| Title | Development of Energy Supply Systems Using Abandoned Deep Wells |
|---|---|
| Authors | Hikari Fujii, Satoshi Akibayashi, Ryuichi Itoi |
| Year | 2005 |
| Conference | World Geothermal Congress |
| Keywords | downhole heat exchanger, numerical simulation, deep wells |
| Abstract | Abandoned deep geothermal and oil/gas wells have enormous potential for the supply of energy to the neighboring communities if converted to a ground heat exchanger (GHE). Since the well re-completion costs are significantly cheaper than those of drilling new wells, the energy supply system could be a highly cost-effective choice. In this study, field tests and numerical simulation studies were performed to demonstrate the effectiveness of the energy supply systems using abandoned deep wells. An abandoned geothermal well of 635m deep was converted to a GHE in Akita Prefecture, Japan, to supply heated water to be mixed with geothermal steams for producing hot spring water. With the circulation of river water through the GHE, the well currently supplies over 100kWt of heat stably without any outside power supply. A numerical model with the consideration of forced convection by groundwater flow was developed to simulate the past heat extraction performance and to improve the well designs and the operation strategies. The simulation results showed good agreement with the measured heat extraction performance, while the use of low thermally conductive inner pipes was proposed to enhance the heat extraction rate. A conversion plan of a depleted gas well of 2637m deep in Niigata Prefecture, Japan, was developed with the use of the same simulation model. The numerical simulation showed that the well could supply over 150kWt of heat with a water circulation rate of 400L/min. The numerical simulation also suggested that the use of low thermally conductive inner pipe is important to maximize the heat extraction rate. |