WO2010148204A2 - Particle stabilized emulsions for extraction of hydrocarbons from oil sands and oil shale - Google Patents

Abstract

Particle-stabilized emulsions, of the sort which can utilize liquid carbon dioxide and/or supercritical carbon dioxide as a continuous or a dispersed phase, for hydrocarbon extraction.

Description

Particle Stabilized Emulsions for Extraction of Hydrocarbons from Oil Sands and Oil Shale

[0001] This application claims priority benefit from Application Serial No. 61/268,875, filed June 17, 2009, the entirety of which is incorporated herein by reference.

Background of the Invention

[0002] Oil sands, also known as tar sands, and oil shales are large deposits of energy rich bitumen or kerogen found immobilized in sand or rock strata at numerous locations around the world. The most notable oil sand reserves are located in Alberta, Canada, and Venezuela. The largest oil shale deposits are in North America, but the Middle East, Australia and Europe (e.g. Estonia) all have significant deposits. Bitumen and kerogen are high carbon content materials produced as a result of fossilization of primeval fauna and flora. In order to use such hydrocarbons as energy sources and feed stocks for oil refineries, initial extraction from the mineral matter (sand and shale) is necessary.

[0003] Current methods of hydrocarbon extraction from oil sands and oil shales use mainly ex situ methods in which the sand or shale deposits are excavated and processed in overland facilities by thermal or chemical treatment processes. Such methods are typically quite energy intensive, reducing overall net gain. Furthermore, large quantities of water are consumed, invariably in areas where water resources are limited. As another consideration, extraction agents are typically specialty chemicals, some of them toxic to human health and the environment. Altogether, the removal of the "overburden" covering the oil sand or oil shale deposits causes deep scars to the pristine environment where such deposits are located. Furthermore, the disposal of the residue after the extraction process causes deleterious environmental problems, considering that the residue still contains significant amounts of the original bitumen (tar) and kerogen in the excavated mineral matter, plus the addition of potential toxic chemical agents. To illustrate the residue disposal problem, oil sands and oil shales contain only up to 15% of bitumen or kerogen, thus, 85% or more of the excavated treated sand or shale needs to be safely disposed of. Therefore, ex situ extraction methods, in addition to being energy and cost intensive, elicit considerable public and political opposition.

[0004] Accordingly, there remains an on-going search in the art for a method to enhance recovery /extraction of oil sand and oil shale deposits, to better utilize the benefits and advantages associated with such available hydrocarbon resources.

Summary of the Invention

[0005] In light of the foregoing, it is an object of the present invention to provide one or more methods and/or systems for hydrocarbon recovery from oil sand and oil shale deposits, thereby overcoming various deficiencies and shortcomings of the prior art, including those outlined above. It will be understood by those skilled in the art that one or more aspects of this invention can meet certain objectives, while one or more other aspects can meet certain other objectives. Each objective may not apply equally, in all its respects, to every aspect of this invention. As such, the following objects can be viewed in the alternative with respect to any one aspect of this invention.

[0006] It can be an object of this invention to provide a method for hydrocarbon recovery from oil sand and oil shale deposits, with less environmental impact as compared to processes of the prior art.

[0007] It can be another object of the present invention, alone or in conjunction with one or more objectives, to provide an approach to hydrocarbon recovery exhibiting greater efficiencies and cost benefits, as compared to the prior art.

[0008] Other objects, features, benefits and advantages of the present invention will be apparent from this summary and the following descriptions of certain embodiments, and will be readily apparent to those skilled in the art having knowledge of various hydrocarbon recovery processes and production techniques. Such objects, features, benefits and advantages will be apparent from the above as taken into conjunction with the accompanying examples, data, figures and all reasonable inferences to be drawn therefrom. [0009] In part, the present invention can be directed to a primary method of subterranean hydrocarbon recovery. Such a method can comprise providing a subterranean formation comprising a hydrocarbon component, such a component as can be selected from a tar, an oil and/or bitumen and kerogen precursors thereof; contacting the material content of such a subterranean formation with a fluid medium comprising an emulsion comprising a liquid carbon dioxide and/or supercritical carbon dioxide component, an aqueous component and a particulate component selected from hydrophilic components and/or combinations thereof and hydrophobic components and/or combinations thereof, such particulate component(s) in an amount sufficient for at least partial emulsification, such contact for a time and/or at a pressure at least partially sufficient to displace the hydrocarbon component from the formation; and recovering the hydrocarbon component and, optionally, at least a portion of the fluid medium and/or emulsion.

[001O]In certain embodiments, the fluid medium can comprise an emulsion comprising a dispersed phase comprising an aqueous component, a continuous phase comprising one or more such carbon dioxide components and one or more hydrophobic particulate components, such hydrophobic particles can include but are not limited to those described elsewhere herein or as would be otherwise known to those skilled in the art made aware of this invention.

[0011]In certain other embodiments, the fluid medium can comprise an emulsion comprising a dispersed phase comprising one or more such carbon dioxide components, a continuous phase comprising an aqueous component and one or more hydrophilic particulate components. Such hydrophilic particulate components can include but are not limited to those described elsewhere herein or as would otherwise be known skilled in the art skilled made aware of this invention.

[0012] In certain embodiments, the subterranean formation can comprise but is not limited to a oil sand and/or oil shale deposit. In such embodiments, a hydrocarbon component can be selected from a tar and an oil and bitumen and/or kerogen precursors thererof. Regardless, in certain such embodiments, the material content of such a formation can be excavated and contact with a fluid medium of the sort discussed above can be ex situ and/or above ground with regard to the subterranean formation. In certain other embodiments, the material content can be contacted in situ and/or under ground with respect to the subterranean formation. Whether such contact is ex- or in-situ, such a fluid medium can comprise an emulsion comprising a liquid carbon dioxide and/or supercritical carbon dioxide component, an aqueous component and a particulate component selected from hydrophilic components and/or combination thereof and hydrophobic components and/or combinations thereof.

[0013] In certain such non-limiting embodiments, such a fluid medium can comprise an emulsion comprising a dispersed phase comprising an aqueous component, a continuous phase comprising one or more such carbon dioxide components and one or more hydrophobic particulate components. In certain other embodiments, such a fluid medium can comprise an emulsion comprising a dispersed phase comprising one or more such carbon dioxide components, a continuous phase comprising an aqueous component and one or more hydrophilic particulate components.

[0014] Without regard to any particular hydrocarbon or subterranean formation, in certain non-limiting embodiments, a carbon dioxide component of an emulsion used in conjunction with this invention, whether part of a continuous phase or dispersed phase, can be present in an amount greater than about 1 wt. % of the emulsion.

[0015] Regardless, particles utilized in conjunction with such an emulsion can be dimensioned from about 5 nanometers or less to about 100 μm or more. With correlation to a dispersed phase of such an emulsion, particulate dimension can be about 5x to about 50x smaller than a dimensional aspect of any such dispersed phase. These and various other non-limiting emulsion parameters are discussed elsewhere herein or as would be understood by those skilled in the art made aware of this invention. Such parameters can be varied, limited only by the physical properties and/or functional effect desired of a particular emulsion, in the context of a particular subterranean formation and/or hydrocarbon recovery.

[0016] Regardless of whether such fluid medium contact is in situ or ex situ, such a method can comprise contact of said formation with an organic component at least partially immiscible with an aqueous component of such a fluid medium. In certain embodiments, without limitation, such an organic compound can be selected from C₂ to about C₂₀ hydrocarbon compounds, C₂ to about C₄o ether compounds and combinations of such hydrocarbon and/or ether compounds, such compounds of the sort illustrated below or as would otherwise be understood by those skilled in the art made aware of this invention. Regardless, such contact can be prior to either such in situ or ex situ contact and can be considered as an optional pre-treatment aspect or component of the present methodologies.

[0017] In part, the present invention can also be directed to a method of using a particulate-stabilized emulsion for hydrocarbon extraction from oil sand/oil shale. Such a method can comprise providing a oil sand, oil shale or a related formation comprising a hydrocarbon; contacting the material content of such a formation, whether in situ or ex situ, with a fluid medium comprising an emulsion comprising an aqueous component, a component at least partially immiscible with such an aqueous component and a particulate component selected from hydrophilic components and/or combinations thereof and hydrophobic components and/or combinations thereof, such a particulate component(s) in an amount sufficient for at least partial emulsification, such contact for a time and/or at a pressure at least partially sufficient to displace the hydrocarbon deposit from the formation; and recovering the hydrocarbon component and at least a portion of the emulsion.

