Salt precipitation in porous media and multi-valued solutions G. G. Tsypkin Institute for Problems in Mechanics RAS, Moscow, Russia Petroleum engineering – gas hydrate, paraffin etc. formation Soil sciences – salt precipitation, ice formation etc. Chemical engineering – filters Geothermal reservoir engineering – salt precipitation, crystallization of components due to chemical reactions etc.

Salt precipitation in soils with destruction of porous media

SPE The Precipitation of Salt in Gas Producing Wells W. Kleinitz, SPE, M. Koehler and G. Dietzsch, SPE, Preussag Energie GmbH, Germany Scanning electron micrograph of precipitate formation in the sample of rock

Sketch of the problem: salt precipitation in geothermal reservoirs

Basic equations Vapor domain: Water domain:  – porosity,  – density, k – permeability, µ – viscosity,  w – compressibility, h – specific enthalpy, e – the specific internal energy, – thermal conductivity, T – temperature, P – pressure, v – filter velocity, S pr – solid salt saturation, c – salt concentration

Boundary conditions through the interface Discontinuities of water and salt saturation functions Mass balance for H 2 O and salt: Momentum balance: Thermodynamic equilibrium: Energy balance: Similarity solution Initial and boundary conditions

Variation of the mass of salt in the vapour domain as a function of reservoir pressure Tsypkin G., Woods A. J. Fluid Mech. 2005

Analytic (1) and numerical results (2) Tsypkin G., Calore C. Proc. 32nd Workshop on Geothermal Reservoir Engineering, Stanford, 2007

Salt diffusion influence in low-permeability reservoirs Tsypkin G. Fluid Dynamics T = const

Conclusions  There are two self-similar solution branches for precipitation problem  These two branches coincide for critical values of the parameters, and above these values, the self-similar solution ceases to exist  For a higher initial pressure and larger well pressure rock becomes fully sealed with salt  Salt diffusion may lead to a sleeping regime formation in low-permeability rock