System for drilling the ground to obtain circulation of fluid in a plant for the exploitation of geothermal energy

Abstract

A system for high-depth drilling of the ground aimed at reaching hot rocks for extraction of geothermal energy by means of introduction of a heat-conveying fluid and extraction thereof after adequate heating uses just one borehole containing two coaxial tubes: an internal tube ( 3, 11, 13 ), through which the cold fluid is introduced, and an external or coating tube ( 4, 6 ), through which said fluid returns to the surface after it has been heated by the hot rocks either directly or through said coating tube.

1 . A system for high-depth drilling of the ground aimed at reaching hot rocks for extraction of geothermal energy by introduction of a heat-conveying fluid and extraction thereof after adequate heating, said system comprising one borehole containing two coaxial tubes: an internal tube, in which introduction of the fluid is carried out, and an external or coating tube, along which said fluid returns to the surface after it has been heated by the hot rocks either directly or through said coating tube.  
   
   
       2 . The system according to  claim 1 , wherein the internal tube is thermally insulated to minimize passage of heat between the descending fluid and the ascending fluid.  
   
   
       3 . The system according to  claim 1 , wherein the external tube is thermally insulated with the exception of a portion in contact with the hot rock.  
   
   
       4 . The system according to  claim 1 , wherein the external tube is closed at the end and extends throughout the length of the piping, wherein the internal tube for introduction of fluid terminates at a small distance from the end of the external tube.  
   
   
       5 . The system according to  claim 1 , wherein the fluid returns to the surface inside the external tube, after it has been heated by the hot rocks through said tube that is in direct contact with the hot rocks.  
   
   
       6 . The system according to  claim 1 , applied to fractured rocks, wherein the dispersion of fluid is small, wherein the internal tube extends beyond the end of the external tube, with a first portion and a second portion that is not coated for introduction of the fluid into the fractured rock through said second portion and its recovery in an area corresponding to the final mouth of the external tube.  
   
   
       7 . The system according to  claim 6 , wherein the main borehole is drilled inside the hot rock without any coating for a certain section, beyond which the internal tube extends.  
   
   
       8 . The system according to  claim 6 , wherein the first portion of internal tube is cemented to the rock, from where the portion that is not coated of the main borehole terminates as far as where the second portion of internal tube starts, to cause return of the heated fluid only through the cracks of the rock up to the second portion that is not coated of the main borehole.  
   
   
       9 . The system according to  claim 6 , wherein the internal tube is thermally insulated.  
   
   
       10 . The system according to  claim 6 , wherein the external tube is thermally insulated.  
   
   
       11 . The system according to  claim 6 , wherein the internal tube branches off in a plurality of branches to increase the surface of infiltration of the fluid in the rock.  
   
   
       12 . The system according to the  claim 1 , wherein a portion of tube in contact with the hot rock is deviated in a nearly horizontal direction to increase the length of path useful for heat exchange in the case where the hot layer is of small depth.