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Flow in horizontally anisotropic multilayered aquifer systems with leaky wells and aquitards
Citation:
Cihan, A., Q. Zhou, J. Birkholzer, AND S. Kraemer. Flow in horizontally anisotropic multilayered aquifer systems with leaky wells and aquitards. WATER RESOURCES RESEARCH. American Geophysical Union, Washington, DC, , online, (2013).
Impact/Purpose:
The goal of this development project was to create tools for regulators in the evaluation of permit applications for large volume and long term injection of CO2 into deep saline sedimentary formations for the purpose of geologic storage or sequestration of carbon (GCS). The development of innovative semi-analytical solutions or the subsurface pressure response to large volume injections is foundational to the effort. The research is supported by an interagency agreement between EPA and DOE/Lawrence Berkeley National Lab.
Description:
Flow problems in an anisotropic domain can be transformed into ones in an equivalent isotropic domain by coordinate transformations. Once analytical solutions are obtained for the equivalent isotropic domain, they can be back transformed to the original anisotropic domain. The existing solutions presented by Cihan et al. [2011] for isotropic multilayered aquifer systems with alternating aquitards and multiple injection/pumping wells and leaky wells were modified to account for horizontal anisotropy in aquifers. With coordinate transformation, a circular well with finite radius becomes an ellipse, and thus in the transformed domain the head contours in the immediate vicinity of the well have elliptical shapes. Through a radial flow approximation around the finite radius wells, the elliptical well boundaries in the transformed domain are approximated by an effective well radius expression. The analytical solutions with the effective radius approximations were compared with exact solutions as well as a numerical solution for elliptic flow. The effective well radius approximation is sufficiently accurate to predict the head buildup at the well bore of the injection/pumping wells for moderately anisotropic systems (K_x/K_y <= 25). The effective radius approximation gives satisfactory results for predicting head buildup at observation points and leakage through leaky wells away from the injection wells even for highly anisotropic aquifer systems (K_x/K_y <= 1000).
