DISPERSION OF COMPOUNDS FOR THE STIMULATION OF BIOGENIC GAS GENERATION IN DEPOSITS OF CARBONACEOUS MATERIAL
Methods of dispersing an activation agent, nutrient, or both to a carbonaceous material to stimulate production of a biogenic gas are described. The methods may include accessing a subterranean geologic formation containing the carbonaceous material, and supplying a mixture to the formation. The mixture may include an activation agent or nutrient mixed with a dispersed phase and a continuous phase. The method may also include contacting the carbonaceous material with the mixture, and distributing at least a portion of the activation agent or nutrient over and/or into the carbonaceous material from the dispersed phase. The production of biogenic gases is increased by microorganisms that are stimulated by the distributed activation agent or nutrient to convert a portion of the carbonaceous material into the biogenic gases.
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This application claims the benefit of U.S. Provisional Application No. 61/613,380, filed Mar. 20, 2012, entitled “Dispersion of Compounds for the Stimulation of Biogenic Gas Generation in Deposits of Carbonaceous Material.” The entire disclosure of which is incorporated herein by reference for all purposes.BACKGROUND OF THE INVENTION
As the price of oil rises, along with economic and environmental pressures to find local and alternative energy sources, the use of natural gas as a safe and reliable energy source continues to grow. Natural gas is used as an energy source for heating, electric power generation, and transportation fuel. Natural gas is also used for the production of hydrogen, and in many manufacturing processes.
The majority of natural gas is found in underground deposits, many of which are the same geologic formations that contain liquid and solid carbonaceous material such as oil fields and coal beds. Much of the production of natural gas is believed to occur by biogenic processes, such as by methanogenic microorganisms that exist in the geologic formations and metabolize the carbonaceous material into substances such as natural gas as a metabolic product. The work of these microorganisms over thousands and millions of years has produced deposits of natural gas that measure in the trillions of cubic feet.
As natural gas use increases globally, these reserves will be depleted creating new types of energy crises. Fortunately, the same biogenic processes that originally produced many of these deposits may be utilized to continue producing natural gas on a globally significant scale. Furthermore, if biogenic processes may be improved or enhanced to convert even a small fraction of the carbonaceous material in current formations to natural gas, the quantities produced could be enormous. For example, the Powder River Basin in northeastern Wyoming is estimated to contain over 1 trillion short tons of coal. If even 1% of this coal could be converted to natural gas, it could supply the current annual natural gas usage in the United States (about 23 trillion cubic feet) for four years. Many previously mined coal and oil fields in the United States alone that have become economically prohibitive to continued mining still contain these quantities of residual carbonaceous materials.
Among the challenges faced in the biogenic conversion of these carbonaceous materials to natural gas and other hydrocarbons is providing an ample and continued source of nutrients and activation agents to the microorganisms that metabolize the carbonaceous materials. The standard spacing of wells for natural gas production is typically forty or eighty acre spacing (i.e., 1 well/40 acres 1 well/80 acres). Due to the depths and spacing of these wells, as well as the underground distances covered by the formations, gas produced through methanogenesis may take a substantial amount of time to travel to the surface for collection. Nutrients and activation agents that have been introduced into the formation to activate or stimulate methanogenesis may be exhausted long before it has had sufficient opportunity to be widely distributed by the advective dispersion processes within the formation. This may slow, or even prevent, the enhanced conversion of carbonaceous material into natural gas, because only a small portion of the subsurface microorganism populations' growth and activity.
Thus, there is a need for improved nutrients and activation agents for stimulating the biogenic production of natural gas and other metabolic products. There is also a need for improved ways of delivering nutrients and activation agents into the formation environment. These and other needs are addressed by the present invention.BRIEF DESCRIPTION OF THE INVENTION
Additional production of biogenic gases from carbonaceous materials found in geologic formations may be realized by supplying mixtures to microorganisms in the formations that stimulate their conversion of the carbonaceous materials to gases like hydrogen and methane. The mixtures may include one or more liquid dispersed phases surrounded by a liquid continuous phase that is characteristic of an emulsion. The mixtures may also include solid phase materials characteristic of a suspension. The compounds in the mixtures that stimulate biogenic gas production from the microorganisms may include activation agents and/or nutrients. These compounds may be at least partially dissolved in one or more liquid phases of the mixture that is supplied to the microorganisms. In some instances the materials that form a liquid phase (e.g., a dispersed phase) may also act as a nutrient or activation agent for the microorganisms.
Exemplary mixtures may include oil-in-water and water-in-oil emulsions. The “oil” phase may be made of a non-polar liquid at the working temperatures of the mixture, and the “water” phase may be made from a polar liquid such as water or an aqueous solution, though other polar liquids may be used instead of (or in addition to) water. Exemplary mixtures may also include more complex multiple emulsions where the dispersed phase includes two or more liquid phases that are not completely miscible. Examples of these multiple emulsions may include water-in-oil-in-water (W/O/W) emulsions which have a dispersed phase that includes a core polar “water” droplet surrounded by a non-polar “oil” droplet surrounded by a polar “water” continuous phase.
Embodiments of the invention may include methods of dispersing an activation agent to a carbonaceous material to stimulate production of a biogenic gas. The methods may include accessing a subterranean geologic formation containing the carbonaceous material, and supplying a mixture to the formation. The mixture may include the activation agent mixed with a dispersed phase and a continuous phase. The method may also include contacting the carbonaceous material with the mixture, and distributing at least a portion of the activation agent over and/or into the carbonaceous material from the dispersed phase. The production of biogenic gases is increased by microorganisms that are stimulated by the distributed activation agent to convert a portion of the carbonaceous material into the biogenic gases.
