To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the pa...To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the paper conducted the numerical simulation of pre-drainage gas in drillings along coal seam, studied the relationship of adsorption constants and permeability, gas pressure, and effective drainage radius of coal seams, and applied the approach to the layout of pre-drainage gas drillings in coal seams. The results show that the permeability of coal seams is on the gradual increase with time, which is divided into three sections according to the increase rate: the drainage time 0–30 d is the sharp increase section;30–220 d is the gradual increase section; and the time above 200 d is the stable section. The permeability of coal seams is in negative linear and positive exponent relation with volume adsorption constant VLand pressure adsorption constant PL, respectively. The effective drainage radius is in negative linear relation with VLand in positive exponent relation with PL. Compared with the former design scheme, the engineering quantity of drilling could be reduced by 25%.展开更多
In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal ...In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal mining industry. How- ever, during the engineering applications, it is observed that the efficiency of gas drainage initially improves, but reduces there- after. Thus, it is speculated that the contrasts in coalbed methane drainage efficiency may reflect variation of the closure be- havior of the artificial fracture created. Based on comprehensive gas drainage monitoring data in underground coal mines, the work presented herein uses numerical simulation to show the behavior of the time-dependent closure of coal seam fractures as- sociated with various levels of waterjet fracturing parameters and geomechanical conditions.展开更多
基金Financial support for this work,provided by the National Natural Science Foundation of China(Nos.51327007,51104118 and51204134)Shaanxi Province Youth Science and Technology Star Project of China(2014KJXX69)
文摘To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the paper conducted the numerical simulation of pre-drainage gas in drillings along coal seam, studied the relationship of adsorption constants and permeability, gas pressure, and effective drainage radius of coal seams, and applied the approach to the layout of pre-drainage gas drillings in coal seams. The results show that the permeability of coal seams is on the gradual increase with time, which is divided into three sections according to the increase rate: the drainage time 0–30 d is the sharp increase section;30–220 d is the gradual increase section; and the time above 200 d is the stable section. The permeability of coal seams is in negative linear and positive exponent relation with volume adsorption constant VLand pressure adsorption constant PL, respectively. The effective drainage radius is in negative linear relation with VLand in positive exponent relation with PL. Compared with the former design scheme, the engineering quantity of drilling could be reduced by 25%.
文摘In order to improve efficiency of coal seam gas drainage, many fracturing techniques, such as waterjet fracturing, hydraulic fracturing and explosive fracturing, etc, have been developed and widely used in China coal mining industry. How- ever, during the engineering applications, it is observed that the efficiency of gas drainage initially improves, but reduces there- after. Thus, it is speculated that the contrasts in coalbed methane drainage efficiency may reflect variation of the closure be- havior of the artificial fracture created. Based on comprehensive gas drainage monitoring data in underground coal mines, the work presented herein uses numerical simulation to show the behavior of the time-dependent closure of coal seam fractures as- sociated with various levels of waterjet fracturing parameters and geomechanical conditions.
