HR: 11:20h
AN: H12D-05    [Abstracts]
TI: A Hybrid Numerical-Analytical Model for Wellbore Leakage in Reservoir-Scale Simulations
AU: * Gasda, S E
EM: sgasda@unc.edu
AF: Princeton University, Civil and Environmental Engineering, Princeton, NJ 08544, United States
AU: * Gasda, S E
EM: sgasda@unc.edu
AF: University of North Carolina at Chapel Hill, Environmental Sciences and Engineering, CB #7431, Chapel Hill, NC 27560, United States
AU: Nordbotten, J M
EM: janmn@mi.uib.no
AF: Princeton University, Civil and Environmental Engineering, Princeton, NJ 08544, United States
AU: Nordbotten, J M
EM: janmn@mi.uib.no
AF: Univeristy of Bergen, Department of Mathematics, Johannes Brunsgate 12, Bergen, 5008, Norway
AU: Celia, M A
EM: celia@princeton.edu
AF: Princeton University, Civil and Environmental Engineering, Princeton, NJ 08544, United States
AB: Large-scale implementation of geological CO₂ sequestration requires quantification of risk and leakage potential. One potentially important leakage pathway for the injected CO₂ involves existing oil and gas wells. Wells are particularly important in North America, where more than a century of drilling has resulted in millions of oil and gas wells. There is significant uncertainty surrounding the integrity of existing wells, and very little data to support quantification of material or hydraulic properties associated with these wells. Models of CO₂ injection and leakage will involve large uncertainties in parameters associated with wells, and therefore a probabilistic framework is required. These models must also be able to capture both the large-scale CO₂ plume associated with the injection and the small-scale leakage problem associated with localized flow along wells. This is made even more difficult by the fact that within a typical simulation domain, many hundreds of wells may exist. Traditional numerical methods are not suitable because grid refinement is needed to capture wellbore flow, which soon becomes computationally prohibitive because of the large number of wells and the need for multiple realizations in a probabilistic framework. Recent developments in analytical models are promising, however, these methods are limited to idealized geological systems. In this paper, we present a new model that combines both numerical and analytical models into a single hybrid model. The governing equations are vertically-averaged and solved numerically on a relatively coarse grid, thereby capturing the large- scale injection problem. Within this coarse-grid simulation, an analytical model is embedded to solve for wellbore flow occurring at the sub-gridblock scale. This hybrid numerical-analytical method is a powerful tool because it combines the advantages of both numerical and analytical methods. We obtain greater flexibility with the numerical model, which can be used solve heterogeneous and geologically complex systems, while the analytical method provides quick and accurate solutions to the wellbore flow problem, thereby eliminating expensive grid refinement. We show that this method compares well with traditional numerical simulations. It also compares well to the fully analytical model, which applies for appropriately simple systems. We also model a more complex system to demonstrate the flexibility of this model for handling CO₂ injection into a dome-shaped aquifer with leakage through an existing well. We believe that the hybrid model provides a simple but powerful tool to evaluate leakage risk in geological CO₂ sequestration.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0900 EXPLORATION GEOPHYSICS
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1800 HYDROLOGY
DE: 8430 Volcanic gases
SC: Hydrology [H]
MN: 2007 Fall Meeting