Embodiments of the invention may also include methods of providing a nutrient to a carbonaceous material to stimulate production of biogenic gas from the material. The methods may include accessing a geologic formation containing the carbonaceous material, and delivering a mixture to the formation that includes a dispersed phase, a continuous phase, and the nutrient incorporated into at least one of these phases. The mixture may contact the carbonaceous material and become available to microorganisms in proximity to the material. The nutrient stimulates the microorganisms to convert at least a portion of the carbonaceous material into biogenic gas, increasing the production of the biogenic gas.
Embodiments of the invention may still further include methods of introducing multiple portions of a compound or a mixture of compounds to microorganisms in a geologic formation. The methods may include accessing a geologic formation containing carbonaceous material, and supplying an emulsion to the formation. The emulsion may have a continuous phase and a dispersed phase, and a first portion of the compound or a single component of a mixture of compounds is incorporated into the continuous phase while a second portion of the compound or a component of the mixture of compounds is incorporated into the dispersed phase. The first portion of the compound in the continuous phase is introduced to the microorganisms when the emulsion contacts the microorganisms, and the second portion of the compound is introduced after the microorganisms make contact with the dispersed phase. The compound stimulates the microorganisms to convert the carbonaceous material into one or more biogenic gases.
Additional embodiments and features are set forth in part in the ensuing detailed description and accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the specification, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.
The present invention is described in conjunction with the appended figures:
In the appended figures, similar components and/or features may have the same numerical reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components and/or features. If only the first numerical reference label is used in the specification, the description is applicable to any one of the similar components and/or features having the same first numerical reference label irrespective of the letter suffix.DETAILED DESCRIPTION OF THE INVENTION
Methods, systems and compositions are described for stimulating production of biogenic gases in geologic formations with activation agent and/or nutrient mixtures that may include two or more liquid phases that are not fully miscible (e.g., emulsions). The emulsions may allow agents and nutrients to be dispersed over a larger portion of carbonaceous material located in the formation, and/or may allow a controlled release of the agents and nutrients over a longer period of time. This allows the agents and nutrients to be accessible to a larger number of microorganisms in the carbonaceous material, and for longer periods. In some instances, one or more of the liquid phases may themselves constitute agents and/or nutrients for microorganisms.
The stimulation effects of the agents and nutrients may include increasing the rate of production of the biogenic gas and/or an intermediary in a metabolic process that produces the gas. The effects may also include activating a consortium of microorganisms in the formation to start producing the biogenic gas. They may further include stopping or decreasing a “rollover” effect such as when the concentration of one or more metabolic products starts to plateau (or even drop) after a period of monotonically increasing.
In some instances, microorganisms may be provided in the mixtures themselves, and/or in separate solutions introduced to the geologic formation. The microorganisms may be provided to areas of the geologic formation (such as the carbonaceous material) that show little or no biological activity. They may also be provided to increase the microorganism population in areas where microorganisms are already present (e.g., where there is already a native microorganism population.) The added microorganisms may be selected to work in concert with the agent/nutrient mixture supplied to the formation.
Compounds used in the methods described may act as nutrients, activation agents, initiators, or catalysts for increasing the production of biogenic gases including hydrogen and methane. As nutrients, the microorganisms may consume the compounds allowing the microorganism populations to grow more rapidly than without the compounds. As activation agents, the compounds may lower an activation barrier, open a metabolic pathway, modify a carbonaceous material, change the reaction environment, and may or may not be rapidly consumed as a nutrient.
When the compound is acting primarily like a nutrient, consumption of the nutrient by the microorganisms may increase the production of biogenic gas by a stoichiometrically proportional amount to that of the compound used. Alternatively, when a compound is acting primarily as an activation agent, the increased amount of biogenic gas may be much larger than the amount of the compound added. Thus, in such a scenario, introducing small quantities of the compound may produce much more than stoichiometric quantities of the biogenic gases. When the compound acts as an activation agent, the compound may or may not act as a catalyst, and may be fully, partially, or not consumed while increasing the production of biogenic gas.
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Accessing the geologic formation 110 may also include accessing microorganisms present in the formation. These microorganisms may include methanogenic microorganisms that convert adjacent carbonaceous material into hydrogen (H2), methane (CH4), and/or other metabolic products that have hydrogen-to-carbon ratios higher than the starting carbonaceous material. The microorganisms may also include species of methanogenesis inhibitors that slow or inhibit methanogenic metabolic processes by consuming methanogenic precursors and/or producing compounds that inhibit methanogenesis.
