6.4.7 CO2 storage project in Schwarze Pumpe – Schweinrich, Germany

For the assessment of the Schweinrich storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere structure(geology) Geological feature produced by the deformation of the Earth’s crust, such as a fold or a fault; a feature within a rock such as a fracture; or, more generally, the spatial arrangement of rocks in Germany, a modified performance assessment (PA) methodology was used comprising the following steps: (i) definition of the assessment basis, (ii) FEP analysis, (iii) safety scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it, (iv) development of dedicated models for probabilistic simulation of safety scenarios, and (v) safety evaluation against HSEHealth, safety and environment effects. The FEP database holds FEPs that may have a potential effect on the safety of the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere system. The latest version of the database contains a total number of 657 FEPs, extracted from various sources. All FEPs have a complete set of identification and classification attributes. These attributes have been assigned generically, and could be used to filter case-specific FEPs with respect to the assessment basis. Case specific FEPs for the Schweinrich case were identified according to the following criteria:

1. FEPs should have a timescale of occurrence less than 1000 years,

2. FEPs should lie within the spatial domains of reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids, sealAn impermeable rock that forms a barrier above and around a reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids such that fluids are held in the reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids, overburdenRocks and sediments above any particular stratum and fault(geology) A surface at which strata are no longer continuous, but are found displaced,

3. FEPs in the spatial domains shallow subsurface, ocean, atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) and underburdon are omitted,

4. FEPs with respect to wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids integrity and engineering are not evaluated since the design and completion(well) Refers to the cementing and perforating of casingA pipe which is inserted to stabilise the borehole of a well after it is drilled and stimulation to connect a well bore to reservoir of future injectionThe process of using pressure to force fluids down wells wells is unknown. EPs for the Schweinrich case will be divided into geochemical EPs acting on long timescales (about 1,000 years), and into geomechanical EPs valid for both short and long timescales of occurrence and duration.

Two EP groups were identified: a leaking fault(geology) A surface at which strata are no longer continuous, but are found displaced EP group and a leaking sealAn impermeable rock that forms a barrier above and around a reservoir such that fluids are held in the reservoir EP group. The geomechanical EPs all relate to the leaking fault(geology) A surface at which strata are no longer continuous, but are found displaced EP group. The geochemical EPs relate to both the leaking fault(geology) A surface at which strata are no longer continuous, but are found displaced and the leaking sealAn impermeable rock that forms a barrier above and around a reservoir such that fluids are held in the reservoir EP group (Chadwick et al., 2008). Some limitations are applicable to the Schweinrich case study, as follows:

• Time frame: The time frame for the FEP analysis was set to 1,000 years. Hazards that may occur as consequence of the identified safety factors were evaluated for 10,000 years, i.e., the simulation period was 10,000 years.

• Spatial domain of the investigated storage(CO2Carbon dioxide) A process for retaining captured CO2Carbon dioxide, so that it does not reach the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) system: The reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids, sealAn impermeable rock that forms a barrier above and around a reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids such that fluids are held in the reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids, overburdenRocks and sediments above any particular stratum, faults and wells compartments were evaluated. The shallow subsurface, ocean (not relevant for structure(geology) Geological feature produced by the deformation of the Earth’s crust, such as a fold or a fault(geology) A surface at which strata are no longer continuous, but are found displaced; a feature within a rock such as a fractureAny break in rock along which no significant movement has occurred; or, more generally, the spatial arrangement of rocks Schweinrich), atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) and underburden compartments were excluded. This selection process is related to the available input data and limitations in the model.

• Probability of occurrence of evaluated scenarios: No attempt to quantify the probability of occurrence of the evaluated scenarios has been made. Instead, it was assumed that the scenarios will definitely occur, i.e., the probability of occurrence of the CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column scenarios is set to 1. These evaluated scenarios represent worst cases.

• Input data: The study used input data that were gained from former geological surveys of the area.

• Model limitations

Based on the FEP analysis and the scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it, the following "what if?" scenarios were identified for simulation:

• Reference scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts assuming no failure of the containmentRestriction of the movement of a fluid to a designated volume (e.g. reservoir) zone occurs,

• Leaking sealAn impermeable rock that forms a barrier above and around a reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids such that fluids are held in the reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts assuming sealAn impermeable rock that forms a barrier above and around a reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids such that fluids are held in the reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids failure by geochemical processes and CO2Carbon dioxide migrationThe movement of fluids in reservoir rocks into the overburdenRocks and sediments above any particular stratum,

• Leaking wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts.

