Abstract: Improved sweep efficiency is obtained in an oil recovery process wherein oil is recovered from a subterranean, viscous oil containing formation having relatively highly permeable zones and relatively low permeability zones penetrated by at least one injection well and at least one spaced apart production well in fluid communication with a substantial portion of the formation. First, a predetermined amount of gel solution is injected into the formation at high pressure to deeply penetrate and plug the fracture face and highly permeable zones of the formation. Thereafter, a breaker material such as hydrochloric acid is injected into the formation at a low pressure to break the gel and displace it from the fracture face and highly permeable zones in the vicinity of the injection well thereby reestablishing injectivity into the formation in the vicinity of the injection well.

Abstract: Relatively high permeability zones in a subterranean formation vertically bounded by relatively low permeability zones are selectively plugged by first injecting a solidifiable selective gel solution, preferably a xanthan/chromium gel solution, at a pressure sufficient to cause the gel solution to coat and temporarily plug the injection face of the low permeability zones without any significant amount of the gel penetrating the low permeability zones while allowing the gel solution to flow into the relatively high permeability zones. Reasonably promptly thereafter and before the selective gel solution solidifies in the high permeability zones, a solidifiable non-selective solution is injected into the formation that preferentially enters the relatively high permeability zones and allowed to solidify and plug the relatively high permeability zones.

Abstract: High permeable thermally fluid swept zones in an oil containing formation are selectively plugged by a high temperature selective gel-forming solution without plugging the less permeable unswept portion of the formation. Ungelled solution in the less permeable unswept portion of the formation in the vicinity of the injection well is removed and a thermal fluid is injected into the formation that sweeps oil from the less permeable, unswept portion of the formation, thereby resulting in more complete displacement of oil from the formation.

Abstract: Oil recovery from a subterranean, oil-containing formation having relatively highly permeable and/or fractured zones and relatively low permeability zones is improved by first injecting a predetermined amount of a plugging agent into the formation, preferably inorganic, non-polymeric solids suspended in a fluid such as drilling muds or bentonite or clay suspensions, that plugs the face of the highly permeable and/or fractured zones of the formation. Thereafter, injection of the plugging agent is continued or in the alternative a displacing fluid at a flow rate and pressure sufficient to initiate and propagate new fractures and/or extensions of existing fractures in the formation. Thereafter, a displacing fluid is injected into the formation at a pressure sufficient to maintain the new fractures and/or extensions of existing fractures open and displace oil from zones communicating with the new fractures and/or extensions of existing fractures toward a production well where it is recovered.

Abstract: A method for inhibiting the formation of scale and corrosion in a well penetrating a subterranean formation for the production of fluids from the formation comprising injecting a predetermined amount of microparticles of a basic anion exchange resin providing a source of polycations into the formation about the well and that are trapped and retained by the interstices of the formation without rendering the interstices or the formation impermeable to the flow of fluids. Thereafter a predetermined amount of an aqueous solution of scale and corrosion inhibitor is injected into the formation about the well that contacts the basic anion exchange resin and becomes fixed in a slightly soluble state either by complexation with the polycations or is precipitated by the polycations in the exchange resin. The scale and corrosion inhibitor is released slowly at effective concentration into fluids produced by the well to inhibit scale formation and corrosion.

Abstract: A method for inhibiting the formation of scale and corrosion in a well penetrating a subterranean formation for the production of fluids from the formation comprising injecting a predetermined amount of microparticles of a cation exchange resin loaded with the desired cations into the formation about the well that are trapped and retained by the interstices of the formation without rendering the interstices or the formation impermeable to the flow of fluids. Thereafter a predetermined amount of an aqueous solution of scale and corrosion inhibitor is injected into the formation about the well that contacts the cation exchange resin and becomes fixed in a slightly soluble state either by complexation with the cations or is precipitated by the cations in the exchange resin. The scale and corrosion inhibitor is released slowly at effective concentration into fluids produced by the well to inhibit scale formation and corrosion.

