Coalification and Methanation: Coal Bed Methane
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This document discusses coalification and methanation processes. It defines coal as a sedimentary rock formed from vegetative material under increased temperature and pressure over long periods of time. Coal formation relies on environments that favor accumulation and preservation of plant matter, followed by peatification and chemical coalification as the peat is buried deeper. Coal rank describes the extent of change from peat to lignite, subbituminous coal, bituminous coal and anthracite as heat and pressure increase. Biogenic and thermogenic methane are generated during early and later stages of coalification, respectively.
![Environments of Coal formation
Fresh-water peat lands
Upper delta and alluvial plain swamps
Marshes
Aquatic environments [Fresh Water]](https://image.slidesharecdn.com/cbm-171112151951/85/Coalification-and-Methanation-Coal-Bed-Methane-3-320.jpg)
![Coal Formation
Coal formation relies on three factors:
(1) initiation, maintenance, and repetition of
environments that favor large-scale accumulation
and preservation of vegetal sediment;
(2) conditions within this depositional environment
that favor biological degradation and alteration of
the vegetal sediment to peat [peatification];
(3) geochemical processes that induce chemical
coalification of the peat to higher-rank coal.](https://image.slidesharecdn.com/cbm-171112151951/85/Coalification-and-Methanation-Coal-Bed-Methane-4-320.jpg)
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Coalification and Methanation: Coal Bed Methane
- 1. Coalification & Methanation Pritish Barman B.Tech Petroleum Engineering 2012-2016 DIBRUGARH UNIVERSITY INSTITUTE OF ENGINEERING AND TECHNOLOGY Department of Petroleum Engineering
- 2. What is Coal? Coal: A sedimentary rock that burns Mineralized vetegatative material deposited over a long period of time. Has altered chemical composition Formed by increased Temp. and Pressure Usually bears fissures containing water and adsorbed methane.
- 3. Environments of Coal formation Fresh-water peat lands Upper delta and alluvial plain swamps Marshes Aquatic environments [Fresh Water]
- 4. Coal Formation Coal formation relies on three factors: (1) initiation, maintenance, and repetition of environments that favor large-scale accumulation and preservation of vegetal sediment; (2) conditions within this depositional environment that favor biological degradation and alteration of the vegetal sediment to peat [peatification]; (3) geochemical processes that induce chemical coalification of the peat to higher-rank coal.
- 5. Coal Formation Sediment burial, subsidence of peat bogs Completely cuts off contact with atmospheric oxygen Overburden: compaction and subsidence Increase Pressure, Temperature
- 6. Coal Rank Coal is not homogeneous it needs classification. Describes extent of geologic change and metamorphism since deposition as peat. Low Rank High Rank parallels: Loss of recognizable plant remains (macerals) Dull shiny luster Increasing hardness Increasing Ash content
- 7. Coal Rank Lignite ~upto 70 % Carbon Subbituminous ~ around 80% Carbon Bituminous ~86-91% Carbon Anthracite ~ above 92% Carbon
- 8. Coal Rank Ranks of Coal Carbon % Volatile Matter Moisture % Specific Energy Peat 60 >60 75 14.7 Lignite 71 52 30 23 Subbituminous 80 40 5 33.5 Low-rank/volatile bituminous 91 14 1 36.4 Medium-rank/volatile bituminous 90 22 <1 36 High-rank/volatile bituminous 86 31 3 35.6 Semianthracite 92 8 1 36 Anthracite 95 2 2 35.2
- 9. Gas Generation During Coalification Gas Generated Volume in SCF/tonne Methane 2000-5000 Carbon Di-oxide 6000+ Wet Gas 100-1000+ Nitrogen 250-500+
- 10. METHANATION Biogenic methane produced by anaerobic bacteria in the early stage of coalification Thermogenic methane mainly during coalification at temperatures of 120 150属 C
- 11. METHANATION Vegetal Matter Biochemical (by organism at <50属C & at 0.5- 10 m depth) Geochemical (by increased temperature & pressure at >10 depth)
- 12. METHANATION Biochemical Diagenesis (Humification) Pit coal (Ro max 0.2-0.3%) Lignite coal (very less % retained &rest is released to the surrounding in the form of diagenic gas)
- 13. Geochemical Catagenesis (Bituminization,debituminization) Sub-bituminous Bituminous (very small amount of methane is released to the surrouding as the thermoginic gas & most of the gas is retained in the coal bed) Metagenesis (>150属C-200属C Ro max >2-4%) -Semi anthracite -Anthracite