NO161808B - Means for use in the breakdown of oil emulsions - Google Patents

Description

The present invention relates to a new and improved micellar solution of a thin film dispersant comprising a polyether polyol and which is particularly useful for breaking or preventing the formation of petroleum emulsions. More particularly, the invention relates to a mixture in which water replaces all or a substantial part of the organic solvents which were previously necessary for the production of liquid solutions of this surface-active compound.

One of the main uses for the present mixture is the breakdown of petroleum emulsions, which enables the separation of these into two main phases. Much of the crude petroleum oil produced in the world is accompanied by some water or brine originating from or adjacent to the geological formations from which the oil is produced. The amount of aqueous phase accompanying the oil can vary from traces to a very large percentage of the total liquid flow. As a result of the natural presence of oil-soluble or dispersible emulsifiers in petroleum, much of the aqueous phase formed in the oil will be emulsified in it, forming stable water-in-oil emulsions.

The literature contains numerous references to such emulsions, the problems caused by them, as well as methods used to break down the emulsions and separate a salable petroleum. See, for example, "The Technology of Resolving Petroleum Emulsions" by L.T. Monson and R.W. Stenzel, pp. 535 etc. in Colloid Chemistry Vol VI, Ed. by Jerome Alexander, Rheinhold Publishing Corp., New York (1946) and "Interfacial Films Affecting the Stability of Petroleum Emulsions" by Chas. M. Blair, Jr. in Chemistry and Industry (London), pp. 538 etc. (1960).

Previously known demulsifiers used to break petroleum emulsions were water-soluble soaps, "Twitchell reagents" and sulfonated glycerides. These products could be easily mixed with water to provide easily pumpable fluids which were conveniently used by pumping into the flow lines at the wellhead or washed down the well casing with water to mix with the well fluids prior to their upflow to the surface. However, these products are only effective in relatively high concentrations and their use contributes significantly to production costs.

Some time ago it was found that certain lightly sulfonated oils, acetylated castor oils and various polyesters, all of which are insoluble in water but soluble in alcohols and aromatic hydrocarbons, were more effective in breaking emulsions. Consequently, essentially the commercial development of demulsifiers has led to the production of agents which are insoluble in both water and petroleum oils and which have other properties which will be described below which cause them to spread at oil-water interfaces to give very thin, moving films that replace any emulsifier present in the oil and enable coalescence of dispersed water droplets. In general, such surface-active agents will hereinafter be referred to as "thin film spreading agents" or "TFSA".

Previously, these compounds had to be composed with and dissolved

in alcohols or highly aromatic hydrocarbon solvents to give readily usable liquid mixtures. A wide spectrum of such mixtures is necessary to treat the many different emulsions that can be encountered around the world.

Although the current TFSA mixtures are very effective and

are possibly up to 50-100 times more effective per volume unit than the original water-soluble demulsifiers, so

they are subject to certain practical disadvantages due to their solubility properties. For example, alcohols and aromatic hydrocarbons which are necessary for the production of a liquid, pumpable mixture are quite expensive and whose price is close to that of the active demulsifier itself. Furthermore, such solvents are flammable and thus create safety problems and cause greater costs for transport, storage and use. The low flash point can

is improved by the use of high-boiling aromatic solvents, but these are increasingly rare, expensive, and not harmless due to their carcinogenic and dermatological effects.

Furthermore, the existing demulsifiers generally cannot be used in an underground oil or gas well, injection well or the like as they cannot be washed down with either water (or brine) or part of the produced oil, and as they are viscous liquids which only are required in very small quantities, they cannot be safely continuously emitted several thousand meters underground at the liquid level in a typical well without the use of complicated and expensive equipment.

Other applications of TFSA compositions would be facilitated if they were readily soluble or dispersible in water. For example, large quantities of heavy, viscous oil are produced in the USA. using steam injection methods. Typically, wet-steam is injected into the oil-producing strata for several weeks to heat the oil, lower its viscosity and increase the energy of the reservoir. The steam injection is then stopped and the oil flows or is pumped out from the borehole that was used for the steam injection. Much of the water that forms as a result of condensation of the steam is also carried with the oil in emulsified form. Since emulsions are more viscous than the external phase at the same temperature, the flow resistance will increase and the productivity of "steamed" wells can be improved by injecting a water-soluble demulsifying agent1 into the steam during the steam injection period to prevent emulsion formation, as stated in US patent No. 3,396,792.

The requirement for water solubility will significantly limit the choice of demulsifiers for use by steam or water injection to relatively ineffective mixtures.

As shown in the Norwegian patent applications No. 80.1661, 80.1662, 80.1663 and 80.1664, TFSA are useful when used in the extraction of petroleum. Used in such processes involving the displacement of residual oil by means of aqueous solutions, polymer solutions or other aqueous systems, these compounds will act to increase the amount of recovered oil. Such an effect is possibly due to their ability to promote further water wetting of the reservoir rock, lower the viscosity of the oil-water interface layer and promote coalescence of dispersed droplets of either water or oil in the second phase.

By using the present aqueous micellar solutions, the introduction of TFSA into aqueous displacement or flow fluids can be facilitated to a significant extent. In addition, present micellar solutions as such or in combination with other components will only be used as a flocculating agent or as a pre-treatment agent that is introduced before other aqueous fluids.

Other uses for the present TFSA micellar solutions include their use as flocculation aids for finely ground hematite and magnetite ores during the de-sliming step or ore processing, as additives to improve oil removal and to promote detergency in cleaning compositions and in detergents for use on polar materials, to improve solvent extraction processes such as those used in the extraction of antibiotics where an aqueous fermentation liquid is extracted with organic solvents, to improve efficiency and phase separation in the purification and concentration of metals by solvent extraction with organic solutions of metal complexing agents, as well as to improve wetting and dyeing of natural and synthetic fibers and for other processes that normally involve interfaces between surfaces of different polarity or wetting properties.

An aim of the present invention is to provide aqueous, liquid mixtures of these TFSA<1>s with new and useful properties which enable the production of: petroleum emulsion breakers and emulsion preventing mixtures which are free or relatively free of highly flammable and environmentally harmful aromatic hydrocarbons, mixtures which are relatively cheap, mixtures that are soluble or dispersible in water and which can therefore often be used using more efficient methods than are possible for existing products, mixtures that can be used in enhanced recovery operations such as steam flooding and flooding with an aqueous medium in which the currently existing products cannot be easily used, as well as mixtures that can be mixed with water-soluble agents of other types, such as corrosion inhibitors, wetting agents, scaling inhibitors, biocides, acid,

etc. to provide multipurpose compounds for use in solving many oil well completion, production, transportation and refining problems.

