Intelligent prediction of stable isotope geochemistry of coalbed gas for
its origin
Abstract
Stable isotope analysis gives the criteria to define the characteristics
of the coalbed gas. In this paper machine learning approach was applied
for this purpose. There are two fundamental origins of coalbed gas,
i.e., thermogenic and biogenic gas. Stable isotope analysis is the
primary method to evaluate the origin of coalbed gas.Samples were
collected from the previous literatures and artificial neural network
(ANN) was developed for calculating stable isotopes of
CH4, CO2 and H2. First
model was trained with around 300 samples and then cross validated with
40 samples. Hydrocarbon, CO2-CH4 (CDMI),
Dryness index, Depth and vitrinite reflectance (Ro) have
been used as input parameters and stable isotope of three gases were
determined. Feed forward back-propagation was extensively used as the
optimum network for the effective results. Before feeding into the
network, data was scaled down between 0 to 1 using linear normalization.
The learning process used 80% of the data, 10% were used for
validation and 10 % for testing. for all the process was above 0.9 and
overall, it was observed that R2=0.97762. The stable
isotope of coalbed gas was achieved through this method, viz. , and .
Based on the stable isotope of coalbed gas, the coalbed gas was
characterized and different results were obtained. The Bernard and CD
diagrams were also plotted for the coalbed gas characterization. The
validation of predicted values by actual values was also shown in the
paper. The current research has vast application on coalbed methane
fields as well as conventional and other unconventional gas resources.
This is the first kind of research which provides the stable isotopes of
coalbed gas using machine learning. As stable isotope of coalbed is
necessary to recognize the types of coalbed gas. Stable isotope
geochemistry of coalbed gas also gives the primary knowledge to
management to assess the secondary recovery of methane. This study
provides the thorough knowledge on stable isotope geochemistry of
coalbed gas for judging the sweet spot for the secondary recovery of
coalbed methane.