Method and arrangement for the storage of CO2 dissolved in water and its permanent fixation in geologic formations

0001The invention relates to a method and an arrangement for Storage and permanent fixation of dissolved in water CO₂ leading in formation water geological formations, wherein by a chemical reaction of the CO₂ with minerals in Formation of CO₂ is precipitated in the form of stable minerals.

0002The reduction of anthropogenic CO₂-Eintrages In the Atmosphere is of paramount importance for the development the world's climate. Besides the develop ment of low-emission Power plants is the storage and permanent fixing of CO₂ short in geological formations and medium term important way to achieve the German of the Federal Government formulated objective the reduction of the German CO₂Emissions by 2005 relative to 25% on the year 1990 levels.

0003For storage and fixation of CO₂ in geological Formations are several methods approaches available, which examined and discussed in the past, were. Ultimately, the different approaches are then rated as safe and permanent storage of it CO₂ underground permit:<ul><li>Direct storage of gaseous or supercritical CO₂ in former natural gas reservoirs;</li><li>Physical fixation of CO₂Molecules to Surfaces of organic carbon in the underground (About coals) by adsorption; </li><li>[3], [5] [4], [6]: Chemical reactions of water dissolved CO₂ with appropriate minerals in formation water bearing formations and the associated Binding and precipitation of CO₂ secondary in the form Carbonates.</li></ul>

0004The storage of CO₂ leading in formation water Formations (saline aquifers) changed their hydrodynamic and geochemical equilibrium. In this case, a portion of the dissolved CO in the reservoir₂ under appropriate Conditions permanently as carbonate in the porous Rock matrix of the formation fail. This has due its effect on the porosity strongly influence on the hydraulic conductivity and can affect so the storage properties of the aquifer impact.

0005be for some time worldwide the advantages and disadvantages of different options for CO₂-Deponierung examined. With regard to the requisite Technologies can respect some aspects already existing solutions are resorted, as in the used management of oil and gas deposits will. This applies particularly to the development and Management of suitable gas storage. be present in Norwegian sector of the North Sea ([1] Korbol and Kaddour, 1995) and in the pool in Alberta Canada ([2] Gunter et al., 1996) attempts are made CO₂Gas permanently in deep save formations. Effects of CO₂-Storage on the complex physico-chemical system in a Reservoir may due to the lengthy geochemical examined processes with the help of numerical simulation will. Initial studies on this particular deal the Problem of groundwater contamination as a result of by CO₂-Migration displaced saline fluids Zementationsprozesse in clayey layers over such CO₂Bubbles and the Effects of clay structures to within an aquifer the decrease in the rate of migration of CO₂gas bubbles and the resulting increase of dissolved CO₂ ([3] Johnson et al. 2001; [4] White et al., 2001; [5] &amp; McPherson Lichtner, 2001).

0006In addition, by [6] Xu et al. (2003), the specific Storage of CO₂ by dissolving and precipitating in Minerals bound CO₂ under suitable conditions on Example of a Küstenaquifers in the United States to 10 kg CO₂ per m³Fluid calculated.

0007Starting from this prior art, the invention the object of a process of the aforementioned propose Art, the one about the storage of CO₂allows beyond reducing environmental pollution.

0008This object is the opening paragraph in a process Art achieved in that a formation with such is selected calcium-containing minerals whose solubility increases with decreasing temperature and to precipitate the stable minerals the formation water in the formation is cooled and the heat recovered during cooling to Heating purposes and / or energy is used.

0009The invention makes use the knowledge that it Formations are whose formation water to precipitate stable CO₂ binding minerals need to be refrigerated. Of Furthermore the invention is based on the idea that at the cooling heat released used for energy can be and thus a further burden on the environment by runs. The cooling of the geothernischen due to the Low level warm formation water is carried out by the Entry of water from the lower temperature Earth's surface into the formation, and by promoting warm formation water from the formation to the Earth's surface where the transported from the formation water geothermal for heating and / or used energy use can be.

