The Simulation and Risk Assessment Focus Area is an integrated effort to develop advanced simulation models of the subsurface and integrate the results into a risk assessment that includes both technical and programmatic risks. As the simulation models are refined with new data, the uncertainty surrounding the identified risks decreases, which in turn provides a more accurate risk assessment and mitigation plan for each project site. Both qualitative and quantitative protocols will be developed to ensure the safe and permanent storage of carbon dioxide (CO2). Results from the simulation models will be incorporated into risk assessments on a project-by-project basis and on a larger basin-scale. As carbon capture and storage (CCS) becomes deployed in major basins, macro model results will be needed to manage reservoirs for pressure management, plume migration, and potential risks of multiple CO2 injection projects across the basin.
Specifically, simulation models also can be used to: (1) predict the thermal impacts and hydrologic flow of CO2 in the target formation; geochemical and thermal changes that may occur in the storage formation; (2) geomechanical effects on the target formation, seals, and release pathways, such as faults, fractures, and wellbores; and (3) the effect of biological responses in the presence of supercritical CO2.
A risk assessment is often performed at the early stages of a project to help in site selection, communicating project goals and procedures to the public, and aiding regulators in permitting for the project. Risk assessment is also necessary in identifying potential issues with a storage site and developing mitigation procedures so that immediate action can be implemented should an issue arise. Risk assessment and management for CO2 storage efforts generally include two primary aspects: (1) programmatic risks (including resource and management risks) that may inhibit project progress or costs, and (2) storage (technical) risks inherent to the scientific and engineering objectives of a storage project. Calculation of risk profiles is a common approach to assessing the predicted performance of large-scale projects. These also help determine long-term project costs and potential liabilities in support of decisions on decommissioning and long-term stewardship.
Schematic Risk Profile for A CO2 Storage Project (Benson, 2007; WRI Presentation)
Simulation and Risk Assessment Technologies
Simulation is a critical step in the systematic development of a monitoring program for a geologic CO2 storage project because the selection of an appropriate measurement method and/or instrument is based on whether the method or instrument can provide the data necessary to address a particular technical issue related to CO2storage. Effective monitoring can confirm that the project is performing as expected from predictive models. The linkage between model results and monitoring data can be complicated if monitoring programs are not designed to address which parameters should be monitored to match with model parameters. These parameters include timing, location, spatial scale, and resolution of measurements. Monitoring data collected early in a project are often used to refine and calibrate the predictive model, improving the basis for predicting the longer term performance of the project. Simulations are utilized to predict the following:
- Temporal and spatial migration of the injected CO2 plume.
- Effect(s) of geochemical reactions on CO2 trapping and long-term porosity and permeability.
- Assess caprock and wellbore integrity.
- Impact of thermal andcompositional gradients in the reservoir.
- Pathways of CO2 out of the reservoir.
- Importance of secondary barriers.
- Effect(s) of unplanned hydraulic fracturing.
- Extent of upward migration of CO2 along the outside of the well casing
- Impacts of cement dissolution.
- Consequences of wellbore failure.
A significant amount of work has been completed by industry and academia to develop simulators for CO2 that couple thermal, hydrologic, mechanical, chemical, and biological (THMCB) impacts of CO2 injection. Several different models (independent and coupled) are currently being used in many field projects to validate laboratory observations. Current research in this focus area includes refinement and coupling of models that can represent these processes for this focus area: