End-of-life production or injection wells may be converted into wellbore heat exchangers for geothermal energy extraction. Whether this conversion is technically and economically feasible depends on several factors such as geothermal potential of the formation, well depth, and working fluid circulation parameters. Here we present a case study where we analyze these parameters and determine their optimum operational brackets. We focus on repurposing active wells that are located in regions with high geothermal potential in the state of Mississippi.

Geothermal gradient map of the state of Mississippi was used to select potential candidate wells. Well logs of these candidate wells were used to find formation temperature and other properties such as well diameter and depth. Next, we conducted heat transfer calculations to estimate the temperature rise of various working fluids as a result of circulating inside these wellbores. We ran sensitivity analyses to determine the effect of circulation rate, tubing insulation, and time. Finally, we estimated the power production potential of each well.

Our results indicate that geothermal energy production through repurposed end-of-life wells may be viable depending on well depth and geothermal potential of the region. With insulated tubing, the thermal energy delivered by a number of candidate wells is sufficient for a small-scale binary power plant with organic Rankine cycle.

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