MXPA02010422A

MXPA02010422A - Solids stabilized water in oil emulsion and method for using same.

Info

Publication number: MXPA02010422A
Application number: MXPA02010422A
Authority: MX
Inventors: Dennis G Peiffer
Original assignee: Exxonmobil Upstream Res Co
Priority date: 2000-04-25
Filing date: 2001-04-05
Publication date: 2003-04-25
Also published as: NO20025108L; WO2001081718A1; GB0223087D0; DE10196124T1; OA12250A; GB2379468A; AU2001249902A1; EA200201136A1; BR0110283A; NO20025108D0; EA006271B1; GB2379468A8; EG22691A; GC0000222A; GB2379468B; CA2405493C; CA2405493A1; AR029247A1; CN1426507A

Abstract

A method for enhancing the stability of a solids stabilized water in oil emulsion by pretreating the oil prior to emulsification. The pretreatment step can be accomplished by adding dilute acid to the oil, adding a lignosulfonate additive to the oil, sulfonating the oil, thermally oxidizing the oil, thermally treating the oil in an inert environment, and combinations thereof. The emulsion can be used in enhanced oil recovery methods, including using the emulsion as a drive fluid to displace hydrocarbons in a subterranean formation, and using the emulsion as a barrier fluid for diverting flow of fluids in the formation.

Description

EMULSION OF WATER IN OIL STABILIZED WITH SOLIDS AND METHOD FOR USING THE SAME FIELD OF THE INVENTION The present invention relates to a water emulsion in. oil stabilized with solids, used for the recovery of improved crude oil. More specifically, the stability of the water-in-oil emulsion stabilized with solids is improved by the oil pre-treatment method prior to emulsification. The pretreatment step can be carried out by adding dilute acid to the oil, by adding a lignosulfonate additive to the oil, by sulfonating the oil, by thermally treating the oil in an inert environment, by thermally oxidizing the oil and combinations thereof. The improved emulsion can be used either as a drive fluid to displace hydrocarbons from an underground formation or as a barrier fluid to divert the flow of hydrocarbons in the formation. BACKGROUND OF THE INVENTION It is well known that a significant percentage of oil remains in an underground formation after the costs of primary production rise to such an extent that the recovery of additional oil is inefficient in cost. Typically, only one-fifth to one-third of the original oil at the site is recovered during production primary. At this point, a number of improved oil recovery (EOR) procedures can be used to additionally recover the oil in a cost effective manner. These procedures are based on repressurization or maintenance of oil pressure and / or mobility. For example, flooding with water from a deposit is a typical method used in the industry to increase the amount of oil recovered from an underground formation. Flooding with water involves simply injecting water into a reservoir, typically through an injection well. The water is used to move the oil in the tank to a production well. However, when flooding with water is applied to displace heavy viscous oil from a formation, the process is inefficient because the mobility of the oil is much less than the mobility , of the water. The water is quickly channeled through the formation to the production well, avoiding most of the oil and leaving it without recovering. For example, in Saskatchewan, Canada, primary production crude has been reported to be only about 2 to 8% of the original oil in place, with flooding with water that produces only another 2 to 5% of that oil in the place. Consequently, there is a need to elaborate either the most viscous water, or use another driving fluid that Do not be channeled through the oil. Due to the large volumes required of the drive fluid, it must be cheap and stable under the flow conditions of the formation. The displacement of the oil is more efficient when the mobility of the driving fluid is significantly lower than the mobility of the oil, so that the greatest need is for a method of generating a low mobility drive fluid in an effective manner in cost. . Oil recovery can also be affected by extreme variations in the permeability of the rock, such as when the high permeability "stealing or skimming zones" between the injection wells and the production wells allow most of the fluid to flow. Injected discharge is quickly channeled to the production wells, leaving the oil in other areas relatively unrecovered. There is a need for a low-cost fluid that can be injected into such spill zones (from either injection wells or production wells) to reduce fluid mobility, thereby diverting the pressure energy by displacing the oil from the fluid. the areas of lower permeability adjacent. In certain formations, oil recovery can be reduced by cone formation of either the gas down or the water up, to the interval where the Oil is being produced. Therefore, there is a need for a low cost injectant that can be used to establish a horizontal "fill" of low mobility fluid to serve as a vertical barrier between the oil producing zone and the area where the formation of oil is occurring. cone. Such a fluid of low mobility will retard the vertical cone formation of gas or water, in order to improve the production of oil in this way. For moderately viscous oils - that is, those having viscosities of about 20-100 centipoise (cP) - water-soluble polymers such as polyacrylamides or xanthan gum have been used to increase the viscosity of the water, injected to displace the oil. the formation. For example, polyacrylamide was added to water, used for the flooding with water of a 24 cP oil in the Sleepy Hollow Field, Nebraska. Polyacrylamide was also used to increase the viscosity of the water, used to flood a 40 cP oil in the Chateaurenard Field, France. With this process, the polymer is dissolved in the water, increasing its viscosity. While water-soluble polymers can be used to achieve a flood with water of favorable mobility for oils of low viscosity to moderately viscous, usually they can not be economically applied to achieve a displacement favorable mobility of more viscous oils - that is, those having viscosities of about 100 cP or higher. These oils are so viscous that the amount of polymer needed to achieve a favorable mobility ratio would usually be uneconomical. In addition, as is known to those skilled in the art, the polymer dissolved in the water is frequently desorbed from the drive water on the rock surfaces of the formation, trapping it and making it ineffective to increase the viscosity of the water. This leads to loss of mobility control, poor oil recovery and high polymer costs. For these reasons, the use of polymer floods to recover oils having viscosities above 100 cP is not usually technically or economically feasible. Also, the performance of many polymers is adversely affected by the levels of dissolved ions, typically found in formations, placing limitations on their use and / or effectiveness. Water and oil macroemulsions have been proposed as a method to produce viscous drive fluids, which can maintain effective mobility control while displacing moderately viscous oils. For example, water-in-oil and oil-in-water macroemulsions have been evaluated as impulse fluids to improve oil recovery from oils viscous Such emulsions have been created by the addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. The emulsions were stabilized by soap films created by the saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the interfacial tension of the oil / water, acting as surfactants to stabilize the water-in-oil emulsion. Therefore, it is well known that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., the caustic substance) to produce a soap film, to reduce the interfacial tension of the oil / water. Several studies on the use of caustic substance to produce such emulsions have demonstrated technical feasibility. However, the practical application of this process to recover oil has been limited by the high cost of the caustic substance, the probable absorption of the soap films on the rock formation, leading to the gradual decomposition of the emulsion, and the sensitivity of the viscosity of the emulsion to minor changes in the salinity of the water and the water content. For example, because most formations contain water with many dissolved solids, emulsions that require fresh or distilled water often fail to achieve design potential, because such low water conditions Salinity are difficult to reach and maintain within the actual formation. The ionic species can be dissolved from the rock and the fresh water injected can be mixed with resident water of higher salinity, causing the decomposition of the stabilized emulsion of low tension. Several methods have been used to selectively reduce the permeability of high permeability "stealing" zones in a process generally referred to as "profile modification". Typical agents that have been injected into the reservoir to effect a reduction in the permeability of contact zones include polymeric gels or cross-linked aldehydes. Polymer gels are formed by crosslinking polymers such as polyacrylamide, xanthan, vinyl polymers or lignosulfonates. Such gels are injected into the formation, where the crosslinking reactions cause the gels to become relatively rigid, thereby reducing the permeability to flow through the treated zones. In most applications of these processes, the region of the formation that is affected by the treatment is restricted to the place close to the inner diameter of the well, due to the cost and the reaction time of the gelling agents. Once the treatments are in the right place, the gels are relatively immobile. This can be a disadvantage, because the Drive fluid (for example, water in a flood with water) eventually finds a path around the immobile gel, reducing its effectiveness. The best performance should be expected if the profile modification agent could move slowly through the formation to plug the newly created stealing areas, penetrating significant distances from the injection or production wells. McKay, in U.S. Patent No. 5,350,014, discloses a method for producing heavy oil or bitumen from a formation that is subjected to thermal recovery. McKay describes a method for producing oil or bitumen in the form of oil-in-water emulsions by carefully maintaining the temperature profile of the sweep zone above a minimum temperature Tc. If the temperature of the oil-in-water emulsion is maintained above this minimum temperature, the emulsion will be able to flow through the porous underground formation for collection in the production well. McKay describes another modality of his invention, in which an oil-in-water emulsion is inserted into a formation and maintained at a temperature below the minimum temperature. This relatively immobile emulsion is used to form a barrier to plug the exhausted chipping zones in formations that are produced by thermal methods, including control of the Vertical cone formation of water. However, the method described by McKay requires careful control of the temperature within the formation zone and, therefore, is useful only for thermal recovery methods. Consequently, the method described by McKay could not be used for non-thermal recovery (referred to as "cold flow") of heavy oil. Recently a new process has been described that uses emulsions stabilized with solids, novel, for recovery of improved oil. U.S. Patent No. 5,927,404 discloses a method for using the novel solid stabilized emulsion as a drive fluid to displace hydrocarbons for improved oil recovery. U.S. Patent No. 5,855,243 claims a similar method for using an emulsion stabilized with solids, whose viscosity is reduced by the addition of a gas, as a driving fluid. U.S. Patent No. 5,910,467 claims the novel solid stabilized emulsion described in U.S. Patent No. 5,855,243. U.S. Patent No. 6,068,054 discloses a method for using the novel solid stabilized emulsion as a barrier to divert the flow of fluids in the formation. The preparation of an emulsion stabilized with solids, with optimal properties, is the key to use successfully the emulsion for improved oil recovery. Two important properties are a stability of the emulsion and its rheology. The emulsion stabilized with solids must be shelf stable, that is, the emulsion must be able to remain as a stable emulsion without separation of water or oil when left unchanged. In addition, the emulsion must be stable under flowing conditions through the porous media, i.e. in an underground formation. The rheological characteristics of the emulsion are also important. For example, the EOR methods for which this emulsion can be used include injecting the emulsion as a driving or barrier fluid in an underground formation. Accordingly, the emulsion must have an optimum viscosity for injection and serve either as a drive or barrier fluid. In the practice of EOR, and particularly with the use of the emulsion as a driving fluid, it is useful to equalize the rheology of the emulsion with the rheology of the underground oil to be produced. The displacement of the oil using a driving fluid is typically more efficient when the driving fluid has a viscosity larger than that of the oil to be displaced. In addition to providing stability to the stabilized emulsion with solids, the invention described herein, will allow the user to prepare emulsions stabilized with solids with a wide range of rheology. to match that of the oil to be produced. Because water and oil are readily available at most production sites, water-in-oil emulsions are a good choice for making emulsions stabilized with EOR solids. Some oils have the chemical composition and physical properties necessary to make water-in-oil emulsions stabilized with solids, stable, with a wide range of solids. The added solids interact with the oil components, ie, polar compounds and asphaltenes, resulting in an increase in their effectiveness as surface active agents. This interaction is specific to the type of solids and the composition of the oil to which they are added. However, if the oil does not contain the correct type and sufficient concentration of polar and asphaltene compounds, the addition of solids is ineffective, because the solids are not properly and appropriately modified to function as stabilizers of the oil interlayer. Water. Therefore, some oils do not form water-in-oil emulsions stabilized with solids, stable, with some solids, or, some oils can form stable emulsions with some types of solids, for example silica, and can not form similar stable emulsions with other types. of solids, for example, clays and fine coal dust. The previously cited technique suggests that asphaltenes or polar hydrocarbons can be added to these oils to improve their ability to form stable emulsions. U.S. Patent No. 5,855,243, column 7, lines 6-10; U.S. Patent No. 5,927,404 column 6, lines 44-47; U.S. Patent No. 5,910,467 column 7, lines 3-6. However, this addition is not always successful because the incompatibility between some components of the oil and the asphaltenes and the added polar compounds can result in phase separation or rejection of the added compounds. These cases limit the scope of the inventions described in the North American patents cited above. To broaden the scope and improve the emulsions stabilized with solids, described in U.S. Patent Nos. 5,927,404, 5,855,243, 5,910,467, 6,068,054, a process is needed that suitably modifies the composition of the oil, so as to be sensitive to the addition of solids to the oil. the preparation of water-in-oil emulsions, stable. The present invention meets this need. BRIEF DESCRIPTION OF THE INVENTION According to the invention, a method is provided for improving the stability of a water emulsion in stabilized oil with solids, the method comprising the step of pretreating at least a portion of the oil before emulsification. In one embodiment of the invention, the oil pretreatment step comprises the addition of dilute organic or mineral acid to at least a portion of the oil prior to emulsification. In another embodiment of the invention, the oil pretreatment step comprises the addition of a lignosulfonate additive to at least a portion of the oil prior to emulsification. In another embodiment of the invention, the oil pretreatment step comprises sulfonating at least a portion of the oil prior to emulsification. In another embodiment of the invention, the oil pre-treatment step comprises heat treating at least a portion of the oil in an inert environment prior to emulsification. In another embodiment of the invention, the oil pretreatment step comprises thermally oxidizing at least a portion of the oil prior to emulsification. You can also use combinations of these modalities. In addition, a method for producing hydrocarbons from an underground formation is described, which comprises: a) making a water-in-oil emulsion stabilized with solids, with the oil pretreated; b) contact the formation with the stabilized emulsion with solids and c) produce hydrocarbons from the formation using the emulsion stabilized with solids. DETAILED DESCRIPTION OF THE INVENTION Water-in-oil emulsions stabilized with solids are generally described in U.S. Patent Nos. 5,927,404, 5,855,243 and 5,910,467. Such emulsions are made by the process of combining oil with solid particles of submicron size to microns and mixing with water until the emulsion of water in oil stabilized with solids is formed. As described in the North American patents referred to above, the solid particles must have certain physical properties. The individual particle size must be small enough to provide adequate surface area coverage in the internal droplet phase. If the emulsion is to be used in a porous underground formation, the average particle size must be smaller than the average diameter of the pore passages in the porous underground formation. The methods to determine the average particle size are discussed in US patents previously cited. The solid particles can be spherical or non-spherical in shape. If they are spherical in shape, the solid particles should preferably have an average size of about five microns or less in diameter, more preferably about two microns or less, even more preferably about one micron or less and much more preferably , 100 nanometers or less. If the solid particles are non-spherical in shape, they should preferably have an average size of about 200 square micras of total surface area, more preferably of about twenty square micras or less, even more preferably of about ten square micras or smaller and much more preferably, a square or smaller square. The solid particles must also remain undissolved in both the oil and water phases of the emulsion under the conditions of the formation. The present invention allows the formation of stable, oil-stable, water-in-oil emulsions of oil, which would otherwise lack suitable polar and asphaltene compounds to form such stable emulsions. The oil necessary to make a stable emulsion using the method described in U.S. Patent Nos. 5,927,404, 5,855,243 and 5,910,467, must contain a sufficient amount of asphaltenes, polar hydrocarbons or polar resins to stabilize the interaction of the solid-oil particle. But, as mentioned, some oils do not have enough type or amounts of these compounds to allow the formation of stabilized emulsions with stable solids. In accordance with the present invention, the oil is pretreated to promote the formation of a water-in-oil emulsion stabilized with solids, stable. The oil used to make the solid stabilized emulsion of the present invention may be oil of any type or composition, including, but not limited to, crude oil, refined oil, oil blends, chemically treated oils, or mixtures thereof. . Crude oil is unrefined liquid petroleum. Refined oil is crude oil that has been purified in some way, for example, the removal of sulfur. Crude oil is the preferred oil used to carry out this invention, more preferably, crude oil is produced from the formation where the emulsion is to be used. The crude oil produced may contain formation gas, or water or brine from the formation mixed with the oil. It is preferred to dehydrate the crude oil before the treatment, however, in this invention also mixtures of oil, formation gas and / or brine from the formation can be used.

