Method of assisting the recovery of petroleum in vertically fractured formations utilizing carbon dioxide gas to establish gravity drainage

摘要

The invention relates to assisting the recovery of petroleum from vertically fractured formations utilizing carbon dioxide gas to lower the interfacial tension between the gas and the petroleum in the vertical fractures and in the formation matrix adjacent the vertical fractures to cause vertical drainage of the petroleum down the fracture system. The invention also includes a method for identifying vertically fractured formations which may be particularly susceptible to such recovery with carbon dioxide gas using the capillary to gravity ratio (1/N.sub.B) to select formations having a value for such ratio of 0.2 or less.