(S)PWD – (Seismic) Prediction While Drilling: Development of a New High-Resolution Seismic While Drilling (SWD) Concept for Geothermal Drilling

Abstract

The increase in the use of renewable energies poses a great challenge today and in the future. In order to raise the percentage of geothermal energy in heat and power production in Germany, the use of low enthalpy systems is the only possibility. Low-enthalpy geothermal reservoirs can be found in depths between 2.000 and 5.000 meters, exhibiting reservoir temperatures between 80 and 170 °C. Typical reservoir types are fault zones in between or at the basis of sedimentary systems with a thickness of a few meters to decameters. For their development, common oil and gas drilling technologies are used. Well designs are typically based on geological interpretations of conventional 2D- and 3D-seismic data. Subsurface interpretations based on these data have a resolution of typically 10 to 60 meters. This limited resolution can cause misinterpretation in the determination of the position or lead to an oversight of fault structures. In the worst case, a potential reservoir may not be detected.
The goal of the project described in this paper is to develop a Seismic While Drilling (SWD) tool which can be integrated into the bottom-hole assembly of the drill string and which transmits seismic data to the surface during the drilling process. This approach shall allow geological structures to be identified that are located ahead of the drill bit in the drilling direction. Hence, drilling path adjustments will be possible during operation. A first prototype of an SWD tool was built and tested in a research mine.