| In recent years, gas injection flooding improves recovery technology developing rapidly. Carbon dioxide flooding is the most popular of them. On one hand,effect of carbon dioxide flooding is very obvious; On the other hand, the use of carbon dioxide can mitigate the greenhouse effect, the result in carbon dioxide flooding more and more popular in the world. However, the gas viscosity is very low,the current speed of gas is fast than the oil which must cause gas channeling. How to control the mobility ratio in the process of gas injection to improve gas macroscopic sweep efficiency is always the concern of people, injection of gas and water in turn and foam system injection can control the mobility and stable displacement front, by this way, it can greatly improving the efficiency of macro oil displacement, So it has been widely used in oilfield production practice.This paper is based on the collection and analysis of the literature, According to the characteristics of low permeability, strong heterogeneity and high-water cut of S reservoir, We Use indoor long-core device with cores coming from formation compose into a double-tube model, and reconfigure the fluid samples.Simulate multiple sets of contrast experiment under different pressue, different moisture content, different slug size and different size ratio of S-reservoir pormation pressure 31MPa and pormation temperature 125?. we optimize the best injection-production parameters through comparison. Get the following results:(1) Differen moisture-content parameters include four experiments of 0%,60%,80% and 100%. Moisture-content parameters influences the factors of gas injection time and gas breakthrough time, the earlier gas injected the later gas break, make for improving crude oil mobility ratio. Moisture-content of 0%is the highest recovery rate, the total recovery rate can reach 69.22%, the high permeability group was 83.73% and 54.04% for low permeability group. Compared to the moisture-content of 100% it's total oil recovery enhance 8.4%.(2) Different displacement-pressure parameters include four experiments of 25MPa, 28MPa,31MPa and 35MPa. Different displacement-pressure parameters mainly affect the octor of CO2 miscible with crude oil, the bigger of the pressure the easier it miscibles with crude oil, So can reduce the interfacial tension of oil-gas, crude oil viscosity and enhance oil recovery.35MPa displacement-pressure is the highest recovery rate, the total recovery rate can reach 62.90%, the high permeability group was 77.64% and 47.49% for low permeability group. Compared to the 25MPa it's total oil recovery enhance 6.62%.(3) Different slug-size parameters include three experiments of 0.05PV,0.1 PV and 0.15PV. the smaller the slug-size is, the more times the water-gas alternating injection, and the later gas break, make three phases fully contact, improve the oil-phase mobility ratio and reduce the viscosity of crude oil.0.05PV is the highest recovery rate, the total recovery rate can reach 69.17%, the high permeability group was 79.40% and 58.46% for low permeability group. Compared to the 0.15PV it's total oil recovery enhance 13.3%.(4) Different slug-ratio parameters include four experiments of 1:1,1:2,2:1 and 1:0. Small gas-water ratiocontact can conducive to a good contact with crude oil and CO2, reduce the viscosity of crude oil, delay the gas breakthrough time.1:2 is the highest recovery rate, the total recovery rate can reach 71.21%, the high permeability group was 82.66% and 59.21% for low permeability group. Compared to the 1:0 it's total oil recovery enhance 19.73%.(5) Foam flooding maybe due to most of the injected CO2 infused into foam, Lead to its contact with crude oil rarely, the effect is worse than gas-water alteenating displacement after foam flooding. The total recovery differ 16.39%... |
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