Thermal Drawdown-Induced Flow Channeling in Fractured Geothermal Reservoirs

Pengcheng Fu, Yue Hao, Stuart D.C. Walsh, Charles R. Carrigan

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27 Citations (Scopus)

Abstract

We investigate the flow-channeling phenomenon caused by thermal drawdown in fractured geothermal reservoirs. A discrete fracture network-based, fully coupled thermal–hydrological–mechanical simulator is used to study the interactions between fluid flow, temperature change, and the associated rock deformation. The responses of a number of randomly generated 2D fracture networks that represent a variety of reservoir characteristics are simulated with various injection-production well distances. We find that flow channeling, namely flow concentration in cooled zones, is the inevitable fate of all the scenarios evaluated. We also identify a secondary geomechanical mechanism caused by the anisotropy in thermal stress that counteracts the primary mechanism of flow channeling. This new mechanism tends, to some extent, to result in a more diffuse flow distribution, although it is generally not strong enough to completely reverse flow channeling. We find that fracture intensity substantially affects the overall hydraulic impedance of the reservoir but increasing fracture intensity generally does not improve heat production performance. Increasing the injection-production well separation appears to be an effective means to prolong the production life of a reservoir.

Original languageEnglish
Pages (from-to)1001-1024
Number of pages24
JournalRock Mechanics and Rock Engineering
Volume49
Issue number3
DOIs
Publication statusPublished - 1 Mar 2016
Externally publishedYes

Keywords

  • Enhanced geothermal system
  • Flow channeling
  • Geothermal
  • Hot wet rock
  • Thermal breakthrough
  • THM model

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