The method 100 may include a biological analysis 112 of the microorganisms. This may include a quantitative analysis of the population size determined by direct cell counting techniques, including the use of microscopy, DNA quantification, phospholipid fatty acid analysis, quantitative PCR, protein analysis, etc. The identification of the genera and/or species of one or more members of the microorganism consortium by genetic analysis may also be conducted. For example, an analysis of the DNA of the microorganisms may be done where the DNA is optionally cloned into a vector and suitable host cell to amplify the amount of DNA to facilitate detection. In some embodiments, the detecting is of all or part of ribosomal DNA (rDNA), of one or more microorganisms. Alternatively, all or part of another DNA sequence unique to a microorganism may be detected. Detection may be by use of any appropriate means known to the skilled person. Non-limiting examples include restriction fragment length polymorphism (RFLP) or terminal restriction fragment length polymorphism (TRFLP); polymerase chain reaction (PCR); DNA-DNA hybridization, such as with a probe, Southern analysis, or the use of an array, microchip, bead based array, or the like; denaturing gradient gel electrophoresis (DGGE); or DNA sequencing, including sequencing of cDNA prepared from RNA as non-limiting examples. The identification of putative metabolic functions that are encoded in the DNA of individual organisms may also be conducted by employing Single Cell Whole Genome Sequencing (SC-WGS). The isolation of hundreds of individual cells in a sample from the geologic formation may be achieved. Hundreds of individual cells may be isolated using fluorescence-activated cell sorting to separate and deposit each cell into its own well in a microtiter plate. The deposited cell may be lysed, its entire genome amplified then screened for identity using SSU rRNA census sequencing techniques and appropriate amplified genomes selected for genome sequencing. Gene annotation of SC-WGA samples can be done using the Integrated Microbial Genomes (IMG) and RAST databases to provide a comprehensive comparative analysis of putative gene function and uncover the dominant metabolic and degradation pathways for the most abundant and active bacteria within the samples. Additional details of the biological analysis of the microorganisms is described in co-assigned U.S. patent application Ser. No. 11/099,879, filed Apr. 5, 2005, the entire contents of which is herein incorporated by reference for all purposes. By determining characteristics of the microorganisms and dominant metabolic functions, activation agents and nutrients may be provided that target particular microorganisms or metabolic pathways in order to stimulate or favor metabolism of the carbonaceous material to make particular metabolic products or biogenic gases.
The method 100 may also include environmental analysis of the formation environment. For example, extracted geologic formation samples such as water, rock, and sediment bearing the carbonaceous material may be analyzed using spectrophotometry, NMR, HPLC, gas chromatography, mass spectrometry, voltammetry, and other chemical instrumentation. The tests may be used to determine the presence and relative concentrations of elements like dissolved carbon, phosphorous, nitrogen, sulfur, magnesium, manganese, iron, calcium, zinc, tungsten, cobalt, and molybdenum, among other elements. The analysis may also be used to measure quantities of polyatomic ions such as PO23−, PO33−, and PO43−, NH4+, NO2−, NO3−, and SO42−, among other ions. The quantities of vitamins, and other nutrients may also be determined. An analysis of the pH, salinity, oxidation potential (Eh), and other chemical characteristics of the formation environment may also be performed. Additional details of chemical analyses that may be performed are described in co-assigned PCT Application No. PCT/US2005/015259, filed May 3, 2005; and U.S. Pat. No. 7,426,960, filed Jan. 30, 2006, of which the entire contents of both applications are herein incorporated by reference for all purposes.
Once access to the geologic formation is available, a mixture may be provided 115 to stimulate the production of biogenic gas (e.g., methanogenesis). The mixture may take the form of an emulsion that incorporates one or more activation agents and/or nutrients that are provided to the geologic formation. Techniques for providing the mixture 115 may include direct injection processes that pump and/or pour the mixture into the formation environment.
The mixture may be non-homogeneous or homogeneous, and may include multiple phases, including solid and liquid phases, and two or more liquid phases. Exemplary mixtures having two or more liquid phases may include emulsions that have one or more dispersed phases surrounded by a continuous phase. The lack of miscibility that causes the separate liquid phases may be due to different polarities of the liquids. For example, a dispersed liquid phase may be non-polar while the continuous phase is polar. Conversely the dispersed phase may have a polar liquid while the continuous phase is made from a non-polar liquid.
Exemplary emulsions may include oil-in-water (O/W) emulsions that have a non-polar dispersed phase incorporated into a continuous phase that include polar water molecules. They may also include water-in-oil (W/O) emulsions where droplets of polar water or an aqueous solution are dispersed in a non-polar hydrocarbon-containing continuous phase. The emulsions may be classified as microemulsions and/or nanoemulsions if the size of the dispersed-phase droplets are the requisite size. The emulsion may be a single emulsion containing two-phases, such as O/W, or may alternatively, in some embodiments, be a multiple emulsion including an emulsion contained in a separate continuous phase, such as W/O/W for example. The mixture may further contain surfactants and/or emulisifiers that slow or prevent the dispersed phases from coagulating and/or forming a separate layer of the mixture.
The activation agents and/or nutrients may be dissolved in the one or more dispersed phases, the continuous phase, or both. For example, the agents/nutrients may be soluble in a polar solvent such as water (i.e., an aqueous phase), or a non-polar solvent such as found in an “oil” phase. Depending on whether the emulsion is (1) oil-in-water or (2) water-in-oil, the agents/nutrients that are soluble in the aqueous phase would be found in the continuous phase of (1), and dispersed phase of (2), respectively. Agents and nutrients that are at least partially soluble in both polar and non-polar solvents may be found in both the dispersed and continuous phases of the emulsions. Examples may further include agents and nutrients that are partially dissolved in one or more of the liquid phases of the emulsion, and that also have a solid phase component suspended and/or precipitated from the liquid phases.
