Single thick coal seam ground mining well extraction process

Abstract

The invention belongs to the technical field of coal bed gas extraction and particularly relates to a single thick coal seam ground mining well extraction process which is capable of performing scale and high-benefit extraction on single coal seams in condition of high ground stress and low permeability. A tri-size drilling process is used, a local well cementation mode is used for relieving damage to bushings by stratum moving, and damage of ground extraction well process structure is prevented by adding a hanger. By extraction experiment well extraction effect analysis and technological and economic feasibility evaluation, the ground extraction well output effect and the cost in condition of single thick coal seam extraction are offset basically, and certain reference and guide effects are provided for future ground coal bed gas extraction well process design and construction of other mines.

Description

technical field [0001] The invention belongs to the technical field of coal bed gas exploitation, and in particular relates to a single thick coal seam ground mining well drainage process. Background technique [0002] For mining areas containing important recoverable coal seams and coalbed methane resources in the Carboniferous Permian, the main mining coal seams are high-rank anthracite, which has the characteristics of simple structure, high coal seam hardness, and high gas content. Affected by coal burial depth, coal thickness, technical difficulty, and mining economics, the No. 3 coal seam of the Permian Shanxi Formation (commonly known as the lower Permian coal formation) was mined preferentially. Due to the good geological and structural conditions, it did not cause a large amount of gas to escape during the formation of coal-derived gas (mainly methane gas), so the content of coalbed methane (coal mine gas) per ton of coal is high. According to safety production req...

AI Technical Summary

Problems solved by technology

[0004] However, for this kind of mining area, after adopting the conventional surface coalbed methane well completion technology, the surface negative pressure vacuum pump is used for extraction and the detection device is lowered into the well for testing. , the wellbore structure of CBM wells is easily damaged by coal mining rock movement. Since the horizontal displacement of the rock formation is the largest at the interface between the weathered zone and the bedrock, it will lead to complete destruction of the wellbore structure at this position. At the same time, through the ground negative pressure The negative pressure value of the vacuum pump reaches the limit value, which also reflects the effective communication without cracks after the wellbore structure is damaged.

Therefore, due to the impact of the fractured subsidence zone formed by the mining of the upper Permian coal formation, it is difficult to achieve a certain scale and high-efficiency development of coalbed methane under the conditions of high ground stress and low permeability by using the above-mentioned conventional mining methods, and it is impossible to effectively realize the development of coalbed methane. Gas drainage in goaf subsidence area during and after mining

[0005] At the same time, since the in-situ stress value of my country's coal mining areas is mainly concentrated in the range of 8~17MPa, the maximum can reach 22.7MPa (Dacheng area), using this conventional mining method, even in the basin, the mining volume is only an average of 3000 cubic meters per day per well The production rate is around 100000000000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000, but the ground stress value of the Black Warrior Basin in the United States is 1 ~ 6MPa, so under the same completion technology conditions, the recovery rate of my country's surface coalbed methane development is far lower than the average 6000 ~ 8000 m3 / day of the wells in the United States Yield

It can be seen that it is difficult to achieve a certain scale and high-efficiency development of coalbed methane under the conditions of high ground stress and low permeability by using conventional mining methods in my country.

Images