In Situ Recovery Of Oil From Tar Sands Using Water-external Micellar Dispersions

Abstract

Hydrocarbon from subsurface tar sands having an injection means in fluid communication with a production means is recovered by first heating the tar sands, then injecting a water-external micellar dispersion into the tar sands, and thereafter displacing the dispersion toward the production means and recovering the hydrocarbon through the production means. The tar sands are heated to a temperature sufficiently high to cause the incoming micellar dispersion to become heated to a temperature of at least about 100.degree.F upon entering the tar sands. The micellar dispersion can be preceded by a slug of hot water which can optionally have a pH greater than about 7. Also, the micellar dispersion can have a pH of about 7-14 and preferably a temperature up to about 100.degree.F. The micellar dispersion contains hydrocarbon, surfactant, aqueous medium, and optionally cosurfactant and/or electrolyte.

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of our copending application titled "In Situ Recovery of Oil from Tar Sands Using Water-External Micellar Dispersions," Ser. No. 888,897, filed Dec. 29, 1969 and now U.S. Pat. No. 3,637,018.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the recovery of hydrocarbon from tar sands by an in-situ process using a water-external micellar dispersion. The tar sands are first heated, then the micellar dispersion (contains hydrocarbon, surfactant, and aqueous medium) is injected and displaced through the tar sand formation.

2. Description of the Prior Art

Tar sands, also known as oil sands and bituminous sands, are sands that contain a very viscous hydrocarbon. One of the largest deposits is the Athabasca sands found in Northern Alberta, Canada. The appearance of such sands is generally asphaltic, due to the viscous hydrocarbon. Oil or hydrocarbon from tar sands is substantially more viscous than crude oil obtained from the normal oil-bearing subterranean formation.

It is known in the prior art that hydrocarbon from tar sands can be recovered by first flooding with steam and then following this steam flood with an aqueous solution of sodium hydroxide. The sodium hydroxide slug aids in emulsification of the oil in the tar sands.

U. S. Pat. No. 2,882,973 to Doscher et al. teaches the use of an aqueous solution containing a nonionic surface-active agent and optionally a neutral salt, the solution at a pH of at least 12. Examples of useful nonionic surfactants include oil-soluble monohydric alcohols, oil-soluble dihydric alcohols, and oil-soluble alcohols containing substituents such as ether and/or ester groups. The nonionic surfactant is present in sufficient concentration to effect instantaneous or spontaneous emulsion of the oil or tarry material present in tar sands and to maintain it in the emulsified state. Concentrations of 0.1-5 percent by weight are effective for this purpose. The high pH is obtained by adding alkali metal hydroxide or ammonia.

U. S. Pat. No. 3,375,870 to Satter et al. teaches an in situ process for recovering hydrocarbon from tar sands by heating the tar sands to a temperature above 300.degree.F., then using "recognized recovery methods" to recover the hydrocarbon. Examples of such processes are waterflooding, steam injection, forward combustion and gas injection.

Also, combustion processes have been used to recover the oil. Air in injected into the tar sand reservoir and the hydrocarbon and air combusted. The fire front distills the oil ahead of it, fuel for the fire is mostly coke deposited by the destructive distillation.

SUMMARY OF THE INVENTION

Applicant has discovered a novel method of recovering oil from tar sands by injecting a water-external micellar dispersion into heated subsurface tar sands and displacing the dispersion toward a production means in fluid communication with the tar sands. The heated tar sands should have sufficient enthalpy or heat to raise the temperature of the micellar dispersion to at least 100.degree.F. upon entering the tar sands, e.g. the dispersion should be heated to at least 100.degree.F. by the time the front portion of the dispersion is introduced about 7.5 - 15 feet into the tar sands. The water-external micellar dispersion contains hydrocarbon, surfactant, and aqueous medium and can have a pH of about 7-14, the higher pH aids in emulsification of the oil. The micellar dispersion can be preceded by a hot water flood, the water flood can be at a pH greater than 7. In addition, the micellar dispersion can be followed by a mobility buffer and this, in turn, followed by a drive material, e.g. drive water. The mobility buffer acts to impart a more stable flow to the process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The water-external micellar dispersion is comprised of hydrocarbon, surfactant, and aqueous medium. Optionally, alcohol and/or electrolyte can be incorporated. Examples of useful volume amounts include about 2 to about 50 percent hydrocarbon, about 40 to about 95 percent aqueous medium, at least about 4 percent surfactant, about 0.01 to about 20 percent cosurfactant, and about 0.001 to about 5 percent by weight of electrolyte. In addition, the dispersion can contain other additives such as corrosion inhibiting agents, bactericides, sequestering agents, etc.

Examples of useful hydrocarbons include crude oil, partially refined fractions thereof, e.g. side cuts from crude columns, crude column overheads, gas oils, kerosene, heavy naphthas, naphthas, straight-run gasoline, liquefied petroleum gases, etc.; and refined fractions thereof including propane, pentane, decane, dodecane, aryl compounds such as benzene, naphthalene, anthracene, and substituted products thereof. Also, the hydrocarbon can be a synthesized hydrocarbon. In addition, the unsulfonated hydrocarbon, e.g., heavy vacuum gas oils in petroleum sulfonates is also useful.

