Scholarly article on topic 'Carbon microbubbles sequestration: A novel technology for stable underground emplacement of greenhouse gases into wide variety of saline aquifers, fractured rocks and tight reservoirs'

Carbon microbubbles sequestration: A novel technology for stable underground emplacement of greenhouse gases into wide variety of saline aquifers, fractured rocks and tight reservoirs Academic research paper on "Environmental engineering"

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{"Carbon dioxide" / "Greenhouse gas" / Mitigation / Microbubble / CCS / Buoyancy / "Fluid fracturing" / earthquake}

Abstract of research paper on Environmental engineering, author of scientific article — Hitoshi (Gene) Koide, Ziqiu Xue

Abstract A novel economic leak-free underground injection technology of greenhouse gas—the carbon (CO2) microbubbles sequesrtrationcan bring the deep reduction of greenhouse gas emission into reality around the world. The atomized foams of CO2 gas, CO2 supercritical fluid or CO2 liquid are dispersed deep into tiny pores of wide variety of underground rocks for virtually permanent storage. The gas microbubbles injection may be effective also for the EOR and EGR in tight rocks such as oil shale and gas shale. Combined effect of hardly buoyant carbon microbubbles, heavy carbon dioxide solution and various trapping mechanisms makes the carbon microbubbles sequestration stable and leak-free in wide variety of geology. The carbon microbubbles injection is suitable also to small scale sequestration of greenhouse gases in the coming hydrogen society as well as large scale CO2 storage from big coal-fired power plants. The dispersion and dilution of CO2 in large volume of deep groundwater and rocks by scattered relatively small-scale carbon microbubbles injections are an earth-friendly strategy of greenhouse gas sequestration. The flexibility of site selection makes the source-sink matching much easier for the carbon microbubbles sequestration than conventional direct large-scale injection practices. As we can find the suitable site for the storage near of many large sources of carbon dioxide, the carbon microbubbles sequestration is practically energy-saving and cost-effective greenhouse gas reduction method in many regions. The carbon microbubbles injection can produce the reductive geochemical and biological environments in tiny pores of igneous (especially oceanic) rocks and sequestrate CO2 into carbonates, organics and methane in the similar mechanism to the Early Archaean earth. The autogenous sealing by carbonate trapping and by hydrate trapping provides the leak proof storage of anthropogenic CO2 in the deep oceanic crust. The carbon microbubbles sequestration (CMS) provides the economig leak-free option of carbon capture and storage (CCS) and a break-through for the prevention of global warming.

Academic research paper on topic "Carbon microbubbles sequestration: A novel technology for stable underground emplacement of greenhouse gases into wide variety of saline aquifers, fractured rocks and tight reservoirs"

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Energy Procedia 1 (2009) 3655-3662

www.elsevier.com/locate/procedia

GHGT-9

Carbon microbubbles sequestration: a novel technology for stable underground emplacement of greenhouse gases into wide variety of saline aquifers, fractured rocks and tight reservoirs

Hitoshi (Gene) Koidea*, Ziqiu Xueb

aWaseda University, RISE, 17Kikui-cho, Shinjuku, Tokyo 162-0044, Japan bKyoto University, Department ofCivil and Earth Resources Engineering, Kyoto 615-8540, Japan

Abstract

A novel economic leak-free underground injection technology of greenhouse gas - the carbon (CO2) microbubbles sequesrtration-can bring the deep reduction of greenhouse gas emission into reality around the world. The atomized foams of CO2 gas, CO2 supercritical fluid or CO2 liquid are dispersed deep into tiny pores of wide variety of underground rocks for virtually permanent storage. The gas microbubbles injection may be effective also for the EOR and EGR in tight rocks such as oil shale and gas shale. Combined effect of hardly buoyant carbon microbubbles, heavy carbon dioxide solution and various trapping mechanisms makes the carbon microbubbles sequestration stable and leak-free in wide variety of geology. The carbon microbubbles injection is suitable also to small scale sequestration of greenhouse gases in the coming hydrogen society as well as large scale CO2 storage from big coal-fired power plants.

