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首页> 外文期刊>Journal of natural gas science and engineering >A novel active prevention technology for borehole instability under the influence of mining activities
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A novel active prevention technology for borehole instability under the influence of mining activities

机译：采矿活动影响下井壁失稳的新型主动预防技术

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Coal bed methane (CBM) drainage is an efficient method used to control gas hazards. Nevertheless, borehole instability is prone to occur under repeated disturbances by external stress from mining activities. Consequently, the collapsed coal blocks the gas-flow channel to further induce several gas drainage problems, including low gas concentration and flow, poor drainage result, etc. Due to these problems, screen pipes were installed in this work to provide active support in order to prevent borehole instability. Initially, the effect of mining activities on borehole stability was analysed. Subsequently, we explored the instability characteristics and corresponding acoustic emission (AE) properties of a non-supported borehole and a borehole stabilized by internal active support. These boreholes were drilled in the lab sample instead of the real coal sample. Moreover, the abilities of the holes to resist disturbances due to external stresses were compared. When the stress reached 10 MPa, the non-supported borehole was completely destroyed, whereas the actively supported borehole only slightly deformed. As the stress continuously increased to 14 MPa, a deformation of 15 mm was detected along the radial direction of the actively supported borehole. Additionally, an analysis of the dynamic changes in the strain on the screen pipe surface, the AE time sequence parameter and location information indicated that the maximum AE event count and energy dissipation rate of the supported borehole at 14 MPa were 44% and 23% lower, respectively, than the corresponding values for the non-supported borehole at 10 MPa. Thus, the support increases the ability of the borehole to resist disturbance by at least 40%. Furthermore, the locating points and energy rate appeared to temporally cluster at coal-yielding or failure stage. Hence, the supporting effect of the screen pipe on the coal around boreholes at the crushing stage is significant. The internal support to the borehole provides a positive confining pressure for the coal in the fracture zone to improve the coal's residual strength. Depending on the support from the screen pipe, the coal can mesh to remain in place and thus prevent collapse, which improves the stability of the borehole. (C) 2015 Elsevier B.V. All rights reserved.
机译：煤层气（CBM）排放是用于控制瓦斯危害的有效方法。然而，由于开采活动的外部压力，在反复扰动下，很容易发生井眼失稳。因此，坍塌的煤堵塞了气流通道，进一步引发了一些瓦斯抽放问题，包括瓦斯浓度低和流量低，排水效果差等。由于这些问题，在此工程中安装了筛管以提供积极的支撑，以便防止井眼不稳定。最初，分析了采矿活动对井眼稳定性的影响。随后，我们探索了非支撑井眼和内部主动支撑稳定井眼的失稳特性和相应的声发射（AE）特性。这些钻孔是在实验室样本而非真实煤样本中钻出的。此外，比较了孔抵抗由外部应力引起的干扰的能力。当应力达到10 MPa时，无支撑的井眼被完全破坏，而有源支撑的井眼仅发生轻微变形。当应力连续增加到14 MPa时，沿着主动支撑钻孔的径向方向检测到15毫米的变形。此外，对筛管表面应变的动态变化，AE时间序列参数和位置信息进行的分析表明，在14 MPa时，所支撑钻孔的最大AE事件计数和能量耗散率分别降低了44％和23％分别比10 MPa下无支撑钻孔的相应值高。因此，支撑件将井眼抵抗干扰的能力提高了至少40％。此外，在采煤或破坏阶段，定位点和能量率似乎会暂时聚集。因此，在破碎阶段，筛管对钻孔周围煤的支撑作用是显着的。钻孔的内部支撑为裂缝区域中的煤提供了正的围压，从而提高了煤的残余强度。取决于筛管的支撑，煤可以筛分以保持在原位，从而防止塌陷，从而提高了井眼的稳定性。 （C）2015 Elsevier B.V.保留所有权利。

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