gas hydrate - CCOP

The results of studies made on 11 coal core samples from the two observation wells and 13
coal core samples from the production well indicated that the desorption of gas averaged
about 0.2-0.31 cubic centimeter per gram or 7.2-10.95 cubic foot per ton.
The properties of the gases were determined by collecting them in 10 canisters from both
production and observation wells and analyzing using gas chromatographic techniques. The
composition of the total gas released from the coal is as follows:
Methane gas about 60%
Nitrogen about 28%
Carbon Dioxide about 12%
Gas flow rate
Gas flow rate from the production well was analyzed using a well stimulation technique by
pumping water from the coal beds to allow coalbed gases to flow into the well. The following
procedure was used:
A submersible pump was installed in the production well below the lower coal seam. The
installation depth was 311.0 m including the length of the pump. The lower coal seam is
found from 281.0 - 287.0 m depth. A pumping test was commenced by pumping water out of
the well. Flow rate was measured and at the same time water levels in both production and
observation wells were recorded. The data received were used for preliminary determination
of coal permeability. Water was continuously pumped so as to keep the water level below the
level of the coal seam. Pumping was suspended at predetermined time-intervals while the
water level was always kept below the coal seam. Gas flow is measured by a system of gas
flow meters.
The results of well stimulation reveal that the water flow rate from the coal seam into the well
was approximately 1.0 cubic meter per day or 0.04 cubic meters per hour. This water flow rate
is considered to be very low, yielding a positive effect during the gas production.
The gas flow during the first 10 days was measured at 19 liters. The resulting flow rate is 1.9
liters per day or 0.067 liters per hour which is considered to be very low. The pumping test
data were used to calculate the coal permeability by a hydrogeological technique yielding a
result of 5 x 10 -6 cm per second. The pumping test was continued for 45 days and it was found
that after the first 10 days the gas flow had completely ceased. The reasons may be due to the
low permeability of the coal and clogging by bentonite mud.
Estimation of reserves of coal and coalbed methane
The reserve estimation of coal in the Mae La Mao basin employed the circular method
recommended by USGS (USGS Circular 891). Using the grid reference of the well as the
center, circles with radii of 400, 1,200, and 4,800 m respectively are drawn to delimit the
reserve areas. The coal reserves are then calculated as measured coal, indicated coal, and
inferred coal respectively.
The thickness of coal used in the reserve calculation is derived from an isopach map by
integrating the entire thickness of all coal beds. In the current calculation, the total thickness
of coal beds is the sum of the upper and lower beds.
140 New Energy Resources in the CCOP Region - Gas Hydrates and Coalbed Methane