The dispersion and dilution of CO2 in large volume of deep groundwater and rocks by scattered relatively small-scale carbon microbubbles injections are an earth-friendly strategy of greenhouse gas sequestration. The flexibility of site selection makes the source-sink matching much easier for the carbon microbubbles sequestration than conventional direct large-scale injection practices. As we can find the suitable site for the storage near of many large sources of carbon dioxide, the carbon microbubbles sequestration is practically energy-saving and cost-effective greenhouse gas reduction method in many regions. The carbon microbubbles injection can produce the reductive geochemical and biological environments in tiny pores of igneous (especially oceanic) rocks and sequestrate CO2 into carbonates, organics and methane in the similar mechanism to the Early Archaean earth. The autogenous sealing by carbonate trapping and by hydrate trapping provides the leak proof storage of anthropogenic CO2 in the deep oceanic crust.

The carbon microbubbles sequestration (CMS) provides the economig leak-free option of carbon capture and storage (CCS) and a break-through for the prevention of global warming. (c 2009 Elsevier Ltd. All rights reserved.

Keywords: carbon dioxide; greenhouse gas; mitigation; microbubble;CCS; buoyancy; fluid fracturing, earthquake

* Corresponding author. Tel.: 81-3-3987-2778; fax: 81-3-3987-2778.

E-mail address: MXE02263@nifty.com URL: http://homepage3.nifty.com/zeroemission/e.htm

doi:10.1016/j.egypro.2009.02.162

1. Near Source Geological Sequestration of CO2

A novel economic leak-free underground injection technology of greenhouse gas - the carbon (CO2) microbubbles sequesrtration- [1] is proposed in this paper to bring the deep reduction of greenhouse gas emission into reality around the world (Fig.1). One of the authors proposed the CO2 saline aquifer storage system 16 years ago in the first ICCDR(GHGT-l) conference in Amsterdam[2]. For the first time, he and co-authors of the first paper designed the ferst comprehensive CCS(carbon capture and storage) system and found that world sedimentary basins can accommodate 320Gtons of CO2 in solution at the reasonable costs even in their conservative estimation. The water-alternating-gas (WAG) injection practices were originally assumed to dissolve CO2 swiftly and to restrict sizes of buoyant CO2 bubbles. In this paper, the authors introduce a new more efficient and leak-free CO2 microbubbles injection (Fig. 1,Fig.2) applicable in the world sedimentary basins and in other various rocks including igneous rocks.

The most serious problem of the extensive worldwide deployment of carbon capture and sequestration (CCS) to prevent the global warming is the mismatching between sources and sinks. The large body of greenhouse gas and supercritical CO2 fluid can be stored only under special trapping geological structures such as domal sedimentary formations that contain perfectly impermeable caprocks (clay, shale, etc.) and porous reservoir rocks (sandstone, conglomerate, etc.). The suitable geological structures to store huge mass of buoyant fluids is large softly consolidated and suitably folded sedimentary basins that contain domal structures- possible natural gas and oil reservoirs. Many greenhouse gas emitters such as fossil-fueled power plants situate far from the suitable geological structures that can store large mass of buoyant CO2. In this paper, the novel "carbon microbubbles sequestration technology" [1] is introduced to emplace large amount of CO2 safely and economically even into incompletely confined flat aquifers, monoclinal aquifers, synclinal sedimentary basins, igneous rocks, metamorphic rocks, densely fractured rocks and other ordinary underground rocks without the special geological structures that can trap large buoyant bodies of the greenhouse gas.

2. Pressure Instability due to the Large Buoyant Bubble of CO2

Rapid underground injection of large amount of CO2 forms a big underground CO2 bubble that is actually a region of connected pore spaces occupied by CO2-dominant fluid in the reservoir rocks. The pure CO2 fluid is gas or liquid or supercritical fluid dependent on the pressure and temperature in the reservoir rocks. As the CO2 fluid ( gas or liquid or supercritical fluid) is lighter than the groundwater at the ordinary underground pressure and temperature condition, a big underground CO2 bubble gains the big buoyant force (Fig.3, Fig.4). The plume-like uprising of large CO2 bubble was observed seismically in the highly permeable sandy aquifer in the first large-scale CO2 sequestration

CO2 injection

Water injection

CO2 microbubbles generation at an adequate depth of injection well

Fig. 1 Carbon microbubbles sequestration.

project at Sleipner, Norway [3]. The perfect cover of underground geological structure such as a dome of caprock is necessary for safe storage of large buoyant body of CO2 fluid (Fig.3,Fig.4). Natural gas and oil deposits have long-term geological traps that have contained the buoyant fluids longer than several million years. It was also suggested that undetected small gaps of shale layers provided pathways of CO2 plume in the Sleipner aquifer [4]. No effective technologies have not yet developed to check out the completeness of caprocks that have not been proven naturally. Abandoned production wells, exploration boreholes, artificial fractures by extraction-caused subsidence may form pathways for CO2 leakage even in naturally proven caprocks.

