The invention discloses an underground enhanced heat exchange method for a closed heat removal
system, and belongs to the field of
geothermal energy development and utilization. A vertical well is drilled according to the depth and thickness of a heat reservoir, a casing
pipe is put down and well cementation is carried out, a central heat preservation
pipe is arranged in the casing
pipe, and an annular space between the casing pipe and the central heat preservation pipe forms a vertical well annulus; casing lateral windowing is carried out on the vertical well section corresponding to the
thermal reservoir, a plurality of
branch well holes are drilled, or volume fracturing is carried out to form
micro cracks; filling a high-thermal-
conductivity material in the multilateral well hole / microcrack, transforming the
thermal reservoir and supporting the transformed space to form a high-thermal-
conductivity area in the
thermal reservoir, and plugging the lateral multilateral well hole to complete the transformation of the thermal reservoir; a heat exchange working medium is injected through a high-pressure pump through a vertical well annulus, is pumped out of the central heat preservation pipe after being subjected to closed type sufficient heat exchange with the transformed heat storage layer, and
geothermal energy utilization is achieved through the
heat exchanger. The defects of a traditional closed heat removal
system are remarkably overcome, the heat removal temperature is increased, the heat removal service life is prolonged, and development and utilization of medium-deep
geothermal energy are accelerated.