Preferably, formation water is used to make the emulsion, however, fresh water can also be used and the ionic concentration can be adjusted as necessary to help stabilize the emulsion under the conditions of formation. Water-in-oil emulsions stabilized with solids according to the present invention are useful in a variety of improved oil recovery applications generally known in the art, including, without limitation, the use of such emulsions (a) as fluids of drive to displace hydrocarbons in an underground formation; (b) to fill the areas of high permeability formation for "profile modification" applications to improve the performance of subsequent EOR; and (c) to form effective horizontal barriers, for example, to form a barrier to vertical flow of water or gas, to reduce cone formation of water or gas to the oil producing zone of a well. Attached in Table 1 are the characterization data of the detailed physical and chemical properties for three different types of crude oil that are referred to as Crude Oil # 1, Crude Oil # 2 and Crude Oil # 3. The Crude Oil # 1 and the Crude Oil # 3 have properties that make possible the formation of emulsions of water in crude oil, stable, with the addition of solids, as described in the US patents Nos. 5,927,404, 5,855,243 and 5,910,467. However, Crude Oil # 2 does not form an emulsion of water in oil stabilized with solids, stable, when the same method is used.

TABLE 1 PHYSICAL AND CHEMICAL PROPERTIES OF RAW OILS PROPERTY Oil Oil Crude Oil # 1 Crude # 2 Crude # 3 Gravity API 16.8 15.5 8.6 Viscosity (cP) 4800 2400 384,616 (25 ° C, 1 sec "1) Interphase voltage (dynes / cm) 2.2 33.7 Sea water Asphaltenes (insoluble in n-heptane (% by weight)) 0.1 ± ± 00..0022 2.6 13.7 Toluene's Equivalence 0.0 14 20 Sulfur (% by weight) 0.12 0.98 3.89 Nitrogen (% by weight) 0.18 0.07 0.19 Distillation cuts (% in volume) IC5 / 175F Naf. Light 0.6 0.2 175/250 ° F Naf. Medium 1.3 250/375 ° F Naf. Heavy 1.80 3.22 1.0 TABLE 1 (continued) PHYSICAL AND CHEMICAL PROPERTIES OF RAW OILS PROPERTY Oil Oil Crude Oil # 1 Crude # 2 Crude # 3 Distillation Cuts (% by volume) 375/530 ° F Kerosene 7.83 12.39 4.8 530/650 ° F Lt. Gasoil 9.88 14.27 9.5 650/1049 ° F PGO 38.04 42.41 38.8 1049 ° F + Residue 42.45 25.80 45.7 HPLC fractions (% < an weight) Mass recovery 83.8 56.6 66.99 Saturated 41.7 28.51 17.67 I-Ring 7.5 11.40 10.07 2-Ring 7.0 9.85 12.89 3-Ring 7.6 7.96 10.15 4-Ring 13.0 16.06 20.93 Polar 23.2 26.23 28.29 Aromaticity 17.1 20.27 22.37 Iatrascan data - Saturated 27.2 19.4 6.4 Aromatics 44.7 44.7 42.5 NSO's 19.0 30.1 29.0 Asphaltenes (insoluble in n-pentane) (% by weight) 8.9 5.8 22.1 TABLE 1 (continued) PHYSICAL AND CHEMICAL PROPERTIES OF RAW OILS PROPERTY Oil Oil Crude Oil # 1 Crude # 2 Crude # 3 Data from Iatrascan Arom. / Saturated 1.64 2.3 6.66 NSO's / Asf. (Insoluble in n-pentane) 2.13 5.19 1.31 TAN 6.2 6.2 3.13 Distribution Determined with HPLC of Acid Fractions (%) 250 MW 8.5 47.2 22.4 300 MW 23.9 24.5 20.7 425 MW 30.5 15.9 20.4 600 MW 20.4 7.0 14.6 750 MW 16.7 5.4 21.7 Acid Aromaticity 8.6 17.2 19.0 Metals (ppm) Ca 30-160 4.22 1.83 Na 10.4-15.5 1.51 11.2 V 0.16-0.31 69.6 434 Ni 9.05-13.0 65.6 102 The Crude Oil # 2 differs from the Crude Oils # 1 and # 3 in the following ways: 1. Crude Oil # 2 has a higher ratio of resin / asphalt, 2. Crude Oil # 2 has a higher proportion of naphthenic acids of lower molecular weight and 3. Crude Oil # 2 has lower amount of calcium and sodium compared with the Crude Oil # 1. These differences suggest: 1. the active species on the surface, that is, asphaltenes and acids / resins, which are essential key components for emulsification, are not readily available to stabilize water droplets in Crude Oil # 2, and 2. oil pretreatment to alter their physical properties and chemical composition is a potential route to improve the stability of the emulsion. Accordingly, the present invention describes an oil pretreatment method for increasing the stability of the stabilized emulsion with solids. Now several modalities of this invention will be described. As one of ordinary skill in the art can appreciate, one embodiment of this invention can be used in combination with one or more other embodiments of this invention, which can provide synergistic effects in the stabilization of the emulsion stabilized with solids.

Oil Pretreatment with Diluted Acid A method of pretreating the oil to improve its ability to form a water-in-oil emulsion stabilized with solids, stable, is to pretreat the oil with dilute mineral or organic acid prior to emulsification. This pretreatment with acid results in modifications to the oil and the surface of the solids: (1) The components of the oil containing basic nitrogen are converted to the corresponding mineral or organic acid salts. These salts are more active on the surface than the same components that contain basic nitrogen and thus contribute to improving the stability of the water-in-oil emulsion stabilized with solids; (2) If the oil contains naphthenic acids, the stronger mineral or organic acids displace the naphthenic acids from the basic nitrogen-containing compounds, to which they are complexed, to thereby provide higher surface activity; (3) Acid protons act to protonate the anionic charged sites on the surface of the solids and thus modify the surface of the solids to improve their interaction with the oil components active on the surface (either pre-existing in the oil or generated by acid treatment); (4) If the oil contains calcium and naphthenic acids, the mineral or organic acids can displace the calcium and free the naphthenic acids, which are more active on the surface than the calcium naphthenates.

Preparation of the Water Emulsion in Oil Stabilized with Solids Using the Pretreatment with Diluted Acid. To perform this embodiment of the invention, dilute mineral or organic acid is added to the oil before emulsification. Solid particles can be added to the oil either before or after the acid pretreatment, but it is preferred to add the solids to the oil and then pre-treat the oil with the solids with acid. After pretreatment with acid and addition of solids, the emulsion stabilized with solids is formed by adding water in small aliquots or continuously and when mixing, preferably at a ratio of between 1000 to 12000 rpm, for a sufficient time to disperse the water as small droplets in the continuous oil phase. It is preferred to have a water concentration in the water-in-oil emulsion of 40 to 80%, more preferably 50 to 65%, and much more preferably 60%. The acid is added to the oil with mixing, preferably for about 5 to 10 minutes at 25 to 40 ° C. The preferred proportion of acid treatment is between 8 and 30,000 ppm. The diluted acid can be mineral acid, organic acid, a mixture of mineral acids, a mixture of organic acids, or a mixture of mineral and organic acids. The preferred mineral acids are hydrochloric acid and sulfuric acid. However, other mineral acids may be used, including, but not limited to, perchloric acid, phosphoric acid, and nitric acid. The preferred organic acid is acetic acid. However, other organic acids may also be used, including, but not limited to, toluene sulphonic acid, alkyl toluene sulphonic acids, mono, di and trialkyl phosphoric acids, organic mono- or di-carboxylic acids (eg, formic), acids C3 to C16 organic carboxylic acids, succinic acid and naphthenic acid of petroleum. The naphthenic petroleum acid may also be added to increase the surface activity in the oil, or oils containing high content of naphthenic acid may be mixed with the oils of interest to provide increased surface activity. The solid particles are preferably hydrophobic in nature. A hydrophobic silica, sold under the trade name Aerosil® R 972 (product of DeGussa Corp.) has been found to be an effective solid particulate material for a number of different oils. Other hydrophobic solids (or oleophilics) can also be used, for example, bentonite clays divided and moistened with oil, kaolinite clays, organophilic clays or carbonaceous asphaltenic solids. The preferred treatment ratio of solids is 0.05 to 0.25% by weight, based on the weight of the oil. After the emulsion is prepared, its pH can be adjusted by adding a calculated amount of weak aqueous base to the emulsion, for a time sufficient to raise the pH to the desired level. It is desirable to adjust the pH of the emulsion in the range of 5 to 7. However, adjusting the pH is optional, since in some cases it is desirable to inject an acidic emulsion and allow the formation of the deposit to regulate the emulsion to alkalinity of the deposit. Ammonium hydroxide is the preferred base for pH adjustment. The strongest bases, similar to sodium hydroxide, potassium hydroxide and calcium oxide have a negative effect on the stability of the emulsion. One possible explanation for this effect is that strong bases tend to invert the emulsion, that is, convert the water-in-oil emulsion to oil-in-water emulsion. Such investment is undesirable for purposes of this invention. In addition to increasing the stability of the water-in-oil emulsion stabilized with solids, the acid pretreatment method results in an emulsion with lower viscosity compared to that produced without pretreatment with acid. This reduced viscosity helps to improve the injection capacity of the emulsion. Thus, the viscosity of an emulsion stabilized with solids can be decreased by suitably adjusting the amount of pretreatment with acid. This ability to manipulate the viscosity of the emulsion allows the user to optimally match the rheological characteristics of the emulsion with those of the oil to be specifically recovered for the particular type of EOR method used. As mentioned in U.S. Patent Nos. 5,855,243 and 5,910,467, gas can also be added to further decrease the viscosity of the emulsion. Another embodiment of this invention is to pretreat a side stream or masterbatch of oil with dilute acid as described above and subsequently mix the side stream with a main stream of oil before the addition of water and the emulsification. This preferred main stream of oil is untreated raw oil, however, it can be any oil, including oil that has been treated to improve its ability to form a non-stable emulsion or that has been treated to optimize its rheology. If the side stream method is used, the amounts of solids and dilute acid needed for the side stream are scaled accordingly to obtain the desired amounts in the resulting emulsion.

