Extended-range optical televiewer imaging of the NEEM deep ice borehole, Greenland

北格陵兰埃米安 (NEEM) 冰钻项目钻孔于 2010 年 8 月到达冰盖底部，触及地表以下 2438 米深度的冰床。因此，NEEM 岩心是有史以来钻探时间最长的岩心之一，人们希望它能够提供延续到最后一个（埃米安）间冰期的过去气候的高分辨率记录。通过查看移除岩心后留下的钻孔，可以提供与岩心和当地冰盖的物理构成相关的附加补充信息。 Robertson Geologging Ltd (RGL) 最近开发了一种先进的测井技术（光学电视；OPTV），用于采矿业。与之前的（定向）钻孔视频技术相比，OPTV 具有许多优势，因为它能够以非常高分辨率（每像素小于 1 毫米）提供整个钻孔壁（即，围绕钻孔及其全长 360 度）的几何精确图像。在过去的三年里，申请人与 RGL 合作，将该设备应用于冰中，并将其应用于冰川和冰盖上的多个测试地点。这些试点研究的结果彻底改变了可以从冰钻孔中恢复的信息，包括识别不同的冰类型、识别不同的层和结构生成、识别和表征钻孔壁内的气泡和碎片夹杂物，尤其是提供从钻孔中取出的岩心的定向虚拟图像（通过“滚动”和反转钻孔壁的图像）。尽管 OPTV 具有彻底改变冰钻研究的潜力，但由于探空仪本身的压力等级以及沿相对较轻（因此可运输）电缆的延长长度的信号通信相关的问题，该技术目前仅限于在 1000 m 以下的深度使用。前一问题现已解决，RGL 目前正处于解决信号处理挑战的后期阶段，并将于 2011 年底开发出扩展范围 OPTV 系统 (EOPTV)（请参阅支持信）。这项小额赠款申请旨在将这种新的 EOPTV 系统应用于 NEEM 深钻孔的全长（约 2.5 公里），以评估新系统的性能并解决几个具体的科学问题（在目标下列出）。

The North Greenland Eemian (NEEM) Ice Drilling Project borehole reached the base of the ice sheet in August 2010, hitting the bed at a depth of 2438 m beneath the surface. The NEEM core is therefore one of the longest ever drilled, and it is hoped that it will provide a high-resolution record of past climate extending through the last (Eemian) interglacial period. Additional complementary information relating to the core and the physical makeup of the local ice sheet can be provided by viewing the borehole that has been left following the removal of the core. An advanced technique for such logging (optical televiewing; OPTV) has recently been developed by Robertson Geologging Ltd (RGL) for use in the mining industry. OPTV has many advantages over previous (directional) borehole video technology in that it provides a geometrically accurate image of the entire borehole wall (i.e., 360 degrees around the borehole and along its full length) at a very high resolution (less than 1 mm per pixel). The applicant has, over the past three years, worked with RGL to adapt this equipment for use in ice and applied it to several test sites on glaciers and ice sheets. The results of these pilot studies have completely transformed the information that can be recovered from ice boreholes - including identifying different ice types, identifying different layers and structural generations, identifying and characterizing bubble and debris inclusions held within the borehole wall and, not least, providing orientated virtual images of the core removed from the borehole (by 'rolling' and inverting the image of the borehole wall). Despite the potential of OPTV to revolutionize ice drilling research, the technique is currently restricted to use at depths of less than 1000 m by issues relating to the pressure rating of the sonde itself and signal communications along an extended length of relatively lightweight (and therefore transportable) cable. The former issue has now been resolved, and RGL is currently in the late stages of solving the signal-processing challenges and will have an extended-range OPTV system (EOPTV) developed by the end of 2011 (see Letter of Support). This small-grant application is to apply this new EOPTV system to the full (~2.5 km) length of the NEEM deep borehole, both to evaluate the performance of the new system and to address several specific science questions (listed under Objectives).