FORECASTING CBM PRODUCTION IN MUKAH-BALINGIAN COALFIELD, SARAWAK MALAYSIA

Coal-bed methane (CBM) or coal-bed gas is a form of natural gas extracted from
coal beds. The term refers to methane adsorbed into the solid matrix of the coal. In
order to understand the performance of a CBM reservoir, we need to know the
Original Gas in Place, Production Rates and also Recovery Factor. This is mainly on
creating a Microsoft Excel ® 2007 with the help of Visual Basic for Application
(VBA) based CBM forecast tool. Field data from Mukah-Balingian Coalfield
Sarawak is analyzed and forecasted. Original Gas in Place is calculated by
multiplying the mass of the coal with the initial gas content of the coal bed.
Following from the generated Relative Permeability data, production rates for both
water and gas calculated over a specific time range. During the whole production, an
abandonment condition which is mainly the pressure will be set by the engineers.
Using this abandonment pressure, we can calculate the recovery factor. Using
constant values of Langmuir Volume of 714.29 scf/ton, Langmuir Pressure of
1024.5 psia, and reference initial pressure of2000 psia; flowing pressure of 100 psia
which is also the abandonment pressure, various range of skin,permeability, intial
gas content as well as porosity tested to predict the field performance. Using the
range of initial gas content of 86.286 - 173.36 sc£'ton; range of permeability of
l.Ole-6 md to 1010 md; porosity, with a range ofO.OOOl to 0.5%; Skin ranged from
-5 to 4, CBM production is forecasted for the range of 5 years.
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