Examples: The following laboratory tests were conducted to demonstrate the effectiveness of acid pretreatment in improving an oil's ability to form stable, solid-stabilized water-in-oil emulsions. These examples focused on Crude Oil # 2 and other crude oil, Crude Oil # 4. None of these crude oils form stable, solid-stabilized emulsions by the method described in U.S. Patent Nos. 5,927,404, 5,855,243 and 5,910,467. The physical properties for Crude Oil # 4 are given in Table 2. Tests showed that acid pretreatment improved the oils' capacities to form stable, solid-stable emulsions. Stable emulsions were formed in the pH range of 1.2 to 7.0, and up to 72% by weight of water was incorporated into these emulsions.

TABLE 2 PHYSICAL AND CHEMICAL PROPERTIES OF RAW OILS PROPERTY Crude Oil # 4 Gravity API 17.2 Viscosity (cP) 8500 (25 ° C, 1 sec "1) Asphaltenes (insoluble in n-heptane) (% by weight) 0.1 Asphaltene (insoluble in cyclohexane) (% by weight) 3.25 TABLE 2 (continued) PROPERTY Crude Oil # 4 Equivalence of Tolueno 0. .0 Sulfur (% by weight) 0. .12 Nitrogen (% by weight) 0. .26 Distillation Cuts (% by volume) IC5 / 175 ° F Naf. Lightweight 175/250 ° F Naf. Medium 250/375 ° F Naf. Heavy OJ 03 375/530 ° F Kerosene 6 09 530/650 ° F Lt. Gasoil 8. ' 67 650/1049 ° F PGO 36 .48 1049 ° F + Residue 48 .73 HPLC fractions (% by weight) Mass recovery 84 .4 Saturated 43 .3 1-Ring 7. 6 2-Ring 6. 8 3-Ring 7. 5 4-Ring 12 .6 Polar 22 .2 Aromaticity 15 .6 Saturated Iatroscan data 35 .4 Aromatics 39 .8 TABLE 2 (continued) PROPERTY Crude Oil # 4 Data from Iatroscan NSO'S 15.4 / Asfalteno 9.4 Arom. / Saturated 1.13 NSO's / Asf. 1.64 TAN 5.4 Distribution Determined with HPLC of Acid Fractions (%) ** 250-300MW 15.4 300-425MW 14.7 425-600MW 27.1 600-750MW 21.5 750 + MW 21.3 Acid Aromaticity 8.6 Metals (ppm) Ca 400-900 Na - 7.7-15.3 V 0.2-0.9 Nor 11.2-17.9 Mn 13.1 K 181-935 Mg 1.1-25.2 In a typical experiment, dilute aqueous mineral or organic acid (concentration of 0.35 to 35%) was added to the oil at a treatment rate of 8 to 30,000 ppm and completely mixed for 10 minutes using a Waring blender or a Silverson homogenizer. Solid particles were added followed by mixing. After the pretreatment with acid was completed, water was added to the oil in small aliquots with mixing, which resulted in a water-in-oil emulsion stabilized with solids. Emulsions prepared by pretreating the oil with dilute aqueous acid were subjected to the following tests: 1. Rack stability at 25 ° C for 48 hours 2. Optical microscopy and / or Nuclear Magnetic Resonance (NMR) for the determination of the size of the water droplet / size distribution 3. Microcentrifuge test - stability of the emulsion to centrifugation (as described in Appendix-1) 4. Stability of the emulsion - flow through a sand pack (this test " micropercolation is described in Appendix-1) 5. Rheology of the emulsion using a Brookfield viscometer (cone (# 51) and plate configuration) at 60 ° C e? a range of shear stress of 1.92 to 384 sec "1. The results of the test for the Crude Oil # 2 using the pretreatment with hydrochloric acid and sulfuric acid, are presented in Tables 3-6 The results for the Crude Oil # 4 using the pretreatment with sulfuric acid and acetic acid, are presented in the Table 7. Example 1: Hydrochloric Acid Pretreatment of Crude Oil # 2 Crude Oil # 2 was used to prepare a 60/40 water-in-oil emulsion with 0.15% by weight of hydrophobic silica, Aerosil® R 972, but without acid pretreatment. As shown in Table 3, the emulsion stabilized with solids was shelf stable, however, the emulsion was unstable in the microcentrifuge and micropercolation tests as demonstrated by the high separation of water (brine) (% bbo). The dispersed water droplets varied in size from 1 to 10 microns in diameter. The effect of the pretreatment with hydrochloric acid on the stability of the emulsion stabilized with solids was then tested. Crude Oil # 2 was used to prepare a water-in-oil emulsion stabilized with solids, 60/40. However, in this example, the oil was pretreated with hydrochloric acid at a rate of 38,000 ppm followed by the addition of 0.15% by weight of Aerosil® R 972. The dispersed water droplets varied in size from 1 to 2 microns in diameter. As shown in Table 3, the pretreatment with hydrochloric acid resulted in improved stabilization in the centrifuge and in the micropercolation, and therefore improved the stability of the emulsion, as indicated by the decreased amount of water separation in the both tests.

TABLE 3 Pretreatment of Crude Oil # 2 with Hydrochloric Acid Pretreatment procedure: 38,000 ppm of HCl added to the crude and mixed using the Waring Mixer for 10 minutes. Crude HCl / Stabilized Particles- Diameter Micro- Micro- Water Solid in the centrifuge- (Aerosil® Shelf Droplet leak R972) ppm (% by weight) (2 days) (microns) (% bbo) (% bbo) ) 0 40/60 0 0 .. .1155 eessttaabbllee 10 a 1 18 35 38,000 40/60 0, .0 stable 10 to 1 0 20 38,000 40/60 0. .15 stable 2 to 1 0 5 38,000 33/66 0. .15 stable 2 to 1 0 4 bbo :: separation of brine (water ) in the microcentrifuge test using Ottawa sand.

Example 2: Sulfuric Acid Pretreatment of Crude Oil # 2 Crude Oil # 2 was used to make a 60/40 water-in-oil emulsion containing 0.15% by weight of Aerosil® R 972 without acid pretreatment. As shown in Table 4, this emulsion, although stable on the shelf, was unstable in the microcentrifuge and micropercolation tests. The dispersed water droplets varied in size from 1 to 10 microns in diameter. An emulsion of water in crude oil 60/40 was prepared with pretreatment with sulfuric acid of Crude Oil # 2, but without the addition of solids. Sulfuric acid was added at a rate of 8750 ppm, based on the weight of the oil. The resulting emulsion was very unstable in the tests in the microcentrifuge and in the micropercolation. An emulsion of water in crude oil 60/40 was prepared with pretreatment with sulfuric acid of Crude Oil # 2, at a rate of 8750 ppm, based on the weight of the oil, with 0.15% by weight of Aerosil® R 972. As is shown in Table 4, this procedure resulted in a stable emulsion. The dispersed water droplets varied in size from 1 to 2 microns in diameter. The pH of the resulting emulsion was 1.2. Pretreatment with sulfuric acid from the oil resulted in improved stability in the microcentrifuge and micropercolation as indicated by the diminished amount of separation of water or brine (% bbo). An emulsion of water in crude oil 60/40 was prepared with pretreatment with sulfuric acid of Crude Oil # 2, at a treatment rate of 8750 ppm, based on the weight of the oil, followed by the addition of 0.15% by weight of a hydrophobic silica, Aerosil® 300 (product of DeGussa Corp.) This procedure did not provide a stable water-in-oil emulsion, since the emulsion has increased the water separation in the microcentrifuge and micropercolation tests. The poor performance of the hydrophilic silica, Aerosil® 300, suggests that hydrophobic solids, in general, are required for the formation of stable emulsions using pretreatment with dilute acid.

TABLE 4 Pretreatment of Crude Oil # 2 with Sulfuric Acid Proc. of Pretreatment: 8750 ppm of H2S04 added to the crude oil and mixed using the Waring Mixer for 10 minutes. H2S04 Oil / Stabilized Particles- Diameter Micro- Micro- Water Solids in the centrifuge- (Aerosil® Shelf Droplet R972 leakage) ppm (% by weight) (2 days) (microns) (% bbo) (% bbo) 0 40/60 0.15 stable 10 to 1 18 35 8750 40/60 0.0 stable 10 to 1 20 91 8750 40/60 0.15 stable 2 to 1 0 0 8750 33/66 0.15 stable 2 to 1 1 2 8750 40/60 0.10 stable 2 to 1 0 0 8750 40/60 0.075 stable 2 to 1 0 0 bbo :: separation of brine (water) in the micropercolation test using Ottawa sand.

Example-3 Increase in Water Content of Crude Oil # 2 Pretreated with Sulfuric Acid As shown in Table 5, about 70% by weight of water could be incorporated into the resulting water-in-oil emulsion with solids, made by pretreating Crude Oil # 2 with dilute sulfuric acid. Up to about 72% by weight of water, an increase in the size of the water droplet was observed. Above about 80% by weight of water, the emulsion phase was separated as an emulsion and excess water. The rheological measurements show that the viscosity of the emulsions increased with an increase in the water content of the emulsion.

TABLE 5 Crude Oil # 2 Pretreated with. Sulfuric Acid Water% StabiMicro- Micro- Diameter Viscosity in centrifuge of the 35C, 9.6 s "1. Shelf leakage Droplet (% bbo) (% bbo) (micras) 60 if 0 0 <2 15,400 65. 5 yes 0 0 < 2 15,888 69.2 if 0 0 < 2 20,152 71. 4 yes 0 0 < 2 27,852 75 yes 0 5 < 2 - 5 26,214 80 yes 0 10 < 2 - 10 85 the phase is separated as an emulsion and water in excess Note: Solids: 0.15% by weight of Silica Aerosil® R 972 bbo: separation of brine (water) in the micropercolation test using Ottawa sand Proportion of treatment with sulfuric acid: 8750 ppm Example-4: Decrease in Solids Content of a Water Emulsion in Crude Oil # 2 60/40 As shown in Table 6, stable emulsions were prepared with the hydrophobic silica, Aerosil® R 972, which varies in concentration from 0.025% by weight to 0.15% by weight. The viscosity of the emulsions decreased with the decrease in solids content.

TABLE 6 Effect of the Decrease in Solids Content of the Crude Oil Emulsion # 2 Pretreated with Sulfuric Acid % of Par- Stabi- Micro- Micro- Diameter Viscosity in centric-percola- 35C, 9.6 s "1. Solid tantal leakage (Aerosil® (% bbo) (% bbo) (micras) R972) 0.15 yes 0 0 <2 15400 0. 1 yes 0 0 < 2 7864 0.075 if 0 0 < 2 7536 0. 05 yes 0 0 < 2 8192 0. 025 yes 0 0 < 2 - 5 6389 Note: Oil / Water Ratio = 40/60 bbo: separation of brine (water) in the micropercolation test using Ottawa sand. Proportion of treatment with sulfuric acid: 8750 ppm Example-5: Pretreatment with Sulfuric Acid and Acetic Acid of Crude Oil # 4 Similar to the results in Crude Oil # 2, the acid pretreatment of Crude Oil # 4 resulted in improved stability of the resulting stabilized, solid emulsions. As indicated in the data in Table 7, the pretreatment of Crude Oil # 4 with sulfuric acid at a rate of 8750 ppm, based on the weight of the oil, followed by the addition of 0.15% by weight of Aerosil® R 972, resulted in result in a stable emulsion. The pretreatment of Crude Oil # 4 with acetic acid at a treatment rate of 24,500 ppm, followed by the addition of 0.15% by weight of Aerosil® R 972, also resulted in a water-in-oil 60/40 emulsion stabilized with solids. , stable. The viscosity of the emulsion treated with acetic acid was found to be lower than the counterpart treated with sulfuric acid, suggesting that the nature of the acidifying agent could influence the viscosity of the emulsion.

