Active fracturing device for coal rock softening and coal rock fracturing construction process

Abstract

The invention discloses an active fracturing device for coal rock softening and a coal rock fracturing construction process. The active fracturing device comprises a conveying mechanism and a fracturing mechanism communicated with the conveying mechanism, wherein the conveying mechanism comprises a pipeline and a supply unit, a power unit and an adjusting unit sequentially arranged on the pipeline, and the fracturing mechanism is arranged at the output end of the pipeline. The construction process comprises the steps of fracturing fluid preparation and drilling, pre-compression, hole sealing, fracturing and pressure relief. The active fracturing device is simple in structure and reasonable in design, a dustproof water fracturing fluid or supercritical CO2 active fracturing fluid serves as a fracturing fluid for a coal rock to be fractured, the input cost is low, a fracturing effect is good, fracturing energy can be continuously increased through gas-fluid two-phase circulating conversion of the fracturing fluid, a good fracturing effect is achieved, clay mineral expansion in the coal rock is effectively prevented, the damage of the fracturing fluid to a stratum is decreased, further the permeability of the coal rock to be fractured is further improved, and the construction process is easy to control.

Description

technical field [0001] The invention belongs to the technical field of mine engineering, and in particular relates to a coal rock softening active fracturing device and a coal rock fracturing construction technology. 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 of coal rocks with high stress, low air permeability, and hard gangue (nodules), gas drainage, impact disasters and Coal dust prevention and control are difficult to achieve results. The permeability of coal and rock 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 and rock, among which the first three As direct factors, the st...

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Problems solved by technology

[0003] Hydraulic fracturing and blasting fracturing technologies are effective ways to increase permeability of coal rocks. 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, they have poor applicability, complicated processes, and heavy workload. What is important is that these measures cannot solve the hydrophobicity of low-permeability coal rocks, and cannot enhance the permeability and softening properties of low-permeability coal rocks

Specifically reflected in: hydraulic fracturing technology uses a pressurized pump to inject fracturing hydraulic pressure into the drill hole to fracturing coal rocks. Due to the limitation of the displacement of the pump and its technological characteristics, the pressure rise time is too long and the loading speed is slow. , the peak pressure is low, so only one crack perpendicular to the direction of the minimum principal stress 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. Therefore, the coal rock cannot be significantly increased. air permeability

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 nights is also difficult to control, and the distribution is not uniform. The hydrophilicity of coal rocks will also affect the gas permeability of coal rocks. 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 coal and rock to relieve pressure and increase permeability, which cannot be explained by the principle of hydraulic fracturing; hydraulic slits, through high pressure Water jet cuts cracks in coal and rock 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 penetrated

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