0010The permanent storage and fixation of CO₂ in Formations underground is by chemically bonding CO₂ in the form of stable minerals, particularly calcium carbonate reached. For the associated chemical reactions therefore come formations with calcium-containing minerals in . Consideration, such as feldspars or sulfates (eg anhydrite: CaSO₄; Gypsum: CaSO₄× H₂O). Particularly useful are anhydrite and gypsum formations.

0011The warm water is the formation anhydrite / gypsum in Rock in chemical equilibrium. Since anhydrite / gypsum respect. the temperature has a retrograde solubility, must hot formation water are cooled. Only in this way can be enriched with calcium sulfate, and then CaCO₃failures. The in cooling the hot formation water Heat recovered may, as in the known systems Geothermal energy is already being practiced for heating purposes, be used or converted into electricity. The use of geothermal energy reduces energy expenditure for cooling the Formation waters. In addition, through the Geothermal energy, an additional, climate-friendly and therefore environmentally desirable effect is achieved.

0012An important feature of mineral invention Conversion of sulfate minerals anhydrite / gypsum is that a resolution of calcium sulfate and subsequent Precipitation of calcium carbonate with a volume reduction accompanied by about 25% for anhydrite and 50% for gypsum. For storage and fixation of CO₂ through the formation Precipitation of calcium carbonate it is therefore advantageous, because the conversion process does not seal the formation and in this way the process of CO₂storage for Standstill brings; Rather, the porosity of rises Rock matrix of the formation during the application of the The inventive method of continuously even so with CO₂ supersaturated formation waters, particularly achieve sols, always more distant parts of the formation can.

0013In the cooled, with sulfate minerals, especially anhydrite / Gypsum enriched formation waters can CO₂ as CaCO₃be committed when the formation waters are alkaline (pH 6-7). If the formation water is not alkaline already (PH 6-7), it is according to the invention by introducing alkaline substances to an alkaline pH brought.

0014<b>figure 2</b> illustrates a model calculation for CO₂-Storage and fixing than CaCO₃ by the reaction of CO₂ with plaster along a pH gradient (initial condition: P_CO2 = 3 atm). Calculations show that in this case for 1 mole of CO₂1.7 mol of (OH)^- required are. The alkalinity is thus a limiting factor for the effectiveness of the mineral conversion process.

0015Particularly suitable formations for carrying out the The inventive method are deep, water-bearing Layers (aquifers) with sulfate minerals such as anhydrite or Plaster. Compared to other geological formations (z. B. depleted oil and Ergaslagerstätten) They provide the Advantage that they can be found widely and easily can be developed. For this reason, let the Transport routes from the site of CO₂Production (power plant) to We make short for formation and thus are represented by the Transport costs minimal.

0016Application of the method according to the invention is in particular, in spatial proximity to a geothermal Heating system into consideration, in the 50-100 m³implemented / h water will.

0017The large sedimentary basins, such. As in Northern Germany, principle for an underground storage of CO₂suitable, since they consist of up to 10,000 m of sediments, which contain a certain proportion of calcium sulfates. Schenck et al. (2000) distinguish six hydrothermal deep Situated formations. These are due to their high Porosity and permeability and since they still upwards have been completed for a storage of CO₂, The flat situated formations (&lt;2000 m depth) are also in principle for a CO₂Storage, although they in terms of geothermal energy because of their comparatively small temperature difference to Earth's surface is less efficient. In their study, the geothermal potential of Rhät Aquifer in Schleswig-Holstein appreciate Schenck et al. (2000), although the volume of to about 10¹⁰ m³, The by mineral binding in Rhät Aquifer or comparable formations landfilling Total volume of CO₂ but depends on the in them Amount contained from sulfate minerals.

0018Anhydrite is often contained in sandstone formations Cement mineral, such as in the Rhät- or Red sandstone layers. Mostly there are the sulfate minerals in the formation adjacent topcoat. The CO₂ Nevertheless, in these cases, conversion reactions be bound in the outer layer of secondary carbonates even if the formation of CO, the₂ was added free of Sulfate minerals is. is For the purposes of this invention Therefore the top layer to the formation duly considered. For example, in some places in North-East Germany Sedimentary basins are the sulfate minerals in a such topcoat.

