Load History and Buckling of the Production Casing in a High Temperature Geothermal Well

Abstract

The production casing of a high temperature geothermal well is subjected to multiple thermo-mechanical loads in the period from installation to production. Temperature and pressure fluctuations are large in high temperature geothermal wells, for example during the first discharge the temperature difference from a non-flowing to a flowing well can be on the range of hundreds of degrees centigrade. During installation, stimulation and production, problems can arise due to these loads and due to a possible corrosive geothermal environment. Plastic buckling of the production casing is a problem that can occur. It results in a bulge in the wall of the casing and is detrimental to the geothermal energy production and the lifetime of the well. The cost of each well is very high. Therefore, it is important to analyze the structural environment of high temperature geothermal wells in effort to avoid repeated problems in the design and installment phases of the casing.
A finite-element model has been developed to evaluate the temperature distribution, deformation and stresses in a high temperature geothermal well and to evaluate the reasons for buckling in the production casing. The load history of the casing is followed from the beginning of the installment phase to the production phase.
The results show that the load history and also the sequence of loading is important in order to understand the true structural behavior of wells.