A new high-temperature borehole fluid sampler: the Multi-Temperature Fluid Sampler

Abstract

Deep (>1 km depth) scientific boreholes are unique assets that can be used to address a variety of microbiological, hydrologic, and biogeochemical hypotheses. Few of these deep boreholes exist in oceanic crust. One of them, Deep Sea Drilling Project Hole 504B, reaches ∼190 ∘C at its base. We designed, fabricated, and laboratory-tested the Multi-Temperature Fluid Sampler (MTFS), a non-gas-tight, titanium syringe-style fluid sampler for borehole applications that is tolerant of such high temperatures. Each of the 12 MTFS units collects a single 1 L sample at a predetermined temperature, which is defined by the trigger design and a shape memory alloy (SMA). SMAs have the innate ability to be deformed and only return to their initial shapes when their activation temperatures are reached, thereby triggering a sampler at a predetermined temperature. Three SMA-based trigger mechanisms, which do not rely on electronics, were tested. Triggers were released at temperatures spanning from 80 to 181 ∘C. The MTFS was set for deployment on International Ocean Discovery Program Expedition 385T, but hole conditions precluded its use. The sampler is ready for use in deep oceanic or continental scientific boreholes with minimal training for operational success.