TABLE 7 Pretreatment with Crude Oil Acid # 4 Acid% Soli- Stabi- Micro- Micro- Diameter Viscosity Centrosequence- of the sity (Aerosil® in leakage droplet 60C, R972) Shelf (% bbo) ( % bbo) mieras) 9.6 s "1. None 0.15 yes 0 9 < 2 - 10 5240 Sulfuric 0.15 yes 0 3.5 < 2 2948 Acetic 0.15 yes 0 0 < 2 4095 Note: Viscosity of Crude Oil # 4 = 164cP @ 60C, 9.6 s "1. bbo: separation of brine (water) in the micropercolation test using Ottawa sand Proportion of treatment with sulfuric acid: 8750 ppm Proportion of treatment with acetic acid: 24,500 ppm Example-6: Adjusting the pH of the Emulsion Treated with Acid Two procedures are described for producing water-in-oil emulsions in the preferred pH range of 5 to 7: a) Neutralization of the emulsion of oil treated with acid, preformed, with the appropriate amount of base: Neutralization of the oil pretreated with acid, with ammonium hydroxide before or after the addition of water is the preferred method for increasing the pH of the emulsion. In contrast, neutralization of the emulsion with sodium hydroxide or calcium oxide results in destabilization of the emulsion. As previously mentioned, one possible explanation for this effect is that ammonium hydroxide is a weaker base than hydroxide of sodium or calcium oxide. Strong bases tend to invert the emulsion, ie convert the water-in-oil emulsion to the oil-in-water emulsion. Such investment is undesirable for the process of this invention. b) Reduction of the Treatment Ratio with Acid at Fairly Accurate Levels to Neutralize the Basic Components of the Oil: Another procedure to obtain an emulsion in the pH range of 5-7 is to reduce the proportion of acid treatment to fairly precise levels to neutralize the basic components of the oil. The acids used in this experiment were hydrochloric acid, sulfuric and acetic. For Crude Oil # 2 and Crude Oil # 4, it was found that an acid treatment ratio of 8.7 ppm was adequate to produce the required emulsions at a pH of 5.5 to 6.5. A summary of the properties of the emulsion for the Crude Oil # 4 pretreated with 8.75 ppm of sulfuric acid, is given in Table 8.

TABLE 8 Summary of the Properties of Emulsion, of an Emulsion of Water in Oil Prepared by Pretreatment of Crude Oil # 4 with 8.75 ppm of Sulfuric Acid Properties of the Emulsion: Crude: 40% by weight Water: 60% by weight Hydrophobic Silica (R 972): 0.15% by weight Size of the Water Droplet (Average Diameter): 6 microns Shelf Stability: > 2 weeks Stability at Centrifuging: 0% water separation Stability to Percolation through Berean sand: 16% water separation Viscosity: 3700 cP @ 60C, 9.6 sec "1. PH: 6.2 Example-8: Addition of Gas for the Reduction of the Viscosity of Water Emulsions in Oil The addition of C02 to the emulsion of oil pretreated with acid, is effective in reducing the viscosity of the emulsion. Experiments were conducted on elaborate emulsions of Crude Oil # 2 pretreated with 8700 ppm of sulfuric acid and 0.15% by weight of Aerosil® R 972. The results shown in Table-9 reveal that at a pressure of 500 psi and the temperature of the corresponding deposit, the reduction of the viscosity of the emulsion is feasible using carbon dioxide gas. Other gases similar to ethane and propane can also decrease the viscosity of the emulsion.

TABLE 9 Influence of CQ2 on a Water Emulsion in Crude Oil Stabilized with Solids, Pretreated with Acid Emulsion Tem. VISCOSITY (Cp) at 10 sec "1 (° C) Viscosity (cP) at 10 sec" 1 Without CO2 with 500 psi of C02 Oil / Crude # 2 35 11213 1671 Oil Pretreatment by Sulfonation Chemistry Another method to pre-treat the oil, to improve its ability to make a water-in-oil emulsion stabilized with solids, is to pretreat the oil with a sulfonation agent prior to emulsification. The sulfonation process can result in chemical modifications to the oil and the surface of the solids. For example, (1) the sulfonation process described herein creates oil components functionalized with sulfur, and these components are active on the surface and aid in the formation of the water-in-oil emulsion; (2) If naphthenic acids are present in the oil, the sulfonation will markedly improve its acidity and interfacial activity through the sulfonate groups chemically bound; (3) The sulfonate groups of the sulfonation agent will also functionalize the surface of the solids and thus modify the surface of the solids to improve their interaction with the oil components active on the surface (preexisting in the oil or generated from the sulfonation reaction ); and (4) The components of the oil containing basic nitrogen are converted to the corresponding sulfonates and / or sulfate salts. These salts are more active on the surface than the components themselves that contain nitrogen base and thus contribute to improve the stability of the emulsion of water in oil stabilized with solids.

Procedure for the Preparation of a Water Emulsion in Oil Stabilized with Solids, Using the Sulphonation Chemistry The oil is pretreated with a sulfonation agent, either before or after the addition of solid particles, and followed by the addition of water. The water is added in small aliquots or continuously, and the mixture is subjected to mixing with shear, preferably between 1000 to 12,000 rpm, for a sufficient time to disperse the water as small droplets in the continuous oil phase, typically between 0.5 to 24 hours. It is preferred to have a water concentration in the emulsion of water in oil of 40 to 80%, more preferably 50 to 65%, and much more preferably 60%. The preferred sulfonation agent is concentrated sulfuric acid. The preferred treatment ratio of sulfuric acid to the oil is between 0.5 to 5% by weight, more preferably 1 to 3% by weight, based on the weight of the oil. Other sulfonation agents can be used alone or in combination with other agents. Such sulfonation agents are generally described in E. Gilbert, Sulfonation and Related Reactions, Interscience, New York, (1965). Other common sulfonation agents which may be useful in the present invention include fuming sulfuric acid, sulfur trioxide, alkali disulfates, pyrosulfates, chlorosulfonic acid and a mixture of manganese dioxide and sulfurous acid. The process temperature during sulfonation can be from -20 ° C to 300 ° C, preferably from 10 ° C to 100 ° C and more preferably from 20 ° C to 60 ° C. The reaction can be accelerated by various methods, including, without limitation, the thermal, mechanical, sonic, electromagnetic, vibration, mixing and spray method. As can be appreciated by one of ordinary skill in the art, the amount of sulfonating agent useful in the present invention can be adjusted especially according to the nature of the sulfonation agent and the Asphaltene content and resin of the oils. An oil that contains a large amount of asphaltene may require less sulfonation than one that contains a small amount of asphaltene. The amount of asphaltene in the oil can be determined using standard techniques known in the art. The sulfonation range can be from 0.01 to 40%, preferably from 0.1 to 10% and more preferably from 0.1 to 2% of the mass of the solid particles. One method for practicing this embodiment of the invention is first sulfonate the oil and then add the solid particles. However, the addition of the solid particles to the oil and the sulfonation of the mixture are preferred. The solids may be silica, clays, hydrophobic particulates and / or non-functionalized and functionalized asphalts and their corresponding mixtures. The preferred treatment ratio of the solids to the oil is 0.05 to 2.0% by weight solids, based on the weight of the oil. The hydrophobic particulates for this embodiment of the invention are any particulate material wherein the hydrophobicity is greater than 50% and less than 99.9% and the hydrophilic or polar portions are less than 40% and greater than 0.1% of the particulate mass . The hydrophilic or polar portions can be formed as a result of the sulfonation of the combination of hydrophobic particulate materials with oil. Examples of particulate materials Useful hydrophobes in this invention, include, without limitation, phyllosilicates, lignin, lignite, carbon, gilsonite, silica, dolamite, metalloids, layered oxides and quaternary onium phyllosilicates. Functionalized and non-functionalized asphalts are also effective solids for preparing water-in-oil emulsions stabilized with solids, pretreated with sulfonate. In particular, the phosphonated asphalt that has been submerged sufficiently in the oil, preferably for 24 hours at 55 ° C, is an effective solid. The asphalts can be used in their natural state or they can be functionalized, or functionalized by sulfonation agents of the present invention. Non-limiting examples of functional portions are sulfonic acid, phosphoric acid, carboxylic acid, nitric acid or salts thereof, and hydrophilic groups. After the preparation of the emulsion, the pH of the emulsion can be adjusted as previously described in relation to the first embodiment of the invention, related to the pretreatment of the oil with dilute acid. As previously described, a calculated amount of weak base is added to the emulsion and the emulsion is subjected to mixing with shear for a time sufficient to raise its pH to the desired level, preferably in the range of 5-7. Adjustment of pH it is optional, since in some cases it is desirable to inject an acidic emulsion and allow the formation of the deposit to regulate the emulsion to the alkalinity of the deposit. The viscosity of the emulsion increases with sulfonation. However, the viscosity of the emulsion is not a linear function of the addition of sulfonation agent. The viscosity of the emulsion is increased to a reduced ratio as a function of sulfonation. Thus, the user can produce emulsions stabilized with solids, increasingly stable, via sulfonation, while maintaining the desirable rheological properties. In addition, the viscosity of the emulsion can also be reduced by the addition of gas as discussed in U.S. Patent Nos. 5,855,243 and 5,910,467. While sulfonation of the full amount of oil necessary to make such an emulsion is feasible, it is also possible to sulfonate a side stream or master batch of oil and subsequently mix the side stream with a main stream of oil before the addition of water and the emulsification. This main stream of oil is preferably untreated raw oil, however, it can be any oil, including oil that has been treated to improve its ability to form a stable emulsion or that has been treated to optimize its rheology. If the current method is used At the side, the amounts of solids and the sulfonation agent required for the treatment of the side stream are scaled accordingly to obtain the desired amounts in the resulting emulsion.

Examples: This embodiment of the invention has been demonstrated using Crude Oil # 2 and other oil, Crude Oil # 5, since these oils do not form stable, solid-stable emulsions, using the method described in U.S. Patent Nos. 5,927,404, 5,855,243 and 5,910,467. However, as indicated by the experiments in the following, the pretreatment of the oil with the sulfonation chemistry improves the oil's ability to form stable, solid-stabilized water-in-oil emulsions. In a typical experiment, the solid particles are added to the oil and then sulfonated. The concentrated sulfuric acid is used as the sulfonation agent, and is added to a treatment ratio of 3 parts of acid per 100 parts of oil. This mixture is stirred on a hot plate with a magnetic stirrer attachment at a temperature of about 50 ° C. Then water is added to the oil in small aliquots with mixing, which results in a water-in-oil emulsion stabilized with solids. These emulsions were subjected to the following tests: 1. Stability in rack at 25 ° C for 48 hours 2. Optical microscopy and NMR for the determination of water droplet size / size distribution 3. Stability in the centrifuge (described in Appendix-1) 4. Stability of the emulsion: flow through a sand pack (the micropercolation test procedure is given in Appendix-1) Example 1 Crude Oil # 2 and solid particulate materials were co-sulphonated as follows: 12 grams (g) of Oil Crude # 2 and solid particles, comprised of 0.06 g of monomorilonite intercalated with 2-methylbenzyl tallow (Organotrol® 1665, product of Cimar Corp.) and 0.12 g of untreated Billings asphalt ASP-97-021 (Exxon product), were combined in a glass jar. The mixture was stirred at 50 ° C for 72 hours. Sulfuric acid was added in the proportion of 3 parts of acid per 100 parts of oil and the mixture was stirred at 50 ° C for 24 hours. The sulphonated oil and the solids are then combined with 18 g of synthetic brine solution (comprised of 9.4 g of sodium chloride, 3.3 g of CaCl2 (calcium chloride) '2H20, 0.48 g of MgCl2 (magnesium chloride)' 6H20 and 0.16 g of potassium chloride per liter of distilled water). The brine was added dropwise during 30 minutes at 5000 rpm. The emulsion thus formed was mixed during additional minutes at 7500 rpm. The emulsion stabilized with external oil solids, thus produced, was tested for stability using the micropercolation test as described in Appendix-1. The sand used in this test was Ottawa sand and the oil was centrifuged with sand for one minute at 50 ° C. Duplicate samples showed 0% and 3.2% separation of brine (% bbo) after injection through the sand pack. The light microscopy showed the diameter of the water droplet smaller than 20 microns and a majority of particles having diameters less than 7 microns.

