Closed deep geothermal energy collecting system and method

Abstract

The invention provides a system for collecting thermal energy from underground deep high-temperature rock with low porosity and low permeability. The system comprises a thermal production well, at least one fracturing well, a full-closed casing pipe, a ground thermal energy utilizing device and a pipeline circulation system, wherein the fracturing wells are located near the thermal production well, meshed cracks are formed in the underground deep high-temperature rock according to a fracturing method, an artificial geothermal reservoir is formed, and a thermal energy collecting section of thethermal production well is partially or wholly wrapped with the artificial geothermal reservoir; and the pipeline circulation system is used for making a heat exchange working medium flow downwards inthe casing pipe along an interlayer and then circulate upwards through a center pipe. With the closed design, matter exchange with the underground environment is avoided, the defects of high energy consumption, needs to reinjection, ground thermal pollution, chemical pollution and ground collapse due to direct use of geothermal water are overcome, and the heat exchange efficiency of a closed deepunderground heat exchange system is improved in an artificial fracturing mode.

Description

technical field [0001] The invention relates to a deep geothermal energy collection system and a method for collecting deep geothermal energy by using the collection system, in particular to a method for extracting geothermal resources with economic value from low-porosity, low-permeability underground deep-layer high-temperature rock mass systems and methods. Background technique [0002] The low-porosity, low-permeability underground deep-layer high-temperature rock mass referred to in the present invention refers to a hot rock mass without water or steam, with a temperature range of 100-650 ° C, generally located 2.5-10 km below the surface, including various Tight sandstone, metamorphic rock or crystalline rock mass. This type of rock mass has a high temperature, is widely distributed, and contains a large amount of deep geothermal resources. It is conservatively estimated that the energy contained in the earth's crust is equivalent to 30 times the energy contained in a...

AI Technical Summary

Problems solved by technology

[0004] In the traditional closed heat exchange system (coaxial tube, vertical well), there are two obvious defects: 1) The inner tube of the coaxial tube is usually not treated with strict vacuum heat insulation, so that the heated fluid flows from the inside When the pipe rises to the ground, a lot of heat energy is lost; 2) The heat exchange area of ​​the vertical heat exchange well is very limited, and only the outer surface of the vertical cylinder is in contact with the rock formation; in the vertical direction, the ground temperature rises slowly and linearly, and there is not enough Heat source; in the hot dry rock mass lacking water, only the heat conduction of the rock exchanges heat with the fluid in the heat exchange well, and the heat conduction power of the rock is much smaller than the heat transfer power of the fluid

Obviously, the above-mentioned requirements are very strict, and in unforeseen and uncontrolled formations containing natural fractures, the success rate of obtaining artificial fractures that meet the requirements is extremely low

Therefore, the fatal flaw of EGS is that it is very poorly controllable

In addition, due to the direct contact between the injected and produced water and the underground environment, the possibility of causing surface environmental pollution is high.

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