A kind of open-hole chemical cavitation method of coalbed methane well

Abstract

A method for chemically making a cave of an open hole of a gas well of a coal seam includes steps of selecting a coal reservoir with the vitrinite reflectivity lower than 0.6%; forming a channel for reaching the coal seam in a drilling operation mode; preparing aqueous alkali on the ground, pumping the aqueous alkali to a coal seam section along the channel and soaking the coal seam section in the aqueous alkali for a period of time; discharging collapsed slack coal to the ground in a well flushing operation mode; carrying out soaking and well flushing operation repeatedly, computing the collapse diameter of the coal seam according to the weight of the discharged slack coal until the cave with the designed size is formed in the collapsed coal seam section, and organizing follow-up production; and inspecting a chemical cave making application effect by comparing the method to the traditional method for making a cave of an open hole. The method has the advantages that once the coal reservoir with the vitrinite reflectivity lower than 0.6% is reacted with the aqueous alkali, large quantities of organic matters can be extracted, the mechanical strength of coal is sharply reduced, the slack coal is formed, the cave is formed in a collapsed coal wall, and the method for chemically making the cave of the open hole has important significance in aspects of increasing the size of the cave, eliminating pollution zones near the well and reducing construction cost for making the cave of the open hole.

Description

technical field [0001] The invention belongs to the fields of coalbed gas development and coal mine gas control, and in particular relates to a method for chemically creating holes in the open hole of a coalbed gas well. Background technique [0002] Open-hole cave completion in coalbed methane development was born half a century ago, but its potential advantages were not really recognized until Amcoco used this method to complete the Cahn1 well in 1977. Coalbed methane development has been carried out in the Guoguodi Formation coal seam in the northern San Juan Basin, and good results have been achieved. The output of open-hole cave completion is 3 to 20 times that of traditional hydraulic fracturing wells. [0003] Open-hole caves are mainly suitable for conditions with high gas saturation in coal seams, normal pressure to abnormally high reservoir pressure, and high permeability, and the coal body structure is relatively complete, close to the original structure coal. Th...

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Problems solved by technology

[0006] In order to solve the disadvantages of high construction cost and small plugging removal range in the prior art, the present invention provides an open-hole chemical method for coalbed methane wells that uses chemical methods to reduce the mechanical strength of coal bodies and realize open-hole hole creation and completion. Hole making method