US 2882973 A
Description (OCR text may contain errors)
l /e 12 XR o A. et. All 3's known petroleum deposits of any type.
aecovnav on on. FROM TAR SANDS Todd M. Doscher and Joseph Relsherg, Houston, Tex., assignors to Shell D evelopment Company, New York, N.Y., a corporation of Delaware N Drawing. Application June 17, 1957 Serial No. 666,237
12 Claims. (Ci. 166--42) This invention relates to a method for the separation and recovery of oil from bituminous or tar sands, such as Alberta tar sands, and more particularly pertains to an economical and commercially feasible method of in situ separation and recovery of high yields of oil from tar sands, such as the Alberta tar sancls in which the oil has a density higher than that of water.
In various localities throughout the world, deposits of tar sands or bituminous sands are found; usually the oil or tarry material in these bituminous sands has a density approaching or even greater than 1.0. The most extensive and best known deposits of this type occur in the Athabasca district, Alberta Province, Canada. These Athabasca tar sands extend for many miles and occur in thicknesses varying up to more than 200 feet. These tar sands constitute one of the probably largest presently The oil content of these sands is usually within the range of lO%-20% by weight, although sands with smaller and larger amounts of oil are not unusual; the sands generally also contain small proportions of water which is usually in the range of l%-5% by weight. The water is present in the form of films surrounding the individual sand grains and insulating them from the oi; and tar which fills the interstices of the mass. The oil or tar from these Athabasca tar sands generally has a specific gravity varying within the range of from 1.00 to 1.04. The Athabasca tar sands also have sand particles which are not well rounded. In fact, these sand particles (which are of granitic origin) have a cuspidal form or shape.
The oil obtained from the bituminous sands, e.g. the above-described Athabasca tar sands, is a viscous tarry material which, in its crude state, does not command a high price. Therefore, any method suitable for recovering this oil must involve a minimum expense to be attractive for commercial practice.
Various methods have been proposed heretofore for the extraction and recovery of the oil from bituminous sands, such as the aforementioned Athabasca tar sands. However, for one reason or another, none of these has had any substantial degree of commercial success. In all of these methods the operating costs have been so high that these processes have not been economical for large commercial scale operations. One of the main reasons why the heretofore proposed methods are uneconomical is that all of them involve the mining and therefore handling of the tar sands for the purpose of recovering therefrom the oily or tarry material. Also, some of these processes involved heating of the tar sands or the use of organic solvents. Thus, in one known process, the tar sand, after removal from the round, is jetted with stentr ...d mulled th :1 small proportion of water at about ht)" mass, and in the maintaining of the circulating water at the desired elevated temperature.
Another process involves milling a mined tar sand with kerosene and water, and then allowing it to settle. A mixture of oil and kerosene floats to the top of the settling zone, and is removed. The process thus requires use of an oil solvent (i.e. kerosene) which will have to be distilled from the extracted oil for reuse. This process is likewise expensive, requiring large capital investments and added operating expenses for heat.
It is an object of the present invention to obviate the above and other defects of the prior art and to provide a process whereby oil in high yields can be recovered from bituminous sands, such as Athabasca tar sands, in situ, i.e. without the necessity of mining these sands, or otherwise handling large masses thereof in order to extract the oil or tarry material therefrom. It is another object of this invention to provide an economical process for extracting and recovering high yields of oil from tar sands without the necessity of heating the sand, or the use of an oil solvent, or both, the application of at least one of these procedures having been heretofore thought to be necessary in order to secure satisfactory extraction of the oil phase from the sand mass.
The above and other objects are attained, according to the process of the present invention, by subje ctjpgthe bituminous sands to the action of an aqueo h s so l u t ign ii-L 2 is ssrtessas ufiiijuuduseue tion has a pllwaw More specifically stated, tlTein'Vention comprises contacting the bituminous or tar sands in situ with an aqueous solution having a pH of at least 12 and containing an effective amount of a non-ionic surfactant. It has been found that if the pH of the aqueous liquid is at least 12, the amount of oil or tarry material which may be recovered from a given tar sand is materially greater than when an equiv alent amount of aqueous liquid having a pH material below 12, even though containing the same non-ionic detergent, is used. It has been still further found that the extraction or recovery of oil from tar sands (other conditions being equal) is further materially improved by the incorporation into the aforementioned highly basic aqueous solutions containing the non-ionic surfactant, of minor amounts of neutral salts which are chemically nonreactive with the non-ionic surfactants or detergents. Although there is no in ention to be limited by any theory of the case, it is presently believed that the use of nonionic surfactants in a water solution having a pH of at least 12 effects an extraction of most if not all of the oil or tarry material from a tar sand by reason of the ready and spontaneous emulsitication which occurs when this aqueous liquid comes in contact in situ with the tar in the sands. In this connection it must be noted that crude petroleum oil, as distinguished from oil from bituminous (tar) sands, will not be spontaneously emulsified when brought in contact with the aforesaid aqueous liquid having a pH of 12 or above and containing a nonionic surfactant, but requires agitation for emulsification.