According to the present invention, these purposes are achieved by means of amphipathic agents which are capable of forming micelle solutions and which, by this mechanism or other not well-defined effect, combined with those for the other essential component which will be referred to as a hydrotropic agent, are in able to form homogeneous aqueous solutions containing TFSA in a relatively wide concentration range.

The TFSA mixtures according to the present invention can be briefly described using the following general properties: 1. Solubility in water and isooctane at approx. 25° C is less than approx. 1 percent by volume; 2. Solubility parameter at 25° C lies in the range from approx. 6.8 to approx. 8.5 with the main component in the range between 7 and 7.9, and 3. Spreads at the interface between a clear refined mineral oil and distilled water to give a film of a calculated thickness not exceeding approx. 20 Angstroms

at a spreading pressure of approx. 16 dyne/cm.

TFSA mixtures with these properties are generally organic polymers or semi-polymers with molecular weights from approx. 2,000 to approx. 100,000 and have a structure containing a number of distributed hydrophilic and hydrophobic groups arranged in linear or planar rows, which makes them surface-active and causes them to be absorbed at oil-water interfaces under

formation of very thin films.

In contrast to most known surface-active compounds, the present TFSA does not seem to be able to form a micelle in either oil or water. The distributed and alternating presence of polar and non-polar or hydrophilic or hydrophobic groups in the molecule apparently prevents the degree of organization necessary for micelle formation and thus reduces dispersion or dissolution either in water or low polar organic solvents.

TFSAs useful in the present invention have the previously stated properties: 1. Solubility in water and in isooctane at approx. 25° C is less than approx. 1 percent by volume.

Solubility determinations can be carried out by introducing 1 ml of sample (or weight of the solid product calculated to have a volume of 1 ml) into a measuring cylinder of the type that can be closed with a towed glass stopper<p.> Then 99 ml of water is introduced into the cylinder and this is introduced into a water bath at 25° C until temperature equilibrium is reached, after which the measuring cylinder is taken from the bath and shaken vigorously for 1 min. The cylinder is then returned to the bath for 5 min. after which the shaking procedure is repeated, finally the cylinder is returned to the bath and allowed to stand quietly for 1 h. The contents of the cylinder are then carefully examined for any milky consistency or opacity of the liquid phase or the presence of any sediment or undissolved material in the cylinder, which indicates that the sample satisfies the requirements for insolubility in water.

Insolubility in isooctane is similarly determined by using this hydrocarbon rather than water. 2. Solubility parameter (S.P.) at approx. 25° C is in the range 6.9 - 8.5.

Methods for determining the solubility parameter are shown in Joel H. Hildebrand, "The Solubility of Nonelectrolytes", third edition, page 4 25 etc. However, a simplified method can be used which is sufficiently accurate for the identification of a useful TFSA mixture. Components with a given solubility parameter are generally insoluble in hydrocarbon (non-hydrogen-binding) solvents that have a lower solubility parameter than the actual TFSA mixture. Therefore, the present mixture will be insoluble in a hydrocarbon solvent with a solubility parameter of approx. 6.8. As the solubility parameter for mixtures of solvents is an additive function of the volume percentage of the components in the mixture, sample solutions with the desired solubility parameter can be easily prepared by, for example, mixing benzene (S.P. 9.15) and isooctane (S.P. 6.85) or perfluoro- n-heptane (S.P. 5.7).

A mixture of approx. 7 2 divides benzene by approx. 28 parts of isooctane will provide a solvent with a solubility parameter of approx. 8.5 at room temperature (approx. 25° C). Perfluoro-n-heptane has a solubility parameter of approx. 5.7 at approx. 25° C so that a mixture of 68 parts of this solvent with 32 parts of benzene gives a solvent with a solubility parameter of approx. 6.8 or isooctane with a solubility parameter of 6.85 can be used.

When 5 ml of TFSA is mixed at room temperature with 95 ml of a solvent with a solubility parameter of 8.5 a clear solution should be obtained. When 5 ml of TFSA is mixed with a solvent with a solubility parameter of 6.85, a cloudy mixture or a mixture showing phase separation should be obtained. Solvent mixtures with a solubility parameter between 7.0 and 7.9 can be prepared as described above using

of a corresponding test procedure.

When interpreting the solubility parameter and other determinations, it should be noted that TFSA does not consist of a single material or a single compound but a cogeneric mixture of products containing a number of products whose molecular weights are distributed around the average molecular weight and which also contain smaller amounts of the starting compounds which was used in the production. As a result, when determining solubility and solubility parameters, a faint presence of milkiness or a lack of absolute clarity should not be interpreted as "standing" or "crossed" with regard to satisfying the aforementioned criteria. The purpose of the test is to determine whether the main proportion of the cogeneric mixture, i.e. 75% or more, meets the requirements. When the result is doubtful, the solubility tests should be carried out in centrifuge tubes to enable a subsequent rapid phase separation by centrifugation, after which the separated non-solvent phase can be removed and any solvent contained therein can be evaporated and the relevant weight or volume of the separated phase

can be determined.

3. TFSA should spread at the interface between distilled water and refined mineral oil to give films with a thickness not exceeding approx. 20 Angstroms (200 nm) at a film pressure of approx. 16 dynes/cm (0.016 Newton/m).

Suitable methods for determining film pressure are shown in N.K. Adam "Physics and Chemistry of Surfaces", Third Edition, Oxford University Press, London, 1941, page 20 etc. and CM. Blair, Jr., "Interfacial Films Affecting The Stability of Petroleum Emulsions", Chemistry and Industry (London), 1960, page 538 etc. The film thickness is calculated on the assumption that all TFSA remains in the interfacial area between oil and water on which the product or a solution thereof in a volatile solvent is applied. As the spreading pressure is numerically equal to the change in the interfacial tension as a result of the film's spreading, interfacial tension measurements can be conveniently performed before and after the addition of a known amount of TFSA to an interface with a known area.

Alternatively, one can use a boundary film scale of the Langmuir type, such as that described by J.H. Brooks and B.A. Pethica, Transactions of the Faraday Society (1964), page 20 etc. or other methods suitable for the determination of the interfacial spreading pressure.

When determining the interfacial spreading pressure for TFSA products, it is preferred to use a relatively easily available and reproducible oil, such as a clear refined mineral oil, as the oil phase. Such oils are derived from petroleum and are treated with sulfuric acid and other agents to remove non-hydrocarbon and aromatic constituents. Typical of such oils is "Nujol" (Plough, Inc.).

This oil has a density in the range 0.85 - 0.89 and usually a solubility parameter in the range 6.9 - 7.5. A number of similar oils of greater or lesser density and viscosity are usually available from chemical suppliers and pharmacies.

