Draining and mining method for coal-bed gas well

Abstract

The invention discloses a draining and mining method for a coal-bed gas well, and belongs to the technical field of coal-bed gas development. A working liquid level quickly descends to 10-30 meters above the coal-bed gas analysis pressure according to an analysis pressure value of coal-bed gas. By the intelligent draining and mining method, the working liquid level is always controlled to 10-30 meters above the analysis pressure; if the working liquid level descends quickly, the draining and mining system is lowered; if the working liquid level rises again, the draining and mining system is raised; therefore gas is not analyzed, and a single-phase flowing state of liquid water with the maximum pressure difference on a coal bed is kept; when the water yield is obviously reduced, about 70 percent of water in the coal bed is drained at the moment, and a pressure drop funnel with a larger area is formed; the liquid level is controlled to 5-10 meters below the bottom boundary of the coal bed so as to ensure that the coal bed section is all exposed above the water in the coal bed; the gas and water two-phase flow, taking the coal-bed gas as a main body and the water as an auxiliary body, of the coal bed is kept, and the generated gas can bring away about 30 percent of the residual water in the coal bed; meanwhile, the flowing pressure at the bottom of the well is controlled by controlling the casing pressure at a wellhead, so that the aim of reasonably adjusting the gas yield is fulfilled.

Description

technical field [0001] The invention relates to a coal bed gas well drainage method, which belongs to the technical field of coal bed gas development. Background technique [0002] The drainage principles formed in the initial stage of coalbed methane development are: smooth, continuous, and slow, and the fluid level drops by 3-5 meters per day as required. Under normal drainage conditions, wells with a depth of about 600 meters need continuous drainage for about 4 months to reach the analysis period; according to this principle, if the well depth reaches 1200 meters or more, it will take about 8 months to reach the analysis period. Analysis, the analysis of the pre-production time is relatively long. Drainage of coalbed methane wells is a process of draining downwater. The more pressurized water in the coal seam is discharged, the larger the area of ​​the pressure drop funnel will be, and the corresponding gas production will be more. According to the principle of seepage...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a coalbed methane drainage method, which solves the problems of slow drainage and long analysis time, avoids the problems of low liquid production caused by two-phase flow in the coal seam, and small pressure drop funnel area, and improves the gas production.

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