The widely recognized importance of the re-evaluation of existing hydrocarbon fields has focused the attention of oil companies on the problem of cased hole logging interpretation.

Cased hole logs actually provide a lot of information. However, their response, particularly for the Density log, is heavily affected by the presence of casing and cement. For this reason, cased hole recordings are mainly utilized from a qualitative or semi-quantitative point of view by applying empirical corrections to the measured values.

A new algorithm for the automatic correction of all the environmental effects has been developed for the Density log. It is based on the evaluation of the relative contribution of casing and cement to the bulk density measurement. Thence, also corrosion can be taken into account. Casing collars and other disturbances are corrected through a multiple linear regression technique. Neutron, Sonic and Gamma Ray logs undergo a calibration procedure and their reliability is accurately verified.

A case study relevant to an old Italian gas field is presented.

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