An Analytical Geothermal Model and Its Implications for Geothermal Engineering Design
Keywords:
Geothermal, Heat transfer, Clean energy, Heat conduction, SustainabilityAbstract
This study presents an analytical model to predict the temperature of the produced fluid and the cumulative heat production from a geothermal reservoir by cycling cold water injection. First, the solutions of the temperature of the produced fluid, the net heat production rate and the cumulative heat production are derived. Then each parameter of the analytical model is analyzed to study the sensitivity and the implications of designing a geothermal project. The derived solutions may be further used to develop other solutions or methods for geothermal engineering. From the quantitative analysis of model results, it is found that a waiting time of year is needed to produce heat until injected water breaks through in a dry geothermal system. After the breakthrough, the temperature of produced fluid is low compared to the initial reservoir temperature. This reduces the heat output. To improve that, the production rate must be high, but the residence time must be long. From that point of view, when designing a practical project, a horizontal well is preferred because of a high rate, and a large well spacing is preferred because of longer residence time. Formation thickness or injected fluid temperature does not affect the heat production significantly, but thermal conductivity does.
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