Stanford Wave Physics SWP

1
Stanford Wave Physics (SWP)

• Importance of geological modeling of coalbeds for
  carbon dioxide sequestration
• by
• Tope Ifedayo Akinbehinje

2
Three major options for geological storage of
carbon dioxide

• Deep saline aquifer
• Depleted oil and gas reservoirs
• Coalbeds

3
Advantages of CO2 sequestration in coal
formations and depleted oil fields.

• Reduction of global warming
• Cost-effectiveness. Production of hydrocarbon can
  be used to offset the cost of CO2 sequestration
• Good public image for the coal industry and the
  petroleum industry
• Coalbeds have distinct advantage of being located
  close to coal plants locations

4
Why is there need for geological modeling of
coalbeds?

• Coal has properties different from conventional
  oil and gas reservoirs such as sandstone and
  limestone reservoirs. For example coal has
  dual-porosity system
• To determine if a particular coalbed is suitable
  for CO2 sequestration
• To make sure there is little or no leakage of
  stored CO2. Very high concentration of CO2 in
  water or air is poisonous
• To detect and monitor leakage of CO2 if any, at
  sequestration sites in time

5
Countries with great potential for CO2
sequestration in coals

• Country Total Coal reserve at end of 2005
  (MT) Share of World Total ()
• USA
  246,643 27.1
• Russian Fed.
  157,010 17.3
• China
  114,500 12.6
• India
  92,455 10.2
• Australia
  78,500 8.6
• South Africa
  48,750 5.4
• Ukraine
  34,153 3.8
• Kazakhstan
  31,279 3.4
• Poland
  14,000 1.5
• Brazil
  10,113
  1.1
• Total
  
  91
• MT Million Tons
• Source British Petroleum
• 
  

6
Countries with most coal reserves
7
Factors to be considered before storing CO2 in
Coalbeds

• Properties of the coal such as, matrix porosity,
  cleats (fractures), permeability and depth of
  occurrence
• Isolation of coal formation from surrounding
  strata by confining strata
• Types and properties of other geological
  formations surroundings coal formations.
• The seal capacity of a particular coal formation
• Water content of coal formation and any nearby
  aquifer/s
• Appreciable reservoir or formation pressure

8
Problems associated with storing CO2 in coalbeds

• Leakage of CO2 to the atmosphere and aquifers
• Primary and secondary porosity systems in coals
  have different CO2 storage mechanisms
• Limited long-term knowledge of the effects of
  artificially storing CO2 in coalbeds

9
Some effects of storing CO2 in coalbeds

• Increase in coal matrix volume
• Reduction in cleats (fractures) sizes
• Decrease in permeability of the coalbeds
• There may be increase in pressure

10
Modeling and Simulation of Coalbeds using GEM
(Features of GEM)

• Coal shrinkage and swelling
• CO2 injection for enhanced
• CBM recovery
• Dual Porosity
• Multiple gas components
• Different diffusion rates
• Stress dependent permeability and porosity
• Water saturation in cleats
• Temperature and pressure

11
Limitations of GEM modeling software

• It does not incorporate water in the coal matrix
• It does not allow movement of water between the
  coal matrix and the coal fractures
• It does not permit adsorption of gas in coal
  cleats.

12
Four modeling leakage cases
13
CASES 1 AND 2 Coal is overlain by sand in these
cases, the black lines represent gas migration
paths, and red line injection well.
14
CASES 3 AND 4 Coal is overlain by shale and sand
in these cases, the black lines represent gas
migration paths, and red line injection well.
15
CONCLUSIONS

• There is the need for proper characterization of
  coal formations before sequestering CO2 in them
• The properties of surrounding formations have
  influences on the suitability of coal formations
  for CO2 sequestration