GB2640148A - Immobilizing carbon dioxide in an underground aquifer using carbonate-forming bacteria - Google Patents

Abstract

An immobilization system (200) for sequestering carbon dioxide, in which carbon dioxide (218), a microbial nutrient, and carbonate-forming bacteria (226) are injected in the underground aquifer (Fig. 1; 106) and are configured to form a carbonate from the nutrient and carbon dioxide, the carbonate-forming bacteria encapsulated with an encapsulating layer (228). The encapsulating layer may have a dissolution time activated by a trigger event, such as the presence of water, configured to dissolve when the bacteria, nutrient and CO2 are sufficiently away from the injection site, and it may be impermeable to water until dissolution. The immobilization system may include two concurrent injections of two different bacterial species and their respective nutrient in distinct encapsulation layers, said layers having distinct dissolution times so that the bacteria and nutrients are released simultaneously. The nutrients may include urea.

Description

IMMOBILIZING CARBON DIOXIDE IN AN UNDERGROUND AQUIFER USING

CARBONATE-FORMING BACTERIA

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] N/A.

BACKGROUND OF THE DISCLOSURE

[0002] Carbon sequestration in underground aquifers involves the injection of carbon dioxide into a formation containing an underground aquifer. Because aquifers are often impermeable to water and/or gas, carbon sequestration in underground aquifers is often identified as a long-term to permanent carbon sequestration mechanism. But in some situations, an underground aquifer may develop leaks, and the sequestered carbon dioxide may leak out of the formation. This may reduce the effectiveness of the sequestration.

SUMMARY

[0003] In some aspects, the techniques described herein relate to a method for immobilizing carbon dioxide in an underground aquifer. The method includes injecting carbon dioxide in the underground aquifer. The operator injects a nutrient in the underground aquifer. The operator further injects carbonate-forming bacteria configured to form a carbonate from the nutrient and carbon dioxide. The carbonate-forming bacteria is encapsulated with an encapsulating layer.

[0004] In some aspects, the techniques described herein relate to a bacterial carbon dioxide immobilization system for an underground aquifer. The bacterial carbon dioxide immobilization system includes carbonate-forming bacteria configured to form a carbonate from a nutrient and carbon dioxide. An encapsulating layer encapsulates the carbonate-forming bacteria. The encapsulating layer has a dissolution property to dissolve after a dissolution time.

[0005] In some aspects, the techniques described herein relate to a method for immobilizing carbon dioxide in an underground aquifer. The method includes, at a first time, injecting a first delayed immobilization injection into the underground aquifer. The

-I -

first delayed immobilization injection includes first carbonate-forming bacteria and first nutrients. The first carbonate-forming bacteria and the first nutrients are encapsulated in a first encapsulating layer. At a second time, a second delayed immobilization injection is injected into the underground aquifer. The second delayed immobilization injection includes second carbonate-forming bacteria and second nutrients. The second carbonate-forming bacteria and the second nutrients are encapsulated in a second encapsulating layer. At a third time, an operator causes the first encapsulating layer and the second encapsulating layer to dissolve and expose the first carbonate-forming bacteria and the second carbonate-forming bacteria to the underground aquifer.

[0006] This summary is provided to introduce a selection of concepts that are further described in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Additional features and aspects of embodiments of the disclosure will be set forth herein, and in part will be obvious from the description, or may be learned by the practice of such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to describe the manner in which the above-recited and other features of the disclosure can be obtained, a more particular description will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings For better understanding, the like elements have been designated by like reference numbers throughout the various accompanying figures. While some of the drawings may be schematic or exaggerated representations of concepts, at least some of the drawings may be drawn to scale. Understanding that the drawings depict some example embodiments, the embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: [0008] FIG. 1 is a schematic representation of a bacterial carbon dioxide immobilization system, according to at least one embodiment of the present disclosure.

[0009] FIG. 2 is a schematic representation of a bacterial carbon dioxide immobilization system, according to at least one embodiment of the present disclosure. -2 -

[0010] FIG. 3-1 and FIG. 3-2 are schematic representations of a bacterial carbon dioxide immobilization system, according to at least one embodiment of the present disclosure.

[0011] FIG. 4 is a flowchart of a method for immobilizing carbon dioxide in an aquifer in an underground environment, according to at least one embodiment of the present disclosure.

[0012] FIG. 5 is a flowchart of a method for immobilizing carbon dioxide in an aquifer in an underground environment, according to at least one embodiment of the present disclosure.

DETAILED DESCRIPTION

[0013] This disclosure generally relates to devices, systems, and methods for immobilizing carbon dioxide in an underground carbon dioxide storage system. The underground carbon dioxide storage system may include an underground aquifer. Carbon dioxide may be injected into the underground aquifer. The carbon dioxide may be indefinitely stored in the underground aquifer. This may help to prevent the carbon dioxide from being released into the atmosphere. In this manner, underground carbon dioxide storage may help to prevent further increase of carbon dioxide concentration in the atmosphere and/or reduce the carbon dioxide concentration in the atmosphere. The storage of carbon dioxide may further allow an operator to trade in carbon credits.

[0014] To store the carbon dioxide underground, many underground carbon dioxide storage systems including aquifers bounded by an impermeable upper formation. The impermeable upper formation may be impermeable to water and/or gas. When carbon dioxide is injected into the aquifer, the impermeable upper formation may prevent egress of the carbon dioxide from the underground aquifer.

[0015] In some situations, the carbon dioxide may exit the underground aquifer. For example, the carbon dioxide may travel out of the range of the impermeable upper formation. In some examples, the impermeable upper layer may be semi-permeable, and over time the carbon dioxide may diffuse through the impermeable upper layer. In some examples, the impermeable upper layer may become cracked or otherwise damaged, thereby increasing the permeability of the upper layer and allowing the carbon dioxide to -3 -travel out of the underground aquifer. In some situations, this may result in the carbon dioxide traveling to the surface and exhausting into the atmosphere. In some situations, the leakage of bacteria treated water into the surrounding formation may fill cracks and fissures, which may increase the integrity of the reservoir.