EXAMPLE 2 Crude Oil # 5 and oxidized asphalt (OX-97-29-180, product of Imperial Oil) were co-sulphonated according to the previously described procedure. However, in this example, the oil and the asphalt were stirred together for 2.5 hours at 50 ° C before the addition of the sulfonation, sulfuric acid, to 3 parts of sulfuric acid per 100 parts of oil. The sulfonated product was mixed with the synthetic brine solution, as described. The resulting mixture contained 60% aqueous phase content. This external oil emulsion exhibited a pH of 1.6 and was then neutralized to a pH of 7.3 with the addition of ammonium hydroxide and then mixed again in an Arrow 850 mixer at 350 rpm for 15 minutes. The pH of the emulsion approached the pH of Crude Oil # 5. This emulsion showed no separation of brine in the micropercolation test. The diameters of the droplets were less than 10 microns, with most water droplets less than 5 microns. The rheological test using a cone and plate viscometer showed high stability of the emulsion, that is, the viscosity remained essentially constant as a function of the number of cycles.

Example 3 The same experiment was performed using Oil Crude # 5 and montmorillonite interspersed with 2-methylbenzyl tallow (Organotrol® 1665, a product of Cimbar Performance Minerals, Cártersville GA) as the solid particulate material. The crude oil and the solid particles were combined and stirred for 4 hours at 50 ° C before the addition of sulfuric acid. Otherwise, this mixture was sulfonated according to the methods described above. The synthetic brine solution described above was added to the oil and solids and mixed as before. The pH level of the resulting emulsion was also adjusted to 7.5 with the addition of ammonium hydroxide and mixing with an Arrow 850® mixer at 350 rpm for 15 minutes. The external oil emulsion exhibited a droplet diameter of the aqueous phase of less than 10 microns and a majority of brine droplets were less than 5 microns. No separation of brine was found under the micropercolation test described in Appendix-1, using Berea sand.

Example 4 Crude Oil # 2 and untreated asphalt (ASP-97-021, a product of Imperial Oil Corporation, Canada) were cosulfonated. The oil and the asphalt were stirred at 50 ° C for 72 hours before the addition of the sulfuric acid. Otherwise, the sulfonation was performed by the steps described above. The water-in-oil emulsion stabilized with solids was produced with the addition of the synthetic brine solution, described above, and mixing according to the above procedures. However, in this For example, the pH of the emulsion was not adjusted, but remained acidic. Light microscopy showed a droplet diameter of the aqueous phase of less than 10 microns, with a majority of droplets less than 5 microns. No brine separation was found using the micropercolation test described in Appendix-1, using Ottawa sand.

Example 5 12 g of Crude Oil # 2 and 0.06 g of a hydrophobic particulate material, Wolastafil-050-MH-0010® (calcium metasilicate-coated ethylalcoxysilane having a coating of 1% by weight of calcium metasilicate - product from United Mineral Corp.), were co-sulphonated as previously described. In this example, the oil and the particulate material were stirred at 50 ° C for 2.5 'hours before the addition of the sulfuric acid. A water-in-oil emulsion stabilized with solids was produced by the procedures described above, and the pH of the emulsion was adjusted to 6.1 using ammonium hydroxide. Light microscopy revealed a droplet diameter of the aqueous phase of less than 5 microns. The result of the micropercolation test showed no separation of brine after injection of the emulsion. The rheological test showed no significant change in viscosity with the number of cycles, indicating high Shear stress stability.

Example 6 A water-in-oil emulsion stabilized with solids was formed using Crude Oil # 2 and Phosphated Asphalt (Kew 97-149®, a product of Imperial Oil Corporation, Canada) as the solid particles. The oil and solids were added together and the mixture was stirred at 50 ° C for J8 hours before the addition of sulfuric acid, as described above. The resulting water-in-oil emulsion showed the diameter of the droplet of the aqueous phase of less than 5 microns using light microscopy. The micropercolation test revealed no separation of brine. The rheological test indicated high stability of the emulsion, that is, the viscosity remained essentially constant as a function of the number of cycles.

Oil pretreatment with Lignosulfonate Additive Another method of oil pretreatment to improve its capacity, to form a water-in-oil emulsion stabilized with solids, stable, is to add a lignosulfonate additive to the oil before preparing the emulsion. The salts of lignosulfonic acid (for example, sodium, potassium, ammonium, calcium, etc.) are of nature active on the surface, and when added to an oil / water mixture will tend to be added to the oil / water interface. This effect increases the interfacial activity of the oil and improves the stability of the emulsion.

Preparation of the Stabilized Emulsion with Solids Treated with Lignosulfonate To practice this embodiment of the invention, a lignosulfonate additive is added to the oil, before or after the addition of the solid particles, but before emulsification. For the sake of simplicity and clarity, this specification will refer to the addition of a type of lignosulfonate additive to the oil. However, it should be understood that combinations of different lignosulfonate additives may be used to practice this embodiment of the invention. The lignosulfonate additive is added to a treatment ratio of between 200 to 20,000 ppm based on the weight of the oil, more preferably from 500 to 5000 ppm, and even more preferably from 500 to 1000 ppm, for 5 to 10 minutes a 25 to 40 ° C. The solid particles are added either before or after the addition of the lignosulfonate additive, followed by the addition of water in small aliquots or continuous water. The mixture is then subjected to mixing with shear at a rate of between 1000 to 12000 rpm, for a sufficient time to disperse the water as small droplets in the continuous oil phase. It is preferred to have a water concentration in the water-in-oil emulsion of 40 to 80%, more preferably 50 to 65% and much more preferably 60%. The temperature of the emulsion will rise above room temperature (25 ° C) during mixing. The control of the temperature of the emulsion during mixing is not critical, however, higher temperatures of between 40 ° C and 75 ° C are preferred. Both oil-soluble and water-soluble lignosulfonate additives can be used to improve the stability of the water-in-oil emulsion stabilized with solids. Non-limiting examples of water-soluble lignosulfonates are the sulfonate salts of monovalent cations, similar to sodium, potassium and ammonium. Non-limiting examples of oil-soluble lignosulfonates are the sulfonate salts of divalent cations, similar to calcium, magnesium and iron. It is preferred to use water soluble additives because of the ease of delivery and the use of water as the supply solvent. The preferred water-soluble lignosulfonate additive is ammonium lignosulfonate. In addition, mixtures of lignosulfonate salts can be used to produce the same or an improved effect. A hydrophobic silica, Aerosil® R 972, was found to be an effective solid for various types of oil. The invention has been demonstrated using Aerosil® R 972 at a treatment rate of 0.15% by weight, based on the weight of the oil. Other hydrophobic solids, similar to bentonite clays divided and wetted with oil, organophilic clays or carbonaceous asphaltenic solids, can also be used. Hydrophilic solid particles can also be used. The preferred treatment ratio for solids is 0.05 to 0.25% by weight, based on the weight of the oil. It is possible to pre-treat the oil with the lignosulfonate additive and then add the solids particulate materials. However, it is preferred to add the solid particulates to the oil and then add the lignosulfonate additive to the mixture. Optionally, the solid particulate materials can first be treated with the lignosulfonate additive and the treated solids can be added to the oil before the addition of water and mixing. As mentioned above, lignosulfonate additives, either water-soluble or oil-soluble, can be used to pre-treat the solids. The choice of what type of lignosulfonate additive to use depends on the type of solid that is treated. Generally, a hydrophobic solid is treated with a water-soluble lignosulfonate additive and a hydrophilic solid with an oil-soluble lignosulfonate additive. Such a choice would make possible the modification of the surface of the solids to optimize the hydrophilic and hydrophobic character. While pretreatment with lignosulfonate of the full amount of oil necessary to make a desired emulsion is feasible by this embodiment of the invention, it is also possible to pretreat a side stream or master batch of oil and subsequently mix the side stream with a main stream of oil before the addition of water and emulsification. This main stream of oil is preferably untreated raw oil, however, it can be any oil, including oil that has been treated to improve its ability to form a stable emulsion or that has been treated to optimize its rheology. If the side stream method is used, the amounts of solids and lignosulfonate additives necessary for the treatment of the side stream are scaled accordingly to obtain the desired amounts in the resulting emulsion. This embodiment of the invention can be used in conjunction with the method of pretreating the oil with dilute mineral or organic acid, to further improve the surface active properties in the oil. The addition of dilute acid may occur before or after the addition of lignosulfonate, since the order of addition of the acid and the lignosulfonate additive are not critical. Without However, the addition of acid and the addition of lignosulfonate must occur before emulsification. If the addition of lignosu] fonate is combined with the acid addition, the pH of the emulsion can be adjusted by adding a calculated amount of a weak base, as previously described, to raise the pH to the desired level, preferably to a pH between 5-7.

Examples: This invention has been demonstrated in the Crude Oil # 4 and Ci udo Oil # 6, since these crude oils do not form stable, solid-stable emulsions, using the method described in U.S. Patent Nos. 5,927,404, 5, &- 5,243 and 5,910,467. The Crude Oil # 6 is a crude oil of low viscosity. In a typical experiment, the lignosulfonate additive was added to the oil at a treatment ratio of 0.05 to 0.5% by weight, based on the weight of the oil, and mixed for 10 minutes using a Silverson® homogenizer at approximately 1000 to 12,000 rpm. . The ammonium lignosulfonate and calcium lignosulfonate were used as the lignosulfonate additives in these examples. Solid particles, either bentonite or hydrophilic silica, were added in 0.15% by weight, based on the weight of the oil, followed by the additional mixer. Then water was added to the mixture in small aliquots with additional mixing to provide a water-in-oil emulsion stabilized with solids. The emulsions prepared by the above methods were subjected to the following tests: 1. Rack stability at 25 ° C for 48 hours 2. Optical microscopy and NMR for determination of water droplet size / size distribution 3. Stability in the centrifuge (See Appendix-1) 4. Stability of the emulsion: flow through a sand pack (details of the micropercolation test procedure are given in Appendix-1) 5. Rheology of the emulsion using a Brookfield viscometer ® (cone (# 51) and plate configuration) at 60 ° C in a range of shear from 1.92 to 384 sec "1.

Example-1: Crude Oil # 4 The results of the test for Crude Oil # 4 pretreated with ammonium lignosulfonate or calcium lignosulfonate are presented in Table 10. An emulsion drained in oil 60/40 stabilized with solids was formed using the pretreatment with lignosulfonate at 0.5% by weight and a hydrophobic silica, Aerosil® R 972, at 0.15% by weight.

"-" "-" ^ As indicated in Table 10, pretreatment with lignosulfonate improved the stability of the emulsions as demonstrated by the separation of brine 'decreased (% bbo) under the micropercolation test, compared to the emulsion of water in oil stabilized with solids, untreated. TABLE 10 Influence of 0.5% by weight of ammonium lignosulfonate and calcium lignosulfonate in a water-in-oil emulsion with crude solids prepared from Crude Oil # 4 Viscosity Stability Additive of Lignosulfonate Micropercolation Emulsion (cP) a ( % bbo) 60 ° C None 38 2743 Ammonium Lignosulfonate 2620 Calcium Lignosulfonate 2620 Example-2: Crude Oil # 6 A 60/40 water-in-oil emulsion stabilized with solids was made with Crude Oil # 6 and 0.15% on hydrophobic silica, Aerosil® R 972. Pretreatment with lignosulfonate was not used. The emulsion was unstable with 40% water separation under the test of 02 micropercolation. The viscosity of the emulsion at 60 ° C and 9.6 sec "1 was 983 cP, however, when the same 60/40 water-in-oil emulsion was prepared using the # 6 Crude Oil pretreated with 0.5 cc. ammonium lignosulfonate, the emulsion stability was improved, with water separation reduced to 17% The viscosity of the emulsion at 60 ° C and 9.6 sec "1 increased slightly to 1064 cP.

