| Abstract |
The geothermal industry predominantly relies on line shaft pumps, as electric submersible pumps have failed to penetrate this market. The current pump technology is cumbersome, expensive, and has poor service cycle longevity. The industry has been looking for different solutions for many years without success.1 GeoTek Energy, LLC has been developing the Gravity Head Energy System for several years2 and is now developing a related gravity energy based technology, the Gravity Head Pump3 (?GHP?) for production pumping of geothermal and moderate temperature oil wells with high water cuts. This paper will focus on the application of the GHP to geothermal power production. The system uses the force of gravity instead of fighting it, relying on the geothermal heat from the produced geothermal fluid to heat and vaporize a refrigerant or organic working fluid and benefitting from the resulting sub-surface thermosiphon loop. To reduce costs, the GHP utilizes the same low-boiling point working fluid as the surface binary system. This working fluid has a lower boiling temperature than water, so it can extract enough heat from moderate temperature produced fluids to vaporize it and drive the turbine generator. To operate the GHP, a portion of the working fluid is directed into the production well in a closed system and rotates an expander which is connected via magnetic coupling to drive a pump that lifts the geothermal brine to the surface. The high temperature/ lower pressure working fluid returns to the surface using the natural thermosiphon effect. There, it is used to partially heat the surface working fluid before being condensed and flowing back into the well. The advantages of the GHP include providing a pump that works in a broad temperature range with a longer service cycle, reducing operating and maintenance costs by allowing for wireline retrieval, elimination of the electricity load incurred for either a shaft-drive or electric submersible pump, and increasing the net power produced from a binary cycle power plant. |