Other essentially aliphatic or naphthenic hydrocarbons with low volatility are equally suitable and will give similar values for the dispersion pressure. Suitable hydrocarbon oils are commercially available as "white oils", "textile lubricants", "paraffin oil" and the like. These can often contain very small amounts of alpha-tocopherol (vitamin E) or similar oil-soluble antioxidants, but these will not affect the scattering measurements.

Although the existence of micelles, as well as oil or aqueous micelle solutions, has been known for some time, (see for example "Surface Activity", Moilliet, Collie and Black, D. Van Nostrand & Co., New York (1961)) and probably forms part of many operations involving detergents in which either oily

(non-polar) or soil particles (very polar) are to be removed, then their use in collaboration with hydrotropic agents for the present purpose is an unexpected and unforeseeable discovery.

In US patent no. 2,356,205, a number of different micellar solutions are indicated designed to dissolve petroleum oils, bitumen, waxes and other relatively non-polar compounds with the intention of clearing oil formations in order to achieve an improved recovery of petroleum by dissolving it. At this early date, however, application of the micelle principles was not contemplated for the preparation of solutions of relatively high molecular weight demulsifiers.

However, some of the principles set forth in said patent, apart from the main purpose therein of dissolving relatively large amounts of hydrocarbons, chlorinated hydrocarbons and the like, are applicable to the preparation of the present compositions.

The necessary four ingredients for the micelle solutions of TFSA are: 1. A micelle-forming amphipathic agent. Such an agent may be anionic, cationic or nonionic and if anionic or cationic. it can either be present in salt form or as the free acid or free base or mixtures thereof. 2. Hydrotropic agent. This is a polar compound of low to medium molecular weight containing oxygen, nitrogen or sulfur and capable of forming hydrogen bonds. It is believed that such agents cooperate in some way with the amphipathic agent to give a clear or opalescent, stable mixture.

3. Water

4. TFSA with the above characteristics.

In addition to these components, the micelle solutions may possibly contain salts, hydrocarbons or smaller amounts of other inorganic or organic material. Such components can be impurities, solvents, or by-products from the production of the hydrotropic agent, or they can be additives that have been found useful in the production of the mixtures according to the invention. As an example of the latter, small amounts of inorganic salts such as NaCl, Na 2 SO 4 , KN0 3 , CaCl 2 and the like may at times be useful in promoting homogeneity with a minimal amount of amphipathic and hydrotropic agents. They can also provide mixtures with a reduced freezing point, a property that is useful when the mixture is to be used in cold climates. In the same way, ethylene glycol, methanol, ethanol, acetic acid and similar organic compounds can be incorporated into the mixtures to improve physical properties such as freezing point, viscosity and density or to improve stability.

As stated above, the micelle-forming amphipathic agents used in the preparation of the present aqueous solutions can either be cationically active, anionically active or of the non-electrolytic type. Amphipathic agents generally have at least one group containing 10 or more carbon atoms and no more than approx. 64 carbon atoms per molecule. This is the case for the amphipathic agents used according to the invention as a component of the carrier or the solvent or dispersant used in the present mixtures. The hydrophobic parts of these agents can be aliphatic, alicyclic, alkylalicyclic, aromatic, arylalkyl or alkylaromatic. The preferred type of agents are those where the molecule contains a long unbroken carbon chain containing 10-22 carbon atoms in length. Examples of suitable anion-active amphipathic agents include the usual soaps as well as materials such as sodium cetyl sulfate, ammonium lauryl sulfate, ammonium diisopropyl naphthalene sulfonate, sodium oleyl glyceryl sulfate, brown and green sulfonates from petroleum or petroleum fractions or extracts, sodium stearamidoethyl sulfonate, dodecylbenzene sulfonate, dioctyl sodium sulfosuccinate, sodium naphthenate and the like. Other suitable sulfonates are those shown in US Patent No. 2,278. 171.

Suitable cationic active compounds include cetylpyridine chloride, stearamidoethylpyridine chloride, trimethylheptadecylammonium chloride, dimethylpentadecylsulfonbromide, octadecylamine acetate and 2-heptadecyl-3-diethyleneamino imidazole diacetate.

Suitable non-electrolytic amphipathic agents include oleic esters of nonaethylene glycol, the stearic ester of polyglycerol, oxyethylated alkylphenols, and long chain alcohol ethers of polyethylene glycols.

It is of course well known that amphipathic compounds are readily and commercially available or they can be readily prepared to exhibit the properties of one or more of the above-mentioned types. Such compounds are shown in US Patent No. 2,262,743. In cases where a surface-active material can exhibit the properties of one or more of the above-mentioned types, it will be understood that it can be classified under either each or both of the types.

The solvent or the hydrotropic agents in the solution used according to the present invention can be described as compounds of a hydrophobic hydrocarbon residue with a relatively low molecular weight combined with a hydrophilic group with a low molecular weight and which is free of surface-active properties. The hydrophobic residue may contain 2-12 carbon atoms and may be an alkyl group, alicyclic, aromatic or alkyl-substituted alicyclic or aromatic, or may be the hydrocarbon portion of a heterocyclic or hydrocarbon-substituted heterocyclic group. The hydrocarbon residue can be branched or unbranched, but no branch can have a length of more than approx. 7 carbon atoms from the attachment point for the hydrophilic residue, benzene or a cyclohexyl group being considered to have an equivalent length to an aliphatic chain of 3 carbon atoms.

When the hydrocarbon residue consists of no more than 4 carbon atoms then the structure for a normal, primary alkyl group is preferred. When the residue consists of more than 4 carbon atoms, structures of the secondary or tertiary type can also be good if the second and third branches are methyl or ethyl groups.

The hydrophobic hydrocarbon residue is combined either directly or indirectly with a hydrophilic group of one of the following types: (a) A hydroxyl group which may be alcoholic, phenolic or carboxylic; (b) An aldehyde group; (c) A carboxyamide group; (d) An amine salt group;

(e) An amine group; and

(f) An alkali phenolate group.

By "indirectly combined with one of these groups" is meant that the hydrocarbon residue is associated by etherification, esterification, amide formation or the like with other organic residues that do not contain more than four carbon atoms and also one or more of the above-mentioned hydrophilic groups, provided that after each combination, at least one of the hydrophilic groups remains free.

Special examples showing this class of compounds are: Ethyl alcohol, n-amyl alcohol, alphaterpineol, p-cresol, cyclohexanol, n-butyraldehyde, benzaldehyde, n-butyric acid, glycol monobutyrate, propyl lactate, mono-n-butylamine hydrochloride, n-propionamide , ethylene glycol mono-n-butylamine hydrochloride, n-propionamide, ethylene glycol mono-n-butyl ether, pyridine, methylated pyridine, piperidine or methylated piperidines.

