Sensitivity study on hydraulic well testing inversion using simulated annealing

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For environmental remediation, management of nuclear waste disposal, or geothermal reservoir engineering, it is very important to evaluate the permeabilities, spacing, and sizes of the subsurface fractures which control ground water flow. Cluster variable aperture (CVA) simulated annealing has been used as an inversion technique to construct fluid flow models of fractured formations based on transient pressure data from hydraulic tests. A two-dimensional fracture network system is represented as a filled regular lattice of fracture elements. The algorithm iteratively changes an aperture of cluster of fracture elements, which are chosen randomly from a list of discrete apertures, to improve the ... continued below

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55 p.

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Nakao, Shinsuke; Najita, J. & Karasaki, Kenzi November 1, 1997.

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Description

For environmental remediation, management of nuclear waste disposal, or geothermal reservoir engineering, it is very important to evaluate the permeabilities, spacing, and sizes of the subsurface fractures which control ground water flow. Cluster variable aperture (CVA) simulated annealing has been used as an inversion technique to construct fluid flow models of fractured formations based on transient pressure data from hydraulic tests. A two-dimensional fracture network system is represented as a filled regular lattice of fracture elements. The algorithm iteratively changes an aperture of cluster of fracture elements, which are chosen randomly from a list of discrete apertures, to improve the match to observed pressure transients. The size of the clusters is held constant throughout the iterations. Sensitivity studies using simple fracture models with eight wells show that, in general, it is necessary to conduct interference tests using at least three different wells as pumping well in order to reconstruct the fracture network with a transmissivity contrast of one order of magnitude, particularly when the cluster size is not known a priori. Because hydraulic inversion is inherently non-unique, it is important to utilize additional information. The authors investigated the relationship between the scale of heterogeneity and the optimum cluster size (and its shape) to enhance the reliability and convergence of the inversion. It appears that the cluster size corresponding to about 20--40 % of the practical range of the spatial correlation is optimal. Inversion results of the Raymond test site data are also presented and the practical range of spatial correlation is evaluated to be about 5--10 m from the optimal cluster size in the inversion.

Physical Description

55 p.

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INIS; OSTI as DE98052728

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  • Other Information: PBD: Nov 1997

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  • Other: DE98052728
  • Report No.: LBNL--41131
  • Grant Number: AC03-76SF00098
  • DOI: 10.2172/658166 | External Link
  • Office of Scientific & Technical Information Report Number: 658166
  • Archival Resource Key: ark:/67531/metadc707358

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  • November 1, 1997

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • Jan. 19, 2018, 2:04 p.m.

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Nakao, Shinsuke; Najita, J. & Karasaki, Kenzi. Sensitivity study on hydraulic well testing inversion using simulated annealing, report, November 1, 1997; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc707358/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.