| Currently, many oil fields in China have entered into the middle or later development period, when the production of the oil begins to decline quickly. So air-foam injection is a new and economical technology to improve oil recovery in middle and high permeability fields. Using air foam technology in block Ming-15 in Zhongyuan oil field can overcome the gas breakthrough when air is injected in heterogeneous reservoirs and has efficient displacement characteristics. This thesis focuses on the development of Ming 15 block in Zhong yuan oil field. In research, using static oxidation and dynamic oxidation laboratory experiments, foam select and evaluation tests and air foam flooding experiments in homogeneous and heterogeneous models to research the mechanisms of air foam injection for enhanced oil recovery.Using static and dynamic oxidation reaction experiments can demonstrate that Ming 15 oil has the excellent characteristics of oxidation. The pressure can accelerate the oxidation reaction, but the extent is not big. The higher temperature can make the oxidation reaction more acute. The formation fluids also have some effect. Salinity can accelerate the reaction, and different inorganic salts have the different effects, the chemical valence is higher, the effect is bigger. The foam is helpful to oxidation reaction. The solid material in the reservoir also has some effect, the clay`s effect is small and it can be ignored. Compare the oxidation reaction experiments of crude oil and oil sand, the oxidation reaction rate is bigger in oil sand, also adding formation core can accelerate the reaction. The dynamic oxidation reaction experiments can make the air-foam and oil contact closely, and it can exactly respond the low temperature oxidation experiments. Based on the experiments, the LTO kinetics model is founded initially.Zhong yuan Ming 15 block belongs to high temperature, high salty reservoir. Using the experiments can select the salt resisting and temperature resisting ZY-1 foam system, then begin to evaluate the blocking ability of the foam system. The higher the temperature, the smaller the resistance factor in the porous medium. The higher the pressure, the bigger the resistance factor .The ZY-1 foam system has a good salt resisting, the higher the salinity, the bigger the resistance factor. And the higher the injection rate, the bigger the resistance factor. Then use different injection mode to displace the foam slug. When using air to displace the foam slug, air is easy to break out, so at first the resistance factor increase, then the factor begins to decrease, but using water to displace the foam slug, at a long time the resistance factor continues to increase until inject water is 2 times of pore volume, then the resistance factor begins to decrease slowly. When using the different influent rate to displace the foam slug, both of air and water, the higher rate, the bigger the resistance factor.In order to study the functions of air foam injection in middle or high permeability heterogeneous reservoirs, according to the reservoirs characteristics of Ming 15 block, found the homogeneous and heterogeneous models to study the application of air foam injection. About the homogeneous models, the higher the permeability, the higher the recovery, also after the water injection, using air injection and air-foam injection can enhance oil recovery further. Using heterogeneous model displacement experiment, when injected fluid has broken out from the high permeability section, then most of the fluids flow through the low resistance section, least of fluids flow through the low permeability section, displacement efficiency becomes small, recovery remains stationary. Consider this situation, use air foam injection to block the high permeability section and capacity channel. Air foam injection can improve oil recovery further and enhance the recovery of the integral reservoirs. So the experiments study can demonstrate that air foam injection is a secure and effective technology to improve oil recovery. |
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