Improved flushing agents for extracting coal seam gas. Proposal prepared by Geoff Croker in conjunction with Docklands Science Park.

1. Well Injection
According to the International Energy
Agency’s Greenhouse Gas Program
findings, conventional recovery by water
removal produces about half the
methane adsorbed onto the coal.

2. Tiffany Project
• Amoco Production Co., now part of BP, conducted the Tiffany project in the 1990s on its CBM
properties in southern Colorado. Company engineers reasoned that nitrogen injection would
improve recovery from the coal since nitrogen has twice as great an affinity for San Juan Basin
coals as methane. In addition, the sweep of the nitrogen front through the formation would push
the released methane to the production wells.
According to an Advanced Resources International study of EGR, if the nitrogen flushes the
methane, it can reach a saturation of almost 100% on the coal.
This is not an inexpensive technique. Even though air is mostly nitrogen, a nitrogen generator
must create nitrogen with high enough quality for an effective sweep, and nitrogen produced with
the methane must be separated, treated and reinjected.
Amoco started the project after the group of wells had produced conventionally for 9 years. It
drilled 10 new directional wells in January 1998 and in December of that year converted two
producing wells to injectors. It injected 22 MMcf/d to 28 MMcf/d of nitrogen into the 12 wells.
Before the injection, the project wells produced 5 MMcf/d of gas from 34 wells. The speed of the
nitrogen action was immediately evident as well production peaked at 29 MMcf/d of gas, a five-
fold increase, in March 1999.
Now, the company is studying the potential of adding CO2 injection to the already-generated
nitrogen.

3. Allison Project
• In its Allison project in New Mexico, Burlington Northern, now part of
ConocoPhillips, injected CO2 and shut in five producing wells for 6
months to let the CO2 “soak” and give the CO2 and methane a
chance to change places.
The company reasoned CO2 has four times the affinity for coal that
methane has, and it should displace the methane from the coal.
After 6 months, the company opened the production wells and saw
an immediate increase in water production. The company also
found a 0.6% concentration of CO2 after injection compared with
0.4% before injection.
The company injected 4.7 Bcf of CO2 into the partially dewatered
coals and got a 1.5 Bcf incremental increase in methane production.
About 4.2 Bcf of the CO2 remained adsorbed on the coal.

4. Economics
• Advanced Resources International came up with a calculation for base
methane recovery and recovery with nitrogen and CO2 individually in a
conceptual five-spot recovery pattern.
Base recovery with no enhanced mechanisms was 1.171 Bcf of gas.
Recovery with nitrogen rose to 2.933 Bcf, and recovery with CO2 was in
between at 2.147 Bcf. In other words, incremental recovery with nitrogen
more than doubled recovery from the pattern, and the CO2 injection nearly
doubled the production.
The US Environmental Protection Agency (EPA) offered a look at the
economics of a 100-well CO2 injection project, assuming a wellhead price of
US $2/Mcf for the CBM and assuming the cost of drilling the production
wells and the infrastructure already had been sunk in the conventional
production phase. It estimated an undiscounted cash flow of $1.l6 to
$1.36/Mcf of gas at a 40% recovery. A new project with new production
wells and infrastructure would lower cash flow by $0.13 to $0.20/Mcf,
leaving the operator a profit between $0.96 and $1.23/Mcf, undiscounted.

5. Combining CO2 & Nitrogen
• Given the qualities of both CO2 and nitrogen in improving CSG production
and given the potential of coal to adsorb four times as much CO2 as
methane in a world looking for ways to get rid of greenhouse gases, a
combination of the two technologies was a natural extension.
Advanced Resources International, and later the Alberta Research Council
in Canada, speculated on the value of combining the technologies using flue
gas from coal-fired power plants, which contains both gases.
The CO2 remains adsorbed to the coal, and most of the nitrogen returns to
the surface in the methane stream.
Utility companies also try to build power plants near the power source, in
this case coal. That opens another attractive alternative. An operator could
collect flue gas from a coal-fired power plant, use the gas to enhance
recovery from the coal beds and use the produced methane for cleaner
industrial utility power.

6. Real World Tests
• A one-well test in the south Qinshui Basin in
Shanxi Province in northern China showed the
coal was stable and permeable enough to
adsorb CO2 and increase methane production.
In related activity, the Asia Canada Energy Inc.
subsidiary of Pacific Asia China Energy Inc. and
the Alberta Research Council started a
cooperative research study to evaluate EGR
potential in the company’s coalbed methane
concession in Guizhou Province in China.

7. Why Docklands Science Park?
• Question remaining
A CBM enhanced recovery conference in
Boulder, Colo., revealed that operators had no
problem with the mechanics of injecting CO2,
nitrogen or flue gas into coal seams.
The big question centred on the economics of
gathering, processing and treating the gases to
get them ready for injection.

8. 200t/day PUTAR Unit
Apply heat
here by pulse
combustion
heaters
Separates gases
sequentially by liquefaction
temperatures, enabling
liquid methane to be sent
into the pipeline and sent
down the pipeline. Cooling down to -268°C
Units are modular.