Abstract: Improved vertical and/or horizontal sweep efficiency in a deep subterranean oil containing formation having a temperature in excess of 250.degree. F. containing relatively high permeability zones and relatively low permeability zones is obtained by injecting an aqueous polysulfide solution into the formation that preferentially enters the relatively high permeability zones and allowing the aqueous polysulfide solution in the relatively high permeability zones to disproportionate under the temperature conditions within the relatively high permeability zones to form a precipitate of elemental sulfur in situ which plugs the relatively high permeability zones in the formation. Thereafter, improved sweep efficiency is realized in displacing oil from the lesser permeable zones.

Abstract: The relatively highly permeable zones of a subterranean oil containing formation having a neutral to alkaline pH are selectively plugged by initially injecting an aqueous acid solution into the relatively highly permeable zones that lowers the pH of these zones to about 6 or less. Thereafter, an aqueous polysulfide solution is injected into the formation that preferentially enters the relatively highly permeable zones and allowed to disproportionate under the pH conditions within the relatively highly permeable zones to form a precipitate of elemental sulfur in situ which plugs the relatively highly permeable zones in the formation. Thereafter, improved sweep efficiency is realized in displacing oil from the lesser permeable zones. If the natural pH of the relatively highly permeable zones in the formation is about 6 or less, the initial treatment with the aqueous acid solution is unnecessary.

Abstract: In a CO.sub.2 miscible displacement enhanced oil recovery process, produced CO.sub.2 -hydrocarbon gas containing from more than the maximum CO.sub.2 content tolerable in a fuel gas up to about 70 volume percent CO.sub.2 is reinjected into a small portion of the well pattern volume and produced CO.sub.2 -hydrocarbon gas containing more than 70 volume percent CO.sub.2 is reinjected into a larger portion of the well pattern volume. The method provides a more effective utilization of CO.sub.2 in a CO.sub.2 miscible enhanced oil recovery process while maintaining most of the oil-containing formation under miscible conditions.

Abstract: A method for the recovery of oil from a subterranean, oil-containing formation by a cyclical steam flood-pressurization and production program. During the first cycle, steam is injected into the formation and oil is recovered until there is steam breakthrough at the production well. Thereafter, a pressurization cycle is initiated by throttling or shutting-in the production well while continuing injection of the steam until the bottomhole injection pressure is greater than the vertical pressure created by the overburden thereby causing the formation to fracture horizontally. After the horizontal fracture is formed, the third cycle or production cycle is initiated in which oil is recovered from the formation from either the production well or the injection well or both until the amount of oil recovered is unfavorable.

Abstract: A viscous oil-bearing formation is produced by a steam flood technique in which the quality of the steam injected into the formation through an injection well is improved in-situ by the generation of an in-situ heat zone which trails along behind the front of the steam flood. This in-situ heat zone is generated by the injection of a non-condensable oxidant which reacts with the residual oil left behind the steam front in the steam swept zone. The oxidant injection is controlled so that the velocity of the heat zone through the formation is no greater than the velocity of the steam front, thereby preventing heat zone breakthrough of the steam front.

Abstract: Oil is recovered from a subterranean oil-containing formation by fracturing the formation around the injection well and thereafter injecting a CO.sub.2 foam or a mixture of steam and a CO.sub.2 foam into the injection well to displace mobilized oil toward a production well for recovery.

Abstract: Oil is recovered by a CO.sub.2 miscible oil recovery method in which the CO.sub.2 minimum miscibility pressure of the oil-containing formation is lowered by injecting a coolant into the formation. The formation is then pressurized to a pressure at least that of the reduced CO.sub.2 minimum miscibility pressure by injecting a fluid therein. A slug of carbon dioxide is then injected into the formation at the formation pressure whereby the carbon dioxide is miscible with the formation oil and thereafter a driving agent is injected to displace the formation oil and carbon dioxide toward a production well from which oil is produced.

Abstract: This specification discloses a method for the recovery of oil from a subterranean, viscous asphaltic oil-containing formation comprising injecting a predetermined amount of a solution comprising an aromatic hydrocarbon and an acid selected from the group consisting of phenol, carboxylic acid, and acidic anhydrite. Thereafter, the formation is subjected to a thermal recovery technique such as steam flooding or an in-situ combustion operation and oil is recovered.