Model software was used for the simulation of four scenarios. In the Schweinrich case, the scenarios present hypothetical future flow and fate of CO2Carbon dioxide in the next 10,000 years. The potential impact of each scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts was expressed as the maximum concentration and flux of CO2Carbon dioxide in the pore system in the shallowest overburdenRocks and sediments above any particular stratum unit, Pleistocene sediments (which form the topmost subsurface layer in the simulation models). No outcome was simulated regarding groundwater deterioration and mobilisation of heavy metals, since no modelling of the flow and fate of CO2Carbon dioxide in the unsaturated zone was conducted. In case of uncertainty on input parameters that were not varied stochastically, the worst-case scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts values were generally selected. Outcome distributions are consequently biased towards the worst-case scenarios. A 2D radial flow model was used to represent the reference scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts, the sealAn impermeable rock that forms a barrier above and around a reservoir such that fluids are held in the reservoir leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts (Fig. 6-10a) and the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts (Fig. 6-10b), while a 3D orthogonal model was used to represent the fault(geology) A surface at which strata are no longer continuous, but are found displaced leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts (Fig. 6-10c). Simulation was carried out with a 3D multiphase flow simulator called SIMED II. The amount of injected CO2Carbon dioxide, its lateral spread in time and the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids pressure were calibrated to the fine-scaled 3D SIMED II model over the injectionThe process of using pressure to force fluids down wells period of 40 years.

This deterministic model represented the injectionThe process of using pressure to force fluids down wells of CO2Carbon dioxide on the flanks of the Schweinrich structure(geology) Geological feature produced by the deformation of the Earth’s crust, such as a fold or a fault; a feature within a rock such as a fracture; or, more generally, the spatial arrangement of rocks by 10 injectionThe process of using pressure to force fluids down wells wells. In this model, the accumulation of CO2Carbon dioxide was mainly in the topmost reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids layer. The representation of the stochastic models was strongly simplified. Each 'what if?' scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts was evaluated with 1,000 model runs with varying stochastic parameters. Based on the results from these model runs concerning the safety of the reference scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts, no CO2Carbon dioxide reaches the uppermost overburdenRocks and sediments above any particular stratum sediments after 10,000 years. Regarding the leaking sealAn impermeable rock that forms a barrier above and around a reservoir such that fluids are held in the reservoir scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts, although CO2Carbon dioxide passes through the sealAn impermeable rock that forms a barrier above and around a reservoir such that fluids are held in the reservoir in this scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts, the velocity of upward migrationThe movement of fluids in reservoir rocks of CO2Carbon dioxide is fairly small and therefore, no CO2Carbon dioxide reaches the uppermost overburdenRocks and sediments above any particular stratum. The leaking wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts is easily the most significant in terms of modelled CO2Carbon dioxide fluxes and CO2Carbon dioxide concentrations in the shallow overburdenRocks and sediments above any particular stratum. The probability that such a scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts will be valid depends on the existence of an old wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids, designed for a purpose other than CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere, penetrating through the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir. The critical safety factor in the leaking wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts is the magnitude of the increase of the (vertical) permeabilityAbility to flow or transmit fluids through a porous solid such as rock in the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids zone, which would be improved by using a proper cement type. However, the best way to avoid the leaking wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts is to design the injectionThe process of using pressure to force fluids down wells wells in such a way that the scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts cannot occur, for example by designing the wells so that the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir is not penetrated and that the wells enter the anticlinal structure(geology) Geological feature produced by the deformation of the Earth’s crust, such as a fold or a fault; a feature within a rock such as a fracture; or, more generally, the spatial arrangement of rocks from below the spill pointThe structurally lowest point in a structural trap that can retain fluids lighter than background fluids. This can be done by the use of directionally drilled deviated Wells that inject the CO2Carbon dioxide at the flanks of the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids. The leaking fault(geology) A surface at which strata are no longer continuous, but are found displaced scenarioA plausible description of the future based on an internally consistent set of assumptions about key relationships and driving forces; note that scenarios are neither predictions nor forecasts indicates moderate CO2Carbon dioxide fluxes and CO2Carbon dioxide concentrations in the shallow overburdenRocks and sediments above any particular stratum. Modelled maximum surface fluxes are comparable to observed leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column rates from natural CO2Carbon dioxide accumulations in Europe and Australia. The maximum concentrations may lead to adverse effects in groundwater and freshwater ecosystems. The critical safety factor is the vertical permeabilityAbility to flow or transmit fluids through a porous solid such as rock of the fault(geology) A surface at which strata are no longer continuous, but are found displaced zone. It is important to stress that the probability of the above-mentioned four scenarios actually occurring has not been assessed. They represent hypothetical 'worst-case' situations that may wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids have a very low probability (Chadwick et al., 2008). It is obvious that the storage(CO2Carbon dioxide) A process for retaining captured CO2Carbon dioxide, so that it does not reach the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) project in Schwarze Pumpe - Schweinrich tries to go quantitative.