Thermodynamic Modeling of the Advanced Geothermal System Using Inclined Well Applications

Abstract

The advanced geothermal system (AGS), also called the closed-loop geothermal technology, requires extremely long horizontal wellbore completion to compensate the deficiency for conductive heat exchange in deep reservoirs, which is technically challenge. The AGS using inclined well configuration has been proposed to improve its efficiency, but it lacks a comprehensive and quantitative evaluation in public domain. In this study, analytical models based on Duhamel’s convolution and natural coupling methods are developed to evaluate the performance of the inclined configuration. The results suggest that the inclined wellbore system can improve the outlet temperature performance of a typical horizontal configuration by 16 %. The inclined system also shows a constant temperature gain (9 °C/km in this case study) for unit increment in lateral length. In multilateral applications of the inclined well system, our sensitivity tests indicate that wellbore spacing can have significant impact on the heat energy production performance due to wellbore interferences if the distance between wells is small in 3D space. At least a 50 m distance between any two wellbores is recommended for the multi-lateral wellbore system in the well pad design. In general, 20 % (3 MWth) more heat energy can be generated and almost 1000 GWhth more heat energy could be produced at the end of 30 years by using a standard 10-laterals inclined well system in our case study.