Texaco Inc.

Texaco Development Corporation

Jack H Park

Joseph C Allen

Alfred Brown

Vernon H Schievelbein

Walter D Hunter

Joseph T Carlin

Ching H Wu

Richard H Widmyer

Timothy N Tyler

Stewart Haynes, Jr

Thomas J Morel

Disclosed is a process for the recovery of oil from a subterranean oil reservoir by miscible displacement using a predominantly nitrogen-containing gaseous displacing fluid which may contain lesser quantities of carbon dioxide. The miscibility of the first portion of the gaseous displacing phase injected into the formation is greater than the miscibility of the subsequent portion, as a consequence of increased concentrations of carbon dioxide and/or normally liquid hydrocarbons for the purpose of decreasing the time and distance which the gaseous nitrogen-containing displacing fluid must travel into the reservoir before attaining a conditionally miscible transition zone at reservoir conditions of temperature and pressure. The concentration of carbon dioxide and/or normally liquid hydrocarbons may be decreased in a reverse taper function, after which essentially pure nitrogen or nitrogen containing only minimal amounts of more soluble components may be injected into the formation.

Method of enhanced oil recovery employing nitrogen injection

Disclosed is an improved surfactant waterflooding enhanced oil recovery process employing a fluid containing as substantial in the only anionic surfactant, an ethoxylated and sulfated or ethoxylated and sulfonated surfactant. The degree of ethoxylation of the surfactant is determined by determining the degree of ethoxylation which produces the first inflection point in the electrical conductivity of a fluid as the degree of ethoxylation is increased from a value below that which causes solubility of the fluid in the aqueous environment in which it is tested to a value slightly greater than borderline solubility. Optimum results are obtained if the average degree of ethoxylation of the ethoxylated and sulfated or ethoxylated and sulfonated surfactant is from n-0.2 to n+0.1 and preferably from n-0.15 to n+0.05, where n is the degree of ethoxylation corresponding to the first inflection point in electrical conductivity.

Surfactant waterflooding enhanced oil recovery process

This invention relates to a method for treating wells completed in subterranean formations to form a mechanically stable, permeable mass which permits flow of fluids therethrough into or from the well, while restricting the movement of unconsolidated earth formation particles such as sand into the well. This method is especially suitable for treating producing wells in a subterranean formation being subjected to thermal oil recovery stimulation of viscous oil production such as by steam flooding, which causes rapid deteriation of consolidated sand or gravel masses formed with plastic resins. The method comprises contacting sand with an aqueous solution of calcium hydroxide, plus an effective amount of calcium salt having solubility greater than calcium hydroxide, such as calcium chloride, plus an alkalinity agent such as sodium hydroxide.

High temperature stable sand control method

A process for recovering hydrocarbons from a subterranean hydrocarbon-bearing formation by injecting into the formation via an injection well an aqueous alkaline flooding medium such as water, steam, etc. containing a small amount of a sulfonated, oxyalkylated interfacial tension reducer, forcing the said flooding medium through the formation and recovering hydrocarbons via a production well.

Oil recovery process using oxyalkylated additives

A two-step method for recovering hydrocarbons from a subterranean formation in which in situ combustion is first initiated in the formation by injection of air, for example, through an injection well, the injection of air is terminated and in a final step a fluid which is preferably water containing a small amount of a sulfonated interfacial tension reducer is injected into the formation whereby the fluid is heated as it passes through the hot formation and finally hydrocarbons are recovered via a production well.

Method for recovering hydrocarbons

The conformance of an enhanced oil recovery process, including waterflood, surfactant or other chemicalized water flood process, in a formation containing at least two strata or zones of varying permeability, the permeability of one zone being at least 50 percent greater than the permeability of the other zone, is improved by flooding until the higher permeability zone has been depleted, after which an aqueous fluid is injected into the high permeability zone, said fluid having relatively low viscosity at the time of injection and containing a particular surface active agent which promotes the formation of a coarse emulsion in the flow channels of the formation which reduces the permeability of the high permeability zone. After the permeability of the first zone has been reduced substantially, flooding may then be accomplished in the second zone which was originally not invaded by the injected oil recovery fluid since its permeability was substantially less than the permeability of the first zone. The surface active agents are individually tailored and the ratio of dissimilar surfactants balanced to exhibit optimum emulsion formation properties with the particular aqueous fluid present in the flow channels of the formation to be treated.

