This paper describes a procedure for evaluation of an important aspect of the suitability of a reservoir for CO2 flooding. The concern addressed is whether the attainable injection pressure will be sufficient to compress the CO2 to the density required for efficient carbon dioxide flooding. The relevant factors--the required mimimum miscibility pressure (MMP), and the regional geothermal and fracture gradients--are reviewed briefly. Available data are fit to simple equations, and a formula is given which permits computation of the estimated pressure margin in CO2 floods. This is the excess of the attainable bottomhole injection pressure over the MMP, and it can be used as a figure of merit for this aspect of flood design. A reasonably high value of the pressure margin would need to be combined with other favorable factors to indicate that prospects were good for a successful CO2 flood. Since the fracture pressure increases with depth faster than the required miscibility pressure, the operating pressure margin normally increases with depth. Graphical correlations are presented to permit a quick estimate of the potential for CO2 flooding if only the reservoir depth and API gravity of the oil are known.

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