The large excess fluid pressure builds up at the top of large bubble of CO2 fluid due to difference of density between the inside and outside of bubble (Fig.4). The CO2 fluid (gas or liquid or supercritical fluid) inside of the bubble is lighter than the groundwater outside of the bubble at the ordinary underground pressure and temperature condition. The pressure instability is inevitable around large buoyant bubble. The excess pressure in the CO2 reservoir cannot exceed the interfacial threshold pressure for the CO2 breakthrough of caprocks(Fig.4). The fluid fracturing of caprocks and fluid-induced earthquakes may occur at the top of large CO2 bubble if the excess pressure due to buoyancy reduces the effective stress enough to cause the shear instability of underground rocks (Fig.4). The fluid fracturing and induced earthquakes are unlikely around microbubbles, because the very small excess fluid pressure only build up at the top of microbubbles.

3. Carbon Microbubbles Injection for Stable Saline Aquifer Storage of CO2 (Fig.5)

The newly proposed technology is the carbon microbubbles injection that can drastically reduce the size of CO2 bubbles. The novel carbon microbubbles injection technology (Fig.1) can generate numerous uniform tiny bubbles of carbon dioxide and/or other greenhouse gases smaller than some ten micrometers in diameter in water (Fig.2), although our experiments are still in the early stage. The word "microbubble" is commonly used in this paper, but the pure CO2 may be gas or liquid in the injection well but usually supercritical fluid in aquifers deeper than about 800m (Fig.2). The mixture of the CO2 microbubbles and water is injected into tiny pore spaces of underground rocks through the wall of deep borehole (Fig.1). The carbon microbubbles of diameters less than several 10 micrometers tend to shrink and quickly to solve into water. The hardly buoyant greenhouse gas microbubbles do not tend to join

The big bubble goes up rapidly audi spreads uder the cap.

Aquifer

Fig. 2 Microbubbles of supercritical CO2 (average diameter: 40 ¡i m).

The microbubble hardly goes up aud shrinks.

Fig. 3 The big bubbles of CO2 fluid (gas, supercritical fluid, liquid) go up by the buoyant force, while tiny microbubbles are hardly buoyant, shrink and do not coalesce into a big bubble. Microbubbles of can be emplaced stably into pores and interstices of underground rocks.

together to form large bubbles that have large buoyant force in groundwater (Fig.2). Tiny CO2 microbubbles percolate deep into tiny pores and cracks in the aquifer rocks(Fig.5)[5]. Interfacial force and capillary effect trap many carbon microbubbles in pores of rocks as residual gas (Fig.6). CO2 microbubbles dissolve into the groundwater rapidly at the underground high pressure. The underground injection of dispersed tiny droplets of CO2 liquid is a water-saving version of carbon microbubbles injection technology (see also the related paper[6]). As the CO2 solution is heavier than the primary groundwater, the CO2 solution tends to flow downward. Dispersion of carbon dioxide into underground rocks as microbubbles prevent the plume uprising of large carbon dioxide (gas or

Pressure

Fig. 4 The large excess fluid pressure builds up at the top of large bubble of CO2 fluid due to difference of density between the inside and outside of bubble (Fig.1). The CO2 fluid (gas or liquid or supercritical fluid) is lighter than the groundwater at the ordinary underground pressure and temperature condition. The fluid fracturing of caprocks and fluid-induced earthquakes may occur at the top of large CO2 bubble. The fluid fracturing and induced earthquakes are unlikely around small bubbles, because the small excess fluid pressure only build up at the top of small bubble.