In exemplary emulsions that include polar aqueous phases and a non-polar (e.g., “oil”) phase, a non-polar “oil” phase may include compounds having at least a non-polar, hydrophobic/lipophilic moiety such as a long chain hydrocarbon. Examples of these non-polar compounds may include mineral oils, essential oils, and organic oils, among other types of oils. They may further include lipids and fatty acids that include non-polar, hydrophobic hydrocarbon tails. Exemplary fatty acids may include naturally occurring, saturated and/or unsaturated fatty acids such as myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, linoleic acid, α-linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosahexaenoic acid, ricinoleic acid, etc., among other fatty acids having one or more double-bonds between carbon atoms in the hydrocarbon chains, and including configurations with hydrogen atoms being located on the same or opposite sides of the double bond, such as with cis- or trans-configurations of the acids. Exemplary saturated fatty acids may include lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, etc., among other fatty acids that have no double bonds and are saturated with hydrogen atoms. Some of the possible combinations of acids that may be used in the non-polar phase may be from naturally occurring fats and oils, and may include animal fats including lard, duck fat, butter, as well as vegetable fats including coconut oil, palm oil, cottonseed oil, wheat germ oil, soya or soybean oil, olive oil, corn oil, sunflower oil, safflower oil, hemp oil, canola oil, among others. Other possible combinations may include engineered formulations that have been shown to remain dispersed in oil-in-water emulsions for particular periods of time without creaming or separation of the dispersed non-polar phase.
Polar phase compounds may include water, or aqueous solutions incorporating salts, sugars, proteins, amino acids, chlorogenic acids, protein hydrolyzates, various cell extracts such as yeast extract, algal extracts, or other compounds including volatile fatty acids, or acids such as acetic acid, propionate, butyrate, oxyphosphorous acids, etc. Additional exemplary polar phase compounds may include formamide, dimethyl sulfoxide, and ferulic acid among others. The included algal extracts may include Chlamydomonaas spp., or Spirulina spp., for example.
A compound that acts as a nutrient or activation agent may be contained within one or more phases of the mixture that is provided 115 to the geologic formation. The compound may stimulate the microorganisms to metabolize carbonaceous material in the formation into biogenic gas, such as methane, or into intermediate metabolites that may further be metabolized into biogenic gases. The activation agent may contain various compounds for stimulating microorganisms in the formation environment. Activation agents provided may include phosphorous compounds, acetate compounds, or other nutrients for the microorganisms.
The phosphorus compounds may include phosphorus compounds (e.g., POx compounds were x is 2, 3 or 4), such as sodium phosphate (Na3PO4) and potassium phosphate (K3PO4), as well as monobasic and dibasic derivatives of these salts (e.g., KH2PO4, K2HPO4, NaH2PO4, Na2HPO4, etc.). They may also include phosphorus oxyacids and/or salts of phosphorus oxyacids. For example, the phosphorus compounds may include H3PO4, H3PO3, and H3PO2 phosphorus oxyacids, as well as dibasic sodium phosphate and dibasic potassium phosphate salts. The phosphorus compounds may also include alkyl phosphate compounds (e.g., a trialkyl phosphate such as triethyl phosphate), and tripoly phosphates. The phosphorus compounds may further include condensed forms of phosphoric acid, including tripolyphosphoric acid, and pyrophosphoric acid, among others. They may also include the salts of condensed phosphoric acids, including alkali metal salts of tripolyphosphate (e.g., potassium or sodium tripolyphosphate), among other salts, and may also include oxides of phosphorus (e.g., phosphorus trioxide, pentoxide, etc.), among other compounds.
Examples of the acetate compounds may include acetic acid, and/or an acetic acid salt (e.g., an alkali metal salt of acetic acid, an alkali earth metal salt of acetic acid, sodium acetate, potassium acetate, etc.), among other acetate compounds. Other activation agents that may be provided include nutrients such as yeasts and yeast extracts, and may include digests and extracts of commercially available brewers and bakers yeasts. Other activation agents may include nutrients including carboxylate compounds, proteins, hydrogen release compounds, minerals, metal salts, and/or vitamins, among other components. Catalysts may also be provided in the emulsions to activate the microorganisms or particular metabolic pathways. Still other compounds that may be included in the emulsion include cyclic and aromatic compounds that may include either or both of an ether linked group and an ester linked group, and may include vanillin and syringic acid, among other compounds and acids with a phenol group or other aryl group, and functional groups that may include, in some embodiments, hydroxyl groups, carboxylates, aldehydes, ethers, esters, etc., among others.
The emulsion may be provided 115 in several separate applications over time as opposed to a single application. These separate applications may provide multiple stages of activation or stimulation over a period of time that may be monitored either through the rate of production of biogenic gas, or alternatively through in situ measurements of the concentrations of the activation agent or a metabolic byproduct produced during the conversion of the carbonaceous material. Additionally, these introductions may be made to the formation over the course of the activation period to maintain a certain concentration level or range of the activation agent in the formation.
Once the mixture has been formed and provided, it may be dispersed through the geologic formation 120. The dispersion of the mixture may be done using a variety of techniques, such as high-pressure pumping that forces the mixture to permeate the formation environment. The dispersion pattern of a mixture's agents and/or nutrients with respect to the formation and the carbonaceous material may be based at least in part on how the liquid phases are emulsified and how the agents/nutrients are dissolved in the liquid phases. For example, in a mixture that is an oil-in-water emulsion having the agent/nutrient dissolved in the non-polar, dispersed “oil” phase, the agent/nutrient may be transported further by the aqueous continuous phase across the carbonaceous material before being absorbed. Moreover, when the same emulsion encounters native formation water in contact with the carbonaceous material, the distribution of the non-polar dispersed phase may be more localized along the boundary of the formation water and carbonaceous material. It may also distribute the dispersed phase over a larger area of the carbonaceous material at the water-material boundary. In this example, more agent/nutrient may be supplied to the carbonaceous material by localizing the non-polar dispersed phase close to the surface of the material instead of diluting it throughout the adjacent formation water.
