It has been well defined about Coal Bed Methane (CBM), I hope that will more helpful for you...

1. Presentation, about Coal Bed Methane (CBM)
Presented by:
 Mr. Haresh (2k14/glg/49)

2. Coal Bed Methane (CBM)

3. Origin
Organic material with temperature and pressure effect.
 Volatile substances such as methane , water result in
contraction.
 Contraction further results in formation of cleats.

4.  What is CBM ?
 It is a natural gas produced from coal seams
 Sweet gas- mostly contains methane
 Other components are ethane, propane , butane

5.  What exactly is Coal Bed Methane?
 The primary energy source of natural gas is a
substance called methane (CH4). Coal bed
methane (CBM) is simply methane found in
coal seams generated during coalification
process .
 Coal serves as both the source as well as the
reservoir rock for CBM and can hold 5 to
6 times the amount of gas stored in a
conventional sand reservoir of comparable
size.

6. CBM =
Unconventional gas
• CBM did not migrate from the source rock
into the reservoir rock.
• Coal is the source rock and the reservoir
rock.
• The methane does not occur as free gas in
the pore space of coal (only 1 – 2 %)
• Coal is adsorbed to the coal matrix
• Coal can store around 6 to 7 times more
methane than the equivalent volume of rock
in a conventional reservoir.
Desorption
from
internal coal
surfaces
Diffusion
through
the matrix
and
micro pores
Fluid flow into
natural
fracture
network

9.  In the coal layer, there are many
fractures (cleats), which formed
during the process
 water and gas flow in the coal layer
through the fracture(cleat).
 The part of the coal which is
surrounded by the cleat is called the
matrix (coal matrix), where most of
the cbm attaches to the pores in
them.

10.  CBM Storage
There face cleats, butt cleats,
natural fractures/bedding
surrounding the coal block
matrix and pores, micro-pores
within the coal black matrix.
• Face cleats
• Cleats form an interconnected
network in the coal, normal to
bedding.
• Butt Cleats
Butt cleats (shorter) terminate at a
face cleat.

11. CBM Storage
(Contd.)
Methane is assumed to be stored
mainly(>95%) in coal matrix pore,
micro pores in absorbed state and
very less amount(<5%) in bedding
planes, natural fractures.

12. CBM Storage
(Contd.)
• Gas held in coals is by
hydrostatic water pressure.
• Pumping water lowers the
hydrostatic pressure and gas
desorbs from the coal in
cleats and fractures to flow to
surface.

13.  Extraction
• Extraction of CBM requires drilling and
pumping the water from the coal seam, which
reduces the pressure and allows CBM to release
from the coal CBM extraction often produces
large amounts of water, Methane and water are
piped from individual wells to a metering
facility, where the amount of production is
recorded. The methane then flows to a
compressor station, where the gas is
compressed and then shipped via pipeline. The
produced water is a by-product of the gas
extraction process, requiring some form of
management (i.e., use or disposal).

16.  Production of CBM
• To obtain CBM, wells production
made ​​by drilling down from the
surface to the coal layer in the soil
layer itself, coal has high pressure
then the effect of the pressure drop
will occur when groundwater is
pumped around the coal layer
(dewatering) to the surface. This will
cause the methane gas released from
the coal layer and then it will flow to
the surface through the wells
production.

17.  How do we estimate the amount of methane gas
which will come from a region underlain by coal?

18. Method.1
Requires estimating methane reserves
by boring to the top of the coal seam,
then extracting a core from the coal.
The amount of methane recovered from
the coal core is used to estimate gas
content per unit volume of coal. If a
number of cores are drilled and methane
gas release is observed, one can
estimate the amount of gas available in
a region.

19. Method.2
Estimation through a series of
calculations based on information
already known about the coal in the
region and the feasibility of CBM
development.

20. Benefits of CBM
• Development of downstream gas based industries.
• Generation of revenue for state as well as central govt.
• Development of new infrastructure in project site/ consumption
centers
• Water produced from CBM wells can be utilized for irrigation or
industrial consumption.