supercritical fluid) bubbles in partially confined aquifers and even in unconfined aquifers. The carbon microbubbles injection accelerates the residual gas (interfacial and capillary effects) trapping, dissolution trapping, and ionization trapping of CO2 for stable saline aquifer storage of CO2 (Fig.6). The natural methane solution deposits (in Chiba, Niigata and Miyazaki prefectures) and natural CO2 solution deposits (at Isobe and Izumi districts) in unconfined saline aquifers in Japan indicate that the long-term CO2 storage in solution is possible in young semi-open unfolded sedimentary basins owing to the dissolution, ionizing and residual gas trapping [2]. The saline aquifer storage of CO2 is the economicaliy prospective option of geological carbon sequestration that has the huge storage potential of three trillion tons of CO2 in solution in the worldwide sedimentary basins [7]. The carbon microbubbles sequestrtion (CMS) in saline aquifers provides the economic option of carbon capture and storage (CCS) for many urban areas and indusitrial areas.

The carbon microbubbles injection is suitable to the small-scale sequestration of greenhouse gases as well as large scale CO2 storage. A large number of relatively small-scale sources of greenhouse gases would be dominant in the coming hydrogen society. The low concentration of CO2 is harmless but has the global greenhouse effect. The dispersion and dilution of CO2 in large volume of deep groundwater and rocks by small-scale carbon microbubbles injection is an essentially safe strategy of greenhouse gas sequestration.

At high pressure, CO2 has much higher solubility than nitrogen and methane. The injection of microbubbles of mixed gas such as flue gas may result in selective dissolution of CO2. The carbon capture by microbubbles without the use of any solvent may relize an efficient and economic option of small-scale CCS. The depth of microbubbles generation in the injection well is important for the efficient separation of CO2.

The permeability of rock is expected to be high for smaller microbubbles than pores of rocks but becomes extremely low for larger bubbles than pores of rocks, although more permeability experiments are needed for various combinations of microbubbles and rocks. Theoretically, suitable microbubbles should be smaller than pores

Water réinjections^ C° injection

Saline aquifer

Aquitard

Microbubbles jection

Fig.5 Carbon microbubbles injection into saline aquifers.

of reservoir rocks but larger than pores of caprocks. Extremely small microbubble - "nanobubbles" - could penetrate into extremely small pores in the oil shale and tight gas reservoirs. The carbon microbubbles injection could be a potent technology for the EOR and EGR in depleted water-driven reservoirs, depleted heavy oil reservoirs, tight reservoirs, oil shale, gas shale etc.

4. Carbon Microbubbles Injection to Stimulate Advanced Sequestration of CO2

The underground carbon microbubbles injection accelerates the geological sequestration mechanisms such as residual gas trapping, dissolution trapping, ionization trapping, mineral trapping, microbial trapping and methanogenesis [8] by dispersion and quick dissolution into groundwater in deep tiny pores in underground rocks (Fig.6, Fig.7). The greenhouse gas microbubbles injection is a favorable tool for the advanced geological and terrestrial sequestration of greenhouse gas. Combined effect of very weak buoyant force of greenhouse gas microbubbles, heavy CO2 solution and various trapping mechanisms makes the carbon microbubbles sequestration stable in wide variety of geological conditions even with some structural imperfection such as depleted oil/gas reservoirs with abandoned wells, barren geological domes with unproven caprocks, faulted anticlines of sedimentary formations, saline aquifers with incomplete caprocks, large horizontal or monoclinal formations, synclinal sedimentary basins, fractured basalt layers, fractured serpentine bodies, fractured igneous bodies etc.

The quick dissolution of CO2 by the carbon microbubble injection forms the region of acidic interstitial water in the underground reservoir rocks around the injection well (Fig.8). The CO2-rich acidic water dissolves the calcite and decomposes feldspars and other minerals in interstices of grains and increases the porosity of rocks. However, further geochemical CO2-water-rock interaction neutralizes and increases pH of water. The cation-rich and CO2-rich water at high pH condition precipitates carbonates and seal autogenously the interstices of rocks, especially of Mg and Fe-rich mafic rocks such as basalt, peridotite, serpentine etc. The autogenously sealed "CO2 capsules" can be formed in large basaltic sheets, ophiolite complex and oceanic crust (Fig.8). The greenhouse gas can be confined in the autogenously sealed "CO2 capsules" permanently.