As the mixture is introduced to the formation, it may make direct contact with carbonaceous material and/or indirect contact by first being dispersed in the formation before reaching the carbonaceous material. The microorganisms may be found in a variety of locations in the geologic formation, including the carbonaceous material and/or the formation water, among other locations. The mixture may be dispersed within the geologic formation 120 in order to reach the microorganisms that may then be stimulated by the activation agent. The microorganisms may access the activation agent directly, or in some embodiments, may consume the non-polar dispersed phase to access the activation agent. In consuming or metabolizing the non-polar dispersed phase, the microorganisms may be provided with an additional nutrient source in addition to the activation agent. Metabolizing the non-polar dispersed phase may produce an acetate compound that may be utilized by the same or different microorganisms within the formation environment as an additional nutrient source to stimulate the microorganisms. Metabolizing the non-polar dispersed phase may also produce hydrocarbons that are similar in nature and structure to the carbonaceous material being converted by the microorganisms, and may produce metabolic products including biogenic gases, among other products.
Method 100 may also include measuring the rate of biogenic gas production 125. For the biogenic gas products, the partial pressure of the product in the formation may be measured. Measurements may also be made before providing the activation agent, and a comparison of the product concentration before and after the activation agent may also be made. The biogenic gas products may also be recovered from the formation environment, or maintained within the formation environment at a concentration range that has been found to stimulate the microorganisms to generate more of the biogenic gas product. Based on the rate of biogenic gas production, more or less activation agents or nutrients may be added to the geologic formation in order to maximize biogenic gas output.
Once the surfactant has been properly combined with the non-polar fluid, the method 200 may include producing a primary emulsion by adding the portion of the polar fluid containing the nutrient to the non-polar fluid with the surfactant 214. The emulsion may be produced by agitating the combined fluids in a blender, magnetic mixer, or another device that applies relatively high shear to the emulsion components. The emulsion may be further stabilized by processing the emulsion in a colloid mill or homogenizer, or a device that applies a very high level of hydraulic shear to the emulsion. This produced emulsion may have macro, micro, or nano-sized particles depending on the requirements of the particular application. The emulsion may also be produced in a device that raises the temperature of the components above room temperature during the processing. Raising the temperature of the emulsion may reduce the viscosity of the dispersed phase which may facilitate emulsification of the components. The temperature of the components may be raised during the processing to above or about 25° C., above or about 50° C., above or about 70° C., or above or about 90° C.
After the primary emulsion has been produced and stabilized, the method 200 may further include making a multiple emulsion. A second portion of a polar fluid, which may include a surfactant and/or emulsifier, may be used as a continuous phase in the multiple emulsion. The surfactant may have a higher HLB value, making it more hydrophilic. For example, the surfactant may have an HLB value above or about 8, above or about 10, above or about 13, above or about 15, or above or about 18.
The method 200 may also include adding the primary emulsion to the second portion of the polar fluid with the surfactant to produce a multiple emulsion 216. The multiple emulsion may be produced by agitating the combined fluids using a relatively low shear device to avoid separating the primary emulsion. For example, a blender or magnetic mixer may be utilized to produce both the primary emulsion and the secondary emulsion. The speed used for the secondary emulsion may be lower than the speed used for the primary emulsion, and may be, for example, 50% or less of the speed used in the primary emulsion. The degree of shear used in the preparation of the primary and secondary emulsion may vary depending on the polar and non-polar fluids and surfactants used, as well as the types of encapsulated compounds. A high-shear device may be used to produce the primary emulsion, such as a high-pressure homogenizer. A low-shear device may be used to create the secondary emulsion, such as a combined orifice device, or a device utilizing a membrane emulsification technique. Regardless of the devices used for preparing the emulsions, the osmotic gradient between the two portions of the aqueous fluids may be maintained at a low-enough threshold such that the encapsulated aqueous portion does not pass through the non-polar fluid phase into the continuous aqueous phase. The osmotic pressure between the two aqueous phases may be adjusted by changing the concentrations of the fluids, which may be done, for example, with the addition of the surfactants, or alternatively by adding various salts, sugars, sugar esters, and/or other compounds.
The surfactants used in the emulsions may be selected based on the compounds provided to the carbonaceous material. Surfactants used may include cationic surfactants, such as benzalkonium chloride; anionic surfactants, such as alkali or amine soaps, and detergents; and/or Zwitterionic surfactants, such as CHAPS or sultaines, amino and imino acids, or phosphates such as lecithin.
The emulsions may also include nonionic emulsifying agents. Nonionic emulsifiers that may be used in either of the primary emulsion or the secondary emulsion may include, for example, polymeric and non-polymeric compounds, as well as fatty alcohols, such as cetyl alcohol, stearyl alcohol, cetostearyl alcohol, and oleyl alcohol, among others. Other examples of nonionic surfactants that may be used in the formation of the emulsions include glyceryl monostearate, polyoxyethylene monooleate or monostearate or monolaurate, and other polyoxyethylene glycol alkyl ethers (PEG-400 emulsifiers), polyoxypropylene glycol alkyl ethers, glucoside alkyl ethers, potassium oleate, sodium lauryl sulfate, and sodium oleate, among others. Still other examples of nonionic emulsifiers that may be used in the formation of the emulsions may include sorbitan alkyl esters (Spans), including sorbitan monolaurate (Span 20), sorbitan monopalmitate (Span 40), sorbitan monostearate (Span 60), sorbitan tristearate (Span 65), sorbitan monooleate (Span 80), sorbitan sesquioleate (Span 83), and sorbitan trioleate (Span 85), among others. Other examples of nonionic surfactants that may be used in the formation of the emulsions may include triethanolamine oleate, polyoxyethylene derivatives of sorbitan alkyl esters (Tweens), including polyoxyethylene sorbitan monolaurate (Tween 20), polyoxyethylene sorbitan monolaurate (Tween 21), polyoxyethylene sorbitan monopalmitate (Tween 40), polyoxyethylene sorbitan monostearate (Tween 61), polyoxyethylene sorbitan tristearate (Tween 65), polyoxyethylene sorbitan monooleate (Tween 80), polyoxyethylene sorbitan monooleate (Tween 81), and polyoxyethylene sorbitan trioleate (Tween 85), among others.
