While the TDF represents a mature field, many geothermal fields will start with a single injectionproduction pair. We define an isolated doublet (ID) as an injection-production well pair with non-zero well spacing located far from any other wells, so there is no outside hydraulic or thermal influence. Many geothermal fields will start as an ID and become a TDF as development continues. Therefore, we analyze IDs and TDFs, which act as bounding cases.