The cosolvent (hydrotropic compounds described above) is essentially a semipolar liquid in the sense that any liquid whose polar properties are not greater than that of ethyl alcohol and which exhibits at least a tendency to and dissolve in water or dissolve water is designated as

semipolar.

The co-solvent or the semi-polar liquid as indicated above can be described by the formula X - Z, in which X is a group with 2-13 carbon atoms and which can be an alkyl, phenyl, phenylalkyl, cycloalkyl or cycloalkenylalkyl group. It is a limitation that the longest carbon chain must be less than 8 carbon atoms and with such a characterization cyclic carbon atoms must be counted as half.

Z means

-COOH; or -OCH3 where U and V are hydrogen or a hydrocarbon group means if X is a cyclic tertiary amino group, is

if X is a cyclic secondary amino group…

The semipolar liquid can also be indicated by the following formula:

R x -NH-(CH 2 ) n -NH-(CH 2 ) -NH-R 2

where n=1-5 and R^ is H > alkyl or imidazolinyl.

In general, all of these hydrotropic agents are liquids with a dielectric value of 6-26, and have at least one polar group containing one or more oxygen atoms and/or nitrogen atoms.

It is possibly significant that all these co-solvents are of types known to form hydrogen bonds.

The value of solubilizer or co-solvent and its proportion in the mixture is to some extent dependent on the amphipathic agent used, the amount and type of TFSA used and the proportion of water used and is best determined by preparing test mixtures on a small scale.

In certain cases, it may be desirable to incorporate small amounts of acid, alkali or inorganic salts into the solution and it has been found that the presence of these electrolytes often gives solutions with greater stability and a wider range of miscibility with water and organic materials. The excess of acid, if used, will usually be

in solutions containing a cationically active or non-electrolytic wetting agent. When an excess of alkali is used, this will usually be in a solution containing an anion-active wetting agent.

The polyether polyol or TFSA used according to the invention is generally an organic polymer or semi-polymer with an average molecular weight above approx. 800 and under approx. 30,000 and has a structure that will enable an orientation on polar surfaces with most or all of the molecule's elements in a thin plane. In order to be effectively adsorbed at oil-water or oil-rock interfaces and subsequently desorbed at water-rock interfaces, the TFSA must generally contain constituents that give it widely distributed hydrophilic and hydrophobic properties and without such a concentration of either hydrophilic or hydrophobic groups as to provide water solubility or oil solubility -ness in the usual macroscopic sense. TFSA seems too

to differ from previously used surfactants in that the effects on the oil-water interfacial tensions as a function of concentration are limited.

During spreading on such interfaces to give thin films with a spreading pressure of up to 35-40 dyne/cm, further larger amounts of TFSA will have relatively little effect on the interface tension. TFSA constitutes a component of the micellar solution in contrast to previously used surfactants and has little or no tendency to stabilize either oil-in-water or water-in-oil emulsions when present in normally used amounts.

Generally, the TFSA components that are usable in the practice of the present invention are made up of organic molecules containing carbon, hydrogen and oxygen, although in certain cases they may also contain sulphur, nitrogen, silicon, chlorine, phosphorus and other elements. Small amounts of inorganic materials such as alkalis, acids or salts may be present in the mixture as neutralizing agents, catalyst residues or otherwise. The critical requirements for the TFSA mixture are not so much the composition as such but more of a structural or physical nature. They must consist of hydrophilic (polar) groups, usually one capable of forming hydrogen bonds, such as hydroxyl, carbonyl, ester, ether, sulfone, amino, ammonium, phosphorus, or similar hydrogen-bonding groups associated with or to hydrophobic groups such as alkylene-, alkyl-, cycloalkyl-, aryl-, arylene-, aralkyl-, polyalkylene-, polyalkylene-, combinations of such groups and such groups containing relatively non-polar substituents such as hydrocarbon, chlorine, fluorine and the like . Sometimes the hydrophobic groups are larger and contain more atoms than the polar groups in the molecule and have at least two carbon atoms in each group and up to as many as 36 carbon atoms, although the actual ratio between the sizes is largely dependent on the structure of the hydrophilic unit. Typically, the hydrophobic groups will contain 14-22 carbon atoms and will have linear or sheet-like conformations that allow a relatively flat orientation on surfaces.

Polar units other than the hydrogen bond positions are not excluded from these mixtures and may in fact be intentionally included in certain structures to improve adsorption and the tendency for interfacial diffusion. For example, quaternary ammonium groups, which are unable to form hydrogen bonds, can improve dispersion and limit adsorption in certain applications due to their highly ionized form, which imparts cationic character to molecules in which they are present and via coulombic repulsion effects improve dispersion in a film.

In general, the TFSA components will contain at least two of each of the required hydrophilic (polar) and hydrophobic units per molecule and usually they will contain many more of each of these. However, the effective products must exhibit the three characteristics described above.

As indicated above, an effective TFSA may be derived from a wide number of different chemical reactants and may contain many different groups or units, however, it has been found that the mixing parameters should satisfy the requirements set forth in the characterizing part of claim 1.

Mixtures that fall within the scope of the above outer formula contain on average 1.5 or more hydroxyl groups per molecule and generally consists of cogeneric mixtures of products obtained by condensing alkylene oxides with smaller molecules containing two or more reactive hydrogen atoms as parts of hydroxyl or amino groups.

Representative of these mixtures is polypropylene glycol with an average molecular weight of approx. 1,200, to which is added approx. 20% by weight ethylene oxide. Such a polyether glycol can theoretically be obtained by condensing approx. 20 mol of propylene oxide with 1 mol of water followed by the addition of approx. 6 moles of ethylene oxide. Alternatively, 20 mol of propylene oxide can be condensed with a previously prepared polyethylene glycol with an average molecular weight of approx. 24 0.

Alkylene oxides which are suitable for use in the preparation of the TFSA components used in the present solutions include ethylene oxide, propylene oxide, butylene oxide, 2-3-epoxy-2-methylbutane, trimethylene oxide, tetrahydrofuran, glycidol and corresponding oxides containing less than approx. 10 carbon atoms. Due to their reactivity and relatively low cost, the preferred alkylene oxides for making effective TFSA components are 1,2 alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide. When producing different TFSA components, more than one alkylene oxide can be used either in the form of mixtures of oxides or in sequence to form block additions of the individual alkylene oxide groups.

Other suitable dihydric alcohols can be obtained by condensing alkylene oxides or mixtures of oxides in successive steps (blocks) with the functional (in relation to oxide addition) compounds such as ethylene glycol, methylamine, propylene glycol, hexamethylene glycol, ethyl ethanolamine, analin, resorcinol, hydroquinone and such.

