Study On The Mechanism Of Nitrogen Recovery And Its Adaptability Evaluation

CO₂ huff and puff technology has been successfully used in several fault-block reservoirs in Jidong oilfield to obtain better oil-increasing effect,but it also faces a series of problems,such as pipeline corrosion,shortage of gas source,and poor application effect of multiple rounds.The N₂ has the advantages of stable chemical property,wide source and supplementary energy,based on the present CO₂ oil production technology,the feasibility of replacing?or partially substituting?CO₂ with N₂ oil production technology is investigated to solve?or mitigate?the above problems,and the adaptability of nitrogen production technology in Jidong oilfield is determined.Firstly,the high-pressure physical property of typical crude oil in Jidong oilfield was injected into a certain gas?N₂ or CO₂?.On this basis,the experimental model of indoor edge water simulation was used to design simulation experiment?pure N₂ huff and puff,surfactant+N₂ huff and puff,N₂+CO₂ stimulation and pure CO₂ huff and puff oil production technology?to evaluate N₂,CO₂ and other gas stimulation control the effect of edge water.On the other hand,a heterogeneous model was used to evaluate the effect and adaptability of N₂ foam flooding in the middle porosity and permeability reservoir,and to discuss the influence of permeability differential and timing on the N₂foam flooding effect.Finally,a typical numerical simulation is used to analyze the main control factors of N₂ foam flooding technology.The experimental results show that when the N₂ and CO₂ are mixed with the molar ratio of 1:1,the physical property of the mixture is between two kinds of pure gas,which can not only play the role of CO₂ dissolving and reducing viscosity,but also can exert the swelling effect of N₂ to displace crude oil.N₂+CO₂ huff and puff?water control lasting effect up to 0.2 PV,increase the amount of oil up to 4.4%?instead of pure CO₂?continuous effect 0.25 PV,increase oil volume 5.4%?Obviously better than N₂ Huff and surfactant+N₂ Huff and puff control edge water effect.In addition,for N₂foam drive,it can be used to improve the oil displacement effect?6 times difference and moisture content 80 pieces under the N₂ foam drive can increase the extraction degree34.2 on the basis of water flooding?in the middle porosity infiltration reservoir.The ultimate recovery rate is 54.9%,and the optimum permeability range is 3⁷,and the optimal timing is 80%;the results of typical numerical model analysis show that N₂foam flooding technology is suitable for use in the thickness of about ten m,medium-low permeability,low viscous crude oil and has a certain heterogeneity in the reservoir.The gas-liquid ratio of N₂ foam is controlled at about 2:1;the injection speed?or extraction speed?should be increased appropriately in the subsequent water flooding process to increase the oil extraction degree and both the physical and numerical models indicate that the best injection time of N₂ foam flooding is that the water content of the mining wells reaches 80%.The research results of this paper are of guiding significance to the optimization of N₂ oil production technology and project design in the field.