| Abstract |
As the demand for energy continues to grow with population in emerging countries, use of alternative renewable sources of energy is imperative for the near future. The impending climate change and current economic development have forced a shift to more sustainable sources of energy like geothermal, solar, and wind. The widening of supply-demand gap over years has led to global energy crisis and resulted in exhaustive use of non-renewable natural resources to meet the energy demands. This extensive use of fossil fuels has been made possible by the current development of human civilization. However, burning of fossil fuels, which are becoming increasingly scarce, has led to an increase in emissions of carbon dioxide, which is a greenhouse gas, into the atmosphere. This, in turn, has also led to a detrimental impact on the environment and an imbalance in the natural ecosystem. Geothermal energy is a green, environment-friendly, low carbon, renewable and sustainable source of energy since there are relatively less investments and is pollutant-free. The major advantage of geothermal energy over other sources of renewable energy is that the underground heat/energy mining does not depend on the weather conditions and geothermal power runs at a much higher load factor than wind or solar. Nearly 40% of the total investment cost that goes into setting up a geothermal plant is the drilling cost. However, this problem can be potentially tackled by utilizing the currently decommissioned and abandoned oil and gas wells for geothermal purposes. Retrofitting an abandoned well to produce geothermal energy also saves the cost of exploring sites for geothermal fields. The estimated potential for the geothermal energy that can be harnessed in India is about 10 million kW. In this study, abandoned oil and gas wells have been simulated as a source of geothermal power to generate electricity. Simulations have been performed by coupling thermal reservoir with bore well heat transfer and laminar flow model. Water, which is chosen as working fluid is circulated down through the annulus and extracted back through the shorter insulated inner pipe. A parametric study to assess the production temperature using finite element method with various operating parameters such as injection mass flow rate, re-injection temperature, well depth and geothermal gradient is performed. The results of this study indicate that heat extraction rate increases with increasing mass flow rate as well as the well depth while all other injection parameters remain constant. At higher injection temperature, the net heat extraction rate from the reservoir decreases with time due to lower temperature difference between injected fluid and reservoir formation temperature. |