Trihydric ether alcohols can be produced by condensation of ethylene, propylene or butylene oxides with, for example, glycerol, ammonia, triethanolamine, diethanolamine, ethylethylenediamine and correspondingly smaller molecules containing three hydrogen atoms which are capable of reacting with the alkylene oxides. Similarly, polyether alcohols with several hydroxyl groups can be obtained by condensation of alkylene oxides with multireactive starting compounds such as pentaerythritol, glycerol, N-mono-butylethylenediamine, trishydroxymethylaminomethane, ethylenediamine, diethylenetriamine, diglycerol, hexamethylenediamine, decylamine or cyclohexylamine. US patent no. 2,679,511 describes a number of polyols derived from amino compounds which are then esterified. "Product 15-200" manufactured and sold by the Dow Chemical Company is produced by oxyalkylation of glycerol with a mixture of ethylene and propylene oxides and is an example of a commercially available polyol of the type contemplated for use in carrying out the present invention.

In general, these compounds will have an average molecular weight of 15,000 or less and are derived from compounds containing reactive hydrocarbon atoms and having 18 or fewer carbon atoms and 10 or fewer reactive hydrogen atoms.

Other general descriptions of suitable compounds falling within the scope of the above-described structure, as well as procedures for carrying out the various preparation steps are shown in "High Polymers, Vol. XIII, Polyethers," edited by N.G. Gaylord, John Wiley & Sons, New York, 1963.

With regard to the limits for the various components in the micellar solutions containing TFSA, the following can serve as a guide, the indications are in % by weight:

Although the exact function of the electrolytes previously discussed is not fully understood, the effect can in any case be partially attributed to their ability to bind water, i.e. get hydrated. This indicates that certain other materials of a very hydrophilic nature and which clearly differ from the class of non-polar solvents and semi-polar co-solvents can be functional equivalents of an electrolyte. Components in this class that do not usually dissociate include glycerol, ethylene glycol, diglycerol, sugar, glucose, sorbitol, mannitol and the like.

As indicated above, these solutions may contain other organic constituents such as hydrocarbons. These are often used as diluents, azeotropic distillation aids or for control of reflux temperatures in the production of the TFSA component and may be back in this when the present micellar solutions are produced. To the extent that such compounds are present, they seem to compete to a certain extent with the TFSA component for micelle space and thus to a certain extent limit the maximum amount of TFSA component that can be brought into a homogeneous solution.

Selection of an effective TFSA mixture for a given petroleum emulsion and determination of the amount that is necessary is carried out by so-called "bottle tests" which are typically carried out in the following way: A fresh emulsion is obtained and 100 ml portions are poured into each of several 180 ml screw cap precipitators - or equivalent graded bottles. Dilute solutions (1% to 2%) of various TFSA ingredients are prepared in isopropyl alcohol. Using a measuring pipette, add a small volume of a TFSA solution to the bottle. A corresponding volume of each of the mixtures is added to the other bottles containing the emulsion. The bottles are then closed and transferred to a water bath and kept at the same temperature as that used at the treatment plant in question. When this temperature is reached, shake the bottles vigorously for several minutes. After shaking, the bottles are placed upright in the water bath and allowed to stand still. At appropriate intervals, the volume of separated water layer is observed together with the sharpness of the oil-water interface, the appearance of the oil and the clarity of the water phase.

After the grace period, which can vary from 30 min. to several hours, depending on the temperature, the viscosity of the emulsion, and the amount of TFSA mixture used, small samples of the oil are removed using a pipette or injection syringe and after the sample they are centrifuged to determine the amount of free and emulsified water back into the oil.

The pipette or syringe used to remove the samples should be inserted via a cap or other device that acts as a position control to ensure that all bottles are sampled at the same liquid level.

The combined information regarding residual water and emulsion, water separation rate and appearance of the interface forms the basis for choosing the generally most effective TFSA component. If none of the results are satisfactory, the experiments should be carried out using higher concentrations of the TFSA components and, in the opposite case, if all the results are good and equal, the experiments should be carried out at lower concentrations until good differentiation is possible.

When dissolving petroleum emulsions of the water-in-oil type with the present micellar solution, the solution is brought into contact with the emulsion to be treated using one of the various methods or devices that are now generally used to break petroleum emulsions with a chemical agent , as the method indicated above is used alone or in combination with other demulsification procedures,

such as the electrical dehydration process.

One method is to accumulate a volume of emulsified oil

in a tank and perform a batch demulsification treatment to recover clean oil. In such a method, the emulsion is mixed with the micellar TFSA solution, for example by stirring the emulsion in the tank and slowly dripping the micellar TFSA solution into the emulsion. In certain cases, the mixture can be achieved by heating the emulsion while the micellar TFSA solution is added dropwise, as the convection currents in the emulsion can provide a satisfactory mixture. A third modification of this type of treatment is to extract the emulsion from the bottom of the tank with the help of a circulation pump and reintroduce it to the top of the tank, while the micellar TFSA solution is supplied, for example, at the suction side of the circulation pump.

In the second type of treatment, the micellar TFSA solution is introduced into the well fluids at the wellhead or at a location between the wellhead and the final oil storage tank, using an adjustable metering mechanism or a metering pump. Normally, the liquid flow through the subsequent pipelines and connections will be sufficient to provide the desired mixture of the micellar TFSA solution and emulsion, although in certain cases additional agitation may be introduced into the flow system. In this general method, the system can include various mechanical devices for discharging free water, separating entrained water or treating the chemically treated emulsion in stationary precipitation tanks. Heating devices can be used in connection with the treatment methods described above.

The third way of using the micellar TFSA solution when treating an emulsion is to introduce the micellar solution either intermittently or continuously in diluted form into the well and let it follow the well fluids to the surface and then let the chemical-containing emulsion flow through a any suitable surface equipment as used in other treatment methods. This particular method of application is useful when the micellar solution is used in connection with the acidification of cold oil-containing strata, especially if it is dissolved in the acid used in the acidification.

In all cases, it will appear from the given description

that the method generally comprises introducing only a relatively small proportion of a micellar TFSA solution into a relatively large proportion of the emulsion, mixing the added chemical and the emulsion either by natural flow or by means of special devices, with or without the application of heat and then letting the mixture is allowed to stand until the content of unwanted water in the emulsion is separated and settled.

In addition to their use to break petroleum emulsions, the present micellar TFSA solutions, as previously mentioned, can be used to prevent emulsion formation by steam flotation, by secondary water flotation, by acidification of oil-producing formations and the like.

