Simulation Study On Migration And Gas Channeling Of CO₂ Flooding Front

With the deepening of exploration work in my country’s oil and gas fields,the proportion of difficult-to-use low-permeability reservoirs is increasing.Because the characteristics of CO₂have great advantages in the exploitation of this type of oil reservoir,using CO₂ as an oil displacement agent can not only increase the recoverable reserves of crude oil,but also realize long-term geological storage of CO₂.However,the problem of gas channeling in CO₂ flooding is more serious.Therefore,carrying out simulation studies on the migration and gas channeling laws of carbon dioxide flooding and proposing targeted development countermeasures are of great significance for improving the development effect of CO₂ flooding.In this paper,according to the geological characteristics,fluid properties and development mode of low permeability reservoir,the conversion relationship between reservoir prototype and physical model is deduced by using the similarity theory of gas flooding physical simulation.The physical simulation flat model under different reservoir conditions is made,and the experimental scheme is designed,the flow law of fluid in the reservoir medium after CO₂injection in low permeability reservoir is studied.The migration and gas channeling law of CO₂displacement front are clarified,the main control factors are determined,and the channeling sealing measures are optimized.The research results show that although fracturing production increases the development effect in the short-term,it also exacerbates the occurrence of gas channeling.It is suitable for implementation in the low-permeability zone with strong heterogeneous reservoirs.Fracturing production can also change the displacement front.The law of movement changes the shape of the ripple.During CO₂ flooding,due to the viscous fingering phenomenon and the heterogeneity of the reservoir,gas channeling will occur and the affected area will decrease;the lower the crude oil viscosity,the earlier the gas breakthrough time,the weaker the viscous fingering phenomenon and the greater the affected area.Larger,the higher the degree of recovery;as the reservoir permeability increases,the gas breakthrough time is advanced,and the degree of gas channeling intensifies;strong heterogeneity will reduce the production area of the low-permeability zone,and the development effect will be worse;when the injection rate is small or large,the occurrence of gas channeling can be suppressed to a certain extent;when the well spacing is small,the premature breakthrough intensifies the gas channeling.Under the same injection rate,the five-point method has a stronger gas-channeling pattern,a more homogeneous reservoir is more suitable for the reverse seven-point well pattern,and the development effect of the heterogeneous reservoir row pattern is better.The injection-production coupling expands the swept volume of injected gas and inhibits the occurrence of gas channeling by changing the fixed flow direction of the underground fluid;the water-gas alternation improves the microscopic oil displacement efficiency by gas flooding and the water flooding improves the macroscopic sweep efficiency.Synergistic effect:by injecting foam to block the flow channel that has been formed,the injected gas is forced to diffuse and spread to the low-permeability area,and the degree of gas channeling can be suppressed to a greater extent.