co 2 sequestration in coal seams b. k. prusty ph. d. (usa) scientist central institute of mining and...
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CO2 Sequestration in Coal Seams
B. K. Prusty Ph. D. (USA)
Scientist
Central Institute of Mining and Fuel Research
Global Warming• Global temperature rose by 0.5 - 0.9°C in
the past century• Likely to increase by 1.1 to 6.4 °C
between 1990 and 2100• Rise of average atmospheric temperature
across the globe is termed as global warming
• Increased GHG concentration responsible
• Minority opinion: Part of Earth's natural cycle
Greenhouse Effect• Shorter-wavelength solar radiation
passes through Earth's atmosphere, and is absorbed by the surface of the Earth, causing it to warm
• Part of the absorbed energy is radiated back to the atmosphere as long wave infrared radiation
• The GHGs selectively transmit this infrared wave, trapping some and allowing some to pass through into space
• GHGs absorb these waves and reemits the waves downward, causing the lower atmosphere to warm
• Carbon dioxide, methane, nitrous oxide, and fluorocarbons
Greenhouse Effect
EARTH
SUN
ATMOSPHEREInfra-red radiation is emitted from the earth’s surface
Solar radiation passes through clear atmosphere
Most solar radiation is absorbed by the earth’s surface and warms
it
Some solar radiation is reflected by the earth to
the atmosphere
Some of the infra-red radiation is absorbed and re-emitted by the
greenhouse gases
GHG Increase
Gas Pre-industrial level (1750)
(vol)
Current (1998) amount
(vol)
Percentage increase
CO2 278 ppm 365 ppm 31
CH4 700 ppb 1745 ppb 150
NOx 270 ppb 314 ppb 16
• CO2 the most important GHG because of its abundance
• CO2 Emission from coal burning.• Energy sector contributing about ~
45% of total GHG emission (fossil fuel)
• >85% of the global energy produced from fossil fuel
• Continued reliance on fossil fuels forecast for future
GHG Emission from Coal
• Fossil fuel consumption to increase 40% in next 20 years
• CO2 emissions to rise by 33% during that period
• Continued use of low-cost, reliable fossil energy while reducing the CO2 emissions is a major challenge
• Control of CO2 emission and its stabilisation critical for abatement of global warming
CH4 Emission from Coal
• CH4 the 2nd most important GHG.
• Methane from coal mining, and handling.
• CO2 is emitted in larger quantity.
• Methane has 21 times greater effect.
• Globally 27 million tons of methane is emitted every year from coal mining.
• Methane recovery from coal and its utilisation is one the mitigation options.
GHG Abatement Strategy
• Kyoto Protocol agreed upon by more than160 countries (1997)
• Annex I countries to reduce emission by 5.2% of 1990 level (during 2008-12)
• India has no obligation due to Non-Annex status
• India can earn Carbon Credit by earning Certified Emission Reductions
CO2 Emission Reduction
• Efficient energy technology
• Renewable sources
• Carbon sequestration
Sequestration is the removal of CO2 from
anthropogenic sources/atmosphere and
disposing it for geologically significant time
periods such as to prevent its interference
in the global climate system.
Geological Sequestration
Potential Sinks Potential (Gt)*
Ocean 1,000 - 10,000+
Deep saline formations
100 -10,000
Depleted oil and gas reservoirs
100 - 1,000
Coal seams 10 -1,000
Terrestrial 10 - 100
Coal Seam Methane
• Huge gas (250 m3/t) produced during coalification.
• Methane, CO2,N2, Ethane and others.
• Gas stays in the micro-pores.
• Adsorbed state (90%).
• Small portion as free gas in the macropores.
• Very small quantity dissolved in the water.
Conventional vs. Coal Reservoir
• Low pressure reservoir. • Both source and reservoir rock.• Gas stays in adsorbed state (liquid
like density)• Larger vol. of gas per unit volume of
reservoir due to adsorbed state.• Low porosity and permeability. • Initial water production declines.• Gas production attains peak before
declining.
Gas RateWater Rate
Water Rate Gas Rate
a. Conventional
b. Coalbed
Conventional versus coalbed reservoirs
Coalbed Reservoir • Dual Porosity: fracture porosity and matrix
porosity.• Matrix porosity more significant for
methane retention potential of coals.• The primary mechanism of methane
retention in coal beds is adsorption on the coal surface within the matrix pore structure.
• Fracture porosity in coal is due primarily to the presence of cleats.
• Face cleat is the major cleat and may extend to a great distance.
• Butt cleat usually extends only from one face cleat to the next.
Transport of methane in Coal
Three Stage process
• Desorption from coal surface.
• Diffusion through micropores.
• Flow in macropores (permeability dependent).
CBM Recovery
• In-situ: Water and gas at high pressure
• Primary recovery method: pump out water, reduce pressure, CH4 desorb and flow to production well.
• Hydro-fracturing for improving permeability
• 20-60% of gas recovered by primary method.
Vertical wells – the standard technique for CBM
• 5 spot pattern• 8 wells per section on 80 acre spacing
Recovery by Vertical wells
ECBM/ Sequestration in Coal
• 20-60% recovery by Pressure depletion technique.
• Enhanced recovery by injection of a second gas.
• Coal’s preferential sorption of CO2 over methane (2:1 to 8:1).
• CO2 displace the adsorbed methane and gets physically adsorbed and stored securely.
• Injection of CO2 will increase drive pressure and the CBM recovery rate.
• CO2 injection can achieve about 70-90% recovery of gas-in-place
• CO2 sequestration in coal has potential to generate revenue through ECBM.
• CO2-ECBM has twin advantage (economic & environment).
CO2 Injection Pilot: Allison
• Located in the San Juan basin, in New Mexico, USA.
• Operated by Burlington Resources.• The pilot consists of four injection wells
and nine production wells, drilled on 320-acre spacing.
• Injection pressure: 1300-1600 psi (9-11 MPa). CO2 injection rate: 141.5 ×103 m3/day. Later, due to injectivity loss, it was reduced to 84.9 ×103 m3/day.
• In 6-years, 370,000 tons of CO2 injected. • Breakthrough of CO2 was minimal. After six
years of injection, CO2 content was 6%, slightly greater than pre-injection level of 4%.
• This suggests that sequestration is happening.
• Recovery improved from 77 to 95%.• Ratio of CO2/CH4 was ~ 2.9:1.• During injection reduction in injectivity of
~60% was observed.• Coal permeability near the well was reduced
by up to two orders-of-magnitude; effects became less severe further from the well, and affected the coal a maximum distance of about 1,000 feet (~300 m) from the well.
CBM Status in India
• Area opened for exploration: 13600 Sq Km
• Blocks awarded: 26
• Resources: 1374 BCM
• Production Potential: 38 MMSCMD
• Most prospective area: Jharia, Raniganj, Karanpura coalfields.