Petroleum oils can also contain significant amounts of inorganic salts after demulsification, either in solid form or as small residual brine droplets. For this reason, most petroleum oils will be desalted before refining. The desalination step is carried out by adding and mixing the oil with a few percent by volume of fresh water to bring this into contact with the brine and the salt. In the absence of a demulsifier, such added water will also be emulsified without providing the desired washing effect. Existing micellar solutions can be added to the fresh water to prevent it from emulsifying and thus facilitate phase separation and removal of salt during the desalination process. If desired, the solution can be added to the oil phase in the same way as the currently used aromatic solvent mixtures. Most petroleum oils together with accompanying brines and gases have a corrosive effect on steel and other metal structures with which they come into contact. Well pipes, well casings, flow pipelines, separators and storage tanks are often severely attacked by well fluids, especially when acidic gases such as J^S and CO2 are present in the fluids, but also in systems that are free of these gases.

It is previously known, for example as indicated in US patent no. 2,466,517, that such corrosive attacks of crude oil liquid can be avoided or prevented by adding small amounts of organic inhibitors to the liquids. Effective inhibitor mixtures for such an application are usually semi-polar surfactant compounds containing a non-polar hydrocarbon unit linked to one or more polar groups containing nitrogen, oxygen or sulfur or combinations of these elements. In general, these inhibitors or salts thereof will be soluble in oil and/or water (brine) and will often apparently be able to form micelles in one or both of these phases. Typical inhibitors include amines such as octylamine, dodecylamine, dioctodecylamine, butylnaphthylamine, dicyclohexylamine, benzyldimethyldodecylammonium chloride, hexadecylaminopropylamine, decyloxypropylamine, mixed amines prepared by hydrogenation of nitrile derivatives of tall oil fatty acids, soy acid esters of monoethanolamine, 2-undecyl-1-aminoethylimidazoline and a wide number of cationic nitrogen-containing compounds of a semipolar character.

Active in certain applications are nonylsuccinic acid, diocylnaphthalene sulfonic acid, trimeric and dimeric fatty acids, propargyl alcohol, mercaptobenzothiozole, 2, 4, 6-trimethyl-1, 3, 5-trithiaan, hexadecyldimethylbenzimidazole bromide, 2-thiobutyl-N-tetrodecylpyridine chloride, tetrahydronaphthylthiomorpholine, etc.

Unlike TFSA, corrosion inhibitors seem to work

in that they form strongly adherent, thick, densely packed films on the metal surface that prevent or reduce the contact between the corrosive fluids and gases with the metal and affect the ion and electron transfer reactions that are part of the corrosion process.

Corrosion inhibitors are often brought down into the well space in oil wells where they are mixed with the well fluids before being fed up through the well pipe and can thus effectively prevent corrosion of the well equipment. When corrosive attack occurs at the surface, the inhibitor can be introduced near or at the wellhead and allowed to adsorb into the pipelines and surface equipment

to ensure protection.

Addition of inhibitor either down in the hole or at surface locations can be suitably combined with the addition of the demulsifier as the latter is also often added at one of these locations.

Inhibitors such as those mentioned above can generally be incorporated into TFSA micellar solutions and replace part of or in addition to the TFSA component. Furthermore, since many of these inhibitors are in themselves micelle-forming amphipathic agents, they can be included in the micellar solution as such and replace other amphipathic agents that could otherwise be used. Combining the micellar solution with a corrosion inhibitor enables a more economical chemical treatment and reduces the inventory of one compound and requires only one chemical injection system instead of two and thus facilitates the work and necessary monitoring.

A further important effect achieved by the application of

the micellar dissolution of TFSA and the corrosion inhibitor is attributed to the prevention of emulsification of the inhibitor. It is often found that the inhibitor in an amount necessary to achieve effective protection causes the formation of very stable emulsions of water and hydrocarbon, especially in systems containing light, normally non-emulsifying hydrocarbons such as

distillates such as petrol, kerosene, diesel oil and various other fractions. Inhibitors are commonly used in refining systems where emulsification is highly undesirable and where the mixtures could be reformulated to include an effective emulsion-preventing micellar solution of TFSA.

Inhibitors can be used in an amount from a few to several hundred parts per million, calculated on the oil to be treated and depending on the extent of corrosion. For a given oil field or groups of wells, tests will normally be carried out to determine the requirement for the micellar dissolution of TFSA and for the inhibitor and a mixture will be prepared containing these components in approximately the desired conditions. In certain cases, the requirements for a micellar solution of TFSA in the best concentration will lead to the use of a corrosion inhibitor, used as a micelle former, in excess of what is necessary for inhibition. This will not affect the applicability of the micellar solution and will result in an inhibition "surplus" which may be useful during periods when high corrosivity can be expected. Examples of micellar solutions in which TFSA is used with inhibitors in water-dispersible micellar solutions will appear from the following.

Selection of the appropriate corrosion inhibitor for a given system or oil can be based on laboratory testing under conditions similar to those in the well or pipelines. Such tests are exemplified by that described in Item No. 1K155, "Proposed Standardized Laboratory Procedure for Screening Corrosion Inhibitors for Oil and Gas Wells", published by the National Association of Corrosion Engineers, Houston, Texas.

EXAMPLE 1

4.7 parts of dipropylene glycol and 0.25 parts of potassium hydroxide are introduced into an autoclave provided with means for mechanical stirring, heating and cooling. The contents of the autoclave were heated to 125° C. and at this temperature 1,2-propylene oxide was slowly introduced from a transfer bomb containing 200 parts of 1,2-propylene oxide. Cooling was used during the addition to keep the temperature below 130° C at a pressure in the range 4 - 5.3 kp/cm " 2. About 2 h was necessary for the introduction of 1,2-propylene oxide. The reaction mass was kept at 13 0 ° C for 4 h to ensure that the amount of unreacted 1,2-propylene oxide was at a minimum. Five parts of ethylene oxide were then added from a transfer bomb at such a rate that the temperature was maintained at 150 - 160 ° C at 4 - 5.25 kp/

2

cm. After all the ethylene oxide had been added, the temperature was held at 150°C for a further 1 hour to complete the reaction. The molecular weight of the finished product was approx. 4,000.

This product is insoluble in water and diisobutylene, has a solubility parameter of 7.2 and spreads on the distilled water-mineral oil interface to give a spreading pressure of 21 dyne/cm at a calculated thickness of 10 Angstroms.

EXAMPLE 2

In an apparatus similar to that in example 1, 9.2 parts of glycerol were reacted with 275 parts of a mixture of 225 parts of propylene oxide and 50 parts of ethylene oxide using the same method as that used in example 2 in the applicant's Norwegian patent application no. 80.1663, which method is hereby also covered by the present invention. The final product was a clear, almost colorless viscous oil with a molecular weight of

a. 3,000. This product was not 1% soluble in water or diisobutylene. It had a solubility parameter of 7.5 and spreads on the distilled water-mineral oil interface to give a pressure of 20 dynes/cm with a calculated film thickness of 12 Angstroms.

