1. COAL BED METHANE:EXTRACTION TECHNOLOGY
MINE PORTAL TEAM
CALL/WHATSAPP

2. What Is Coal Bed Methane?
Standard natural gas: CH4
methane rich gas originating in coal-seams.
It is held in the cleats with the coal
Substantial water pressure needed to keep methane in the coal: 400 to 1000 ft

3. Reason For Extracting
The occurrence of CBM has been known for many years, but it was initially treated as a potentially explosive hazard during underground mining.
Fans were used to extract the gas into the atmosphere, which not only loses an energy source but adds to the ‘greenhouse effect’ in the atmosphere.

4. Classification Of CBM
In industry CBM is classified in three main categories:
Coal-mine methane (CMM): released from the coal seams during coal mining.
Abandoned mine methane(AMM):- released from closed and sealed mines
Virgin coal bed methane(VCBM): Virgin Coal Bed Methane (VCBM) describes the recovery of methane from seams in which the coal will remain unmined.

5. Coal Bed Methane Potential: India
CBM Blocks of India
State No. of Blocks Area (Sq. Km)
West Bengal
Jharkhand
Madhya Pradesh
Rajasthan
Chhattisgarh
Andhra Pradesh
Maharashtra
Gujarat
Total

7. How Coal Bed Methane Is Removed
CBM is removed by removing water pressure which holds CBM in place. Methane that was held in place by water pressure tends to follow the water as it is pumped to the surface, where it is captured and transported through pipelines

8. CBM Gas/Water Separation in Sohagpur Block CENTRAL INDIA CBM

9. Continued…..
The operator extracts water to reduce the hydrostatic pressure in the formation so that gas flow can commence.
The CBM readily separates as pressure decreases, allowing it to be piped out of the well separately from the water. Water moving from the coal seam to the well bore encourages gas migration toward the well.

10. Method Of Degasification
CBM is recovered with :-
Horizontal wells,
Hydraulically fractured vertical wells, and
Gob wells.
Hydro fractures propagate up to 500 feet in the coal seam
The choice of vertical or horizontal wells is dependent on the geology of the coal seam. In the case of seams at shallow depths, vertical wells have been traditionally used.

12. Vertical Wells Method
Well is drilled through coal seam prior to mining .
hydraulically fractured to remove much of the methane from the seam
The water in the coal seams must be removed to provide better flow of gas.
Recover 50% to 90% of the gas content of the coal.
They can be applied to multiple coal seams simultaneously

13. Vertical Well

14. Gob Wells
Extracts methane from the gob areas of a mine after the mining has caved the overlying strata.
They are normally drilled to a point 10 to 50 feet above the target seam prior to mining.
Operated only after mining fractures the strata around the wellbore
Methane emitted from the fractured strata then flows into the well and up to the surface.
Cross measure bore hole are used for exhausting gas from the gob area.
Recover 30% to 70% of methane

15. Gob Well Method

16. Horizontal Borehole Horizontal holes are drilled into the coal seam.
Horizontal systems can recover much higher volumes of methane from coal seams at extreme depth
Methane are drained from the un mined areas of the coal seam shortly before mining.
Recovery efficiency of this technique is low

17. Horizontal Bore Hole

18. CASE STUDY
Great Eastern Energy Corporation Ltd (GEECL) has begun the production and sale of coal-bed methane (CBM), the first such commercial project in India. GEECL is targeting initial production of 1.5 million standard cubic feet per day .
GEECL had drilled, perforated and fractured 23 wells and installed the pumps. Nine wells are currently in production, delivering 991 thousand cubic feet (MSCFD) per day.

19. CASE STUDY continued…..
GEECL uses a hydraulic fracturing process in which a fracturing fluid is first injected into a targeted coal seam. The fluid causes a pressure build-up that propagates the fracture away from the well. Once the fracture has propagated, the operator injects a gelled fluid carrying a prop pant (usually sand) to prop the fracture open. Fracture propagation and prop pant injection are a continuous process.

21. Hydrologic Impacts Groundwater depletion Water table drawdown
Decreased flow to springs and streams
Groundwater Contamination
- Methane in the groundwater
- Seepage of disposed CBM water
Surface Water
- Water quality: Excess Sodium or Salt
- Wasted water
- Changing channel shape

22. References
Bhat, S. and Agarwal, P.K., 1996, The effect of moisture condensation on The spontaneous combustion of coal:Fuel, v. 75, (13), p
Biswas, S.K. (1995): Prospects of coal bed methane in India:Ind. Jour. Petroleum Geol., v. 4, No. 2, p
GSI, 2004, Inventory of Geological Resource of Indian Coal (As of ): Geological Survey of India.
en.wikipedia.org/wiki/Coalbed_methane retrieved on 08/08/2011.