| Title | An Innovative Concept of Regenerative Enhanced Geothermal Systems: A Field Case Study of The North German Basin |
|---|---|
| Authors | Muhammad Haris, Michael Zhengmeng Hou, Wentao Feng |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Regenerative enhanced geothermal system, Hydraulic fracturing, Heat production, Electricity generation, Energy storage |
| Abstract | Geothermal energy is clean, renewable, efficient, independent of weather, and available in significant amounts. However, utilizing an effective approach has prime and foremost importance for the substantial exploitation of geothermal energy. In 2009, the GeneSys EGS project in the North German Basin was chosen to produce 2 MW of thermal energy to fulfill the residents' energy requirement. However, the low production rate and high-temperature decline caused the development of a salt plug inside the tubing due to cooling-induced precipitation. The salt plug was removed using the coil tubing technique; however, the high-temperature reduction (more than 50 oC) and extreme water salinity were major reasons for the project breakdown. The geothermal exploitation through GeneSys EGS using a single well with low flow rates could not provide acceptable results. In this work, an innovative concept of a regenerative enhanced geothermal system is proposed, and the MHH-GeneSys region in the North German Basin is investigated for geothermal energy production as well as surplus renewable energy storage. Numerous thermo-hydro-mechanical coupled simulations have been conducted to obtain massive hydraulic fractures, and subsequently, heat and electricity potential have been forecasted. Multiple hydraulic fracturing results indicate that stress shadow considerably disturbs the subsequent fracture geometry, which ultimately alters the heat contribution of individual fractures. The energy production results show that the tendency of temperature decline in each fracture area increases with increased flow rate and well spacing. The total optimized installed power capacity of the whole projected EGS during 30 years drops from 14.34 MW to 10.16 MW, 10.66 MW to 7.04 MW and 7.17 MW to 4.14 MW for 288 L/s, 192 L/s and 96 L/s flow rate, respectively. The expected total cost of the multi-well multi-hydraulic fracture system is estimated at $ 120.47 million, having significant shares of drilling and operation & maintenance costs. The levelized cost of electricity (LCOE) is calculated at 0.0501 $/kWh, which is significantly economical. Moreover, after electricity production, the accumulated hot fluid can be used for direct heat applications. The high flow rates are beneficial in reducing the temperature reduction rate, leading to lower salt crystallization issues. Lastly, to examine the surplus energy storage/recovery potential of the energy-depleted deep geothermal reservoir, continuous hot fluid injection/production cycles have been evaluated by adopting equal fluid volumes and time. It has been estimated that high energy recovery can be obtained by critically analyzing the continuous injection/production cycles. In addition, the stored energy can increase the life of the geothermal project by reducing the reservoir temperature reduction rate. The energy storage cycles can further help remove salt crystallization in wells. |