High conformance oil recovery process

Heavy or viscous oils may be recovered from subterranean deposits by one or more wells each of which is provided with at least two separate communication means from the surface of the earth, one in fluid communication with the upper part of the formation and the other well being in fluid communication with the lower part of the formation, each of said communication means being completed so as to permit injection of steam or mixtures of steam and other materials into the formation and production of heated viscous petroleum therefrom. A relatively impermeable barrier is formed between the portions of the formation where the communication is established, oriented horizontally and extending some distance into the formation. The oil recovery process comprises several separate phases of operation. In the first, steam is injected into the formation using both communication means simultaneously for a period of time followed by a soak period if desired, followed by production of heated oil from both parts of the formation using both communication means simultaneously. In the second phase, steam is injected into only one of the communication means, which may be the one in communication with either the top or bottom part of the formation, and oil production is taken from the other communication means. The horizontally-oriented impermeable barrier forces the steam to move a considerable distance into the formation away from the point of injection before moving back toward the production inlet. The injection-production sequences are then reversed, so the process effectively pressure pulses the formation to increase the distance into the formation that the push-pull steam injection process is effective.

Thermal oil recovery method

Surfactant oil recovery process in which an aqueous fluid containing petroleum sulfonate is injected into an oil formation containing water which is naturally fresh or which has been reduced to an acceptable salinity level by a pre-flush with fresh water is disclosed. Optimum oil recovery is achieved by determining the average equivalent weight petroleum sulfonate which produces the minimum interfacial tension in an oil-brine system similar to that present in the formation in which the surfactant is to be injected, and a petroleum sulfonate sample having an average equivalent weight which is from 2 to 20 percent and preferably from 5 to 15 percent less than the average equivalent weight of the sample which produced the minimum interfacial tension, or from 20 to 100 and preferably from 30 to 70 equivalent weight units less than the average equivalent weight of the sample which produced the minimum interfacial tension is used in the oil recovery process.

Surfactant oil recovery process

A method for separating bitumen from tar sand by solvent extraction with efficient separation of water from the recovered bitumen is disclosed. Tar sand may often be recovered by surface mining techniques. The tar sand is comprised of bitumen, water and sand including clays. The tar sand is contacted with bitumen solvent having a freezing point below that of the water, and the temperature of the mixture is lowered below the freezing point of the water in the tar sand. The solid ice crystals may then be easily removed along with the sand leaving a water-free liquid bitumen solvent mixture.

Method of separating bitumen from tar sand with cold solvent

Recovery of viscous petroleum from thick formations is especially difficult because thermal fluids or solvents needed to mobilize the viscous petroleum tend to channel through high permeability streaks in the formation, thereby bypassing large portions of the petroleum saturated formation. By forming or ensuring that there are naturally occurring high permeability strata in the upper portion and in the lower portion of the petroleum formation, and establishing separate communication means between the surface of the earth and the upper and lower high permeability strata, effective downward displacement may be achieved. A heated fluid such as steam is injected into one well in fluid communication with the lower high permeability strata to pass horizontally through the high permeability strata to another well which is also in fluid communication with the lower high permeability strata, sufficient to heat the lower high permeability zone to a temperature substantially above the ambient temperature of the formation. A solvent having a boiling point intermediate between the ambient temperature of the formation and the temperature to which the communication path is heated is injected into the heated communication path. The solvent vaporizes and moves up into the formation immediately thereabove to dissolve into the viscous petroleum. A gaseous substance is then injected into the upper high permeability strata to increase the pressure therein sufficiently to displace the mixture of viscous petroleum and solvent downward into the lower high permeability strata, wherein it is displaced horizontally to a remotely located well for recovery to the surface of the earth.

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Houston, TX, United States of America

Jack H Park