A wide variety of non-ionic surfactant compounds may be used in the process of the present invention. The following are exemplary classes or groups of compounds which are effective non-ionic surfactants:
(I) Oil-soluble monohydric alcohols, cg. the octanols, nonanols, decanols, undccanols, dodecanols and the higher aliphatic alcohols. These may be synthetic alcohols, cg. alcohols produced by the so-cnlled Oxo process, or they may be of natural origin, eg. fatty alcohols from sperm oil. Also oil-soluhle aromatic and cyclonliphutie alcohols such as bcnzyl alcohol and methylcyclohexanol may be used.
(ll) Oil-soluble dihydric alcohols such as the hexyleue sunsrl IUTE roa nissme COPY aesaa /s glyc'ol's, octyle3 glycols, decylene glycols and the higher the mono-esters or ethers of polyethylene glycols such as the mono-oleate or stearate of noun-ethylene glycol. The commercially available mixtures of compounds of the aforesaid types may be used.
A particularly desirable non-ionic surfactant for use in the process of the present invention (in conjunction with water containing a basic compound to raise the pH to at least 12) is a glycol or polyglycol ether of the type obtainable by causing an aromatic or hydroaromatic hydroxyl compound substituted in the nucleus by at least one hydrocarbon radical or equivalent thereof, containing at least four carbon atoms, to react with an alpha, beta-alkylene oxide, such as ethylene oxide, propylene oxide, butylene oxide, or the like. Either or both reactants may first be block homopolymerizcd before reacting with each other.
The following are illustrative examples of non-ionic surfactants of the last-mentioned group: Reaction product obtained by condensing iscroctyl phenol with ethylene oxide in a mol ratio of 1:10 (this product is commercially sold by Rohm and Haas as Triton X-lOO); nonyl phenyl which has been oxyethylated with about 30 mols of ethylene per mol of phenol (this is sold commercially by General Aniline and Film Company under the name Antarox A403") an alkyl phenol having an alkyl side chain of 8 or 9 carbon atoms, which has been oxyethylated with about 10 mols of ethylene oxide per mol of phenol (Hercules Powder Companys Synthetic B The non-ionic surfactant should be present in the treating or extracting liquid in sufiicient concentration to effect the instantaneous or spontaneous emulsification of the oil or tarry material present in the tar sands and to maintain it in emulsified state during passing through the formation and subsequent mechanical handling. Concentrations of from about 0.1% by weight to about by weight are usually suilicient for this purpose, although smaller or larger quantities may be desired or even necessary in some cases. Excessive concentrations are in most instances to be avoided as wasteful, or as inimical to proper emulsification, or as yielding an. emulsion too stable to be amenable to its ultimate resolution.
It was pointed out above that the surfactant-containing aqueous liquid must have a pH of at least 12. This is generally effected by the incorporation of a base to either fresh or saline water. In the case of distilled water, a very small amount of a base, e.g. alkali metal hydroxide or ammonia, is required to produce such solution, this amount being less than 0.04% by weight. However, in the case of water available in the field, considerably larger concentrations of base are usually required to insure the overcoming of the buffering action of compounds in solution in such waters. As stated, the treating solutions (into which the aforementioned non-ionic surfactants are incorporatcd) preferably comprise fresh or saline waters containing ammonia or an alkali metal hydroxide, preferably sodium hydroxide, to yield a solution having a pH of at least about 12; normally, this is attained by the incorporation of sodium hydroxide in amounts equal to about 0.5% by weight.
The spontaneous emulsiiication, and therefore the re- 'coverable yield of oily matter from the tar sands, is enhanced by the presence, in the aqueous non-ionic-surfactant-containing alkaline solution, of a water-soluble A. Generally, water-soluble alkali metal halides, sulfates, carbonates, phosphates, and the like are suitable for use for this purpose, the amount thereof in the solution ranging from substantially negligible amounts to as high as about 5% by weight, although still larger amounts may be sometimes desirable or even necessary.
The temperature of the treating solution may vary within wide limits. As stated, no special heating thereof is necessary. 'Ihus, excellent results can be obtained by using these aqueous alkaline solutions at temperatures in the range of from about 15 C. to about 40 C. However it must be noted that sometimes higher temperatures may be advantageous because a rise in temperature generally enhances the activity of the surfactant and thus increases the speed of emulsification.