[0018] In certain embodiments, a hydrocarbon component can be selected from a tar, an oil, a bitumen, a kerogen and/or combinations thereof. Regardless, such a fluid medium can comprise an emulsion comprising a dispersed phase comprising an aqueous component, a continuous phase comprising one or more components at least partially immiscible with such an aqueous component and one or more hydrophobic particulate components. As illustrated elsewhere herein, such a continuous phase can comprise a liquid carbon dioxide component, a supercritical carbon dioxide component, an organic component at least partially immiscible with an aqueous component and/or combinations thereof. With regard to such an organic component, whether alone or in combination with a carbon dioxide component, such an organic component can, without limitation, be selected from about C₂ to about C₂o hydrocarbons, from about C₂ to about C₄₀ ethers and from combinations thereof. Regardless, such a dispersed phase can comprise water, water-miscible components and combinations thereof. Such hydrophobic particulate components can be selected from those described elsewhere herein or as would otherwise be understood by those skilled in the art made aware of this invention.

[0019] Likewise, without regard to hydrocarbon component, such a fluid medium can comprise an emulsion comprising a continuous phase comprising an aqueous component, a dispersed phase comprising one or more components at least partially immiscible with such an aqueous component and one or more hydrophilic particulate components. As illustrated elsewhere herein, such a continuous phase can comprise an aqueous component comprising water, water-miscible components and combinations thereof. Such water-miscible components can, without limitation, be selected from Ci to about C₆ alcohols, Ci to about C₆ ketones, C₂ to about C₆ glycols, such components as can comprise one or more ionic and/or non-ionic components and/or solutes therein. Regardless, such a dispersed phase can comprise a liquid carbon dioxide component, a supercritical carbon dioxide component, an organic component at least partially immiscible with such an aqueous component and combinations thereof. Such hydrophilic particulate components can be selected from those described elsewhere herein or as would otherwise be understood by those skilled in the art made aware of this invention.

[0020] Without regard to any particular dispersed or continuous phase, hydrophobic particulate components can include but are not limited to coal particles, carbon black particles, petrocoke particles, Teflon^R particles, latex particles, polymer bead particles, protein particles, modified cellulose particles, chitosan particles, clay particles, and various other hydrophobic particles known to those skilled in the art, whether naturally-available or prepared by grinding, pulverizing, crystallizing, chemical synthesis, chemical coating and/or surface modification, pyrolysis or petroleum refining. Likewise, hydrophilic particulate components can include, but are not limited to carbonate mineral particles, silicate mineral particles, clay mineral particles, latex particles, polymer bead particles, protein particles, cellulosic particles, modified cellulose particles, chitin particles, chitosan particles, iron particles, iron oxide particles, cadmium selenide particles and various other hydrophilic particles known to those skilled in the art, whether prepared by grinding, pulverizing, crystallizing, chemical coating and/or surface modification or chemical synthesis.

[0021] Whether such a method is effected in situ or ex situ with respect to a particular formation, in certain non-limiting embodiments, such an emulsion can comprise one or more carbon dioxide components. In certain such embodiments, a carbon dioxide component, whether part of a continuous phase or dispersed phase, can be present in an amount greater than about 1 wt. % of the emulsion. Regardless, particulates utilized in conjunction with such an emulsion—whether hydrophobic or hydrophilic— can be dimensioned from about 5 nanometers or less to about 100 μm or more. Without limitation, nanometer-dimensioned particulates, i.e., nanoparticles, can be used effectively in the context of in situ contact with an oil sand/oil shale formation. With correlation to a dispersed phase of such an emulsion, particulate dimension can be about 5 x to about 50 x smaller than a dimensional aspect of any such dispersed phase. These and various other non-limiting emulsion parameters are discussed elsewhere herein or as would be understood by those skilled in the art made aware of this invention. Such parameters can be varied, limited only by the physical properties and/or functional effect desired of a particular emulsion, in the context of a particular subterranean formation and/or hydrocarbon recovery.

[0022] With respect to either the methods and emulsions of the present invention, the steps and components thereof can suitably comprise, consist of, or consist essentially of any of the steps or components disclosed herein. Each such method or step and emulsion or component thereof is distinguishable, characteristically or functionally contrasted and can be practiced in conjunction with the present invention separate and apart from another. Accordingly, it should also be understood that inventive methods and/or emulsions, as illustratively disclosed herein, can be practiced or utilized in the absence of any one component or step which may or may not be disclosed, referenced or inferred herein, the absence of which may or may not be specifically disclosed, referenced or inferred herein. Brief Description of the Drawings

[0023] Non-limiting embodiments of the present invention can be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In the figures:

[0024] FIG. 1 shows a schematic diagram of a particle stabilized emulsion according to one embodiment of the invention;

[0025] FIG. 2 shows droplets of water in a dodecane continuous phase stabilized by carbon black particles according to another embodiment of the invention;

[0026] FIG. 3 shows a schematic diagram of a high-pressure batch reactor for forming an emulsion according to another embodiment of the invention;

[0027] FIG. 4 shows a static mixer that can be used to form an emulsion according to another embodiment of the invention;

[0028] FIG. 5 shows a static mixer emulsion apparatus according to another embodiment of the invention;

[0029] FIG. 6 shows a system for recovering hydrocarbon from a subterranean formation according to another embodiment of the invention;

[003O]FIG. 7 shows one particular system for extracting hydrocarbon(s) from excavated oil sand/oil shale, according to another embodiment of the invention; and

[003 I]FIGS. 8A-8B illustrate oil extraction from sand, in accordance with one embodiment of this invention.

Detailed Description of Certain Embodiments.

[0032] Particle stabilized emulsions, and more specifically, particle stabilized emulsions for extraction of hydrocarbons from oil sand and/or oil shale formations are provided. While certain embodiments are discussed, it will be understood by those skilled in the art made aware of this invention that any such embodiment can independently pertain to the other or another such recovery process with corresponding revision or adaptation to a particular recovery, subterranean formation and/or particular end-use application, and can be applied thereto with comparable effect. One aspect of the invention relates to a process for recovering hydrocarbons from a subterranean formation by contacting or injecting an emulsion of aqueous liquid in liquid or supercritical carbon dioxide (aqueous-in-CO₂ [A/C] emulsion more commonly referred to as water-in-CO₂ emulsion [W/C]) stabilized by fine hydrophobic particles, with or into the formation. Another aspect of the invention relates to the process for recovering hydrocarbons from a subterranean formation by contacting or injecting an emulsion of liquid or supercritical carbon dioxide (CO₂-in- aqueous [C/A] emulsion more commonly referred to as CO₂-in-water emulsions [CAV]) stabilized by fine hydrophilic particles, with or into the formation.

[0033] As understood in the art, an "emulsion" is a stable mixture of at least two immiscible liquids. In general, mixing or dispersing immiscible liquids (one phase into the other) creates an unstable dispersion, which tends to separate back into two distinct phases. An emulsion is thus stabilized by the addition of an "emulsifying agent" which functions to reduce surface tension between at least two immiscible liquids. As used herein, an "emulsifying agent" defines a substance that, when combined with a first component defining a first phase, and a second component defining a second phase immiscible with the first phase, will facilitate assembly of a stable dispersion of the first and second phases.

[0034] Emulsions described herein may be stabilized by particles. The particles may orient themselves around the droplets according to their hydrophilicity or hydrophobicity. For instance, in A/C emulsions, a part of the hydrophobic particles may be wetted by the continuous carbon dioxide phase. Conversely, with C/A emulsions, the hydrophilic particles may be wetted by an aqueous continuous phase. The sheath of particles surrounding the droplets can prevent the coalescence of either carbon dioxide or water droplets into a continuous phase. In C/A emulsions, a larger part of the hydrophilic particles may be wetted by the continuous aqueous phase. As discussed below, the invention comprises many types of aqueous systems including water that is distilled, deionized, artesian, sea, waste, brine, oil- and gas-well associated or formation water. Similarly, the invention comprises all sorts of carbon dioxide, pure liquid and supercritical carbon dioxide, as well as complex mixtures and complex liquids, such as liquid hydrogen sulfide, organic and inorganic solvents freely miscible with carbon dioxide.

[0035] Without restriction to any one theory or mode of operation, upon injection into a subterranean formation, the emulsion disperses and disintegrates. If, for example, an A/C emulsion is injected, the liquid or supercritical carbon dioxide released therefrom can interact with the hydrocarbon component of the formation, dissolve at least a portion of it, at least partially reduces its viscosity and leave behind a slurry of fine particles in water. Further, as sand or other similar granules of the formation may be hydrophilic, there may be a preferential interaction with water rather than the hydrophobic hydrocarbon component, thereby allowing release of the tar, oil, bitumen and/or kerogen from the granules. As a result, water can displace the hydrocarbon component from the formation, mobilizing it for extraction and recovery.

[0036] Alternatively, a similar process can be envisioned with respect to a C/A emulsion system. While liquid carbon dioxide is very sparingly soluble in water (e.g., less than about 5 wt. % at low temperatures and relatively high pressures), up to about 50 wt. % or more of a carbon dioxide component can be dispersed in water with an emulsion system of the sort described herein, using hydrophilic particulate components. As discussed above, interaction of such a carbon dioxide (and/or organic) component with an oil sand/oil shale formation can be used to promote hydrocarbon extraction and recovery.

