Firn permeability impacts on pressure loss associated with rapid air movement drilling
Firn permeability impacts on pressure loss associated with rapid air movement drilling
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DOI：
10.1016/j.coldregions.2015.11.018
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发表时间：
2016-03
影响因子：
4.1
通讯作者：
A. Whelsky;M. Albert
中科院分区：
文献类型：
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作者：
A. Whelsky;M. Albert
格陵兰岛和南极洲的极地冰盖是天气和气候的敏感指标，也是过去气候的自然档案;冰内和冰下的证据对科学调查很重要。各种钻冰技术已被用于广泛的科学应用，包括机械取冰芯、热水钻取出入孔和压缩空气钻孔以容纳用于地震测量的炸药。利用压缩空气在冰层中钻取通道孔，在冰盖的某些地方穿透速度很快，但在其他地方较浅的深度，该技术却失败了。本文研究了与压缩空气钻孔相关的压力损失与被称为“积雪”的老化雪的性质的相互作用。具体而言，我们报告的数值研究检查的影响，积雪分层和积雪渗透性空气钻引起的压力变化的钻孔内和周围的积雪。结果表明，在具有高透气性层带的积雪中，钻孔压力损失最高。井眼压力的损失将导致通过井眼向上输送的碎冰空气减少，从而由于碎冰堵塞钻头而导致钻井性能下降，从而使钻井停止。数值计算结果表明，高渗透率层的存在下，靠近底部的钻孔可能会导致足够的压力损失，阻碍钻井。与其他类型的冰钻不同，在靠近地表的钻孔中套管是常见的，在钻孔的底部套管对于在深度处存在高渗透性层带的区域中的快速空气流动钻孔可能是必要的。
The polar ice sheets of Greenland and Antarctica are sensitive indicators of weather and climate, and also serve as natural archives of past climate; evidence from within and below the ice is important for scientific investigations. A variety of ice drilling techniques have been used for a wide array of scientific applications, including mechanical ice coring, hot water drilling of access holes, and compressed air-drilling of holes to contain explosive charges for seismic measurements. Creating access holes using compressed air-drilling in ice has rapid rates of penetration in some locations on an ice sheet, yet the technique has failed at shallower depths in other locations. This paper investigates the interaction of the properties of the aged snow, called ‘firn’, with pressure loss associated with compressed air-drilling. Specifically, we report on numerical studies examining the impact of firn layering and firn permeability on air-drill induced pressure changes inside the borehole and in the surrounding firn. Results indicate borehole pressure loss is highest in firn that has bands of higher air permeability layers. A loss of borehole pressure would lead to decreased ice-chip air transport up through the borehole, causing degraded drill performance as ice chips clog the drill bit, stalling the drill. Numerical results show that the presence of higher-permeability layers near the bottom of the borehole may lead to sufficient pressure loss to impede drilling. In contrast to other kinds of ice drilling, where casing the borehole near the surface is common, casing the bottom of the borehole may be necessary for rapid air movement drilling in areas where high permeability bands of layers exist at depth.