Coal seam liquid carbon dioxide fracturing device and method

Abstract

The invention discloses a coal seam liquid carbon dioxide fracturing device and method. The device comprises a supplying unit for supplying liquid carbon dioxide, a fracturing pump, a hole packer, a first pipeline and a second pipeline; the hole packer is used for being placed in a drill hole in a coal seam to be fractured and comprises an grouting pipe, a first hole sealing capsule, a second hole sealing capsule and a fracturing pipe, one end of the grouting pipe and one end of the fracturing pipe penetrate through the first hole sealing capsule and are fixed on the first hole sealing capsule, the other end of the fracturing pipe penetrates through the second hole sealing capsule and is fixed on the second hole sealing capsule, and the other end of the grouting pipe is located between the first hole sealing capsule and the second hole sealing capsule. The coal seam liquid carbon dioxide fracturing device and method are capable of increasing the output of a mine and improving permeability of the coal seam and lump coal output rate.

Description

technical field [0001] The invention relates to the technical field of coal mining, and belongs to underground safe mining of coal mines, in particular to a coal seam liquid carbon dioxide fracturing device and method. Background technique [0002] my country's coal mines mainly adopt underground mining, the mining conditions are complex, the operating environment is harsh, and there are many disaster-causing factors, especially mechanized mining, gas drainage, and dust control of coal seams with low air permeability and hard gangue (nodules) are difficult to achieve results. The permeability of coal mainly depends on the porosity of the medium, the geometric properties of internal cracks, the fractal dimension of cracks, the internal stress-strain state and pore pressure, etc. These are considered to be the main factors affecting the permeability of coal, of which the first three The first is a direct factor, the stress-strain state and pore pressure affect permeability by ...

AI Technical Summary

Problems solved by technology

[0003] After years of research and practice, hydraulic fracturing and blasting fracturing technologies are effective ways to increase permeability or pre-moisture of coal seams. Although they can relieve pressure and increase permeability as a whole, and improve the air permeability and fragmentation rate of coal seams to a certain extent, their applicability is poor. The process is complex, the protection distance is insufficient, and the workload is large. More importantly, these measures have little effect on the pressure relief radius of the coal seam

It is specifically reflected in: the hydraulic fracturing technology uses a pressurized pump to inject the fracturing hydraulic pressure into the borehole to fracture the coal (rock) layer. Due to the limitation of the displacement of the pump and its technological characteristics, the pressure rise time is too long in this way. The loading speed is slow and the peak pressure is low, so only one crack perpendicular to the minimum principal stress direction can be formed. This crack is easy to expand along the original weak surface, and it is difficult to generate new cracks perpendicular to the layer, making it difficult for the cracks to communicate with each other, so it cannot be significantly increased. gas permeability of coal

Even if the high-pressure water can fracture the coal body, as the fracture volume increases, the pressure of the fracturing fluid will continue to decrease, and the effectiveness of fracturing will be lost rapidly

In addition, the proportion of fracturing proppant is also difficult to control, and the distribution is uneven. The hydrophilicity of coal will also affect the gas permeability of the coal seam. The fracturing equipment is complicated and the cost is high, so it is not suitable for increasing gas emissions.

Blasting fracturing technology is to put safety explosives or high-energy explosives in coal mines into drill holes, and use gun mud to block the blasting. This method has a short pressure rise time and high peak pressure, which can produce countless short cracks. Higher than the yield strength of the surrounding rock, resulting in severe fracture and collapse of the borehole wall, forming a "stress cage" in the residual pressure zone, thereby reducing the permeability

Other hydraulic extrusion measures include: hydraulic extrusion, a pressure relief zone located outside the stress concentration zone, suitable for soft coal, through loosening the coal body to relieve pressure and increase permeability, which cannot be explained by the principle of hydraulic fracturing; hydraulic slotting, through high pressure Water jet cuts seams in the coal body to relieve pressure and increase permeability; high-pressure water injection is similar to hydraulic fracturing, but the water injection pressure and water injection volume are limited, and large cracks cannot be opened or the cracks can be effectively extended and communicated

[0004] What has been published so far about liquid CO 2 Inventions on fracturing (CN 102011574 A, CN 102031106 A, CN 102168550 A, CN 102852508 A) are all aimed at oil exploitation or shale gas exploitation, and have been applied in some enterprises, but there is no information on coal mining Field applications and related processes

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