Preliminary Study on Gas Storage Capacity and Gas-in-Place for CBM Potential in Balingian Coalfield, Sarawak, Malaysia

Abstract - The objective of this project is to predict the Coal Bed
Methane (CBM) potential in Balingian coalfield, Sarawak. The
geological survey shows that this area is about 120 km2. One out
of six blocks in Balingian area is picked as an area of interest for
preliminary assessment. Liang formation (Balingian Coal) is
lignite coal with a mean vitrinite reflectance of 0.32%.The coal
seam thickness is ranging from 0.33ft to 29.69ft. Based on the
proximate analysis data from Geoscience and Mineral
Department of Malaysia, the result show the moisture content is
in between 12.9% to 18.7%. The volatile matter varies at 37.8%
to 43.4%, whereas the fixed carbon ranges from 40.3% to 43.4%.
The coal contains a very low ash content at mean of 2.7% and
low sulphur content of less than 1%. Four core samples which
were plugged from different coals have the range of porosity
varies from 1.58% to 5.12%. Meanwhile, the permeability
attained at minimum of 0.15mD to maximum of 46.15mD. Such a
huge variation in porosity and permeability shows that they were
due to the different number of cleat networks which were
examined using PoroPerm. Gas storage capacity at different
steps of pressure was determined from adsorption isotherm test
which based on modified Boyle’s law. The result from the
adsorption isotherm test showed the maximum adsorbed
methane in the coal is 374.62scf/ton at maximum pressure of
1219.58psia. The linear regression of Langmuir Volume and
Langmuir Volume showed 714.29scf/ton and 1024.5psia
respectively. The value of maximum absorbed methane is used in gas-in-place calculation which yields 15.20Bscf in the area of 6.094km2. The result is then compared with other similar coal rank fields. As a conclusion, Balingian coal field showed a very good prospect to produce the first CBM in Malaysia based on this preliminary study.

Keywords - Langmuir, gas storage capacity, CBM and gas-inplace