Research On Phase Behavior And Development Method For Reservoir With Big Gas Cap And High CO₂ Content

For reservoir which has thin oil rim with big condensate gas cap on top and aquifer below,as well as extremely high CO₂ content belongs to a special reservoir type,the development of this kind reservoir is a complicated project,and successful development cases are rarely reported around the world.Taking the deep water K oilfield in Brazil as example,reservoir type,phase behavior characteristics and equation of state?EOS?,development of adaptability and technical policy,as well as the actual reservoir development method were systematically studied in this paper,with PVT test,reservoir engineering and compositional numerical simulation methods.The study results show: The particular of K oilfield is since the CO₂ from deep strata thrusted into the black oil reservoir,presenting the character of CO₂ on the top and heavy oil rim at the bottom.Considering the differences between gas and oil,two sets of EOS equations are built to characterize their fluid phase behavior.Development mechanism research shows,high oil recovery factor can be achieved by using vertical wells to develop gas cap and re-inject separated gas,horizontal wells to develop thin oil rim.Classifying the development units based on the actual reserves and structural differences of K oilfield,and using two sets of wells to develop gas and oil respectively,20.7% of oil recovery factor and simultaneous and efficient development of hydrocarbon can also be achieved.The research work offers important reference to develop reservoir with the same characters like K oilfield.