[0037] Accordingly, in one embodiment, a method of recovering or extracting a hydrocarbon from an oil sand and/or oil shale formation is provided. The method comprises introducing an emulsion comprising supercritical CO₂, an aqueous liquid, and an emulsifying agent comprising particles, into such formation or in contact with sand or shale excavation therefrom, and extracting hydrocarbon. In some cases, the emulsion comprises supercritical CO₂ and an aqueous liquid. For example, the emulsion may comprise a continuous phase comprising supercritical CO₂ and a dispersed phase comprising an aqueous liquid.

[0038] In another embodiment, such a method comprises contacting an emulsion comprising a continuous phase including greater than about 1% by weight of liquid CO₂, a dispersed phase comprising an aqueous liquid, and an emulsifying agent comprising particles, with oil sand and/or oil shale, and extracting hydrocarbon deposit(s) therefrom.

[0039] In another embodiment, a related system is provided. The system comprises supercritical CO₂, an aqueous liquid, and particles in fluid communication with an emulsion forming apparatus for forming an emulsion comprising the CO₂ component, aqueous liquid, and particles. The system also includes an apparatus for introducing the emulsion into a formation or contacting material excavated therefrom and an apparatus for recovering hydrocarbons. In one embodiment, the emulsion formed by such a system comprises a continuous phase comprising supercritical CO₂ and a dispersed phase comprising an aqueous liquid.

[0040] In another embodiment, a related system comprises liquid CO₂, an aqueous liquid, and particles in amounts sufficient to form an emulsion comprising a continuous phase including greater than about 1% by weight of liquid CO₂, a dispersed phase comprising an aqueous liquid, and an emulsifying agent comprising particles. The liquid CO₂, aqueous liquid, and particles may be in fluid communication with an emulsion forming apparatus. The system also includes an apparatus for introducing the emulsion into a formation or contacting an excavation thereof and an apparatus for recovering hydrocarbon. In one embodiment, the emulsion formed by such a system comprises a continuous phase comprising greater than about 1% by weight of liquid CO₂ and a dispersed phase comprising an aqueous liquid.

[0041 ] In another aspect, whether method or system-related, a series of emulsions are provided. In one embodiment, the emulsion comprises a plurality of droplets of an aqueous liquid suspended in a continuous phase comprising supercritical CO₂, and an emulsifying agent comprising particles. In another embodiment, an emulsion comprises a plurality of droplets of an aqueous liquid suspended in a continuous phase comprising greater than about 1% by weight of liquid CO₂, and an emulsifying agent comprising particles.

[0042] In another embodiment, a method of this invention comprises extracting a hydrocarbon component from a mixture. The method comprises introducing an emulsion comprising supercritical CO₂, an aqueous liquid, and an emulsifying agent comprising particles, into a mixture containing a hydrocarbon, and extracting the hydrocarbon from the mixture. In some cases, the emulsion comprises supercritical CO₂ and an aqueous liquid. For example, the emulsion may comprise a continuous phase comprising supercritical CO₂ and a dispersed phase comprising an aqueous liquid.

[0043] In another embodiment, such a method of extracting a hydrocarbon from a mixture comprises introducing an emulsion comprising a continuous phase including greater than about 1% by weight of liquid CO₂, a dispersed phase comprising an aqueous liquid, and an emulsifying agent comprising particles, into a mixture of components, and extracting a hydrocarbon component from the mixture. In one embodiment, the emulsion comprises a continuous phase comprising greater than about 1% by weight of liquid CO₂ and a dispersed phase comprising an aqueous liquid.

[0044] In another aspect, a related system for recovering a hydrocarbon component from a mixture is provided. In one embodiment, the system comprises supercritical CO₂, an aqueous liquid, and particles in fluid communication with an emulsion-forming apparatus for forming an emulsion comprising the supercritical CO₂, aqueous liquid, and particles. The system also includes an apparatus for introducing the emulsion into a mixture of components, and an apparatus for recovering a hydrocarbon component from the mixture. In some cases, the emulsion of such system comprises supercritical CO₂ and an aqueous liquid. For example, the emulsion may comprise a continuous phase comprising supercritical CO₂ and a dispersed phase comprising an aqueous liquid. [0045] In one embodiment, a related system for recovering a hydrocarbon component from a mixture comprises liquid CO₂, an aqueous liquid, and particles in amounts sufficient to form an emulsion comprising a continuous phase including greater than about 1% by weight of liquid CO₂. The system also includes a dispersed phase comprising an aqueous liquid, and an emulsifying agent comprising particles. The liquid CO₂, aqueous liquid, and particles are in fluid communication with an emulsion-forming apparatus, an apparatus for introducing the emulsion into a mixture of components, and an apparatus for recovering a hydrocarbon component from the mixture. In some cases, the emulsion comprises a continuous phase comprising greater than about 1% by weight of liquid CO₂ and a dispersed phase comprising an aqueous liquid.

[0046] As shown in the embodiment illustrated in FIG. 1, an emulsion 8 includes droplets 10 (also known as "globules") of a dispersed phase 14 (i.e., the isolated phase stabilized by an emulsifying agent). In some embodiments, the dispersed phase can comprise an aqueous liquid (e.g., water or aqueous solutions). In certain embodiments in which the dispersed phase comprises an aqueous liquid, a continuous phase 18 can comprise supercritical or liquid carbon dioxide (i.e., an AIC- type emulsion). Some emulsions may also include an oil or lipid component forming all, or portions, of a continuous phase (e.g., aqueous-in-oil [A/O] type emulsions). Examples of such emulsions are provided below. The droplets of the emulsion are stabilized by particles 22, which may include, for example, solid particles such as pulverized coal. The particles form a particle sheath at the interface of the two phases, preventing their coalescence into a bulk phase. Without limitation, such particle stabilized emulsions can be referred to or are commonly known as "Pickering emulsions".

[0047] While in some embodiments, liquid or supercritical CO₂ may form substantially all of the continuous phase of A/C emulsions, the invention is not so limited, and it should be understood that A/C emulsions described herein can have other compositions. For example, as described in more detail below, A/C emulsions can also include other fluids in the continuous phase in addition to liquid or supercritical CO₂ (e.g., to form a ternary mixture). In certain embodiments including A/C-type, the continuous phase, can include greater than about 1% by weight of liquid or supercritical CO₂. For example, in some cases, the continuous phase can include between about 1- about 20%, about 20- about 50%, or about 50-100% by weight of liquid or supercritical CO₂.

[0048] As used herein "droplet" means an isolated phase having any shape, for example cylindrical, spherical, ellipsoidal, tubular, irregular shapes, etc. Droplets may have an average cross-sectional dimension of greater than or equal to about 25 nm, greater than or equal to about 50 nm, greater than or equal to about 100 nm, greater than or equal to about 250 nm, greater than or equal to about 500 nm, greater than or equal to about 1 micron, greater than or equal to about 5 μm, greater than or equal to about 10 μm, greater than or equal to about 50 μm, greater than or equal to about 100 μm, greater than or equal to about 200 μm, greater than or equal to about 350 μm, greater than or equal to about 500 μm, greater than or equal to about 700 μm, greater than or equal to about 800 μm, or greater than or equal to about 900 μm. The droplet size of a particular emulsion may depend, at least in part, on the size and type of the emulsifying particles, inter-particle interactions (e.g., steric interactions), concentration and composition of the continuous and dispersed phases, as well as the rate of shearing/mixing when forming the emulsion, as described in more detail below.

[0049] In some embodiments, emulsions described herein have a CO₂ continuous phase and an aqueous dispersed phase. For example, in one embodiment, an emulsion comprises a plurality of droplets of an aqueous liquid (e.g., water and seawater) suspended in continuous phase comprising greater than 1% by weight of liquid CO₂, and an emulsifying agent comprising particles. For example, in some cases, the continuous phase can include between 1-20%, 20-50%, or 50-100% by weight of liquid CO₂. In some cases, the continuous phase consists essentially of liquid CO₂.

[0050] Whether or not expressly indicated, all numbers expressing component quantities, concentrations or proportions (e.g., weight percentages ratios and factors of ratios), dimensions, properties, reaction or process parameters or conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical values set forth in this specification and the attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as a limitation of application of the doctrine of equivalents to the scope of such claims, each numerical value should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[005 I]In certain embodiments, particle stabilized aqueous-in-oil (A/O) emulsions are contemplated. (Such emulsions are also known as water-in-oil [W/O] emulsions). As described below, an "oil" can include any liquid that is immiscible with an aqueous liquid such as water; that is, any liquid that, when admixed with an aqueous liquid, can form a two-phase mixture. In one embodiment, an emulsion may include a continuous phase comprising an oil (e.g., a hydrocarbon or fluorocarbon) and a dispersed phase comprising an aqueous liquid (e.g., water). Such emulsions may optionally comprise liquid or supercritical carbon dioxide with respect to a continuous phase thereof. An example of a particle stabilized aqueous-in-oil emulsion is shown in FIG. 2. In the illustrative embodiment of FIG. 2, emulsion 40 including droplets 42 of water in a dodecane continuous phase 44. The droplets are stabilized by carbon black particles 48. In this particular embodiment, the droplets have an average size of 10-20 μm.

