Reciprocating type sampling method and device for gas content fixed-point sampling

Abstract

The invention relates to a reciprocating type sampling method for gas content fixed-point sampling. The method comprises the following steps: 1) performing segmental drilling on a hollow drill rod ofwhich the front end is fixed with a coal core pipe according to a predetermined drilling path; 2) arranging a sealing air bag connected with an inflation pipeline at a front end opening of the coal core pipe when the hollow drill rod is drilled to sampling predetermined depth, pushing the coal core pipe into the front end of the hollow drill rod along an inner hole of the hollow drill rod and fixing the coal core pipe, drilling the hollow drill rod again to sampling length to ensure that a coal sample enters into the coal core pipe, inflating the air bag arranged at the front end of the coal core pipe by utilizing the inflation pipeline, and then sealing the front end of the coal core pipe after the air bag is expanded; 3) taking out the sealed coal core pipe along the inner hole of the hollow drill rod, deflating the air bag and taking the coal sample out of the coal core pipe, and carrying out fixed-point sampling. According to the reciprocating type sampling method and device, the gas content fixed-point sampling efficiency and precision of a coal layer can be greatly improved, and the gas content testing accuracy is improved.

Description

technical field [0001] The invention specifically relates to a reciprocating sampling method and device for fixed-point sampling of gas content, belonging to the technical field of geological drilling. Background technique [0002] At present, the method of directly measuring coal seam gas content underground mainly adopts the desorption method, and the specific process is divided into three steps: 1. Drilling and collecting coal samples in newly exposed coal walls, stone gates or rock roadways; Determination of residual gas content. Among them, the theory of steps 2 and 3 is mature, and the impact on the measured value of gas content can be ignored. Since 1 involves the fixed-point sampling method and the calculation of gas loss, it is the main source of error in gas content measurement. The determination of gas content in underground coal mines must adopt the coal core tube coring method and the fixed-point sampling method based on the orifice sampling method. The bigge...

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Problems solved by technology

This method can really achieve fixed-point sampling, but there are the following problems: the sampling time is much longer than the stipulation that the sampling time should not be greater than 5 minutes; The temperature rise of the sample will cause deterioration and accelerate the gas desorption of the coal sample; during the time period between the completion of the drilling construction and the delivery of the coal core pipe to the bottom of the hole, the gas in the target coal sample section at the bottom of the hole has begun to escape, and the gas at this time The gas loss of the coal sample is not taken into account in the gas loss of the coal sample; the stability of the drilling in the soft coal seam is poor, and it is easy to deviate from the predetermined drilling path when re-drilling after the drill is withdrawn, which leads to the application of the coal core pipe sampling method in the soft coal seam Poor sex

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