| Abstract |
Increase in global warming, population, and reduction in oil and gas reserves, it is necessary to find more source of energy which will be sustainable in the upcoming future. Geothermal energy is a renewable and clean source of energy. Due to costs associated with the exploration, drilling and production of this clean energy sometimes it is not economical to develop as geothermal power plants. These cost barriers can be avoided by using efficient turbines and pumps which will reduce the cost of getting this hot energy out of the earth. Especially in the case of Enhanced Geothermal Energy, which involves in creating a fracture network in places where there is presence of hot rock but, lacks in permeability and geo-fluid; it is very important to reduce the cost of operation. With advancement in the technology of efficient and economical turbines, pumps and drilling operations can make such systems feasible. Along with the technology, it is very important to maintain these reservoirs at a certain temperature, for a long period of time, for economical energy extraction. Fenton Hill-1 hot dry rock experiment was successfully simulated and matched with field data by using MULTIFLUX code (Danko and Bahrami, 2013). The reservoir subjected to a continuous coolant fluid circulation is first modeled and the pumping power and the geothermal energy recovery are evaluated for base case characteristic. Keeping the reservoir properties same, EGS reservoir was subjected to various and variable injection rates with on-off circulation, similar to a huff-puff operation. The variable flow rate and pressure affects the fracture extension in both the longitudinal and aperture directions. This non-linearity allows for increasing the active heat transport surface area. This work shows the advantages of using variable and various flow rates on operation of an EGS reservoir. Temperature decline and the net thermal power generated from the reservoir are compared with the base case of the Fenton Hill-1 field study with different injection scenarios discussed. Fenton Hill experiment was divided into two parts, Fenton Hill Phase-1 and Fenton Hill Phase-2. Phase 1 was started in 1974 and completed in 1980 and Phase-2 was started in 1979. Fenton Hill Phase-1 comprises the development and research on a 3 km deep reservoir with a temperature of 200°C, while Fenton Hill Phase-2 dealt with a deeper reservoir which was at 4.4 km and about 300°C (Tester, et al., 2006). Effect of flow modulation is discussed for 75 days and at 1 day interval as well as 1 year for 1 week interval is also discussed. Different flow rates and time durations are considered to show that the flow modulation is helpful even if we change the injection flow rate and/or the time span. |