Discussion on the calculation of the rights protection radius of the geothermal well for stratified thermal reservoir

In order to ensure the sustainable exploitation of geothermal resources and prevent the occurrence of thermal breakthrough during the process of geothermal water reinjection, the authors systematically summarized the calculation formulas of the rights protection radius of the geothermal well in this paper. Three shortcomings in the calculation method of the rights protection radius of the geothermal well were identified through theoretical derivation. (1) The parameter f, which is defined as the ratio of the specific heat of water to that of thermal reservoir rocks, is defective. (2) The value of the thermal reservoir recovery rate defined as 0.15 is relatively unilateral, which is not applicable for geothermal wells with different lithology. (3) The calculation time is fixed as 36 500 d, which is not appropriate for geothermal wells with interval development. Based on the problems above, the authors redefined the parameter f and used variables to replace the previous thermal reservoir recovery rate and exploitation time, which can be identified according to different thermal reservoirs and specific exploitation time. By comparison of the applicable conditions of different calculation formulas of the rights protection radius of the geothermal well, the authors proposed that different calaulation formuas should be chosen based on the relationship of the size between β^-1-α and 3λ. And by comparison of the rights protection radius calculation formulas for the mining well and the recharge well, it is found that the rights protection radius of the mining well is always bigger than that of the recharge well. Finally, Shuiwen residential area of Decheng district was taken as an example to verfity the theoretical results.