200m;higher water injection rate results in lower oxygen concentration;with the air injection rate of 4000m3/d and water injection rate of 30m~3/d~70m~3/d,the minimum radius of secure concentration is all the same about 165m;in the core displacement experiments,microbial flooding shows good EOR effect by comparing water flooding and more microbe injection amount results in better effect;get the relative permeability curve by numerical adaptation to microbial experiment data;in microbe and air flooding,the single factor showing from the strongest to the weakest sensitivity is microbial concentration、injecting pore volume and air injection amount;the optimizing scheme obtained by numerical simulation and orthogonal ways is total injection of0.075PV(3.6 years)microbe,with one month’s injection of microbe in 3%concentration and one month’s air injection(1:8 liquid gas rate)in each cycle(2 months),and in this way the prediction results show that the minimum water ratio drop is 7.26%,the cumulative enhanced oil production is 3.13×104t,and EOR rate is 7.72%.