| 远距离下保护层开采卸压特性及钻井抽采消突研究 |
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| 引用本文： | 刘应科.远距离下保护层开采卸压特性及钻井抽采消突研究[J].煤炭学报,2012(6):1067-1068. |
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| 作者姓名： | 刘应科 |
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| 作者单位： | 中国矿业大学安全工程学院 |
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| 摘 要： | 我国西部部分矿区地质构造复杂,瓦斯灾害特别是煤与瓦斯突出十分严重,威胁了矿井的安全生产,制约了煤炭资源的开发。针对这些矿区构造复杂、煤层渗透性差及煤层群开采的特点,以消除煤与瓦斯突出危险性、降低煤层瓦斯含量为切入点,对远距离下保护层开采及钻井抽采卸压瓦斯、消除煤与瓦斯突出危险性进行了系统研究。构建了采场相似模型和数值分析模型,研究了远距离下保护层开采的卸压特性:①下保护层开采期间,被保护层可实现充分卸压,其透气性系数大幅度提高,为抽采卸压瓦斯提供了条件;②针对双保护层开采条件,揭示了工作面风巷、机巷内错40~50 m区域的被保护层均为膨胀区,是布置钻井的合理位置;③提出了远距离双保护层开采的重复卸压模型,首采保护层回采后形成的采空区具有"缓冲效应",减弱了次采保护层开采期间上覆煤层的卸压程度。建立了地面钻井稳定性分析的力学模型,研究得出:①邻近岩层的强度相差越大,对钻井的挤压、剪切作用越大;②在套管和井壁之间留设间距后,套管上的最大剪切应力平均降低50.8%,减小了套管剪切破坏的概率;③生产套管长度越大,其挠度值越大,抗弯曲变形能力越强。对此,设计了防剪切破断的钻井井身结构:生产套管采用贯穿井身的整管,与固井套管或井壁之间留设"缓冲容移间距",筛管段采用了"套管强化技术",有效提高了钻井稳定性。揭示了地面钻井抽采卸压瓦斯规律:①阐明了工作面回采距离(表征上覆煤层和裂隙带的透气性)是影响钻井产气率的关键参数;②得出了保护层工作面回采期间地面钻井产气率"快增慢减"的变化机制,并确定了钻井的最佳布井参数;③建立了卸压煤层及采空区的瓦斯流量计算模型,为钻井抽采卸压瓦斯消突效果的评价提供了依据;④提出了钻井下段增阻提高卸压瓦斯抽采量的方法。远距离下保护层开采及钻井抽采消突技术在神华集团乌兰煤矿进行了工程试验,结果表明地面钻井抽采卸压瓦斯消突效果显著:试验区钻井的总产气量为1 512.96×104m3,机巷侧、风巷侧钻井的最大布井间距分别为150和169 m,被保护层的残余瓦斯含量分别降低至3.63和3.14 m3/t,抽采率分别达到65.8%和68.0%,彻底消除了煤层的突出危险性。
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| 关 键 词： | 煤与瓦斯突出 下保护层 地面钻井 缓冲效应 井身结构 |
Study on the depressurization effect produced by exploitation of lower distant protective coal seam and elimination of outburst hazard of the protected seams by applying gas drainage with surface boreholes |
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| LIU Ying-ke.Study on the depressurization effect produced by exploitation of lower distant protective coal seam and elimination of outburst hazard of the protected seams by applying gas drainage with surface boreholes[J].Journal of China Coal Society,2012(6):1067-1068. |
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| Authors: | LIU Ying-ke |
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| Affiliation: | LIU Ying-ke(Faculty of Safety Engineering,China University of Mining and Technology,Xuzhou 221116,China) |
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| Abstract: | In Western China,there are some mining areas with complex geological structure and significant hazards of gas,coal and gas outburst.The outburst hazard not only threatens safety of mine gravely,but also makes it difficult to explore coal resources in some regions.Aiming at the characteristics of the complex structure,poor coal seam permeability and multi-seam mining in the mining area,with the purpose of eliminating the danger of outburst and decreasing the gas content of coal seam,this paper made a systematic research on the mining of the lower distant protective layer,the technology of pressure-relieved gas drainage using surface boreholes and eliminating the potential dangers of coal and gas outburst.By constructed the model of similar materials experiments of stope and numerical simulation,the author studied the depressurization effect of protected coal seam under the mining condition of lower distant protective layer: ① During extraction of the lower distant layer,the stress of protected layer could be reduced sufficiently,and gas permeability coefficient could be increased substantially,providing favorable condition for gas drainage;② As the double protective seam mining,40-50 m area of intake entry and return entry of mining face in protected coal seams is dilated area,which is the proper location of surface boreholes;③ Repeat depressurization mode is found that the gob of the extracted seam below the gassy one provides a "Buffering Effect" for the overlying coal seam which makes the depressurization of the overlying seam weaken.The results from mechanical model for analysis of the stability of surface borehole are: ① The greater the difference between the strength of adjacent strata is,the bigger the squeezing and shearing stress in the casing become;② Under the condition of leaving the space between the casing and borehole wall,the max shearing stress of casing decreased by 50.8% evenly,and the probability of failure of casing was reduced significantly;③ The longer the production casing is,the bigger the deflection value is and the greater anti-bending ability the casing gets.Based on the above results,the author designed a structure of surface borehole against shearing and rupturing.There leaves the "buffer spacing" between the cementing casing or borehole wall and the production casing which is whole-tube and screen section was handled by "casing enhancement technology",effectively improving the stability of surface borehole.The law of pressure relief methane drainage using surface borehole is demonstrated: ① Illustrated the distance from working face to borehole(showing the methane permeability coefficients of overlying coal seam and fractured zone),is the key influencing factor of gas production rate of borehole;② Revealed the changing mechanism of "fast increase-slowly decrease" of the gas production rate of borehole during the protective coal seam mining,and determined the best layout parameters of surface boreholes;③ Built a mathematical model for determining the gas flow rate of overlying coal seam and gob,which can provide a basis of assessment for gas drainage of overlying coal seam;④ Proposed the method of improving gas drainage form overlying pressure released seams with increasing the lower borehole resistance.The research results mentioned above were carried out in Wulan Coal Mine of Shenhua Group,which show that the effect of eliminating outburst by extracting pressure relieved gas with surface boreholes is remarkable.The pure gas drainage quantity of boreholes in the testing area has totally reached 1 512.96×10 4 m 3.The max spacing of borehole near the intake entry and the return entry are 150 m and 169 m respectively.The remaining gas quantities of the protected coal seams are eliminated to 3.63 m 3 / t and 3.14 m 3 / t,and the gas drainage rates are 65.8% and 68.0%,respectively,completely eliminating the outburst danger of the coal. |
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| Keywords: | coal and gas outburst lower protective coal seam surface borehole buffering effect borehole structure |
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