A geothermal well comprising in a wellbore formed in the Earth's crust: a fist tube comprising at least one opening in a first depth and having a first inner diameter, a first outer diameter, and a side wall which is thermally insulated along at least a segment thereof; a second tube having a closed bottom in a second depth, a second inner diameter larger than the first outer diameter, and a second outer diameter; a third tube , formed by a casing tube, having a closed bottom in a third depth, a third inner diameter larger than the second outer diameter, and a third outer diameter, wherein the first tube is inside the second tube , a first interspace is formed between the first tube and the second tube , wherein the first tube has at least one opening in fluid communication with the first interspace , wherein the second tube is inside the third tube , a second interspace is present between the second tube and the third tube ; a plurality of through-holes are formed in the second tube above the bottom of the third tube , which allow fluid communication between the first interspace and the second interspace , a first sealing element is disposed in the first interspace above the through-holes for preventing an upward flow of fluid in the first interspace , and a heat insulating material is disposed in at least a portion of the first interspace above the through-holes , characterized in that the second tube is formed by a casing tube, wherein the third depth is smaller than the second depth, the first depth is smaller than the second depth, and the first depth is larger than the third depth, and the side wall of the first tube in the third depth is devoid of through-holes. a fist tube comprising at least one opening in a first depth and having a first inner diameter, a first outer diameter, and a side wall which is thermally insulated along at least a segment thereof; a second tube having a closed bottom in a second depth, a second inner diameter larger than the first outer diameter, and a second outer diameter; a third tube , formed by a casing tube, having a closed bottom in a third depth, a third inner diameter larger than the second outer diameter, and a third outer diameter, wherein the first tube is inside the second tube , a first interspace is formed between the first tube and the second tube , wherein the first tube has at least one opening in fluid communication with the first interspace , wherein the second tube is inside the third tube , a second interspace is present between the second tube and the third tube ; a plurality of through-holes are formed in the second tube above the bottom of the third tube , which allow fluid communication between the first interspace and the second interspace , a first sealing element is disposed in the first interspace above the through-holes for preventing an upward flow of fluid in the first interspace , and a heat insulating material is disposed in at least a portion of the first interspace above the through-holes , characterized in that the second tube is formed by a casing tube, wherein the third depth is smaller than the second depth, the first depth is smaller than the second depth, and the first depth is larger than the third depth, and the side wall of the first tube in the third depth is devoid of through-holes. <EOS>