EXAMPLE 3

By using the apparatus and method according to Example I

1,815 kg of polypropylene glycol with an average molecular weight of 1,200 was condensed with 318 kg of ethylene oxide. 18 kg of potassium hydroxide was dissolved in the polypropylene glycol before the oxide addition, which was carried out at a temperature in the range of 140 -

160° C at a maximum pressure of approx. 5 kp/cm.

On cooling to room temperature, it was found that the retained product was found to be approx. 1% soluble in water and isooctane, has a solubility parameter of 8.0 and spreads at the interface between "white" oil and distilled water at 25°C to give a film exerting a spreading pressure of 16 dyne/cm with a calculated film thickness at 20 Angstroms.

EXAMPLE 4

To a vessel having a volume of 760 1 equipped as per Example 1^ was introduced 80 kg of diethylenetriamine and the temperature was slowly raised to 110°C and propylene oxide was slowly introduced at a rate sufficient to raise the temperature as a result of the exothermic reaction to approx. 140° C. Cooling was then used to maintain this temperature until 318 kg of propylene oxide had been added. At this point, the contents of the vessel were cooled to 70°C and pumped into a stainless vessel with a volume of 7,570 1, similar to that according to Example 1. 4 kg of potassium hydroxide flakes were stirred into the contents of the vessel. Pure nitrogen was blown through the liquid to remove water and the temperature was raised to 110°C, after which the vessel was closed and the nitrogen supply stopped and propylene oxide was again pumped into the reaction mass at a rate sufficient to bring the temperature to 140-160°C This addition was continued until the oxide addition dropped to approx. 1 kg/min. The vessel was quickly opened and an additional 11 kg of potassium hydroxide flakes were introduced followed by 30 min. nitrogen purge.

Propylene oxide was again pumped into the reaction mass until the total propylene oxide addition reached 3,630 kg. At this point the propylene oxide addition was stopped and ethylene oxide was introduced at a rate sufficient to maintain the temperature at 140-150° C until a total of 410 kg had been added.

The cooling system was activated to lower the temperature to approx. 4 0° C after which the product was pumped to storage. This product satisfied the previously mentioned criteria for a suitable TFSA.

EXAMPLE 5

90 kg of triethanolamine was used instead of diethylenetriamine in Example 4. The method of preparation was followed except that 4 kg of potassium hydroxide flakes were stirred into the triethanolamine before the addition of propylene oxide.

The final product satisfied the requirements for TFSA.

EXAMPLES OF MICELLULAR SOLUTIONS OF TFSA

EXAMPLE A

In addition to having a good demulsifying effect, the product was found to be an effective corrosion inhibitor for use down a borehole. Imidazoline, which was used as an amphipathic agent, is a strongly adsorbing inhibitor for steel in anaerobic systems.

EXAMPLE B

This product also exhibits significant corrosion inhibitory action in aerated systems and is also a useful demulsifier. This product was investigated to determine its effectiveness in promoting the recovery of oil by waterflooding.

Among test methods that have been found useful in selecting the appropriate TFSA is one that involves determining the oil displacement efficiency from treated oil-bearing rock cores in the equipment described below. A tube of glass or transparent polymethacrylate with an inner diameter of approx. 3.5 cm and a length of approx. 45 cm and provided with supply connections and suitable valves at each end. The tube is mounted vertically in a stand in an air bath equipped with a fan, heating elements and a thermostat that allows the selection and maintenance of temperatures in the range 25 - 13 0° C.

In order to select the most effective TFSA for use in a given oil formation, samples of oil, the oil-producing rock formation and the water to be used in the flooding operation are obtained. The rock formation is extracted with toluene to remove oil, dried and then ground in a ball mill to a point where a greater percentage passes a 40 mesh sieve. The fraction between 60 mesh and 100 mesh is retained. The above-described tubes are removed from the air bath, opened and, after introducing a glass wool filter at the lower end, the tube is packed with the painted stone formation. The pipe is gently tapped from time to time during filling to ensure a tight packing and visually inspected to ensure the absence of voids.

The pipe is then returned to the air bath, connected to the supply pipe and the temperature is adjusted to the temperature of the oil formation and oil from such formation is slowly supplied through the bottom supply pipeline from a calibrated reservoir in an amount just sufficient to fill the packed rock plug in the pipe. This volume is determined from the calibrated reservoir and is referred to as "Pore volume" and is the volume of oil that is just sufficient to fill the pores or cavities in the packed rock plug.

The upper pipeline to the reservoir is then connected to a calibrated reservoir containing the oil representing that from the formation to be flowed. By appropriate manipulation of valves, the pipeline can be filled with oil which is then slowly pumped into the core from the reservoir after which the lower valve is opened to allow displacement of the formation water.

A breakthrough of oil at the bottom is noted and pumping is stopped and the volume of oil introduced into sand is determined from readings from the reservoirs. This is referred to as the volume of oil present. The pipe with the sand containing oil is then placed in the air bath at a temperature corresponding to that of the formation for a period of 3 days to allow equilibrium between the ground formation rock and the oil with regard to adsorption of the oil constituents on the rock and lowering of the interfacial tension. The time for reaching equilibrium can vary within wide limits. At higher temperatures, the time required to achieve equilibrium is probably less. Usually, for comparative tests, 3 days are used to age the oil-stone plug. Results of this procedure approximately simulate working with current cores of oil-bearing rock.

Oil and the water samples used for testing purposes are preferably taken under an inert gas such as pure nitrogen and are kept free from contact with air during all manipulation with the aim of preventing oxidation of the oil and thus the introduction of foreign polar, surface-active components into the oil. At this point, rock-oil systems simulate the original oil formation before primary oil production has begun and the well before any secondary waterflow operation.

The other inlet pipe is now connected to the water sample to be used when flooding the oil formation and with the help of an injection syringe or other positive displacement pump with a small displacement <p>the water is pumped into the sand body from the top to displace liquid out at the bottom of the pipe which is connected to a calibrated receiver. The pump speed is adjusted so as to simulate the speed of the flood water during a current operation, which is usually in the range of 1-50 cm/day. Pumping is maintained at this rate until two pore volumes of water have been pumped through the sand.

The volumes of the liquids collected in the receiver are measured and the relative amount of oil and water displaced from the rock sample is determined and recorded. Of particular interest is the volume of oil displaced in relation to the original pore volume. This information can be regarded as an indication of the percentage of oil that was originally present and that has been produced by natural expulsion with water after drilling a well in a rock formation followed by the primary production phase carried out to the approximate economic limit.

After this step, an additional one to three" pore volumes of water containing the TFSA micellar solution to be examined are slowly pumped through the plug and the additional volumes of oil and water displaced are determined. Typically when such an initial "slug" of micellar TFSA solution is introduced it can be contained in a liquid volume in the range 1-100% of the pore volume, but most commonly this volume will be 10-50% of the pore volume.

