Geochemistry Department Core Capability:
High Temperature/Pressure Experimental Geochemistry

Recently, the ESD has begun to develop geochemical experimental capabilities at temperatures and pressures beyond the ambient conditions characteristic of environmental geochemistry. Our current experimental geochemistry capabilities now span from the bench-scale to the nanoscale. Topics being investigated include: rock-water-gas interactions that control the behavior and fate of CO₂ injected into deep sedimentary basins, oil fields, and elsewhere within the shallow crust; geochemical interactions occurring within geothermal systems and the geochemical impact of various strategies employed in Enhanced Geothermal Energy recovery approaches; and fundamental research into mineral-aqueous fluid interfacial geochemical processes.

Our bench-scale studies utilize hydrothermal geochemical reactors of various types that permit experiments at temperatures up to 400°C and pressures up to 200MPa. We have four rocking furnaces equipped with flexible gold bag (Dickson-type) reaction cells and super-alloy pressure vessels, associated digital controllers, an analogue/digital datalogging system, a piston accumulator (for reinjecting fluid into the gold bags during a run), two air-driven (Sprague) high pressure pumps, two ISCO 500D HPLC pumps (one dedicated to CO₂ delivery using a chiller jacket), and a Quizex computer-controlled precision high pressure two-piston metering pump.  Fluid samples can be acquired throughout an experiment without disturbing the temperature and pressure of experiment.

Our nanoscale studies use a custom-built (homemade, one of a kind) Hydrothermal Atomic Force Microscope (HAFM) capable of real-time subnanometer (crystal monolayer) scale imaging of crystal growth and dissolution at up to 150°C and 10 b pressure under flowing conditions (gas or liquid), including aqueous fluids spanning a range in pH (pH1 – pH10) and fluid composition. A Picostage X-Y translator allows precise sample positioning over a ±1mm range.  A modified (for cooling) Digital Instruments Top View^© optical head also permits simultaneous video microscopy - ideal for crystal growth/dissolution catalysis/inhibition mechanistic studies.  Recently, we have built a minibending jig for use inside the HAFM, permitting simultaneous geomechanical/geochemical studies, e.g., subcritical crack growth, frictional force measurements.

We work closely with the Geochemical Transport group and use a variety of geochemical simulators to both design and interpret experiments.

Current research is funded by the DOE: Office of Basic Energy Science, Office of Fossil Energy, and the Geothermal Program Office. We are a participant in the LBNL EFRC Center for Nanoscale Control of Geologic CO₂.