3. FLOW MODELLING

InjectionThe process of using pressure to force fluids down wells of CO2Carbon dioxide into deep geological formations involves deploying many of the technologies and methodologies that have been developed in the oil and gas (exploration and production) industry. Computer simulation of storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids dynamics is one of these technologies, along with wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids-drilling technology, injectionThe process of using pressure to force fluids down wells technology, and monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions methods.

The mechanisms that control the behaviour of injected CO2need to be evaluated through fluid flow modelling based on an understanding of the processes that are active in the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids and the available injectionThe process of using pressure to force fluids down wells/production and monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions data.

Site characterisation and storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere system modelling work helps to design a robust monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions, verification(CO2 storage) The proof, to a standard still to be decided, of the CO2 storage using monitoring results; (in the context of CDM) The independent review by a designated operational entity of monitored reductions in anthropogenic emissions and accountingActivities aiming to document and report avoided CO2 emissions for a project system that provides data for validating modelling results, monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions potential leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column, and providing confidence that the CO2Carbon dioxide would remain in the subsurface. A number of existing reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids simulators have been used or further developed to evaluate underground multi-phase flow, seepage through the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir, geomechanical impact, or flow in fractured media.

ReservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids and storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere system simulations are used to determine (modified from NETL, 20092009 - NETLBest practices for monitoring, verification, and accounting of CO2 stored in deep geologic formations.see more):

• the temporal and spatial migrationThe movement of fluids in reservoir rocks of the injected CO2Carbon dioxide plumeDispersing volume of CO2Carbon dioxide-rich phase contained in target formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it;
• the effect of geochemical reactions on CO2Carbon dioxide trapping(CO2Carbon dioxide) ContainmentRestriction of the movement of a fluid to a designated volume (e.g. reservoir) or immobilisation of CO2Carbon dioxide, there are four main trapping mechanisms: structural or stratigraphicThe order and relative position of geological strata trapping; residual CO2Carbon dioxide trapping (capillary trappingImmobilisation of a fraction of in-situ fluids by capillary forces) by capillary forces; solubility trappingA process in which fluids are retained by dissolution in liquids naturally present by dissolution of CO2Carbon dioxide in resident formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it fluids forming a non-buoyant fluid; and mineral trapping where CO2Carbon dioxide is absorbed by solid minerals present in 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%) volume and long-term 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 behaviour;
• the caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir and wellboreThe physical hole that makes up the 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, it can be cased, open, or a combination of both; open means open for fluid migrationThe movement of fluids in reservoir rocks laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migrationThe movement of fluids in reservoir rocks integrity;
• the impact of thermal/compositional gradients 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;
• the pathways that may allow CO2Carbon dioxide to migrate out of the main 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%) 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;
• the importance of secondary barriers;
• the effects of unplanned hydraulic fracturing;
• the extent of upward migrationThe movement of fluids in reservoir rocks of CO2Carbon dioxide along the outside of the 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 casingA pipe which is inserted to stabilise the borehole of a well after it is drilled;
• the impacts of cement dissolution; and consequences of wellboreThe physical hole that makes up the 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, it can be cased, open, or a combination of both; open means open for fluid migrationThe movement of fluids in reservoir rocks laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migrationThe movement of fluids in reservoir rocks failure.

