Construction of a well impairment model for determination of geothermal clogging

Abstract Producing geothermal heat from production water causes cooldown from the reservoir temperature up to 25 • C at fluid pressures from over 100 bar to 10 bar. During the process degassification of CO2 cause an increase in pH and by that dissolution and precipitation of minerals. At depth, mineral precipitation in the reservoir restricts flow paths through the cyclic system, resulting into injectiv-ity loss, by that higher injection pressures result in additional costs. In other words knowing where under (P,T)-conditions certain minerals are dissolved and generated helps to find spatial solutions that prevent the previously mentioned clogging and by that optimizes the fluid circulation. Due the large number of timesteps, numerically modeling mineralization, accounting for the reaction kinetics, can be computationally expensive. These simulations are less expensive when assuming a local equilibrium between the reactants and reaction-products. As described in [1] we present an analytical model for mineral precipitation in a low-enthalpy geothermal reservoir. The three different reaction regimes are (1) fast reactions (2) very slow reactions (3) reaction/transport intermediate 1 zone. We focus on the near-wellbore region in the reservoir, where precipitation can behave as a ‘skin’ and has a more dramatic impact on the injectivity than precipitation further downstream. Our numerical model uses a coupling approach between PHREEQC and COM-SOL utilizing the qualification of the different reaction regimes. This methodology was validated by using an analytical solution of a specific mineralization case. In addition it was compared to a field case.