[0052] The aqueous liquid of an emulsion can be any liquid miscible with water; that is, any liquid that, when admixed with water, can form a single-phase solution. In some cases, the aqueous liquid can comprise one or more additives, such as salts (e.g., salts of alkali and/or alkali earth metals). Non-limiting examples of aqueous phase materials include, for example, water (e.g., purified water, unpurified water, distilled water, deionized water, artesian water, seawater, ground water, well water, waste water, brackish water, brine, oil- and gas-well associated water, formation water, natural sources of water that may or may not contain dissolved salts or contaminants, etc.), methanol, ethanol, DMF (dimethylformamide), or DMSO (dimethyl sulfoxide). Those of ordinary skill in the art can choose appropriate aqueous liquid(s) for forming particle stabilized emulsions based on general knowledge of the art in combination with description provided herein.

[0053] The oil portion of an emulsion can be any liquid that is immiscible with an aqueous liquid such as water. In some cases, the oil may include one or more additives such as a surfactant. Two classes of oils that may be used in emulsions described herein include hydrocarbons and halocarbons (e.g., fluorocarbons). The emulsion can be stable at any suitable temperature depending on the particular application.

[0054] A hydrocarbon may include a linear, branched, cyclic, saturated, or unsaturated hydrocarbon. The hydrocarbon can optionally include at least one heteroatom (e.g., oxygen in the backbone of the compound to provide a corresponding ether). Non-limiting examples of hydrocarbons include methane, ethane (and, e.g., dimethyl ether), propane, butane, pentane, hexane, heptane, octane, nonane, decane, undodecane, dodecane, and the like and corresponding available ethers. Higher-order hydrocarbons such as Ci₀-C_2O hydrocarbons can also be used. In some cases, a continuous or dispersed phase of an emulsion can include mixtures of hydrocarbons of various chain lengths. The hydrocarbon may be, for example, a petroleum hydrocarbon. In some cases, hydrocarbons recovered from an oil sand/oil shale formation can be used in continuous phases of emulsions described herein. Regardless, use of such water immiscible solvents such as dimethyl ether, dodecane or similar such organic solvents, can facilitate hydrocarbon extraction from a particular formation. For instance, use of such components, whether in conjunction with a dispersed or continuous phase, can enable extraction at lower (e.g., atmospheric) pressures, thereby improving extraction efficiencies. Likewise, as discussed below, such organic components can be used with good effect for in situ extraction.

[0055] A fluorocarbon may include any fluorinated compound such as a linear, branched, cyclic, saturated, or unsaturated fluorinated hydrocarbon. The fluorocarbon can optionally include at least one heteroatom (e.g., in the backbone of the component). In some cases, the fluorocarbon compound may be highly fluorinated, i.e., greater than 50% of the hydrogen atoms of the component are replaced by fluorine atoms. In other cases, the fluorocarbon is perfluorinated. Halocarbons including, for example, bromine or chlorine atoms, are also contemplated.

[0056] In certain embodiments, emulsions described here include liquid or supercritical carbon dioxide in the continuous phases. Gaseous carbon dioxide can become liquid carbon dioxide when compressed or pressurized (e.g., above 5.1 atm). Supercritical carbon dioxide can form when the carbon dioxide is brought above its critical temperature (31.1° C) and pressure (78.3 atm). Supercritical carbon dioxide behaves like a gas with respect to viscosity, and can expand to fill its container like a gas, but behave like a liquid with respect to density. Additionally, liquid and supercritical carbon dioxide can diffuse through solids like a gas, and dissolve materials like a liquid, because of their properties such as low viscosity, high diffusion rate, and little or no surface tension. For example, the viscosity of supercritical carbon dioxide is typically in the range of 20 to 100 μPa-s, whereas typical liquids have viscosities of approximately 500 to 1000 μPa-s. Such properties make supercritical and liquid carbon dioxide useful for extraction processes.

[0057] The invention comprises all sorts of carbon dioxide, pure liquid and supercritical carbon dioxide, complex mixtures, complex liquids, as well as binary liquids, such as liquid hydrogen sulfide, organic and inorganic solvents freely miscible with carbon dioxide.

[0058] In embodiments comprising liquid or supercritical carbon dioxide as part of a continuous phase of an emulsion, it should be understood that other materials can form at least a portion of that phase. Likewise, continuous or dispersed phases described herein may include one or more of the following non-limiting examples of supercritical fluids: water, methane, ethane, propane, ethylene, propylene, methanol, ethanol and acetone. Additionally and/or alternatively, the continuous or dispersed phase can also include liquids such as liquid nitrogen, liquid oxygen, liquid hydrogen, liquid argon, liquid helium, or other cryogenic liquids (i.e., liquefied gases at very low temperatures). Particle stabilized emulsions comprising a cryogenic liquid or a supercritical fluid as a continuous or dispersed phase, and an aqueous liquid as a continuous or dispersed phase are also provided. [0059] Liquids forming continuous and dispersed phases may have a range of viscosities suitable for forming emulsions described herein. In some cases in which the continuous and/or dispersed phase comprises a supercritical or cryogenic liquid, for example, the viscosity of the liquid may be in the range of, e.g., between 10-200 μPa-s. For instance, in one embodiment, a continuous and/or dispersed phase consisting essentially of a supercritical or cryogenic liquid may have a viscosity in the above range. In another embodiment, a continuous and/or dispersed phase comprising a supercritical or cryogenic liquid (e.g., which may be dissolved in a liquid) may have a viscosity in the range of between 200-1,500 μPa-s. In yet another exemplary embodiment, a continuous and/or dispersed phase comprising a liquid, but which does not comprise a supercritical or cryogenic liquid therein, may have a viscosity in the range of between 200-1,500 μPa-s. It should be understood, however, that any suitable viscosity of a continuous and/or dispersed phase can be used to form emulsions described herein and that the invention is not limited in this respect.

[006O]In certain embodiments, the dispersed and/or continuous phase of an emulsion may include one or more additives such as organic substances, microbial components (e.g., bacteria), minerals, undissolved particles, various dissolved species, gases, solvents, salts, and the like. Accordingly, in some embodiments, emulsions described herein include ternary or higher mixtures.

[006I]In certain embodiments, emulsions described herein are stabilized at least in part by fine particles. Suitable particles include solid particles that are at least partially undissolved in the emulsion. The particles may be, for example, naturally occurring, synthetic, or modified. Particles can be held at the interface between the two phases of the emulsion by, e.g., van der Waals forces, hydrophobic/hydrophilic interactions, hydrogen bonding, ionic interactions, and the like.

[0062] The surface properties of the particles (e.g., wettability) determines, at least in part, use in conjunction with an aqueous-in-CO₂ emulsion, in the case of a mixture of carbon dioxide (e.g., supercritical or liquid carbon dioxide) and an aqueous liquid. Particles having some hydrophobic character (e.g., ground Teflon^®, activated carbon, carbon black, and pulverized coal) are preferentially wetted by the carbon dioxide phase; hence, they promote A/C-type emulsions. In some cases, the hydrophobic character of the particles is naturally occurring or inherent in the material. In other embodiments, however, particles can be treated by a process such as heating or coating, which can change the surface characteristics of the materials. For instance, particles can be partially, completely, or uniformly coated with a substance (e.g., a surfactant or polymer). Applicable surface properties of the particles can be measured by those of ordinary skill in the art by techniques such as contact angle measurements between, for example, particle, aqueous and carbon dioxide three-component systems. Numerous representative particulate materials are summarized, below, with respect to type, preparation and source.

[0063] Particles described herein may have a variety of shapes and sizes. For example, particles may be cylindrical, spherical, rectangular, triangular, ellipsoidal, tubular, rod-like, or irregularly shaped. Suitable sizes of the particles may depend on factors such as the particulate type of emulsion (e.g., a water-in-carbon dioxide emulsion), the components of the continuous and dispersed phases, and the size of the dispersed droplets in the medium. The size of the particles refers to the length of the shortest line (e.g., cross-sectional dimension) connecting two end points of the particle and passing through the geometric center of the particle. In some embodiments, the average size of the particles used to form an emulsion is less than 100 μm, less than 50 μm, less than 25 μm, less than 10 μm, less than 5 μm, less than 1 μm, less than 500 nm, less than 250 nm, less than 100 nm, less than 50 nm, less than 10 nm, or less than 5 nm.

[0064] In some instances, the average size of the particles used to form an emulsion is chosen, at least in part, by the desired size of the dispersed droplets of the emulsion. For instance, in some embodiments, very small particles may not be suitable for large droplets, as the particles may be dislodged from the surface of large droplets by Brownian motion. In other embodiments, large particles may not be suitable for small droplets, as the particles may not be able to pack onto small droplets. Accordingly, in some cases, the particle size is adjusted to the dispersed droplet diameter. In certain embodiments, the average size of the particles may be 5-50 times smaller than the average size of the dispersed droplets of the emulsion. For example, the average size of the particles may be at least 5, 15, 25, or 50 times smaller than the average size of the dispersed droplets of the emulsion. The ratio of particle size to droplet size may be, for example, between 1 : 10 and 1 :30 (e.g., between 1 : 10 and 1 :20 or between 1 :20 and 1 :30). Of course, other ratios of particle size to droplet size may also be used.

