Geological Carbon Sequestration

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					Geological Carbon Sequestration
 Presentation based on articles by
 S. Julio Friedmann
 ELEMENTS , VOL. 3, PP. 179–184 JUNE 2007
 And Steven Bryant
 Journal of Petroleum Technology • SEPTEMBER 2007
 IPCC Special Report on Carbon Dioxide Capture and Storage
 --Storage in Deep Underground Geological Formations –
      Carbon Capture and Storage
Geological storage is a four-step process:
• First, a pure or nearly pure stream of CO2 is
  captured from flue gas or other process
• Next it is compressed to about 100
• It is then transported by pipeline to the
  injection site
• Finally, it is injected deep underground into
  a geological formation where it can be
  safely stored for thousands of years or
Reservoir characteristics
• “The most promising reservoirs are porous
  and permeable rock bodies, generally at
  depths of 800 m or greater”

Pressure and temperature changes
 with depth
• On average, temperature increases by 25ºC
  for every 1000 m depth within the earth
  (average geothermal gradient)
• Pressure increases by approximately 270
  bars for every 1000 m depth (using density of
                             Fig. 1 of the Friedmann article

What is going to be the state of CO2
(solid, liquid or gas) At a depth of 800 m?
Under these conditions, CO2 will
 Act like a liquid, with
 • a density less than that of brine,
 • a fairly low solubility in water, and
 • a viscosity less than that of oil

 “The high densities are critical to
   successful storage because a large
   volume of CO2 can be injected into a
   limited pore volume.”
Storage Options
    (will also require an impermeable layer as “caprock”)

•    Deep saline formations
•    Depleted oil and gas reservoirs
•    Enhanced oil and gas recovery
•    Deep unmineable coal seams
•    Enhanced coal bed methane recovery


 Capacity of Storage Formations
Reservoir        Lower Estimate of             Upper Estimate of
Type             Storage Capacity              Storage Capacity
                     (GtCO2)                     (GtCO2)

Oil and gas                675                           900
Unminable                 3–15                           200
coal seams

Deep saline               1000                   Uncertain, but
formations                                        possibly 104

From Bradshaw and Dance 2005
Potential risks
• Fractured rock formations, faults, and seismic
  activity could provide an avenue for CO2 leakage.
• Pressure from CO2 injection could trigger small
• The cement caps usually placed on the wells
  could deteriorate when exposed to carbonic acid,
  which can form when CO2 interacts with saline
• Abandoned oil and gas wells that were not
  sealed to today’s standards could leak.

 Potential risks contd.
• A sudden and large release of CO2 could pose
  immediate dangers to people in the vicinity.
(This one by the way, has been shown to be
  groundless. See figure 3 of Friedmann article)
• Elevated CO2 concentrations in the shallow
  subsurface could have lethal effects on plants
  and subsoil animals, and could contaminate
• Carbon-laden liquids could mobilize toxic metals
  and organics and contaminate groundwater.

Potential release pathways and remediation


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