| Title | Reducing Flat Time in Geothermal Drilling: Surface-Landed Threaded Wellhead Installation |
|---|---|
| Authors | Anil Tokcan, Sami Atalay, Ernesto Rivas, William M. Rickard |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | Reducing non-productive time (NPT) is critical in geothermal drilling, where complex formations and high costs demand operational efficiency. We present a field-proven wellhead installation method that eliminates waiting on cement time by landing each casing string at the surface. The method leverages redesigned wellhead equipment (WHE) that allows the wellhead to be landed directly on the previous casing string using threaded connections manufactured to API wellhead specifications. This configuration enables immediate blowout preventer (BOP) installation and pressure testing without waiting for cement curing. In conventional wellhead installation, the BOP stack cannot be reinstalled until the cement achieves sufficient compressive strength to support the casing, often resulting in extended flat time. The new design eliminates the need for welding and associated heat-treatment time by employing threaded interfaces between casing strings and the wellhead housing. This enables BOP-related work to begin immediately after cement placement. Operational experience has verified time savings of eight hours per string, saving one day of rig time during the construction of a geothermal well. The incremental cost of modifying the WHE is minimal, typically involving only machining threaded connections instead of weld preparation. Overall, this method is estimated to reduce well construction costs by tens of thousands of dollars per well. This paper details the engineering design, operational procedure, and risk mitigation strategies used to safely implement this system. Results demonstrate that targeted equipment redesign and procedural innovation can reduce flat time without compromising well integrity or safety—offering a method for improved efficiency in geothermal well delivery. |