Contemporary drilling systems for wellbores have serious limitations on how wide and deep wellbores can be drilled. In conventional systems, mud is injected through the pipe and exits through several orifices at drill-bit and circulates up between the pipe and wall of the wellbore providing a necessary stream for cutting to be excavated. Increasing the size of the drill-bit (wellbore) and/or increasing the depth of the wellbore it requires a tremendous increase of pressure inside the pipe to form a sufficient stream of fluid up for cuttings to be excavated. Also, the wellbore has a gradually smaller diameter with each subsequent section because of the casing. The presented system provides a solution for drilling deeper and wider wellbores with a constant diameter. The presented system consists of a motorized drill head; a separate excavation line; a separate fluid delivery line, and a separate closed-loop cooling line engaged with Binary Power Unit on the ground surface. The presented drilling apparatus has retractable bits on the motorized drill head. The casing of the wellbore can be built during the drilling process. The drilling apparatus consists of the elevator sliding over the drilling/excavation/heat exchange apparatus delivering and installing casing sheets and concrete. The elevator also has an expendable chamber, and adjacent containers above for delivering air, and concrete. The containers with air also can be used for providing buoyancy thus minimizing the weight issue during the disassembling process. The diameter of the excavation line and rate of flow of mud and cuttings through it and the diameter of the fluid delivery line and rate of fluid flow through it are in balance requiring only a limited fluid column at the bottom of the wellbore. The fluid column may exist through the whole wellbore to sustain the wellbore during the drilling process, and later for better conduction of the heat, but not for the excavation purpose. The excavation process continues regardless of the diameter of the drill head (wellbore); therefore, this method eliminates well-known drilling limitations relative to the depth and diameter of the wellbore.

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