[0065] Particles may include elemental metals (e.g., gold, silver, copper), semi- metals and non-metals (e.g., antimony, bismuth, graphite, sulfur), and/or ceramics. In some instances, particles can include, but not limited to, oxides, sulfides, sulfates, carbonates, silicates.

[0066] Particles can also include, but not limited to, polymer particles (e.g., plastics) such as polycarbonates, polyethers, polyethylenes, polypropylenes, polyvinyl chloride, polystyrene, polyamides, polyacrylates, polymethacrylates, polytetrafluoroethylene (Teflon^R) and the like.

[0067] In one particular embodiment, particles from the following group of materials can be used: carbon black, petrocoke, Teflon^®, shale, surface-coated clays, silica and pulverized coal. It should be understood that the invention is not limited to the above mentioned particles, but any particle or group of particles that facilitates the generation of an A/C and/or C/ A emulsion as desired can be used in accordance with the invention.

[0068] In certain embodiments of the invention, an emulsion can be stabilized by both particles and a surfactant, which act as emulsifying agents to stabilize at least two immiscible phases. A variety of surfactants is known in the art and may include, for example, anionic, cationic, zwitterionic, and non-ionic species.

[0069] Those of ordinary skill in the art can also choose an appropriate emulsifying agent by, for example, choosing the components used to form the continuous and dispersed phases of the emulsion and knowing the surface properties (e.g., wettability) and/or likelihood of reactivity between the emulsifying agent and the two phases, and/or by a simple screening test. For example, if a water-in-carbon dioxide emulsion is desired, a suitable emulsifying agent (e.g., particles) may include one that is hydrophobic such that it can be wetted by the continuous carbon dioxide phase. One simple screening test may include mixing one set of components in a vial to form the emulsion and determining the stability of the emulsion. Either the material composition, quantities, and/or concentration of one component can then be varied while keeping the others constant, and the stability of this emulsion can then be measured. Other simple tests can be conducted by those of ordinary skill in the art.

[0070] Emulsions described herein are, according to some embodiments, stable for at least about 1 minute. Emulsions that are stable over time are useful because they allow for the time necessary to transport, place, and/or use the emulsion before coalescence or disintegration. For example, emulsions may be stable for more than 1 minute, 1 hour, 1 day, 1 week, 1 month, or 1 year. As used herein, a "stable emulsion" means that droplets of the emulsion do not coalesce, e.g., to form larger droplets, at a particular temperature and pressure resulting in two bulk phases with a meniscus between them. In one particular embodiment, an emulsion that can be used for hydrocarbon extraction from oil sand/oil shale is stable from the time of formation to the time of injection into or contact with the sand/shale.

[0071 ] Emulsions described herein can have any suitable ratio of continuous and dispersed phases. Typically, however, the volume of the continuous phase is greater than that of the dispersed phase. For example, the ratio of the volumes of the continuous phase to dispersed phase may be greater than or equal to 1 : 1 up to 20: 1 (e.g., between 1 : 1 and 5: 1, between 5:1 and 10: 1, or between 10: 1 and 20: 1). It should be understood, however, that any suitable ratio of volumes of continuous phase to dispersed phase can be used to form emulsions described herein and that the invention is not limited in this respect.

[0072] The amount of particles necessary for forming an emulsion may depend on one or more of the following parameters: particle size, droplet size, type of emulsion formed, shape of the particles (which, in turn, may effect inter-particle or steric interactions), concentration and composition of the continuous and dispersed phases, and physical parameters associated with forming the emulsion (e.g., shear force, temperature, and pressure). Accordingly, various amounts of particles relative to the amount of dispersed and/or continuous phase may be used to form emulsions described herein. In certain embodiments, the mass ratio of particle to carbon dioxide may be, for example, greater than or equal to 0.005: 1 up to 1.0: 1 (e.g., between 0.005: 1 and 0.2: 1, between 0.2:1 and 0.6: 1, or between 0.6: 1 and 1.0: 1).

[0073] In some embodiments, the amount of particles added to two immiscible phases of an emulsion can be greater than that which is necessary to form the emulsion, and a portion of the particles can accumulate, for example, at the bottom of a reactor. In addition, because not all particles are of uniform size and may, in fact, include a distribution of sizes (e.g., some may be too small to adhere to the interface of the continuous and dispersed phases, and some may be too big), higher mass ratios of particles to dispersed phase material may be used.

[0074] In some embodiments, the amount of particles necessary for emulsion formation can be estimated from a particle sheath model (e.g., a monolayer or multilayer sheath model). An example is given for liquid CO₂ droplets in an aqueous continuous phase and particles comprising CaCO₃. Taking a droplet diameter of 100 μm, a sheath thickness of 2 μm (corresponding to a monolayer of Hubercarb CaCO₃ Q6 particles with mean size 2 μm), a liquid CO₂ density at 15° C and 17 MPa of 0.93 g/cm³, and a CaCO₃ bulk density of 2.7, the mass ratio of CaCO₃/CO₂ is estimated at 0.2: 1. Because not all particles have a uniform size, different ratios of CaCO₃/CO₂ may be used. For example, 0.4: 1, that is, for every 1 kg of CO₂, 0.4 kg of pulverized limestone may be used as well as ratios down to 0.002:1.

[0075] Emulsions described herein may be formed using any suitable emulsification procedure known to those of ordinary skill in the art. In this regard, it will be appreciated that the emulsions can be formed using methods/systems such as micro fluidic systems (e.g., a micro fluidizer), ultrasound, high pressure homogenization, using a static mixer, shaking, stirring, spray processes, and membrane techniques. In certain embodiments, emulsions described herein are formed by shear forces. In the description herein concerning the use of appropriate methods of fabricating emulsions, those of ordinary skill in the art can select suitable materials, techniques, conditions (e.g., temperature and pressure) etc. based upon the particular application, general knowledge of the art and available reference materials concerning certain techniques for forming emulsions, in combination with the description herein.

[0076] In one particular embodiment, emulsions described herein are formed using a high-pressure batch reactor, as shown in FIG. 3. As shown in the embodiment illustrated in FIG. 3, high-pressure batch reactor 50 can be used to form an emulsion comprising water and liquid or supercritical carbon dioxide as the continuous or dispersed phases. The reactor includes source of water 54 in fluid communication with vertical batch reactor 58. Electrical pump 60 can transport water from the source to the reactor via pipe 62, and this process which can be controlled at least in part by check valve 64 and/or release valve 66. As illustrated, source of carbon dioxide 70 is also in fluid communication with the reactor via pipe 72. Introduction of carbon dioxide into the reactor can be controlled by manual piston screw pump 74, shut off valves 76 and 78, and relief valve 80. The pressures in the pipes can be measured by gauges 82 and 86. Once water and carbon dioxide are introduced into reactor 58, magnetic mixer assembly 88 can mix the components and form an emulsion. The temperature inside the reactor can be measured by thermal couple and panel meter 90. Particles can be introduced into the reactor via an opening (not shown) in the form of a slurry or particles alone. System 100, or a similar system, can be used to form a variety of emulsions including, but not limited to, CO₂-in-aqueous, aqueous-in-CO₂, aqueous-in-oil, and oil-in-aqueous emulsions.

[0077] In another embodiment, a microfluidizer is used to form an emulsion. The size and stability of the droplets produced by this method may vary depending on, for example, capillary tip diameter, fluid velocity, viscosity ratio of the continuous and dispersed phases, and interfacial tension of the two phases.

[0078] In another embodiment, a static mixer is used to form an emulsion. An example of a static mixer is illustrated in FIG. 4. As shown in the embodiment illustrated in FIG. 4, static mixer 92 is tubular and includes alternating helical mixing blades 96 with no moving parts. In some cases, the static mixer is a Kenics-type static mixer. The components of an emulsion (e.g., liquid or supercritical CO₂, particles, and an aqueous liquid) can be introduced at an up-stream portion 94 of the mixer, and an emulsion formed of the components can exit at a down-stream portion 98. A static mixer can be incorporated into a static mixer emulsion apparatus, e.g., as shown in FIG. 5. The size and stability of the droplets produced by a static mixer may vary depending on, for example, the pressure differential between the up- and down-stream portions of the static mixer, the length of the mixer, the number of baffles per unit length of the mixer, and other variables (e.g., temperature).

[0079] In some embodiments of the invention, emulsions described herein are used for extracting a component from a mixture of at least two components. The component to be extracted may be in the form of a solid (e.g., particles), a liquid (e.g., oil), or a gas (e.g., methane). In some cases, the component may include impurities and/or can include more than one phase (e.g., solid contaminants in a liquid). The at least two components of the mixture may be of the same phase (e.g., both solid, both liquid, or both gaseous) or may include different phases (e.g., a solid and a liquid, a solid and a gas, or a liquid and a gas).

