Pressure-transient behavior during cold water injection

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During injection testing, pressures in geothermal wells sometimes decline after an initial period of increase despite continued injection. The injection tests carried out at the Yutsubo geothermal field in Kyushu, Japan exhibit this peculiar behavior. During injection testing of Yatsubo well YT-2, observed downhole pressures eventually began to decline despite sustained injection rates. We have carried out numerical simulation studies using a radial flow model to examine this behavior. Double porosity ("MINC") models are adopted, in which the fracture porosity increases due both to cooling and to pressure buildup, and the permeability is very sensitive to porosity changes. This extreme ... continued below

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407-411

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Nakao, Shinsuke & Ishido, Tsuneo January 24, 1996.

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Description

During injection testing, pressures in geothermal wells sometimes decline after an initial period of increase despite continued injection. The injection tests carried out at the Yutsubo geothermal field in Kyushu, Japan exhibit this peculiar behavior. During injection testing of Yatsubo well YT-2, observed downhole pressures eventually began to decline despite sustained injection rates. We have carried out numerical simulation studies using a radial flow model to examine this behavior. Double porosity ("MINC") models are adopted, in which the fracture porosity increases due both to cooling and to pressure buildup, and the permeability is very sensitive to porosity changes. This extreme sensitivity of fracture permeability to porosity appears to be necessary to reproduce the late-time pressure decline, and suggests that fractures were opened by injection-induced cooling near the well.

Physical Description

407-411

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  • Proceedings, Twenty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 22-24, 1996

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  • Report No.: SGP-TR-151-56
  • Grant Number: None
  • Office of Scientific & Technical Information Report Number: 889851
  • Archival Resource Key: ark:/67531/metadc884515

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  • January 24, 1996

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 30, 2016, 6:11 p.m.

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Nakao, Shinsuke & Ishido, Tsuneo. Pressure-transient behavior during cold water injection, article, January 24, 1996; United States. (digital.library.unt.edu/ark:/67531/metadc884515/: accessed August 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.