Title: |
Modeling of Calcite Scaling and Estimation of Gas Breakout Depth in A Geothermal Well by Using PHREEQC |
Authors: |
Taylan AKIN, Aygün GÜNEY, Hulusi KARGI |
Key Words: |
phreeqc, calcite scaling, gas breakout depth |
Conference: |
Stanford Geothermal Workshop |
Year: |
2015 |
Session: |
Geochemistry |
Language: |
English |
Paper Number: |
Akin |
File Size: |
944 KB |
View File: |
|
Calcite scaling is widely encountered in geothermal wells and it has to be inhibited since it prevents production. As a result of a pressure drop, thermal fluids start to boil and degas of CO2 while fluids rise in a wellbore. Thermal fluid becomes saturated to calcite as a result of both CO2 exsolution and concentration increase of calcium and carbonates as a consequence of boiling. When the first gas bubble is formed, CO2 exsolution affects the ph and also carbonate species. In order to prevent calcite scaling effectively, inhibitor must be injected into the wellbore at a depth below gas breakout point where thermal fluid is still in liquid phase. Thermal fluid transforms from 100% liquid to both liquid and gas phases at the gas breakout depth when the sum of partial pressures of water vapor and non-condensable gases exceed the wellbore pressure under flowing conditions. There are a lot of ways to predict the gas breakout depth in geothermal wellbores. One of them, the easiest but primitive, is dynamic PT survey evaluation. This method is common in industry but limited with applicable flow rate. Therefore determining gas breakout depth from dynamic pressure profile is not sensitive. In this study, major chemical analysis of brines, in situ measurements (pH, CO2/H2O ratios), steam fractions at sampling conditions, dynamic wellbore temperature and pressure data were used to compute gas breakout depth in a well at Kizildere geothermal field. All calculations were performed with thermodynamic approach by using PHREEQC software.
Press the Back button in your browser, or search again.
Copyright 2015, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.
Attend the nwxt Stanford Geothermal Workshop,
click here for details.