| Title | Interpreting Drilling Data to Inform Deep Geothermal Reservoir Rock Mass Properties |
|---|---|
| Authors | Marlène C. Villeneuve, Aliaa Hammoud, Anette Mortensen |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | In deep geothermal drilling, tens to hundreds of meters are drilled without cutting retrieval and, therefore, without insight into the rock mass. Despite their increasing development, studies using drilling parameters and logging-while-drilling to interpret the rock mass in high-temperature, deep geothermal environments remain rare. Here we present a method where the drilling parameters from wells in Iceland are used to assess the quality of the rock mass, with particular focus on its effect on drillability. We use the drilling reports and drilling data to develop this method based on recent work into relating geotechnical drilling and tunnelling boring machine parameters to the rock mass. First, we pre-process the drilling parameters produce the penetration index (PI), which is the ratio of normalized penetration rate to normalized weight on bit, and the net advance rate (NAR) which is the drilling speed averaged over 1 m length, including times when PR is 0, but RPM is > 0. Key variations in processed (PI, NAR) drilling parameters are used to interpret the drillability in different rock masses (e.g. poor drillability, fractured rock). The processed drilling parameters are combined with the interpretations from drill cuttings to determine the impact of lithology changes on drillability, as well as other indicators of down-hole conditions, such as circulation loss and feed zones. We show that different rock masses have distinct signatures of processed drilling parameter combinations, providing the ability to interpret geology using drilling parameters. |