NOVELTY - The system (1) has a casing chamber that is provided with a casing chamber upper portion fluidly communicating with casing opening and central line bottom opening. A working fluid return flow path (13) is extended downwardly through the casing chamber and central line chamber, and provided with a return path inlet fluidly communicating with one of working fluid return interface. A working fluid supply flow path (54) is extended upwardly through one of casing chamber and central line chamber, and provided a supply path outlet fluidly communicating with working fluid supply interface.    USE - Renewable energy, single well, primarily self-flow, geothermal heat/power production system for use with well extending into subsurface formation.    ADVANTAGE - The sub-surface structures defining a working fluid flow path can be insulated to increase the operational efficiency of the production system, and to ensure a self-generating working fluid flow. The safety of the system can be achieved. The maintenance cost of the system can be reduced. The system can reduce the parasitic power draw associated with a liquid pump used during system operation, to reduce system operation time, and to improve the overall environmental impact. The system can use water as the working fluid in the closed loop, sub-surface portion of the system, so as to avoid the expense and deleterious environment effects associated with the refrigerants.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of the single well, self-flowing, geothermal energy extraction system in which a cool liquid phase working fluid flows to the bottom portion of a deep well, and the working fluid transported up and out of the well through the insulated supply line, after acquiring geothermal heat.    Renewable energy, single well, primarily self-flow, geothermal heat/power production system (1)    Working fluid (2)    Well casing (9)    Working fluid return flow path (13)    Working fluid supply flow path (54)