Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep...Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage, They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111（1） and 11112（1） in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m^3/min and the effective drainage distance can be extended up to 150 m or more.展开更多
Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and lo...Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and low recovery factors.In this study,combined core displacement and nuclear magnetic resonance(NMR)experiments explored the reservoir gas−water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection.Consequently,for fracture core,the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion,whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores.Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability,especially for fracture core.The remaining gas distribution and the content are related to the core properties.Compared with pore cores,the water invasion rate strongly influences the residual gas distribution in fracture core.The results enhance the understanding of the water invasion mechanism,gas injection to resume production and the remaining gas distribution,so as to improve the recovery factors of carbonate gas reservoirs.展开更多
基金Acknowledgments The research was supported by Program for Changjiang Scholars and Innovative Research Team in University （IRT_I4R55）, and the National Natural Science Foundation of China under Grant No. NSFC-51274193.
文摘Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage, They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111（1） and 11112（1） in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m^3/min and the effective drainage distance can be extended up to 150 m or more.
基金Project(2016ZX05017)supported by the China National Science and Technology Major Project
文摘Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and low recovery factors.In this study,combined core displacement and nuclear magnetic resonance(NMR)experiments explored the reservoir gas−water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection.Consequently,for fracture core,the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion,whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores.Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability,especially for fracture core.The remaining gas distribution and the content are related to the core properties.Compared with pore cores,the water invasion rate strongly influences the residual gas distribution in fracture core.The results enhance the understanding of the water invasion mechanism,gas injection to resume production and the remaining gas distribution,so as to improve the recovery factors of carbonate gas reservoirs.
