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

Anthropgenic GHG

• 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.

Source: NETL

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.

CH4 storage in coal

Porous Structure of Coal

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.

Cleat in Coal

Cleats in Coal

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.

Water

Coal

In-situ Reservoir

Primary Recovery

Gas Water

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).

Preferential Sorption affinity for CO2

Reservoir Pressure Psi

Gas

Con

tent

CO2

Methane

Methane/CO2 Exchange

ECBM/Sequestration in CoalECBM/Sequestration in Coal

ECBM & Sequestration Synergy

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.

CBM BLOCKS AWARDED

THANK YOU !!!!!