The aqueous medium can be soft, brackish, or a brine water. Preferably, the water is soft but it can contain small amounts of salts which are compatible with the ions within the tar sands.

The surfactant can be anionic, cationic, and nonionic. Examples of useful surfactants include those found in U.S. Pat. No. 3,254,714 to Gogarty et al. Especially useful surfactants are the petroleum sulfonates, also known as alkyl aryl naphthenic sulfonates. Preferred petroleum sulfonates include those having an average equivalent weight of about 350 to about 525 and more preferably about 390 to about 460. The sulfonate is preferably one containing a monovalent cation. Mixtures of different surfactants as well as mixtures of low, medium, and high average equivalent weight surfactants or sulfonates are useful.

The cosurfactant (also known as semi-polar organic compound and cosolubilizer) can have limited water solubility. Preferably, the water solubility of the cosurfactant is about 0.1 to about 20 percent or more and more preferably about 1 to about 5 percent at ambient temperature. Examples of useful cosurfactants include alcohols, amino compounds, esters, aldehydes, ketones and like compounds containing one to about 20 or more carbon atoms and more preferably about 3-16 carbon atoms. Specific examples of useful alcohols include isopropanol, n- and isobutanol, the amyl alcohols such as n-amyl alcohol, 1- and 2-hexanol, 1- and 2-octanol, decyl alcohols, alkaryl alcohols, and alcoholic liquors such as fusel oil. The alcohols can be primary, secondary, and tertiary alcohols. Preferably, the concentrations within the dispersions are about 0.01 to about 5 percent and more preferably about 0.1 to about 3 by volume. Mixtures of two or more different cosurfactants are useful.

The electrolyte useful in the water-external micellar dispersions include inorganic bases, inorganic acids, and inorganic salts; organic bases, organic acids, and organic salts, which are either weakly or strongly ionized. Preferably the electrolytes are inorganic bases, inorganic acids, and inorganic salts, e.g. sodium hydroxide, sodium chloride, sodium sulfate, hydrochloric acid, sulfuric acid, sodium nitrate, ammonium hydroxide, etc. Examples of other useful electrolytes are found in U.S. Pat. No. 3,330,343 to Tosch et al. Preferably, the electtolyte is one that will yield a high pH, e.g., sodium or ammonium hydroxide and like materials.

Examples of useful water-external micellar dispersions are taught in U.S. Pat. Nos. 3,506,071 and 3,506,070, to Jones.

Preferably, the pH of the micellar dispersion is above 7 and more preferably about 10-14. The desired pH can be obtained by adding the appropriate electrolyte to obtain the desired pH, e.g. NaOH, NH.sub.4 OH, etc.

The temperature of the micellar dispersion can be from below about ambient temperature up to about 100.degree.F., more preferably it is closer to 100.degree.F. Heating the micellar dispersion to above ambient temperature before injecting it into the injection means can be accomplished using conventional heating equipment. Also, the enthalpy or heat potential of the subterranean conditions can be used advantageously to heat the micellar dispersion as it progresses down the well bore before entering the tar sand.

The tar sand formation is heated before the dispersion is injected therein. The enthalpy or heat within the formation should be sufficiently high to cause the incoming micellar dispersion to become heated to at least 100.degree.F. as it enters the formation, e.g. the front portion should be at least 100.degree.F. by the time it travels about 7.5-15 feet into the formation. Temperatures up to the flash point of components within the micellar dispersion are useful within the formation. Methods of heating the formation are known in the art, e.g., steam flooding, in situ combustion, injecting heated fluids, etc.

The components of the micellar dispersion are designed to obtain a stable dispersion at the high temperature within the reservoir. For example, increasing the aromaticity of the hydrocarbon, increasing the electrolyte content, increasing the molecular weight of the surfactant and/or cosurfactant, etc. are methods useful to obtain dispersions stable at high temperatures. Specific methods of increasing the thermostability range to higher temperatures are taught in U.S. Pat. Nos. 3,493,048 to Jones, 3,493,047 to Davis et al, 3,495,660 to Davis et al, 3,500,912 to Davis et al, and 3,508,611 to Davis et al. The dispersion is made up on the surface so that it will be stable at formation temperatures, i.e., the surface mixture may not be thermodynamically stable at surface temperature, but at formation temperature, it will be a stable micellar dispersion.

The water-external micellar dispersion can be preceded by a water slug. The water slug is at a temperature greater than 100.degree.F. and more preferably above 150.degree.F. Also, the pH of the pre-water slug can be adjusted to about 7-14. High pHs aid in the emulsification of the oil. The high pH can be obtained by adding water-soluble bases, e.g. NaOH, etc. Volume amounts up to about 1 pore volume and greater are useful as a preslug.

The mobility, i.e., the effective mobility of the micellar dispersion flowing in the tar sands, can be adjusted, e.g., decreased, to give a more stable fluid flow to reduce or inhibit fingering. Such can be obtained by adjusting the components within the micellar dispersion to obtain a desired viscosity. However, it will generally be desired to design the mobility to be about equal to or greater than that of the formation fluids flowing in front of the dispersion.

