Program > Keynote Speakers > Carl I. Steefel

Incorporating Microscale Chemical and Mechanical Effects into Reactive Transport Modeling of Subsurface Faults
Carl I. Steefel
Lawrence Berkeley National Laboratory

Dr. Carl I. Steefel is a Senior Scientist and Head of the Geochemistry Department at Lawrence Berkeley National Laboratory.  He has over 30 years of experience in developing models for multicomponent reactive transport in porous media and applying them to topics in reactive contaminant transport and water-rock interaction. He developed the first routine for multicomponent nucleation and crystal growth in the Earth Sciences and the first multicomponent, multi-dimensional code for simulating water-rock interaction in non-isothermal environments. He has also worked extensively in applying reactive transport modeling to natural systems, including hydrothermal, contaminant, and chemical weathering environments. More recent work has focused on pore scale studies of reactive systems, especially faults, and modeling of Critical Zone processes in terrestrial environments.

He is the principal developer of the reactive transport software CrunchFlow, a widely used package in many countries around the globe and a 2017 R&D100 award winner. Features that distinguish CrunchFlow from other RTM software include its global implicit solve of reaction and transport, the ability to treat diffusion with the Nernst-Planck equation, the ability to consider an explicit electrical double layer, mineral nucleation, burial and erosion, and porosity-permeability change as a result of reactions. CrunchFlow’s user-friendly input and flexible coupling of processes makes it easy to consider problems ranging from relatively simple geochemistry or transport to more complex simulations in which a range of processes are coupled together.


While reactive transport modeling of subsurface faults has been underway since at least the 1990s, the challenge of capturing microscale chemical and mechanical features and processes is only now being addressed.  The permeability of most subsurface faults is controlled by micro-scale asperities that can evolve due to the influx of reactive fluids, or as a result of stress-induced reactions that promote collapse of the fractures.  Chemical effects may involve channeling or wormholing within the fracture, leading to a focusing of flow via the positive feedback between flow and reaction, or to clogging of the fracture due to mineral precipitation.  Mineral precipitation may also potentially lead to fracturing of the rock if the driving free energy force of reaction is sufficiently high.  Where this occurs or not depends on the interplay between the free energy of reaction and the ambient stress field in the rock.  Simulation of both wormholing and mineral precipitation-induced fracturing require accurate models for the mineral-fluid interface, or for mineral-mineral interfaces separated by thin water films.  Here simulation of the reactive interfaces requires high resolution models for the interfaces at the nanoscale, including the electrical double layer bordering the charged mineral surfaces.