FR2235262A1 - Secondary recovery from oil-bearing formations - by injection of carbon dioxide - Google Patents

Abstract

Secondary recovery from oil-bearing formations is effected by (a) injecting CO2 gas or a mixt. of CO2 and gaseous hydrocarbons contg. 65-90% CO2 into the formation through one or more injection wells until the pressure reaches the initial formation pressure, the producing wells meanwhile being kept in production, even if the production is 100% H2O; and then (b) injecting water intermittently or continuously into the formation during the whole prodn. period. The process is esp. useful in oil fields with a local supply of natural CO2 (as in Hungary). The injected gas increases the vol. of the water and oil in the formation, improves their flow properties and removes the film of oil adhering to the formation, without causing sepn. of asphalt or paraffin, pptn. of dissolved salts or swelling of clay minerals.