Systems and methods for drilling geothermal wells
Systems and methods for drilling a geothermal well can include drilling a first borehole to a geothermal target, the first borehole defining a longitudinal axis; and drilling a first portion of a second borehole having a first end and a second. The first end of the second borehole extends from the first borehole, the first portion extends downwardly and outwardly from the longitudinal axis of the first borehole, and the first portion of the second borehole is in fluid communication with the first borehole. The techniques can include drilling a second portion of the second borehole. The second portion extends downwardly and towards the longitudinal axis of the first borehole, the second end of the second borehole extends to the first borehole, and the second portion of the second borehole is in fluid communication with the first borehole. Casing can be provided and a geothermally active region surrounding the wellbores may be fractured, thus providing a geothermal region with a greater surface area through which a fluid may flow.
1 . A method for creating a geothermal well, the method comprising:
drilling a first borehole to a geothermal target, wherein the first borehole defines a longitudinal axis;
drilling a first portion of a second borehole having a first end and a second end, wherein the first end of the second borehole extends from the first borehole, the first portion extends downwardly and outwardly from the longitudinal axis of the first borehole, and the first portion of the second borehole is in fluid communication with the first borehole;
drilling a second portion of the second borehole, wherein the second portion extends downwardly and towards the longitudinal axis of the first borehole, and wherein the second end of the second borehole extends to the first borehole, and wherein the second portion of the second borehole is in fluid communication with the first borehole;
wherein the first borehole is within twenty degrees of vertical, the first portion of the second borehole extends at an angle between 15 degrees and 75 degrees from the longitudinal axis of the first borehole, the second portion of the second borehole extends at an angle between 15 degrees and 75 degrees from the longitudinal axis of the first borehole, and portions of the first portion and second portion of the second borehole define a curved portion of the second borehole; and
fracturing at least a portion of a formation proximal to the second borehole; and
casing at least a portion of the first borehole that is located below the first end of the first portion of the second borehole, wherein the casing defines an annulus between the casing and an exterior wall of the first borehole and the casing forms a fluid pathway through the casing to a bottom of the first borehole, and through the second borehole and one or more fractures of the fractured portion of the formation, and then back through the annulus.
2 . The method according to claim 1 , further comprising:
drilling a plurality of second boreholes, each having a first end and a second end and a first portion and a second portion, wherein each of the first ends of the plurality of second boreholes are connected to the first borehole at a first point, and each of the second ends of the plurality of second boreholes are connected to the first borehole at a second point, wherein each first point is higher than each corresponding second point for each of the plurality of second boreholes.
3 . The method according to claim 2 , wherein the plurality of second boreholes comprise at least three boreholes.
4 . The method according to claim 2 , wherein the plurality of second boreholes are positioned around the longitudinal axis of the first borehole and radially spaced apart from one another by at least thirty degrees.
5 . The method according to claim 1 , wherein the first portion of the second borehole extends downwardly away from the first borehole at an angle of at least thirty degrees.
6 . The method according to claim 5 , wherein the second portion of the second borehole extends downwardly towards the first borehole at an angle of at least thirty degrees.
7 . The method according to claim 1 , wherein the first portion of the second borehole is drilled from a first kick off within a geothermal zone to a first location at a first distance, wherein the first distance is before a true vertical depth of the geothermal target, wherein the first borehole has a first diameter, and the second borehole has a second diameter smaller than the first diameter.
8 . The method according to claim 1 , wherein the casing comprises a thermally insulating material.
9 . The method according to claim 1 , wherein the longitudinal axis of the first borehole has an angle within 20 degrees from vertical.
10 . A geothermal well, comprising:
a well comprising:
a first well portion, wherein the first well portion extends at an angle within 20 degrees from vertical, and has a first diameter, and
a second well portion, wherein a top of the second well portion is connected to a bottom of the first well portion, and the second well portion has a second diameter, wherein the first diameter is greater than the second diameter;
a plurality of sidetrack wells, each extending from a first place on the first well portion or the second well portion to a second place on the second well portion, and each defining a fluid pathway between the first place and the second place, wherein the second well portion and the plurality of sidetrack wells extend into a thermally active formation comprising a plurality of fractures in a region;
a first casing positioned in at least the first well portion or the second well portion; and
a second casing forming an annulus between the first casing and the second casing, wherein the well is adapted to receive a fluid therein allowing flow through the first casing to a bottom of the well, then through one or more of the plurality of sidetrack wells and one or more fractures of the plurality of fractures, and then back to a surface location through the annulus.
11 . The well according to claim 10 , wherein the region is proximal to at least one of the sidetrack wells.
12 . The well according to claim 10 , wherein the thermally active formation is in a region proximal to at least part of the second well portion and includes the region including the plurality of fractures; and wherein each of the plurality of sidetrack wells is fractured.
13 . The well according to claim 10 , wherein at least one of the first casing or the second casing comprises a thermally insulating material.
14 . The well according to claim 10 , wherein each of the plurality of sidetrack wells has a first portion and a second portion, wherein the first portion of a sidetrack well is drilled from a first kick off within a geothermal zone to a first location at a first distance, wherein the first distance is before a true vertical depth of a geothermal target, wherein the well has a first diameter, and each of the plurality of sidetrack wells have a second diameter smaller than the first diameter.
15 . A method of generating energy comprising:
drilling a well, the well comprising:
a first well portion, wherein the first well portion extends at an angle within 20 degrees from vertical, and has a first diameter, and
a second well portion, wherein a top of the second well portion is connected to a bottom of the first well portion, and the second well portion has a second diameter, wherein the first diameter is greater than the second diameter;
at least one sidetrack well extending from a first place on the first well portion or the second well portion to a second place on the second well portion, and defining a first fluid pathway between the first place and the second place;
a first casing positioned in at least the first well portion or the second well portion; and
a second casing forming an annulus between the first casing and the second casing, wherein the well is adapted to receive a fluid therein allowing flow through a second fluid pathway;
fracturing a thermally active formation such that the second well portion and at least one sidetrack well extend into a region with a plurality of fractures;
pumping the fluid through the first and second fluid pathways such that the fluid travels down through the first casing to a bottom of the well, then up through of the at least one sidetrack well and one or more fractures of the plurality of fractures, and then back to a surface location through the annulus; and
generating energy using a generator adapted to receive heated fluid exiting the annulus.
16 . The method according to claim 15 , wherein the region is proximal to the least one sidetrack well.
17 . The method according to claim 15 , wherein the well further comprises two or more sidetrack wells extending from one or more first locations on at least one of the first well portion or the second well portion to one or more second locations on the second well portion.
18 . The method according to claim 17 , wherein the thermally active formation is in a region proximal to at least part of the second well portion and includes the region including the plurality of fractures; and wherein each of the two or more sidetrack wells is fractured.
19 . The method according to claim 15 , wherein at least one of the first casing or the second casing comprises a thermally insulating material.