Multi-stage liquid nitrogen fracturing system and method for hot dry rock geothermal well

Abstract

The invention discloses a multi-stage liquid nitrogen fracturing system and a multi-stage liquid nitrogen fracturing method for a hot dry rock geothermal well. The system comprises a nitrogen gas inlet pipeline and a liquid nitrogen outlet pipeline of a high-pressure liquid nitrogen container which are respectively connected with a main nitrogen gas input pipeline and a main liquid nitrogen discharging pipeline; an emptying pipeline is provided with emptying valve; the liquid nitrogen outlet pipeline is connected with a coiled tubing; a gas inlet and a driving air inlet of a gas supercharger are respectively connected with a gas outlet of a nitrogen gas bottle group and an air outlet of an air compressor; a gas outlet of the gas supercharger is connected with a gas inlet end of the main nitrogen gas input pipeline; an inlet end of a low-temperature liquid nitrogen pump is connected with a liquid nitrogen storage tank; and an outlet end of the low-temperature liquid nitrogen pump is connected with a liquid nitrogen inlet pipeline of a high-pressure liquid nitrogen container. The method comprises the following steps: establishing the connection between the system and the coiled tubing; removing air and moisture from the system; filling liquid nitrogen; fracturing the liquid nitrogen stage by stage; completing fracturing operation of each section in sequence; and closing a well and recording pressure. According to the system and the method, the fracture initiating pressure of a fracture of a hot dry rock reservoir can be reduced; the water consumption is reduced; and environment-friendly high-efficiency development of hot dry rock geotherm can be realized.

Description

technical field [0001] The invention belongs to the technical field of geothermal development, and in particular relates to a liquid nitrogen multistage fracturing system and method for geothermal wells of dry hot rocks. Background technique [0002] Hot dry rock geothermal resources are a kind of clean and renewable energy. Realizing its large-scale development is of great significance for promoting the adjustment of national energy structure and ensuring energy security. The potential of hot dry rock resources in my country is huge. The hot dry rock resources within the range of 3-10km underground are equivalent to about 860 trillion tons of standard coal, which is an important national strategic energy. Due to the extremely low permeability of the hot dry rock reservoir (0.001-0.1mD), it is necessary to artificially transform the hot dry rock reservoir to form an enhanced geothermal system in order to efficiently extract the heat stored in the hot dry rock. Hydraulic fra...

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Problems solved by technology

In addition, the fracturing period of hot dry rock reservoirs is long and large-scale, which consumes a lot of water resources, which will cause a series of environmental problems such as excessive consumption of water resources and pollution.

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