The effect of calcite deposition on geothermal well inflow performance

Deposition of calcite in a formation may signi®cantly reduce the in¯ow performance of geothermal wells producing brine with CO2 content. The key operational and reservoir parameters in¯uencing the magnitude of impairment by calcite deposition were identi®ed through the derivation of analytical expressions for the rate of calcite deposition and its e€ect on ¯ow rate assuming idealized ¯ow conditions. A methodology for the use of derived expressions permits the investigation of calcite deposition processes for speci®c 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 ¯ow rate, the degree of calcite deposition around the well may be signi®cantly reduced by decreasing the pressure gradient near the well and/or increasing the e€ective wellbore radius through well-stimulation techniques (e.g., acid treatments). Reducing the ¯ow rate will generally increase the production time of a well before signi®cant ¯ow impairment by deposited calcite. # 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.