Calculation Of Wellbore Parameters For CO₂ Displacement

Since the idea of CO₂ flooding in 1920,the research on carbon dioxide flooding technology has been carried out at home and abroad.At present,carbon dioxide flooding has become an increase in foreign oilfields.One of the main methods of recovery.In 2012,there were 325 oil production projects in the world,including 133 CO₂ flooding projects,accounting for 41%.Carbon dioxide flooding is an important method to improve oil recovery,and foreign carbon dioxide flooding technology is relatively mature.In the United States,the number of chemical flooding,thermal recovery projects and oil production has decreased overall in recent years,while the number of CO₂ flooding projects and oil production have shown an increasing trend.About 50%of the crude oil reserves of the 6.32 billion tons of low-permeability reservoirs that have been identified in China are unutilized reserves.Carbon dioxide flooding can significantly improve oil recovery in low-permeability and ultra-low permeability reservoirs.In the course of CO₂ injection,the bottom hole pressure and temperature of CO₂injection well are the main issues we concern.Because they directly determine the ability of achieving miscible displacement.If it fails to achieve miscibility near the bottom of the injection well,the whole reservoir can't be miscible with CO₂,because the bottom pressure of injection well is far higher than that of the oil reservoir,and thus it will seriously affect the effectiveness of CO₂ displacement.In the light of the energy balance equation of vertical conduit flow and combined with the computational method for the Ramey wellbore temperature distribution,this paper gives the distribution of well-bore pressure and temperature when CO₂ is injected at different injection pressures,injection temperatures and injection rates etc.And then we use VB to program some small-scale software,which can predict temperature,pressure and phase distribution along the wellbore after CO₂ has been injected.On this basis,we further discuss how to select the suitable injection temperature,pressure and rate.