Example-3: 50/50 Crude Oil Blend using Crude Oil # 4 and Crude Oil # 6 A 60/40 water-in-oil emulsion stabilized with solids, untreated, was prepared using a mixture of 50% Crude Oil # 4 and 50% Crude Oil # 6. The solid particles were comprised of a hydrophobic silica, Aerosil® R 972, at 0.15% by weight, based on the weight of the oil mixture. The emulsion stabilized with untreated solids had a water separation of 32%. The viscosity for this emulsion at 60 ° C and 9.6 sec "1 was 2129 cP The same emulsion was prepared with a mixture of Crude Oil # 4 / Crude Oil # 6 50/50, which was pretreated with 0.5% by weight of ammonium lignosulfonate The emulsion stabilized with solids, treated with lignosulfonate, showed improved stability as demonstrated by the decrease in the separation of brine to 5%. The viscosity of the emulsion treated at 60 ° C and 9.6 sec "1 remained at 2129 cP The data indicate that the treatment improved the stability of the emulsion without change in viscosity.

Pretreatment of the Oil by Thermal Oxidation with Air Another form of pretreatment that can be used to increase the stability of a water-in-oil emulsion stabilized with solids is to heat-treat the oil, either before or after the addition of solid particles, in the presence of air or oxygen. The heat treatment of the oil or a mixture of oil and solid particles in the presence of air or oxygen causes several reactions to occur in the oil and on the surface of the solid particles. (1) The aromatic components of the oil having benzylic carbons and those having fused rings which are oxidizable including, but not limited to, naphthelene and anthracene, are oxidized to the corresponding products of acids, ketones or quinone. The organosulfur and nitrogen compounds present are oxidized to sulfoxides and nitrogen oxides. Oxygenated compounds are more active on the surface than the aromatic components themselves and are strongly adsorbed on the surface of the solid particles to improve the stability of the water-in-oil emulsion stabilized with solids. (2) If naphthenic acids are present as salts of divalent cations, similar to calcium, oxidation with air can convert these salts to naphthenic acids and the corresponding metal oxide, for example, calcium oxide. The free naphthenic acid can be adsorbed on the surface of the solids and also improve the stability of the water-in-oil emulsion stabilized with solids. (3) The heat treatment with an air purge dehydrates the solid particles and thus modifies the surface of the solids to improve their interaction with the oil components active on the surface (pre-existing in the oil or generated from oxidation with air).

Preparation of a Stabilized Emulsion with Solids Using Oxidized Air with Thermal Air To prepare a water-in-oil emulsion stabilized with sclidos using this method, the oil is thermally treated for a sufficient time and temperature in the presence of an air or oxygen purge, to make possible the physical and chemical modifications to oil and solid particles. Preferably, the oil is heated to temperatures between 110-180 ° C for 15 minutes to 6 hours, under an air or oxygen purge at a preferred ratio of 20 to 100 standard cubic feet per barrel per hour (se - .bbl / hr). The solid particles may be added before, during or after the oxidation step with thermal air, but must be added before emulsification. However, it is preferred to add the acids to the oil and then thermally oxidize the mixture with air. The solid particles may be hydrophilic or hydrophobic in nature. The fumed silica, sold under the trade name of Aerosil® R 972 or Aerosil® 130 (Products of DeGussa Corp.) was found to be the effective solids for a number of oils. Other solid particles similar to bentonite arcs, split bentonite clays, kaolinite clays, organophilic clays or asphaltenic solids can also be used. carbonaceous The amount of solid particles added to the oil can vary in the range of about 1% to 90% based on the weight of the oil, preferably 0.01 to 20% by weight and more preferably 0.05 to 5.0% by weight. At the highest concentrations, the mixture of solids and oil will be a thick slurry with a high solids content. Bentonite clays, such as those mined in Wyoming, Ga, or numerous other locations around the world, are particularly suitable as stabilizers for water-in-oil emulsions. As they are extracted, these clays naturally consist of aggregates of particles that can be dispersed in water and broken by shear in units that have average particle sizes of 2 microns or less. However, each of these particles is a laminate unit containing about 100 layers of 1 nm thick fundamental silicate joined together by inclusions of atoms, such as calcium, in the layers. By exchanging atoms, such as calcium, sodium or lithium (which are larger and have strong attractions for water molecules in fresh water), and then by exposing the bentonite to fresh water, the bentonite can be broken into 1 nm layers of individual thickness, called fundamental particles. The chemistry of this delamination process is well known to those skilled in the art of clay chemistry. The result of this delamination process is a gel consisting of split bentonite clay. The preferred solid is split or delaminated bentonite clay which is obtained as a gel from the delamination process described above. The amount of gel added to the oil before the oxidation step with thermal air can vary in the range of 5 to 95% gel based on the weight of the oil, preferably 40 to 60%. The weight of the bentonite clay solids in the gel can vary from 1 to 301, based on the weight of the water. When you use bentonite clay gel as the particles solid, and is added to the oil and subjected to the oxidation step with thermal air, the water is expelled from the reaction vessel as steam. The reaction must be carried out until at least 80% of the water is expelled, preferably until 95% of the water is expelled, and even more preferably until 100% of the water is expelled. It is preferred to oxidize a side stream or masterbatch of a mixture of oil and solids and subsequently mix the side stream with a main stream of oil prior to the addition of water and mixing, i.e., prior to emulsification. This main stream of oil is preferably untreated raw oil, however, it can be any oil, including oil that has been treated to improve its ability to form a stable emulsion or that has been treated to optimize its rheology. If the untreated raw oil is the. mainstream, the preferred mixing ratio is 0.5 to 5% oxidized oil in the main stream of untreated oil, more preferably from 0.1 to 2.5%. After the step of oxidation with air and the addition of solid particles, water is added in small aliquots or continuously and the mixture is subjected to mixing with shear at 1000 to 12000 rpm for a sufficient time to disperse the water as small droplets in the continuous oil phase. The temperature of the emulsion will rise above the ambient temperature of 25 ° C during mixing. Controlling the temperature of the emulsion during mixing is not critical. However, higher temperatures are preferred between 40 to 70 ° C. Catalysts can be used to improve the oxidation reaction. Finely divided catalysts similar to iron, manganese or nickel, or their oil-soluble metal salts can be used to catalyze the oxidation rates and effect selectivity in the oxidation products. Such oxidation promoting catalysts and techniques for using such catalysts are well known in the art, and will therefore not be discussed herein. Oxidation can be conducted at elevated pressures to further catalyze the reaction rate and achieve product selectivity, however, oxidation at ambient pressures is preferred. The oxidized oil can be further treated with dilute mineral or organic acid to provide additional stability to the water-in-oil emulsion stabilized with solids. The preferred proportion of acid treatment is between 8 and 30,000 ppm. If the acid pretreatment step is used, the pH of the resulting emulsion can be adjusted to a preferred range of to 7 by adding a calculated amount of weak base to the emulsion. However, pH adjustment is optional since in some cases it is desirable to inject an acidic emulsion and allow the formation of the deposit to regulate the emulsion to the alkalinity of the deposit. Ammonium hydroxide is the preferred base for pH adjustment. Stronger bases similar to sodium hydroxide, potassium hydroxide and calcium oxide have a negative effect on the stability of the emulsion. One possible explanation for this effect is that the strong bases tend to invert the emulsion, that is, convert the water-in-oil emulsion to an oil-in-water emulsion. Such investment is undesirable for the purposes of this invention. In addition to increasing the stability of the water-in-oil emulsion stabilized with solids, treatment with dilute acid decreases the viscosity of the emulsion. This reduced viscosity helps to improve the injection capacity of the emulsion, and may also be beneficial in other aspects in EOR processes, for example, to match the rheology of the emulsion with that of the underground oil to be recovered when the emulsion as a driving fluid. Gas can also be added to further decrease the viscosity of the emulsion.

Examples: In a typical experiment, 200 g of oil were placed in a Parr® autoclave or in three-neck glass flasks and oxidized at temperatures of 150 to 160 ° C for 2 to 6 hours, with a continuous air purge at 80 ° C. 100 scf / bbl / hour. The oxidized oil was then mixed at various ratios with untreated oil or other thermally oxidized oils with air, as detailed in the specific examples in the following. A hydrophobic silica, Aerosil® R 972, was added to the oxidized oil mixture at 0.05 to 0.15% by weight, based on the weight of the oil. After the addition of solids, the product was mixed using a Silverson® homogenizer. Then water was added in small aliquots with mixing to produce the water-in-oil emulsion stabilized with solids. For the preferred case of oxidation with thermal air of a mixture of oil and split bentonite gel, the oil and the first are mixed to form a slurry. The oxygen gas or air is purged in the reactor and the temperature raised to between 150 ° C and 170 ° C. The water is expelled as steam and can be condensed externally for recovery and reuse. For the optional case of adding acid to the oxidized areite, 10 ppm of sulfuric acid was added to the oxidized sample and mixed for 10 minutes at 40 ° C. The addition of solids and water with mixing was followed as is described earlier. The emulsions prepared by the above methods were subjected to the following tests: 1. Stability in rack at 25 ° C for 48 hours 2. Optical microscopy and NMR for the determination of water droplet size / size distribution 3. Stability in the centrifuge (described in Appendix-1) 4. Stability of the emulsion: flow through a sand pad (details of the micropercolation test procedure are given in Appendix-1) 5. Rheology of the emulsion using a Brookfield® viscometer (cone (# 51) and plate configuration) at 60 ° C in a shear rate of 1.92 to 384 sec "1.

Example-1: Crude Oil # 4 untreated Mixed with Crude Oil # 4 Oxidized with Air Aerosil® R 972 was added to a treatment ratio of 0.15 '. in weight to Crude Oil # 4 untreated, followed by water and € -1 mixed to form a water emulsion in crude oil stabilized with solids, 60/40. This emulsion, although stable on the shelf, was unstable in the tests in the microcentrifuge and micropercolation. The dispersed water droplets varied in size from 2 to 40 microns in diameter, and a water separation of 54% was observed in the micropercolation test described in Appendix-1, using Berea sand. The viscosity of the emulsion at 60 ° C and 9.6 sec "1 was 3644 cP Another batch of Crude Oil # 4 was thermally oxidized with air according to the procedure described above The Crude Oil # 4 thermally oxidized with air mixed with the untreated Crude Oil # 4 at 2.5% by weight of oil treated in the untreated oil The supply of the Crude Oil # 4 thermally oxidized with air was in toluene in a ratio of 1: 2. A hydrophobic silica, Aerosil® R 972, was added to the mixture at 0.15% by weight, based on the weight of the mixed oil.The addition of water and mixing were followed to make an emulsion stabilized with water solids in crude oil, stabilized with solids , 60/40 The droplet size distribution, determined with NMR, indicates that 90% of the water droplets were smaller than 2 microns in diameter.The stability of the emulsion was improved over that of the emulsion stabilized with oil solids. Raw # 4 not treated or, "as demonstrated by a 10% water separation reduction in the Berea micropercolation test. The viscosity of the emulsion was 2452 cP at 60 ° C and 10 sec. "1. the viscosity profiles were repeated on a shear cycle of 1 hour. Ethane gas was added to reduce the viscosity of the emulsion of water in oil stabilized with solids, thermally oxidized with air. The viscosity of the resulting emulsion was decreased from 2452 to 390 cP at 60 ° C with ethane saturation at 400 psi. The emulsion was stable to the addition of ethane and to the shear stress at 10 sec "1, during the duration of the experiment of 5 days.

Example 2: Mixes of Crude Oil # 4 Oxidized and Crude Oil # 6 of Low Viscosity In this experiment, Crude Oil # 4 and a crude oil of low viscosity, Crude Oil # 6, were mixed to several ratios. A hydrophobic solid, Aerosil® R 972, was added at 0.15% by weight solids to the mixed oil, along with 10 ppm sulfuric acid and mixed for 30 minutes. Then water was added in small aliquots and mixed to provide a mixed water-in-oil emulsion 60/40. The results are shown in Table 11. As observed from the data, the increase in the proportion of the low viscosity Crude Oil # 6 decreases the viscosity of the water emulsion in mixed oil 60/40 of 3644 cP (measured at 60 ° C and 9.6 sec_1 \ to 983 cP However, the stabilities of the emulsions are poor as is demonstrated by the separation of water from 30 to 40% in the micropercolation test using Berea sand.

