| Since the 21st century, gas flooding gradually has developed into a mature EOR method. It has applications in major oil fields both in and out of the country, and it works enormously, which has become a widely-used technology to increase oil recovery in mature reservoirs. Injecting CO2 flooding is very vulnerable to form miscible flooding, as many reservoir experts keep appealing that reducing the emission of greenhouse gas like CO2 in world-scale is of great urgency, which will largely motivate the development of developing of CO2 flooding. Injecting CO2 gas into the reservoir, which is the joint point that takes both emission of greenhouse gas and rationalizing use of resources, it is a win-win to everyone.In this paper, I take a crude fluid of H3 area in H reservoir for study. At first, I can carry out the corresponding laboratory study and numerical simulation studies. Second, according to oil viscosity, interfacial tension and C2--C6 molar content in oil phase, we can explain the miscible flooding mechanism of CO2 injection, and analyze different studies of gas injection, under pressure for different driving parameters on these parameters. Based on single phase fluid stable percolation theoretical mechanism, and the equations of reservoir pressure distribution, we can derive a theoretical modal of one-dimensional CO2 injecting miscible flooding mathematical model. Last but not least, combine all of experimental data into the model equation. Calculate the length of the miscible zone, and determine the position of the miscible zone. On top of that I should take slim tube experiment results into consideration to verify the accuracy of the model.Through CO2 injection slim tube experiment and simulation of miscible flooding Mathematical Model, we have a better understanding of:(1) After injecting CO2 gas, intermediate hydrocarbon components of C2-C6 are extracted, oil viscosity reduces, and viscosity of crude oil in displacement front may be the least. After mixing with the oil, viscosity is higher than that of displacement front, and miscible evaporated gas flooding conditions are met.(2) Under the same injection rate, the bigger the injecting pressure is, the narrower the transitional zone is; Similarly, under the same injecting pressure, the more we inject, the broader the transitional zone is, which will be much more far away from the injecting end.(3) Under the same conditions of gas injection, compared to the effect of flooding pressure on the miscible zone length. The greater the pressure, the longer the miscible length is. With the increase of injecting CO2 gas, in the beginning it cannot form a mixed phase, but when the injection volume is large enough, the oil viscosity is reduced to a certain value, it begins to appear on the miscible zone, miscible with CO2 gas and the length broadens, and the oil recovery increases. The location of miscible zone will appear with the gas injection rate increases, moving to the rear end of the slim tube.(4) Because the average viscosity is adopted in the calculation, the calculation of the miscible zone is more close to the back and the length is shorter than the simulation.(5) The calculation results of mathematical model agree well with the simulation results of slim tube experiment, which shows that the model is correct. |
PDF Full Text Request