100161 In accordance with at least one embodiment of the present disclosure, a bacterial carbon dioxide immobilization system immobilizes the carbon dioxide in the underground aquifer. The bacterial carbon dioxide immobilization system may include bacteria that is configured to process carbon dioxide and a nutrient to generate a solid carbonate. For example, the bacterial carbon dioxide immobilization system may include bacteria that process carbon dioxide and urea in the presence of urease to generate calcium carbonate. Converting the carbon dioxide into a solid carbonate may immobilize the carbon dioxide, thereby preventing the egress of the carbon dioxide from the underground aquifer. In this manner, the bacterial carbon dioxide immobilization system may help to keep the carbon dioxide in the underground aquifer, thereby preventing the increase in the carbon dioxide concentration in the atmosphere.

100171 In some embodiments, the bacterial carbon dioxide immobilization system may include a delayed immobilization system. For example, the bacteria may be encapsulated in an encapsulating layer. The encapsulating layer may prevent the bacteria from contacting the water and/or the nutrient. This may prevent the bacteria from immobilizing the carbon dioxide until after the encapsulating layer is at least partially removed from the bacteria. The removal (e.g., degradation) of the encapsulating layer may be timed to allow the bacteria to flow away from the injection location of the bacteria before breaking down. In this manner, the bacteria may immobilize the carbon dioxide away from the injection site, thereby reducing or eliminating the formation of solidified carbonate near the injection location that may otherwise block further injection of the carbon dioxide at the injection site. This may allow the bacterial carbon dioxide immobilization system to continue to inject carbon dioxide into the underground aquifer, thereby expanding the carbon dioxide storage capacity of the bacterial carbon dioxide immobilization system without drilling further into the underground aquifer and/or drilling a new wellbore into the underground aquifer. -4 -

[0018] In some embodiments, the carbonate-forming bacteria may be mixed in the aquifer due to flows of the water and brine within the aquifer. Brine within the aquifer may mix based on any factor. For example, brine may mix based on pre-existing flows of water (e.g., currents) through the aquifer. In some examples, carbon-rich brine may be denser than brine having lower concentrations of brine. But the carbon dioxide inserted into the aquifer may have a lower density than the surrounding water. As the carbon dioxide dissolves into the aquifer, this may increase the density of the brine, causing the denser brine to migrate to the bottom of the aquifer, displacing the less dense brine, including upwards and outwards. This may help to mix the encapsulated carbonate-forming bacteria throughout the aquifer. The mixing of the carbon and encapsulated-forming bacteria-enriched brine may be further influenced by any factor, including temperature-influenced convection (including temperature differentials caused by the carbon dioxide/carbonateforming bacteria injection and/or the temperature of the formation), capillary action, chemical reactions with the formation, any other factor, and combinations thereof.

[0019] FIG. 1 is a schematic representation of a bacterial carbon dioxide immobilization system 100, according to at least one embodiment of the present disclosure. The bacterial carbon dioxide immobilization system 100 may include an injection wellbore 102 drilled into a formation 104. The injection wellbore 102 may extend into an underground aquifer 106. The underground aquifer 106 may be any type of aquifer. For example, the underground aquifer 106 may include a cavern or void in the formation 104 that is filled with water. In some examples, the underground aquifer 106 may include a porous or jointed formation, layer, rock, and combinations thereof. The underground aquifer 106 may be formed by water located in the formation. It should be understood that water, as used herein, may include any fluid that may be trapped in the formation. For example, the water may include one or more dissolved substances, including salts, minerals, hydrocarbons, gasses, any other dissolved substance, and combinations thereof. In some examples, the underground aquifer 106 may include a hydrocarbon reservoir including one or more gaseous, liquid, or solid hydrocarbons.

[0020] The underground aquifer 106 may include an impermeable upper layer 108.

The impermeable upper layer 108 may be impermeable to the fluid in the underground aquifer 106. This may help to keep the water and other fluids below the impermeable upper -5 -layer 108, thereby forming at least one boundary to the underground aquifer 106. The impermeable upper layer 108 may include any type of geologic feature, such as a sedimentary layer, a metamorphic layer, an igneous layer, a fault, a formation including one or more cemented voids or joints, any other geologic feature, and combinations thereof [0021] The impermeable upper layer 108 may be impermeable to water in the underground aquifer 106. For example, the impermeable upper layer 108 may prevent egress of water from the underground aquifer 106. In some embodiments, the impermeable upper layer 108 is impermeable to gas. For example, the impermeable upper layer 108 may prevent egress of gas from the underground aquifer 106.

[0022] The underground aquifer 106 may have an aquifer pressure. The aquifer pressure may be at least partially based on the depth of the underground aquifer 106. The underground aquifer 106 may place the fluid within the underground aquifer 106 under a fluid pressure. The underground aquifer 106 may further have an aquifer temperature. In some situations, the aquifer temperature may be based on the depth of the underground aquifer 106, geothermal system, and the surrounding formation 104. The fluid temperature may be based on the aquifer temperature.

[0023] The injection wellbore 102 may extend into the underground aquifer 106 at an injection site 110. An injection system 112 may inject carbon dioxide into the underground aquifer 106. The injection system 112 may include one or more pumps 114. The pumps 114 may pump carbon dioxide through injection pipes 116. The injection pipes 116 may extend into the injection wellbore 102 and open at the injection site 110.

[0024] The injection system 112 may inject the carbon dioxide into the underground aquifer 106 in any form. For example, the injection system 112 may inject the carbon dioxide into the underground aquifer 106 as a fluid. Carbon dioxide may be fluid at pressures above the gas/liquid phase boundary and below the solid/liquid phase boundary of the carbon dioxide phase diagram. Carbon dioxide may further be fluid at temperatures above the solid/liquid phase boundary of the carbon dioxide phase diagram. In some examples, the carbon dioxide may be injected into the underground aquifer 106 when the carbon dioxide is a gas.

