Permeability evolution due to dissolution and precipitation of carbonates using reactive transport modeling in pore networks

Juan P. Nogues, Jeffrey P. Fitts, Michael A. Celia, Catherine A. Peters

Research output: Contribution to journalArticlepeer-review

137 Scopus citations

Abstract

A reactive transport model was developed to simulate reaction of carbonates within a pore network for the high-pressure CO2-acidified conditions relevant to geological carbon sequestration. The pore network was based on a synthetic oolithic dolostone. Simulation results produced insights that can inform continuum-scale models regarding reaction-induced changes in permeability and porosity. As expected, permeability increased extensively with dissolution caused by high concentrations of carbonic acid, but neither pH nor calcite saturation state alone was a good predictor of the effects, as may sometimes be the case. Complex temporal evolutions of interstitial brine chemistry and network structure led to the counterintuitive finding that a far-from-equilibrium solution produced less permeability change than a nearer-to-equilibrium solution at the same pH. This was explained by the pH buffering that increased carbonate ion concentration and inhibited further reaction. Simulations of different flow conditions produced a nonunique set of permeability-porosity relationships. Diffusive-dominated systems caused dissolution to be localized near the inlet, leading to substantial porosity change but relatively small permeability change. For the same extent of porosity change caused from advective transport, the domain changed uniformly, leading to a large permeability change. Regarding precipitation, permeability changes happen much slower compared to dissolution-induced changes and small amounts of precipitation, even if located only near the inlet, can lead to large changes in permeability. Exponent values for a power law that relates changes in permeability and porosity ranged from 2 to 10, but a value of 6 held constant when conditions led to uniform changes throughout the domain. Key Points Acid dissolves carbonates but neither pH nor saturation alone predicts extent Dissolution increases porosity but permeability increase depends on flow rate Permeability decreases due to precipitation but effects are localized

Original languageEnglish (US)
Pages (from-to)6006-6021
Number of pages16
JournalWater Resources Research
Volume49
Issue number9
DOIs
StatePublished - Sep 2013

All Science Journal Classification (ASJC) codes

  • Water Science and Technology

Keywords

  • carbon sequestration
  • carbonate
  • permeability
  • pore network model
  • porosity
  • power law

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