Recovery of oil from a subterranean reservoir employing an alkaline agent-sulfonate surfactant system in conjunction with the injection of a sacrificial system comprising an inorganic polyphosphate and an alkali metal carbonate. An aqueous initiaion slug containing an inorganic polyphosphate, an alkali metal carbonate and an alkaline agent selected from the group consisting of alkali metal and ammonium hydroxides is injected into the reservoir. The initiation slug is followed by the injection of an aqueous surfactant slug which contains an alkaline agent and a sulfonate surfactant. After injection of the surfactant slug, an aqueous flooding medium is injected in order to displace the oil within the reservoir to a production system from which it is recovered. The surfactant slug may also contain an inorganic polyphosphate and alkali metal carbonate and the concentrations of these agents in the surfactant slug may be lower than in the initiation slug.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of pending U.S. patent application Ser. No. 553,697, filed Feb. 27, 1975, by Harry L. Chang.
An oil recovery process in which oil is displaced by a viscous alkaline aqueous solution is improved by using such an aqueous alkaline solution containing a water-thickening polymer partially hydrolyzed polyacrylamide polymer and a stabilizer consisting essentially of a 2-mercaptobenzothiazole in the presence of a sulfur-containing oxygen scavenger. A readily oxidizable alcohol or glycol may also be included.
A method for reducing retention of a polymer based displacement agent injected into a hydrocarbon containing rock matrix involves treating the matrix with an adsorbent solution containing alkali metal phosphates after the rock matrix comprising clays has been stabilized by injection of a solution containing cations obtained from KCl or NaCL salts. The presence of the cations increases the effect of the adsorbent solution.
In a continuous or cyclic steam foam drive, recovery of an acidic reservoir oil (1) is improved by injecting steam accompanied by (a) enough dissolved alkaline monovalent salt to ion-exchange multivalent cations from the reservoir rocks and precipitate those ions in compounds which are insoluble in an alkaline aqueous liquid as well as forming soaps of the reservoir oil acids and (b) surfactants for foaming the steam and increasing the salt tolerance of an aqueous surfactant system containing the soaps of the reservoir oil acids, and (2) is further improved by using trona or an equivalent mixture of alkali metal carbonates and bicarbonates as the alkaline monovalent salt.
Steam injected into a subterranean formation comprises a liquid phase and a vapor phase. Oil displacement by the liquid phase is not as efficient as the oil displacement in the portion of the formation contacted by the vapor phase. The effectiveness of the oil recovery process in the portion of the formation being contacted by the liquid phase is increased by contacting that portion of the formation with an aqueous solution containing from 0.005 to 2.0 percent by weight of an alkalinity agent, preferably sodium hydroxide, and from 0.01 to 5.0 percent by weight of a buffering agent, preferably sodium carbonate. The mixture of sodium hydroxide and sodium carbonate may be co-mixed with the steam introduced into the formation, or may be introduced as a separate liquid containing both the sodium carbonate and sodium hydroxide, or separate slugs containing sodium carbonate and sodium hydroxide may be injected.
The effectiveness of a water injection oil recovery process is increased by incorporating a viscosifying amount of a hydrophilic polymer in the injection fluid, together with from 0.005 to 2.0 percent by weight of an alkalinity agent, preferably sodium hydroxide, and from 0.01 to 5.0 percent by weight of an alkalinity stabilizing agent, preferably sodium carbonate. The hot alkaline polymer water flood is especially effective when applied after a steam flood to recover oil bypassed by the steam.
