A rock-exploitation method based on thermodynamic cycles utilizing an in-situ energy source, which includes sinking at least one well as far down as, or deeper than a producing horizon, admitting stratal fluid into the well, discharging the fluid from the well above or below the producing horizon, and injecting a heat-carrying agent into the well where it circulates and exchanges heat with the rock through the fluid which is in contact with the rock and acts as a heat-carrying agent in an underground circuit including said means for admission of fluid, a section of the well between the fluid inlet and the fluid outlet, and the fluid-permeable rock mass adjacent to said section of the well.