After this final displacement step, produced oil and water are again determined. By comparing the amount of oil produced as a result of the further injection of water containing, or after a prior injection of a solution of micellar TFSA solution with an amount produced when the same volume of water is injected without TFSA solution present, then one can calculate the efficiency of the special micellar TFSA solution used to improve the recovery of additional oil compared to that achieved by ordinary waterflooding.

In general, 6 or more sand columns of the described type will be installed in the heated air bath. Examination of a given micellar TFSA solution is carried out "in triplo" using identical conditions and concentrations simultaneously with three blank samples without addition of the micellar TFSA solution to the water.

The mixture according to Example B was examined by this method under the following conditions.

The oil was displaced by pumping two pore volumes of water into the sand. After measuring the volumes of oil and water produced via the bottom pipeline, a further 0.2 pore volumes of water containing 3,500 ppm of the mixture according to Example B were injected followed by 2.8 pore volumes of water containing 200 ppm of the mixture according to Example B. Measurement of the volumes of oil and formed water was read after every 0.2 pore volume of injected water.

The result of this test for the injection of 2,3 and 5 pore volumes of water, respectively, is given in the following table, in which average figures for 3 determinations are reproduced.

Recovered oil in % of

oil present

Use of the mixture according to example B in the above

for given quantities led to a production of 130% more oil from injection of an additional drilling volume of water than that provided by water injection alone and produced 180% more oil after injection of an additional 3 pore volumes of treated water.

EXAMPLE C

This was a clear, homogeneous, viscous solution which was found to be an effective demulsifier for emulsion formed in the Swan Hills, Alberta field and was particularly useful in causing a clear water phase to separate from the oil phase in the processing plant.

EXAMPLE D

In addition to exhibiting a strong demulsifying effect on emulsions of East Texas crude oil, the product was also an effective bactericide as a result of the quaternary ammonium salt and the cresylic acids that are sufficiently soluble in the water phase that separates from the emulsion and will thus prevent bacterial growth in the water and thus ensure that it is easily injectable for removal or for enhanced recovery.

In this mixture, the dodecyldimethylbenzoylammonium chloride functions both as a cell-forming amphipathic agent and as a biocide. The ability of this product to break down a petroleum solution was demonstrated in the following experiment.

100 ml of an emulsion from the Taching field, People's Republic of China, was introduced into each of two 150 mis measuring bottles fitted with screw caps. The emulsion contained 42% water as determined by azeotropic distillation with xylene. The bottles were placed in a water bath and kept at a temperature of 55° C. After 30 min. in the bath, a bottle (no. 1) was opened and 0.8 ml of a 1% isopropanol solution of the mixture according to example D was introduced into the bottle by means of a calibrated 1 mm pipette. 0.8 mm of pure isopropanol was introduced into the second bottle (no. 2) using a corresponding pipette. Both bottles were carefully closed, shaken in a mechanical shaker for 5 min. with 134 oscillations per my. (extension 10 cm) and then returned to the water bath.

After 1 h of quiet rest at 54° C, the bottles were examined.

In bottle no. 1, a clear phase separation was visible with a sharp interface at approx. The 40 ml graduation. Bottle No. 2 did not exhibit any free water or other phase separation. The bottles were allowed to stand for a further 1 h after which they were opened and 6 ml samples were pipetted out from each bottle at the 60 ml level and mixed with 6 ml portions of xylene in 12 ml API calibrated centrifuge tubes. The tubes were shaken for a few seconds to ensure mixing of oil and xylene and then centrifuged for 5 min. at 1,800 rpm. The sample from bottle no. 1 contained 0.2% free water and 0.1% sedimented emulsion. The sample from bottle no. 2 contained 52% sedimented emulsion layer and no free water.

EXAMPLE E

This product was found to be an effective demulsifier for emulsions produced in the Salem, Illinois field and was further found to provide a clear separated water phase, free of oil and other suspended solids, which could be re-injected to maintain pressure with minimal contamination of the filter. and the production formations.

This product was highly viscous and can be used as such or mixed with a corresponding amount of water as a propellant for secondary or tertiary oil recovery where mobility control, as well as improved water wetting and oil removal are important.

Claims (2)

1. Micellar thin film dispersant mixture, characterized in that it comprises: (1) 5-75 wt% of a polyether polyol of the formula: wherein A is an alkyl an oxide group of the formula -C-jHgiO-, i is a positive integer not greater than 10, j is a positive integer not greater than 100, k is a positive integer not greater than 100, r! is hydrogen, a monovalent alkyl group contained containing up to 11 carbon atoms or (AlH), L is a positive integer not greater than 100, R is a hydrocarbon residue of a polyol, a primary or secondary amine, a primary or secondary polyamine, a primary or secondary amino alcohol or hydrogen, m + n is not greater than 4 when R is different from hydrogen and one of m or n is zero and the other 1 when R is hydrogen, which polyether polyol at 25°C: (a) is less than 1 volume soluble in water and in isooctane, (b) has a solubility parameter in the range 6.9-8.5, and (c) spreads at the interface between distilled water and refined mineral oil to give a film of a thickness not greater than 20 Angstroms at a film pressure of 16 dyne/cm, (2) 2-30 wt# of a hydrotropic agent having one of the formulas wherein X is an alkyl -, optionally with alkyl substituted phenyl/phenylalkyl, cycloalkyl or cycloalkenylalkyl group with from 2 to 13 carbon atoms, and in which Z is: -OH; -COOH; or -OCH 3 ; where U and V are hydrogen or hydrocarbon substituents, wherein n = 1-5, R^ is hydrogen, alkyl or imidazolinyl, (3) 2-30 wt# of an amphipathic agent of formula where R 2 is alkyl of more than 10 carbon atoms, R3 is SO3X, where X is an alkali metal or optionally with alkyl or cycloalkyl substituted ammonium, or R3 is -O-((CH2)n~O)m_SO3x» where m and n are 1-10 and X as indicated above, and J (4) 15-90 wt# water. 2. Mixture according to claim 1, characterized in that the polyether polyol is derived from a reaction product of an alkylene oxide containing less than 10 carbon atoms with polyols, amines, polyamines and amino alcohols containing 2-10 active hydrogen groups which can react with the alkylene oxides and containing 2-30 wt# of a hydrotropic agent comprising a semipolar hydrogen bond-forming compound containing at least one oxygen atom, nitrogen atom or sulfur atom and 2-12 carbon atoms, (3) 2-30 weight^ of an amphipathic agent containing at least one group with 10-64 carbon atoms per molecule, (4) 15-90 wt# of water.