Introducing a method for calculating water saturation in a carbonate gas reservoir

Cementation factor greatly affects water saturation estimation. Factors such as depositional environment, diagenesis and depositional architecture make the estimation of water saturation a big challenge in carbonate reservoirs. The current study is introduced a method for calculating cementation factor in Archie formula. First, (MRGC) technique was applied on the (NMR) logging parameters along with (NDS) data to obtain the optimum number of clustering. After that, fuzzy logic method was applied on conventional log parameters obtained from the wells without any NMR log data. In the third part of the study, a novel crossplot introduced including compressional to shear-wave velocity ratio (Vp/Vs ratio) and NDS parameters. Finally, available core data was used to obtain a relationship between cementation factor and effective porosity for each region. Proposed method had advantage of obtaining a variable cementation factor instead of a constant one.