Water saturation
(
S
w
) is a vital factor
for the original oil and gas in place (OOIP and OGIP). Numerous available
equations can be used to calculate
S
w
,
but their values have been unreliable and strongly depend on core
analyses, which are costly and time-consuming. Hence, this study implements
artificial intelligence (AI) modules to predict
S
w
from the conventional well logs. Artificial neural networks
(ANNs) and the adaptive neuro-fuzzy inference system (ANFIS) were
applied to estimate
S
w
using gamma-ray
(GR) log, neutron porosity (NPHI) log, and resistivity (
R
t
) log. A data set of 782 points from two wells (Well-1
and Well-2) in tight gas sandstone formation was used to develop and
test the different AI modules. Well-1 was used to construct the AI
models, then the hidden data set from Well-2 was applied to validate
the optimized models. The results showed that the ANN and ANFIS models
were able to accurately estimate
S
w
from
the conventional well logging data. The correlation coefficient (
R
) values between the actual and estimated
S
w
from the ANN model were found to be 0.93 and 0.91 compared
to 0.95 and 0.90 for the ANFIS model during the training and testing
processes. The average absolute percentage error (AAPE) was less than
5% in both models. A new empirical correlation was established using
the biases and weights from the developed ANN model. The correlation
was validated with the unseen data set from Well-2, and the correlation
coefficient between the actual and the estimated
S
w
was 0.91 with an AAPE of 6%. This study provides AI
application with an empirical correlation to estimate the water saturation
from the readily available conventional logging data without the requirement
for experimental analysis or well site interventions.