The emulsions may also incorporate natural emulsifying agents, and/or hydrocolloids. For example, the emulsions may include vegetable derivatives, such as acacia, tragacanth, agar, pectin, carrageenan, lecithin, and others; or animal derivatives, such as gelatin, lanolin, and cholesterol, among others. Semi-synthetic agents such as methylcellulose, and carboxymethylcellulose, and fully synthetic agents such as Carbopols may also be used.
Solid particle emulsifiers may be used to form a particulate layer around the dispersed phase. These agents may include dispersed particles of bentonite, veegum, hectorite, magnesium hydroxide, magnesium trisilicate, and aluminum hydroxide, among others.
The method 200 may also include transporting the emulsion to the geologic formation 218. The transporting may be done in such a way as to maintain the stabilized emulsion, such as by utilizing transportation equipment and vehicles that will minimize changes in temperature or pressure on the emulsion. In some embodiments, the emulsion may be made at the site of the geologic formation where the compound may be injected, such that transportation may not be a concern. Where the emulsion must be transported over long distances, additional surfactants, mixing transportation vessels, or different amounts of the surfactants used in the preparation of the emulsion may be utilized to produce a stable emulsion.
The emulsion may be injected into the geologic formation 220 to contact the carbonaceous material with the encapsulated compound. The injection may include a pumping mechanism to force the emulsion into the geologic formation, and disperse the emulsion over a greater area of the formation. Alternatively, the emulsion may be poured into the formation and allowed to remain at the site of the injection. Depending on the relative amounts of the polar and non-polar fluids used in the emulsion, the non-polar fluid may allow the activation agent to disperse over a larger area because the non-polar fluid may not be absorbed into the carbonaceous material, formation water, or the formation itself.
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A paused or delayed dispersion may allow greater amounts of nutrients or activation agents to be delivered at lower concentrations over longer periods of time to the carbonaceous material than could otherwise be provided. Adding large amounts of a specific compound to the geologic formation in one dose may in some circumstances create deleterious effects including the death or deactivation of microorganisms. However, by creating multiple emulsions that stage the release of smaller portions of a compound at a time, an overall greater amount of the compound may be used in a single injection. The larger amounts may allow fewer applications of the activation agents to the geologic formation, which may provide for improved consistency of the applications to create a more controlled stimulation of the microorganisms within the formation.
Paused or staged dispersion may allow time for the microorganisms to grow or activate before the additional portion of the activation agent may be released. For example, a greater portion of the activation agent may be contained in the non-polar dispersed phase than in the aqueous continuous phase. Thus, after the microorganisms are activated by the portion of the nutrient contained in the continuous phase, they may be provided with a period of time in which they may grow as a consortium. The non-polar dispersed phase may be consumed as a nutrient by the microorganisms, the consumption of which may release equivalent or greater portions of the activation agent. This second dosing with larger amounts of activation agent may be more effectively utilized by a larger and/or more robust microorganism population that has been given time to grow and acclimate to metabolizing coal carbon to new biogenic methane gas.
Alternatively, a greater portion of the activation agent may be contained in the polar continuous phase of the emulsion, and a lesser amount within the non-polar dispersed phase. Thus, after the greater portion of the activation agent has been utilized to activate the microorganisms, and the microorganisms have penetrated the non-polar dispersed phase, either by its consumption or by the breakdown of the emulsion due to separation, the lesser amount of the activation agent may be utilized to maintain the activation of the microorganisms during their metabolizing of the carbonaceous material. A potential cost savings may be realized by providing the correct proportions of nutrients or activation agents based on the characteristics or dynamics of the microorganisms. Additionally, fewer follow-on introductions of nutrients or activation agents may be required.
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The geologic formation environment may be anaerobic, and thus, the production and transportation of the emulsions may occur under anaerobic conditions. For example, the encapsulated microorganisms may be contained in an anaerobic aqueous fluid used in the primary emulsion. Anaerobic fluid is characterized as having little or no dissolved oxygen, in general no more than 4 mg/L, preferably less than 2 mg/L, and most preferably less than 0.1 mg/L, as measured at 20° C. and 760 mmHg barometric pressure. The microorganisms may be from the same geologic formation to which they will be injected, and are being reinjected in order to be dispersed to alternative portions of the geologic formation, or to a broader area of the geologic formation. Alternatively, the microorganisms may be from a different geologic formation and are being transported to the geologic formation containing the carbonaceous material sought to be converted into biogenic gas. In these or other cases, the microorganisms may have been modified, for example genetically, prior to their being injected or reinjected into the geologic formation. In order to maintain an anaerobic environment for the microorganisms, equipment and vehicles that are oxygen impermeable may be used, otherwise the microorganisms may be damaged in the process.