[0080] FIG. 6 schematically illustrates a system and one or more associated methods that can be used to recover a hydrocarbon from a subterranean formation in situ, that is, underground without removing the overground burden. As shown in this illustrative embodiment, system and related method(s) 100 include particles 102, supercritical or liquid CO₂ 104 and aqueous liquid (e.g., water), which can be in fluid communication with emulsion forming apparatus 112 for forming, for example, aqueous-in-CO₂, or aqueous-in-oil emulsions. Once an appropriate emulsion is formed, the emulsion may flow to injection apparatus 118 (e.g., an injection well or pump), which may introduce the emulsion into well 123 in the direction of arrows 122.

[0081] Well 123 may be drilled from top layer 124 to bottom layer 125 of a subterranean formation, and the intermediate layer may include oil sand and/or oil shale deposits 126 containing mixtures of bitumen and/or kerogen components. Without limitation as to any one theory or mode of operation, when the emulsion is introduced into well 123, this produces areas of high pressure 127 and low pressure 129; as a result, the emulsion flows in the direction of arrows 128 from well 123 to well 130. Likewise, without limitation to any one theory or mode of operation, the carbon dioxide (or other oil) component, can dilute the hydrocarbon component, reduce its density and/or increase its mobility, thereby mobilizing the hydrocarbon component in the direction of arrows 128. The remaining slurry of fine particles in water pushes out the diluted hydrocarbon. Such a process appears to be aided by the fact that water has a greater affinity for hydrophilic sand particles, than for oil. As a result, the aqueous component of the emulsion is exchanged with the hydrocarbon component on the sand or shale of the formation. The hydrocarbon extracted from formation/deposits 126, along with portions of the continuous and/or dispersed phases of the emulsion, can flow in the directions of arrows 132 to receiver 142 (e.g., a producing well).

[0082] Regardless, as the resulting extracted mixture may include carbon dioxide, a hydrocarbon and water (e.g., in the case of a water-in-CO₂ emulsion being injected), separation of the components may be necessary or desired. A first separation process can include the use of separator 146, which may separate carbon dioxide from the hydrocarbon and water. The carbon dioxide, which may now be in the form of a gas, can be recovered in container 154. If desired, this carbon dioxide can be recycled by transporting it to compressor/condenser 158, which can compress and/or condense the carbon dioxide to form supercritical or liquid CO₂. This compressed carbon dioxide can act as, or be added to, source of carbon dioxide 104. [0083] Once separator 146 removes CO₂ from the extracted mixture, oil/gas and water can be transported to separator 164, which can separate water from the hydrocarbon component. Water separated from the mixture can be transported to container 168, and can act as, or be added to, source of water 108 used in forming the emulsion. Additionally and/or alternatively, at least a portion of the water can be transported to a water disposal well. The hydrocarbon separated from separator 164 can be transported to storage facility 174 for future use or consumption. In some embodiments, at least a portion of the oil can act as, or be added to, source of oil 109 used to form the emulsion.

[0084] Carbon dioxide 104 may be obtained commercially from sources such as natural CO₂ deposits, gas wells, CO₂ separated from natural gas wells, from separating CO₂ in the flue gas of fossil fuel combustion, from cement manufacturing, from fermentation, from combustion of carbonaceous fuels, and as a by-product of chemical processing where CO₂ is a major by-product. For example, CO₂ may be obtained as a by-product from steam-hydrocarbon reformers used in the production of ammonia, gasoline, and other chemicals.

[0085] In the future, large amounts of CO₂ may be obtained from a new generation of coal based power plants. The new plants may use the principle of integrated coal gasification combined cycle (IGCC) with CO₂ capture. In these plants, coal is gasified to produce a synthetic gas comprising a mixture of carbon monoxide (CO) and hydrogen (H₂). The CO is further reformed with steam to produce more H₂ and CO₂. The CO₂ is separated from H₂ by one of several known technologies, such as physical absorption, chemical absorption, or membrane separation. The H₂ is used for power generation in a combined cycle. The separated gaseous CO₂ is liquefied under pressure and may be sequestered in subterranean formations, called geologic sequestration. However, a part of the separated CO₂ may become available to form the particle stabilized emulsions to be used for oil sand and/or oil shale extraction as described in this invention.

[0086] As described above, at least a portion of carbon dioxide 104 may be recycled or recovered from the extraction process. Carbon dioxide may be treated by processes such as, for example, amine (MEA) treatment, adsorption processes, extractive distillation techniques, and membrane systems. Crude CO₂ (e.g., containing at least 90% CO₂) can be compressed in either two or three stages, cooled, purified, and condensed to the liquid phase by a compressor/condenser. The carbon dioxide can then be placed in an insulated storage vessel.

[0087] If CO₂ is imported to the oil sand/oil shale extraction site, it is most economical to transport the liquid carbon dioxide by pipeline. Alternatively, the carbon dioxide can be transported, for example, in high-pressure un-insulated steel cylinders, as a high-pressure liquid in insulated truck trailers or rail tank cars, or as dry ice in insulated boxes, trucks, or boxcars.

[0088] As described above, a variety of aqueous liquids can be used in emulsions described herein. In one embodiment, water from a well on site of the subterranean formation can be used. In other embodiments, well water, sea water, or other sources of water can be imported. In yet another embodiment, waste water from an oil refinement process may be used in forming emulsions described herein. Optionally, the water may be purified (e.g., filtered) to remove waste materials, contaminants, and the like, prior to formation of the emulsion.

[0089] In the embodiment illustrated in FIG. 6, particles 102, carbon dioxide 104, and aqueous liquid 108 (and/or oil) are shown as separate sources. However, in other embodiments, one or more materials can be premixed prior to forming an emulsion. For example, in one embodiment the particles are mixed with water to form a slurry prior to formation of an emulsion with carbon dioxide. In another embodiment, the particles are mixed with carbon dioxide to form a slurry prior to formation of an emulsion with another liquid. Other pre-mixtures of components can also be used. Regardless, such a methodology can be used for in situ extraction of hydrocarbons from a subterranean formation, e.g., oil sand or oil shale. A stabilized emulsion can be injected directly into the formation. When A/C emulsions are used, injection depth should be greater than about 200 meters. At shallower depths, vaporization of a liquid carbon dioxide component would disintegrate the emulsion. However, as discussed above, A/O emulsions using an alternative organic continuous phase (e.g., dimethyl ether, dodecane, etc.) can be used at effectively shallower depths. [0090] In certain embodiments, for in situ hydrocarbon extraction (e.g., petroleum) from oil sands or oil shale, as illustrated in FIG. 6, an organic component at least partially immiscible with an aqueous component, can be injected into the oil sand or oil shale formation prior to the injection of the particle stabilized emulsion of an aqueous fluid in carbon dioxide (AJC) or carbon dioxide in aqueous fluid (C/ A). The organic component can, without limitation, be selected from about C₂ to about C₂₀ hydrocarbons (e.g., straight-chain, branched and/or cyclic aliphatic and aromatic compounds - - whether substituted or unsubstituted, saturated or unsaturated), from about C₂ to about C₄o ethers and from combinations thereof. The prior injection of the said hydrocarbons or ethers can reside in the formation from about 1 hour, 1 week, 1 month to about 1 year before injection of the particle stabilized emulsion. This embodiment may lead to greater petroleum extraction efficiency compared to the co-injection of such an organic component together with or as a component of the AJC or C/A emulsion. This embodiment can be designated "soak&puff."

[0091 ] One particular system for recovering hydrocarbons ex situ from excavated oil sand and/or oil shale is shown in FIG. 7. In the illustrative embodiment shown in FIG. 7, an AJC or C/A emulsion can be contacted with excavated sand/shale. In the embodiment, a crusher 1 comminutes the oil sand or oil shale into beach sand size granules. The granules are fed via a hermetic feeder 2 into the contact tower 3. The contact tower must be kept under a sufficiently high pressure in order for the emulsion not to phase separate, and the liquid or supercritical CO₂ flash into a gas. The particle stabilized AJC or C/A emulsion is prepared in the particle-water mixer 4. The emulsion is injected into the contact tower via an emulsion forming apparatus 5, where it flows counter-current to the oil sand or oil shale granules. The residual tailings are discharged via a hermetic discharger 6 into a hopper 7, from whence they are transported away by truck or rail. The upward flowing emulsion extracts and dissolves the oil from the sand or shale granules and exits the top of the contact tower into a flash separator 9. where liquid or supercritical CO₂ is flashed into gaseous CO₂, which is liquefied in compressor 10 for eventual re-use. The extracted oil is stored in tank 11 for transport to the refinery. A liquid CO₂ tank 12 stores the necessary make- up liquid CO₂. The emulsifying particles are stored in hopper 13. The necessary water for forming the emulsion comes from municipal water, surface water (river, lake, ocean) or associated water from oil and natural gas production.