- TABLE 11 Ratio of Mixed% bbo Viscosity, cP of Crude Oil # 4/60 ° C, 96s-1 Crude Oil # 6 100/0 38 3644 75/25 34 2621 • 50/50 32 2129 25/75 41 1638 0/100 40 983 Table 12 shows the effectiveness of thermal oxidation with oil air, before emulsification, to improve the stability of the resulting emulsion. Oil Crude # 6 was thermally oxidized with air by the previously described method and then mixed with untreated Crude Oil # 4 to result in a mixture of 75% Crude Oil # 4 untreated at 25% Crude Oil # 6 thermally oxidized with air. A hydrophobic solid, Aerosil® R 972, was added to the mixture together with 10 ppm sulfuric acid and mixed for 30 minutes. Then water was added in small aliquots and mixed to provide a mixed water-in-oil emulsion 60/40. The results shown in Table 12 illustrates the effectiveness of this method, as indicated by the micropercolation test using Berea sand. Table 12 Oils Brine Separation Viscosity, cP (% bbo) 60 ° C, 96s ~ x 75% Crude Oil # 4 34 2621 25% Crude Oil # 6 75% of Crude Oil # 4 25% of Crude Oil # 6 16 2620 Thermally Oxidized with Air In the addition of 25% of Crude Oil # 6. thermally oxidized with air to untreated Crude Oil # 4, the stability of the emulsion doubles as demonstrated by the decrease in percent brine separation from 34% to 16%. %.

Example-3: Solids Stabilized Emulsion Prepared Using Crude Oil # 4 and Bentonite Gel Divided A mixture of 70 grams (g) of Crude Oil # 4 and 30 g of divided bentonite gel (providing an oil to gel ratio of 70) : 30, and with a concentration of solids of bentonite of 3.5% by weight in the gel) was oxidized with air at a temperature of 160 ° C for 4 hours with an air purge of 80 scf / bbl / hour. Approximately 25 g of water were expelled from the reactor. The product of the reaction was used to prepare a 60/40 water-in-oil emulsion, stabilized with solids. The product oxidized with air was mixed with untreated crude oil, with a resulting mixture consisting of 2.4% by weight of the product oxidized with air, to 98.6% of the untreated crude oil. The resultant 60/40 water-in-oil emulsion showed a brine separation of 12% in the micropercolation stability test. The emulsion was stable to the addition of ethane gas at 400 psi. A mixture of 30 g of Crude Oil # 4 and 70 g of divided bentonite gel (oil to gel ratio of 30:70) was subjected to oxidation with thermal air used as described above. The water was expelled from the reactor and the resulting product was an oily solid. A 60/40 water-in-oil emulsion stabilized with solids was made using the oily solid product. The amount of oily solid used was 0.1%, based on the weight of the untreated crude oil. The resulting emulsion showed a brine separation of 20% in the micropercolation stability test. The dispersed water droplets were less than 4 miera in diameter.

Pretreatment of the Oil by Thermal Treatment in an Environment Ineite Another method of pretreating an oil to improve its capacity to form a water-in-oil emulsion stabilized with solids, stable, is to heat treat the oil in an inert environment before emulsification . This embodiment has the added benefit of reducing the viscosity of the water-in-oil emulsion stabilized with solids. The heat treatment can: a) generate asphaltenic solids that by themselves and / or in combination with externally added solids provide improved stability to water-in-oil emulsions stabilized with solids, b) reduce the viscosity of the crude oil that translates into lower viscosity of the emulsion, water-in-oil emulsions stabilized with solids; and c) retaining or degrading naphthenic acids.

Preparation of Water Emulsions in Oil Stabilized with Solids with Thermally Treated Oil To improve the physical and chemical properties of an oil for the formation of an emulsion stabilized with solids, stable, the oil can be heat treated in an inert environment for a sufficient time and at a sufficient temperature and pressure before emulsification. It is preferred to thermally treat the oil when heating at temperatures between 250 ° C-450 ° C to 30 to 300 pounds / square inch (psi) for 0.5 to 6 hours. The heat treatment may occur in an inert atmosphere without gas purge, or alternatively in the continuous presence of an inert purge gas. For the preferred method of thermal pretreatment without purge gas, the oil is initially bled off with an inert gas similar to nitrogen for 30 minutes and the autoclave sealed and heated to the required temperature. For the alternative mode of thermally pretreating with a continuous inert gas purge, an inert gas, similar to argon, is bubbled into the reactor at 200 to 450 standard cubic feet / barrel / hour (scf / bbl / hour) during the full course of the heat treatment. This process is preferred, if a larger reduction in viscosity is desired. The latter process will result in a larger percent destruction of surface active naphthenic acids and is less preferred for the purposes of preparing a stable emulsion. The severity of the treatment is suitably selected to produce the reduction of optimal viscosity and naphthenic acid retention. This severity of treatment may vary from one oil to another, but it is within the ranges described. After the heat treatment, the solids are added, followed by water and mixing to form the water-in-oil emulsion stabilized with solids. The addition of solids to the oil before thermal pretreatment is also within the scope of the present invention. However, in the latter case, the potential to soil the process equipment needs to be resolved, and the heat treatment conditions optimized to minimize equipment fouling. The addition of water is done in small aliquots or continuously and the mixture is subjected to mixing with shear, preferably between 1000 to 12000 rpm, for a sufficient time to disperse the water as small droplets in the continuous oil phase. It is preferred to have a water concentration, in the water-in-oil emulsion, of 40 to 80%, more preferably 50 to 65%, and much more preferably 60%. The temperature of the emulsion will rise above room temperature (25 ° C) during mixing. Controlling the temperature of the emulsion during mixing is not critical. However, higher temperatures are preferred between 40 ° C to 75 ° C. With respect to solids, solid particles they are preferred to be hydrophobic in nature. The fumed silica, sold under the trade name Aerosil® R 972 (product of DeGussa Corp.), was found to be effective for a number of different oils. Other solids similar to bentonite clays divided and wetted with oil, kaolinite clays, organophilic clays or carbonaceous asphaltenic solids can also be used. The preferred concentration of solids to the oil is in the range of 0.05 to 0.25% by weight. It is preferred to heat treat a side stream of oil at a high level of severity and then mix the side stream with a main stream of oil, before the addition of solids, water and mixing to form the emulsion. This main stream of oil is preferably untreated raw oil, however, it can be any oil, including oil that has been treated to improve its ability to form a stable emulsion or that has been treated to optimize its rheology. To further stabilize the solid stabilized emulsion, made with thermally treated oil, it is anticipated that it is particularly useful to add from 0.1 to 1.0% by weight of a lignosulfonate additive to the oil, prior to emulsification. This method of improving the stability of a solid-stabilized emulsion, that is, the addition of a lignosulfonate additive, is described above.

YES It is also possible to add dilute acid to the oil before emulsification, which will further improve the stability of the emulsion and reduce the viscosity of the emulsion. This addition of dilute acid is also described herein. The method of heat treating the oil prior to emulsification has the added benefit of lowering the viscosity of the stabilized emulsion with solids, compared to an emulsion stabilized with solids, made with untreated oil. This ability to manipulate the viscosity of the emulsion allows the user to optimally match the rheological characteristics of the emulsion with those of the oil to be recovered, specifically for the particular type of EOR method used. Gas can also be added to further decrease the viscosity of the emulsion. Yet another method for reducing the viscosity of a thermally treated solid stabilized emulsion is to age the emulsion. The thermally treated, solid stabilized emulsion can be aged by simply allowing the emulsion to stand at room temperature or at an elevated temperature for a sufficient period of time. The viscosity of the emulsion can be reduced by more than 50% when using this method. The aging process can be accelerated by centrifugation, repeated centrifugation preference, which will produce a similar reduction in the thermally treated viscosity of the thermally stabilized, solid emulsion. The centrifugation is preferably conducted at temperatures between 35 ° C and 80 ° C for 15 minutes to 2 hours at 500 to 10,000 rpm.

Examples: In a typical experiment, 200 g of oil was placed in a PARR autoclave and heated to temperatures of 150 to 450 ° C for 0.5 to 6 hours, at pressures ranging from 30 to 280 psi. The thermal pretreatment occurred either in an inert atmosphere without purge gas, or alternatively in the continuous presence of a purge gas. For the thermal pre-treatment without purge gas, the oil was initially purged with an inert gas similar to nitrogen, for 30 minutes and the autoclave was sealed and heated to the required temperature. For thermal pretreatment with a continuous inert purge, an inert gas similar to argon was bubbled into the reactor at 200 to 450 scf / bbl / hour during the entire course of the heat treatment. A hydrophobic silica, Aerosil® R 972, was then added to the heat-treated oil. Mixing using a Silverson® homogenizer followed the addition of solids. Finally, water was added to the oil and solid particles in small aliquots and mixed to provide an emulsion of water in oil stabilized with solids. The thermal pre-treatment method was demonstrated in three levels of severity, which impacted the following oil properties: (1) total acid number (TAN), (2) amount of insolubles in n-heptane, (3) equivalence of toluene ( measurement of solubility of thermally generated asphaltenes) and (4) viscosity. Emulsions prepared by thermally treated oil were subjected to the following tests: 1. Stability in rack at 25 ° C for 48 hours 2. Optical microscopy and NMR for the determination of water droplet size / size distribution 3. Stability in the centrifuge (as described in Appendix-1) 4. Stability of the emulsion: flow through a sand pack (details of the micropercolation test procedure are given in Appendix-1) 5. Rheology of the emulsion using a Brookfield® viscometer (cone (# 51) and plate configuration) at 35 or 60 ° C in a shear rate of 1.92 to 384 sec "1.

Example 1 A 60/40 water-in-oil emulsion was prepared using Crude Oil # 2 without any heat treatment, but with the addition of 0.15% by weight of hydrophobic silica (Aerosil® R 972). This emulsion, although stable on the shelf, was unstable in the tests in the centrifuge and in the micropercolation. The dispersed water droplets varied in size from 0.4 to 80 microns in diameter.

Example-2 Crude Oil # 2 was thermally treated at 360 ° C for 6 hours at 280 psi in an inert environment, using a sudden preflux of nitrogen. The viscosity of the resulting oil at 35 ° C and 9.6 sec "1 was decreased from 643 centipoise (cP) to 328 cP, the TAN was reduced from 6.6 to 3.9, the toluene equivalence increased from 14 to 31, while the insoluble in n-heptane they remained unchanged at 2.7% Solid particles, 0.15% by weight of Aerosil® R 972, were added to the thermally treated # 2 Crude Oil, followed by water and mixing to form a water-in-oil emulsion 60 / 40 stabilized with solids, as previously described.The resultant solid stabilized emulsion had a viscosity of 5734 cP at 35 ° C and 9.6 sec "1, which represented a 63% reduction in emulsion viscosity, compared to an emulsion stabilized with solids untreated, made with the untreated Crude Oil # 2 and 0.15% by weight of Aerosil® R 972. The water droplet size, determined with NMR, of the emulsion stabilized with solids, treated with heat, indicates a distribution Reduced water droplets in the size range of 2 to 10 microns in diameter. The emulsion was stable to flow, since no separation of water was observed in the micropercolation tests described in Appendix-1. The pH of the emulsion was approximately 6.2.

Example-3 Heat treatment of Crude Oil # 2 at 350 ° C for 2 hours at 90 psi in an inert environment resulted in a treated oil whose viscosity at 35 ° C and 9.6 sec "1 was decreased from 643 (cP ) at 328 cP TAN was reduced from 6.6 to 5.1, the toluene equivalence increased from 14 to 25, while insoluble in n-heptane remained unchanged at 2.7%, adding 0.15% by weight of Aerosil® R 972 to the thermally treated oil, followed by water and mixing, as previously described, provided a water-in-oil emulsion 60/40 stabilized with solids, stable.The NMR revealed a distribution of water droplets in the size range from 2 to 14 microns in diameter, a water separation of 14% was observed in the test micropercolation sand packing and no water separation in the test in the microcentrifuge. The pH of the emulsion was 6.2. The viscosity of the emulsion at 35 ° C and 9.6 sec "1 was 7373 cP, which represents a viscosity reduction of more than half, when compared with the emulsion, stabilized with solids, similar, prepared from the Crude Oil # 2 , which has been pretreated with diluted acid using the method described in the above.

Example-4 A 60/40 water-in-oil emulsion was prepared with another crude oil, Crude Oil # 4, without any thermal pre-treatment, but with the addition of 0.15% Aerosil® R 972. Crude Oil # 4 does not form emulsions stabilized with solids, stable, by the method described in U.S. Patent Nos. 5,927,404, 5,855,243 and 5,910,467. The physical properties for the Crude Oil # 4 are contained in Table 2. This emulsion, although stable on the shelf, was unstable in the tests in the centrifuge and in the micropercolation. The dispersed water droplets varied in size from 2 to 40 microns in diameter and a water separation of 54% was observed in the micropercolation test, described in Appendix-1, using Berea sand. The viscosity of the emulsion at 60 ° C and 9.6 sec "1 was 3644 cP.

