Method for determining drainage and mining intensity of coal-bed gas well

Abstract

The invention provides a method for determining drainage and mining intensity of a coal-bed gas well. The method comprises following steps: pre-setting first falling speed of a working fluid level during a single-phase flow phase; determining the estimated total time for drainage and mining based on the variation quantity from the initial pressure of a well bottom to the critical desorption pressure; obtaining a well-bottom predicated first pressure generated by a mineshaft liquid column based on the first falling speed of the working fluid level and the pre-estimated total time for drainage and mining; adjusting the first falling speed of the working fluid level based on the difference between the well-bottom predicated first pressure and the critical desorption pressure and ensuring the difference between well-bottom predicated first pressure and the critical desorption pressure satisfies the falling speed of the working fluid level within the error range; and determining the difference as the drainage and mining intensity in the single-phase flow phase. The method for determining drainage and mining intensity of the coal-bed gas well has following beneficial effects: while ensuring higher output, the method helps to avoid damage to the reservoir stratum; the best calculations of the drainage and mining intensity are achieved during the saturated single-phase water-flow phase, the non-saturated and single-phase water-flow phase and the gas-water two-phase flow phase for the coal-bed gas well.

Description

Technical field

[0001] The invention relates to the technical field of petroleum engineering, in particular to a method for determining the drainage intensity of a coalbed methane well. Background technique

[0002] With the continuous expansion of global energy demand and the depletion of conventional oil and gas resources, the large-scale development and utilization of unconventional resources is particularly urgent. As a typical unconventional resource, coalbed methane has huge global reserves, more than twice the proven reserves of conventional natural gas. Major coal-producing countries in the world attach great importance to the development of coalbed methane.

[0003] Coalbed methane mining usually uses drainage gas production methods, that is, the water in the reservoir is pumped to depressurize, and then the gas adsorbed on the surface of the coal seam is resolved and extracted. Coal reservoirs are highly sensitive to stress, and the porosity and permeability of the rese...

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