Collaborative Research: Development and fabrication of a high-temperature borehole fluid sampler to characterize seawater-basalt reactions and the thermal limits of life on Earth

五十年的科学海洋钻探已经在海洋中创造了超过113个套管的钻孔。已在一系列海底地质环境中钻了这种遗留的钻孔，其中许多钻孔的深度足以使天然地温梯度使钻孔升温到一定温度范围(60-200摄氏度)。在这个温度范围内，海水和玄武岩之间的反应路径会发生变化，例如，通过原生矿物的溶解和不同矿物作为矿脉的沉淀，影响玄武岩地壳的老化。这种溶解和降水的结合改变了洋壳的特征，最终影响到地壳被俯冲的方式，并有可能发生大的破坏性地震。根据实验(122摄氏度)、理论计算(150摄氏度)和坊间证据(180摄氏度)，这个温度范围也跨越了微生物生命的热极限。然而，科学钻探界目前缺乏收集如此温暖、原始的井下流体的能力，因为电子设备在这样的温度下失效。该项目将通过首先测试形状记忆合金来解决这一抽样问题，形状记忆合金是一种金属合金，可以在特定温度下改变其形状和长度，这是合金成分和制造工艺的函数。然后，将开发一种利用形状记忆合金的特性来触发井筒流体收集的水样系统。新制造的系统将于2019年7月首次部署，届时科学钻探计划将重新进入井底约200摄氏度的遗留钻孔。该项目的更广泛影响将为科学界提供一种新的采样系统，用于在高温下收集井下流体。这样的采样系统不仅限于海洋钻孔，还可以在现有的数千个大陆钻孔中使用。这一新的高温流体采样系统将使社区在了解热液过程方面探索新的方向。热液作用和生命的热极限是令人兴奋的话题，吸引了公众。更具体地说，拟议的工作将包括为为期一周的夏令营(ssrovcamp.org)开发一个动手模块，供3-5年级和6-9年级学生以及参与圣克拉拉大学本科生海洋教育计划的学生使用。2018年，超过300名学生参与了这两个项目之一。该项目的关键是设计和制造一种适用于海洋和大陆环境下60-200摄氏度高温钻孔应用的流体采样系统。该项目将以一项临时专利为基础，设计和制造由一种新机制触发的标准钛注射器状液体捕获系统。这种机制将使用形状记忆合金，因为这种合金在特定温度下会改变形状。采样系统的设计将是模块化的，允许一次下井采集一套样品，每个采样器根据采样器中使用的特定形状记忆合金在特定温度下采集流体。该系统将设计为可在海洋钻井船、大陆钻井平台和潜水器/遥控潜水器(ROV)上部署。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Five decades of scientific ocean drilling have created more than 113-cased boreholes in the ocean. Such legacy boreholes have been drilled into a range of seafloor geologic settings and many of these boreholes are deep enough that natural geothermal gradients have warmed the boreholes to temperatures in the range (60-200 degrees C). Within this temperature range reactions pathways between seawater and basalt change, affecting how the basaltic crust ages through the dissolution of primary minerals and the precipitation of different minerals as veins, for example. This combination of dissolution and precipitation changes the characteristics of the ocean crust that ultimately affects how the crust is subducted and the potential for large destructive earthquakes. This temperature range also spans the thermal limits of microbial life, based on experiments (122 degrees C), theoretical calculations (150 degrees C), and anecdotal evidence (180 degrees C). However the scientific drilling community currently lacks the ability to collect such warm pristine borehole fluids because electronics fail at such temperatures. This project will solve this sampling problem by first testing shape memory alloys, which are metal alloys that can change their shape and length at a specific temperature that is a function of the alloy composition and fabrication process. Then a water sampling system will be developed that utilizes the properties of shape memory alloys to trigger the collection of boreholes fluids. The first deployment of the newly fabricated system will occur in July 2019 when the scientific drilling program re-enters a legacy borehole that is ~200 degrees C at the base of the hole. The broader impacts of this project will provide the scientific community with a new sampling system for collecting borehole fluids at elevated temperatures. Such a sampling system is not limited to oceanic boreholes, but could be used within the thousands of existing continental boreholes. This new high temperature fluid sampling system will allow the community to explore new directions in understanding hydrothermal processes. Hydrothermal processes and the thermal limits of life are exciting topics that engage the public. More specifically the proposed work will include the development of a hands-on module for a week-long summer day camp (ssrovcamp.org) for rising 3-5th and 6-9th grade students and students involved in the undergraduate marine education program at Santa Clara University. Combined, over 300 students were engaged in one of these two programs in 2018.The crux of this project is to design and fabricate a fluid sampling system for high temperature 60-200 degrees C borehole applications in oceanic and continental settings. The project will build on a Provisional Patent to design and fabricate standard titanium syringe-like fluid capture systems that are triggered by a novel mechanism. This mechanism will use shape memory alloys, given that such alloys change shape at a particular temperature. The sampling system will be modular in design to allow a suite of samples to be collected on a single lowering, each sampler collecting fluid at a specific temperature depending on the particular shape memory alloy that is used in that sampler. This system will be designed to be deployable from oceanic drilling vessels, continental drilling rigs, and submersibles/remotely operated vehicles (ROVs).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.