The micellar dispersion can be followed by a drive material. Optionally, a mobility buffer can be injected behind the micellar dispersion and this, in turn, followed by the drive material. Examples of useful mobility buffers include aqueous and nonaqueous fluids containing mobility reducing agents such as high molecular weight, partially hydrolyzed polyacrylamides, polysaccharides, polyisobutylenes, etc. Generally, any mobility reducing agent is useful as long as it is compatible with the dispersion and the tar sands and does effectively reduce the mobility of the aqueous or nonaqueous mobility buffer slug flowing in the tar sands.

As mentioned previously, the micellar dispersion can be followed by a drive material. The drive material can be aqueous or nonaqueous and can be liquid, gas, or a combination of the two. Preferably it is an aqueous drive material. The drive material can contain ions but such ions are preferably compatible with the ions within the subterranean formation.

Formation pore volumes of about 1 to about 30 percent of more of the water-external micellar dispersion are useful with this invention. More preferably, about 1 to about 10 percent formation pore volume is useful. The mobility buffer can be in amounts of up to about 5 to about 75 percent or more formation pore volume.

It is not intended that the invention be limited by the specifics taught above. Rather, all equivalents obvious to those skilled in the art are intended to be included within the scope of the invention as defined within the specification and appended claims.

Claims

What is claimed is:

1. A process of recovering hydrocarbon from sub-surface tar sands having at least one injection means in fluid communication with at least one production means, comprising heating the tar sands to a temperature sufficient to heat an incoming water-external micellar to a temperature above about 100.degree.F. by the time the micellar dispersion travels about 7.5 to about 15 feet into the tar sands, injecting the water-external micellar dispersion into the tar sands, displacing the micellar dispersion toward the production means and recovering hydrocarbon through said production means.

2. The process of claim 1 wherein the water phase of the micellar dispersion has a pH within the range of about 7 to about 14.

3. The process of claim 1 wherein a slug of water at a temperature above 100.degree.F. precedes the injection of the micellar dispersion.

4. The process of claim 3 wherein the pH of the water is above about 7.

5. The process of claim 1 wherein the micellar dispersion is comprised of hydrocarbon, surfactant, and aqueous medium.

6. The process of claim 5 wherein the micellar dispersion contains cosurfactant, electrolyte or cosurfactant and electrolyte.

7. The process of claim 1 wherein the temperature of the micellar dispersion is above about ambient temperature and below about 100.degree.F.

8. The process of claim 1 wherein steam is injected to heat the tar sands before the micellar dispersion is injected.

9. The process of claim 1 wherein a mobility buffer is injected after the micellar dispersion.

10. The process of claim 1 wherein an aqueous drive material is used to displace the micellar dispersion toward the production means.

11. A process of recovering hydrocarbon from sub-surface tar sands having at least one injection means in fluid communication with at least one production means, comprising:

1. heating the tar sands to a temperature sufficient to heat an incoming water-external micellar dispersion to a temperature above about 100.degree.F by the time the front portion of the dispersion has traveled about 7.5 to about 15 feet in the tar sands,

2. injecting about 1 to about 30 percent formation pore volume of the water-external micellar dispersion into the tar sands,

3. thereafter, injecting about 5 to about 75 percent formation pore volume of a mobility buffer into the tar sands,

4. and then injecting sufficient drive material to displace the micellar dispersion and mobility buffer toward the production means and recovering hydrocarbon through the production means.

12. The process of claim 11 wherein the micellar dispersion is at a temperature above about ambient temperature and less than about 100.degree.F.

13. The process of claim 11 wherein up to about 100 percent formation pore volume of an aqueous preslug at a temperature above 100.degree.F. is injected into the tar sands before the micellar dispersion is injected.

14. The process of claim 13 wherein the pH of the aqueous preslug is about 7 to about 14.

15. The process of claim 11 wherein the micellar dispersion is comprised of hydrocarbon, surfactant, and aqueous medium.

16. The process of claim 15 wherein the micellar dispersion contains cosurfactant, electrolyte, or cosurfactant and electrolyte.

17. The process of claim 15 wherein the surfactant is petroleum sulfonate.

18. The process of claim 11 wherein the mobility buffer is an aqueous solution containing a mobility reducing agent.

19. The process of claim 11 wherein the drive material is aqueous.

20. The process of claim 11 wherein the pH of the water phase of the micellar dispersion is about 7 to about 14.

21. The process of claim 11 wherein steam is injected to heat the reservoir before the micellar dispersion is injected.

22. The process of claim 11 wherein the micellar dispersion contains about 2 to about 50 percent by volume hydrocarbon, about 40 to about 95 percent by volume aqueous medium, at least about 4 percent by volume surfactant, and about 0.01 to about 20 percent by volume cosurfactant and about 0.001 to about 5 percent by weight of electrolyte.

23. The process of claim 22 wherein the surfactant is petroleum sulfonate.