High temperature and pressure of CO2 microbubbles and brine mixture in tiny pore space of oceanic crust make a similar condition to the early earth's ocean floor nearly 4 billion years ago in extremely small scale. Nakamura and Kato [9] suggested that large amount of CO2 were sunk into the oceanic crust by the intense seafloor hydrothermal alteration in the global carbon cycle in the Early Archaean. The methanogenesis by anaerobic Archaea is expected in the mixture of CO2 microbubbles and brine. The geochemical and biological environment similar to the Early Archaean earth may contribute to the prevention of global warming by the carbon microbubbles injection into the

Fig.6 Microtraps: The tiny CO2 microbubbles percolate deep into tiny pores and cracks in the aquifer rocks. Interfacial force and capillary effect trap many carbon microbubbles in pores of rocks as residual gas.

oceanic basalt. Koide et al. [8] indicated that the CO2 storage in deep subseabed formations is virtually perfectly leak-free due to the hydrate trapping. Goldberg et al. [10] suggested that CO2 sequestration in sediment-covered basalt aquifers on the Juan de Fuca plate offer promising locations to securely accommodate more than a century of future U.S. emissions. The autogenous sealing by carbonate trapping and by hydrate trapping provides the leak-free storage of vast amount of anthropogenic CO2 in the oceanic crust.

5. Conclusion

Although our experiments are in the early stage, the flexibility of sequestration site selection makes the source-sink matching much easier for the carbon microbubbles sequestration than conventional direct injection practices. As we can find the suitable site for sink near of many large sources of carbon dioxide, the carbon microbubbles sequestration is practically energy-saving and cost-effective greenhouse gas reduction method with easy and economical transportation in many regions.

The carbon (CO2) microbubbles sequesrtration is the safe, economic and earth-friendly novel technology for the greenhouse gas sequestration in wide variety of underground rocks and for the EOR and EGR effective even in tight rocks such as oil shale and gas shale. The carbon microbubbles sequestration has possibility to provide a breakthrough for the prevention of global warming, although many experimental data should be collected in laboratories and in situ.

The novel economic leak-free underground injection technology of greenhouse gas - the carbon (CO2) microbubbles sequesrtration- can bring the deep reduction of greenhouse gas emission into reality around the world. The carbon microbubbles sequestration (CMS) provides the economig leak-free option of carbon capture and storage (CCS) and a break-through for the prevention of global warming.

Sequestration

Acceleration by microbubbles injection

Fig.7 Carbon microbubbles accelerates deep underground fixation of CO2

Acknowledgements

The authors thank the Tokyo Gas Co., Ltd. for their support to our experiments. References

1. H.Koide and J.Shinoda, Proc.M.M.I.J. (2007) in Japanese.

2. H.Koide, Y.Tazaki, Y.Noguchi, S.Nakayama, M.Iijima, K.Ito, & Y.Shindo, Energy Conv. & Man.33(1992) 619

3. R.Arts, I.Brevik, O.Eiken, R.Sollie, E.Causse & B.van der Meer, Greenhouse Gas Control Technologies, CSIRO Publishing, Collingwood, Australia (1984) 366.

4. Saline Aquifer CO2 Storage project (SACS) - Best Practice Manual - IEA GHG R&D Programme (2003)

5. T.Suekane, N.H.Thanh, T.Matsumoto, M.Matsuda, M.Kiyota,A.Ousaka, GHGT-9 (2008)

6. S.Uemura., S.Tsushima & S.Hirai, GHGT-9 (2008)

7. H.Koide, Proc. GHGT-4 (1999)201

8. H.Koide, Y.Shindo, Y.Tazaki, M.Iijima, K.Ito, N.Kimura, & K.Omata, Energy Conv. & Man.38Sup.(1997) 2539. K.Nakamura, K. & Y. Kato, Geochimica et Cosmochimica Acta, 68 (2004) 4595.

10. D.S.Goldberg, T.Takahashi & A.L. Slagle, PNAS 105 (2008) 9920.

Autogenous sealii

itogenous sealing

igh^ CO2 microbubbles pH . Acidic water v

y , t x

Maiîc rocks

Basalt Serpentine Ophiolite Oceanic Crust

Fig.8 Autogenous sealing "capsule" formed by CO2 microbubbles injection in mafic rocks (basalt, serpentine, ophiolite complex, oceanic crust etc.).