High Performance Computing Meets Mesoscale Science

Source:  Carl Steefel, Sergi Molins, and Dan Hawkes

The convergence of world-class microscopic characterization and computational resources has made it possible to address the problem of subsurface geological carbon sequestration and other closely related subsurface topics, using a new generation of pore-scale flow and reactive transport models. These models, developed as a collaborative effort involving Carl Steefel and Sergi Molins of LBNL-ESD, and David Trebotich of LBNL’s Computational Research Division (and others), possess unprecedented spatial resolution and process fidelity. They have made it possible to carry out a first-of its-kind simulation of pore-scale reactive transport processes associated with CO2 injection and sequestration using a centimeter-long capillary tube filled with crushed calcite (calcium carbonate) as an experimental and computational analogue of a flow path through the subsurface.  

As reported this past year in the journals Environmental Science & Technology and Computing in Science and Engineering, the ultra-high resolution simulations are able to capture the micron-scale hydrodynamic and diffusion boundary layers at interfaces between reactive calcite grains and the flowing solution, demonstrating that the model is a tool for investigating the mesocale science associated with CO2 injection and sequestration. These represent the largest and most highly resolved pore-scale reactive transport simulations ever carried out. Such pore-scale simulations, which contrast with larger-scale CO2 injection and sequestration simulations based on averaged physical and chemical parameters, offer the promise of finally resolving the long-discussed discrepancy between laboratory and field rates, by taking into account the detailed pore geometry of subsurface materials.

Imaging of the porous material was carried out using X-ray synchrotron microtomography at the Advanced Light Source at Lawrence Berkeley National Laboratory. These characterization data are then used as the basis for a high resolution numerical (digital) model of the reactive porous medium.  A pore-scale reactive transport model based on the CHOMBO-Crunch platform developed at Lawrence Berkeley National Laboratory is then used to carry out simulations with as many as 2.5 billion grid cells to resolve the centimeter-long porous domain in three dimensions on the NERSC supercomputers.

• To read the Environmental Science & Technology paper, go here: http://pubs.acs.org/doi/full/10.1021/es5013438
• To read the Computing in Science and Engineering paper, go here: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6970989
• To read more about this work, go to: http://earthsciences.typepad.com/blog/2015/05/steefel-a-key-developer-of-complex-flow-code.html

Citations:

• Molins, S., D. Trebotich, L. Yang, J.B. Ajo-Franklin, T.J.  Ligocki, C. Shen, and C.I. Steefel (2014), Pore-scale controls on calcite dissolution rates from flow-through laboratory and numerical experiments. Environmental Science & Technology, 48 (13), 7453–7460; DOI: 10.1021/es5013438.
• Trebotich, D.P., M.F. Adams, S. Molins, C.I. Steefel, and C. Shen (2014), High resolution simulation of pore scale reactive transport processes associated with carbon sequestration. Computing in Science and Engineering, 16 (6), 22–31; DOI:10.1109/MCSE.2014.77.

Funding: BES