Ground and underground three-dimensional extraction system of coal seam gas

Abstract

The invention relates to an extraction system of a coal seam gas, comprising a coal mine underground clustered directional drilling group, a vertical well, an underground main extraction pipeline, an underground subhorizontal directional drilling orifice connecting pipeline, an underground water discharge box, a well head and a well head coal seam gas extraction pipeline, wherein the vertical well is arranged in an area near a directional drilling final hole and within a range of a ground clustered directional drilling track projection area, penetrates through a rock stratum, a rock stratum, a coal seam roof and a target coal seam and extends into a coal seam floor; the well head of the vertical well is provided with a ground extraction pipeline of the coal seam gas; the underground water discharge box is arranged in a coal mine underground roadway and connected with the coal mine underground clustered directional drilling group through the underground subhorizontal directional drilling orifice connecting pipeline penetrating through the target coal seam; and the upper end of the underground water discharge box is connected with the underground main extraction pipeline of the coal seam gas through a pipeline to form the three-dimensional extraction system. The invention has mature technology, little construction risk and difficulty and lower cost.

Description

technical field [0001] The invention relates to a coal bed gas extraction system. Background technique [0002] At present, the extraction of coalbed methane at home and abroad can be realized through surface drilling and underground near-horizontal drilling in coal mines. [0003] Surface drilling CBM extraction can generally be divided into vertical well extraction and directional well extraction. Shaft drainage mainly drills through one or more coal seams through the ground shaft borehole, and forms a large number of cracks in the coal seam by fracturing the coal seam section of the wellbore to increase the range of communication between the shaft and the reservoir, thereby improving the coal seam drilling efficiency. Finally, the coalbed methane in the reservoir is extracted through the wellhead extraction device. The advantage of this method is that the construction method is simple and the construction cost is low. At the same time, there are still some deficiencies...

AI Technical Summary

Problems solved by technology

The characteristics of horizontal wells are: drilling into the rock formation in the form of a vertical shaft first, and directional deflection when the wellbore trajectory reaches the predetermined depth to ensure that the wellbore reaches a near-horizontal state after entering the coal seam, and then drills into the coal seam to the designed well depth, and finally pumps through the wellhead The coalbed methane extraction device has the advantages of this drilling borehole structure in the coalbed methane extraction: the borehole and the coal seam have a wide contact range, good connectivity, and the gas extraction effect is better than that of the vertical well; the disadvantages are: the drilling fluid The impact of coal seam porosity is not conducive to the extraction of coalbed methane; the water accumulation in the well cannot be solved during the extraction process; the construction technical difficulty, cost and risk are greater than those of vertical wells

However, this kind of drilling also has the disadvantages of low production capacity, short drainage period, and is not conducive to large-scale drainage; this kind of drilling is mostly drilled with circulating sewage, and the cuttings in the sewage will block the coal seam cracks, which is not conducive to Release of coalbed methane; since the drainage system is completely arranged underground, blockage or leakage of pipelines will also pose a threat to mine safety; at the same time, this method cannot realize the separation of borehole drainage and gas production, which affects the extraction effect of coalbed methane

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