COAL BED METHANE (CBM)

PRESENTED BY: FAHMI RAMADHAN ’10

(sharing class knowledge)

Coal has the ability to store gas in significant amounts, because its surface can adsorb gases. Although the form of coal is solid and it looks like a hard rock, but there are a lot of pores smaller than a micron scale, so that coal is like a sponge.

This condition causes the coal surface becomes so broad so that it can absorb large amounts of gas. If the gas pressure is higher, the ability to adsorb gas coal will also increase.

Gas trapped in coal mainly consist of methane gas, so the gas is generally referred to as Coal Bed Methane or CBM . CBM is classified as an unconventional energy

TOPICS

a)History of cbmb)What is it cbm?c)The characteristic of cbmd)production of cbme)How to produce cbm?f)The use of cbm and its impact to the environment

a)History of cbmAnalyses of drilling records suggest that

coal bed methane was produced in the eastern kentucky coal field from wells drilled in the 1950’s that were mistakenly identified as conventional gas well.

Recently, a gas company working in cooperation with several coal companies produced coal bed methane from wells in eastern companies

b)What is it cbm?• it is a gas that occurs in association with coal. During the

coalification process, large amount of gas are produced, some of this gas escapes into other rocks or into the atmosphere but some still remain in coal.

* Permeability in coal is created by naturally occuring fractures referred as cleats

* Coal bed methane is similar to natural gas, differing only in the way that it is formed and stored in the Earth's crust

* Unlike much natural gas from conventional reservoirs, coal bed methane contains very little heavier hydrocarbons such as propane or butane, and no natural gas condensate. It often contains up to a few percent cabon dioxide.

c)The characteristic of coal bed methane

1.Porosity

The porosity of coal bed reservoirs is usually very small, ranging from 0.1 to 10%.

2. Fracture permeability

the fracture permeability acts as the major channel for the gas to flow

3.Thickness of formation and initial reservoir pressure

The thickness of the formation may not be directly proportional to the volume of gas produced in some areas

4. Other properties

coal density, initial gas phase concentration, critical gas saturation

d) Production of cbmIn the coal layer, there are many fractures

(cleats), which formed during the processwater 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.

cbm can come out (desorption) of the matrix through the cracks, by lowering the water pressure on the target layer

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

e)The use and reserve of CBM in Indonesia

CBM is an alternative energy whis is renewable. It can be used as an energy for every human needs. It can be used as a substitute of gasoline in which gasoline’s production is getting lower in indonesia and the prize is also sky rocketting.

1) Rusia:  450-2.000 TCF2)China: 700-1.270 TCF3)Amerika Serikat:  500-1.500 TCF4)Australia/New Zealand:  500-1.000 TCF5)Kanada:  360-460 TCF6)Indonesia:  400-453 TCF7)Afrika bagian Selatan:  90-220 TCF8)Eropa bagian Barat:  200 TCF9)Ukraina:  170 TCF10)Turki:  50-110 TCF11)India:  70-90 TCF12)Kazakhstan:  40-60 TCF13)Amerika bagian Selatan/Meksiko:  50 TCF14)Polandia:  20-50 TCF

the reserves of cbm in indonesia mainly located in south sumatra approximately 183 TCF, BARITO 101,6 TCF, KUTAI 80,4 TCF,

f) How to produce cbm and its impact to the environment

In the conventional method of CBM production, economical production can only be done on good permeability of coal seams layer.

But with advances in drilling techniques to control direction, the direction of the borehole from the surface can be determined freely, so that the extended drilling in the coal layer can be done

controlling the direction of the drillingDrillinfg technique using a down hole drilling

motor (in this mechanism, only the bit that is attached at the end of the down hole motors which is spinning through the work of a pressurized fluid sent from the surface) and not a rotary drilling machine (in this mechanism, the rotation caused by the rotation of rod). In this technique, a tool called MWD (Measurement While Drilling) mounted on the back of the down hole motor, serves to monitor the direction of the drill holes and make corrections direction while continuing to drill

CBM is extracted from coal beds through the drilling of wells. However, unlike drilling for natural gas, large amounts of water must be pumped from the coal bed area in order to depressurize the bed. Once the water is removed, the methane is able to escape from the coal and flow into the well itself. A typical well can produce CBM for up to 15 years. a much shorter life-span than that of a coal mine. However, unlike a coal mine, the later years generally produces the most methane since the well contains less water allowing the release of more CBM.

ECBM (enhanced coal bed methane recovery)

ECBM (Enhanced Coal Bed Methane Recovery) is a technique to improve CBM which is produced.

In this technique, gas injection is commonly used is N, and CO2. Here, the results obtained are very different depending on which gas injection is used.

Environmental impacts

CBM wells are connected by a network of roads, pipelines, and compressor stations. Over time, wells may be spaced more closely in order to extract the remaining methane. Additionally, the produced water may contain undesirable concentrations of dissolved substances. Water withdrawal may depress aquifers over a large area and affect groundwater flows.

The report noted that the extraction of water from coal beds and its eventual disposal or use can have either positive or negative impacts on soil, ecosystems, and the quality and quantity of surface water and groundwater. At present, no widespread negative effects have been documented. However, because coal bed methane production is a relatively young industry, these environmental impacts are not yet completely documented or understood

Produced water varies greatly in both quality and quantity depending on the geology of the coal basin from which it is extracted, but after any required treatment, the water could be put to beneficial uses. However, produced water is thought to accumulate over millions of years, making it essentially a nonrenewable resource, and therefore managing produced water carries with it the responsibility to take all environmental considerations into account, rather than simply choosing the management option that comes at the least cost

Thank’s for your attention