Sufficiently representative and detailed characterisation of potential storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere sites is essential for accurate simulation of their long-term storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere performance. Geomechanical characterisation of the host and caprocks of the target reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids and the assessment of the long-term behaviour of the overburdenRocks and sediments above any particular stratum in a CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere 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 require the determination of mechanical (elastic) properties of these rocks. The first step for geomechanical assessment involves the development of a static 3D geologic model of the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere site (e.g. using Petrel, EarthVision, etc.), which specifies stratigraphicThe order and relative position of geological strata contacts, structures, faults, wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids locations, and other salient features that have been identified from baseline wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids logs, seismic surveys, surface maps, etc. Within this geologic model, the distinct strata are populated with representative hydrological, geochemical, and geomechanical attribute data, which are typically obtained at sparsely-distributed locations through geophysical surveys, core/fluid sampling programs, and associated analytical studies, then extrapolated between imaging/sampling locations using geostatistical methods. Hydrological data would include temperature, pressure, porosityMeasure for the amount of pore space in a rock, permeabilityAbility to flow or transmit fluids through a porous solid such as rock, and ambient flow gradients. Geochemical data may include detailed mineralogy and fluid-phase compositions/saturations, while geomechanical data may include in situ stress fields and fractureAny break in rock along which no significant movement has occurred densities, apertures, and orientations (Johnson, 20092009 - J. W. JohnsonIntegrated modeling, monitoring, and site characterization to assess the isolation performance of geologic CO2 storage: Requirements, challenges, and methodologysee more). Aarnes et al., 2010 gives a comprehensive list for the geomechanical data requirements, such as rock compressibility, Young's modulus, Poisson's ratio, compressive strength, tensile strength, in situ vertical total stress, in situ major horizontal and minor horizontal total stress, formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it fracturing pressure, fault(geology) A surface at which strata are no longer continuous, but are found displaced valving pressure, fault reactivationThe tendency for a fault to become active, i.e. for movement to occur pressure, etc.
For geological storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere of CO2Carbon dioxide, an important element of the model is whether conductive features exist within the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir. Therefore, particular attention should be given to collecting data for the primary caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir and describing its properties relevant to storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere containmentRestriction of the movement of a fluid to a designated volume (e.g. reservoir). For storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere sites that have a caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir that has contained hydrocarbons over geologic time scales, the task is focused on the characterisation of the geomechanical properties of the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir and any pre-existing fault(geology) A surface at which strata are no longer continuous, but are found displaced planes through the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir. These can be used to estimate threshold reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids pressures for creating new fractures through the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir or activating existing fractures.
Caprocks consist typically of sediments from distal depositional environments, which are characterised by relatively uniform conditions over large areas. CaprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir lithologyThe nature and composition of rocks, fluid-flow and geomechanical properties are therefore likely to vary much less than those of the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids rocks. Consequently, extrapolation of lithologyThe nature and composition of rocks-related caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir properties from a small number of wells over a large potential footprint area can be better constrained than extrapolation of reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids properties. However, relevant caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir properties due to deformation (faults, joints) cannot easily be extrapolated but require detailed local assessment covering the whole footprint area. The regional seismic stratigraphy of the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir should be discernible from 2D seismic data, as would major faults that cut it. Smaller structural features, for example 'polygonal' type minor faults that characterise some shaleClay that has changed into a rock due to geological processes sequences, generally require good quality 3D seismic data for their proper identification. Very small structures, fractures and joints are usually below the limit of seismic detection resolution. Assessment of the presence of microfractures in the subsurface is challenging, because mechanical deformation and depressurisation during coring may induce microfractures in core samples that are difficult to distinguish from those that formed in situ. Consequently, careful coring and preservation of cores is a prerequisite for successful microfracture assessment (Chadwick et al., 2008).
The presence of fractures and their azimuth can be determined from core examination. Vertical in-situ stress can be obtained from density logs. Mechanical properties such as elastic properties for different formations can be obtained using dipole sonic logs as wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids.
Among the tests applied on core samples to measure rock geomechanical properties, uniaxial compression is the most widely performed method, where stress is applied only in one direction. This test is used to determine uniaxial or unconfined strength, Young's modulus and Poisson's ratio. On the other hand, stress is applied in all three directions in a triaxial compression test. From a triaxial compression test, the complete stress-strain curve may be obtained. A complete stress-strain curve records the core response to loading up to rock failure and beyond (post-failure). It provides information on the strength (maximum axial stress reached), yield stress point (marking the departure from linear elastic behaviour), and residual (post-failure) strength of the rock sample under a given confining pressure.
During geomechanical simulations, the initial stress state and stress/displacement boundary conditions for the model domain need to be defined.