Download - Coal bed methane
What is coal bed methane?
• Standard natural gas: CH4
• Methane forms along with coal
• It is held in the cleats with the coal
• Substantial water pressure needed to keep methane in the coal: 400 to 1000 ft ?
Ref.www.Coalbed_methane.htm
" Decaying Organic matter is: – Buried – Cooked – Pressurized
" Creating – Coal – Methane – Other gases
The (Simplified) Science of CBM
Ref.www.Coalbed_methane.htm
Methane Storage in Coal
Methane in coal is:
• Adsorbed on the surfaces of the coal
• Stored as free gas in the cleats and open pores
Ref:-www.wsgs.uwyo.edu/Coal/CBM_Info.aspx
PARAMETERS IN CBM EXPLORATION
• Regional geology of the area • Mapping and surveying• Areal extent of coal seams• Thickness of the coal seams• Permeability in the Coal as measured by tests, logs, etc.• Gas content data
INITIAL STAGES OF CBM EXPLORATION
Stacking of location Planning strategy for cbm - geo technical order. - preparation of master log.
BORE HOLE DRILLING
• Low Clay Polymer Mud system
• Surface casing only• Continuous coring of
formation• Plotting of litho columns.• Correlation of litho columns
on the basis of borehole data.
• Sub-surface information are revealed and interpretations are done. Ref:- Raniganj bore hole drilling (photograph)
CONVENTIONAL VERTICAL DRILLING
• Mud circulation for the -stability of bore hole and -removal of cuttings. • Mud used:- - bentonite suspension and -PHPA (Partially hydrolyzed
polyacrylic amide) • Casing – 2 Casing Policy (12¼” - 9⅝”, 8 ½”-
5 ½”)• Cementation - Two stage
cementation or light weight cementation- due to large column of cement & low fracture gradient of Coals.
• Casing perforations
Ref:-www.coal bed gas drilling information.htm
Pressure drawdown profile of a single well
Water Flow Only
DiscontinuousGas Flow
ContinuousGas Flow
For CBM reservoirs, we need to deplete the reservoir pressure down low to get the gas out.
Source : ONGC Task Force Report 2006
SL.NO. COUNTRY COAL RESOURCES CBM RESOURCES( BILLION TONNES) (TCM)
1 RUSSIA 6500 17-1142 CHINA 4000 31.83 USA 3970 124 AUSTRALIA 1700 10.85 CANADA 7000 10.26 INDIA 241 1.07 S. AFRICA 150 3.28 U.K. 190 2.89 POLAND 160 2.8
10 GERMANY 320 2.811 ZIMBABWE 8 0.05
WORLD WIDE CBM RESOURCES
USES OF COAL BED METHANE
• Clean burning fuel for domestic and industrial uses.
• Motor fuel • Cleaning of recovered substances and methane
supply to natural gas pipelines • Electricity generation (diesel generators, gas
turbines, internal-combustion engines ) • Supporting mine operations • Community needs (heat and electricity) of
adjacent territories • Mine boilers – switching from coal to gas