In the later stage of heavy oil reservoir development by steam injection

the steam channeling is serious and the development effect gets worse year by year.So it is urgent to apply relevant technologies to improve steam flooding performance.According to the characteristics of the heavy oil reservoir in Z32 Qigu Formation in Fengcheng Oilfield

the feasibility of steam flooding assisted by CO

2

injection to

improve the development effect has been studied.In the process of steam injection in heavy oil reservoir

the injection of CO

2

N

2

or flue gas can make crude oil swell

increase formation elastic energy

reduce viscosity of crude oil and improve oil flow capacity of crude.The swell and viscosity reduction effects of different types of injected gas on heavy oil have been measured by high temperature and high pressure crude oil sampler and core flow experiment device.The volume expansion of crude oil is about 10 %～40 %

2 %～10 % and 4 %～16 % by injecting CO

2

N

2

and simulated flue gas respectively

the viscosity is reduced by 27.3 %～82.9 %

4.3 %～18.5 % and 10.2 %～45.8 %

respectively

and the oil recovery is enhanced by 5.83 %

3.08 % and 3.75 %

respectively.Therefore

CO

2

is recommended as the injection medium.Field application shows that after the new technology is implemented

the daily oil production of the well group increases from 26.6 t to 36.2 t

the oil steam ratio increases from 0.174 to 0.206

and the total oil production increases by 1 158 t.Remarkable economic benefits are obtained

which provides references for the scale application of this new technology.