A device and method for drilling sealed coring while drilling in coal seams and soft rock formations

Abstract

The invention discloses a coal seam and soft rock formation drilling-while-drilling airtight coring device, which comprises a sampling outer cylinder. The two ends of the sampling outer cylinder are respectively provided with a sampling drill bit and a suspension joint; the lower end of the suspension joint extends into the sampling outer cylinder, and the suspension joint The tail of the bearing set is provided with a bearing group, and the upper part of the bearing group is provided with a pressing ball seat, and the connecting sleeve, the sampling inner cylinder and the long section of the sampling inner cylinder are arranged coaxially below the pressing ball seat; the connecting sleeve and the sampling inner cylinder are also connected outside The coaxial sleeve has a pushing cylinder; the connecting sleeve is equipped with a desorption valve; the sampling inner cylinder is equipped with a sealing ball valve; the high-pressure fluid entering the inner cavity passes through the first-level water outlet hole set on the ball seat body and then pushes the multi-stage hydraulic pushing mechanism Axially move to open the sampling drill bit, or push the multi-stage hydraulic pushing mechanism to move axially to close the sealing ball valve and the desorption valve through the secondary water outlet hole provided on the ball seat body. The device and the method of the invention realize the purpose of taking coal cores while drilling and quickly sealing the coal cores in situ at the bottom of the hole.

Description

technical field [0001] The invention belongs to the technical field of geological exploration and coal mine safety, and relates to a closed coring device and method for drilling holes in coal seams and soft rock layers while drilling. Background technique [0002] Gas content is an important parameter to characterize the gas-bearing characteristics of coal and rock formations. The gas content of coal seams is usually directly measured by desorption method. capacity. The desorption gas volume and residual gas volume can be obtained by actual measurement of the desorption instrument, and the gas loss volume can be obtained by calculating the initial desorption law of the coal core. The longer the exposure time of the coal core, the more inaccurate the estimation of the gas loss volume. In actual operation, the gas content data of coal formations can be obtained by coring. In order to ensure the accuracy and authenticity of the data, it is essential to carry out airtight corin...

AI Technical Summary

Problems solved by technology

The desorption gas volume and residual gas volume can be obtained by actual measurement of the desorption instrument, and the gas loss volume can be obtained by calculating the initial desorption law of the coal core. The longer the coal core exposure time, the more inaccurate the estimation of the gas loss volume

In actual operation, the gas content data of coal formations can be obtained by coring. In order to ensure the accuracy and authenticity of the data, it is essential to carry out airtight coring in the horizontal section. When taking the coring point, it is necessary to withdraw all the drill pipes in the hole, and then install the coring device, and then send the coring device to the hole to start coring drilling. The disadvantage is that the construction process is complicated and the construction labor intensity is increased. , and this process often takes a long time, especially in long boreholes. During this period, the coal core to be taken at the bottom of the hole is exposed to air or unpressurized water, and a large amount of gas from the coal core escapes. Therefore, freshly exposed coal cores cannot be obtained, and the gas content measurement results of the drilled samples are often quite different from the actual values, and the original gas information cannot be accurately obtained. Misjudgment, therefore, there is an urgent need for a device and method that does not replace the coring device during the drilling process and can perform sealed coring while drilling

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