Abstract

Over the past two decades, Pulsed Neutron Logging (PNL) technology has provided an avenue for hydrocarbon estimation in cased-hole environments independent of formation salinity. Despite the environmental challenges faced during PN log interpretation certain key prevalent parameters including calculation of shale volume, effect of porosity, lithology, borehole size with respect to depth of investigation, type of annulus fluid, cement sheath, hydrocarbon density in the formation, completion fluid at the time of logging operation and availability of calibration zone against clean inorganic shale or water bearing zones, involves a significant impact on the C/O and Sigma results for saturation estimation. The job pre-requisites for appropriate well selection, including factors such as porosity, cement quality, and borehole size based on depth of investigation of the tool also contribute to an integral segment for the success of PNL. This paper takes into consideration the sensitivity analysis of critical parameters related to the log data evaluation and interpretation of pulsed neutron logs with special reference to carbonate reservoirs of the Mumbai High Field. The authors analyzed all these critical parameters governing the PN log responses which are crucial for computation of remaining saturation that adds economic value with increase in production of depleted reservoirs in brown oilfields over time.