COAL BED METHANE PROPERTIES MODELING USING IMPROVED SEISMIC RESOLUTION FOR ESTIMATING GAS RESERVES: A CASE STUDY OF EAST KALIMANTAN FIELD, INDONESIA

Abstract

Coal bed methane (CBM) potential resources are distributed in many areas of East
Kalimantan and are estimated to total about 50 trillion cubic feet (TCF). To estimate more accurately the
potential reserves of CBM, sub-surface modeling of CBM properties is required. The objective of this study
is to estimate the gas methane reserves by using deterministic and probabilistic approaches, which are based
on the identified coal seam distribution. This work is carried out by estimating the gas content parameters
(moisture, ash, volatile matter, and fixed carbon), which are derived by empirical approximation from
geological and geophysical information. The property modeling of CBM parameters is then distributed,
based on the three-dimensional (3D) framework of the identified coal seam distribution. In the well log data,
several coal seams can be recognized using the electric log characters, especially the gamma ray, resistivity,
and density logs. Coal seams are indicated by a low-density value and high resistivity. In this field, coal
seams can be identified at depths ranging from 400 to 1100 m. The gas-in-place (GIP) was estimated in
reference to the identified coal seam along the 3D geometrical framework. The results show that based on the
probabilistic approach, the GIP ranges between a minimum of 8.9 billion cubic feet (BCF) and a maximum
of 493.7 BCF, with a mean of 47.7 BCF, while based on the deterministic approach the GIP is 107.7 BCF.