[0025] In some embodiments, the carbon dioxide is injected into the underground aquifer 106 as a supercritical fluid. Supercritical carbon dioxide may be a fluid state of -6 -carbon dioxide at conditions above the critical point, or at conditions above the critical temperature and the critical pressure. The critical temperature of carbon dioxide is 304 IC (31.0 °C, 87.8 °F). The critical pressure of carbon dioxide is 7.3 MPa (72.8 atm, 1.1 ksi, 73,8 bar). Supercritical carbon dioxide has a density of between 250 kg/m' and 800 kg/m'.

[0026] In accordance with at least one embodiment of the present disclosure, the underground aquifer 106 may have a fluid pressure and a fluid temperature that may be greater than the critical point of supercritical carbon dioxide. In this manner, the supercritical carbon dioxide inserted into the underground aquifer 106 may stay in the supercritical phase.

[0027] As discussed herein, the density of the supercritical carbon dioxide may be between 250 kg/m3 and 800 kg/m3. Pure water has a density of 1,000 kg/m3. Therefore, the supercritical carbon dioxide may be less dense than the water in the underground aquifer 106. But it should be understood that, based on the type and/or amount of dissolved minerals in the underground aquifer 106, the supercritical carbon dioxide may be approximately the same density or denser than the water in the underground aquifer 106.

100281 In some situations, the carbon dioxide may become dissolved within the fluid of the underground aquifer 106. This may help to immobilize the carbon dioxide when the fluid is trapped within the underground aquifer 106. But the amount of carbon dioxide injected into the underground aquifer 106 may exceed the solubility of carbon dioxide in the fluid of the underground aquifer 106.

[0029] When the carbon dioxide is injected into the underground aquifer 106, at least a portion of the carbon dioxide may extend into the underground aquifer 106 in a carbon dioxide plume 118 extending away from the injection site 110. As discussed herein, the carbon dioxide plume 118, when the carbon dioxide is a supercritical fluid, may float to the top of the underground aquifer 106. This may cause the carbon dioxide plume 118 to congregate at or near the impermeable upper layer 108.

[0030] In some situations, if the impermeable upper layer 108 has any permeability to the carbon dioxide, when the carbon dioxide plume 118 is adjacent or in contact with the impermeable upper layer 108, at least a portion of the carbon dioxide in the carbon dioxide plume 118 may migrate through the impermeable upper layer 108, potentially exhausting to the atmosphere 120. -7 -

[0031] Geologic chemical processes may convert the carbon dioxide to carbonates or other minerals. But geologic timescales are long, and may not solidify or immobilize the carbon dioxide before it migrates out of the underground aquifer 106 if the impermeable upper layer 108 is at least partially permeable to the carbon dioxide.

[0032] In some situations, carbonate-forming bacteria may be injected into the underground aquifer 106. The carbonate-forming bacteria may process nutrients in the underground aquifer 106, generating solid carbonates utilizing the carbon dioxide. The carbonate-forming bacteria may begin forming carbonates as soon the carbonate-forming bacteria is exposed to water and nutrients. In some situations, forming the carbonates may at least partially fill the voids in the underground aquifer 106. These carbonates may at least partially block the flow of the water through the underground aquifer 106.

[0033] Typically, carbonate-forming bacteria may begin forming carbonates at or near the injection site 110. This may cause carbon dioxide flow out of the injection pipes 116 at the injection site 110 to be reduced. In some situations, the flow at the injection site 110 may be stopped. If the flow at the injection site 110 is blocked before all of the intended carbon dioxide is injected into the underground aquifer 106, the blockage may prevent the storage of all of the intended carbon dioxide within the underground aquifer 106. To install the remaining carbon dioxide, the operator may re-drill the injection wellbore 102 and/or use another injection wellbore 102 to access the underground aquifer 106. This may significantly increase the cost of carbon dioxide sequestration in the underground aquifer 106.

[0034] The carbonate-forming bacteria may include any type of carbonate-forming bacteria either directly or indirectly by causing alkaline conditions outside the bacterium. For example, the carbonate-forming bacteria may include at least one of Sporosarcina pastettrii, Bacillus pasteurii, Bacillus sphaericus, Arthrobacter sp., Aliivibrio salmonicida, Bacillus halodurans, Aeribacillus pallidus, Halontonas anticariensis, Bacillus pumilis, Bacillus megaterium,lhionticrospira cntnogena, Lactobacillus delbrueckii, Nocardiopsis lucentensis, Sporosarcina sp., Bre vundimonas sp., Sphingobacterium sp., Acinetobacter sp., Serratia sp., Bacillus mucilaginosus, lhermovibrio ammonificans, Persephonella marina, persephonella marina, Desulfovibrio vulgaris, Bacillus altitudinis, Micrococcus lylae, Micrococcus luteus, Bacillus cereus, Bacillus sp., Sulphurihyd rogen ib itt azorense, -8 -E. coli, Rahella chejuensis, Halomonas sp., Pseudomonas grimontii, ihalassospira sp., Bacillus pumilus, Sulfihydrogenibium yellostonense, Neisseria gonorrhoeae, Bacillus simplex, Psedomonas fragi, Citrobacter,freundii, Enterobacter sp., Bacillus subtilis, Strenotrophomonas acidaminiphila, Staphylococcus sp., Enterobacter taylorae, Enterobacter gergoviae, Aeromonas hydrophila, Aeromonas caviae, Microcella sp., Pullulanihatilhts sp., Synechococcus sp, Clostridium sp., any other carbonate-forming bacteria, and combinations thereof.

[0035] In some embodiments, the carbonate-forming bacteria may have one or more characteristics, including being anaerobic and compatible with the reservoir temperature and pressure. For example, the water in many aquifers may not be oxygenated, or may have a limited supply of oxygen. To survive in this environment, the carbonate-forming bacteria may be an anaerobic bacteria that does not use oxygen in any biological process, or may perform biological processes in an anaerobic environment.

[0036] While embodiments of the present disclosure discuss the microorganisms as bacteria, it should be understood that the microorganisms may be any type of organism that generates carbonates and/or generates conditions conducive to carbonate formation through non-bacterial processes. It should also be understood that carbonate-forming bacteria may be bacteria that directly form carbonates through biological processes. But carbonate-forming bacteria may also include bacteria and other microorganisms that generate conditions conducive to carbonate formation. For example, the carbonate-forming bacteria may alter the pH of the aquifer sufficiently that dissolved carbonate ions may bond with calcium or other ions to form a carbonate. Such reactions may be catalyzed by one or more enzymes. The enzymes may be directly produced by the carbonate-forming bacteria and/or may be injected into the aquifer.