The process of the present invention comprises or includes three actual operating steps: (a) an aqueous alkaline treating solution (of a pH of at least 12) containing a non-ionic surfactant and, optionally a water-soluble neutral inert inorganic salt, is injected into a tar sand; (b) the emulsion formed in situ and containing the oil or tarry material, is brought to the surface, e.g. bypumping; and (c) the emulsion is separated to yield the oil and to recover the treating solution for reuse.
In operating on undisturbed tar sand formations in situ, the aforementioned aqueous alkaline surfactant-containing solution may be forced through the formation to effect a recovery of the tarry material from the sands. By sinking a central pressuring or input well in the formation, and around it sinking several other collectng or production wells, the aqueous solution may be forced down the central well and by means of applied pressure cause it to migrate to the neighboring collecting wells. In the passage of the aqueous solution through the tar sands, the oily or tarry material is stripped free from the sand and emulsified in the form of small discrete particles surrounded by the aqueous solution; in other words, the emulsion formed is of the oil-in-water type.
In operation according to the process generally described in the preceding paragraph, the introduction of the treating solution into the formation may be interrupted when this solution has penetrated as far as the production well or wells, this for a period of time sufficient to assure complete emulsification and, thus, recovery of the tarry material from the sand.
Another way of effecting the recovery of oil from tar sand formations, particularly when they are unconsolidated, is to employ a process analogous to the Frasch process for mining sulfur. In this process a single well is used, this well being provided with an outer casing set in the well and open to the formation, and an inner tubing concentrically disposed within the casing and preferably having a nozzle or nozzles at or near its (the tubings) lower end. The aforementioned aqueous alkaline solution is then jetted against the oil-containing tar sand formation through the nozzles; this produces the emulsion, which, together with the entrained sand, is pumped, or otherwise raised to the surface through the annular space between the casing and the tubing. If the specific gravity is too high and the pumping of the emulsion is too difficult, other means, e.g. gas lift, may be employed to elevate the oil-containing emulsion to the surface.
In some cases, particularly where the aqueous solution will permeate the tar sand formation only with difiiculty, it may be preferred to use a surging or pulsating motion of the aqueous alkaline solution to effect the contact thereof with and cmulsiflcation of the oily material at the outer bounds of the zone penetrated by the aqueous solution, and subsequently provides for the removal of this relatively concentrated emulsion, cg. like in the aforementioned modilied Frasch process, and the replacement thereof by a fresh or less concentrated solution. In this case, if a single well is used, the injections and withdrawal are intermittent and alternate.
In demonstrating the present invention, series of up ansaeva paratus were set up to simulate conditions in a tar sand formation. Each apparatus consisted of a glass tubing 4 inches in length and 1 inch in diameter, the tops and bottoms of these tubings being closed by perforated metal discs and screens. Each unit was filled with Althabasca tar sand, which was maintained in cold storage since its removal from the source, this sand being tamped into the glass cylinders. The oil content of this tar sand, as determined by extraction with benzene in a soxhlet extract, was equal to 15.75% by weight (based on the sand).
The various units prepared as described above were then treated by saturating the sands therein with various aqueous solutions mentioned below, and left undisturbed except for the periodic removal of 25 cc. samples of the solute from each and the immediate replacement thereof with fresh solutions of equal volume. In all, in each case 300 cc. of the given aqueous solution were thus passed through the sand in each vessel, this over a period of 35 days. This was then followed by a wash with a 5% aqueous sodium chloride solution to remove remaining surfactant from the pack. The effectiveness of each solution to remove the oily material was then determined by extracting the residual tars remaining in the sands with benzene in a soxhlet extractor. The results of these runs are presented in the following table:
The Triton X-lOO is the Rohm and Haas surfacant produced by reacting isooctyl phenol with ethylene oxide in a molar ratio of 1:10.
It will be seen that the use of an aqueous solution containing only sodium hydroxide did not extract any oil; in fact, the 2% NaOH solution showed no signs of even discoloration. Likewise an aqueous solution containing Triton X-lOO (together with some neutral salt) failed to extract any oil, while the use of the same solution with some sodium hydroxide permitted a substantial oil recovery which was enhanced by the presence of some sodium chloride. It must also be noted that the use of an anionic surfactant (sodium lauryl sulfate) failed to result in any substantial oil displacement even though the solution also was highly basic due to the presence of sodium hydroxide.
In another series of tests, using the same size glass tube units and the same Althabasca tar sand, the following aqueous solutions were -in total amounts of 100 cc., the passage being in 2 5 cc. increments each of which was allowed to remain in contact with the sand for two days. The results of these tests are presented in the following The Igepal CO-850 is a full equivalent of the Autarox A-403 discussed above. It must be noted that the use of bornx together with a non-ionic surfactant failed to effect any economical removal of oil from the tar sands; this is believed to be due to the fact that borax forms a Q; buffered solution having a pH of only 9.2 even though borax is added in amounts up to saturation. On the othe hand effective extraction is and was obtained by using an aqueous alkaline solution having a pH of above 12 (by use of sodium hydroxide).
