Free Online CO2 Plume Calculator: Injection Radius and Overpressure

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The plume radius comes from cylinder geometry: injected volume spread through the porous, partially saturated disc. The injection overpressure comes from steady radial Darcy flow and must stay below the fracture pressure of the caprock by your chosen margin, or the injection rate is not safe.

The two questions every injection permit asks

Once a site has capacity, two operational questions decide whether it works: how far will the CO2 spread, and how hard must you push to get it in? The tool above answers both with the standard screening physics. The plume radius comes from cylinder geometry, injected mass spread through the porous, partially saturated disc of reservoir. The injection overpressure comes from steady radial Darcy flow, and it is compared directly against your fracture pressure margin, because pressure is the thing that can break the seal that makes storage permanent.

Plan view of a CO2 plume growing in concentric circles around an injection well over one, five, and fifteen years, with notes on plume footprint and injection overpressure
The plume radius grows with the square root of injected mass; the pressure to inject it must respect the seal.

This is the second tool in the CO2 Storage and Geothermal Suite. It consumes the same reservoir properties as the capacity tool and adds permeability, the property that separates paper capacity from injectable capacity.

Reading the results

  • The footprint area is the monitoring obligation and the pore-space lease: seismic surveys and regulatory maps must cover it with room to spare.
  • The radius grows with the square root of mass, so doubling injection years does not double the footprint; the fifteenth year adds far less radius than the first.
  • The overpressure verdict is the safety line: exceeding the fracture margin means reducing rate, adding wells, or walking away.
  • The pressure halo extends far beyond the plume itself, which is why induced seismicity reviews look at a much larger circle than the CO2 footprint.

What this tool is for

First-pass feasibility of an injection rate, sizing the monitoring area for a storage concept, and making the capacity-versus-injectivity distinction concrete in teaching. Detailed permitting adds reservoir simulation, geomechanics, and well-test-calibrated permeability, with these screening numbers as the sanity check throughout.

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