## Abstract

We present a new finite element - finite volume (FEFV) method combined with a realistic equation of state for NaCl-H_{2}O 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 H_{2}O, 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-H_{2}O 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 language | English |
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Pages (from-to) | 399-434 |

Number of pages | 36 |

Journal | Transport in Porous Media |

Volume | 63 |

Issue number | 3 |

DOIs | |

Publication status | Published - Jun 2006 |

Externally published | Yes |

## 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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