Downhole Pumps
Downhole submersible pumps are a key component for large scale power generation from geothermal resources. Both Hydrothermal and Enhanced Geothermal Systems require a robust serviceable pump capable of bringing heat to the surface. Both literature review and interviews with geothermal experts confirmed the importance of such a pump in advancing the development of the technology.
Though validated by multiple sources, the DOE Geothermal R & D agenda through 2015 sets out the technical barrier of a pumping system. In the area of interwell connectivity barriers “downhole pumps capable of withstanding EGS conditions while sustaining sufficient EGS flow rates do not yet exist”. They set 2012, 2015 and 2020 targets. From 2015:
By 2015 improve the performance of downhole pumps, especially ESPs, to operate at temperatures of 275C, mass flow rates up to 80 kg/s, setting depths as great as 2 km for well bores 6 5/8 to 10 5/8 and operating at pressures up to 200bar.
The critical attributes of such a pump are temperature tolerance and low service needs. Initially, such a pump will exploit the limited high temperature (250C plus) locations (power production per well is a function of temperature). Accelerated investment in geothermal will depend on the flow of high temperature resources, that will in turn offset shortcomings in the knowledge of managing geothermal fields. With time, such pumps will be installed into lower temperature sites. At that point, reliability and robustness will be key operating features.
