Abstract

An accurate value of formation water resistivity (Rw) is essential in calculating formation fluid saturation from conventional well logs. It becomes difficult to get accurate fluid saturation where Rw value is not readily available and where the water saturation in the formation is poor due to lack of clean water bearing zones. The difficulty of obtaining clean water-bearing zones is further accentuated by complexity of reservoir lithology. Normally, in identifying reservoirs from conventional logs, natural/spectral gamma ray is taken into consideration. But due to secondary mineralization where radioactive concentration is much pronounced (i.e. weathered basement) delineating reservoir rock becomes a matter of concern. In this scenario statistical method (P