Behaviors and Influencing Factors of Desorption-Diffusion of Methane from Coal Core Under Drilling Fluid Medium
YANG Zhao-biao
QIN Yong
WANG Zhao-feng
WU Cai-fang
WANG Guo-ling
Abstract：Accurate calculation of the lost gas quantity under drilling fluid is a key to estimate coalbed methane (CBM) content. Based on an auto-simulating experiment of the CBM desorp-tion during pick-up of coal core under drilling fluid medium, we discussed systemically the effects of CBM pressure, core-hoisting velocity, coal granularity and drilling fluid density on desorption-diffusion behavior. The results show that the CBM pressure is a main inherent fac-tor deciding the lost gas quantity. The higher the pressure is, the larger the gas desorption ve-locity and the lost gas quantity are. The core-hoisting velocity is an extrinsic influencing fac-tor, but less influencing factor to the tectonically-deformed coal. The rapider the core-hoisting velocity is, the larger the lost gas quantity is. The natural granularity of coal is one of the in-fluencing factors, the smaller the granularity is, the more the lost gas quantity is. Increasing drilling fluid density can decrease the lost of the gas in coal core to a certain extent. The statis-tical relation between the lost gas quantity and CBM pressure was proposed by fitting to the simulating experimental data. The desorption-diffusion of CBM from coal core is a dynamic e-quilibrium preocess for CBM pressure and drilling fluid pressure.
Keywords：drilling fluidcoal coreCBMlost gas quantitydesorption-diffusioninfluencing factor
Publication Date：2009-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：5( 624-628 )