| Title | Optimization of Vacuum Insulated Tubulars for Geothermal U-Shaped Wellbores: Modeling Challenges and Performance Enhancement Under Supercritical CO2 Conditions |
|---|---|
| Authors | Nasikul Islam, Corey Dufrene, Elizabeth Cambre |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | Vacuum insulated tubulars (VITs) offer a groundbreaking solution for enhancing thermal efficiency in geothermal wells, particularly when used as casing in producer wells. VITs significantly reduce thermal losses as fluid travels from the reservoir to the surface. This study focuses on optimizing the design of a larger VIT uncemented in the production section of a U-shaped geothermal well. This innovative design addresses limitations of smaller diameter closed-loop systems—such as restricted surface area, flow rate, and flow path—by integrating proven oil and gas wellbore intercept technology with increased energy harvesting capacity. While tubingless strings are not new, applying them with VIT casing is novel. Key parameters—inner and outer diameter, length, material strength, tapered design, connection integrity, and preloaded sections—were optimized by evaluating flow rates, temperature profiles, friction pressure, and the Thermal Siphon effect under supercritical CO₂ conditions. Supercritical CO₂ offers advantages including deeper geothermal access, lower friction, longer turbine life, and higher energy transfer efficiency. A major challenge is the lack of existing software and high-flow test loops to model this complex system. This research explores new methodologies for simulating heat transfer, fluid dynamics, and temperature-pressure behavior within the wellbore. By integrating advanced computational techniques and validating models with empirical data, the study aims to enhance operational efficiency, reduce thermal losses, and optimize performance in high-temperature geothermal environments. Ultimately, it establishes a framework for determining the optimal VIT design for U-shaped geothermal systems. |