The effect of calcite deposition on geothermal well inflow performance

Deposition of calcite in a formation may significantly reduce the inflow performance of geothermal wells producing brine with CO2 content. The key operational and reservoir parameters influencing the magnitude of impairment by calcite deposition were identified through the derivation of analytical expressions for the rate of calcite deposition and its effect on flow rate assuming idealized flow conditions. A methodology for the use of derived expressions permits the investigation of calcite deposition processes for specific reservoir descriptions and well operations. The rate of calcite scaling in the formation was shown to be inversely proportional to the square of the radial distance from the well. For a given flow rate, the degree of calcite deposition around the well may be significantly reduced by decreasing the pressure gradient near the well and,or increasing the effective wellbore radius through well-stimulation techniques (e.g.. acid treatments). Reducing the flow rate will generally increase the production time of a well before significant flow impairment by deposited calcite. (C) 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.