Monitoring of Casing Integrity in Geothermal Wells

Abstract

In order to gain an early warning of potential casing problems in geothermal wells, an electromagnetic instrument has been designed to log the casing condition. The Hot Hole Casing Corrosion (HHCC) instrument is capable of operation in real time in the harsh geothermal environment, at temperatures up to 320oC and at pressures up to 200 bar. The HHCC toolís operation enables the accurate monitoring of both internal and external casing condition in the wellís natural state without quenching. A major advantage that this instrument offers is the capability to detect corrosion on the external wall of the casing. A programme of regular checks on casing condition has been instigated in several geothermal fields in New Zealand. This has proven useful in monitoring the casing integrity of geothermal wells and satisfying the operatorís requirements for proving the safety of wells.