The effect of calcite deposition on geothermal well inflow performance

Deposition of calcite in a formation may significantly reduce the inflow pe rformance of geothermal wells producing brine with CO2 content. The key ope rational and reservoir parameters influencing the magnitude of impairment b y calcite deposition were identified through the derivation of analytical e xpressions for the rate of calcite deposition and its effect on flow rate a ssuming idealized flow conditions. A methodology for the use of derived exp ressions permits the investigation of calcite deposition processes for spec ific reservoir descriptions and well operations. The rate of calcite scalin g 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 cal cite deposition around the well may be significantly reduced by decreasing the pressure gradient near the well and,or increasing the effective wellbor e radius through well-stimulation techniques (e.g.. acid treatments). Reduc ing the flow rate will generally increase the production time of a well bef ore significant flow impairment by deposited calcite. (C) 1999 CNR. Publish ed by Elsevier Science Ltd. All rights reserved.