[0037] In some embodiments, the delayed immobilization injection 122 includes a single type of bacteria. In some embodiments, the delayed immobilization injection 122 includes a combination of types of bacteria. The carbonate-forming bacteria may utilize an autotrophic and/or a heterotrophic pathway to facilitate the formation of calcium carbonate.

[0038] In some embodiments, the carbonate-forming bacteria may directly form the carbonates. In some embodiments, the carbonate-forming bacteria may form the carbonates by altering the chemistry of the underground aquifer 106 solution. For example, the -9 -carbonate-forming bacteria may metabolize nutrients, which may result in an increase in the pH of the underground aquifer 106 solution. This may facilitate the precipitation of the carbonate in the underground aquifer 106 solution.

[0039] The carbonate used to immobilize the carbon dioxide may include any carbonate. For example, the carbonate may include calcium carbonate (CaCO3). In some examples, the carbonate may include any other type of carbonate, such as dolomite (CaMg(CO3)2), magnesite (MgCO3), siderite (FeCO3) and dawsonite (NaAICO3(OH)2, any other carbonate, and combinations thereof.

[0040] In accordance with at least one embodiment of the present disclosure, the bacterial carbon dioxide immobilization system 100 may include a delayed immobilization injection 122. The delayed immobilization injection 122 may include bacteria and nutrients that begin forming carbonate after the carbon dioxide plume I I 8 has extended away from the injection site I I 0 and/or after the underground aquifer I 06 has been injected with the target amount of carbon dioxide. The delayed immobilization injection 122 may prevent the carbonate-forming bacteria from forming carbonates at or near the injection site 110. This may help to prevent the formation of the carbonate from blocking the underground aquifer 106 at the injection site 110. In this manner, the bacterial carbon dioxide immobilization system 100 may continue to inject the carbon dioxide into the underground aquifer 106 until the target amount of carbon dioxide has been injected.

[0041] The delayed immobilization injection 122 may include bacteria coated or encapsulated in an encapsulating layer. The encapsulating layer may provide a barrier between the bacteria and the water in the underground aquifer 106. When the encapsulating layer breaks down (e.g., dissolves, cracks, breaks apart), the bacteria may be exposed to the water, and the bacteria may begin forming carbonates. Delaying the exposure of the bacteria to the water may result in carbonate formation at a location away from the injection site 110, thereby reducing or preventing the buildup of carbonates at or proximate to the injection site 110. This may help to maintain the injection of the carbon dioxide into the underground aquifer 106.

[0042] The encapsulating layer may have a dissolution property. The dissolution property may be the property by which the encapsulating layer may dissolve. For example, the dissolution property may be based on dissolution of the material of the encapsulating layer using the fluid in the underground aquifer 106 as a solvent. The encapsulating layer may delay exposure to the underground aquifer 106 based on a time in which the encapsulating layer is exposed to the underground aquifer 106. For example, the encapsulating layer may include a material that is soluble in the fluid of the underground aquifer 106 in the conditions of the underground aquifer 106. Based on the dissolution rate, which may be determined by the material of the encapsulating layer, the thickness of the encapsulating layer, and the content of the underground aquifer 106, the dissolution may take a dissolution time. The dissolution time may be determined based on the injection rate and the rate at which the carbon dioxide plume 118 may expand away from the injection site 110. For example, the dissolution time may be based on the amount of time the carbon dioxide plume 118 may take to reach the extents of the underground aquifer 106. In this manner, the bacteria may begin forming carbonate when the bacteria has traveled away from the injection site 110, thereby maintaining a fluid path for the carbon dioxide to travel through the underground aquifer 106. In some examples, the dissolution time may be based on the amount of time the bacteria may use to travel sufficiently far away from the injection site 110 to maintain a fluid path for the carbon dioxide to travel through the underground aquifer 106. As discussed herein, bacteria injected into the aquifer at different times may have different dissolution times (e.g., different thicknesses of the encapsulating layer, different types of encapsulating layers, and so forth).

100431 In some embodiments, the dissolution time may be in a range having an upper value, a lower value, or upper and lower values including any of 1 s, 10 s, 30 s, 1 min., 5 min., 10 min., 30 min., 1 hr., 2 hr., 3 hr., 6 hr., 18 hr., 1 day, 1.5 days, 2 days, 2.5 days, 3 days, 3.5 days, 4 days, 4.5 days, 5 days, 5.5 days, 6 days, 6.5 days, 1 week., 1.5 weeks, 2 weeks. 3 weeks, 1 month, 2 months, 3 months, 6 months, 1 year, 2 years, 5 years, 10 years, 15 years, 20 years, 25 years, 30 years, 35 years, 40 years or any value therebetween. For example, the dissolution time may be greater than 1 s. In another example, the dissolution time may be less than 40 years. In yet other examples, the dissolution time may be any value in a range between 1 s and 40 year. In some embodiments, it may be critical that the dissolution time is between 1 year and 30 years to facilitate the dissolution of the encapsulating layer after the carbon dioxide has been injected in the underground aquifer 106.

[0044] In some embodiments, the dissolution property may be based on a triggering event. Basing the dissolution property on a triggering event may facilitate controlled dissolution or breaking down of the encapsulating layer. The triggering event may be any triggering event. For example, the triggering event may include a sonic pulse, a seismic pulse, an electromagnetic pulse, an electrical current, pH level, contact with water (and not supercritical carbon dioxide), any other triggering event, and combinations thereof. Breaking down the encapsulating layer using a triggering event may help to prevent the premature exposure of the bacteria to the underground aquifer 106, thereby maintain a fluid path through the underground aquifer 106 away from the injection site 110. Tailoring the dissolution property to the particular conditions and/or triggering events may allow the operator to fine-tune the timing of the dissolution or breaking down of the encapsulating layer.