High-HLB surfactant 421 may be incorporated into polar aqueous fluid 422 in low-shear device 430. The primary emulsion may be added to the polar aqueous fluid 422 in low-shear device 430 to create a multiple emulsion 440. Low-shear device 430 may include a blade-type or magnetic mixer or blender that operates at a speed lower than mixing vessel 410. Alternatively, low-shear device 430 may include a membrane through which the primary emulsion may be passed or pressed. Continuous phase, polar aqueous fluid 422 may be flowed across the membrane of the low-shear device separating droplets of the primary emulsion and creating a secondary, multiple emulsion 440.
Alternatively, system 500 may include transferring multiple emulsion 440 into a vehicle 540 to be delivered to one or more locations at a geologic formation 510. Vehicle 540 may transport the multiple emulsion 440 to alternative geologic formations. When the multiple emulsion 440 is maintained under anaerobic conditions, oxygen impermeable pipes 530 and vehicles 540 may be utilized to prevent the introduction of oxygen to the emulsion 440.
Prior to transportation in vehicle 540, additional emulsifiers, surfactants, or stabilizers may be added to the multiple emulsion 440 in order to facilitate transporting the emulsion in its dispersed form, and to resist separation of the phases. When vehicle 540 arrives at the geologic formation at which the multiple emulsion 440 is to be introduced, multiple emulsion 440 may be added to mixing device 550 to more uniformly disperse any of the primary emulsion that has separated from multiple emulsion 440.EXPERIMENTAL
Experiments were conducted to determine the stability of the emulsion in the presence and absence of coal particles. Into non-sterile micro-centrifuge tubes, emulsified soybean oil emulsion was pipetted in varying dilutions with water filtered by reverse osmosis to a final volume of 1000 mL. Two identical sets were made. The first set contained emulsified oil only, and was examined at several concentrations including 100%, 50%, 10%, and 1%. The second set was prepared by adding 0.5 g of <600 μm ground Anderson coal to the tubes along with the emulsified oil. After liquid additions, all tubes were tightly capped and blended by vortex mixer prior to incubation over night at room temperature. The samples were viewed under magnification using direct light/oil emersion microscopy. Distinct round emulsion micelles were observed at similar numbers in both the coal amended and unamended samples within the same dilution level. This was true at all dilution levels, and both sets of samples were then monitored at set periods of time to determine if and when separation occurred.
Microcosms tests were performed using fresh coal bed methane water from the Powder River Basin with and without 0.5 grams of ground Anderson coal. Emulsified oil amendment was tested for its ability to activate methanogenic coal conversion and compared to various nutritional controls. A microscopic examination of samples from methanogenically active microcosms tests showed the presence of emulsified oil micelles at significantly reduced particle numbers at 150 days after test initiation. These results suggest that amendment materials contained within the emulsion micelles may still be available for long-term slow-release to microorganism consortiums. Additionally, the oil that may be included within the emulsion is also available to the microorganisms for conversion.
Experiments conducted also compared methane production by microorganism consortiums being provided emulsified oil and various other amendments.
A similar set of experiments was conducted to those illustrated in
An additional experiment including carbonaceous material was conducted with similar amendment samples to determine the amount and degree of acetate turnover as shown in
An additional experiment creates additional emulsion products useful according to the present technology. Polyglycerol polyricinoleate (“PGPR”) was blended into soybean oil at 8% by weight (8 g PGPR:100 g Soybean oil) until the solution appeared visibly homogenized in a first solution. Xanthan gum was blended into a solution of yeast extract, acetate, and phosphate at 0.2% by weight to make a second solution. Equal parts of the first and second solutions were blended in bursts at high speed (>5000 RPM) until a viscous product was formed as a third product.
An additional solution of yeast extract, acetate, and phosphate was added to a fresh vessel and stirred at room temperature. To the stirring solution was added 0.5% by weight of a 1:1 ratio of Tween 20 and Tween 80. The solution was stirred for several minutes at low speed (<500 RPM) until bubbles developed. The third product was slowly added to the solution while mixing continued. The final product was blended for several minutes more at low to moderate speed (<1000 RPM) to avoid incorporating air into the mixture.
It will be understood by one of ordinary skill in the art that the embodiments may be practiced differently in different environments. For example, one environment may include wireless control of processes or machinery from a remote terminal that can provide automatic instruction, while another environment may include no such control and is operated locally at the site of the process based on then current operation conditions.
Additionally, it will be understood by one of ordinary skill in the art that the embodiments may be practiced without these specific details. For example, machinery, systems, networks, processes, and other elements in the invention may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known processes, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
Also, it is noted that individual embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process may be terminated when its operations are completed, but could have additional steps not discussed or included in a figure. Furthermore, not all operations in any particularly described process may occur in all embodiments. A process may correspond to a method, a system, a procedure, etc.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes, and reference to “the nutrient” includes reference to one or more nutrients and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise”, “comprising”, “include”, “including”, and “includes”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.
The description and examples above are not intended to limit the scope, applicability, or configuration of the application to only what has been described. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention as set forth in the appended claims.
1. A method of dispersing an activation agent to a carbonaceous material to stimulate production of a biogenic gas, the method comprising:
- accessing a subterranean geologic formation containing the carbonaceous material;
- supplying a mixture to the geologic formation, wherein the mixture comprises the activation agent mixed with a dispersed phase and a continuous phase;
- contacting the carbonaceous material in the formation with the mixture, wherein the dispersed phase distributes at least a portion of the activation agent over and/or into the carbonaceous material; and
- increasing the production of the biogenic gas from microorganisms stimulated by the distributed activation agent to convert a portion of the carbonaceous material into the biogenic gas.