00191 shows a schematic representation of an arrangement for performing the method according to the invention. The total designated 1 formation with calcium-containing Minerals, especially anhydrite, is schematically from the Surface shown 2 via an injection well 3 and a production well 4 opened. In its porous Rock matrix performs the formation 1 saline Formation waters, the increasing because of the depth Temperature (geothermal gradient) a significantly higher have temperature than the outdoor temperature at the Surface 2. The heated water formation occurs over the production well 4 as hot water or steam at a Outlet opening 5 at the surface in a line 6 one that with the outlet opening 7 of the injection bore is connected via a connecting line. 6

0020The connection line 6 via a heat exchanger 8 out, the cut off the hot water or steam heat and in another vapor or liquid medium write that the exchanger 8 also flows through. These Heat can either directly for heating purposes or for Energy are used. The heat exchanger 8 in Direction of the inlet opening 7 of the injection well 3 leaving, recooled formation water is an in the figure 1 pump, not shown, back into the formation promoted, the at the same time a close Inlet opening 7 arranged inlet CO₂ in the Formation water is introduced, the over the Injection well with water and optionally alkaline Substances will pressed into the formation. The pump is For example, as a submersible pump or as in line 6 built-in pump running.

0021is By feeding the recooled formation water the warm formation water cooled. Due to having decreasing temperature decreasing solubility of anhydrite accumulates this in the formation water, so then calcium carbonate CaCO₃ fails.

0022In an alternative embodiment of the invention are the Outlet openings 5, 7 of the injection hole 3 and the Production well 4 not interconnected. Such Embodiment of an inventive arrangement for Carrying out the process is for example in Consideration when the formation water of drinking water quality having. In these cases the can via the feed bore 4 to daily discharge water or superheated steam through the Heat exchanger 8 a drinking water treatment plant are supplied. Since the water is not recycled is, it is then necessary, however, the Outlet opening 7 of the injection hole 3 with a connect water source needs while ensuring, that the temperature of the water supplied under the Temperature of formation water is.

0023<b>Literature:</b><sl><li>[1] Korbol, R., and Kaddour, A., 1995. Sleipner vest CO₂disposal - Injection of removed CO₂ into the Utsira Formation, <i>Energy Convers. Manag.,</i> 36, 509-512., 1995</li><li>[2] Gunter, WD, Bachu, S., Law, DHS, Marwaha, V., Drysdale, DL, MacDonald, DE, and McCann, TJ, 1996. Technical and economic feasibility of CO₂ disposal in aquifers within the Alberta Sedimentary Basin, Canada,<i>Energy Convers. Manag., 37,</i> 1135-1142., 1996</li><li>[3] Johnson, JW, JJ Nitao, CI Steffelbauer, and KG Knaus, 2001. Reactive transport modeling of geologic C02 sequestration in saline aquifers: The influence of intraaquifer shales and the relative effectiveness of structural, solubility, and mineral trapping during prograde and retrograde sequestration, paper presented at<i>First National Conference on Carbon Sequestration,</i>Washington, DC, May 14-17., 2001</li><li>[4] White, SP, Weir, GJ, Kissling, WM., 2001 Numerical Simulation of CO2 Sequestration in Natural CO₂Reservoir on the Colorado Plateau, paper presented at<i>First National Conference on Carbon Sequestration,</i>Washington, DC, May 14-17., 2001</li><li>[5] McPherson, BJOL, Lichtner, PC, 2001. C02 Sequestration in Deep Aquifers, paper presented at <i>ridge National Conference on Carbon Sequestration,</i> Washington, DC, May 14-17., 2001</li><li>[6] Xu, T., Apps, YES, and Pruess, K., 2003. Reactive geochemical transport simulation to study mineral trapping for C02 disposal in deep arenaceous formations,<i>J. Geophys. Res., 108 (B2)</i>2071, doi: 10.1029 / 2002JB001979.</li><li>[7] Schenck, PF, Kirsch, R., and Christensen, S., 2000. The Geothermal potential in Schleswig-Holstein,<i>Journal of Applied Geology, 46,</i> 130-137.</li></sl>