Method for calculating gas-water permeability of coal-bed methane in different production stages

Abstract

The invention discloses a method for calculating gas-water permeability of coal-bed methane in different production stage. The method involves that according to different mining stages, the productionstage can be divided into the following four stages including a single-phase water flowing stage, a near-wellbore unsaturated single-phase flowing stage, a near-wellbore gas-water two-phase flowing stage and a single-phase gas flowing stage; and the permeability is calculated through combining a permeability-pressure empirical model according to restrictions of an effective stress effect, a coalmatrix shrinkage effect caused by gas desorption, a coal matrix shrinkage effect caused by hydrolysis desorption as well as a Klinkenberg effect on the permeability. According to the method, aiming atthe four production stages of a coal-bed gas well for the first time, a gas-water permeability calculation model which comprehensively considers the influence of "the four effects" in the coal-bed gas well drainage and recovery process is provided, and therefore the dynamic permeability of the coal-bed gas well can be predicted more accurately and quickly.

Description

technical field [0001] The application relates to the field of mining technology, in particular to a method for calculating gas-water permeability in different production stages of coalbed methane. Background technique [0002] Coalbed methane refers to hydrocarbon gas stored in coal seams with methane as the main component, mainly adsorbed on the surface of coal matrix particles, and partly free in coal pores or dissolved in coal seam water. It is an associated mineral resource of coal. Coal reservoir permeability is a key parameter affecting the production of coalbed methane. In the actual coalbed methane mining process, it is found that with the increase of gas output and effective stress of coal seam, the permeability of reservoir coal rock decreases. Changes are complex. During the drainage process of coalbed methane wells, the physical properties of coal reservoirs are affected by many factors and are in a dynamic change. Scholars at home and abroad have done a lot ...

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Problems solved by technology

However, previous studies have not comprehensively reported the key mechanism affecting the dynamic permeability of coal reservoirs, and have not carried out detailed and in-depth quantitative characterization of the above-mentioned relative permeability laws in each production stage of coalbed methane wells.

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