| Title | Numerical Investigation of the Impacts of Geothermal Reactive Flow Coupled for Wellbore and Reservoir |
|---|---|
| Authors | Hakan Alkan |
| Year | 2007 |
| Conference | European Geothermal Conference |
| Keywords | Reactive flow, geothermal reservoir assessment, productivity index, calcite precipitation, numerical modelling |
| Abstract | Geochemistry is one of the major concerns of the geothermal exploration and reservoir studies. Numerical modelling of the chemical variations during geothermal production and its coupling with hydro-dynamical computations is a key tool for an effective management of the reservoir. High flow rates cause high pressure and in some cases high temperature gradients in the wellbore which in turn result in significant changes in equilibrium chemistry. Saturated minerals precipitate especially in the cases where phase changes occur in the wellbore. If the unfavourable thermodynamic conditions begin to dominate throughout the reservoir, precipitation may take place even in the reservoir. As a conservative point of view, this reduces the permeability and therefore the production performance of the reservoir. The impacts of the chemical variations on the geothermal reservoir performance are studied by coupling a wellbore simulator capable of modelling the carbonate equilibrium with reactive reservoir simulator TOUGHREACT. A basic geothermal reservoir model is created using TOUGHREACT. Reservoir characteristics are chosen to be representative for a geothermal reservoir containing dissolved CO2. The influence of the pore volume changes on hydrodynamic calculations is taken into consideration via modified cubic law. The effect of the calcite precipitation in the wellbore to the deliverability is investigated using the wellbore simulator as function of the wellhead pressure, temperature and flow rate as well as the initial dissolved CO2 amount in the fluid. The precipitation behaviour is coupled with the production performance of the reservoir by using TOUGHREACT model. The effect of the decreasing reservoir pressure on the precipitation profile in the wellbore is investigated. The precipitation of carbonates is calculated to be effective in near well zones by reducing the reservoir permeability. |