This is a study of Adriatic shaly-sand reservoir using a quantitative approach from data acquired by pulsed neutron tools with an aim of revamping this mature gas field, located in offshore Ravenna in Italy. The well acquired the logs was drilled in 1996 and it produced for 11 years and then was shut because of high water cut production.

The field is characterized by thin multilayered sand-shale alternation, with moderate to high porosity; complex wellbore completion scheme; gas and moderate salty water are the only reservoir fluids. The pulsed neutron tools are exceptionally suitable on these conditions to measure the petrophysical properties that afterward are to be processed by the Techlog software, with a purpose of quantifying the reservoir saturation in the bypassed pay zones and advise for the through-tubing perforation.

The methodology was to use a Techlog software to perform a quantitative interpretations in some well datasets, characterized by dual string completion, acquired using two formation evaluation tools – Reservoir Saturation Tool and Formation Evaluation Tool, from different time-lapse since field production start-up.

The aim was reached thanks to the comparison of open-hole Computerized Petrophysical Interpretation dataset with the cased-hole log measurements, first tool from 2002 and second tool from 2017, and the result was the identification of time-lapse changes in saturation leading to clear quantification of the current saturating fluid within the reservoir layers.

The many pay zones identified were run through-tubing perforation so the production increased from zero up to 120000 standard cubic meters of gas per day.

The pulsed neutron in Sigma mode is extremely suitable for the purpose of investigating the saturating formation fluid on cased-hole conditions.