Statistical abstraction of high-fidelity CO2 pressure histories in 2-D, uniform, cylindrical domains
- Los Alamos National Laboratory
Long-term, deep, geologic sequestration of carbon dioxide (CO{sub 2}) is being evaluated as a world-wide strategy for limiting anthropogenic carbon emissions to the atmosphere. A key element of this evaluation is quantification of the ancillary risks associated with this fundamentally new linkage between the global energy economy and the subsurface ecosphere. Quantitative risk assessment methods traditionally enumerate operational scenarios and describe the multiple physical responses that may ensue from each scenario depending on the quality of information that is available to describe identified system dependencies. For example, multiplepoint injection of compressed CO{sub 2} into a geologic reservoir having a nominal stratigraphy will create a pressurized zone of liquid that migrates through the rock. Scenarios that postulate CO{sub 2} encountering previously undetected wells or natural fractures in the caprock that represent leakage paths to the surface must be treated in a probabilistic format that accommodates unknown details in the subsurface geology. Fluid pressure in the reservoir at the location of the potential transport path drives any potential leakage that might occur, so the spatial and temporal distribution of CO{sub 2} overpressure represents an important metric for numeric simulation. State-of-the-art geologic transport models like FEHM, TUFF, and ECLIPSE (Refs. 1, 2, 3) can accurately simulate multi phase gas migration in a fully characterized geologic domain. However, each simulation can require time periods ranging between minutes and hours to achieve acceptable numerical performance, so it is often impractical to link predictive physics models directly in a quantitative risk assessment that will require transport estimates for thousands of scenarios. When direct computation is not possible, a library of high-fidelity calculations can sometimes be distilled to a simplified statistical correlation that spans the variability in all relevant input parameters while retaining acceptable accuracy in the key predicted qu antities. Essentially, numerical calculations can be used as data for an exploratory trend analysis just as one might regress predictive equations against laboratory measurements to determine unknown parameter values. Statistical correlations are derived here to reproduce radial overpressure as a function of time and position for CO{sub 2} injected along the centerline of cylindrical geologic domains. FEHM was used to compute two-phase pressure histories in a suite of simulations that varied (1) initial pressure, (2) vertical reservoir thickness, (3) domain radius, (4) uniform permeability, and (5) mass injection rate. The simulations include both a 50-yr injection phase and a 50-yr relaxation phase. The correlations are based on a two-step fitting paradigm that first captures the shape of an entire radial pressure profile for a given time and input condition, and then correlates the shape parameters as generalized power products of 6 dimensionless parameters. Estimated overpressures are accurate within a factor of 1.25 compared to the suite of simulated values. The correlations can be used to evaluate rapidly local temporal overpressure for any continuous values within the defined space of input parameters. Inversion of the pressure correlation is also demonstrated to determine the maximum injection rate corresponding to an assumed limiting fracture pressure.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1007984
- Report Number(s):
- LA-UR-10-02526; LA-UR-10-2526; TRN: US201106%%294
- Resource Relation:
- Conference: 9th Annual Carbon Capture and Sequestration Conference ; May 10, 2010 ; Pittsburgh, PA
- Country of Publication:
- United States
- Language:
- English
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