[0092] In certain embodiments, for ex situ hydrocarbon extraction (e.g., petroleum) from oil sands or oil shale, an organic component at least partially immiscible with an aqueous component, can be contacted with the excavated oil sand or oil shale in a contact tower, as illustrated in FIG. 7, prior to contact in the tower of the particle stabilized emulsion of an aqueous fluid in carbon dioxide (AJC) or carbon dioxide in aqueous fluid (C/ A). The organic component can, without limitation, be selected from about C₂ to about C₂₀ hydrocarbons (e.g., straight-chain, branched and/or cyclic, aliphatic and aromatic compounds - - whether substituted or unsubstituted, saturated or unsaturated), from about C₂ to about C₄o ethers and from combinations thereof. The prior contact of the said hydrocarbons or ethers can reside in the tower from about 1 minute, 1 hour, to about 1 week before contact in the tower of the particle stabilized emulsion. This embodiment may lead to greater petroleum extraction efficiency compared to the co-injection of such an organic component together with or as a component of the AJC or C/A emulsion. This embodiment can be designated "soak&extract."

[0093] Figure 7 is but one of the possible ex situ extraction processes, and is not limited to this invention. For example, a batch reactor can be used for the extraction procedure. It is understood by those skilled in the art of ex situ oil extraction that either a continuous process, such as illustrated in FIGURE 7, or a batch reactor, or a combination thereof, using the extraction process based on AJC or C/A emulsions is part and parcel of this invention. Furthermore, when using water-immiscible solvents such as dimethyl ether, dodecane or other such solvents of the sort described herein, conventional, atmospheric pressure vessels can be used with good effect for hydrocarbon extraction from oil sand or oil shale.

Examples of the Invention.

[0094] The following non-limiting examples and data illustrate various aspects and features relating to the methods and/or systems of the present invention, including the preparation of particle stabilized emulsions over range of physical properties and functional effects, as are available through the synthetic methodologies described herein. In comparison with the prior art, the present methods and/or systems provide results and data which are surprising, unexpected and contrary thereto. While the utility of this invention is illustrated through the use of several methods/systems and emulsions, together with various continuous and dispersed phases thereof, it will be understood by those skilled in the art that comparable results are obtainable with various other methods/systems and emulsions/continuous phases/dispersed phases, as are commensurate with the scope of this invention.

[0095] The following examples illustrate preparation of particle stabilized emulsions, for use in oil sand, oil shale or related extraction methods, according to certain embodiments of the invention.

Example Ia

[0096] Particle stabilized aqueous liquid- in-CO₂ (A/C) macroemulsions were formed in a high pressure batch reactor (HPBR) with view windows using an apparatus similar to the one shown in FIG. 3. The reactor included a stainless steel pressure cell of 85 mL internal volume equipped with tempered glass windows (PresSure Products G03XC01B). The windows were placed 180° apart, with one illuminated with a 20 W, 12 V compact halogen bulb and the other allowing observation with a video camera. The view window diameter was 25 mm. The window diameter was used as a scale for determining droplet diameter sizes. The reactor was equipped with a pressure-relief valve (Swagelok R3^"A), a thermocouple (Omega KMQSS- 125G-6), a pressure gauge (Swagelok PGI-63B), a bleed valve (Swagelok SS-BVM2), and a 3.2 mm port for admitting CO₂. A cylindrical magnetic stir bar with a cross shape on top (VWR Spinplus) was utilized for internal mixing. Unless otherwise indicated, the stir bar rotated at 1300 rpm. Reactor temperature was adjusted by application of hot air from a heat gun or solid dry ice chips. Example Ib

[0097] For preparation of A/C macroemulsions, the following procedure was carried out: dry hydrophobic particles were added to the HPBR, followed by injection of liquid CO₂. After agitation, a high-pressure syringe pump was used to inject water to a set pressure of 17.2 MPa. For the A/C emulsions, a proportion of -65 mL of CO₂/20 mL OfH₂O was used.

Example Ic

[0098] For most particles used in these representative, non-limiting examples, the particle size was determined from SEM images. In each frame, nearly all particles were counted and measured. For spherical particles, their diameter was measured; for crystalline or irregular particles, the average of two dimensions was taken, one along the long axis and the other along the short axis. The mean diameter was estimated as

(dp)mean = [∑n, (dp) X d_p]/N_t (1) where n, (d_v) is the number of particles counted that have a size d_v, and N₁ is the total number of particles counted. The mean size, (d_v)_msaa, and standard deviation of the particles used in this study are tabulated in Table 1.

Example Id

[0099] For dispersed phase droplet size determination, the HPBR window diameter (25 mm) was used as a scale. The diameter of droplets near the window was measured under magnification and compared with the window diameter.

Table 1. Mean Particle Size and (Standard Deviation) in μm of Pulverized Materials Used for Stabilizing C/A and A/C Type Emulsions

(a) (hydrophilic) limestone CaCO₃ , „.„ particle limestone (Q 6) „. , _λ sand SiO₂ flyash shale lizardite (Qi) (Fisher) mean, size 2 (1.7) 0.55 (0.4) 3.1 (1.6) 4.3 (5.7) 2.5 (3.4) 4.2 (6.0) 4.8 (3.9) μm

(b) Hydrophobic particle carbon black^a coal Tenon m^em' 0.12 4.2 (4.4) 1.8 (1.0) size μm

¹ Manufacturer data; ( ) standard deviation

[00100] The following examples provide results and observations relating to the emulsions prepared above, and illustrate various properties and functional characteristics which can be utilized in the context of oil sand or shale oil hydrocarbon recovery. (For purpose of comparison, various representative hydrophilic particles and corresponding emulsions were prepared and characterized.)

Hydrophilic Particles.

Example 2a

[00101] Limestone. Both Hubercarb as mined pulverized limestone and Fisher Chemical reagent-grade CaCO₃ gave stable C/A macroemulsions. A C/A macroemulsion formed with Hubercarb Ql particles with mean particle size of 0.55 (0.4) μm, where the number in parentheses is the standard deviation. A non-uniform macroemulsion was formed, with heavier globules settling at the bottom of the water column, median-size globules being neutrally buoyant, and large globules floating on top of the water column. The large globules appeared to be partially covered with a sheath of particles.

[00102] A C/A macroemulsion stabilized by Hubercarb Q6 particles with mean particle size of 2 (1.7) μm was formed. After thorough mixing and a rest period, most globules settled in the bottom of the pressure cell, indicating that the globules were heavier than the surrounding water. The globule diameter was in the range of 200-300 μm.

[00103] Macroemulsions were also formed with supercritical CO₂ and Q6 particles. The pressure in the cell was 17.2 MPa at a temperature of 45-47° C. A stable macroemulsion formed with a globule diameter in the 100-150 micron range, smaller than that with liquid CO₂ under the same pressure and mixing conditions. Most globules settled in the bottom of the cell. Even though the density of supercritical CO₂ (-800 kg m^"3) is smaller than that of liquid CO₂ (-930 kg m^"3 at 17.2 MPa and 15° C), the gross density of the supercritical globules was greater than that of the surrounding water.

[00104] Limestone particle-stabilized macroemulsions were also formed in a solution of 3.5 wt % NaCl in deionized water. The globule diameter was similar to that formed in deionized water alone, and all the initially present liquid CO₂ was emulsified. However, no systematic measurements were performed on emulsion yield as a function of NaCl concentration.

[00105] Macroemulsions were also formed with Fisher Chemical C-65 reagent-grade CaCO₃ (mean particle size 3.1 (1.6) μm). Under mild mixing conditions (400-500 rpm), rather large globules were formed, in the 500-800 micron diameter range. The sheath of crystalline particles adhering to the surface of CO₂ droplets was clearly visible.

Example 2b

[00106] Sand. The milled and sieved sand particles had a mean particle size of 4.3 (5.7) μm. The large standard deviation indicates a wide distribution of particle size. The sand particles produced a stable C/A macroemulsion, probably due to the hydrophilic silica content of sand. The globule diameter was in the 200-300 micron range.

Example 2c

[00107] Fly ash. The unprocessed flyash particles had a mean particle size of 2.5 (3.1) μm. The large standard deviation indicates a wide distribution of sizes, but most particles were in the submicron to a few micron size range. The size of the particles, plus their hydrophilic character (similar to sand), was conducive for the formation of a stable C/A macroemulsion. The globule diameter was in the 80-150 micron range.

Example 2d

[00108] Shale. The pulverized shale had a mean particle size of 4.2 (6.0) μm with a wide distribution of sizes. Pulverized shale produced a stable C/A macroemulsion, probably due to the hydrophilic character of shale's major ingredients, clay minerals and quartz. The globule diameter was in the 80-150 micron range. Because of the small bulk density of shale (2.0-2.2 g/cm³), most pulverized shale- sheathed globules floated on top of the water column. Example 2e

[00109] Magnesium Silicate. The pulverized lizardite had a mean particle size of 4.8 (3.9) μm. The appropriate particle size and the hydrophilic character of magnesium silicate produced a stable C/A macroemulsion. The globule diameter was in the 80-130 micron range.

Hydrophobic Particles.

Example 3 a

[00110] Teflon^®. Teflon^® powder is strongly hydrophobic. One gram of the powdered resin produced an aqueous liquid-in-carbon dioxide (AJC) macroemulsion, where water is the dispersed phase and CO₂ is the continuous phase. Water droplets sheathed with Teflon^® particles were evident, and no phase separation occurred during several hours of observation, which indicates that a stable AJC macroemulsion was formed.

Example 3b

[00111] Activated Carbon. When activated carbon (AC) was dispersed in liquid CO₂ under pressure, the AC agglomerated into clumps. Under the conditions employed, upon addition of water and stirring, a black mass ensued in which it was difficult to discern distinct globules.

Example 3 c

[00112] Carbon Black. Carbon black (CB) did disperse in liquid CO₂ without agglomeration. Upon addition of water with stirring, a black, inscrutable liquid ensued. However, no phase separation occurred after several hours of observation, suggesting that a stable AJC emulsion was formed.

Example 3d [00113] Coal. Pulverized coal also dispersed readily in liquid CO₂ without agglomeration. Upon addition of water with stirring, a A/C macroemulsion was formed where water droplets were sheathed with coal particles dispersed in CO₂.

Example 4a

[00114] The example shows that particle stabilized emulsions described herein can be used to extract or remove oil from oil sand or shale oil. As shown in FIG. 8 A, , embodiment 200 includes a mixture of oil and sand. A water-in-oil emulsion comprising a dodecane continuous phase (having an average droplet size of 50-100 μm) and a water dispersed phase stabilized by Teflon^® particles (average size of 1.8 μm) was injected into tube 206 in the direction of arrow 208. Tube 206 extended to the bottom of column 207. As the emulsion exited tube 206 and flowed back up column 207 in the direction of arrow 209, oil was extracted from the mixture of sand and oil. This extraction process resulted in a relatively clean sand 212 (i.e., substantially free of oil), and extracted oil phase 214 as a mixture of oil and dodecane.

Example 4b

[00115] As shown in the comparative example of FIG. 8B, a similar process as described for FIG. 8 was used, except a mixture of oil and sand was extracted using alternating dodecane and water instead of an emulsion of dodecane and water. This extraction process resulted in embodiment 210 including a smaller oil and dodecane phase 220 (compared to that of FIG. 8A), water phase 222, and a mixture of oil and sand 224.

[00116] This example shows that particle stabilized dodecane and water emulsions are more effective in extracting oil from sand and oil mixtures than non- emulsions comprising dodecane and water.

[00117] As demonstrated, the emulsion technology of this invention improves upon the currently practiced extraction method using hot water frothing on account of the greater extraction efficiency of liquid or supercritical CO₂ or other solvents. Emulsions of Water- in-CO₂ (W/C) or Water- in-Oil (W/O) stabilized by fine particles can disperse as much as 50% by volume water in liquid or supercritical CO₂ or other solvents, whereas less than a few percent by volume water can be dissolved in liquid or supercriticalCO₂ or other solvents. Laboratory experiments showed that crude oil is readily displaced from the pores of oil sand or oil shale when using particle stabilized W/C or W/O emulsions. Because the surface of sand or shale granules is hydrophilic, the water readily adsorbs in place of the extracted crude oil. In addition, the emulsion components can be recycled, thus reducing water use requirements and otherwise significantly lowering the material costs inherent in the currently practiced hot water frothing methods. Particle stabilized emulsions of Water-in-CO₂ provide greater extraction efficiencies than water alone, CO₂ alone, or Water- Alternate-Gas (WAG) methods.

[00118] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. For instance, it will be understood by those skilled in the art that various other emulsions can be used in conjunction with this invention, such emulsions including carbon dioxide and/or oil in aqueous emulsions, with corresponding modification to the methods/apparatus and/or systems described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present invention.

Claims

What is claimed.

1. A primary method of subterranean hydrocarbon recovery, said method comprising: providing a subterranean formation comprising a hydrocarbon component, said component selected from a tar, a bitumen precursor of said tar, an oil and a kerogen precursor of said oil; contacting said subterranean formation with a fluid medium comprising an emulsion comprising an aqueous component dispersed in a continuous phase at least partially immiscible with said aqueous component and a particulate component selected from hydrophobic components and combinations thereof, and hydrophilic components and combinations thereof, said particulate component in an amount sufficient for at least partial emulsification, said contact for at least one of a time and at a pressure at least partially sufficient to displace said hydrocarbon component from said formation; and recovering said hydrocarbon component.

2. The method of claim 1 wherein said fluid medium comprises a component selected from a liquid carbon dioxide component, a supercritical carbon dioxide component and combinations thereof.

3. The method of claim 2 wherein a said carbon dioxide component comprises greater than about 1 weight percent of said emulsion.

4. The method of claim 1 wherein said fluid medium comprises a component selected from about Cj to about C₂₀ hydrocarbons, about C₂ to about C₄₀ ethers and combinations thereof.

5. The method of claim 1 wherein said hydrophobic particulate component is selected from coal particles, carbon black particles, activated carbon particles, asphaltene particles, petrocoke particles, fluorocarbon particles, and combinations of said components.

6. The method of claim 1 wherein said hydrophilic particulate component is selected from pulverized limestone particles, pulverized sand particles, pulverized hydrophilic mineral particles, pulverized hydrophilic rock particles, pulverized clay particles and combinations of said components.

7. The method of claim 1 wherein said particulate components are dimensioned from about 5 nanometers to about 100 μm.

8. The method of claim 1 wherein said fluid medium contact is selected from in situ contact and ex situ contact with respect to said formation.

9. The method of claim 8 wherein said contact is in situ, said method comprising contacting said formation with an organic component at least partially immiscible with said aqueous component, said organic component comprising a compound selected from C₂ to about C₂₀ hydrocarbon compounds, said hydrocarbon compounds selected from straight-chain, branched and cyclic aliphatic compounds and aromatic compounds, and C₂ to about C₄₀ ether compounds, and combinations of said hydrocarbon and ether compounds, said contact prior to said ex situ contact.

10. The method of claim 8 wherein said contact is ex situ, said method comprising contacting excavated formation with an organic component at least partially immiscible with said aqueous component, said organic component comprising a compound selected from C₂ to about C₂₀ hydrocarbon compounds, said hydrocarbon compounds selected from straight-chain, branched and cyclic aliphatic compounds and aromatic compounds, and C₂ to about C₄₀ ether compounds, and combinations of said hydrocarbon and ether compounds, said contact prior to said ex situ contact.

11. A method of using a particulate-stabilized carbon dioxide emulsion for hydrocarbon extraction from an oil sand/oil shale formation, said method comprising: providing a formation comprising at least one of oil sand and oil shale, and a hydrocarbon component deposited therewith; contacting said formation with an emulsion comprising a liquid carbon dioxide component, a supercritical carbon dioxide component or a combination thereof, and an aqueous component, said emulsion comprising a particulate component selected from hydrophobic components and combinations thereof, said particulate component in an amount sufficient for at least partial emulsification, said contact for at least one of a time and at a pressure at least partially sufficient to displace said hydrocarbon from said formation; and recovering said hydrocarbon component, and at least one of a portion of said emulsion and a carbon dioxide component thereof.

12. The method of claim 11 wherein said continuous phase of said emulsion comprises a said carbon dioxide component comprising greater than about 1 weight percent of said emulsion.

13. The method of claim 11 wherein said hydrophobic particulate component is selected from coal particles, carbon black particles, activated carbon particles, asphaltene particles, petrocoke particles, fluorocarbon particles and combinations of said components.

14. The method of claim 11 wherein said emulsion contact is ex situ.

15. A method of using a particulate-stabilized aqueous liquid-carbon dioxide emulsion for hydrocarbon extraction from an oil sand/oil shale formation, said method comprising: providing a formation comprising at least one of oil sand and oil shale, and a hydrocarbon component deposited therewith; contacting said formation with an emulsion comprising a liquid carbon dioxide component, a supercritical carbon dioxide component or a combination thereof, and an aqueous component, said emulsion comprising a particle component selected from hydrophilic particulate components and combinations thereof, said particulate component in an amount sufficient for at least partial emulsification, said contact for at least one of a time and at a pressure at least partially sufficient to displace said hydrocarbon from said formation; and recovering said hydrocarbon component, and at least one of a portion of said emulsion and a carbon dioxide component thereof.

16. The method of claim 15 wherein said continuous phase of said emulsion comprises a said aqueous component comprising greater than about 1 weight percent of said emulsion.

17. The method of claim 15 wherein said hydrophilic particulate component is selected from pulverized limestone particles, pulverized sand particles, pulverized hydrophilic mineral particles, pulverized rock particles, pulverized clay particles, and combinations of said components.

18. The method of claim 15 wherein said emulsion contact is ex situ.