[0045] In accordance with at least one embodiment of the present disclosure, the delayed immobilization injection 122 may include a nutrient. The nutrient may include any nutrient that may be metabolized or otherwise utilized by the carbonate-forming bacteria. In some embodiments, the nutrient may include a catalyst that may catalyze the formation of the carbonate. The underground aquifer 106 and the fluids therein may not include sufficient nutrients for the carbonate-forming bacteria to metabolize and generate the calcium carbonate. Including the nutrient with the delayed immobilization injection 122 may provide the carbonate-forming bacteria with sufficient nutrients to immobilize the carbon dioxide in the underground aquifer 106. The nutrient may include any nutrient. For example, the nutrient may include carbon sources (e.g., glucose, maltose, lactose, fructose, sucrose, acetate, L-proline, L-alanine), terminal electron acceptors (e.g., oxygen, nitrate, sulphate, Fe3-, fumarate), phosphate, potassium, sulfur, calcium trace elements, booster nutrients (e.g., L-methionine, L-cysteine, thiamine, nicotinic acid), urea (CO(NH2)2), ammonia (NH3), any other nutrient, and combinations thereof [0046] In some embodiments, the carbonate-forming bacteria may form the carbonate in the presence of an enzyme. The enzyme may include any enzyme, such as urease, carbonic anhydrase, any other enzyme, and combinations thereof. The enzyme may be inserted into the aquifer at any time. For example, the enzyme may be inserted into the aquifer simultaneously with the nutrient. In some examples, the enzyme may be inserted -12-into the aquifer by itself, or without any nutrients. In this example, the enzyme may still be encapsulated for a delayed or slow release. In some examples, the enzyme may be inserted into the aquifer with the carbonate-forming bacteria. In some examples, the enzyme may be inserted into the aquifer simultaneously with the nutrient and the carbonate-forming bacteria. In some embodiments, the enzyme is encapsulated in the encapsulating materials discussed herein. For example, the enzyme may be encapsulated in the encapsulating material. In some examples, the enzyme may be encapsulated with the nutrient. In some examples, the enzyme may be encapsulated with the carbonate-forming bacteria. In some examples, the enzyme may be encapsulated with the nutrient and the carbonate-forming bacteria. In some embodiments, the enzyme may catalyze the precipitation of the carbonate in the underground aquifer. In some embodiments, the enzyme may catalyze the precipitation of the carbonate based on conditions generated by the carbonate-forming bacteria or other bacteria.

[0047] In some embodiments, the delayed immobilization injection 122 may include sufficient nutrients to immobilize all of the carbon dioxide injected into the underground aquifer 106. In this manner, all, or substantially all, of the carbon dioxide in the underground aquifer 106 may be immobilized by the injected bacteria.

[0048] I think the intent here is to differentiate between the cation (say calcium) and the carbonate. We want the carbonate to come from the dissolved and hydrolysed carbon dioxide, otherwise there is no net carbon capture. In some embodiments, the delayed immobilization injection 122 may include a calcium-ion source (such as calcium chloride). The calcium-ion source may be a source for positive ions that may be used to form the carbonate. For example, the calcium-ion source may include a calcium-ion source, which may be used to form calcium carbonate. For example, the delayed immobilization injection 122 may include calcium ions dissolved in the fluid medium of the delayed immobilization injection 122. This may provide the carbonate-forming bacteria calcium ions to generate calcium carbonate. In some embodiments, the calcium-ion source may be provided by the dissolved carbon dioxide in the aquifer water. The dissolution of carbon dioxide in water may take the form of: CO2 + H2O <-> H+ + HCO3 (pH < 8) CO2 + OH-<-* HCO3 (pH > 10) [0049] In accordance with at least one embodiment of the present disclosure, the delayed immobilization injection 122 includes the carbon dioxide, the carbonate-forming bacteria, and the nutrient. In this manner, the carbonate-forming bacteria and the nutrient may be advanced through the underground aquifer 106 with the carbon dioxide plume 118. In some embodiments, the delayed immobilization injection 122 includes the carbonate-forming bacteria and the nutrient and may be injected into the underground aquifer 106 after the carbon dioxide. This may allow the operator to inject the carbonate-forming bacteria into the underground aquifer 106 at any time, thereby forming the calcium carbonate at pre-determined locations and/or in a pre-determined pattern within the underground aquifer 106.

[0050] FIG. 2 is a schematic representation of a bacterial carbon dioxide immobilization system 200, according to at least one embodiment of the present disclosure. The bacterial carbon dioxide immobilization system 200 may include a brine 224. The brine 224 may be the fluid that is located within the underground aquifer. Carbonate-forming bacteria 226 may be located within the brine 224. The carbonate-forming bacteria 226 may be encapsulated in an encapsulating layer 228. As discussed herein, the encapsulating layer 228 may help to isolate the carbonate-forming bacteria 226 from the brine 224. This may help to prevent the carbonate-forming bacteria 226 from contacting the brine 224 and begin forming a carbonate.

[0051] In some embodiments, the carbonate-forming bacteria 226 may be encapsulated within the encapsulating layer 228 with the nutrient. For example, the encapsulating layer 228 may be formed around the carbonate-forming bacteria 226 and the nutrient. In this manner, the carbonate-forming bacteria 226 may have ready access to a nutrient when the encapsulating layer 228 breaks apart and the carbonate-forming bacteria 226 is exposed to the brine 224.

[0052] The brine 224 may include a carbon dioxide plume 218. The carbon dioxide plume 218 may be formed from supercritical carbon dioxide that is not dissolved within the brine 224. Carbon dioxide from within the carbon dioxide plume 218 may be dissolved into the brine 224 to form a carbon dioxide-rich brine 230.

[0053] When the encapsulating layer 228 breaks apart, an exposed bacterium 232 may be exposed to the brine 224. The exposed bacteria 232 may be in contact with the carbon dioxide-rich brine 230 and, through metabolism of the nutrient, the exposed bacterium 232 may form a calcite grain 234 using dissolved calcium ions in the carbon dioxide-rich brine 230. In this manner, the bacterial carbon dioxide immobilization system 200 may immobilize the carbon dioxide in the brine 224.