The aim of flow modelling is different in each phase of the CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere project. During the pre-operational phase, simulation models are used to predict CO2 plumeDispersing volume of CO2-rich phase contained in target formation migrationThe movement of fluids in reservoir rocks and the effectiveness of solubility, residual gas (capillary) and mineral trapping(CO2) Containment or immobilisation of CO2, there are four main trapping mechanisms: structural or stratigraphic trapping; residual CO2 trapping (capillary trapping) by capillary forces; solubility trapping by dissolution of CO2 in resident formation fluids forming a non-buoyant fluid; and mineral trapping where CO2 is absorbed by solid minerals present in the storage volume. During operations, comparison between simulated and monitored plume migrationThe movement of fluids in reservoir rocks are used to refine and calibrate the model, and then update forecasts of plume migrationThe movement of fluids in reservoir rocks. This iterative approach is required to develop confidence in the prediction of plume behaviour. During the post-operational phase, a similar iterative approach is used to predict post-injectionThe process of using pressure to force fluids down wells plume behaviour with a primary focus on quantifying the secondary trapping(CO2) Containment or immobilisation of CO2, there are four main trapping mechanisms: structural or stratigraphic trapping; residual CO2 trapping (capillary trapping) by capillary forces; solubility trapping by dissolution of CO2 in resident formation fluids forming a non-buoyant fluid; and mineral trapping where CO2 is absorbed by solid minerals present in the storage volume mechanisms that will eventually immobilise the CO2Carbon dioxide.

One of the main purposes of developing predictive models is to confirm that the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere project is performing as planned/expected. Data collected during the early monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions phase can be used to address potentials risks and mitigate circumstances when the project may not be performing adequately. Inconsistencies between field data and model predictions, which may suggest a leak, would trigger another level of monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions to determine the CO2Carbon dioxide leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column pathway and the potential plume location and extent. The predictive model that is calibrated and refined using these data forms the basis for predicting longer-term performance. Model calibration and performance confirmation can be done by comparing model predictions with monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions data. Therefore, parameters that will be monitored should include the data needed for this comparison such as downhole pressure, actual injectionThe process of using pressure to force fluids down wells and production rates, 3-D seismic data, tracerA chemical compound or isotope added in small quantities to trace flow patterns data, data from geophysical logs, geochemical data from cores, and reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids fluid test data, etc. ReservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids pressure data may be obtained either by downhole pressure sensors or estimated using surface pressure and injectionThe process of using pressure to force fluids down wells data (NETL, 20092009 - NETLBest practices for monitoring, verification, and accounting of CO2 stored in deep geologic formations.see more).

Besides CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere in the deep saline aquifers or depleted(hydrocarbon reservoir) one where production is significantly reduced gas or oil reservoirs, the enhanced coalbed methane (ECBMEnhanced coalbed methane recovery: the use of CO2 to enhance the recovery of the methane present in unminable coal beds through the preferential adsorption of CO2 on coal) recovery with CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere is also modelled. In addition to monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions, verification(CO2 storage) The proof, to a standard still to be decided, of the CO2 storage using monitoring results; (in the context of CDM) The independent review by a designated operational entity of monitored reductions in anthropogenic emissions, and riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event of CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere in coal seams, optimisation of methane recovery using CO2Carbon dioxide is addressed by numerical modelling. ECBMEnhanced coalbed methane recovery: the use of CO2 to enhance the recovery of the methane present in unminable coal beds through the preferential adsorption of CO2 on coal simulators are used to define the physical and operational boundaries and trade-offs for safe and effective CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere and ECBMEnhanced coalbed methane recovery: the use of CO2 to enhance the recovery of the methane present in unminable coal beds through the preferential adsorption of CO2 on coal recovery. Simulations are used to determine the monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions networks that are needed to predict both the migrationThe movement of fluids in reservoir rocks of CO2Carbon dioxide and within the coal seam and the recovery of CH₄ from the coal seam.

A reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids modelling study starts with the development of a geological model for the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere site that consists of the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids, the primary seals, and may include the overlying formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it, shallow aquiferAn underground layer of fluid-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) with significant permeability to allow flow(s) and the vadose zoneNear surface layer of aeration above the water table (where ambient air infiltrates soil). ReservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids simulation models require site-specific geological parameters both physical (lithologyThe nature and composition of rocks, pressures, temperatures) and chemical (groundwater and formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it fluid compositions, soil gas composition) to properly simulate plume fate and transport over time.

Modelling of the shallow groundwater will provide insights into groundwater flow directions and the potential for transport of groundwater that may be impacted by the CO2Carbon dioxide injectionThe process of using pressure to force fluids down wells process and require migrationThe movement of fluids in reservoir rocks off site.