A fracturing method for sub-stage circulation of low-pressure forward injection of low-temperature fluid in upward drilling

Abstract

The invention discloses an upward drilling negative pressure advancing type injection low-temperature fluid staged cycle fracturing method. First, water jet slotting equipment is used to set up three crack areas, and water is injected through a water injection pipe to fill up a hydraulic plugging device. In this way, three sealed fracturing chambers are formed, and the three sealed fracturing chambers are placed in a negative pressure state. Cryogenic fluid is injected into the three sealed fracturing chambers, and the cryogenic fluid fills each sealed fracturing chamber in turn, and the three sealed fracturing chambers are filled with low-temperature fluid. The fracture area in the fracturing chamber is subjected to cold impact fracturing. As the low-temperature fluid in the sealed fracturing chamber is heated and gasified by the geothermal heat, the internal pressure of the low-temperature fluid exhaust pipe exceeds the opening threshold of the safety pressure relief valve, and the safety pressure relief valve opens to make the corresponding The variable gas is discharged, thereby reducing the air pressure inside the low-temperature fluid exhaust pipe and each sealed fracturing chamber, so that 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 an upward drilling negative pressure advancing 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 coalbed methane resources, with great development potential, and the recoverable resources are about 10.87×10 12 m 3 , in the next 10 to 20 years, China's coalbed methane production will increase significantly, and it will play an increasingly important role in making up for the shortage of conventional oil and gas production. With the increase of mining depth, the content and pressure of CBM in the coal seam gradually increase, the permeability of the coal seam gradually decreases, and the gas disasters such as CBM explosion and coal and gas outburst are also becoming more and more serious. CBM extraction is essential. Through investigation, it is found that the current coalbed methane dr...

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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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