A method for fracturing with sub-stage circulation of negative pressure back-injection low-temperature fluid

Abstract

The invention discloses a negative pressure retreat type injecting low-temperature fluid staged circulation fracturing method. Firstly, three crack areas are prefabricated by using a perforating gun, and then the rubber plugging device is filled with water through a water pipe, thereby forming three sealing pressure zones. The three sealed fracturing chambers are placed in a negative pressure state through the air pump, and low-temperature fluid is injected into the three sealed fracturing chambers. The low-temperature fluid fills each sealed fracturing chamber in turn. The fracture area is subjected to cold impact fracturing, and as the low-temperature fluid in the sealed fracturing chamber is heated and gasified by the geothermal heat, after the internal pressure of the low-temperature fluid exhaust pipe exceeds the opening threshold of the safety pressure relief valve, the safety pressure relief valve opens to discharge the gas, thereby The air pressure inside the low-temperature fluid exhaust pipe and each sealed fracturing chamber is reduced, and the cycle is repeated, and the gas expansion force fracturing is performed on each sealed fracturing chamber multiple times. It can effectively ensure the rapid injection of low-temperature fluid and the cracking effect on coal and rock mass, and will not cause pollution to the surrounding environment.

Description

technical field [0001] The invention relates to a negative pressure retreat type injection low-temperature fluid staged cycle fracturing method, which belongs to the technical field of coal and rock mass anti-permeability. Background technique [0002] China is rich in unconventional natural gas resources and has great potential for development, among which the recoverable resources of coalbed methane are about 10.87×10 12 m 3 , the recoverable resources of shale gas are 15×10 12 ~25×10 12 m 3 , in the next 10-20 years, China's unconventional natural gas production will increase significantly, and it will play an increasingly important role in making up for the shortage of conventional oil and gas production. Although the reserves of unconventional natural gas resources in my country are large, the reservoirs are complex and dense, and the main part of the reservoir space is a nanoscale pore-throat system, with micron-millimeter-scale pores locally developed. Therefore,...

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Problems solved by technology

[0004] Through investigation, it is found that the existing low-temperature fluid injection technology is injection under pressure, and the maximum injection pressure can reach 20MPa, which will significantly inhibit the contact between the low-temperature fluid and the reservoir surface, thereby greatly weakening the temperature difference between the low-temperature fluid and the reservoir. thermal stress caused by

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