Multiphase thermohaline convection in the earth's crust: I. A new finite element - Finite volume solution technique combined with a new equation of state for NaCl-H2O

Sebastian Geiger*, Thomas Driesner, Christoph A. Heinrich, Stephan K. Matthäi

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

81 Citations (Scopus)

Abstract

We present a new finite element - finite volume (FEFV) method combined with a realistic equation of state for NaCl-H2O to model fluid convection driven by temperature and salinity gradients. This method can deal with the nonlinear variations in fluid properties, separation of a saline fluid into a high-density, high-salinity brine phase and low-density, low-salinity vapor phase well above the critical point of pure H2O, and geometrically complex geological structures. Similar to the well-known implicit pressure explicit saturation formulation, this approach decouples the governing equations. We formulate a fluid pressure equation that is solved using an implicit finite element method. We derive the fluid velocities from the updated pressure field and employ them in a higher-order, mass conserving finite volume formulation to solve hyperbolic parts of the conservation laws. The parabolic parts are solved by finite element methods. This FEFV method provides for geometric flexibility and numerical efficiency. The equation of state for NaCl-H2O is valid from 0 to 750°C, 0 to 4000bar, and 0-100 wt.% NaCl. This allows the simulation of thermohaline convection in high-temperature and high-pressure environments, such as continental or oceanic hydrothermal systems where phase separation is common.

Original languageEnglish
Pages (from-to)399-434
Number of pages36
JournalTransport in Porous Media
Volume63
Issue number3
DOIs
Publication statusPublished - Jun 2006
Externally publishedYes

Keywords

  • Brine
  • Convection
  • Finite element
  • Finite volume
  • Hydrothermal
  • Mid-ocean ridge
  • NaCl-HO
  • Numerical modeling
  • Porphyry copper
  • Two-phase flow
  • Vapor

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