General Test for the Increase in Oil Surface Activity The increase in oil surface activity due to pretreatment can be measured by determining the decrease in interfacial tension between oil and water. The interfacial tensions were determined by the standard slope drop technique at 25 ° C. The results for the untreated Crude Oil # 4 and the Pretreated Crude Oil # 4 are given in the following. Note that the results of interfacial tension for Crude Oil # 4 treated with solid particles and sulfonation, could not be measured using the standard slope drop technique.

TABLE 13 Measurement of Intertential Tension Oil Interfacial Tension dynes / cm Crude Oil # 4 not treated 32.3 Crude Oil # 4 + solid particles (solid) 32.6 Crude Oil # 4 + acid pretreatment + solids 15.8 Crude Oil # 4 + lignosulfonate + solids 12.5 Solids = 0.15% by weight of Aerosil® R 972 Lignosulfonate = 0.1% by weight of ammonium lignosulfonate Pretreatment with acid = 8000 ppm of sulfuric acid The present invention has been described in relation to its preferred embodiments. However, persons skilled in the art will recognize that many modifications, alterations and variations to the invention are possible without departing from the true scope of the invention. Accordingly, all such modifications, alterations and variations will be considered to be included in this invention, as defined by the appended claims.

Appendix-1: Micropercolation Test for Stability of Flow Emulsion Through Porous Media The observation that emulsions that are unstable will form two separate macroscopic phases, one oil / emulsion phase and one water phase, is considered In order to find out the stability of an emulsion in flow through porous media in a convenient, rapid test. A volume of emulsion that passes completely through the porous media, therefore can be centrifuged to form two distinct phases, whose volumes can be used as a measurement of the stability of the emulsion - the larger the proportion of water or water originally in the emulsion, which forms a phase distinct, clear, after the step and the centrifugation, the emulsion is more unstable. A convenient parameter for measuring stability, therefore, is the "brine separation" or "bbo", defined as the fraction of the water or brine that is in the emulsion, which forms the separate separated aqueous phase. Since it is a proportion, the bbo is smaller in size and varies between one (maximally unstable) and zero (maximally stable). The brine separation is measured under a well-defined set of conditions. A commercially available special frit microcentrifuge tube, which is comprised of two parts, is used as the container for the experiment. The bottom part is a tube that traps any fluid that flows from the upper tube. The upper part is similar to the usual polypropylene microcentrifuge tube, except that the bottom is a frit that is too small to contain grains of sand again, but allows the easy flow of fluid. In addition, the tubes arrive supplied with covers to each part, one of which also serves as a support that allows the upper part to be easily weighed and manipulated while it is vertical. They are available from Princeton Separations, Inc., Adelphia NJ and are sold under the name "CENTRI-SEP COLUMNS". A heated centrifuge is used to supply the pressure, to make the fluid flow emulsion through a piece of sand placed in the upper tube. This was supplied by Robinson, Inc., (Tulsa, OK) Model 620. The temperature is not adjustable, but stabilizes at 72 ° C under the conditions of the applicants. The top speed is approximately 2400 revolutions per minute (RPM) and the radius for sand packing is 8 centimeters (cm), which gives a centrifugal force of 520 g. All weights are measured to the nearest milligram. The columns come supplied with a small supply of silica gel, already heavy in the tube. This is discarded, and the weights of both sections noted. Approximately 0.2 grams (g) of sand are weighed on top and 0.2 ± 0.01 g of oil are added to the top. The typical sands used for this experiment are Berean or Ottawa sands. The sand that is used in this test can be varied according to the particular purpose. For simplicity, untreated, unscreened Ottawa sand, supplied by VWR Scientific Products, can be used. This gives an "indulgent" system, convenient, because the sand particles are rather large and free of clay. Alternatively, a fraction passing through a 100 Tyler mesh can be used, but it is retained by a 150 mesh, and another fraction passing through the 150 Tyler mesh, mixed in a ratio of ten to one, respectively. The tube is Weighed again, then centrifuged for one minute at full speed in the heated centrifuge. The bottom tube is discarded and the top is weighed again, which gives the amount of sand and oil that remains on top. The sand is now in a state wetted with oil, with air and oil in the pore space. Now, 0.18 ± 0.02 g of emulsion are placed in the upper part of the wetted sand, and the upper part is weighed again. A bottom tube is weighed and placed under this tube to trap the effluent during centrifugation. A separate bottom tube is filled with 0.2 to 0.5 g of emulsion only. This serves as a control to determine if the centrifugation of the emulsion, without being passed through the sand wetted with oil, causes the brine to separate from the emulsion. This step is known as the microcentrifuge test and is also an indicator of the stability of the emulsion. Both tubes are then centrifuged for an indicated time (15 to 45 minutes) depending on the viscosity of the oil and the speed of the centrifuge. The object in adjusting the duration of time is to obtain a point where at least 75% of the emulsion arrives in the bottom tube after passing through the sand. If it is smaller than what appears, the assembly is centrifuged during a additional time (s). After spinning, the weight of the top and bottom pieces are again recorded. If the emulsion is unstable, a clear water phase will be visible at the bottom of the tube, below a black, opaque emulsion / oil phase. The volume of water in the bottom receptacle is then measured by pulling it up in a precision disposable capillary pipette (100-200 microliters) equipped with a plunger. These are supplied by Drummond Scientific Co. (under the name "Wiretroll II"). The length of the water column is measured and converted to water mass through a calibration curve suitable for the capillary. The water separation can then be calculated from these measurements and knowledge of the weight fraction of the water in the original emulsion.

Claims

CLAIMS 1. A method for improving the stability of a water-in-oil emulsion stabilized with solids, the method characterized in that it comprises the step of pre-treating at least a portion of the oil before emulsification, the pre-treatment step comprising at least one of the steps of adding diluted acid to the oil, adding a lignosulfonate to the oil, sulfonating the oil, heat treating the oil in an inert environment and thermally oxidizing the oil.
2. A method for recovering hydrocarbons from an underground formation, the method characterized in that it comprises the steps of: (a) preparing a water-in-oil emulsion stabilized with solids, by (1) pre-treating at least a portion of the oil before the emulsification, the pretreatment step comprising at least one of the steps of adding dilute acid to the oil, adding a lignosulfonate to the oil, sulfonating the oil, heat treating the oil in an inert environment and thermally oxidizing the oil, (2) Add solid particles to the oil before emulsification and (3) add water and mix until the emulsion of water in oil stabilized with solids is formed; (b) inject the emulsion of water in oil stabilized with solids, in the underground formation and (c) recover the hydrocarbons from the underground formation.
3. The method according to claim 2, characterized in that the water-in-oil emulsion stabilized with solids is used as a driving fluid to displace the hydrocarbons in the underground formation.
4. The method according to claim 2, characterized in that the water-in-oil emulsion stabilized with solids is used as a barrier fluid to divert the flow of hydrocarbons in the underground formation.
The method according to claim 1 or claim 2, characterized in that the pretreatment step comprises adding diluted acid to at least a portion of the oil before emulsification, the diluted acid selected from the group consisting of at least a mineral acid, at least one organic acid, mixtures of at least two mineral acids, mixtures of at least two organic acids, and mixtures of at least one mineral acid and at least one organic acid.
6. The method according to claim 5, characterized in that the acid is added to the oil in a proportion of about 8 parts per million to about 30,000 parts per million.
The method according to claim 5, characterized in that the method further comprises the steps of determining the pH of the water-in-oil emulsion after the emulsification and if necessary, adjusting the pH so that it is in the range from about 5.0 to about 7.0.
The method according to claim 7, characterized in that the pH of the water-in-oil emulsion is adjusted by adding ammonium hydroxide to the emulsion.
The method according to claim 1 or claim 2, characterized in that the pretreatment step comprises sulfonating at least a portion of the oil prior to emulsification.
10. The method of compliance with the claim 9, characterized in that the sulfonation step of at least a portion of the oil comprises the addition of at least one sulfonation agent.
11. The method according to claim 10, characterized in that the sulfonation agent is acidic sulfuric.
The method according to claim 10, characterized in that the sulfonation agent is added to the oil at a treatment ratio of about 0.5% by weight to about 5% by weight.
The method according to claim 1 or claim 2, characterized in that the pretreatment step comprises adding a lignosulfonate additive to at least a portion of the oil before emulsification.
14. The method according to claim 13, characterized in that the lignosulfonate additive is added to the oil in a proportion of between about 500 parts per million to about 5000 parts per million.
15. The method according to claim 13, characterized in that the lignosulfonate additive is oil soluble.
The method according to claim 13, characterized in that the lignosulfonate additive is soluble in water.
The method according to claim 1 or claim 2, characterized in that the pretreatment step comprises thermally oxidizing at least a portion of the oil prior to emulsification.
18. The method according to claim 17, characterized in that the thermal oxidation step is carried out at a temperature between about 110 ° C and about 180 ° C.
19. The method according to the claim 17, characterized in that the step of thermal oxidation is improved by the addition of a catalyst.
The method according to claim 1 or claim 2, characterized in that the pretreatment step comprises heat treating at least a portion of the oil in an inert environment prior to emulsification.
21. The method according to claim 20, characterized in that the heat treatment step is carried out at a temperature in the range of between about 250 ° C and about 450 ° C.
22. The method according to claim 20, characterized in that the heat treatment step is carried out at a pressure in the range of between about 30 psi and about 300 psi.
23. The method according to claim 20, the method characterized in that it further comprises the step of adding dilute acid to the oil before emulsification, the dilute acid selected from the group consisting of at least one mineral acid, at least one organic acid, mixtures of at least two mineral acids, mixtures of at least two organic acids, and mixtures of at least one mineral acid and at least one organic acid.
24. The method of compliance with the claim 20, the method characterized in that it also comprises the step of adding a lignosulfonate additive to the oil before emulsification.
25. The method according to claim 20, characterized in that the step of heat treating the oil in an inert environment reduces the viscosity of the water-in-oil emulsion stabilized with solids.
26. The method according to claim 20, the method characterized in that it further comprises the step of aging the emulsion of water in oil stabilized with solids after emulsification, whereby the viscosity of the emulsion is reduced.
27. The method of compliance with the claim 26, characterized in that the aging step of the emulsion comprises centrifuging the emulsion at approximately 500 rpm at about 10,000 rpm for about 15 minutes to about 2 hours.
28. The method of compliance with the claim 27, characterized in that the centrifugation step of the emulsion is repeated.
29. The method according to claim 2, characterized in that the solid particles are hydrophobic solid particles.
30. The method according to claim 2, characterized in that the step of adding solid particles to the oil occurs after the pretreatment step.
31. The method according to claim 2, characterized in that the step of adding solid particles to the oil occurs before the pretreatment step.
32. The method of compliance with the claim 2, characterized in that the solid particles comprise at least one of functionalized asphalts, non-functionalized asphalts, bentonite clays, bentonite clay gel, kaolinite clays, organophilic clays, carbonaceous asphaltenic solids, phyllosilicates, lignin, lignite, coal , gilsonite, silica, dolamite, metalloids, layered oxides and phyllosilicates of quaternary onium exchange.
33. The method according to claim 2, characterized in that the lignosulfonate additive is combined with hydrophilic solid particles.
34. The method according to claim 2, characterized in that the thermally oxidized oil is combined with hydrophilic solid particles.
35. The method of compliance with the claim 2, characterized in that the solid particles are combined with a lignosulfonate additive, and then the combination is added to the oil before emulsification.
36. The method according to claim 2, characterized in that the solid particles are added as a gel, comprised of solid particles and water.
37. The method according to claim 36, characterized in that the solid particles comprise about 1% by weight to about 30% by weight of the gel, based on the weight of the water.
38. The method according to claim 36, characterized in that the gel is added to the oil in a treatment range of about 5% by weight to about 95% by weight of the gel to the oil.
39. The method according to claim 2, characterized in that the solid particles are added at a treatment ratio of about 0.05% by weight to about 5% by weight.
40. A water-in-oil emulsion stabilized with solids for use in the recovery of hydrocarbons from an underground formation, the emulsion characterized in that it comprises: (a) oil, wherein at least a portion of the oil is pretreated by at least one of the steps of adding diluted acid to the oil, adding a lignosulfonate additive to the oil, sulfonating the oil, heat treating the oil in an inert environment and thermally oxidizing the oil; (b) water droplets suspended in the oil and (c) solid particles that are insoluble in the oil and water at the conditions of the underground formation. 10