Making Geothermal Drilling Feasible: Leveraging MPD Success from HPHT Operations in Hungary, Europe

Summary Drilled in the Pannonian Basin, Hungary this HPHT (high-pressure high-temperature) well posed significant technical challenges. Utilizing a non-aqueous drilling fluid (NADF) with a mud weight of 2.04 to 2.24 SG, the vertical well reached a TD of 4,155 m. Key challenges included severe loss of circulation, high formation temperatures leading to high surface flowline temperatures (114°C / 237°F), and gas influxes from high-pressure sands and swab effects during tripping. To address high surface temperatures and protect the RCD (rotating control device) components, high-temperature sealing elements were used in combination with a Mud Cross that was installed below the RCD to circulate cooler mud continuously. This solution extended the RCD component life while eliminating the need for a separate RCD cooling unit, reducing the operational footprint. Losses of circulation were mitigated through a combination of optimized mud properties, LCM (lost circulation materials) pills, and MPD (Managed Pressure Drilling) techniques, ensuring a successful formation integrity test. Gas influxes and early kick detection were controlled with MPD procedures, allowing safe drilling through high-pressure sands and efficient stripping to the surface. The integration of MPD, drilling fluid technology, and Mud Cross implementation enabled successful drilling with minimal NPT and no HSE incidents. MPD stripping techniques significantly improved tripping time and efficiency while maintaining constant bottom- hole pressure. These advancements optimized well economics and demonstrated MPD's potential for unlocking European geothermal drilling opportunities.