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

50年的科学海洋钻探已经在海洋中创造了超过113个套管井。这些遗留的钻孔已被钻到一系列海底地质环境中，并且这些钻孔中的许多钻孔足够深，使得天然地热梯度将钻孔加热到范围（60-200摄氏度）内的温度。在这个温度范围内，海水和玄武岩之间的反应途径发生变化，例如，通过原生矿物的溶解和不同矿物作为矿脉的沉淀，影响玄武岩地壳的年龄。这种溶解和沉淀的结合改变了海洋地壳的特征，最终影响了地壳的俯冲方式和发生大规模破坏性地震的可能性。根据实验（122摄氏度）、理论计算（150摄氏度）和轶事证据（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这种温暖的原始钻孔流体的能力，因为电子设备在这样的温度下会失效。该项目将通过首先测试形状记忆合金来解决这一取样问题，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过程的函数。然后将开发一种水取样系统，该系统利用形状记忆合金的特性来触发钻孔流体的收集。新制造的系统的首次部署将于2019年7月进行，届时科学钻探计划将重新进入孔底温度约为200摄氏度的传统钻孔。这一项目的广泛影响将为科学界提供一种新的采样系统，用于收集高温下的钻孔流体。这种取样系统不仅限于海洋钻井，也可用于数以千计的现有大陆钻井。这种新的高温流体取样系统将使该社区能够探索了解热液过程的新方向。水热过程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）开发一个实践模块，供3- 5年级和6- 9年级的学生以及圣克拉拉大学本科海洋教育项目的学生使用。2018年，共有300多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用于海洋和大陆环境中高温60-200摄氏度钻孔应用的流体采样系统。该项目将建立在一项临时专利的基础上，设计和制造由一种新机制触发的标准钛合金状流体捕获系统。该机构将使用形状记忆合金，假定这种合金在特定温度下改变形状。取样系统将采用模块化设计，允许在单次下降时收集一套样品，每个取样器根据取样器中使用的特定形状记忆合金在特定温度下收集流体。该系统将被设计为可从海洋钻井船、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知识价值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.