Numerical simulation of magmatic hydrothermal systems

Abstract

[1] The dynamic behavior of magmatic hydrothermal systems entails coupled and nonlinear multiphase flow, heat and solute transport, and deformation in highly heterogeneous media. Thus, quantitative analysis of these systems depends mainly on numerical solution of coupled partial differential equations and complementary equations of state (EOS). The past 2 decades have seen steady growth of computational power and the development of numerical models that have eliminated or minimized the need for various simplifying assumptions. Considerable heuristic insight has been gained from process-oriented numerical modeling. Recent modeling efforts employing relatively complete EOS and accurate transport calculations have revealed dynamic behavior that was damped by linearized, less accurate models, including fluid property control of hydrothermal plume temperatures and three-dimensional geometries. Other recent modeling results have further elucidated the controlling role of permeability structure and revealed the potential for significant hydrothermally driven deformation. Key areas for future research include incorporation of accurate EOS for the complete H 2 O-NaCl-CO 2 system, more realistic treatment of material heterogeneity in space and time, realistic description of large-scale relative permeability behavior, and intercode benchmarking comparisons. PURPOSE AND SCOPE[2] This review emphasizes the application of numerical modeling to understand and quantify processes in magmatic hydrothermal systems. We assess the state of knowledge and describe advances that have emerged in the 2 decades since a similar review by Lowell [1991]. Though our ability to rigorously describe key hydrothermal processes is still imperfect, there have been substantial advances since Lowell's [1991] review. These advances owe mainly to the steady growth of computational power and the concomitant development of numerical models that have gradually minimized various simplifying assumptions. They include incorporation of more accurate equations of state (EOS) for the fluid system, an increased ability to represent geometric complexity and heterogeneity, and faster and more accurate computational schemes. These advances have revealed dynamic behaviors that were entirely obscured in previous generations of models.[3] For purposes of this paper we define "magmatic hydrothermal systems" as aqueous fluid systems that are influenced by magma bodies in the upper crust. We particularly emphasize multiphase, multicomponent phenomena, which can have both quantitative and qualitative effects on the behavior of hydrothermal systems [Lu and Kieffer, 2009]. Multiphase (liquid-vapor) hydrothermal phenomena of interest include phase separation at scales ranging from centimeters to kilometers, with concomitant geochemical effects; novel modes of heat transport such as boiling plumes and countercurrent liquid-vapor flow ("heat pipes") [Hayba and Ingebritsen, 1997]; profound retardation of pressure transmission [Grant and Sorey, 1979]; and boiling-related minera...

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