Enhanced oil recovery by injection of carbon di:oxide - and aq. wetting agent, both preceded by aq. foaming agent

A process for enhanced recovery of oil from a reservoir, using the injection of CO2 or similar gas, comprises the following steps. (i) An aq. soln.of a synthetic foaming agent is injected at an injection well. If the formation has a gas cap, this injection is made at its boundary, giving a foam curtain to prevent penetration of foam into the cap. (ii) CO2 or other gas is injected to displace the oil, with an aq. soln. of wetting agent to counter the tendency of asphaltenes sepd. out by the CO2 to deposit on the pore walls. (iii) Water, opt. satd. with CO2, is injected. Used esp. in formations of varying permeability. CO2 is not wasted by filling the gas cap. By the action of foaming and wetting agents, the vol. of oil removed per unit vol. injected is increased, as is the displacement of oil on the micro scale. L'invention concerne un procédé pour l'exploitation de gisements de pétrole au moyen d'anhydride carbonique et/ou de milieux contenant de l'anhydride carbonique et/ou d'autres milieux gazeux et par injection d'eau. Avant injection du gaz, on injecte un fluide moussant synthétique en vue d'augmenter le facteur volumétrique d'injection de la réserve pétrolifère, on injecte ensuite du gaz pour mobiliser l'huile en injectant simultanément des agents mouillants, puis comme étape finale on injecte de l'eau et/ou de l'eau contenant de l'anhydride carbonique après l'injection de gaz. Application à l'exploitation des gisements de pétrole.