The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly ...The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly to the inaccuracy of CBM quantity in coal seam.Here we took the desorption of CBM from coal core under drilling fluid medium as a pressure-swing process,and based on the Langmuir equation and Fick-first law,established the desorption-diffusion model and numerical modeling method of lost gas(including free CBM) calculation in coal core under various drilling fluid mediums through physical simulation test and by considering comprehensively primary factors.The results showed that the physical simulated t-Qt curves can be rightly fitted by the numerical modeling data,which indicated the ultimate desorption quantity from the numerical modeling was adjacent to that from the physical simulation as a whole.It was found that the lost CBM quantity from the modeling method was generally higher than that from the direct method when lost time was relatively long.Thus,we sug-gest that it is necessary to emend the active China national standard through further investigation,since the lost CBM quantity from coal drilling-core was generally underestimated using the method in the current standard.展开更多
Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane(CBM)exploration as a significant basic parameter.Due to the calculation error of lost gas and resid...Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane(CBM)exploration as a significant basic parameter.Due to the calculation error of lost gas and residual gas in the direct method,the efficiency and accuracy of the current methods are not inadequate to the large area multi-point measurement of coal seam gas content.This paper firstly deduces a simplified theoretical dynamic model for calculating lost gas based on gas dynamic diffusion theory.Secondly,the effects of various factors on gas dynamic diffusion from coal particle are experimentally studied.And sampling procedure of representative coal particle is improved.Thirdly,a new estimation method of residual gas content based on excess adsorption and competitive adsorption theory is proposed.The results showed that the maximum error of calculating the losing gas content by using the new simplified model is only 4%.Considering the influence of particle size on gas diffusion law,the particle size of the collected coal sample is below 0.25 mm,which improves the measurement speed and reflects the safety representativeness of the sample.The determination time of gas content reduced from 36 to 3 h/piece.Moreover,the absolute error is 0.15–0.50 m^3/t,and the relative error is within 5%.A new engineering method for determining the coal seam gas content is developed according to the above research.展开更多
为研究气流对扩散层输水性的影响,构建二维模型表征扩散层纤维结构特征;联合VOF(Volume of Fluid)方法、N-S方程、Darcy定律及毛细压力方程,建立多孔介质内气液控制方程,跟踪气液流动界面,分析气流压力、温度和输入模式与不同孔隙率扩...为研究气流对扩散层输水性的影响,构建二维模型表征扩散层纤维结构特征;联合VOF(Volume of Fluid)方法、N-S方程、Darcy定律及毛细压力方程,建立多孔介质内气液控制方程,跟踪气液流动界面,分析气流压力、温度和输入模式与不同孔隙率扩散层水输运状态的关系,阐明气流与孔隙结构耦合作用对扩散层水分布的影响机理。结果表明:扩散层内气流分布直接影响水的输运,而气流状态与扩散层孔隙结构特征密切相关;增大气体输入间隔对于增进扩散层排水效果显著。该研究对于提升扩散层的输水性具有借鉴意义。展开更多
基金supported by the Key Project of National Natural Science Foundation of China (Grant No.40730422)Young Project of National Natural Science Foundation of China (Grant No.40802032)
文摘The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly to the inaccuracy of CBM quantity in coal seam.Here we took the desorption of CBM from coal core under drilling fluid medium as a pressure-swing process,and based on the Langmuir equation and Fick-first law,established the desorption-diffusion model and numerical modeling method of lost gas(including free CBM) calculation in coal core under various drilling fluid mediums through physical simulation test and by considering comprehensively primary factors.The results showed that the physical simulated t-Qt curves can be rightly fitted by the numerical modeling data,which indicated the ultimate desorption quantity from the numerical modeling was adjacent to that from the physical simulation as a whole.It was found that the lost CBM quantity from the modeling method was generally higher than that from the direct method when lost time was relatively long.Thus,we sug-gest that it is necessary to emend the active China national standard through further investigation,since the lost CBM quantity from coal drilling-core was generally underestimated using the method in the current standard.
基金the National Natural Science Foundation of China(51774119,51374095,and 51604092)the primary research projects of critical scientific research in Henan Colleges and Universities(19zx003)+1 种基金Program for Innovative Research Team in University of Ministry of Education of China(IRT_16R22)State Key Laboratory Cultivation Base for Gas Geology and Gas Control(Henan Polytechnic University)(WS2018A02)。
文摘Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane(CBM)exploration as a significant basic parameter.Due to the calculation error of lost gas and residual gas in the direct method,the efficiency and accuracy of the current methods are not inadequate to the large area multi-point measurement of coal seam gas content.This paper firstly deduces a simplified theoretical dynamic model for calculating lost gas based on gas dynamic diffusion theory.Secondly,the effects of various factors on gas dynamic diffusion from coal particle are experimentally studied.And sampling procedure of representative coal particle is improved.Thirdly,a new estimation method of residual gas content based on excess adsorption and competitive adsorption theory is proposed.The results showed that the maximum error of calculating the losing gas content by using the new simplified model is only 4%.Considering the influence of particle size on gas diffusion law,the particle size of the collected coal sample is below 0.25 mm,which improves the measurement speed and reflects the safety representativeness of the sample.The determination time of gas content reduced from 36 to 3 h/piece.Moreover,the absolute error is 0.15–0.50 m^3/t,and the relative error is within 5%.A new engineering method for determining the coal seam gas content is developed according to the above research.
文摘为研究气流对扩散层输水性的影响,构建二维模型表征扩散层纤维结构特征;联合VOF(Volume of Fluid)方法、N-S方程、Darcy定律及毛细压力方程,建立多孔介质内气液控制方程,跟踪气液流动界面,分析气流压力、温度和输入模式与不同孔隙率扩散层水输运状态的关系,阐明气流与孔隙结构耦合作用对扩散层水分布的影响机理。结果表明:扩散层内气流分布直接影响水的输运,而气流状态与扩散层孔隙结构特征密切相关;增大气体输入间隔对于增进扩散层排水效果显著。该研究对于提升扩散层的输水性具有借鉴意义。