[0054] FIG. 3-1 is a schematic representation of a bacterial carbon dioxide immobilization system 300, according to at least one embodiment of the present disclosure. The bacterial carbon dioxide immobilization system 300 includes an underground aquifer 306. Carbon dioxide may be injected into the underground aquifer 306 through an injection wellbore 302 using an injection system 312. The injection system 112 may include pump 314 connected to injection pipes 316 that are inserted into the injection wellbore 302.

[0055] Carbon dioxide may be injected into the underground aquifer 306 at an injection site 310.This may result in a carbon dioxide plume (collectively 318) that extends from the injection site 310. As discussed herein, the underground aquifer 306 is covered by an impermeable upper layer 308. Because the carbon dioxide in the carbon dioxide plume 318 has a lower density than the water in the underground aquifer 306, the carbon dioxide plume 318 may be skewed and/or deflected toward the impermeable upper layer 308.

[0056] As discussed herein, the injection system 312 may inject a delayed immobilization injection 322 into the underground aquifer 306. The delayed immobilization injection 322 may include carbonate-forming bacteria and nutrients.

[0057] In the view shown in FIG. 3-1, the injection system 312 has injected the carbon dioxide and the delayed immobilization injection 322 for a first injection time, resulting in a first carbon dioxide plume 318-1 having a first size and extents. Differing geologic conditions of the underground aquifer 306 may cause different shapes of carbon dioxide plumes 318. For example, as may be seen, the first carbon dioxide plume 318-1 has a different size and extents than the carbon dioxide plume 118 of FIG. 1.

[0058] In some embodiments, the first carbon dioxide plume 318-1 may include the entirety of the carbon dioxide intended to be inserted into the underground aquifer 306. Conventionally, without the encapsulating layer surrounding the carbonate-forming bacteria, the carbonate-forming bacteria may begin forming carbonates upon injection into the underground aquifer 306. The carbonates may fill the voids in the underground aquifer 306 at the first carbon dioxide plume 318-1, including at the boundary between the supercritical carbon dioxide in the first carbon dioxide plume 318-1 and the water of the underground aquifer 306. This may reduce or block the fluid path further into the underground aquifer 306, thereby limiting the amount of carbon dioxide that may be injected in the underground aquifer 306.

[0059] In accordance with at least one embodiment of the present disclosure, the first carbon dioxide plume 318-1 may include the delayed immobilization injection 322. This may delay contact of the carbonate-forming bacteria with the water in the underground aquifer 306. In this manner, the carbonate-forming bacteria may not form carbonate in the underground aquifer 306 until the dissolution time has passed and/or the trigger event has occurred. In this manner, the fluid path into the underground aquifer 306 may remain open.

[0060] In FIG. 3-2, the extent of the carbon dioxide plume 318 has extended to the second carbon dioxide plume 318-2. The second carbon dioxide plume 3 I 8-2 may extend further into the underground aquifer 306. In some embodiments, the second carbon dioxide plume 318-2 has extended into the underground aquifer 306 until all of the predetermined amount of carbon dioxide has been injected into the underground aquifer 306. In some embodiments, the second carbon dioxide plume 318-2 has extended into the underground aquifer 306 until a threshold amount of carbon dioxide has been injected into underground aquifer 306.

[0061] When the carbon dioxide plume 318 has reached the second carbon dioxide plume 318-2 shown, the encapsulating layer surrounding the carbonate-forming bacteria may be dissolved and/or broken apart. For example, as discussed herein, the encapsulating layer may be configured to dissolve after the dissolution time. The extents of the second carbon dioxide plume 318-2 may be based on the dissolution time.

[0062] In some examples, the encapsulating layer is configured to dissolve after a triggering event. For example, when the amount of carbon dioxide used to form the second carbon dioxide plume 318-2 is injected into the underground aquifer 306, a triggering event may be implemented. For example, the operator may insert a triggering device into the injection pipes 316. The triggering device may include a sonic emitter that may emit a sonic pulse into the underground aquifer 306 to break apart the encapsulating layer. In some examples, the triggering device may include a seismic emitter, such as an explosive charge, that may emit a seismic pulse into the underground aquifer 306 to break apart the encapsulating layer. In some examples, the triggering device may include an electric current emitter, which may emit an electric current into the underground aquifer 306 to break apart the encapsulating layer. In this manner, the operator may cause the carbonate-forming bacteria to begin forming carbonate at any time. For example, the operator may cause the carbonate-forming bacterial to begin forming carbonate when all of the carbon dioxide intended to be injected into the underground aquifer 306 has been injected.

[0063] In some embodiments, all of the carbonate-forming bacteria inserted into the underground aquifer 306 have the same dissolution time and/or triggering event. As the carbon dioxide is inserted into the underground aquifer 306, the carbonate-forming bacteria may be subsequently exposed to the underground aquifer 306. This may cause the dissolution time to begin when the carbonate-forming bacteria enters the underground aquifer 306 at the injection site 310. In this manner, the encapsulating layer may be dissolved at the same rate as the insertion rate into the underground aquifer 306. This may result in the encapsulating layer further from the injection site 310 dissolving first, and the encapsulating layer closer to the injection site 310 dissolving last.

100641 In some embodiments, the bacterial carbon dioxide immobilization system 300 may include multiple batches of the delayed immobilization injection 322. For example, a first batch of the delayed immobilization injection 322 may have a first encapsulating layer and a second batch of the delayed immobilization injection 322 may have a second encapsulating layer. The first encapsulating layer may have a first dissolution time and the second encapsulating layer may have a second dissolution time. In some embodiments, the first dissolution time and the second dissolution time may be different. The first dissolution time and the second dissolution time may be configured to dissolve the encapsulating layer simultaneously or approximately simultaneously. In this manner, the entirety of the carbon dioxide in the carbon dioxide plume 318 may be immobilized simultaneously or approximately simultaneously. In this manner, the exposed carbonate-forming bacteria in the carbon dioxide plume 318 may begin forming calcium carbonate simultaneously or approximately simultaneously. This may help to prevent the fluid paths through the underground aquifer 306 from being blocked off due to the formation of calcite prior to the injection of the entirety of the predetermined quantity of carbon dioxide into the underground aquifer 306.

