Method for efficiently developing deep geothermal reservoir through liquid nitrogen circulating fracturing

Abstract

The invention provides a method for efficiently developing a deep geothermal reservoir through liquid nitrogen circulating fracturing. On the basis of the method, liquid nitrogen is periodically injected in a small-displacement injection-pause mode, under the action of alternating thermal stress-fluid pressure, a stress field around a rock crack of the deep geothermal reservoir is periodically changed, fatigue failure of the rock can be induced, the crack initiation pressure is further reduced, crack initiation and expansion of a crack are induced, and finally a three-dimensional crack net is formed. Meanwhile, as the liquid nitrogen injection displacement is small, the overall injection amount is low, and the pump pressure is low, the cycle index can be selected according to the crack scale, and the earthquake risk can be reduced. Therefore, the problems that conventional hydraulic fracturing is high in crack initiation pressure, single in crack, small in heat exchange area, frequent in microseism and the like can be solved, the deep geothermal reservoir fracturing effect can be well improved, the reservoir heat exchange efficiency is improved, and geothermal energy resources can be safely and efficiently developed and utilized for a target geothermal reservoir in a target area subsequently.

Description

technical field [0001] This specification belongs to the technical field of geothermal reservoir development, and in particular relates to a method for efficiently developing deep geothermal reservoirs through liquid nitrogen circulation fracturing. Background technique [0002] When developing geothermal energy resources, it is usually necessary to form a complex fracture network in the reservoir through fracturing technology to create efficient heat extraction channels. [0003] However, deep geothermal reservoirs often have the characteristics of high temperature, high strength, and large stress. If the existing hydraulic fracturing method is directly used for fracturing, it is prone to problems such as high fracture initiation pressure, single fracture, and small heat transfer area. problems, leading to poor fracturing effects, and prone to micro-earthquakes, etc., affecting the safety of construction operations. [0004] For the above problems, no effective solution ha...

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Problems solved by technology

[0003] However, deep geothermal reservoirs often have the characteristics of high temperature, high strength, and large stress. If the existing hydraulic fracturing method is directly used for fracturing, it is prone to problems such as high fracture initiation press

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