Coal mine underground low-temperature closed coal core drilling device and method

Abstract

The invention discloses an underground coal mine low-temperature closed coal core drilling device and method, and belongs to the technical field of coal core drilling.The underground coal mine low-temperature closed coal core drilling device comprises an outer cylinder assembly, an inner cylinder assembly is rotationally installed in the outer cylinder assembly, a collecting assembly is fixedly installed at one end of the inner cylinder assembly, and a water supply assembly is rotationally installed at one end of the inner cylinder assembly; a cold supply assembly is rotatably mounted at one end of the inner cylinder assembly, a drill bit assembly is fixedly mounted at one end of the outer cylinder assembly, a coal seam is cooled through a liquid nitrogen nozzle during use, after cooling, the coal seam is cut through the drill bit assembly, and a coal sample enters a collection chamber through a small-diameter drill bit; the upper end ball valve and the core cutting ball valve are pushed through the water supply assembly, then low-temperature sealing is carried out on a coal sample, the gas overflowing effect is reduced, field desorption is carried out, and accurate basic data can be conveniently obtained for coal mine gas content measurement, gas disaster control, coal bed gas resource exploration and development and the like.

Description

technical field [0001] The invention relates to coal mine sampling, in particular to an underground low-temperature airtight coal core drilling device and method in a coal mine, belonging to the technical field of coal core drilling. Background technique [0002] Coalbed methane (gas) content is an important parameter to characterize coal seams, and it is an important basis for surface coalbed methane (gas) resource exploration, production capacity prediction and well pattern layout design. It is an important basis for the study of occurrence law and coal seam outburst risk prediction, mine ventilation design and equipment selection, and gas drainage engineering design. The gas dissipation rate in coal is related to particle size and temperature. Small, the gas in the coal body will lose rapidly when the temperature is higher. At present, the gas content measurement usually adopts the method of drilling and returning chips at room temperature. The drill bit cuts the coal bod...

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Problems solved by technology

[0002] Coalbed methane (gas) content is an important parameter to characterize coal seams, and it is an important basis for surface coalbed methane (gas) resource exploration, production capacity prediction and well pattern layout design. It is an important basis for the study of occurrence law and coal seam outburst risk prediction, mine ventilation design and equipment selection, and gas drainage engineering design. The gas dissipation rate in coal is related to particle size and temperature. Small, the gas in the coal body will lose rapidly when the temperature is higher. At present, the gas content measurement usually adopts the method of drilling and returning chips at room temperature. The drill bit cuts the coal body into small particles at the sampling point. Or return to the orifice under the action of water pressure, the exposure time of the whole process is too long, and during the process of cutting and returning the coal sample in the hole, the original characteristics and integrity of the coal body will be destroyed by mechanical action. During the sampling process, friction with the coal body generates heat, resulting in an increase in the temperature in the borehole, which intensifies the gas release rate, resulting in a large amount of gas dissipation in the coal body during the sampling process, resulting in the measurement results of the coal gas content being inconsistent with the actual gas content of the coal body. There are huge deviations. Currently, there are mainly three fixed-point sampling devices and sampling methods for the direct determination of underground gas content in coal seams. When the borehole is deep, the negative pressure generated by the compressed air injection is low enough to take out coal samples; the second is to use a single-tube or double-tube core drilling tool, which can achieve fixed-point collection of short-hole coal samples within 60m, The disadvantage is that for long drilling, the drilling time is too long, the desorption gas loss of the coal sample is large, resulting in inaccurate gas content measurement results; the third is the use of a closed coring device, the disadvantage is that the device operation process is complicated and is greatly affected by the applicable conditions , cannot be used for coal sample collection in ultra-deep boreholes with thousand-meter drilling rigs

The above three fixed-point sampling methods are all carried out at room temperature, and the influence of high temperature in the hole on gas release cannot be avoided. Therefore, the study of low-temperature sealed sampling devices has important practical significance for the accurate determination of coal seam gas content.

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