Method for calculating coal-bed gas absorption amount of gas well

Abstract

A method for calculating a coal-bed gas absorption amount of a gas well comprises the following steps: step one: testing and analyzing a coal bed that a gas well passes through, so as to acquiring a coal quality industrial analysis result, and collecting gas well coal bed data; step two: calculating a maximum reflectance of vitrinite according to a dry ash-free volatile; step three: calculating a coal-bed gas absorption amount of each coal bed according to a coal-bed gas dynamic absorption equation; and step four: calculating an absorption amount of each coal bed under different pressures according to a formation temperature of each coal bed, and summing all absorption amount values to obtain a total absorption amount when the gas well passes through all coal beds. The method is capable of greatly improving precision of calculation of coal-bed gas absorption amount of the gas well and has important practical significance for instructing coal-bed gas exploration and development.

Description

Technical field: [0001] The invention relates to the field of coalbed methane exploration and development, in particular to a method for calculating the adsorption amount of coalbed methane in a gas well. Background technique: [0002] The quantitative calculation method of gas well coalbed adsorption gas content is the key and main technical problem in the evaluation of coalbed methane reservoirs. Using logging data to calculate its content has become an important way, and its calculation accuracy directly affects the decision-making of coalbed methane exploration and development. The critical desorption pressure of the coal seam refers to the corresponding pressure when desorption and adsorption reach equilibrium, that is, the pressure at which the gas adsorbed on the coal micropore surface begins to desorb due to the pressure drop. Theoretically, when the reservoir pressure drops below the critical desorption pressure, the gas adsorbed in the coal pores begins to desorb, ...

AI Technical Summary

Problems solved by technology

However, most coalbed methane wells pass through multi-coalbed methane reservoirs or thicker coalbed methane reservoirs, and they often carry out mixed drainage in a unified manner. Each coal reservoir is regarded as a uniform gas-producing reservoir. It is obviously not in line with the actual situation. The above calculation model only considers the influence of pressure on the adsorption amount of coalbed methane, and does not consider the influence of temperature on the amount of adsorbed gas. The adsorption amount of coalbed methane has an influence, so there is a certain error in the calculation of the adsorption amount of coalbed methane by the above model

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