| Title | Sustainability of Geothermal Doublets |
|---|---|
| Authors | Abdurrahman Satman |
| Year | 2011 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Doublets, sustainability, temperature distribution, lumped parameter model |
| Abstract | The heat content of a hydrothermal aquifer can be utilized by producing the aquifer’s hot fluid whereas the waste cooled water is reinjected into the aquifer and such a scheme is called the doublet operation. The produced hot fluid is continuously replaced by cooled injected water. After the thermal breakthrough time the temperature of the produced fluid decreases. However if after a time the field is shut-in the natural energy flow will slowly replenish the geothermal system and it will again be available for production. Therefore when operated on a periodic basis, with production followed by recovery, doublets are renewable and sustainable. This paper addresses renewability and sustainability concept by considering a lumped parameter model with new and simple analytical solutions. An analytical approach is presented to analyze the parameters involved to estimate the time that a doublet takes to fully recover to its original state after shut-down at some production time. A simplified lumped-parameter type of an approach to model the temperature behavior of a single liquid-phase reservoir is discussed here. New analytical equations and correlations are presented to investigate the temperature behavior of doublets. Emphasis is given to understand the characteristics of temperature recovery following some production period. These equations and correlations can be used to design the doublets. Corresponding calculations with porous reservoir models for a doublet field operation given in the literature demonstrate the validity of the analytical expressions given in this paper. |