Mobil Oil Corporation

Mobile Oil Corporation

Billy G Hurd

An alkaline flooding oil recovery process is enhanced by injection of aqueous solutions of foam-forming surfactant and gases, or pre-formed foams, either ahead of or behind conventional alkaline slugs. In a preferred embodiment, a slug of an aqueous solution containing an alkaline agent followed by a driving fluid is injected into the formation that displaces oil through the relative high permeability zones of the formation and oil is recovered via the production well. Thereafter, a slug of an aqueous solution of a foam-forming surfactant is coinjected into the formation with a gas creating a foam when the gas mixes with the foam-forming surfactant in the aqueous solution. The foam created from the aqueous surfactant and gas will go preferentially into the formation zones of relatively high permeability and low oil saturation substantially plugging these zones. Thereafter, a slug of an aqueous solution containing an alkaline agent is injected followed by a driving fluid that displaces the aqueous solution containing an alkaline agent and oil through the less permeable zones of the formation toward the production well and oil is recovered from the formation via the production well. This process improves volumetric sweep efficiency and/or reduces effective mobility ratio of released oil and displacing fluids thereby enhancing displacement of oil to the production well and total oil recovery.

Method for using foams to improve alkaline flooding oil recovery

Volumetric sweep efficiency and oil recovery by CO.sub.2 flooding processes may be increased by injecting a surfactant solution into the formation which will form a gel in-situ in the high permeability zones via interaction of the surfactant with formation brine, oil, and CO.sub.2 under formation conditions. Thereafter, improved oil recovery efficiency is realized in displacing oil from the lesser permeability zones. The surfactant solution is selected from phase behavior experiments which show gel precipitation at conditions of temperature, salinity, oil composition, and CO.sub.2 pressure which are expected to exist or may be practically established in the particular oil-containing formation. Preferably, the gel is precipitated at CO.sub.2 pressures above the minimum miscibility pressure for CO.sub.2 miscible flooding, and below the prevailing formation pressure during the CO.sub.2 flooding. The surfactant solution may be injected into the reservoir as an aqueous solution or as a microemulsion solution prepared in surface mixing facilities. The surfactant solution may also be injected prior to injection of CO.sub.2, or may be alternately injected in WAG cycles following CO.sub.2 breakthrough into production wells.

Method for improving sweep efficiency in CO.sub.2 oil recovery

Waterflooding process for the recovery of oil from a subterranean formation in which at least a portion of the injected fluid consists of an oil slug containing a preferentially oil-soluble alcohol and a preferentially oil-soluble ether-linked sulfate or sulfonate. Specifically disclosed ether-linked surfactants include sulfonated or sulfated polyethoxylated alkylphenols. Specifically disclosed alcohols include aliphatic alcohols containing from 5 to 7 carbon atoms and having a water solubility of less than 3 percent.

Oil recovery by surfactant-alcohol waterflooding

An improved recovery process is provided for fluent petroleum in a porous formation having spaced injection means and production well recovery means which includes a concentrated brine drive and surfactant carrier system. Advantageously, an effective aqueous surfactant composition is formulated containing a water-soluble ether-linked sulfonate surfactant, a cosolvent alcohol, and at least one cosurfactant (as for example, petroleum sulfonate or alkylbenzene sulfonate) or sacrificial sulfonate material in a concentrated brine carrier.

Method for surfactant waterflooding in a high brine environment

There is provided a process for improving oil recovery from stratified reservoirs by (1) injecting low saline water to reduce the salinity in high permeability zones, (2) injecting a surfactant solution into the high permeability zones, (3) injecting high salinity water into the reservoir, thereby forming a surfactant/water/oil emulsion which reduces effective brine permeability in the high permeability zones, and (4) continuing to inject high salinity water into the reservoir, whereby water is diverted to low permeability zones and oil is recovered from the low permeability zones. Low salinity water may then be injected to break-up or release the emulsion in the high permeability zones and to recover oil from the high permeability zones.

Oil recovery process for stratified high salinity reservoirs

An improved recovery process is provided for fluent petroleum in a porous formation having spaced injection means and production well recovery means which includes a concentrated brine drive and surfactant carrier system. By injecting an aqueous drive medium having gradually decreasing brine concentration, surfactant transport and petroleum recovery efficiency are improved. Advantageously, an effective aqueous surfactant composition is formulated containing a water-soluble ether-linked sulfonate surfactant, a cosurfactant alcohol, and at least one cosurfactant or sacrificial sulfonate material in a concentrated brine carrier.

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Dallas, TX, United States of America

Billy G Hurd