2. The method of claim 1, wherein the dispersed phase comprises a non-polar liquid and the continuous phase comprises water.
3. The method of claim 1, wherein the mixture comprises a multiple emulsion comprising water-in-oil-in-water, and wherein the dispersed phase comprises a non-polar liquid surrounding an aqueous solution and the continuous phase comprises water.
4. The method of claim 3, wherein the activation agent is present in the aqueous solution in the dispersed phase.
5. The method of claim 1, wherein the activation agent comprises at least one compound selected from the group consisting of an acetate compound, a yeast extract, an algal extract, and a phosphorus compound.
6. The method of claim 1, wherein the activation agent comprises an aromatic compound including an ether linked group.
7. The method of claim 1, wherein the activation agent comprises an aromatic compound including an ester linked group.
8. The method of claim 1, further comprising metabolizing the non-polar dispersed phase by the microorganisms, wherein the metabolizing produces an acetate compound.
9. The method of claim 1, wherein the non-polar dispersed phase comprises a fatty acid.
10. The method of claim 1, wherein the contacting the carbonaceous material with the emulsion disperses at least a portion of the activation agent over a greater area of the formation.
11. The method of claim 1, wherein the non-polar dispersed phase allows the emulsion to travel over and/or into the carbonaceous material without being absorbed therein.
12. The method of claim 1, wherein the activation agent comprises sodium phosphate, potassium phosphate, a phosphorus oxyacid, a salt of a phosphorus oxyacid, an alkali metal salt of acetic acid, or an alkali metal earth metal salt of acetic acid.
13. A method of providing a nutrient to a carbonaceous material to stimulate production of a biogenic gas, the method comprising:
- accessing a geologic formation containing the carbonaceous material;
- delivering to the geologic formation a mixture comprising a dispersed phase and a continuous phase, wherein the nutrient is incorporated into at least one of the phases;
- contacting the carbonaceous material in the geologic formation with the mixture, wherein the nutrient becomes accessible to microorganisms; and
- increasing the production of the biogenic gas by stimulating the microorganisms with the nutrient to convert a portion of the carbonaceous material into the biogenic gas.
14. The method of claim 13, wherein the dispersed phase is homogenously distributed in the mixture.
15. The method of claim 13, wherein the dispersed phase comprises a non-polar liquid surrounding an aqueous solution and the continuous phase comprises water.
16. The method of claim 13, wherein at least a portion of the nutrient is located in the dispersed phase.
17. The method of claim 13, wherein the continuous phase comprises an aqueous solution in which the nutrient is partially dissolved.
18. The method of claim 17, wherein the microorganisms consume a portion of the nutrient that is not fully incorporated in the homogenous mixture.
19. The method of claim 15, wherein microorganisms consume the non-polar dispersed phase as an additional nutrient source.
20. The method of claim 19, wherein consuming the non-polar dispersed phase delays the consumption of a second portion of the nutrient incorporated in the liquid mixture.
21. The method of claim 14, wherein the homogenous mixture is an emulsion.
22. The method of claim 21, wherein the emulsion is a microemulsion, and wherein the emulsion further comprises a surfactant.
23. The method of claim 13, wherein the nutrient comprises an aromatic compound including an ether linked group.
24. The method of claim 13, wherein the nutrient comprises an aromatic compound including an ester linked group.
25. The method of claim 13, wherein the nutrient comprises methanol, ethanol, n-propanol, n-butanol, 2,3butanediol, ethanolamine, 3,4,5-trimethoxybenzoate, syringate, vanillate, glycine, cysteine, formate, yeast extract, hydrogen, or carbon dioxide.
26. A method of introducing multiple portions of a compound to microorganisms in a geologic formation, the method comprising:
- accessing a geologic formation that contains carbonaceous material;
- supplying an emulsion to the formation, wherein the emulsion has a continuous phase and a dispersed phase, and wherein a first portion of the compound is incorporated into the continuous phase and a second portion of the compound is incorporated in the dispersed phase;
- introducing the first portion of the compound in the continuous phase to the microorganisms when the emulsion contacts the microorganisms, and introducing the second portion of the compound after the microorganisms contact the dispersed phase;
- wherein the compound stimulates the microorganism to covert the carbonaceous material to one or more biogenic gases.
27. The method of claim 26, wherein the compound comprises an activation agent or a nutrient.
28. The method of claim 26, wherein the compound is selected from the group consisting of methanol, ethanol, n-propanol, n-butanol, 2,3butanediol, ethanolamine, 3,4,5-trimethoxybenzoate, syringate, vanillate, glycine, cysteine, formate, yeast extract, hydrogen, carbon dioxide, sodium phosphate, potassium phosphate, a phosphorus oxyacid, a salt of a phosphorus oxyacid, an alkali metal salt of acetic acid, and an alkali metal earth metal salt of acetic acid.
29. The method of claim 26, wherein the continuous phase comprises water and the dispersed phase comprises a non-polar liquid.
30. The method of claim 26, wherein the biogenic gases comprise hydrogen (H2) or methane (CH4).
31. The method of claim 26, wherein the microorganisms consume the dispersed phase as an additional nutrient source.
32. The method of claim 31, wherein consuming the non-polar dispersed phase produces an acetate compound.
33. The method of claim 26, wherein the dispersed phase comprises two or more phases.
34. The method of claim 33, wherein the dispersed phase comprises a polar-phased droplet surrounded by a non-polar-phased droplet.
International Classification: E21B 43/295 (20060101);