Earth Sciences Division (ESD) Department of Energy (DOE) Lawrence Berkeley National Laboratory (LBNL)

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09/25/2013

Modeling Pore-Scale Geological Carbon Sequestration

Source:  Carl Steefel

Fig1_porescale
Figure 1: Top: Digitally reconstructed calcite grain pack from 3D synchrotron X-ray microtomography at the Advanced Light Source, Lawrence Berkeley National Laboratory. Bottom: pH contours in a diffusion-dominated numerical experiment involving the infiltration of high CO2 water into the same calcite grain pack. The simulation was carried out on the NERSC supercomputer Edison and consisted of about 1.6 billion grid cells with 1 micron spatial resolution.

ESD scientists Sergi Molins Rafa, Carl Steefel, Jonathan Ajo-Franklin, and Li Yang are collaborating with Computational Research Division scientist David Trebotich on the problem of subsurface geological carbon sequestration, using a new generation of pore-scale flow and reactive transport models possessing unprecedented spatial resolution and process fidelity.  These new models for the mesoscale physical and chemical processes associated with subsurface CO2 injection and sequestration are made possible by the convergence of world-class characterization and computational resources at the LBNL’s Advanced Light Source (ALS) and National Energy Research Scientific Computing (NERSC) facilities, respectively.

A first-of its-kind simulation of pore-scale reactive transport processes associated with CO2 injection and sequestration uses a centimeter-long capillary tube filled with crushed calcite (calcium carbonate) as an experimental and computational analogue of a flow path through the subsurface. The investigation begins with high resolution (1 micron) synchrotron X-ray microtomography collected at Beamline 8.3.2 at the Advanced Light Source to provide the pore geometry of calcite grains within the capillary tube. These data are converted into digital information that are then used as the initial conditions for the pore-scale simulations, which solve the Navier-Stokes equation with resolution equal or close to the resolution of the microtomography (1 micron) together with the multicomponent reactive transport equations for the chemical system. In the laboratory and virtual experiment, the capillary tube is infiltrated by a high CO2 solution, which reacts with the calcite as it flows through the tube, dissolving it and raising the solution pH and releasing calcium into solution. 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 withCO2  injection and sequestration  (Figure 1). These represent the largest and most highly resolved pore-scale reactive transport simulations ever carried out [1].  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.

This research was carried out as part of the DOE Energy Frontier Research Center (EFRC) for Nanoscale Control of Geologic CO2. Important additional support came in the form of SciDAC-e ARRA funding that builds on years of algorithm and software development at LBNL within the SciDAC (ASCR) program in DOE. The Center is headed by Associate Lab Director Don DePaolo and is a collaborative effort led by Lawrence Berkeley National Laboratory that includes three other national laboratories and four universities. The extreme computing results shown here have been recently highlighted by NERSC [2] and have been included in the FY15 DOE ASCR budget narrative submitted for Congressional approval [3].

To read more, go to:

  1. Steefel, C.I., Molins, S., and Trebotich, D. (2013) Pore scale processes associated with subsurface CO2 injection and sequestration.  Reviews in Mineralogy and Geochemistry 77.
  2. NERSC 2012 Annual Review.  “New Model Will Help Predict Stability of CO2 Reservoirs.” Science at scale highlight. to appear. http://www.nersc.gov/news-publications/publications-reports/nersc-annual-reports/
  3. FY15 Budget Request to Congress, “Massively-Parallel Simulations Verify Carbon Dioxide Sequestration Experiments”, to appear, http://science.energy.gov/ascr/about/ascr-budget/

Funding Source: BES, EFRC-NCGC