Cave-forming method for coal seam gas directional well

Abstract

The invention discloses a cave-forming method for a coal seam gas directional well and belongs to the field of coal seam gas mining. The cave-forming method comprises the steps that a cave-forming target point is determined in a coal seam or between an upper top plate and a lower bottom plate of the coal seam, and a discharge and mining well field of the coal seam gas directional well is determined in the position, located above the cave-forming target point, on the ground; drilling operation is conducted on the coal seam and the upper top plate and the lower bottom plate of the coal seam through a directional drilling technique, the cave-forming target point is drilled out to the preset well depth position, and thus the coal seam gas directional well is obtained; a casing is put downwardsin the coal seam gas directional well for well cementing operation, then, a casing forging-milling device drilling tool assembly is put into the position, corresponding to the cave-forming target point, in the casing, and the part, corresponding to the cave-forming target point, of the casing is forged and milled away; and a mechanical cave-forming drilling tool assembly is put into the casing till the mechanical cave-forming drilling tool assembly is placed at the cave-forming target point, and mechanical cave-forming operation is conducted in the cave-forming target point. Cave forming is conducted for directional wells such as the coal seam gas pinnate horizontal well and the coal seam gas U-shaped well, and the problems that the ground conditions for drilling a vertical well are not met, the adaptability of the vertical well is limited, and cave forming of the directional well is difficult are solved.

Description

technical field [0001] The invention relates to the field of coalbed methane exploitation, in particular to a method for creating cavitations in a directional well of coalbed methane. Background technique [0002] In the process of coalbed methane exploration, in order to cope with low coal seam permeability and low gas production, the above problems are usually solved by creating holes in the coal seam, or the rock formation at the bottom, or the roof at the top. Commonly used hole making methods are divided into mechanical hole making, hydraulic hole making, gas hole making, explosive hole making, etc. Among them, mechanical hole making generally adopts the method of mechanical hole expansion, and the mechanical hole making tool is placed in the predetermined hole making position Make the cutter bar open and rotate under the drive of the drilling tool to cut coal seams to form caves that meet actual needs. The process and equipment are simple, and the size of the cave can...

AI Technical Summary

Problems solved by technology

[0005] The methods provided by the prior art are only applicable to vertical coalbed methane wells, but cannot be applied to directional wells such as plume horizontal wells and U-shaped wells.

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