Closed well loop for a geothermal system
A closed well loop is provided for a geothermal system. The closed well loop includes a well (single well) that traverses a subterranean formation to extract heat from the subterranean formation. The well includes a section having an inner pipe that is supported inside an outer pipe in a pipe-in-pipe arrangement. The inner pipe has an interior flow channel that defines a first flow path for circulating working fluid, and the annulus between the inner pipe and the outer pipe defines a second flow path for the circulating working fluid. The well can be configured to extract heat from the subterranean formation and transfer heat to the circulating working fluid that flows in the first and second flow paths. The inner pipe can include a thermally-insulative piping system that reduces the amount of heat transferred from the circulating fluid that flows in the first and second flow paths within the well.
1 . A closed well loop for a geothermal system, the closed well loop comprising:
a well that traverses a subterranean formation to extract heat from the subterranean formation, wherein the well includes a vertical section and at least one lateral section that extends laterally and downward away from the vertical section, wherein the at least one lateral section has a toe segment that is located at, or extends to, a depth below a bottom of the vertical section, wherein the vertical section includes an inner pipe, wherein the inner pipe is supported inside an outer pipe in a pipe-in-pipe arrangement, wherein the inner pipe extends to a depth in the vertical section below an intersection of the at least one lateral section and the vertical section, wherein the inner pipe has an interior flow channel, wherein the interior flow channel defines a first flow path for a circulating working fluid, wherein an annulus between the inner pipe and the outer pipe defines a second flow path for the circulating working fluid, wherein the inner pipe includes a thermally-insulative piping system, wherein the thermally-insulative piping system reduces an amount of heat transferred from the circulating working fluid at a higher temperature to the circulating working fluid at a lower temperature, and wherein the circulating working fluid flows in the first flow path and the second flow path within the well;
an isolation packer disposed within the vertical section, wherein the at least one lateral section intersects the vertical section above the isolation packer; and
at least one lateral injection manifold that extends laterally and downward from the vertical section and intersects the toe segment of a corresponding lateral section, wherein the at least one lateral injection manifold intersects the vertical section below the isolation packer.
2 . The closed well loop according to claim 1 , wherein:
at least part of the at least one lateral section is configured to support convective circulation of the circulating working fluid.
3 . The closed well loop according to claim 1 , wherein:
the thermally-insulative piping system includes a continuous layer of thermally-insulating material applied to or otherwise disposed about an inner diameter surface of the inner pipe for at least part of the vertical section.
4 . The closed well loop according to claim 1 , wherein:
the thermally-insulative piping system includes a continuous layer of thermally-insulating material applied to or otherwise disposed about an outer diameter surface of the inner pipe for at least part of the vertical section.
5 . The closed well loop according to claim 1 , wherein:
the thermally-insulative piping system includes a vacuum insulated pipe; and the vacuum insulated pipe forms the inner pipe for at least part of the vertical section.
6 . The closed well loop according to claim 1 , wherein:
the first flow path defined by the interior flow channel of the inner pipe is configured to carry the circulating working fluid at the lower temperature downward within the well from a surface toward a hot zone of the subterranean formation; and
the second flow path defined by the annulus between the inner pipe and the outer pipe is configured to carry the circulating working fluid at the higher temperature, the circulating working fluid at the higher temperature having been heated by thermal energy extracted from the hot zone of the subterranean formation, upward within the well away from the hot zone of the subterranean formation toward the surface.
7 . The closed well loop according to claim 1 , wherein:
the outer pipe includes pipe that is part of casing that lines a wellbore wall of the vertical section.