Thermal Cycling-Induced Wellbore Integrity Risks in Super-Hot Geothermal Drilling: Identifying Hazardous Operational Scenarios

Document Type

Conference Proceeding

Publication Date

1-1-2025

Abstract

Super-hot geothermal drilling operations are subjected to significant thermal variations due to the extremely high-temperature nature of these advanced geothermal reservoirs. These thermal cycles, resulting from operational activities such as fluid circulation, shut-ins, and production fluctuations, can induce substantial thermo-mechanical stresses on wellbore components, potentially compromising well integrity. In this study, we present a comprehensive simulation-based investigation into the effects of thermal cycling on wellbore integrity during super-hot geothermal drilling. Utilizing a rigorously developed coupled thermo-mechanical modeling framework with multilayered heat resistance analysis, we analyze the stress responses of wellbore materials-particularly casing and cement sheaths-under various thermal loading scenarios. The model incorporates realistic material properties, boundary conditions, and operational parameters to accurately replicate field conditions, including convective heat transfer coefficients calibrated from field data and formation heat-storage effects. Our numerical investigation identifies multiple hazardous operational scenarios that threaten wellbore integrity in super-hot geothermal environments. These include rapid temperature fluctuations during initial circulation after extended shut-ins, thermal shock from wellbore flashing events, superheated formation fluids influxes, or steam kick management operations. Thermal analysis revealed that casing shoes experience the most severe temperature gradients, with peak heating/cooling rates exceeding 3°F/min during the phases. Additionally, our heat transfer maps demonstrated that rapid temperature variations affect not only the casing shoes but also extend to the surfaces for both the surface and inner casings, creating complex stress patterns throughout the wellbore system that can potentially lead to debonding or micro-fracturing. The findings underscore the critical importance of accounting for thermal cycling effects in the design and operation of super-hot geothermal wells. By identifying hazardous operational scenarios through advanced simulation, this work provides valuable insights into developing mitigation strategies to enhance wellbore longevity and safety in super-hot geothermal drilling operations.

Publication Source (Journal or Book title)

Transactions Geothermal Resources Council

First Page

667

Last Page

694

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