A module of Digital Formation's LESA software log analysis package includes special algorithms for coalbed methane analysis. The basis of the analysis involve calculations from the density log. However, if other porosity logs are available (sonic and neutron), additional calculations are made with respect to coal rank. Also if an SP log is available, estimates can be made of gas deliverability.
The interpreter defines input parameters to check for the presence of coal, together with choices of drainage area and tons of coal per acre-foot. The program foot calculates the following properties:
- Ash content
- Fixed carbon
- Moisture
- Volatile matter
Then gas volumes are calculated using various equations:
- Original Kim
- Modified Kim
- Langmuir
- Mullen
- Mavor, Close, and McBane
- Prensky
Special templates present the data in the same fashion as Schlumberger and Halliburton.
The interpreter can also perform a regular deterministic analysis (porosity, shale volume, water saturation) over the entire interval, and superimpose on the coal output. This will provide information as to the reservoir properties of any interbedded sandstone intervals (hydrocarbon-bearing vs. wet).