Coal bed gas yield forecasting method

Abstract

The invention discloses a coal bed gas yield forecasting method which comprises the following steps: establishing a geological model for coal bed gas storage and migration; establishing a mathematical model of a coal bed gas reservoir in the geological model and obtaining the dynamic permeability of a coal bed according to the relative shrinkage of coal matrix desorption and the variation of coal matrix porosity in the mathematical model; solving the mathematical model by utilizing a numerical method to obtain a numerical model; solving the numerical model to obtain coal bed gas yield and reservoir pressure distribution. The coal bed gas yield forecasting method disclosed by the invention has the benefits that through comprehensive improvement in coal fissure compression factors and coal volume shrinkage factors, the accuracy of the forecasting method is improved; further, the influence of pulverized coal in a near well zone is considered, the pulverized coal in the near bore zone is converted into coal powder pollution skin, and the coal bed gas yield forecasting method is suitable for a coal bed gas well in which the pulverized coal is easy to go out, and geological conditions are not clearly understood.

Description

technical field [0001] The invention relates to the technical field of mining of coalbed methane, in particular to a method for predicting the output of coalbed methane. Background technique [0002] Coalbed methane is a self-generated and self-storage unconventional natural gas. Its development and utilization are of great significance to the improvement of energy structure, environmental protection and coal mine safety. Based on the existing coalbed methane mining technology, there have been many commercial or individual CBM numerical simulation software. [0003] Pulverized coal plugging and self-regulation effect are two factors that affect the permeability of coal seams. During the development of coalbed methane wells, especially in the early stage of development, the quality of coal is easy to produce pulverized coal, which blocks the gas production channels of coal seams near the wellbore, resulting in a decrease in permeability However, the existing CBM numerical si...

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Problems solved by technology

[0003] Pulverized coal plugging and self-regulation effect are two factors that affect the permeability of coal seams. During the development of coalbed methane wells, especially in the early stage of development, the quality of coal is easy to produce pulverized coal, which blocks the gas production channels of coal seams near the wellbore, resulting in a decrease in permeability However, the existing CBM numerical simulation software does not comprehensively consider these two influencing factors, and the permeability model adopted does not consider the influence of pulverized coal plugging on permeability, and lacks a comprehensive improvement on coal fracture compressibility coefficient and coal volume shrinkage coefficient

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