The foregoing exemplary description of this invention is not to be considered as limiting since many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.
We claim as our invention:
1. The process of recovering oil from oil-containing tar sands which comprises contacting tar sands in the formation with an aqueous solution having a pH of at least 12 and containing a non-ionic surfactant, thereby extracting the oil from the tar sands by spontaneous emulsification thereof in the aqueous solution, recovering the emulsion thus formed from the formation, and separating the oil from said emulsion.
2. The process of recovering oil from oil-containing tar sands which comprises contacting tar sands in situ in the formation with an aqueous solution having a pH of at least 12 and containing at least 0.1% by weight of a nonionic surfactant, thereby extracting the oil from the tar sands by spontaneous emulsification thereof in the aqueous solution, recovering the emulsion thus formed from the formation, and separating the oil from said emulsion.
3. The process of recovering oil from oil-containing tar sands which comprises contacting tar sands in situ in the formation with an aqueous solution having a pH of at least 12 and containing between about 0.1% and about 5%, by weight, of a non-ionic surfactant, thereby extracting the oil from the tar sands by spontaneous emulsification thereof in the aqueous solution, recovering the emulsion thus formed from the formation, and separating the oil from said emulsion.
4. The process according to claim 3, where the nonionic surfactant is a reaction product obtained by condensing an alkyl phenol with an alkylene oxide in an amount of between about 10 and about 30 mols of the alkylene oxide per mole of the alkyl phenol.
5. The process of recovering oil from oil-containing tar sands which comprises contacting a tar sand in situ in the formation with an aqueous solution containing between about 0.l% and about 5%, by weight, of a nonionic surfactant and of a water-soluble alkali metal hydroxide in an amount sufficient to bring the pH of the aqueous solution to at least 12, to effect an extraction of the oil from the tar sands and the spontaneous emulsification of said oil in the aqueous solution, thereby producing an oil-in-watcr emulsion, recovering said emulsion from the formation, and separating the oil from said emulsion.
6. The process according to claim 5, wherein the watersoluble alkali metal hydroxide is sodium hydroxide.
7. The process according to claim 2 wherein the aqueous solution also contains a water-soluble neutral salt which is chemically non-reactive with the non-ionic surfactant.
8. The process of recovering oil from oil-containin tar sands which comprises contacting a tar sand in situ in the formation with an aqeuous solution containing an alkali metal hydroxide in an amount sutficient to raise the pH of the solution to at least 12, a non-ionic surfactant in an amount equal to between about 0.1% and about 5% by weight, and a water-s oluble neutral salt chemically nonreactive with the non-ionic surfactant, said salt being used in an amount of up to about 5%, by weight, of the aqueous solution, to effect an extraction of the oil from the tar sands and the spontaneous emulsilication of said oil in the aqueous solution, thereby producing an oil-in-water emulsion, recovering said emulsion from the formation, and separating the oil from said emulsion.
9. The process of recovering oil from oil-containing tar sands which comprises introducing into the tar sand formation an aqueous alkaline solution having a pH of at least 12 and containing at least 0.1%. by weight, of a nonionic surfactant, maintaining said aqueous solution in contact with the tar sands in the formation for a period of time sufficient to eliect an extraction of the oil from the tar sands and the spontaneous emulsiiication of said oil in I containing between about 0.1% and-about 5% of a nonionic surfactant up to about 5% of a neutral inorganic salt non-reactive with the surfactant, and an alkali metal hydroxide to bring the pH of the aqueous solution to at least 12, forcing said solution through the tar sand formation thereby extracting oil therefrom and causing said oil to be emulsified in the aqueous alkaline solution, recovering said emulsion through a recovery well at a distance from the injection well, and separating the oil from the emulsion.
ll. The process of recovering oil from oil-containing assaera tar sands which comprises introducing into the tar sand formation an aqueous solution containing an alkali metal hydroxide in an amount sufiicicnt to raise the pH of the solution to at least 12, and containing a non-ionic surfactant in an amount equal to between about 0.1% and about 5% by weight, maintaining said aqueous solution in contact with the oil-containing tar sands in the formation for a period of time suilicient to effect an extraction of the oil from the tar sands and the spontaneous emulsification of said oil in the aqueous solution, thereby producing an oil-in-water emulsion, recovering said emulsion from the formation, and separating the oil from said emulsion.
12. The process according to claim 11 wherein the alkali metal hydroxide is sodium hydroxide.
References Cited in the file of this patent UNITED STATES PATENTS 2,412,765 Buddrus et al Dec. 17, 1946 2,748,080 Newcombe et al May 29, 1956 2,817,635 Goldman et a1. Dec. 24, 1957