[0065] FIG. 4 and 5 are flowcharts of a method for immobilizing carbon dioxide in an aquifer in an underground environment, in accordance with at least one embodiment of the present disclosure. One or more embodiments can also be described in terms of flowcharts comprising acts for accomplishing a particular result, as shown in FIG. 4 and 5. FIG. 4 and 5 may be performed with more or fewer acts. Further, the acts may be performed in differing orders. Additionally, the acts described herein may be repeated or performed in parallel with one another or parallel with different instances of the same or similar acts.

[0066] As mentioned, FIG. 4 illustrates a flowchart of a series of acts or a method 436 for immobilizing carbon dioxide in an aquifer in an underground environment, according to at least one embodiment of the present disclosure. While FIG. 4 illustrates acts according to one embodiment, alternative embodiments may omit, add to reorder, and/or modify any of the acts shown in FIG. 4. The acts of FIG. 4 can be performed as part of a method. In some embodiments, a system can perform the acts of FIG. 4.

[0067] An operator may inject carbon dioxide into an underground aquifer at 438. As discussed herein, the operator may inject supercritical carbon dioxide into the underground aquifer. The operator may further inject a nutrient in the underground aquifer at 440. The operator may inject carbonate-forming bacteria into the underground aquifer at 442. The carbonate-forming bacteria may be configured to convert the nutrient and carbon dioxide to a carbonate. In some embodiments, the carbonate-forming bacteria is a means for forming carbonate in the aquifer.

[0068] In accordance with at least one embodiment of the present disclosure, the carbonate-forming bacteria may be encapsulated in an encapsulating layer. The encapsulating layer may be configured to delay exposure of the carbonate-forming bacteria to water in the aquifer. In some embodiments, the encapsulating layer may be a means for delaying exposure of the carbonate-forming bacteria to the water in the aquifer.

[0069] In some embodiments, injecting the nutrient and the carbonate-forming bacteria may include flowing the nutrient and the carbonate-forming bacteria away from the injection site. In some embodiments, the encapsulating layer is configured to dissolve when the carbonate-forming bacteria and the nutrient are flowed a threshold distance away from the injection site. This may facilitate formatting of the carbonate at a distance away from the injection site. The threshold distance may be any distance. For example, the threshold -18-distance may be a distance may be sufficient to maintain the flow of the carbon dioxide into the aquifer.

[0070] In accordance with at least one embodiment of the present disclosure, the carbonate-forming bacteria may include a first carbonate-forming bacteria, or a first set of carbonate-forming bacteria. The first set of carbonate-forming bacteria may be injected into the underground aquifer at a first time. The carbonate-forming bacteria may include a second set of carbonate-forming bacteria. The second set of carbonate-forming bacteria may be injected into the underground aquifer at a second time. The second time may be after the first time. The first set of carbonate-forming bacteria may begin forming carbonate at a different time than the second set of carbonate-forming bacteria. As discussed herein, this may allow the operator to tailor the time at which the carbonate is formed to the particular underground aquifer and/or amount of carbon dioxide to be injected.

[0071] The first set of carbonate-forming bacteria may have a first encapsulating layer configured to dissolve at a first dissolution time. The second set of carbonate-forming bacteria may be encapsulated in a second encapsulating layer configured to dissolve at a second dissolution time. The first dissolution time may be approximately the same as the second dissolution time. This may facilitate simultaneous or approximately simultaneous dissolution exposure of the first set of carbonate-forming bacteria and the second set of carbonate-forming bacteria to the water in the underground aquifer.

[0072] As mentioned, FIG. 5 illustrates a flowchart of a series of acts or a method 544 for immobilizing carbon dioxide in an aquifer in an underground environment, according to at least one embodiment of the present disclosure. While FIG. 5 illustrates acts according to one embodiment, alternative embodiments may omit, add to, reorder, and/or modify any of the acts shown in FIG. 5. The acts of FIG. 5 can be performed as part of a method. In some embodiments, a system can perform the acts of FIG. 5.

[0073] An operator may, at a first time, inject a first delayed immobilization injection into an underground aquifer at 546. The first delayed immobilization injection may include first carbonate-forming bacteria and first nutrients. The first carbonate-forming bacteria and the first nutrients may be encapsulated in a first encapsulating layer. The operator may, at a second time, inject a second delayed immobilization injection into the underground aquifer at 568. The second delayed immobilization injection may include second -19-carbonate-forming bacteria and second nutrients. The second carbonate-forming bacteria and the second nutrients may be encapsulated in a second encapsulating layer. In some embodiments, injecting the second delayed immobilization injection may cause the first delayed immobilization injection to travel further into the underground aquifer.

[0074] At a third time, the first encapsulating layer and the second encapsulating layer may dissolve at 550. This may cause the first carbonate-forming bacteria and the second carbonate-forming bacteria to be exposed to the water of the formation. This may cause the first and second carbonate-forming bacteria to begin forming carbonates. In some embodiments, the first encapsulating layer and the second encapsulating layer dissolve simultaneously or approximately simultaneously. In some embodiments, causing the first encapsulating layer and the second encapsulating layer to dissolve may include triggering a triggering event in the underground aquifer. As discussed in further detail herein, the triggering event may include an event that causes the encapsulating layers to dissolve.

[0075] The embodiments of the bacterial carbon dioxide immobilization system have been primarily described with reference to wellbore drilling operations; the bacterial carbon dioxide immobilization systems described herein may be used in applications other than the drilling of a wellbore. In other embodiments, bacterial carbon dioxide immobilization systems according to the present disclosure may be used outside a wellbore or other downhole environment used for the exploration or production of natural resources. For instance, bacterial carbon dioxide immobilization systems of the present disclosure may be used in a borehole used for placement of utility lines. Accordingly, the terms "wellbore," "borehole" and the like should not be interpreted to limit tools, systems, assemblies, or methods of the present disclosure to any particular industry, field, or environment.