Abstract: In a cyclic method of solvent stimulation of a single oil well penetrating a viscous crude oil-containing formation, the well is first produced and a portion of the produced crude oil is subjected to a visbreaking operation to produce a hot visbroken crude oil having reduced viscosity. Production is terminated and a predetermined amount of the hot visbroken produced crude oil is injected into the formation via the well as a solvent, the formation is allowed to undergo a soak period, and the well is returned to production. Thereafter, production may be continued until the percentage of visbroken crude oil in the produced fluids is less than 12 percent and the above cycle may be repeated.

Abstract: A method for the recovery of viscous crude oil from a subterranean, viscous crude oil-containing formation penetrated by an injection well and a spaced-apart production well wherein produced crude oil recovered from the production well is subjected to a visbreaking operation to produce a hot visbroken crude oil solvent reduced in viscosity and injecting the hot visbroken crude oil solvent into the formation via the injection well to reduce the viscosity of oil remaining in the oil formation and thereby enhance recovery of oil from the formation. A predetermined amount or slug of the hot visbroken crude oil solvent may be injected into the formation followed by injection of another fluid such as a gas or an aqueous fluid to drive the hot solvent and the oil through the formation toward the production well for recovery of fluids including oil.

Abstract: A method for determining the CO.sub.2 minimum miscibility pressure (MMP) is disclosed which comprises filling a coiled capillary tube with oil at a predetermined temperature T.sub.1 and an initial predetermined pressure P.sub.1 less than the CO.sub.2 MMP. Carbon dioxide is injected into the capillary tube at a fixed flow rate F.sub.1 to displace the oil while maintaining the temperature of the oil at T.sub.1 and the pressure at P.sub.1. The pressure drop across the capillary tube and the volume of carbon dioxide injected is constantly measured. The pressure difference versus volume of carbon dioxide injected data is plotted and the pressure drop .DELTA.P.sub.1 at the point of inflection where the second derivative goes from a negative value to a positive value is determined graphically. The previous steps are repeated while maintaining T.sub.1 and F.sub.1 constant at a different pressure P.sub.2 less than the CO.sub.2 MMP and .DELTA.P.sub.2 at the inflection point of pressure versus volume of CO.sub.

Abstract: The displacement efficiency of a steam drive process is improved and steam override reduced by rapidly injecting a predetermined amount of high temperature steam via an injection well into the formation to visbreak a portion of the oil in the formation prior to a steam drive wherein steam is injected into the formation via the injection well to displace oil to a spaced-apart production well through which oil is recovered. The visbroken oil provides a more favorable transition of mobility ratio between the phases in the formation thereby reducing viscous fingering and increasing the displacement efficiency of the steam drive. In addition, after a predetermined amount of high temperature steam has been injected into the formation, the formation may be allowed to undergo a soak period prior to the steam drive. The high temperature steam injection and soaking steps may be sequentially repeated for a plurality of cycles.

Abstract: A method for recovering oil by injecting an oxygen-containing gas containing at least 50 vol. % oxygen into the formation to initiate an in-situ combustion operation, separately producing oil and a flue gas from the formation, and separating carbon dioxide from the flue gas to produce a combustible gas.

Abstract: In a thermal method for the recovery of oil from a subterranean, viscous oil-containing formation, steam in an amount ranging from 0.3 to 0.5 pore volume and an injection rate within the range of 4.0 to 7.0 bbl/day/ac.-ft. is injected into the formation via an injection well completed in the lower 50% or less of the formation and fluids including oil are recovered via a spaced-apart production well completed in the upper 50% or less of the formation. The injection well is then shut-in for a variable time and thereafter a predetermined amount of hot water or low quality steam is injected into the formation via the injection well in an amount ranging from 0.03 to 0.10 pore volume and at an injection rate of 1 to 2.0 bbl/day/ac.-ft. The method is applied to viscous oil-containing formation in which either naturally occurring or induced communication exists between the injection well and the production well in the bottom zone of the formation.