[0076] One or more specific embodiments of the present disclosure are described herein. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual embodiment may be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous embodiment-specific decisions will be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one embodiment to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0077] Additionally, it should be understood that references to "one embodiment" or "an embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. For example, any element described in relation to an embodiment herein may be combinable with any element of any other embodiment described herein. Numbers, percentages, ratios, or other values stated herein are intended to include that value, and also other values that are "about" or "approximately" the stated value, as would be appreciated by one of ordinary skill in the art encompassed by embodiments of the present disclosure. A stated value should therefore be interpreted broadly enough to encompass values that are at least close enough to the stated value to perform a desired function or achieve a desired result. The stated values include at least the variation to be expected in a suitable manufacturing or production process, and may include values that are within 5%, within 1%, within 0.1%, or within 0.01% of a stated value.

[0078] A person having ordinary skill in the art should realize in view of the present disclosure that equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and alterations may be made to embodiments disclosed herein without departing from the spirit and scope of the present disclosure. Equivalent constructions, including functional "means-plus-function" clauses are intended to cover the structures described herein as performing the recited function, including both structural equivalents that operate in the same manner, and equivalent structures that provide the same function. It is the express intention of the applicant not to invoke means-plus-function or other functional claiming for any claim except for those in which the words 'means for' appear together with an associated function. Each addition, deletion, and modification to the embodiments that falls within the meaning and scope of the claims is to be embraced by the claims.

[0079] The tenns "approximately," "about," and "substantially" as used herein represent an amount close to the stated amount that is within standard manufacturing or -21 -process tolerances, or which still performs a desired function or achieves a desired result. For example, the terms "approximately," "about," and "substantially" may refer to an amount that is within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of a stated amount. Further, it should be understood that any directions or reference frames in the preceding description are merely relative directions or movements. For example, any references to "up" and -down" or "above" or "below" are merely descriptive of the relative position or movement of the related elements.

[0080] The present disclosure may be embodied in other specific forms without departing from its spirit or characteristics. The described embodiments are to be considered as illustrative and not restrictive. The scope of the disclosure is, therefore, indicated by the appended claims rather than by the foregoing description. Changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

-22 -

Claims (20)

1. CLAIMSWhat is claimed is: 1. A method for mmobil z ng carbon dioxide in an underground aquifer, the method comprising: injecting carbon dioxide in the underground aquifer; injecting a nutrient in the underground aquifer; and injecting carbonate-forming bacteria configured to form a carbonate from the nutrient and carbon dioxide, the carbonate-forming bacteria encapsulated with an encapsulating layer.
2. 2. The method of claim I, wherein the nutrient includes urea.
3. 3. The method of claim I, further comprising flowing the carbonate-forming bacteria, the nutrient, and the carbon dioxide away from an injection site in the underground aquifer.
4. 4. The method of claim 3, wherein the encapsulating layer is configured to dissolve when the carbonate-forming bacteria, the nutrient, and the carbon dioxide are flowed a threshold distance away from the injection site.
5. 5. The method of claim 1, wherein the carbonate-forming bacteria includes first carbonate-forming bacteria and injecting the first carbonate-forming bacteria includes injecting the first carbonate-forming bacteria at a first time, and further comprising injecting a second carbonate-forming bacteria at a second time after the first time.
6. 6. The method of claim 5, wherein the encapsulating layer is a first encapsulating layer, and wherein the second carbonate-forming bacteria is encapsulated with a second encapsulating layer, the first encapsulating layer configured to dissolve at a first dissolution time and the second encapsulating layer configured to dissolve at a second dissolution time.
7. 7. The method of claim 6, wherein the first dissolution time is approximately the same as the second dissolution time.
8. 8. A bacterial carbon dioxide immobilization system for an underground aquifer, the bacterial carbon dioxide immobilization system comprising: -23 -carbonate-forming bacteria configured to form a carbonate from a nutrient and carbon dioxide; and an encapsulating layer encapsulating the carbonate-forming bacteria, the encapsulating layer having a dissolution property to dissolve after a dissolution time.
9. 9. The bacterial carbon dioxide immobilization system of claim 8, wherein the dissolution property is based on a triggering event.
10. 10. The bacterial carbon dioxide immobilization system of claim 9, wherein the triggering event includes at least one of a sonic pulse, a seismic pulse, an electromagnetic pulse, an electrical current, pH level, or contact with water.
11. Ii. The bacterial carbon dioxide immobilization system of claim 8, wherein the nutrient includes urea.
12. 12. The bacterial carbon dioxide immobilization system of claim 8, wherein the nutrient is encapsulated in the encapsulating layer.
13. 13. The bacterial carbon dioxide immobilization system of claim 8, wherein the encapsulating layer is impermeable to water.
14. 14. The bacterial carbon dioxide immobilization system of claim 8, wherein the carbonate-forming bacteria includes at least one of Sporosarcina pasteurii, Bacillus pasteurii, or Bacillus sphaericus.
15. 15. The bacterial carbon dioxide immobilization system of claim 8, further comprising a calcium-ion source.
16. 16. The bacterial carbon dioxide immobilization system of claim 15, wherein the calcium-ion source includes calcium chloride.
17. 17. A method for immobilizing carbon dioxide in an underground aquifer, the method comprising: at a first time, injecting a first delayed immobilization injection into the underground aquifer, the first delayed immobilization injection including first carbonate-forming bacteria and first nutrients, the first carbonate-forming bacteria and the first nutrients encapsulated in a first encapsulating layer; -24 -at a second time, injecting a second delayed immobilization injection into the underground aquifer, the second delayed immobilization injection including second carbonate-forming bacteria and second nutrients, the second carbonate-forming bacteria and the second nutrients encapsulated in a second encapsulating layer; and at a third time, causing the first encapsulating layer and the second encapsulating layer to dissolve and expose the first carbonate-forming bacteria and the second carbonate-forming bacteria to the underground aquifer.
18. 18. The method of claim 17, wherein injecting the second delayed immobilization injection causes the first delayed immobilization injection to travel further into the underground aquifer.
19. 19. The method of claim 17, wherein the first encapsulating layer and the second encapsulating layer dissolve approximately simultaneously.
20. 20. The method of claim 17, wherein the first encapsulating layer is different than the second encapsulating layer.